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Home My WebLink About240911 Draft Respone to Comments Letter ENVIRONMENTAL �yii i inn ion� PARTNERS September 11, 2024 Ms.Jean Enright, Planning Director North Andover Planning Board 120 Main Street North Andover, Massachusetts 01845 North Lake Coch*Ichewick Boat Launch North Andover,, Massachusetts Dear Ms. Enright and Planning Board Members, On behalf of the Town of North Andover(the Applicant), Environmental Partners Group, LLC(EP) has prepared this letter in response to the peer review comments received from Horsley Witten Group (HW) on August 26, 2024.A list of attachments to this letter is provided below. List of Attachments: Attachment 1: Peer Review Letter by Horsley Witten Group, dated August 26, 2024 Attachment 2: Permeable Paver Detail Attachment 3: HydroCAD Stage Storage Tables Attachment 4: Revised TSS Worksheets Attachment 5: North Andover Design and Performance Criteria with Attachments Attachment 6: BMP Location Map Horsley Witten Group's comments are listed below in bold followed by EP's responses in italics. Stormwater Management Design Peer Review Standard 1: No new stormwater conveyances (e.g., outfalls) may discharge untreated stormwater directly to or cause erosion in wetlands or waters of the Commonwealth. The Project has been designed to comply with Standard 1. Standard 2: Stormwater management systems shall be designed so that post-development peak discharge rates do not exceed pre-development peak discharge rates. 1. HW recommends that the Applicant provide a plan view detail of the permeable interlocking concrete pavement with paver dimensions, and the placement of the'/4- inch crushed stone in openings for clarity. A plan view detail of the concrete permeable paver is provided in Attachment 2. d 2. HW recommends that the Applicant clarify the stone to be placed beneath the concrete pavers. Specifications for the process gravel backfill and the crushed stone bedding would be beneficial to confirm the permeable interlocking concrete pavement will function as anticipated. HW recommends that the Applicant confirm if an underdrain is applicable and update the details as necessary. Per the manufacturer's recommendations the base below the concrete pavers shall be a 1-inch thick standard bedding of course sand and a minimum 6-inch thick standard base of 3/"crushed run gravel(any road base standard in accordance with ASTM-D2940) compacted to 98916 Standard Proctor Density(SPD). Based on EP-s review of the boring data collected, the soils proved adequate infiltration. Therefore, we do not believe an underdrain is needed. The intent of the crushed stone bedding is to provide infiltration,provide a layer to move water away from the surface, and recharge the groundwater.A revised detail with a plan view of the concrete permeable pavers is provided in the Attacchment 2. 3. HW recommends that the Applicant specify the filter fabric and clarify if the intent is to install the filter fabric under all the pavers to create an impermeable liner. HW notes that the Applicant has not included exfiltration or storage beneath the pavers in the HydroCAD model. The intent of the filterfabric is to provide a permeable membrane between the stone base and subgrade, allowing water to pass while keeping soil fines from migrating through the fabric. EP did not include the exfiltration explicitly in our model. 4. The Applicant has used an exfiltration rate of 0.17 inches per hour(iph)for the Bioretention Areas,which is comparable to a sandy clay loam for hydrologic soil group (HSG) C. Three borings were conducted within the project area which support the exfiltration rate used. HW notes that the test pits are not within the footprints of the bioretention areas. The value appears reasonable. However, prior to construction additional soil testing should be conducted within the footprints to confirm the soil texture as well as the depth to estimated seasonal high ground water(ESHGW). The exfiltration rate used in our model was conservative. Soil boring B1 is located approximately 60 feet from bioretention area No. 2 and soil boring B3 is located approximately 75 feet from bioretention area No. 1. Based on our borings,soils were generally classified as poorly graded sand, silty sand. Rawls rates for this soil is between 0.4 and 0.5 in/hr. EP is confident that the soils used in our model are conservative, and further test pitting and design changes are not necessary. 5. The water table for the three borings was noted to be 6.5 feet below ground surface (bgs). Based on boring B1 the ESHGW is at approximately elevation 110.75. The bottom surface of the bioretention areas is elevation 115.0 and 115.5 with approximately 4.5 feet of planting soil and crushed stone below, to elevation 110.5 and 111.0. HW recommends that the Applicant conduct additional soil testing to document that the ESHGW is lower than elevation 110.5 or raise the bottom of the systems. en vI I'� II II° II m m li The estimated seasonal high ground water(ESHGW) elevation was measured at approximately elevation 110.75 feet at soil boring B 1 and elevation 110.0 feet at soil boring B3. The depth of soil media and washed stone is 2-feet and 2.5 feet below the bottom of the bioretention areas, respectively(elevation 112.5 and 113.0, respectively). The plantings within the bioretention areas shall be shallow rooted plants and grasses to accommodate for the minimum soil media depth of 2-feet. We will incorporate two (2)test pits into the final design that will be completed during construction to verify groundwater elevations. 6. In accordance with §250-22 B. (6)a summary of pre-and post-development peak rates and volumes of stormwater demonstrating no adverse impacts should be provided as part of the narrative. The Applicant has provided the peak flows but has not provided the peak volumes for the 2-year, 10-year, and 100-year 24-hour storm events. HW recommends that the Applicant provide a volume comparison table as required. The peak volumes are provided in the HydroCAD report.A runoff volume comparison table for the 100 year storm event is provided in Attachment 5. Standard 3: The annual recharge from post-development shall approximate annual recharge from pre-development conditions. 1. HW recommends that additional soil testing is conducted to confirm the exfiltration rate and the ESHGW. HW recommends that the Applicant provide the stage storage HydroCAD worksheet for the two bioretention areas to confirm the storage volume listed in the calculations(1,432 cubic feet(cf)for Bioretention Area #1 and 1,239 cf for Bioretention Area #2). EP will add test pits to the final design documents. Test pits will be located within the bioretention area footprints to confirm soil texture and estimated seasonal high ground water (ESHGW) elevation. The test pits will be performed by the construction Contractor. The custom stage storage tables for the bioretention areas are provided in Attachment 3. Standard 4 requires that the stormwater system be designed to remove 80%Total Suspended Solids(TSS)and to treat 1-inch of volume from the impervious area for water quality. 1. The Applicant has provided a TSS worksheet that states the Bioretention Areas have a TSS Removal Rate of 90%. In accordance with the MSH,Volume 1, Chapter 1, page 11 90% credit is allowed when combined with adequate pretreatment. HW recommends that the Applicant clarify what the pretreatment practice is. BMPs were selected so that a total of 80916' TSS removal is provided by one or more BMPs. The treatment trains for the two(2)bioretention areas have been revised and described below. However, EP believes that we are meeting this standard regardless of the additional TSS removal. There is a reduction in imperviousness to the redeveloped project area. Treatment Train 1: This treatment train consists of capturing stormwater runoff from a portion of the Site and a portion of Great Pond Rd to Bioretention Area No. 2. The portion of runoff from the Site is a combination of runoff from grass filled and stone filled permeable III IPA ar II-ieI m a In pavers(5,275-sf), the paved driveway apron (235-sf), and lawn area(1,250-sf). The portion of off-site run-off directed to Bioretention Area No. 2 is from 1,672-sf of the paved roadway along Great Pond Rd. Excess water from Bioretention No. 2 will discharge to Bioretention No. 1 through an overflow structure and conveyance piping. The overall TSS removal for this train is 80%. This treatment train does not provide pre-treatment prior to stormwater conveyance to Bioretention Area No. 2. Treatment Train 2: This treatment train consists of capturing stormwater runoff from a portion of the Site, and a portion of Great Pond Rd to Bioretention Area No. 1. The portion of runoff from the Site is a combination of runoff from stone filled permeable pavers(1,056-sf), the paved driveway apron (248-sf), and lawn area(1,781-sf). The portion of off-site run-off directed to Bioretention Area No. 1 is from 1,808-sf of paved roadway along Great Pond Rd. Overflow from Bioretention No. 1 is conveyed via a riprap-lined Swale. The overall TSS removal for this train is 80916. This treatment train does not provide pre-treatment prior to stormwater conveyance to Bioretention Area No. 2. Treatment Train 3: This treatment train consists of capturing excess water from Bioretention No. 2. Bioretention No. 2 provides pre-treatment to the excess water before discharging to Bioretention No. 2. Overflow from Bioretention No. 1 is conveyed via a riprap-lined swale. The overall TSS removal for this train is 85916. The pretreatment requirement of 44916 TSS removal prior to infiltration is met to the maximum extent practicable.A redevelopment project is required to meet this Standard only to the maximum extent practicable. No new impervious area is being added under proposed conditions. There is an overall reduction in impervious area from 5,253-sf to 483-sf (approximately 91%reduction). Overall, the project will be an improvement to existing conditions. Revised TSS Worksheets are provided in Attachment 4. 2. HW further notes that including 90% pretreatment from Bioretention Area 2 prior to Bioretention Area 1 is not realistic considering the additional surface area captured by Bioretention Area 1 that does not go through Bioretention Area 2 first. The treatment trains for the two (2)bioretention areas have been revised based on HW's comments. Refer to response above. However, EP believes that we are meeting this standard regardless of the additional TSS removal. There is a reduction in imperviousness to the redeveloped project area. Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads (LUHPPL). Agreed, Standard 5 is not applicable to the Project. III-i v P a IIIrt-°e s m c o Itm ry��''�'��µ� c ..III Ir Standard 6 is related to projects with stormwater discharging into a critical area, a Zone II, or an Interim Wellhead Protection Area of a public water supply. 1. It is HW's understanding that MassDEP has stated that porous pavement is not suitable within a Zone I or a Zone A. The practice can be lined with an underdrain. The underdrain must employ a practice to provide for shut down and containment if there is a spill on the surface. HW recommends that the Applicant review the permeable pavement design and confirm it meets MassDEP's requirements. The Massachusetts Stormwater Handbook identifies three major types of permeable paving (i.e. porous pavement):porous asphalt, paving stones, and grass pavers. Porus pavement typically refers to the use of recycled rubber, stone aggregate, and a urethane binding agent. We are not using this type of product in this project. A redevelopment project is required to meet this Standard only to the maximum extent practicable. If the stormwater BMPs do not meet all the requirements set forth on page 6 of the Redevelopment Checklist, the Applicant shall document an analysis of alternative approaches.An alternatives analysis was provided in Appendix C of the NOI application. There are no site-specific factors that indicate a strong likelihood of a significant impact occurring to this area. EP believes that we are meeting this Standard to the maximum extent practicable and implementing the highest practicable level of stormwater management. Overall, the project will be an improvement to existing conditions. Standard 7 is related to projects considered Redevelopment. In general, the project has been designed to comply with Standards 4 and 6 to the maximum extent practicable. Standards 1, 2, 3, 5, 8, 9 and 10 have been met fully. Overall, measures have been proposed to improve existing conditions. 1. HW notes that the North Andover Stormwater Management and Erosion Control Bylaws have specific requirements for redevelopment projects that are more stringent than the MSH. HW recommends that the Applicant clearly demonstrate that it complies with the local regulations. This recommendation does not apply to Standard 7 of the Massachusetts Stormwater Handbook. Project compliance with the performance criteria as identified in Section 250-27 of the North Andover Stormwater Regulations is provided in Attachment 5. Standard 8 requires a plan to control construction related impacts including erosion, sedimentation, or other pollutant sources. 1. HW recommends that the Applicant install silt sacks in all catch basins within 100 feet of the construction entrance. ii1-i v P a iiIrt-e s m c o itm ryi��;�a!��:��C,.III'..liiw IL"`" e A silt sack will be installed at the CB downslope of the project site and incorporated into the final design drawings. 2. HW recommends that the Construction Entrance be a minimum of 30 feet long. The construction entrance shown on Sheet C-2 of the permit drawings is more than 30 feet long. 3. HW recommends that the Applicant confirm that it is necessary to remove all the trees proposed to be cut and list the size and types of trees to be installed. Standard 8 does not apply to this recommendation. The Contractor shall flag trees to be cut and work with representatives of the Conservation Commission for review and approval prior to tree clearing. The types of trees to be installed are listed in the general planting plan notes on Sheet CD-2 of the permit drawings. Standard 9 requires a Long-Term Operation and Maintenance(O & M) Plan to be provided. 1. HW recommends that the Applicant include the routine inspections and maintenance of the permeable pavers as well as the riprap aprons and lined swale. Routine inspections of BMPs will be performed in accordance with the Town's Stormwater Management Plan and the MassDEP Stormwater Handbook. Figure 1,provided in Attachment 6, identifies the location of each BMP to be inspected and maintained. 2. HW further recommends that the Applicant include a simple maintenance schedule,with a simple sketch to illustrate where the practices are located on the site, as well as a budget, so that the property owner understands what to expect. The Town of North Andover will be responsible for the operation and maintenance of the BMPs post-construction.A BMP location map is provided in Attachment 6. Standard 10 requires an Illicit Discharge Compliance Statement be provided. 1. The Planning Board may choose to require receipt of a statement signed by the Property Owner prior to land disturbance. A receipt of a statement signed by the Property Owner prior to land disturbance can be provided to the Planning Board upon request. III IPA ar II-ieI m a In Sincerely, Environmental Partners Group, LU[ DRAFT Jamie LVeiUette, BT Senior Project Engineer 0: 617.657.0960 E:jlv@envpartners.com e�v�a Irt 1-i e s.c omm A..........Iuuuuu ..........11 C��Peer" Review � etteir, I.............1�()In I Ely Wi,�t��t e i�,.I G I M Ll dated August 26, 2,024 Horsley 'Wi ften Group 112 Water Street 611,Floor Boston,MBA 02109 August 26, 2024 Ms. Jean Enright, Planning Director North Andover Planning Board 120 Main Street North Andover, Massachusetts 01845 Ref: Initial Stormwater Peer Review North Lake Cochichewick Boat Launch North Andover, Massachusetts Dear Ms. Enright and Board Members: The Horsley Witten Group, Inc. (HW) is pleased to provide the North Andover Planning Board with this letter report summarizing our initial review of the Stormwater Report and plan set for the proposed redevelopment of the North Lake Cochichewick Boat Launch (Boat Launch), located across the street from 1939 Great Pond Road, North Andover, MA. The plans and Stormwater Report were prepared by Environmental Partners on behalf of the Town of North Andover (Applicant). The redevelopment project proposes to reconstruct the existing boat launch, add a new block retaining wall, install a permeable access drive and parking lot, and install two bioretention areas to manage stormwater. The proposed redevelopment includes reducing the total impervious area from 5,253 square feet (sf) to 483 sf, which includes eliminating the 5,074 sf of existing gravel parking areas considered impermeable and installing 9,991 sf of permeable pavers with crushed stone. The entire site is within the 150-foot Watershed Protection District Non-Disturbance Zone of Lake Cochichewick, with proposed work within Bordering Vegetated Wetlands (BVW), inland Bank, Land Under Waterbodies and Waterways (LUWW), Bordering Land Subject to Flooding (BLSF), and the 25-foot, 50-foot and 100-foot Buffer Zones to the BVW. The project is under the jurisdiction of the North Andover Conservation Commission. The boat launch ramp is located within the 100-year floodplain, identified as Zone A on the most recent Flood Insurance Rate Map (FIRM). The Applicant has noted the Top of Bank JOB) at approximate elevation 113 and the Observed High Water (OHW) at approximate elevation 114. By modifying the grades along the bank and reducing the slope of the new ramp, the proposed project increases the flood storage volume by 100 cubic feet (cf) below elevation 114. The following documents and plans were received by HW: • Application for Special Permit—Watershed Permit Application, Town of North Andover, MA (13 pages); • Supplemental Information — Notice of Intent (DEP NOI #242-1900), North Lake Cochichewick Boat Launch, Town of North Andover, MA, prepared by Environmental Partners, dated August 13, 2024 (21 pages); • Stormwater Report, North Lake Cochichewick Boat Launch, Town of North Andover, MA, prepared by Environmental Partners, dated July 30, 2024 (149 pages); and Town of North Andover August 26, 2024 Page 2of6 • Plan set for North Lake Cochichewick Boat Launch, Town of North Andover, MA, prepared by Environmental Partners, dated July 2024, including: o Cover Sheet o General Notes and Legend G-1 o Existing Conditions C-1 o Erosion Control and Dewatering Plan C-2 o Demolition Plan C-3 o Grading and Drainage Plan C-4 o Site Plan C-5 o Site Restoration Plan C-6 o Civil Details CD-1 — CD-6 Stormwater Management Design Peer Review HW offers the following comments concerning the stormwater management design as per the Massachusetts Stormwater Handbook (MSH) dated February 2008, and the North Andover Chapter 165 Stormwater Management and Erosion Control Bylaw (Bylaw), and the Chapter 250 Stormwater Management and Erosion Control regulations (Stormwater Regulations) adopted June 21, 2022. In accordance with Article 195-4.19.0 (4)) "All construction in the Watershed Protection District shall comply with best management practices for erosion, siltation, and stormwater control in order to preserve the purity of the groundwater and the lake; to maintain the groundwater table; and to maintain filtration and purification functions of the land." The stormwater best management practices have been reviewed in accordance with the most recent version of the Massachusetts Stormwater Standards as well as the North Andover Stormwater Management and Erosion Control Bylaws. We have used the Massachusetts Stormwater Standards as the basis for organizing our comments. However, in instances where the additional criteria established in §250-22 of the North Andover Code requires further recommendations; we have referenced these as well. 1. Standard 1: No new stormwater conveyances (e.g., outfalls) may discharge untreated stormwater directly to or cause erosion in wetlands or waters of the Commonwealth. a. The Applicant has analyzed the pre- and post-development stormwater runoff at one Design Point 1 (DP1), Lake Cochichewick. i) Under existing conditions, there are no stormwater practices to manage the runoff. The project area has been divided into 2 subcatchment areas. (1) Subcatchment 1 S flows towards the southwest edge of the project area into the lake via sheet flow. (2) Subcatchment 2S flows towards the southeast edge of the project area into the lake via sheet flow. ii) Under proposed conditions the Applicant has subdivided the project area into four subcatchment areas. (1) Subcatchment 1 S flows towards the southwest edge of the project area into the lake via sheet flow. Permeable pavers have been proposed to allow some of the runoff to infiltrate into the ground before discharging into the Lake. I i . . WI � " �ll�� I I� ' ° �� I i .� �I� ��I ii � �� „.„��I�� i�� ii l�� III ��i � � �gal I � Town of North Andover August 26, 2024 Page 3of6 (2) Subcatchment 2S flows towards the southeast edge of the project area into the lake via sheet flow. Permeable pavers have been proposed to allow some of the runoff to infiltrate into the ground before discharging into the Lake. (3) Subcatchment 3S, includes a large portion of the permeable pavers as well as a section of Great Road that flows onto the site. The runoff is directed into a (Bioretention Area 2). Bioretention Area 2 is piped into Bioretention Area 1. (4) Subcatchment 4S, includes a large portion of the permeable pavers, as well as a section of Great Road that flows onto the site. The runoff is directed into a bioretention area (Bioretention Area 1). Bioretention Area 1 outlets via a riprap channel towards the Lake. iii) The Applicant has provided the velocity of the riprap channel documenting that the proposed discharge should not cause erosion into the BVW or the Lake. 2. Standard 2: Stormwater management systems shall be designed so that post-development peak discharge rates do not exceed pre-development peak discharge rates. a. HW has reviewed the Pre-Development and Post-Development Drainage Plans and the HydroCAD model. The subcatchment areas, surface materials, curve numbers (CN), times of concentrations, depths of precipitations, and flow patterns appear reasonable. A CN of 80 was used for the permeable interlocking concrete pavement based on the Manufacturer recommended CN value. HW recommends that the Applicant provide a plan view detail of the permeable interlocking concrete pavement with paver dimensions, and the placement of the 1/4-inch crushed stone in openings for clarity. b. HW recommends that the Applicant clarify the stone to be placed beneath the concrete pavers. Specifications for the process gravel backfill and the crushed stone bedding would be beneficial to confirm the permeable interlocking concrete pavement will function as anticipated. HW recommends that the Applicant confirm if an underdrain is applicable and update the details as necessary. c. HW recommends that the Applicant specify the filter fabric and clarify if the intent is to install the filter fabric under all the pavers to create an impermeable liner. HW notes that the Applicant has not included exfiltration or storage beneath the pavers in the HydroCAD model. d. The Applicant has used an exfiltration rate of 0.17 inches per hour (iph) for the Bioretention Areas, which is comparable to a sandy clay loam for hydrologic soil group (HSG) C. Three borings were conducted within the project area which support the exfiltration rate used. HW notes that the test pits are not within the footprints of the bioretention areas. The value appears reasonable. However, prior to construction additional soil testing should be conducted within the footprints to confirm the soil texture as well as the depth to estimated seasonal high ground water (ESHGW). e. The water table for the three borings was noted to be 6.5 feet below ground surface (bgs). Based on boring B1 the ESHGW is at approximately elevation 110.75. The bottom surface of the bioretention areas is elevation 115.0 and 115.5 with approximately 4.5 feet of planting soil and crushed stone below, to elevation 110.5 and 111.0. HW recommends that the Applicant conduct additional soil testing to document that the ESHGW is lower than elevation 110.5 or raise the bottom of the systems. Iq "� u I u I �I^.� � I° �' I W ' W gal"I�. I I IW I � I I �� I I �,I�� I r„.��.��,. ��w wll�� uill�� i „.^„..� ��..,� I I i°��..� ��o"wll�� I ��„..��I��,� ' I o V �,I �� .��`��:'.�. I"��:�� .�� .� �..�� I° � � II � � p i � �� 'iii ip I ��°�.� III . � iii ��.�. �I �� I � � � w�� III�� II I�� I� iii ��. � .IIII III��II��IIL � �III �°��iii ��IIII � �� II � �� IIL �III � �iii �� .I� .� � � � � � � � � I III Town of North Andover August 26, 2024 Page 4 of 6 f. In accordance with §250-22 B. (6) a summary of pre- and post-development peak rates and volumes of stormwater demonstrating no adverse impacts should be provided as part of the narrative. The Applicant has provided the peak flows but has not provided the peak volumes for the 2-year, 10-year, and 100-year 24-hour storm events. HW recommends that the Applicant provide a volume comparison table as required. 3. Standard 3 requires that the annual recharge from post-development shall approximate annual recharge from pre-development conditions. a. The Applicant has reduced the total impervious surface. The annual recharge from post- development is greater than the pre-development conditions. The Applicant has further provided recharge calculations. However, as noted above HW recommends that additional soil testing is conducted to confirm the exfiltration rate and the ESHGW. HW recommends that the Applicant provide the stage storage HydroCAD worksheet for the two bioretention areas to confirm the storage volume listed in the calculations (1,432 cubic feet (cf) for Bioretention Area #1 and 1,239 cf for Bioretention Area #2). b. Per §250-23 C. (1)(b) redevelopments sites are required to retain the volume of runoff equivalent to 0.8 inch multiplied by the total post-construction impervious surface or meet a combination of retention and treatment that achieves the above standards listed under§250-23 C. (1). HW notes that the HydroCAD model indicates that the Applicant is retaining the 2-year storm event within the bioretention areas. HW further notes that the proposed Bioretention Areas are managing the runoff from a portion of Great Pond Road. HW has no further comment. 4. Standard 4 requires that the stormwater system be designed to remove 80% Total Suspended Solids (TSS) and to treat 1-inch of volume from the impervious area for water quality. a. The Applicant has provided a TSS worksheet that states the Bioretention Areas have a TSS Removal Rate of 90%. In accordance with the MSH, Volume 1, Chapter 1, page 11 90% credit is allowed when combined with adequate pretreatment. HW recommends that the Applicant clarify what the pretreatment practice is. b. HW further notes that including 90% pretreatment from Bioretention Area 2 prior to Bioretention Area 1 is not realistic considering the additional surface area captured by Bioretention Area 1 that does not go through Bioretention Area 2 first. 5. Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads (LUHPPL). a. The proposed use is not considered a LUHPPL, therefore Standard 5 is not applicable. No further action requested. 6. Standard 6 is related to projects with stormwater discharging into a critical area, a Zone 11, or an Interim Wellhead Protection Area of a public water supply. a. The proposed development is discharging into an Outstanding Water Resource, listed as Zone A and Zone B public surface water supply. HW notes that in accordance with the MSH Volume 1, Chapter 1, page 18, "Unless essential to operation of a public water system, stormwater BMPS are prohibited within the Zone A."HW understands that the proposed redevelopment is a boat launch for the Town of North Andover and is an Iq "� u I u I �I^.� � I° ' I W ' W gal"I�. I I IW I � I I �� I I �,I�� I r„.��.��,. ��w wll�� uill�� i „.^„..� ��..,� I I i°��..� ��o"wll�� I ��„..��I��,� ' I o V ,I �� .��`��:'.�. I"��:�� .�� .� �..�� III . � iii ��.�. �I �� I � � � w�� III�� II I�� I� iii ��. � .IIII III��II��IIL � �III �°��iii� �� IIII � �� II � �� IIL �III � �iii �� .I� .� � � � � � � � � I III Town of North Andover August 26, 2024 Page 5 of 6 improvement over the existing condition. HW further notes that exfiltrating Bioretention Areas are considered an accepted infiltration practice for stormwater discharges to outstanding resource waters. It is HW's understanding that MassDEP has stated that porous pavement is not suitable within a Zone I or a Zone A. The practice can be lined with an underdrain. The underdrain must employ a practice to provide for shut down and containment if there is a spill on the surface. HW recommends that the Applicant review the permeable pavement design and confirm it meets MassDEP's requirements. 7. Standard 7 is related to projects considered Redevelopment. a. The Boat Launch project is considered a redevelopment because it has reduced the total impervious area. Per the MSH, a redevelopment project is required to meet the following Stormwater Management Standards only to the maximum extent practicable: Standard 2, Standard 3, and the pretreatment and structural best management practice requirements of Standards 4, 5, and 6. Existing stormwater discharges shall comply with Standard 1 only to the maximum extent practicable. A redevelopment project shall also comply with all other requirements of the Stormwater Management Standards and improve existing conditions. HW concurs that the Applicant will improve existing conditions. b. HW notes that the North Andover Stormwater Management and Erosion Control Bylaws have specific requirements for redevelopment projects that are more stringent than the MSH. HW recommends that the Applicant clearly demonstrate that it complies with the local regulations. 8. Standard 8 requires a plan to control construction related impacts including erosion, sedimentation, or other pollutant sources. a. The proposed project will be disturbing less than one acre of land. Therefore, a Stormwater Pollution Prevention Plan (SWPPP) is not required by EPA. b. The Applicant has provided a detail for Sedimentation Control at Catch Basins Silt Sacks. However, the location for the silt sacks is not obvious on the Erosion Control and Dewatering Plan. HW recommends that the Applicant install silt sacks in all catch basins within 100 feet of the construction entrance. c. The Applicant has provided an Erosion Control and Dewatering Plan, that includes a 12- inch filter sock and silt fence within the project area. The Applicant has also proposed a turbidity curtain and cofferdam to be located within the Lake along the Limit of Work. HW recommends that the Construction Entrance be a minimum of 30 feet long. d. There appear to be 16 trees proposed to be removed and 15 native trees to be installed. HW recommends that the Applicant confirm that it is necessary to remove all the trees proposed to be cut and list the size and types of trees to be installed. 9. Standard 9 requires a Long-Term Operation and Maintenance (O & M) Plan to be provided. a. The Applicant included an O&M Plan in Attachment 8 of the Stormwater Report. The O&M Plan is for the Bioretention Areas only. HW recommends that the Applicant include the routine inspections and maintenance of the permeable pavers as well as the riprap aprons and lined swale. I i . . "ll�� I i .� �I� ��I ii � �� „.„��I�� i�� ii l�� III ��i � � �gal I ��I Town of North Andover August 26, 2024 Page 6of6 b. HW further recommends that the Applicant include a simple maintenance schedule, with a simple sketch to illustrate where the practices are located on the site, as well as a budget, so that the property owner understands what to expect. 10. Standard 10 requires an Illicit Discharge Compliance Statement be provided. a. The Applicant has provided an Illicit Discharge Compliance Statement signed by the engineer. The Planning Board may choose to require receipt of a statement signed by the Property Owner prior to land disturbance. Conclusions HW recommends that the Planning Board require that the Applicant provide a written response to address these comments as part of the Board's review process. The Applicant is advised that provision of these comments does not relieve him/her of the responsibility to comply with all Town of North Andover Codes and By-Laws, Commonwealth of Massachusetts laws, and federal regulations as applicable to this project. Please contact Janet Bernardo at 508-833-6600 or at jbernardo@horsleywitten.com if you have any questions regarding these comments. Sincerely, HORSLEY WITTEN GROUP, INC. , nF , .µ, �R A Janet Carter Bernardo, P.E. Principal I i . . �I I iiW�� II II � ��I � I . I I I I I� IIL .� .� !I(��I ii � �t � � ��I� � II q � l�� ..........Iuuuuu ..........F 2 a a d. O � z e — lank m, J 0 ui ui O ui o U _ tr) a - z ui Q LLI 0 - U - w N !FrIy , 4 - > r. �_.,. - $ _ >> - 4 - - .0 _ - - :_-._ _ m _ VA - — to At a s. _ h • -- - a- OR s -E . a e uu T11 im, a _ FM _ �. a -- 00 �s - 0oLL O �: - -. 3 y _ _IN mill, \. iiq- 3, _v - - a Z W -` �• H _- - � —_ ,�:� �� - y _ _. IIIII IIII' IIIII'' °°°IIIII°°°"°°'IIIIIUNILOCK IIIIIIIIIIIIIII°"' APPLICATIONS Lti Note: Not all sizes are suitable for every application. Contact Unilock Representative for assistance. �. Driveway Patio&Walkway 1 h" 464 Permeable SustainableDesign,Stormwaterretention, LowlmpactDesign,RainwaterHarvesting, IncreasedLotRatio COLORS NATURAL FINISH:CLASSIC STANDARD 15 " " / " MV�IIII umi 0i��wm IIIII°u��„0IIII ��1��8 0 0 IIII"'IIIII IIII...........OQ I(. IIIII U IIII' IIIII'' °°°IIIII°°°"°°'IIIII IIIIIIIIIIIIIII°"' �.t JOINT SPACING=2MM VOID RATIO=40%% LAYING PATTERNS 9 tr� '"ry✓'� r � f" LP TURFSTONE A PDF IIII IIIII i��wm IIIII°�� IIII 111,111,Vi IIII"'IIIII IIII........... IIIII° IIIII IIII' IIIII'' °°°IIIII°°°"°°'IIIII IIIIIIIIIIIIIII°"' TYPICAL CROSS SECTION Lti Note: Base,screed bed, infill aggregates and or reinforcements may vary based on project requirements or as specified by engineer. Unilock,Pavers Standard Joint Viand r Polymeric San 1/4"Clear,Chip AST N ,.9) Extend Base BeyondEdge; ttin CI (Same Base TN ickn s) Plastic,Metal N or,Concrete/ Mortar Edge,"Restraint yr, II ops"4u l Galvanized sik M See CIS w, .. Cn Grade Bas,e(Frei Dra,�,, ln mmmmmmm ri° d Geogrid r Got�, tiN t1 II II I IN IN7' " Residential Use Minimum Base Thickness Walkway 6"'(1 50nnm)- 8,1""(200m m) Driveway_ . . _ ","'00 w"-1 2"'� , mm e m Other Contact ni[ ��' 0 IIII"'IIIII IIII........... C IIIII° ulll 11, IIIII IIII' IIIII''S,°°°IIIII°°°°°'IIIII IIIIIIIIIIIIIII°"' PACKAGING Lti 4. STANDARD ITT I ( ) 80 LAYERS PER BUNDLE 8 SQ FT PER BUNDLE 60 SQ T PER LAYER 7.50 SQ T PER UNIT 2.50 UNITS PER BUNDLE 24 UNITS PER LAYER 3 LBS PER BUNDLE 2,997 LBS PER LAYER 374.63 LBS PER UNIT 124.88 o��w IIII IIIII IIII........... cam IIII "'�� IIII IIIII IIII...........0�i��wm IIIII IIIII IIII' IIIII'' °°°IIIII°°°"°°'IIIII IIIIIIIIIIIIIII°"' INSTALLATION NOTES Lti TurfstoneTM Turfstone has long been a favorite of landscape architects and engineers for areas requiring a supported turf. Its filigree design makes it an attractive and permanent solution for emergency access areas, embankments,spillways,and environmentally sensitive parking areas.Voids may be filled with grass or colored aggregates. Recommended Base Stabilization—one layer of DriveGridTM stabilization grid between subgrade and base material. Recommended depth 8"to 10"below pavers for maximum stability and performance. Use under Standard Base only. Standard Base—Min. 6"—8"of 1/4"Crusher Run gravel(any road base standard in accordance with ASTM-D2940)compacted to 98% Standard Proctor Density(SPD). Standard Bedding Course—1"thick of course sand—in accordance with ASTM-D2940)screeded over base. Jointing Material and Joint Stabilization Fill all holes with topsoil to promote grass growth in openings. Handling—This product is heavy and a two-man clamp is recommended for placement. Edge Restraint-A concrete curb or a"sub-surface concrete wedge"can also be installed to retain the edge. Paver Compaction-For the final compaction,a"rubber roller compactor"will give you the best results without breaking the block. Cleaners—Not applicable Sealers-Not applicable Recommendation: Sealers—After the soil is placed in the openings, it is recommended to seed the area or fill with sod plugs. In order for the grass to establish, provisions must be made for watering. In dry areas,consider irrigation over this area to prevent turf burnout. The Americans with Disabilities Act Accessibility Guidelines(ADAAG)provides measurable criteria to determine compliance, not individual product evaluation. Gaps,joints or openings, greater than '/2"horizontal and 1/4"vertical should be avoided as they can disrupt wheelchair maneuvering(United States Access Board—Guidelines and Standards). Contact Unilock Representative for actual color samples and availability. Unilock reserves the right to change product information without notice. PDF Generated September 8,2024, 11:14 am !JN1L0C1<` uu �� i��wm IIIII°u��„�� 8 0 0V�IIII ...........MIIII ��1�� IIII"'IIIII IIII �IIIII°. IIII IIIII IIII........... ..........I.......... 13.......... Stage Star"age mnlnnnna[-.)1�e s Proposed-N. Andover Boat Launch Type // 24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 9/9/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Stage-Area-Storage for Pond 2P: Bio. Ret. Area #1 Elevation Surface Storage Elevation Surface Storage (feet) (sq-ft) (cubic-feet) (feet) (sq-ft) (cubic-feet) 115.00 0 0 116.04 802 473 115.02 1 0 116.06 810 489 115.04 4 0 116.08 818 506 115.06 8 0 116.10 826 522 115.08 15 0 116.12 834 539 115.10 24 1 116.14 842 555 115.12 34 1 116.16 850 572 115.14 46 2 116.18 858 589 115.16 60 3 116.20 866 607 115.18 76 5 116.22 874 624 115.20 94 6 116.24 882 642 115.22 114 8 116.26 890 659 115.24 136 11 116.28 898 677 115.26 160 14 116.30 907 695 115.28 185 17 116.32 915 713 115.30 212 21 116.34 923 732 115.32 242 26 116.36 932 750 115.34 273 31 116.38 940 769 115.36 306 37 116.40 948 788 115.38 341 43 116.42 957 807 115.40 378 50 116.44 965 826 115.42 416 58 116.46 974 846 115.44 457 67 116.48 982 865 115.46 499 77 116.50 991 885 115.48 544 87 116.52 999 905 115.50 590 98 116.54 11007 925 115.52 597 110 116.56 11015 945 115.54 605 122 116.58 11023 965 115.56 612 134 116.60 11031 986 115.58 620 147 116.62 11040 1,007 115.60 627 159 116.64 1,048 1,028 115.62 635 172 116.66 11056 11049 115.64 642 185 116.68 1,064 13070 115.66 650 197 116.70 1,073 1,091 115.68 658 211 116.72 1,081 M 13 115.70 665 224 116.74 1,089 M 34 115.72 673 237 116.76 1,098 M 56 115.74 681 251 116.78 13106 M 78 115.76 689 264 116.80 13115 1,201 115.78 697 278 116.82 13123 1,223 115.80 705 292 116.84 13132 1,246 115.82 713 306 116.86 15140 1,268 115.84 721 321 116.88 M 49 13291 115.86 729 335 116.90 M 57 1,314 115.88 737 350 116.92 M 66 1,337 115.90 745 365 116.94 M 75 1,361 115.92 754 380 116.96 M 83 1,384 115.94 762 395 116.98 M 92 1,408 115.96 770 410 117.00 11201 11432 115.98 779 426 116.00 787 441 116.02 795 457 Proposed-N. Andover Boat Launch Type // 24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 9/9/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Stage-Area-Storage for Pond 1 P: Bio. Ret. Area #2 Elevation Surface Storage Elevation Surface Storage (feet) (sq-ft) (cubic-feet) (feet) (sq-ft) (cubic-feet) 115.50 419 0 116.54 986 773 115.52 431 9 116.56 994 793 115.54 444 17 116.58 1,002 813 115.56 457 26 116.60 1,010 833 115.58 470 36 116.62 1,018 853 115.60 483 45 116.64 1,026 873 115.62 496 55 116.66 1,034 894 115.64 510 65 116.68 13042 915 115.66 523 75 116.70 13050 936 115.68 537 86 116.72 13058 957 115.70 551 97 116.74 19066 978 115.72 566 108 116.76 1,075 999 115.74 580 119 116.78 1,083 1,021 115.76 595 131 116.80 1,091 1,043 115.78 609 143 116.82 1,100 1,065 115.80 624 155 116.84 M 08 1,087 115.82 640 168 116.86 M 16 M 09 115.84 655 181 116.88 M 25 M 31 115.86 670 194 116.90 M 33 M 54 115.88 686 208 116.92 M42 M 77 115.90 702 222 116.94 M 50 1,200 115.92 718 236 116.96 M 59 1,223 115.94 734 250 116.98 M 67 13246 115.96 751 265 117.00 11176 1,269 115.98 767 281 116.00 784 296 116.02 791 312 116.04 798 328 116.06 805 344 116.08 812 360 116.10 820 376 116.12 827 393 116.14 834 409 116.16 841 426 116.18 849 443 116.20 856 460 116.22 863 477 116.24 871 495 116.26 878 512 116.28 886 530 116.30 893 547 116.32 901 565 116.34 908 583 116.36 916 602 116.38 924 620 116.40 931 639 116.42 939 657 116.44 947 676 116.46 954 695 116.48 962 714 116.50 970 734 116.52 978 753 A..........Iuuuuu ..........14 l,,,,R,,ev'iSed 11 SS Warksl-,)ee-ts INSTRUCTIONS: Non-automated:Mar.4,2008 1. Sheet is nonautomated. Print sheet and complete using hand calculations. Column A and B: See MassDEP Structural BMP Table 2.The calculations must be completed using the Column Headings specified in Chart and Not the Excel Column Headings 3.To complete Chart Column D, multiple Column B value within Row x Column C value within Row 4.To complete Chart Column E value, subtract Column D value within Row from Column C within Row 5.Total TSS Removal=Sum All Values in Column D Location: Treatment Train 1 A B C D E TSS Removal Starting TSS Amount Remaining BMP' Rate' Load* Removed (B*C) Load (C-D Bioretention Area No. 2 � 0.80 0.80 0.20 s �.00 L OO E 0 co �+ W Separate Form Needs to be Completed for Each V Total TSS Removal = 80% Outlet or BMP Train Project: N.Lake Cochichewick Boat Launch Prepared By: Environmental Partners *Equals remaining load from previous BMP (E) Date: 9/9/2024 which enters the BMP Non-automated TSS Calculation Sheet must be used if Proprietary BMP Proposed 1. From MassDEP Stormwater Handbook Vol. 1 Mass. Dept.of Environmental Protection INSTRUCTIONS: Non-automated:Mar.4,2008 1. Sheet is nonautomated. Print sheet and complete using hand calculations. Column A and B: See MassDEP Structural BMP Table 2.The calculations must be completed using the Column Headings specified in Chart and Not the Excel Column Headings 3.To complete Chart Column D, multiple Column B value within Row x Column C value within Row 4.To complete Chart Column E value, subtract Column D value within Row from Column C within Row 5.Total TSS Removal=Sum All Values in Column D Location: Treatment Train 2 A B C D E TSS Removal Starting TSS Amount Remaining BMP' Rate' Load* Removed (B*C) Load (C-D Bi r ni nAr N . 2� o ete t o Area o 0.80 0,80 0.20 s �.00 L OO E 0 co �+ W Separate Form Needs to V so io 0 _ be Completed for Each Total TSS Removal — Outlet or BMP Train Project: N.Lake Cochichewick Boat Launch Prepared By: Environmental Partners *Equals remaining load from previous BMP (E) Date: 9/9/2024 which enters the BMP Non-automated TSS Calculation Sheet must be used if Proprietary BMP Proposed 1. From MassDEP Stormwater Handbook Vol. 1 Mass. Dept.of Environmental Protection INSTRUCTIONS: Non-automated:Mar.4,2008 1. Sheet is nonautomated. Print sheet and complete using hand calculations. Column A and B: See MassDEP Structural BMP Table 2.The calculations must be completed using the Column Headings specified in Chart and Not the Excel Column Headings 3.To complete Chart Column D, multiple Column B value within Row x Column C value within Row 4.To complete Chart Column E value, subtract Column D value within Row from Column C within Row 5.Total TSS Removal=Sum All Values in Column D Location: Treatment Train 3 A B C D E TSS Removal Starting TSS Amount Remaining BMP' Rate' Load* Removed (B*C) Load (C-D Bioretention Area No. 2 0.25 1.00 0.25 0.75 s > L Bioretention Area No. 1 0.80 0.75 0.15 O 0 0.60 E 0 co W H � Separate Form Needs to be Completed for Each t� c� V Total TSS Removal = 0.85 Outlet or BMP Train Project: N.Lake Cochichewick Boat Launch Prepared By: Environmental Partners *Equals remaining load from previous BMP (E) Date: 9/9/2024 which enters the BMP Non-automated TSS Calculation Sheet must be used if Proprietary BMP Proposed 1. From MassDEP Stormwater Handbook Vol. 1 Mass. Dept.of Environmental Protection A..........Iuuuuu FACuuumuuuM ��q R Nar-tl[i AridovII Desigri and 1�1&r-forrnarice Cr"'i�teir,'i'�a w"th Attachr"nents I uumr, �� o �� m Ap �p �� um�nn mug � i �m� m uu� C ��'��. ,ATMion Ii �� m� IIIII �mm� u o �hi,,,,,,�� t �� The following describes the performance criteria as identified in Section 250-27 of the North Andover Stormwater Regulations. III ow kir„ ,: ct Design IIL.......I l;; ) LID features were considered as part of the development of the project.The proposed stormwater management system consists of two (2) bioretention areas and overflow via country drainage. Additional LID measures include reducing impervious area through the use of permeable paver driveways and parking areas. a a ,� m III,,,,,,,,,�III Ir- �„� �,,,�lii c�, It III..........III Ir,a lii c „�,,lil lilt lii°ii a Rainfall data was entered into the model for the 2-year, 10-year, 25-year, and 100-year 24-hour rainfall events as shown in Table 1.An SCS Type III rainfall distribution was selected to develop 24- hour rainfall distribution curves.Additionally,the one-inch water quality storm was analyzed for those areas that are defined as"critical areas." Table 1 - Rainfall eats' 2-year, 24-hour 3.2 10-year, 24-hour 4.8 25-year, 24-hour 6.2 100-year, 24-hour 8.9 1. Obtained from Section 20-27 0f the North Andover Zoning Bylaw 0r more recent NRCC rainfall data (rounded t0 the nearest 1/10 0f an inch). HydroCAD reports for both existing and proposed conditions for the 2-, 10-1 25-, and 100-year 24- hour storm events listed are provided in the attachments. The peak flows and velocities were analyzed at design point 1 (DP-1). Table 2 provides these results. Table 2® Exeistaing andProposed Peak Results at DP-1 0000 IN I 0 V IIIIIII oiiiiiiii IIIIIII I i � IIIII i IIIII N I Vmiu m m IVI °P18611IIIIIIIIIII..P ulllll�ullllllllllllllUlllll °°°�IIIIIIIII(IIIIIII IIIIIII llllllllllllllllllllllllllllllllllllllll 1.47 0.74 5 0% 0.23 5.0 Il�pppppppppppp�IpluIIIIIpIII�IgIIIIpI��IlUllllll IIIII...Illllllllllllllllllllllllllllllllllllllllllllllllllllllllll�illllllllllllllllllllllllllll Illulllllllll�lllllll °°I — ..u�6 ":9U!!!' uuuuuuuuuuuuuuuuuuu 2.90 1.58 46% 1.88 5.0 11 iiol Iu�9lullllllllllllllllllll�llllllllll 4.23 3.17 2 5% 2.63 5.0 IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII)I�IIII�IIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIII IIIIIIIII�IIIIIIIIlllu III II 6.83 6.44 6% 3.15 5.0 IIIIfpa Irt- smc o II Page 2 of 2 Table 3 presents a runoff volume comparison for the 100-year storm event. Table 3- 100-year Storm Event Runoff Volume Comparison Existing 0.486 acre-feet � ' • Proposed 0.427 acre-feet Reduction 12% Table 3 indicates a reduction in runoff volume discharging to Design Point 1 during the 100-year storm event which further indicates that no downstream flooding is anticipated during the 100-year storm event as a result of the project. Recharge The project will result in a reduction in paved and impervious surface area by replacing hard packed gravel surfaces with grass or permeable concrete pavers. Therefore,the sites'ability to recharge stormwater runoff will be improved. In addition, bioretention areas are provided to capture a portion of the Site's runoff and runoff from Great Pond Road. Water Quality Water quality provisions are provided to remove TSS and other pollutants from the stormwater runoff prior to discharge to receiving waters. Currently,there are no stormwater management systems or BMPs on the property. Under proposed conditions, two (2) bioretention areas are designed to meet water quality requirements of the North Andover Stormwater Management Bylaw and the MassDEP Stormwater Standards. Overall,there is a reduction in imperviousness to the redeveloped project area. Redevelopment The project is the redevelopment of the existing driveway, parking area, boat ramp, and stone retaining walls.The project proposes to improve stormwater management through the implementation of BMPs and provide a net reduction in impervious areas. In general,the project has been designed in compliance with MassDEP Stormwater Standards and the North Andover Stormwater Regulations. Landscape Design A planting plan is provided in the permit drawings. Plantings shall be submitted to the Conservation Commission for approval prior to purchasing and installing plantings.The Contractor will work with representatives of the Conservation Commission to identify trees to be cut and the location/distribution of plantings within the planting areas. envpartners.com Existing Model Report is 2S SC-01 SC-02 1 R DP-1 - Lake Cochichewick Subcat Reach Pond Link Routing Diagram for Existing_N.Andover Boat Launch_revSept20 4 Prepared by Apex Companies, Printed 9/11/2024 HydroCAD®10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Existing_N. Andover Boat Launch_revSept2024 Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 2 Rainfall Events Listing Event# Event Storm Type Curve Mode Duration B/B Depth AMC Name (hours) (inches) 1 2-yr, 24-hr Type III 24-hr Default 24.00 1 3.20 2 2 10-yr, 24-hr Type III 24-hr Default 24.00 1 4.80 2 3 25-yr, 24-hr Type III 24-hr Default 24.00 1 6.20 2 4 100-yr, 24-hr Type III 24-hr Default 24.00 1 8.90 2 Existing_N. Andover Boat Launch_revSept2024 Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 3 Area Listing (all nodes) Area CN Description (sq-ft) (subcatchment-numbers) 21,593 74 >75% Grass cover, Good, HSG C (1 S) 2S) 55074 96 Gravel, HSG C (1 S) 41843 98 Paved, HSG C (1 S) 2S) 81288 70 Woods, Good, HSG C (1 S, 2S) 39,798 79 TOTAL AREA Existing_N. Andover Boat Launch_revSept2024 Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 4 Soil Listing (all nodes) Area Soil Subcatchment (sq-ft) Group Numbers 0 HSG A 0 HSG B 39,798 HSG C 1 S, 2S 0 HSG D 0 Other 3%798 TOTAL AREA Existing_N. Andover Boat Launch_revSept2024 Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 5 Ground Covers (all nodes) HSG-A HSG-6 HSG-C HSG-D Other Total Ground Su (sq-ft) (sq-ft) (sq-ft) (sq-ft) (sq-ft) (sq-ft) Cover NL 0 0 21,593 0 0 211593 >75% Grass cover, Good 0 0 51074 0 0 53074 Gravel 0 0 41843 0 0 43843 Paved 0 0 8,288 0 0 81288 Woods, Good 0 0 399798 0 0 39,798 TOTAL AREA Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 6 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: SC-01 Runoff Area=21,643 sf 13.26% Impervious Runoff Depth=1.54" Flow Length=206' Tc=5.0 min CN=82 Runoff=0.93 cfs 2,774 cf Subcatchment2S: SC-02 Runoff Area=18,155 sf 10.87% Impervious Runoff Depth=1.15" Flow Length=141' Tc=5.8 min CN=76 Runoff=0.55 cfs 1,743 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=1.47 cfs 4,517 cf Outflow=1.47 cfs 4,517 cf Total Runoff Area = 39,798 sf Runoff Volume = 4,517 cf Average Runoff Depth = 1.36" 87.83% Pervious = 34,955 sf 12.17% Impervious = 4,843 sf Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 1 S: SC-01 A Tc of 5-min min. was used Runoff = 0.93 cfs @ 12.08 hrs, Volume= 2,774 cf, Depth= 1.54" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2-yr, 24-hr Rainfall=3.20" Area (sf) CN Description 57074 96 Gravel, HSG C 27870 98 Paved, HSG C 41233 70 Woods, Good, HSG C 9,466 74 >75% Grass cover, Good, HSG C 217643 82 Weighted Average 187773 86.74% Pervious Area 21870 13.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 28 0.0380 1.38 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.20" 0.1 22 0.0164 2.60 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 1.4 140 0.0070 1.70 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 0.0 16 0.1400 7.60 Shallow Concentrated Flow, SCF, paved boat ramp Paved Kv= 20.3 fps 1.8 206 Total, Increased to minimum Tc = 5.0 min Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 8 Subcatchment 1 S: SC-01 Hydrograph 1El Runoff 0.93 cfs Type III 24=hr 2=yr j 24=hr Rainfall=3.20" Runoff Area=21,643 sf 1102 0 Runoff Volume=2,774 cf 0 Runoff Depth=1.54" a Flow Length=206' Tc=5.0 min CN=82 0 U U U U U U U U I a a a a I a a a a I a a a P, 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type 111 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 2S: SC-02 Runoff = 0.55 cfs @ 12.09 hrs, Volume= 1,743 cf, Depth= 1.15" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2-yr, 24-hr Rainfall=3.20" Area (sf) CN Description 1,973 98 Paved, HSG C 4,055 70 Woods, Good, HSG C 121127 74 >75% Grass cover, Good, HSG C 181155 76 Weighted Average 16,182 89.13% Pervious Area 1,973 10.87% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 14 0.0200 0.93 Sheet Flow, Sheet flow, first 50% paved Smooth surfaces n= 0.011 P2= 3.20" 4.4 36 0.0190 0.14 Sheet Flow, Sheet Flow, first 50', grass Grass: Short n= 0.150 P2= 3.20" 0.7 56 0.0400 1.40 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.4 35 0.0900 1.50 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 5.8 141 Total Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 10 Subcatchment 2S: SC-02 Hydrograph 0.6 El Runoff 0.55 cfs 0.55,11,111, Type III 24=hr 0.5 2=yr - Rainfall=3.20"24 hr 0.4 Runoff Area=18,155 sf y 0.35 Runoff Volume=1,743 cf Runoff Depth=1.15" Flow Length=141' 0.2 ' a Tc=5.8-m n 0.15 CN=76 0.1 - 0.05 r r r 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 11 Summary for Reach 1 R: DP-1 - Lake Cochichewick DP-1 is used as a common point(Lake C.) to analyze peak flows in existing and proposed conditions [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.17% Impervious, Inflow Depth = 1.36" for 2-yr, 24-hr event Inflow = 1.47 cfs @ 12.08 hrs, Volume= 4,517 cf Outflow = 1.47 cfs @ 12.08 hrs, Volume= 4,517 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph EM Inflow 1.47 cfs Outflow 1.47 cfs Inflow Area=39,798 sf o 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existi n g_N. Andover Boat La u n c h_revSe pt2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 12 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: SC-01 Runoff Area=21,643 sf 13.26% Impervious Runoff Depth=2.90" Flow Length=206' Tc=5.0 min CN=82 Runoff=1.75 cfs 5,232 cf Subcatchment2S: SC-02 Runoff Area=18,155 sf 10.87% Impervious Runoff Depth=2.37" Flow Length=141' Tc=5.8 min CN=76 Runoff=1.16 cfs 3,588 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=2.90 cfs 8,820 cf Outflow=2.90 cfs 8,820 cf Total Runoff Area = 39,798 sf Runoff Volume = 8,820 cf Average Runoff Depth = 2.66" 87.83% Pervious = 34,955 sf 12.17% Impervious = 4,843 sf Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 13 Summary for Subcatchment 1 S: SC-01 A Tc of 5-min min. was used Runoff = 1.75 cfs @ 12.07 hrs, Volume= 5,232 cf, Depth= 2.90" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10-yr, 24-hr Rainfall=4.80" Area (sf) CN Description 57074 96 Gravel, HSG C 27870 98 Paved, HSG C 41233 70 Woods, Good, HSG C 9,466 74 >75% Grass cover, Good, HSG C 217643 82 Weighted Average 187773 86.74% Pervious Area 21870 13.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 28 0.0380 1.38 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.20" 0.1 22 0.0164 2.60 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 1.4 140 0.0070 1.70 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 0.0 16 0.1400 7.60 Shallow Concentrated Flow, SCF, paved boat ramp Paved Kv= 20.3 fps 1.8 206 Total, Increased to minimum Tc = 5.0 min Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 14 Subcatchment 1 S: SC-01 Hydrograph El Runoff 1.75 cfs Type III 24=hr 1 Omyr 24=hr Rainfall=4.80" Runoff Area=21,643 sf Runoff Volume=5,232 cf 0 Runoff Depth=2.90" Flow Length=206' Tc=5.0 min CN=82 / MR/ M�� r �n// �O 0aI a a a a a I a a a a I 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type 111 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 15 Summary for Subcatchment 2S: SC-02 Runoff = 1.16 cfs @ 12.09 hrs, Volume= 3,588 cf, Depth= 2.37" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10-yr, 24-hr Rainfall=4.80" Area (sf) CN Description 1,973 98 Paved, HSG C 4,055 70 Woods, Good, HSG C 121127 74 >75% Grass cover, Good, HSG C 181155 76 Weighted Average 16,182 89.13% Pervious Area 1,973 10.87% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 14 0.0200 0.93 Sheet Flow, Sheet flow, first 50% paved Smooth surfaces n= 0.011 P2= 3.20" 4.4 36 0.0190 0.14 Sheet Flow, Sheet Flow, first 50', grass Grass: Short n= 0.150 P2= 3.20" 0.7 56 0.0400 1.40 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.4 35 0.0900 1.50 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 5.8 141 Total Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 16 Subcatchment 2S: SC-02 Hydrograph El Runoff 1.16 cfs Type III 24=hr 1 0_yr 1 24=hr Rainfall=4.80" Runoff Area=18,155 sf Runoff Volume=3,588 cf 0 Runoff Depth=2.37" Flow Length=141' Tc=5.8 min CN=76 00/5"O"RI/5"'i ii 01 1 1 1 1 1 a am"" 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 17 Summary for Reach 1 R: DP-1 - Lake Cochichewick DP-1 is used as a common point(Lake C.) to analyze peak flows in existing and proposed conditions [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.17% Impervious, Inflow Depth = 2.66" for 10-yr, 24-hr event Inflow = 2.90 cfs @ 12.08 hrs, Volume= 8,820 cf Outflow = 2.90 cfs @ 12.08 hrs, Volume= 8,820 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph EM Inflow 2.90 cfs ED]Outflow 3 2.90 cfs Inflow Area=39,798 sf 2 1 'j i 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 18 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: SC-01 Runoff Area=21,643 sf 13.26% Impervious Runoff Depth=4.17" Flow Length=206' Tc=5.0 min CN=82 Runoff=2.49 cfs 7,524 cf Subcatchment2S: SC-02 Runoff Area=18,155 sf 10.87% Impervious Runoff Depth=3.55" Flow Length=141' Tc=5.8 min CN=76 Runoff=1.75 cfs 5,376 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=4.23 cfs 12,900 cf Outflow=4.23 cfs 12,900 cf Total Runoff Area = 39,798 sf Runoff Volume = 12,900 cf Average Runoff Depth = 3.89" 87.83% Pervious = 34,955 sf 12.17% Impervious = 4,843 sf Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 19 Summary for Subcatchment 1 S: SC-01 A Tc of 5-min min. was used Runoff = 2.49 cfs @ 12.07 hrs, Volume= 7,524 cf, Depth= 4.17" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25-yr, 24-hr Rainfall=6.20" Area (sf) CN Description 57074 96 Gravel, HSG C 27870 98 Paved, HSG C 41233 70 Woods, Good, HSG C 9,466 74 >75% Grass cover, Good, HSG C 217643 82 Weighted Average 187773 86.74% Pervious Area 21870 13.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 28 0.0380 1.38 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.20" 0.1 22 0.0164 2.60 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 1.4 140 0.0070 1.70 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 0.0 16 0.1400 7.60 Shallow Concentrated Flow, SCF, paved boat ramp Paved Kv= 20.3 fps 1.8 206 Total, Increased to minimum Tc = 5.0 min Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 20 Subcatchment 1 S: SC-01 Hydrograph El Runoff 2.49 cfs Type III 24=hr 25=yr 2 / 24=hr Rainfall=6.20" Runoff Area=21,643 sf 1102 Runoff Volume=7,524 cf 0 UL Runoff Depth=4.17" 1 % Flow Length=206' Tc=5.0 min CN=82 0 11711711 U U Uii U U U�j I I I I I I I I I I I I a I a a U 1111 1111 1111 11111111 1111 1111 1111 1111 1111�IIF]IIF-U-U-u-u-l-w-uu-u-]FU-Tu-u-]FU-U-U-T]Fu-v-m OW, " i 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type 111 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 21 Summary for Subcatchment 2S: SC-02 Runoff = 1.75 cfs @ 12.09 hrs, Volume= 5,376 cf, Depth= 3.55" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25-yr, 24-hr Rainfall=6.20" Area (sf) CN Description 1,973 98 Paved, HSG C 4,055 70 Woods, Good, HSG C 121127 74 >75% Grass cover, Good, HSG C 181155 76 Weighted Average 16,182 89.13% Pervious Area 1,973 10.87% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 14 0.0200 0.93 Sheet Flow, Sheet flow, first 50% paved Smooth surfaces n= 0.011 P2= 3.20" 4.4 36 0.0190 0.14 Sheet Flow, Sheet Flow, first 50', grass Grass: Short n= 0.150 P2= 3.20" 0.7 56 0.0400 1.40 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.4 35 0.0900 1.50 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 5.8 141 Total Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 22 Subcatchment 2S: SC-02 Hydrograph El Runoff 1.75 cfs Type III 24=hr 25=yr 24=hr Rainfall=6.20" Runoff Area=18,155 sf Runoff Volume=5,376 cf 0 Runoff Depth=3.55" a Flow Length=141' a Tc=5.8 min CN=76 0 111 a I m a a a I V V V V I V V a a a a a a I a a a a I a a m U I a a a a I a a a a I a I 1 1111 1111 1111 1111'111'111 1111 1111 1111 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 23 Summary for Reach 1 R: DP-1 - Lake Cochichewick DP-1 is used as a common point(Lake C.) to analyze peak flows in existing and proposed conditions [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.17% Impervious, Inflow Depth = 3.89" for 25-yr, 24-hr event Inflow = 4.23 cfs @ 12.08 hrs, Volume= 121900 cf Outflow = 4.23 cfs @ 12.08 hrs, Volume= 12,900 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph El Inflow 4.23 cfs ED outflOW 4.23cfs Inflow Area=39,798 sf 4 3 o UL 2 I i 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 24 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: SC-01 Runoff Area=21,643 sf 13.26% Impervious Runoff Depth=6.72" Flow Length=206' Tc=5.0 min CN=82 Runoff=3.94 cfs 12,117 cf Subcatchment2S: SC-02 Runoff Area=18,155 sf 10.87% Impervious Runoff Depth=5.98" Flow Length=141' Tc=5.8 min CN=76 Runoff=2.92 cfs 9,052 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=6.83 cfs 21,169 cf Outflow=6.83 cfs 21,169 cf Total Runoff Area = 39,798 sf Runoff Volume = 21,169 cf Average Runoff Depth = 6.38" 87.83% Pervious = 34,955 sf 12.17% Impervious = 4,843 sf Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 25 Summary for Subcatchment 1 S: SC-01 A Tc of 5-min min. was used Runoff = 3.94 cfs @ 12.07 hrs, Volume= 12,117 cf, Depth= 6.72" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-yr, 24-hr Rainfall=8.90" Area (sf) CN Description 57074 96 Gravel, HSG C 27870 98 Paved, HSG C 41233 70 Woods, Good, HSG C 9,466 74 >75% Grass cover, Good, HSG C 217643 82 Weighted Average 187773 86.74% Pervious Area 21870 13.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 28 0.0380 1.38 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.20" 0.1 22 0.0164 2.60 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 1.4 140 0.0070 1.70 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 0.0 16 0.1400 7.60 Shallow Concentrated Flow, SCF, paved boat ramp Paved Kv= 20.3 fps 1.8 206 Total, Increased to minimum Tc = 5.0 min Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 26 Subcatchment 1 S: SC-01 Hydrograph El Runoff 3.94 cfs 4 / Type III 24-hr 100- r y M"r, 24-hr Rainfall=8.90" 3 Runoff Area=21,643 sf j Runoff Volume=12,117 cf Runoff Depth=6.72" Flow Length=206' Tc=5.0 min 1 % CN=82 1 0: 2/ I I IMM 0 a I a a a a I a a a gp—n-I-TTR a a I a 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type 111 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 27 Summary for Subcatchment 2S: SC-02 Runoff = 2.92 cfs @ 12.08 hrs, Volume= 9,052 cf, Depth= 5.98" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-yr, 24-hr Rainfall=8.90" Area (sf) CN Description 1,973 98 Paved, HSG C 4,055 70 Woods, Good, HSG C 121127 74 >75% Grass cover, Good, HSG C 181155 76 Weighted Average 16,182 89.13% Pervious Area 1,973 10.87% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 14 0.0200 0.93 Sheet Flow, Sheet flow, first 50% paved Smooth surfaces n= 0.011 P2= 3.20" 4.4 36 0.0190 0.14 Sheet Flow, Sheet Flow, first 50', grass Grass: Short n= 0.150 P2= 3.20" 0.7 56 0.0400 1.40 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.4 35 0.0900 1.50 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 5.8 141 Total Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 28 Subcatchment 2S: SC-02 Hydrograph El Runoff 3, 2.92 cfs /. Type III 24=hr j 1 00=yr 24=hr Rainfall=8.90" 2-1 Runoff Area=18,155 sf Runoff Volume=9,052 cf 0 Runoff Depth=5.98" Flow Length=141' Tc=5.8 min CN=76 0 jir7ir7ii U U U U U U U U U U U U U U U U U U U U U U U U U U U1 11 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 29 Summary for Reach 1 R: DP-1 - Lake Cochichewick DP-1 is used as a common point(Lake C.) to analyze peak flows in existing and proposed conditions [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.17% Impervious, Inflow Depth = 6.38" for 100-yr, 24-hr event Inflow = 6.83 cfs @ 12.08 hrs, Volume= 21,169 cf Outflow = 6.83 cfs @ 12.08 hrs, Volume= 21,169 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph EM Inflow 6.83 cfs Outflow 7 6.83 cfs Inflow Area=39,798 sf 6 - - - 4 3 o LL 3 2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 30 Events for Subcatchment 1 S: SC-01 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-h r 3.20 0.93 2,774 1.54 10-yr, 24-hr 4.80 1.75 5,232 2.90 25-yr, 24-h r 6.20 2.49 75524 4.17 100-yr, 24-hr 8.90 3.94 121117 6.72 Existing_N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 31 Events for Subcatchment 2S: SC-02 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-h r 3.20 0.55 1,743 1.15 10-yr, 24-h r 4.80 1.16 3588 2.37 25-yr, 24-h r 6.20 1.75 55376 3.55 100-yr, 24-hr 8.90 2.92 9,052 5.98 Existing_N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 32 Events for Reach 1 R: DP-1 - Lake Cochichewick Event Inflow Outflow Elevation Storage (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-h r 1.47 1.47 0.00 0 10-yr, 24-h r 2.90 2.90 0.00 0 25-yr, 24-h r 4.23 4.23 0.00 0 100-yr, 24-hr 6.83 6.83 0.00 0 Existing_N. Andover Boat Launch_revSept2024 Table of Contents Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC TABLE OF CONTENTS Project Reports 1 Routing Diagram 2 Rainfall Events Listing 3 Area Listing (all nodes) 4 Soil Listing (all nodes) 5 Ground Covers (all nodes) 2-yr, 24-hr Event 6 Node Listing 7 Subcat 1 S: SC-01 9 Subcat 2S: SC-02 11 Reach 1 R: DP-1 - Lake Cochichewick 10-yr, 24-hr Event 12 Node Listing 13 Subcat 1 S: SC-01 15 Subcat 2S: SC-02 17 Reach 1 R: DP-1 - Lake Cochichewick 25-yr, 24-hr Event 18 Node Listing 19 Subcat 1 S: SC-01 21 Subcat 2S: SC-02 23 Reach 1 R: DP-1 - Lake Cochichewick 100-yr, 24-hr Event 24 Node Listing 25 Subcat 1 S: SC-01 27 Subcat 2S: SC-02 29 Reach 1 R: DP-1 - Lake Cochichewick Multi-Event Tables 30 Subcat 1 S: SC-01 31 Subcat 2S: SC-02 32 Reach 1 R: DP-1 - Lake Cochichewick Proposed Model Report 4S 3S SC-04 Sd-03 AP 2 P 1 P Bio. Ret. Area #1 12" RCP Bio. Ret. Area #2 is 3R 2S SC-01 Rip-Rai) Swale SC-02 1R DP-1 - Lake Cochichewick Subcat Reach Pond Link Routing Diagram for Proposed—N.Andover Boat Launch_revSept20 4 Prepared by Apex Companies, Printed 9/11/2024 HydroCAD®10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Proposed—N. Andover Boat Launch_revSept2024 Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 2 Rainfall Events Listing Event# Event Storm Type Curve Mode Duration B/B Depth AMC Name (hours) (inches) 1 2-yr, 24-hr Type III 24-hr Default 24.00 1 3.20 2 2 10-yr, 24-hr Type III 24-hr Default 24.00 1 4.80 2 3 25-yr, 24-hr Type III 24-hr Default 24.00 1 6.20 2 4 100-yr, 24-hr Type III 24-hr Default 24.00 1 8.90 2 Proposed—N. Andover Boat Launch_revSept2024 Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 3 Area Listing (all nodes) Area CN Description (sq-ft) (subcatchment-numbers) 16764 74 >75% Grass cover, Good, HSG C (1 S) 2S, 3S7 4S) 483 98 Paved, HSG C (3S) 4S) 91991 80 Permeable Pavers, HSG C (1 S, 2S, 3S, 4S) 11196 74 Rain Garden, Good, HSG C (3S) 991 74 Rain garden, Good, HSG C (4S) 41664 98 Roadway, HSG C (1 S, 2S, 3S, 4S) 55709 70 Woods, Good, HSG C (1 S, 2S) 395798 78 TOTAL AREA Proposed—N. Andover Boat Launch_revSept2024 Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 4 Soil Listing (all nodes) Area Soil Subcatchment (sq-ft) Group Numbers 0 HSG A 0 HSG B 39,798 HSG C 1 S, 2S, 3S, 4S 0 HSG D 0 Other 3%798 TOTAL AREA Proposed—N. Andover Boat Launch_revSept2024 Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 5 Ground Covers (all nodes) HSG-A HSG-B HSG-C HSG-D Other Total Ground Su (sq-ft) (sq-ft) (sq-ft) (sq-ft) (sq-ft) (sq-ft) Cover NL 0 0 16,764 0 0 161764 >75% Grass cover, Good 0 0 483 0 0 483 Paved 0 0 91991 0 0 9,991 Permeable Pavers 0 0 17196 0 0 1,196 Rain Garden, Good 0 0 991 0 0 991 Rain garden, Good 0 0 47664 0 0 43664 Roadway 0 0 57709 0 0 5,709 Woods, Good 0 0 39J98 0 0 397798 TOTAL AREA Proposed—N. Andover Boat Launch_revSept2024 Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 6 Pipe Listing (all nodes) Line# Node In-Invert Out-Invert Length Slope n Width Diam/Height Inside-Fill Node Number (feet) (feet) (feet) (ft/ft) (inches) (inches) (inches) Name 1 5P 115.50 115.30 44.0 0.0045 0.012 0.0 12.0 0.0 Proposed-N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 7 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1 S: SC-01 Runoff Area=13,643 sf 4.25% Impervious Runoff Depth=1.15" Flow Length=131' Tc=5.0 min CN=76 Runoff=0.42 cfs 1,310 cf Subcatchment2S: SC-02 Runoff Area=10,661 sf 5.67% Impervious Runoff Depth=1.09" Flow Length=97' Tc=5.0 min CN=75 Runoff=0.31 cfs 972 cf Subcatchment3S: SC-03 Runoff Area=9,610 sf 19.84% Impervious Runoff Depth=1.54" Flow Length=63' Slope=0.0100 '/' Tc=5.0 min CN=82 Runoff=0.41 cfs 1,232 cf Subcatchment4S: SC-04 Runoff Area=5,884 sf 34.94% Impervious Runoff Depth=1.61" Flow Length=52' Tc=5.0 min CN=83 Runoff=0.26 cfs 789 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=0.74 cfs 2,288 cf Outflow=0.74 cfs 2,288 cf Reach 3R: Rip-Rap Swale Avg. Flow Depth=0.00' Max Vet=0.23 fps Inflow=0.00 cfs 6 cf n=0.041 L=13.0' 5=0.0500 '/' Capacity=4.54 cfs Outflow=0.00 cfs 6 cf Pond 1 P: Bio. Ret.Area IN #2 Peak Elev=116.51' Storage=745 cf Inflow=0.41 cfs 1,232 cf Discarded=0.00 cfs 668 cf Primary=0.03 cfs 299 cf Outflow=0.03 cfs 967 cf Pond 2P: Bio. Ret.Area#1 Peak EIev=116.50' Storage=887 cf Inflow=0.26 cfs 1,088 cf Discarded=0.00 cfs 834 cf Primary=0.00 cfs 6 cf Outflow=0.01 cfs 840 cf Pond 5P: 12" RCP Peak EIev=116.50' Inflow=0.03 cfs 299 cf 12.0" Round Culvert n=0.012 L=44.0' S=0.0045 '/' Outflow=0.03 cfs 299 cf Total Runoff Area = 39,798 sf Runoff Volume = 4,302 cf Average Runoff Depth = 1.30" 87.07% Pervious = 34,651 sf 12.93% Impervious = 5,147 sf Proposed-N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment 1 S: SC-01 Runoff = 0.42 cfs @ 12.08 hrs, Volume= 1,310 cf, Depth= 1.15" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2-yr, 24-hr Rainfall=3.20" Area (sf) CN Description 27459 80 Permeable Pavers, HSG C 580 98 Roadway, HSG C 17813 70 Woods, Good, HSG C 87791 74 >75% Grass cover, Good, HSG C 137643 76 Weighted Average 13,063 95.75% Pervious Area 580 4.25% Impervious Area Tic Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 50 0.0150 1.07 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.20" 0.4 66 0.0300 2.79 Shallow Concentrated Flow, SCF, driveway Unpaved Kv= 16.1 fps 0.0 15 0.1200 5.58 Shallow Concentrated Flow, SCF, paved boat ramp Unpaved Kv= 16.1 fps 1.2 131 Total, Increased to minimum Tc = 5.0 min Subcatchment 1 S: SC-01 Hydrograph I El 0.46 Runoff 0.44 0.42 cfs 0.42 Type III 24=hr 0.4 0.38 2=yr 0.36 0.3 j 24-hr Rainfall=3.20" 0.32 0.3 0.28 Runoff Area=13,643 sf 4 0.26 RunoffVolume=1,310 d 0.24 0 00.2 Runoff Depth=1.15" 0.18 Flow Length=131' 0.16 0.14 Tc=5.0 m i n 0.12 0.1 ` / CN=76 0.06 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 2S: SC-02 Runoff = 0.31 cfs @ 12.08 hrs, Volume= 972 cf, Depth= 1.09" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2-yr, 24-hr Rainfall=3.20" Area (sf) CN Description 1,219 80 Permeable Pavers, HSG C 3,896 70 Woods, Good, HSG C 4,942 74 >75% Grass cover, Good, HSG C 604 98 Roadway, HSG C 10,661 75 Weighted Average 101057 94.33% Pervious Area 604 5.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 15 0.0200 0.94 Sheet Flow, Sheet flow, first 50', roadway Smooth surfaces n= 0.011 P2= 3.20" 2.5 35 0.0714 0.23 Sheet Flow, Sheet flow, first 50', woods Grass: Short n= 0.150 P2= 3.20" 0.2 15 0.0350 1.31 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.3 32 0.1060 1.63 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 3.3 97 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 10 Subcatchment 2S: SC-02 Hydrograph 0.34 El Runoff 0.32 0.31 cfs 0.3 Type III 24=hr 0.28 2=yr 0.26 0.24 24-hr Rainfall=3.20" 0.22 Runoff Area=10,661 sf - Runoff Volume=972 cf r, .2 Runoff0.16 �; Depth=1.09" LL 0.14 Flow Length=97' 0.12 - 0.1 Tc=5.0 min r CN=75 0.06 i!rr 0.04 r ' 0.02 01„,,,% a 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment 3S: SC-03 Runoff = 0.41 cfs @ 12.08 hrs, Volume= 1,232 cf, Depth= 1.54" Routed to Pond 1 P : Bio. Ret. Area #2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2-yr, 24-hr Rainfall=3.20" Area (sf) CN Description 1,672 98 Roadway, HSG C 235 98 Paved, HSG C 5,257 80 Permeable Pavers, HSG C 1,196 74 Rain Garden, Good, HSG C 1,250 74 >75% Grass cover, Good, HSG C 9,610 82 Weighted Average 7,703 80.16% Pervious Area 1,907 19.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.91 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.20" 0.1 10 0.0100 1.61 Shallow Concentrated Flow, SCF, pavers Unpaved Kv= 16.1 fps 0.1 3 0.0100 0.70 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 1.1 63 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 12 Subcatchment 3S: SC-03 Hydrograph 0.46 El Runoff 0.44 0.42 0.41 cfs Type III 24-h r r -y 0.36 2 0.34 / 24 h r Rai nfal I=3.20 0.32 0.3 / 'Runoff Area 9,610 sf 0.2s 0.26 j Runoff Volume=1,232'cf Runoff Depth=1.54"l 0 0.22 Flow Length=63' 0.1s 0.16 % Slope=0.01 00 0.14 % 0.12`1 Tc=5.0 m i n 0.1 CN=82 0.06 i 0.02 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 13 Summary for Subcatchment 4S: SC-04 Runoff = 0.26 cfs @ 12.08 hrs, Volume= 789 cf, Depth= 1.61" Routed to Pond 2P : Bio. Ret. Area #1 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2-yr, 24-hr Rainfall=3.20" Area (sf) CN Description 1,808 98 Roadway, HSG C 248 98 Paved, HSG C 1,056 80 Permeable Pavers, HSG C 991 74 Rain garden, Good, HSG C 1,781 74 >75% Grass cover, Good, HSG C 5,884 83 Weighted Average 3,828 65.06% Pervious Area 2,056 34.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 33 0.0200 1.10 Sheet Flow, Sheet flow, pavers Smooth surfaces n= 0.011 P2= 3.20" 0.6 6 0.0750 0.16 Sheet Flow, Sheet flow, first 50', grass Grass: Short n= 0.150 P2= 3.20" 0.0 13 0.0500 4.43 7.54 Channel Flow, Swale Area= 1.7 sf Perim= 4.2' r= 0.40' n= 0.041 Riprap, 2-inch 1.1 52 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 14 Subcatchment 4S: SC-04 Hydrograph El 0.28 Runoff 0.26 cfs 0.26 Type III 24=hr / 2=yr � // 24=hr Rainfall=3.20" 0.2 0.1 sArea=5,884 sf ,/ Runoff 0.16 �. / Runoff Volume=789 cf c 0.14 Runoff Depth=1.61 wl 0.12 Flow Length=52' 0.1 0.08 Tc=5.0 min 0.06 CN=83 0.02 0 � 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCADO 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 15 Summary for Reach 1 R: DP-1 - Lake Cochichewick [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.93% Impervious, Inflow Depth = 0.69" for 2-yr, 24-hr event Inflow = 0.74 cfs @ 12.08 hrs, Volume= 2,288 cf Outflow = 0.74 cfs @ 12.08 hrs, Volume= 2,288 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph El Inflow 0.8 0.74 cfs _ - _ - - - -- �,,�: Outflow 0.75 0.74 cfs Inflow Area=39,798 sf 0.7 0.65 0.55 0.5 0.45 3 0.4 0 0.35 0.3 0.2 3 0.15 j 3 0.1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 16 Summary for Reach 3R: Rip-Rap Swale Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 0.00" for 2-yr, 24-hr event Inflow = 0.00 cfs @ 21.45 hrs, Volume= 6 cf Outflow = 0.00 cfs @ 21.49 hrs, Volume= 6 cf, Atten= 0%, Lag= 1.9 min Routed to Reach 1 R : DP-1 - Lake Cochichewick Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Max. Velocity= 0.23 fps, Min. Travel Time= 0.9 min Avg. Velocity = 0.23 fps, Avg. Travel Time= 0.9 min Peak Storage= 0 cf @ 21.47 hrs Average Depth at Peak Storage= 0.00' , Surface Width= 1.03' Bank-Full Depth= 0.50' Flow Area= 1.3 sf, Capacity= 4.54 cfs 1.00' x 0.50' deep channel, n= 0.041 Riprap, 2-inch Side Slope Z-value= 3.0 '/' Top Width= 4.00' Length= 13.0' Slope= 0.0500 '/' Inlet Invert= 116.50', Outlet Invert= 115.85' Reach 3R: Rip-Rap Swale Hydrograph IM Inflow 0.00 cfs El Outflow 0.001 0.00 cfs I of I ow AreaIIIIIIIIIIIIIIIIIIIIII 15 sf 0.001 Avg. Flow 0.001 Max Vel=0.23 fps 0.001 0.001`1111111 n=0.041 C.) 0.001 0 0.001`1111111 L=1 3.0' i , S=0.0500 T 0.000 Capacity=4.54 cfs 0.000 0.000 0.000, 0 01 1111111 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 17 Summary for Pond 1P: Bio. Ret. Area #2 Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 1.54" for 2-yr, 24-hr event Inflow = 0.41 cfs @ 12.08 hrs, Volume= 1,232 cf Outflow = 0.03 cfs @ 13.46 hrs, Volume= 967 cf, Atten= 92%, Lag= 83.3 min Discarded = 0.00 cfs @ 13.46 hrs, Volume= 668 cf Primary = 0.03 cfs @ 13.46 hrs, Volume= 299 cf Routed to Pond 5P : 12" RCP Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.51'@ 13.46 hrs Surf.Area= 975 sf Storage= 745 cf Flood Elev= 117.00' Surf.Area= 1,176 sf Storage= 1,269 cf Plug-Flow detention time= 1,034.5 min calculated for 967 cf(78% of inflow) Center-of-Mass det. time= 952.5 min ( 1,787.8 - 835.3 ) Volume Invert Avail.Storage Storage Description #1 115.50' 1,269 cf Custom Stage Data (Conic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.50 419 0 0 419 116.00 784 296 296 787 117.00 17176 973 11269 15194 Device Routing Invert Outlet Devices #1 Discarded 115.50' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' 24.0" Horiz. Top of Riser C= 0.600 Limited to weir flow at low heads Discarded Outflow Max=0.00 cfs @ 13.46 hrs HW=116.51' (Free Discharge) L1=Exfi1tration ( Controls 0.00 cfs) Primary OutFlow Max=0.02 cfs @ 13.46 hrs HW=116.51' (Free Discharge) L2=Top of Riser (Weir Controls 0.02 cfs @ 0.35 fps) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 18 Pond 1P: Bio. Ret. Area #2 Hydrograph EM Inflow 0.41 cfs Outflow Discarded 0.46 Inflow Area=9,61 0 sf Primary 0.44 0.42 Peak Elev=1 16.51' 0.4 0.38 Storage=745 cf 0.36 0.34 0.32 0.3 0.28 —�- 0.24 c0.22111111�� 0.2 0.18 0.16 0.14 12,1111111 0.1 0.03 cfs 0.08 0.06 s , 0.04 0.03 cfs 0.02 0 2 4 6 8 10 12 1416 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 19 Summary for Pond 2P: Bio. Ret. Area #1 [81] Warning: Exceeded Pond 5P by 0.54' @ 13.14 hrs Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 0.84" for 2-yr, 24-hr event Inflow = 0.26 cfs @ 12.08 hrs, Volume= 1,088 cf Outflow = 0.01 cfs @ 21.45 hrs, Volume= 840 cf, Atten= 98%, Lag= 562.7 min Discarded = 0.00 cfs @ 21.45 hrs, Volume= 834 cf Primary = 0.00 cfs @ 21.45 hrs, Volume= 6 cf Routed to Reach 3R : Rip-Rap Swale Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.50'@ 21.45 hrs Surf.Area= 992 sf Storage= 887 cf Flood Elev= 117.00' Surf.Area= 1,201 sf Storage= 1,432 cf Plug-Flow detention time= 1,527.7 min calculated for 840 cf(77% of inflow) Center-of-Mass det. time= 1,446.0 min ( 2,310.4 - 864.4 ) Volume Invert Avail.Storage Storage Description #1 115.00' 1,432 cf Custom Stage Data (Conic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.00 0 0 0 0 115.50 590 98 98 590 116.00 787 343 441 793 116.50 991 444 885 17003 117.00 11201 547 11432 11222 Device Routing Invert Outlet Devices #1 Discarded 115.00' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' Channel/Reach using Reach 3R: Rip-Rap Swale Discarded OutFlow Max=0.00 cfs @ 21.45 hrs HW=116.50' (Free Discharge) L1=Exfi1tration ( Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 21.45 hrs HW=116.50' (Free Discharge) L2=Channel/Reach (Channel Controls 0.00 cfs, @ 0.12 fps) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 20 Pond 2P: Bio. Ret. Area #1 Hydrograph EM Inflow 0.26 cfs 11 Outflow Inflow Area=15 494 sf ES 0 discarded � Primary 0.28 Peak Elev=l 16.50' 0.26 0.24 Storage=887 cf 0.22 0.2 0.18 0.16 c 0.14 0.12 0.1 0.08 0.06 luiou 0.01 cfs 0.04 0.00 cfs 0.02 � 0.00 CfSf� 0 2 4 6 8 10 12 1416 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 2-yr, 24-hr Rainfall=3.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 21 Summary for Pond 5P: 12" RCP Inflow Area = 91610 sf, 19.84% Impervious, Inflow Depth = 0.37" for 2-yr, 24-hr event Inflow = 0.03 cfs @ 13.46 hrs, Volume= 299 cf Outflow = 0.03 cfs @ 13.46 hrs, Volume= 299 cf, Atten= 0%, Lag= 0.0 min Primary = 0.03 cfs @ 13.46 hrs, Volume= 299 cf Routed to Pond 2P : Bio. Ret. Area #1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.50'@ 13.46 hrs Flood Elev= 117.00' Device Routing Invert Outlet Devices #1 Primary 115.50' 12.0" Round Culvert L= 44.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet/ Outlet Invert= 115.50'/ 115.30' S= 0.0045'/' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 0.79 sf Primary OutFlow Max=0.08 cfs, @ 13.46 hrs HW=116.50' TW=116.50' (Fixed TW Elev= 116.50') L1=Culvert (Outlet Controls 0.08 cfs @ 0.13 fps) Pond 5P: 12" RCP Hydrograph Inflow El 0.03 cfs Primary 0.03 0.03 cfsInflow Area=9,61 0 sf 0.028,1111111 i 0.026 Peak Elev=1 16 0.024 110"0.022 r 0.02 Round Culvert 0.018 60 0.016 n= 12 0 � M 0.014 j L=44.0'0.012 0.01 T S 0.0045 0.008 % 0.006 ' 0.004 0.002 111u uu uuuu uu MUM U M my Mugu my U guy u U uu uu U u uu u UY guy, Q1111111111111111 J1111uuuuuuu uu UUMMMMUMMMMUM ' 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed-N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 22 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1 S: SC-01 Runoff Area=13,643 sf 4.25% Impervious Runoff Depth=2.37" Flow Length=131' Tc=5.0 min CN=76 Runoff=0.90 cfs 2,696 cf Subcatchment2S: SC-02 Runoff Area=10,661 sf 5.67% Impervious Runoff Depth=2.29" Flow Length=97' Tc=5.0 min CN=75 Runoff=0.68 cfs 2,033 cf Subcatchment3S: SC-03 Runoff Area=9,610 sf 19.84% Impervious Runoff Depth=2.90" Flow Length=63' Slope=0.0100 '/' Tc=5.0 min CN=82 Runoff=0.78 cfs 2,323 cf Subcatchment4S: SC-04 Runoff Area=5,884 sf 34.94% Impervious Runoff Depth=2.99" Flow Length=52' Tc=5.0 min CN=83 Runoff=0.49 cfs 1,468 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=1.58 cfs 6,458 cf Outflow=1.58 cfs 6,458 cf Reach 3R: Rip-Rap Swale Avg. Flow Depth=0.15' Max Vet=1.88 fps Inflow=0.41 cfs 1,729 cf n=0.041 L=13.0' S=0.0500 T Capacity=4.54 cfs Outflow=0.41 cfs 1,729 cf Pond 1 P: Bio. Ret.Area#2 Peak Elev=116.59' Storage=821 cf Inflow=0.78 cfs 2,323 cf Discarded=0.00 cfs 679 cf Primary=0.54 cfs 1,378 cf Outflow=0.54 cfs 2,058 cf Pond 2P: Bio. Ret.Area#1 Peak Elev=116.65' Storage=1,038 cf Inflow=0.90 cfs 2,846 cf Discarded=0.01 cfs 865 cf Primary=0.41 cfs 1,729 cf Outflow=0.41 cfs 2,594 cf Pond 5P: 12" RCP Peak Elev=116.53' Inflow=0.54 cfs 1,378 cf 12.0" Round Culvert n=0.012 L=44.0' S=0.0045 '/' Outflow=0.54 cfs 1,378 cf Total Runoff Area = 39,798 sf Runoff Volume = 8,520 cf Average Runoff Depth = 2.57" 87.07% Pervious = 34,651 sf 12.93% Impervious = 5,147 sf Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 23 Summary for Subcatchment 1 S: SC-01 Runoff = 0.90 cfs @ 12.08 hrs, Volume= 2,696 cf, Depth= 2.37" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10-yr, 24-hr Rainfall=4.80" Area (sf) CN Description 27459 80 Permeable Pavers, HSG C 580 98 Roadway, HSG C 17813 70 Woods, Good, HSG C 87791 74 >75% Grass cover, Good, HSG C 137643 76 Weighted Average 13,063 95.75% Pervious Area 580 4.25% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 50 0.0150 1.07 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.20" 0.4 66 0.0300 2.79 Shallow Concentrated Flow, SCF, driveway Unpaved Kv= 16.1 fps 0.0 15 0.1200 5.58 Shallow Concentrated Flow, SCF, paved boat ramp Unpaved Kv= 16.1 fps 1.2 131 Total, Increased to minimum Tc = 5.0 min Subcatchment 1 S: SC-01 Hydrograph 1I El Runoff 0.90 cfs Type III 24=hr 1 Omyr 24=hr Rainfall=4.80" ON Runoff Area=13,643 sf Runoff Volume=2,696 d 0 Runoff Depth=2.37" Flow Length=131' Tc=5.0 min CN=76 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 24 Summary for Subcatchment 2S: SC-02 Runoff = 0.68 cfs @ 12.08 hrs, Volume= 2,033 cf, Depth= 2.29" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10-yr, 24-hr Rainfall=4.80" Area (sf) CN Description 1,219 80 Permeable Pavers, HSG C 3,896 70 Woods, Good, HSG C 4,942 74 >75% Grass cover, Good, HSG C 604 98 Roadway, HSG C 10,661 75 Weighted Average 101057 94.33% Pervious Area 604 5.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 15 0.0200 0.94 Sheet Flow, Sheet flow, first 50', roadway Smooth surfaces n= 0.011 P2= 3.20" 2.5 35 0.0714 0.23 Sheet Flow, Sheet flow, first 50', woods Grass: Short n= 0.150 P2= 3.20" 0.2 15 0.0350 1.31 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.3 32 0.1060 1.63 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 3.3 97 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 25 Subcatchment 2S: SC-02 Hydrograph 0.75El Runoff 0.7 0.68 cfs Type III 24=hr 0.65 _ 0.6 1Omyr 0.55 24-hr Rainfall=4.80" 0.5 Runoff Area=10,661 sf 0.45 0.4 1102 Runoff Volume=2,033 cf 3 0 Runoff Depth=2.29" 0.3 Flow Length=97' 0.25 Tc=5.0 min- 0.15 CN=75 0.05 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 26 Summary for Subcatchment 3S: SC-03 Runoff = 0.78 cfs @ 12.07 hrs, Volume= 2,323 cf, Depth= 2.90" Routed to Pond 1 P : Bio. Ret. Area #2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10-yr, 24-hr Rainfall=4.80" Area (sf) CN Description 1,672 98 Roadway, HSG C 235 98 Paved, HSG C 5,257 80 Permeable Pavers, HSG C 1,196 74 Rain Garden, Good, HSG C 1,250 74 >75% Grass cover, Good, HSG C 9,610 82 Weighted Average 7,703 80.16% Pervious Area 1,907 19.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.91 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.20" 0.1 10 0.0100 1.61 Shallow Concentrated Flow, SCF, pavers Unpaved Kv= 16.1 fps 0.1 3 0.0100 0.70 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 1.1 63 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 27 Subcatchment 3S: SC-03 Hydrograph 0.85 El Runoff 0.8 0.78 cfs Type III 24-h r 0.75 0.7 10-yr 0.65 24 hr Rainfall 4 80110.6 0.55 - Runoff Area=9�610 sf 0.5 / Runoff Volume=2,323'cf 0.45 Runoff De th=2.90 .� � 0.4 o UL 0.35 ��% _ a Flow Length=63' 0.3 j Slope=0.01 00 0.25 Tc_5.0 min 0.2 CN=82 0.15 0.1 i u 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 28 Summary for Subcatchment 4S: SC-04 Runoff = 0.49 cfs @ 12.07 hrs, Volume= 1,468 cf, Depth= 2.99" Routed to Pond 2P : Bio. Ret. Area #1 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10-yr, 24-hr Rainfall=4.80" Area (sf) CN Description 1,808 98 Roadway, HSG C 248 98 Paved, HSG C 1,056 80 Permeable Pavers, HSG C 991 74 Rain garden, Good, HSG C 1,781 74 >75% Grass cover, Good, HSG C 5,884 83 Weighted Average 3,828 65.06% Pervious Area 2,056 34.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 33 0.0200 1.10 Sheet Flow, Sheet flow, pavers Smooth surfaces n= 0.011 P2= 3.20" 0.6 6 0.0750 0.16 Sheet Flow, Sheet flow, first 50', grass Grass: Short n= 0.150 P2= 3.20" 0.0 13 0.0500 4.43 7.54 Channel Flow, Swale Area= 1.7 sf Perim= 4.2' r= 0.40' n= 0.041 Riprap, 2-inch 1.1 52 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 29 Subcatchment 4S: SC-04 Hydrograph El Runoff 0.5 0.49 cfs Type III 24=hr 1Omyr 0.4 24=hr Rainfall=4.80" 0.35 Runoff Area=5,884 sf// 0.3 Runoff Volume=1,468 cf 0.25UL Runoff Depth=2.99" 0.2 Flow Length=52' 0.15 % Tc=5.0 min CN=83 0.1 i i r r 0 ISO VOW -a r r 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCADO 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 30 Summary for Reach 1 R: DP-1 - Lake Cochichewick [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.93% Impervious, Inflow Depth = 1.95" for 10-yr, 24-hr event Inflow = 1.58 cfs @ 12.08 hrs, Volume= 6,458 cf Outflow = 1.58 cfs @ 12.08 hrs, Volume= 6,458 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph El Inflow 1.58 cfs � outflow 1.58 cfs lnflow Area=39,798 sf _O i i 0 U 9 9 9 U 9 9 9 9 U 9 9 9 9 U Y Y Y 111,1111 111,11111111 1111 1111 1111 11111111 1111 1111 1111 11111111 1111 1111 1111 11111111 U 1111 M 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed-N. Andover Boat Launch_revSept2024 Type 111 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 31 Summary for Reach 3R: Rip-Rap Swale Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 1.34" for 10-yr, 24-hr event Inflow = 0.41 cfs @ 12.39 hrs, Volume= 1,729 cf Outflow = 0.41 cfs @ 12.40 hrs, Volume= 1,729 cf, Atten= 0%, Lag= 0.2 min Routed to Reach 1 R : DP-1 - Lake Cochichewick Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Max. Velocity= 1.88 fps, Min. Travel Time= 0.1 min Avg. Velocity = 0.74 fps, Avg. Travel Time= 0.3 min Peak Storage= 3 cf @ 12.39 hrs Average Depth at Peak Storage= 0.15' , Surface Width= 1.90' Bank-Full Depth= 0.50' Flow Area= 1.3 sf, Capacity= 4.54 cfs 1.00' x 0.50' deep channel, n= 0.041 Riprap, 2-inch Side Slope Z-value= 3.0 '/' Top Width= 4.00' Length= 13.0' Slope= 0.0500 '/' Inlet Invert= 116.50', Outlet Invert= 115.85' Reach 3R: Rip-Rap Swale Hydrograph Inflow - - - El Outflow 0.44 0.41 cfs 0.42 0 41 ifs I of I ow Area=15 sf 0.4 0.38 Avg. Flow Depth=0.15' 0.36 0.34 Max VeI-1 .88 fps - 0.32 - - - - - - -0.3 i n=0.041 0.2s N 26 0. 0.24 ' L=1 3.0' -�- 3 0.22 C 0.2 ; S=0.0500 T - 0.18 0.16 Capacity=4.54 cfs � - 0.14 - - - 0.12 0.1 0.08 0.06 0.04 0.02 i r /, 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 32 Summary for Pond 1P: Bio. Ret. Area #2 Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 2.90" for 10-yr, 24-hr event Inflow = 0.78 cfs @ 12.07 hrs, Volume= 2,323 cf Outflow = 0.54 cfs @ 12.15 hrs, Volume= 2,058 cf, Atten= 30%, Lag= 4.5 min Discarded = 0.00 cfs @ 12.15 hrs, Volume= 679 cf Primary = 0.54 cfs @ 12.15 hrs, Volume= 1,378 cf Routed to Pond 5P : 12" RCP Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.59'@ 12.15 hrs Surf.Area= 1,005 sf Storage= 821 cf Flood Elev= 117.00' Surf.Area= 1,176 sf Storage= 1,269 cf Plug-Flow detention time=514.7 min calculated for 2,058 cf(89% of inflow) Center-of-Mass det. time=461.1 min ( 1,278.2 - 817.1 ) Volume Invert Avail.Storage Storage Description #1 115.50' 1,269 cf Custom Stage Data (Conic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.50 419 0 0 419 116.00 784 296 296 787 117.00 17176 973 11269 15194 Device Routing Invert Outlet Devices #1 Discarded 115.50' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' 24.0" Horiz. Top of Riser C= 0.600 Limited to weir flow at low heads Discarded Outflow Max=0.00 cfs @ 12.15 hrs HW=116.59' (Free Discharge) L1=Exfi1tration ( Controls 0.00 cfs) Primary OutFlow Max=0.54 cfs @ 12.15 hrs HW=116.59' (Free Discharge) L2=Top of Riser (Weir Controls 0.54 cfs @ 0.97 fps) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 33 Pond 1P: Bio. Ret. Area #2 Hydrograph EM Inflow 0.7s cfs II llll Outflow Discarded 0.85 Inflow Area=9,61 0 sf Primary 0.8 Peak Elev=1 16.59' 0.75 0.7 1 1 Storage=821 cf 0.65 0.54 cfs 0.6 0.54 cfs 0.55 n 0.5 0.45 0 0.4 � 0.35 0.3 0.25 0.2 0.15 0.1 i® 0.05 0 2 4 6 8 10 12 1416 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 34 Summary for Pond 2P: Bio. Ret. Area #1 [81] Warning: Exceeded Pond 5P by 0.52' @ 12.07 hrs Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 2.20" for 10-yr, 24-hr event Inflow = 0.90 cfs @ 12.13 hrs, Volume= 2,846 cf Outflow = 0.41 cfs @ 12.39 hrs, Volume= 2,594 cf, Atten= 54%, Lag= 15.5 min Discarded = 0.01 cfs @ 12.39 hrs, Volume= 865 cf Primary = 0.41 cfs @ 12.39 hrs, Volume= 1,729 cf Routed to Reach 3R : Rip-Rap Swale Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.65'@ 12.39 hrs Surf.Area= 1,052 sf Storage= 1,038 cf Flood Elev= 117.00' Surf.Area= 1,201 sf Storage= 1,432 cf Plug-Flow detention time=554.1 min calculated for 2,594 cf(91% of inflow) Center-of-Mass det. time= 512.2 min ( 1,345.0 - 832.8 ) Volume Invert Avail.Storage Storage Description #1 115.00' 1,432 cf Custom Stage Data (Conic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.00 0 0 0 0 115.50 590 98 98 590 116.00 787 343 441 793 116.50 991 444 885 17003 117.00 11201 547 11432 11222 Device Routing Invert Outlet Devices #1 Discarded 115.00' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' Channel/Reach using Reach 3R: Rip-Rap Swale Discarded OutFlow Max=0.01 cfs @ 12.39 hrs HW=116.65' (Free Discharge) L1=Exfi1tration ( Controls 0.01 cfs) Primary OutFlow Max=0.41 cfs @ 12.39 hrs HW=116.65' (Free Discharge) L2=Channel/Reach (Channel Controls 0.41 cfs, @ 1.88 fps) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 35 Pond 2P: Bio. Ret. Area #1 Hydrograph EM Inflow 0.90 cfs Outflow Discarded 1 I nfl ow Area=15,494 sf Primary Peak Elev=l 16.65' Storage=1,038 cf v 0.41 cfs C 0.41 cfs LL i i 0 '/„ „�i. ,�/✓'„ Lac / „,/ f /„ „�, ///!,,,„/,,,// 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed-N. Andover Boat Launch_revSept2024 Type 111 24-hr 10-yr, 24-hr Rainfall=4.80" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 36 Summary for Pond 5P: 12" RCP [79] Warning: Submerged Pond 1P Primary device # 2 by 0.03' Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 1.72" for 10-yr, 24-hr event Inflow = 0.54 cfs @ 12.15 hrs, Volume= 1,378 cf Outflow = 0.54 cfs @ 12.15 hrs, Volume= 1,378 cf, Atten= 0%, Lag= 0.0 min Primary = 0.54 cfs @ 12.15 hrs, Volume= 1,378 cf Routed to Pond 2P : Bio. Ret. Area #1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.53'@ 12.15 hrs Flood Elev= 117.00' Device Routing Invert Outlet Devices #1 Primary 115.50' 12.0" Round Culvert L= 44.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet/ Outlet Invert= 115.50'/ 115.30' S= 0.0045'/' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 0.79 sf Primary OutFlow Max=0.54 cfs @ 12.15 hrs HW=116.53' TW=116.50' (Fixed TW Elev= 116.50') L1=Culvert (Outlet Controls 0.54 cfs @ 0.84 fps) Pond 5P: 12" RCP Hydrograph El Inflow 0.6El 0.54 cfs Primary 0.55 0.54 cf, Inflow Area=9 610 sf 0.5 j Peak Elev=l ' 16.53 0.45 12m0" 0.4 Round Culvert n=0.01 2 0.3 o 0.25 L=44.0' 0.2 S=OmOO45 T 0.15 0.1 0.05 / 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed-N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 37 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1 S: SC-01 Runoff Area=13,643 sf 4.25% Impervious Runoff Depth=3.55" Flow Length=131' Tc=5.0 min CN=76 Runoff=1.35 cfs 4,040 cf Subcatchment2S: SC-02 Runoff Area=10,661 sf 5.67% Impervious Runoff Depth=3.45" Flow Length=97' Tc=5.0 min CN=75 Runoff=1.03 cfs 3,068 cf Subcatchment3S: SC-03 Runoff Area=9,610 sf 19.84% Impervious Runoff Depth=4.17" Flow Length=63' Slope=0.0100 '/' Tc=5.0 min CN=82 Runoff=1.11 cfs 3,341 cf Subcatchment4S: SC-04 Runoff Area=5,884 sf 34.94% Impervious Runoff Depth=4.28" Flow Length=52' Tc=5.0 min CN=83 Runoff=0.69 cfs 2,097 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=3.17 cfs 10,460 cf Outflow=3.17 cfs 10,460 cf Reach 3R: Rip-Rap Swale Avg. Flow Depth=0.28' Max Vet=2.63 fps Inflow=1.34 cfs 3,352 cf n=0.041 L=13.0' S=0.0500 '/' Capacity=4.54 cfs Outflow=1.34 cfs 3,352 cf Pond 1 P: Bio. Ret.Area#2 Peak Elev=116.64' Storage=871 cf Inflow=1.11 cfs 3,341 cf Discarded=0.00 cfs 689 cf Primary=1.05 cfs 2,386 cf Outflow=1.05 cfs 3,075 cf Pond 2P: Bio. Ret.Area#1 Peak Elev=116.78' Storage=1,176 cf Inflow=1.72 cfs 4,484 cf Discarded=0.01 cfs 877 cf Primary=1.34 cfs 3,352 cf Outflow=1.35 cfs 4,229 cf Pond 5P: 12" RCP Peak Elev=116.59' Inflow=1.05 cfs 2,386 cf 12.0" Round Culvert n=0.012 L=44.0' S=0.0045 '/' Outflow=1.05 cfs 2,386 cf Total Runoff Area = 39,798 sf Runoff Volume = 12,546 cf Average Runoff Depth = 3.78" 87.07% Pervious = 34,651 sf 12.93% Impervious = 5,147 sf Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 38 Summary for Subcatchment 1 S: SC-01 Runoff = 1.35 cfs @ 12.07 hrs, Volume= 4,040 cf, Depth= 3.55" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25-yr, 24-hr Rainfall=6.20" Area (sf) CN Description 27459 80 Permeable Pavers, HSG C 580 98 Roadway, HSG C 17813 70 Woods, Good, HSG C 87791 74 >75% Grass cover, Good, HSG C 137643 76 Weighted Average 13,063 95.75% Pervious Area 580 4.25% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 50 0.0150 1.07 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.20" 0.4 66 0.0300 2.79 Shallow Concentrated Flow, SCF, driveway Unpaved Kv= 16.1 fps 0.0 15 0.1200 5.58 Shallow Concentrated Flow, SCF, paved boat ramp Unpaved Kv= 16.1 fps 1.2 131 Total, Increased to minimum Tc = 5.0 min Subcatchment 1 S: SC-01 Hydrograph El Runoff 1.35 cfs Type III 24=hr 25myr 24=hr Rainfall=6.20" Runoff Area=13,643 sf Runoff Volume=4,040 d 0 Runoff Depth=3.55" Flew Length=131' Tc=5.0 min CN=76 r 0 , , r 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 39 Summary for Subcatchment 2S: SC-02 Runoff = 1.03 cfs @ 12.07 hrs, Volume= 3,068 cf, Depth= 3.45" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25-yr, 24-hr Rainfall=6.20" Area (sf) CN Description 1,219 80 Permeable Pavers, HSG C 3,896 70 Woods, Good, HSG C 4,942 74 >75% Grass cover, Good, HSG C 604 98 Roadway, HSG C 10,661 75 Weighted Average 101057 94.33% Pervious Area 604 5.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 15 0.0200 0.94 Sheet Flow, Sheet flow, first 50', roadway Smooth surfaces n= 0.011 P2= 3.20" 2.5 35 0.0714 0.23 Sheet Flow, Sheet flow, first 50', woods Grass: Short n= 0.150 P2= 3.20" 0.2 15 0.0350 1.31 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.3 32 0.1060 1.63 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 3.3 97 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 40 Subcatchment 2S: SC-02 Hydrograph El Runoff 1.03 cfs 1 / Type III 24=hr 25=yr 24=hr Rainfall=6.20" Runoff Area=1 0 sf 1*2 Runoff Volume=3,068 cf 0 Runoff Depth=3.45" Flow Length=97' Tc=5.0 min CN=75 1, , f O 1 PUT!IT IT i 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 5860 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 41 Summary for Subcatchment 3S: SC-03 Runoff = 1.11 cfs @ 12.07 hrs, Volume= 3,341 cf, Depth= 4.17" Routed to Pond 1 P : Bio. Ret. Area #2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25-yr, 24-hr Rainfall=6.20" Area (sf) CN Description 1,672 98 Roadway, HSG C 235 98 Paved, HSG C 5,257 80 Permeable Pavers, HSG C 1,196 74 Rain Garden, Good, HSG C 1,250 74 >75% Grass cover, Good, HSG C 9,610 82 Weighted Average 7,703 80.16% Pervious Area 1,907 19.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.91 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.20" 0.1 10 0.0100 1.61 Shallow Concentrated Flow, SCF, pavers Unpaved Kv= 16.1 fps 0.1 3 0.0100 0.70 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 1.1 63 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 42 Subcatchment 3S: SC-03 Hydrograph El Runoff 1.11 cfs Type III 24-h r 25-yr 24-h r Rainfall=6.20 Runoff Area=9 610 sf ,% Runoff Vo I u m e 3,341 cf o Runoff Depth=4.17 Flow Length=63' Slope=0.01 00 Tc=5.0 min CN=82 r i 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 43 Summary for Subcatchment 4S: SC-04 Runoff = 0.69 cfs @ 12.07 hrs, Volume= 2,097 cf, Depth= 4.28" Routed to Pond 2P : Bio. Ret. Area #1 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25-yr, 24-hr Rainfall=6.20" Area (sf) CN Description 1,808 98 Roadway, HSG C 248 98 Paved, HSG C 1,056 80 Permeable Pavers, HSG C 991 74 Rain garden, Good, HSG C 1,781 74 >75% Grass cover, Good, HSG C 5,884 83 Weighted Average 3,828 65.06% Pervious Area 2,056 34.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 33 0.0200 1.10 Sheet Flow, Sheet flow, pavers Smooth surfaces n= 0.011 P2= 3.20" 0.6 6 0.0750 0.16 Sheet Flow, Sheet flow, first 50', grass Grass: Short n= 0.150 P2= 3.20" 0.0 13 0.0500 4.43 7.54 Channel Flow, Swale Area= 1.7 sf Perim= 4.2' r= 0.40' n= 0.041 Riprap, 2-inch 1.1 52 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 44 Subcatchment 4S: SC-04 Hydrograph 0.75 El Runoff 0.69 cfs 0.7 " Type III 24=hr 0.65 0.6 25=yr 0.55 24=hr Rainfall=6.20" 0.5 Runoff Area=5,884 sf . � 04 5 0.4 � - - - Runoff Volume=2,097 cf_ ° 0.35 Runoff Depth=4.28" 0.3 Flow Length=52' 0.25 0.2 Tc=5.0 min- 0.15 / CN=83 0.05 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCADO 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 45 Summary for Reach 1 R: DP-1 - Lake Cochichewick [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.93% Impervious, Inflow Depth = 3.15" for 25-yr, 24-hr event Inflow = 3.17 cfs @ 12.12 hrs, Volume= 10,460 cf Outflow = 3.17 cfs @ 12.12 hrs, Volume= 10,460 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph El Inflow 3.17 cfs E Outflow 3.1�ifs Inflow Area=39,798 sf 3 ,r LL r" 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 46 Summary for Reach 3R: Rip-Rap Swale Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 2.60" for 25-yr, 24-hr event Inflow = 1.34 cfs @ 12.15 hrs, Volume= 3,352 cf Outflow = 1.34 cfs @ 12.15 hrs, Volume= 3,352 cf, Atten= 0%, Lag= 0.1 min Routed to Reach 1 R : DP-1 - Lake Cochichewick Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Max. Velocity= 2.63 fps, Min. Travel Time= 0.1 min Avg. Velocity = 0.87 fps, Avg. Travel Time= 0.2 min Peak Storage= 7 cf @ 12.15 hrs Average Depth at Peak Storage= 0.28' , Surface Width= 2.67' Bank-Full Depth= 0.50' Flow Area= 1.3 sf, Capacity= 4.54 cfs 1.00' x 0.50' deep channel, n= 0.041 Riprap, 2-inch Side Slope Z-value= 3.0 '/' Top Width= 4.00' Length= 13.0' Slope= 0.0500 '/' Inlet Invert= 116.50', Outlet Invert= 115.85' � � r � � r � I I I I I I I� I� I I J Reach 3R: Rip-Rap Swale Hydrograph IM Inflow 1.34 cfs / Outflow 1.34cfs I nfl ow Area=15,494 sf Avg. Flow Depth=0.28' Max Vel=2.63 fps n=0.041 L=1 3.0 ° S=0.0500 T Capacity=4.54 cfs j -„.�,,: i.,., o. .,-.,-.,i,/ , i., a, rr.,- 'err,/, rr:,.,' c,a - . ./,ir:,.., Y gill, 1111 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 47 Summary for Pond 1P: Bio. Ret. Area #2 Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 4.17" for 25-yr, 24-hr event Inflow = 1.11 cfs @ 12.07 hrs, Volume= 3,341 cf Outflow = 1.05 cfs @ 12.10 hrs, Volume= 3,075 cf, Atten= 5%, Lag= 1.5 min Discarded = 0.00 cfs @ 12.10 hrs, Volume= 689 cf Primary = 1.05 cfs @ 12.10 hrs, Volume= 2,386 cf Routed to Pond 5P : 12" RCP Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.64'@ 12.10 hrs Surf.Area= 1,025 sf Storage= 871 cf Flood Elev= 117.00' Surf.Area= 1,176 sf Storage= 1,269 cf Plug-Flow detention time=356.9 min calculated for 3,075 cf(92% of inflow) Center-of-Mass det. time= 316.6 min ( 1,123.3 - 806.7 ) Volume Invert Avail.Storage Storage Description #1 115.50' 1,269 cf Custom Stage Data (Conic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.50 419 0 0 419 116.00 784 296 296 787 117.00 17176 973 11269 15194 Device Routing Invert Outlet Devices #1 Discarded 115.50' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' 24.0" Horiz. Top of Riser C= 0.600 Limited to weir flow at low heads Discarded Outflow Max=0.00 cfs @ 12.10 hrs HW=116.64' (Free Discharge) L1=Exfiltration ( Controls 0.00 cfs) Primary OutFlow Max=1.05 cfs @ 12.10 hrs HW=116.64' (Free Discharge) L2=Top of Riser (Weir Controls 1.05 cfs @ 1.21 fps) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 48 Pond 1P: Bio. Ret. Area #2 Hydrograph Inflow 1.11 cfs Outflow Inflow Area=9,61 0 sf Discarded 1.05 cfs � � � � � � � � Primary 1.0 Peak Elev=1 16.64' 1 Storage=871 cf o �i S p 'U'UU U Alu 0 11111111 11111111 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 49 Summary for Pond 2P: Bio. Ret. Area #1 [81] Warning: Exceeded Pond 5P by 0.53' @ 11.91 hrs Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 3.47" for 25-yr, 24-hr event Inflow = 1.72 cfs @ 12.09 hrs, Volume= 4,484 cf Outflow = 1.35 cfs @ 12.15 hrs, Volume= 4,229 cf, Atten= 22%, Lag= 3.9 min Discarded = 0.01 cfs @ 12.15 hrs, Volume= 877 cf Primary = 1.34 cfs @ 12.15 hrs, Volume= 3,352 cf Routed to Reach 3R : Rip-Rap Swale Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.78'@ 12.15 hrs Surf.Area= 1,105 sf Storage= 1,176 cf Flood Elev= 117.00' Surf.Area= 1,201 sf Storage= 1,432 cf Plug-Flow detention time=350.4 min calculated for 4,229 cf(94% of inflow) Center-of-Mass det. time= 320.7 min ( 1,141.1 - 820.4 ) Volume Invert Avail.Storage Storage Description #1 115.00' 1,432 cf Custom Stage Data (Conic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.00 0 0 0 0 115.50 590 98 98 590 116.00 787 343 441 793 116.50 991 444 885 17003 117.00 11201 547 11432 11222 Device Routing Invert Outlet Devices #1 Discarded 115.00' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' Channel/Reach using Reach 3R: Rip-Rap Swale Discarded OutFlow Max=0.01 cfs @ 12.15 hrs HW=116.78' (Free Discharge) L1=Exfi1tration ( Controls 0.01 cfs) Primary OutFlow Max=1.34 cfs @ 12.15 hrs HW=116.78' (Free Discharge) L2=Channel/Reach (Channel Controls 1.34 cfs, @ 2.63 fps) Proposed—N. Andover Boat Launch_revSept2024 Type /// 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 50 Pond 2P: Bio. Ret. Area #1 Hydrograph Inflow 1.7 Utflow of l ow Area=15 sf � Discarded Primary Peak Elev=l 16.78' 1.35cfs Storage=1,176 cf 1.34 cfs t� i 1 o i 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Type 111 24-hr 25-yr, 24-hr Rainfall=6.20" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 51 Summary for Pond 5P: 12" RCP [79] Warning: Submerged Pond 1P Primary device # 2 by 0.09' Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 2.98" for 25-yr, 24-hr event Inflow = 1.05 cfs @ 12.10 hrs, Volume= 2,386 cf Outflow = 1.05 cfs @ 12.10 hrs, Volume= 2,386 cf, Atten= 0%, Lag= 0.0 min Primary = 1.05 cfs @ 12.10 hrs, Volume= 2,386 cf Routed to Pond 2P : Bio. Ret. Area #1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.59'@ 12.10 hrs Flood Elev= 117.00' Device Routing Invert Outlet Devices #1 Primary 115.50' 12.0" Round Culvert L= 44.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet/ Outlet Invert= 115.50'/ 115.30' S= 0.0045'/' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 0.79 sf Primary OutFlow Max=1.05 cfs @ 12.10 hrs HW=116.59' TW=116.50' (Fixed TW Elev= 116.50') L1=Culvert (Outlet Controls 1.05 cfs @ 1.53 fps) Pond 5P: 12" RCP Hydrograph El Inflow El Primary 1.05 cfs 1.05 cfs Inflow Area 9 sf Peak Elev=1 16.59 / 12m0" 1 Round Culvert n=0.01 2 0 L=44.0' S=0.0045 T 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch_revSept2024Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 52 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1 S: SC-01 Runoff Area=13,643 sf 4.25% Impervious Runoff Depth=5.98" Flow Length=131' Tc=5.0 min CN=76 Runoff=2.25 cfs 6,802 cf Subcatchment2S: SC-02 Runoff Area=10,661 sf 5.67% Impervious Runoff Depth=5.86" Flow Length=97' Tc=5.0 min CN=75 Runoff=1.73 cfs 5,207 cf Subcatchment3S: SC-03 Runoff Area=9,610 sf 19.84% Impervious Runoff Depth=6.72" Flow Length=63' Slope=0.0100 '/' Tc=5.0 min CN=82 Runoff=1.75 cfs 5,380 cf Subcatchment4S: SC-04 Runoff Area=5,884 sf 34.94% Impervious Runoff Depth=6.84" Flow Length=52' Tc=5.0 min CN=83 Runoff=1.09 cfs 3,354 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=6.44 cfs 18,615 cf Outflow=6.44 cfs 18,615 cf Reach 3R: Rip-Rap Swale Avg. Flow Depth=0.39' Max Vet=3.15 fps Inflow=2.63 cfs 6,605 cf n=0.041 L=13.0' S=0.0500 '/' Capacity=4.54 cfs Outflow=2.62 cfs 6,605 cf Pond 1 P: Bio. Ret.Area#2 Peak Elev=116.69' Storage=923 cf Inflow=1.75 cfs 5,380 cf Discarded=0.01 cfs 709 cf Primary=1.68 cfs 4,405 cf Outflow=1.68 cfs 5,114 cf Pond 2P: Bio. Ret.Area#1 Peak Elev=116.89' Storage=1,298 cf Inflow=2.74 cfs 7,759 cf Discarded=0.01 cfs 899 cf Primary=2.63 cfs 6,605 cf Outflow=2.63 cfs 7,504 cf Pond 5P: 12" RCP Peak Elev=116.70' Inflow=1.68 cfs 4,405 cf 12.0" Round Culvert n=0.012 L=44.0' S=0.0045 '/' Outflow=1.68 cfs 4,405 cf Total Runoff Area = 39,798 sf Runoff Volume = 20,743 cf Average Runoff Depth = 6.25" 87.07% Pervious = 34,651 sf 12.93% Impervious = 5,147 sf Proposed_N. Andover Boat Launch_revSept2024Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 53 Summary for Subcatchment 1 S: SC-01 Runoff = 2.25 cfs @ 12.07 hrs, Volume= 6,802 cf, Depth= 5.98" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-yr, 24-hr Rainfall=8.90" Area (sf) CN Description 27459 80 Permeable Pavers, HSG C 580 98 Roadway, HSG C 17813 70 Woods, Good, HSG C 87791 74 >75% Grass cover, Good, HSG C 137643 76 Weighted Average 13,063 95.75% Pervious Area 580 4.25% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 50 0.0150 1.07 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.20" 0.4 66 0.0300 2.79 Shallow Concentrated Flow, SCF, driveway Unpaved Kv= 16.1 fps 0.0 15 0.1200 5.58 Shallow Concentrated Flow, SCF, paved boat ramp Unpaved Kv= 16.1 fps 1.2 131 Total, Increased to minimum Tc = 5.0 min Subcatchment 1 S: SC-01 Hydrograph El Runoff 2.25 cfs Type III 24=hr 2 % 00=yr1 24=hr Rainfall=8.90" Runoff Area=13,643 sf Runoff Volume=6,802 d 0 RunoffDepth=5.98" Flow Length=131' Tc=5.0 min CN=76 r 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch_revSept2024Type 111 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 54 Summary for Subcatchment 2S: SC-02 Runoff = 1.73 cfs @ 12.07 hrs, Volume= 5,207 cf, Depth= 5.86" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-yr, 24-hr Rainfall=8.90" Area (sf) CN Description 1,219 80 Permeable Pavers, HSG C 3,896 70 Woods, Good, HSG C 4,942 74 >75% Grass cover, Good, HSG C 604 98 Roadway, HSG C 10,661 75 Weighted Average 101057 94.33% Pervious Area 604 5.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 15 0.0200 0.94 Sheet Flow, Sheet flow, first 50', roadway Smooth surfaces n= 0.011 P2= 3.20" 2.5 35 0.0714 0.23 Sheet Flow, Sheet flow, first 50', woods Grass: Short n= 0.150 P2= 3.20" 0.2 15 0.0350 1.31 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.3 32 0.1060 1.63 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 3.3 97 Total, Increased to minimum Tc = 5.0 min Proposed_N. Andover Boat Launch_revSept2024Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 55 Subcatchment 2S: SC-02 Hydrograph El Runoff 1.73 cfs Type III 24=hr 1 =0or y 24=hr Rainfall=8.90" Runoff Area=1 0 sf 1102 0 1 Runoff Volume=5,207 cf 0 Runoff Depth=5.86" ice% i i Flow Length=97' Tc=5.0 min CN=75 0-1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch_revSept2024Type 111 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 56 Summary for Subcatchment 3S: SC-03 Runoff = 1.75 cfs @ 12.07 hrs, Volume= 5,380 cf, Depth= 6.72" Routed to Pond 1 P : Bio. Ret. Area #2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-yr, 24-hr Rainfall=8.90" Area (sf) CN Description 1,672 98 Roadway, HSG C 235 98 Paved, HSG C 5,257 80 Permeable Pavers, HSG C 1,196 74 Rain Garden, Good, HSG C 1,250 74 >75% Grass cover, Good, HSG C 9,610 82 Weighted Average 7,703 80.16% Pervious Area 1,907 19.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.91 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.20" 0.1 10 0.0100 1.61 Shallow Concentrated Flow, SCF, pavers Unpaved Kv= 16.1 fps 0.1 3 0.0100 0.70 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 1.1 63 Total, Increased to minimum Tc = 5.0 min Proposed_N. Andover Boat Launch_revSept2024Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 57 Subcatchment 3S: SC-03 Hydrograph El Runoff 1.75 cfs Type III 24-h r 100- r 24-h r Rainfall=8.90 Runoff Area=9,610 sf Runoff Volume=5 380 cf i Runoff Depth=6.72" 1 Flow Length=63r Slope=0.01 00 / Tc=5 0 m i n CN=82 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch_revSept2024Type 111 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 58 Summary for Subcatchment 4S: SC-04 Runoff = 1.09 cfs @ 12.07 hrs, Volume= 3,354 cf, Depth= 6.84" Routed to Pond 2P : Bio. Ret. Area #1 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-yr, 24-hr Rainfall=8.90" Area (sf) CN Description 1,808 98 Roadway, HSG C 248 98 Paved, HSG C 1,056 80 Permeable Pavers, HSG C 991 74 Rain garden, Good, HSG C 1,781 74 >75% Grass cover, Good, HSG C 5,884 83 Weighted Average 3,828 65.06% Pervious Area 2,056 34.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 33 0.0200 1.10 Sheet Flow, Sheet flow, pavers Smooth surfaces n= 0.011 P2= 3.20" 0.6 6 0.0750 0.16 Sheet Flow, Sheet flow, first 50', grass Grass: Short n= 0.150 P2= 3.20" 0.0 13 0.0500 4.43 7.54 Channel Flow, Swale Area= 1.7 sf Perim= 4.2' r= 0.40' n= 0.041 Riprap, 2-inch 1.1 52 Total, Increased to minimum Tc = 5.0 min Proposed_N. Andover Boat Launch_revSept2024Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 59 Subcatchment 4S: SC-04 Hydrograph El Runoff 1.09 cfs j Type III 24=hr 1 1 00=yr 24=hr Rainfall=8.90" Runoff Area=5,884 sf 1102 0 Runoff Volume=3,354 cf 0 Runoff Depth=6.84" Flow Length=52' Tc=5.0 min CN=83 i /ter e �7 ISOM 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch_revSept2024Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCADO 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 60 Summary for Reach 1 R: DP-1 - Lake Cochichewick [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.93% Impervious, Inflow Depth = 5.61" for 100-yr, 24-hr event Inflow = 6.44 cfs @ 12.09 hrs, Volume= 18,615 cf Outflow = 6.44 cfs @ 12.09 hrs, Volume= 18,615 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph El Inflow 7 6.44 cfs ED] outflOW 6.44 fs Inflow' Area=39,798 sf 6 j 4 3 0 2 f „ r rr r/ i r ®r 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch_revSept2024Type 11124-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCADO 10.20-5a s/n 04044 O 2023 HydroCAD Software Solutions LLC Page 61 Summary for Reach 3R: Rip-Rap Swale Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 5.12" for 100-yr, 24-hr event Inflow = 2.63 cfs @ 12.11 hrs, Volume= 6,605 cf Outflow = 2.62 cfs @ 12.11 hrs, Volume= 6,605 cf, Atten= 0%, Lag= 0.1 min Routed to Reach 1 R : DP-1 - Lake Cochichewick Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Max. Velocity= 3.15 fps, Min. Travel Time= 0.1 min Avg. Velocity= 1.06 fps, Avg. Travel Time= 0.2 min Peak Storage= 11 cf @ 12.11 hrs Average Depth at Peak Storage= 0.39' , Surface Width= 3.32' Bank-Full Depth= 0.50' Flow Area= 1.3 sf, Capacity= 4.54 cfs 1.00' x 0.50' deep channel, n= 0.041 Riprap, 2-inch Side Slope Z-value= 3.0 '/' Top Width= 4.00' Length= 13.0' Slope= 0.0500 '/' Inlet Invert= 116.50', Outlet Invert= 115.85' $ mw Reach 3R: Rip-Rap Swale Hydrograph IM Inflow 2.63 cfs 0�U�OW 2.62°fs Infl ow Area=15,494 sf Avg. Flow Depth=0.39' Max Vel=3.1 5 fps 2 n=0.041 L=1 3.0' 0 S=0.0500 T Capacity=4.54 cfs 111 :'!IN-1:3-i i! iii ii o e 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch_revSept2024Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 62 Summary for Pond 1P: Bio. Ret. Area #2 Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 6.72" for 100-yr, 24-hr event Inflow = 1.75 cfs @ 12.07 hrs, Volume= 5,380 cf Outflow = 1.68 cfs @ 12.09 hrs, Volume= 5,114 cf, Atten= 4%, Lag= 1.3 min Discarded = 0.01 cfs @ 12.09 hrs, Volume= 709 cf Primary = 1.68 cfs @ 12.09 hrs, Volume= 4,405 cf Routed to Pond 5P : 12" RCP Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.69'@ 12.09 hrs Surf.Area= 1,045 sf Storage= 923 cf Flood Elev= 117.00' Surf.Area= 1,176 sf Storage= 1,269 cf Plug-Flow detention time=228.1 min calculated for 5,113 cf(95% of inflow) Center-of-Mass det. time=200.7 min ( 994.1 - 793.4 ) Volume Invert Avail.Storage Storage Description #1 115.50' 1,269 cf Custom Stage Data (Conic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.50 419 0 0 419 116.00 784 296 296 787 117.00 17176 973 11269 15194 Device Routing Invert Outlet Devices #1 Discarded 115.50' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' 24.0" Horiz. Top of Riser C= 0.600 Limited to weir flow at low heads Discarded Outflow Max=0.01 cfs @ 12.09 hrs HW=116.69' (Free Discharge) L1=Exfi1tration ( Controls 0.01 cfs) Primary OutFlow Max=1.67 cfs @ 12.09 hrs HW=116.69' (Free Discharge) L2=Top of Riser (Weir Controls 1.67 cfs @ 1.42 fps) Proposed_N. Andover Boat Launch_revSept2024Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 63 Pond 1P: Bio. Ret. Area #2 Hydrograph Inflow 1.75 cfs Outflow of I ow Area=9 61 0 sf Discarded 1.68 cfs 7 � Primary 1.68cfs Peak Elev=l 16.69' Storage=923 cf o j UL r l MINE!I 0 MR 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch_revSept2024Type 111 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 64 Summary for Pond 2P: Bio. Ret. Area #1 [81] Warning: Exceeded Pond 5P by 0.53' @ 11.34 hrs Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 6.01" for 100-yr, 24-hr event Inflow = 2.74 cfs @ 12.08 hrs, Volume= 7,759 cf Outflow = 2.63 cfs @ 12.11 hrs, Volume= 7,504 cf, Atten= 4%, Lag= 1.4 min Discarded = 0.01 cfs @ 12.11 hrs, Volume= 899 cf Primary = 2.63 cfs @ 12.11 hrs, Volume= 6,605 cf Routed to Reach 3R : Rip-Rap Swale Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.89'@ 12.11 hrs Surf.Area= 1,151 sf Storage= 1,298 cf Flood Elev= 117.00' Surf.Area= 1,201 sf Storage= 1,432 cf Plug-Flow detention time=206.6 min calculated for 7,503 cf(97% of inflow) Center-of-Mass det. time= 188.2 min ( 995.1 - 806.9 ) Volume Invert Avail.Storage Storage Description #1 115.00' 1,432 cf Custom Stage Data (Conic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.00 0 0 0 0 115.50 590 98 98 590 116.00 787 343 441 793 116.50 991 444 885 17003 117.00 11201 547 11432 11222 Device Routing Invert Outlet Devices #1 Discarded 115.00' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' Channel/Reach using Reach 3R: Rip-Rap Swale Discarded OutFlow Max=0.01 cfs @ 12.11 hrs HW=116.89' (Free Discharge) L1=Exfi1tration ( Controls 0.01 cfs) Primary OutFlow Max=2.62 cfs @ 12.11 hrs HW=116.89' (Free Discharge) L2=Channel/Reach (Channel Controls 2.62 cfs, @ 3.15 fps) Proposed_N. Andover Boat Launch_revSept2024Type /// 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 65 Pond 2P: Bio. Ret. Area #1 Hydrograph Inflow 2.74 cfs Outflow Discarded 3 2.63cfs Infl ow Area=15,494 sf .� Primary 2.63cfs Peak Elev=l 16.89' j Storage=1,298 cf O i i r 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch_revSept2024Type 111 24-hr 100-yr, 24-hr Rainfall=8.90" Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 66 Summary for Pond 5P: 12" RCP [81] Warning: Exceeded Pond 1 P by 0.01' @ 12.09 hrs Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 5.50" for 100-yr, 24-hr event Inflow = 1.68 cfs @ 12.09 hrs, Volume= 4,405 cf Outflow = 1.68 cfs @ 12.09 hrs, Volume= 4,405 cf, Atten= 0%, Lag= 0.0 min Primary = 1.68 cfs @ 12.09 hrs, Volume= 4,405 cf Routed to Pond 2P : Bio. Ret. Area #1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.70'@ 12.09 hrs Flood Elev= 117.00' Device Routing Invert Outlet Devices #1 Primary 115.50' 12.0" Round Culvert L= 44.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet/ Outlet Invert= 115.50'/ 115.30' S= 0.0045'/' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 0.79 sf Primary OutFlow Max=1.68 cfs @ 12.09 hrs HW=116.70' TW=116.50' (Fixed TW Elev= 116.50') L1=Culvert (Inlet Controls 1.68 cfs @ 2.13 fps) Pond 5P: 12" RCP Hydrograph El Inflow El Primary 1.68 cfs 1.68 cfs Inflow Area=9,61 0 sf Peak Elev=l 16.70' 12m0" Round Culvert 1 / n=0.01 2 0 L=44.0' S=0.0045 T .,o�'r'./. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 67 Events for Subcatchment 1 S: SC-01 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-h r 3.20 0.42 1,310 1.15 10-yr, 24-h r 4.80 0.90 2,696 2.37 25-yr, 24-h r 6.20 1.35 45040 3.55 100-yr, 24-hr 8.90 2.25 6,802 5.98 Proposed—N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 68 Events for Subcatchment 2S: SC-02 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-h r 3.20 0.31 972 1.09 10-yr, 24-h r 4.80 0.68 2,033 2.29 25-yr, 24-h r 6.20 1.03 3,068 3.45 100-yr, 24-hr 8.90 1.73 5,207 5.86 Proposed—N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 69 Events for Subcatchment 3S: SC-03 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-hr 3.20 0.41 1,232 1.54 10-yr, 24-h r 4.80 0.78 2,323 2.90 25-yr, 24-h r 6.20 1.11 35341 4.17 100-yr, 24-hr 8.90 1.75 5,380 6.72 Proposed—N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 70 Events for Subcatchment 4S: SC-04 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-h r 3.20 0.26 789 1.61 10-yr, 24-hr 4.80 0.49 1,468 2.99 25-yr, 24-h r 6.20 0.69 2,097 4.28 100-yr, 24-hr 8.90 1.09 3,354 6.84 Proposed—N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 71 Events for Reach 1 R: DP-1 - Lake Cochichewick Event Inflow Outflow Elevation Storage (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-h r 0.74 0.74 0.00 0 10-yr, 24-h r 1.58 1.58 0.00 0 25-yr, 24-h r 3.17 3.17 0.00 0 100-yr, 24-hr 6.44 6.44 0.00 0 Proposed—N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 72 Events for Reach 3R: Rip-Rap Swale Event Inflow Outflow Elevation Storage (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-h r 0.00 0.00 116.50 0 10-yr, 24-h r 0.41 0.41 116.65 3 25-yr, 24-h r 1.34 1.34 116.78 7 100-yr, 24-hr 2.63 2.62 116.89 11 Proposed—N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 73 Events for Pond 1 P: Bio. Ret. Area #2 Event Inflow Outflow Discarded Primary Elevation Storage (cfs) (cfs) (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-hr 0.41 0.03 0.00 0.03 116.51 745 10-yr, 24-h r 0.78 0.54 0.00 0.54 116.59 821 25-yr, 24-h r 1.11 1.05 0.00 1.05 116.64 871 100-yr, 24-hr 1.75 1.68 0.01 1.68 116.69 923 Proposed—N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 74 Events for Pond 2P: Bio. Ret. Area #1 Event Inflow Outflow Discarded Primary Elevation Storage (cfs) (cfs) (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-h r 0.26 0.01 0.00 0.00 116.50 887 10-yr, 24-h r 0.90 0.41 0.01 0.41 116.65 1,038 25-yr, 24-h r 1.72 1.35 0.01 1.34 116.78 1,176 100-yr, 24-hr 2.74 2.63 0.01 2.63 116.89 15298 Proposed—N. Andover Boat Launch_revSept2024 Multi-Event Tables Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC Page 75 Events for Pond 5P: 12" RCP Event Inflow Primary Elevation Storage (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-hr 0.03 0.03 116.50 0 10-yr, 24-h r 0.54 0.54 116.53 0 25-yr, 24-h r 1.05 1.05 116.59 0 100-yr, 24-hr 1.68 1.68 116.70 0 Proposed—N. Andover Boat Launch_revSept2024 Table of Contents Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC TABLE OF CONTENTS Promect Reports 1 Routing Diagram 2 Rainfall Events Listing 3 Area Listing (all nodes) 4 Soil Listing (all nodes) 5 Ground Covers (all nodes) 6 Pipe Listing (all nodes) 2-yr, 24-hr Event 7 Node Listing 8 Subcat 1 S: SC-01 9 Subcat 2S: SC-02 11 Subcat 3S: SC-03 13 Subcat 4S: SC-04 15 Reach 1 R: DP-1 - Lake Cochichewick 16 Reach 3R: Rip-Rap Swale 17 Pond 1 P: Bio. Ret. Area#2 19 Pond 2P: Bio. Ret. Area#1 21 Pond 5P: 12" RCP 10-yr, 24-hr Event 22 Node Listing 23 Subcat 1 S: SC-01 24 Subcat 2S: SC-02 26 Subcat 3S: SC-03 28 Subcat 4S: SC-04 30 Reach 1 R: DP-1 - Lake Cochichewick 31 Reach 3R: Rip-Rap Swale 32 Pond 1 P: Bio. Ret. Area#2 34 Pond 2P: Bio. Ret. Area#1 36 Pond 5P: 12" RCP 25-yr, 24-hr Event 37 Node Listing 38 Subcat 1 S: SC-01 39 Subcat 2S: SC-02 41 Subcat 3S: SC-03 43 Subcat 4S: SC-04 45 Reach 1 R: DP-1 - Lake Cochichewick 46 Reach 3R: Rip-Rap Swale 47 Pond 1 P: Bio. Ret. Area#2 49 Pond 2P: Bio. Ret. Area#1 51 Pond 5P: 12" RCP 100-yr, 24-hr Event 52 Node Listing 53 Subcat 1 S: SC-01 54 Subcat 2S: SC-02 56 Subcat 3S: SC-03 58 Subcat 4S: SC-04 Proposed—N. Andover Boat Launch_revSept2024 Table of Contents Prepared by Apex Companies Printed 9/11/2024 HydroCAD® 10.20-5a s/n 04044 ©2023 HydroCAD Software Solutions LLC 60 Reach 1 R: DP-1 - Lake Cochichewick 61 Reach 3R: Rip-Rap Swale 62 Pond 1 P: Bio. Ret. Area#2 64 Pond 2P: Bio. Ret. Area#1 66 Pond 5P: 12" RCP Multi-Event Tables 67 Subcat 1 S: SC-01 68 Subcat 2S: SC-02 69 Subcat 3S: SC-03 70 Subcat 4S: SC-04 71 Reach 1 R: DP-1 - Lake Cochichewick 72 Reach 3R: Rip-Rap Swale 73 Pond 1 P: Bio. Ret. Area#2 74 Pond 2P: Bio. Ret. Area#1 75 Pond 5P: 12" RCP A..........Iuuuuu� ..........16 ..............111,13 1\4 L.,o c atio ri M a PNGfc V\S��0?6 rBENCHMARKI -7— P REUSE CLEAN BOULDERS 5'X5'RIP RAP FROM RETAINING WALL. SPLASH PAD DOUBLE SWING GATE SS SIG REMOVE AND RESET GUARDRAIL REMOVE AND NATIVE TREE(TYP.) 25 RESET MW COVER RESET GUY WIRE 25-25-25— BIORETENTION 5 N AREA NO.1 BIORETENTION AREA NO.2 "'d JfA ................. I I-I FZ FZ Z F1 FZ Fz FZ 'Z FZ FZ 44 1j, RIPRAP-LINE, SWALEF- NATIVE ONE WAY SIGN 18.0' BENCHMARK SIGN PLANTINGS MIN.5'(TYP.) IG BOAT RACKS (6)8'X20-BOAT RACK tt PARKING ON Co- +++,+ 9 RESET MW COVER -2- BOAT RACK Q(2)12'X20 %4- RESET MW C RR Z 2r,�25--�25_1 8'WIDE BOAT LAUNCH WITH dit- --'ONE WAY N 2 25 O,,,STURB ZONE "NO TRAILER ACCESS"SIGN 4- REVETMENT(SEE DETAIL SIGN .------ 25'NO SHEET CD-5) (2)LOCKING BOLLARDS Li ++ MIN.8'(TY P.) TRASH AND RECYCLING 3.6 4-; -R36.0- RECEPTACLES R54 0' VV- -f-+ONEWAYSIGN—J-A C"-2- ---OH' - -T--T- OHW ONVV 3 2- 7 + 41 8'WIDE STONE FILLED PERMEABLE PAVER BOAT LAUNCH WITH 12% 25 SLOPE(SEE DETAIL SHEET CD-5) TREES SIGN"HANDICAP NATIVE ES —————— (TYP.) RESET EXISTING -��l PARKING" WOOD POST WITH ,0 E ROPED FENCING KIOS MSE BLOCK WALL 4 (SEE DETAIL SHEET CD-5) ——————————————— BENCHMARK REMOVE AND REPLACE SPIKE FENCING(TYP.) EXISTING STONE ROCK BANK BENCHMARK ALONG FACE OF WALL SPIKE ELEV=109.32' LEGEND IA GRAVEL FILLED PAVERS GRASS FILLED PAVERS G! BIORETENTION AREA REVETMENT RIP RAP A FLARED END STRUCTURE PLANOVERFLOW STRUCTURE SCALE:1 20' Scale 11. 20' NORTH LAKE COCHICHEWICK BOAT LAUNCH Date JULY 2024 ENVIRONMENTAL Sheet No. "07 Job No. 22003302 TOWN OF NORTH ANDOVER,MA o Designed by JLV THIS LINE IS ONE INCH < LONG WHEN PLOTTED AT PARTNERS 3 Drawn by AES FULL SCALE ON A 22"X G FI . 1 Checked by RJP 34"DRAWING BMP LOCATION MAP An '.npxC--oMMa,,.v r- J MARK DATE DESCRIPTION Approved by RJP