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HomeMy WebLinkAbout2018-11-13 Stormwater Peer Review CHRISTIANSEN & SERGI CS A DIVISION OF THE MORIN CAMERON GROUP PROFESSIONAL ENGINEERS AND LAND SURVEYORS 160 SUMMER STREET,HAVERHIL€-, IOA t118:30 1ei: 978-373-0310 fax 978-372-3,360 August 3, 2018 Jean Enright Planning Director Town of North Andover Planning Department 120 Main Street North Andover, MA 01845 RE: Stormwater Review Improvement of Rea Street Dear Ms. Enright: We offer the following responses to comments received in a review letter of July 18, 2018 by SSV. General 1. The Site Evaluation Statement was provided. The waiver request was erroneous and has been removed, 2. The outlet pipes are required to the overflows. The outlet pipes have been shortened where possible based on the minimum pipe slope to accommodate the required overflows. The rain garden has been removed from the riverfront area. 3. The proposed dwelling is located more than 100' from Mosquito Brook. 4. A revised alternatives analysis will be provided for review during the Notice of Intent approval process. The rain garden has been removed from the riverfront area. 5. It is not feasible nor standard engineering practice to provide stormwater infiltration areas within the R.O.W. The swales and infiltration areas are to be maintained by the Homeowners, The proposed catch basin and water quality unit are located within the R.O.W. Stormwater Review 1. No response required. I A DIVISION OF THE MORIN CAMERON GROUP CS, PROFESSIONAL ENGINEERS AND LAND SURVEYORS 160 SUMMER STREET,HAVERHILL, MA 018,30 tel: 978-373-0310 vmvm csi-en9r.cont fax 978-372-3960 3. The Rain Garden and associated grassed swale were removed. A catchbasin was added at the low point of Rea Street. A water quality unit is proposed to treat the runoff before flowing into an existing retention basin., Very truly yours Stephen Sawyer, P.E. CMS1 A DIVISION OF THE MORIN CAMERON GROUP PROFESSIONAL ENGINEERS AND LAND SURVEYORS 160 SUMMER STREET,HAVERHILL, NIA 01830 tel:978-,M-0310 wwmcsi-engr.com fax 978.372.3960 2. a. One Design Point was used for Pre and Post construction calculations. It is typical that the over-all drainage area from the existing drainage is divided up into smaller sub-catchment areas for the proposed conditions. This is required to route the newly created impervious surfaces to the proposed drainage mitigation features. The total of the proposed sub-catchment areas is equal to the original drainage area of the existing conditions. The design point for this project is at the culverts located at the crossing under Rea Street, This design point is the same for both the existing and proposed conditions. A reach was provided for each subcatchment to accurately model the flow path and time associated with each subcatchment prior to reaching the common design point. b. Runoff from the driveways will flow overland into the grassed channel for treatment and flow into the nitration areas. Roof runoff will be piped from gutter to the grasses Swale and into infiltration areas. The roofs of lots b & 7 will be piped to smaller infiltration chamber systems on each property. c. Crushed stone has been added at the beginning of each grassed channel. 3. a. The area of impervious and the Required Recharge Volume have been revised. The areas have been broken down as requested in HydroCAD. b. Infiltration tests are not required under the DEP Stormwater Management Handbook. It is industry standard to use the soil texture/type frorn the onsite soil testing and then using the Rawls Table to determine infiltration rates. DEP does allow the use of double ring infiltrometer to determine infiltration rates. We have found those rates to be much faster than those dictated within the Rawls Table. Soil evaluations were performed on site to confirm the sandy Hydrologic soil group A soils. 4. a. No response required. b. The grass channels are used as pretreatment for the infiltration areas. DEP Stormwater Standards indicate 80%TSS removal for Infiltration Basins. To receive the 80% TSS removal the infiltration areas require adequate pretreatment. If the grass channel and infiltration areas were combined, more TSS is being removed than actual conditions. The calculation e. A sediment forebay has been added to the grassed channel to meet the requirement to receive 50%TSS removal. This is applied only to meet the 44% pre-treatment requirements needed prior to directing stormwater to the infiltration basins. A DIVISION OF THE MORIN CAMERON GROUP ctsPROFESSIONAL. ENGINEERS AND LAND SURVEYORS 160 SUMMER STREET, HAVERHILL, MA 01830 tel: 978-373-0310 vmvl.cs 1-011y,ca n I fax 978-372-3960 5. No response required 6. No response required 7. No response required 8. a. No response required. b. It is our opinion that installing the construction entrance during the installation of the siltation controls is impractical. The site it completely wooded, and trees will need to be removed within the construction entrance areas. Clearing, grubbing and grading will need to occur in the area of the construction entrance and will result in numerous replacements of the crushed stone. Upon clearing and grubbing at the entrances the stabilized entrance will be installed. c. The location of the construction entrances at either end of Rea Street have been added to the plan. Site plans for each lot will be provided prior to obtaining a building permit. The site plans will include construction entrances for each lot. d. Siltation controls have been provided around each stockpile area. c. The grassed channels and collection areas are intended to be used as sediment basins during construction. 9. The o & M has been updated to list the Homeowner's Association as the responsible party for the grass channels and infiltration areas. 10. No response required. Wetlands Review All comments concerning wetlands regulations will be resolved with the Conservation Commission and its agent during the Notice of Intent process. Additional Revisions 1. The infiltration basins were redesigned as subsurface infiltration areas. 2. A stone trench drain was added along the north side of Rea Street to reduce the amount of runoff flowing across Rea Street. CHRISTIANSEN & SERGI PROFESSIONAL DIVISION or /T��a-�E Of�IN �Cj�p4�1� RCp" N GROUP CSS PROFE . IONAL. ENGINEERS AND LAND SURVEYORS ORS 160 SUMMER STREET,HAVERHILL,MA 01830 tel:978-373-0310 www.csi-engF.COM fax 978-372-3960 September 18, 2018 ,lean Enright Planning Director Town of North Andover Planning Department 120 Main Street North Andover, MA 01845 RE: Stormwater Review Improvement of Rea Street Dear Ms. Enright: We offer the fallowing responses to comments received in a review letter of August 17, 2018 by SSV. General 1. Comment Resolved. 2. These items will be handled during the Notice of Intent process with the Conservation Commission. 3. This item will be handled during the Notice of Intent process with the Conservation Commission. 4. This item will be handled during the Notice of Intent process with the Conservation Commission. 5. The drainage system has been substantially changed and will be reviewed by the Town Engineer.. Stormwater Review 1. No response required. 2. a, One Design Point was used for Pre and Post construction calculations. It is typical that the over-all drainage area from the existing drainage is divided up into smaller sub-catchment areas for the proposed conditions. This is required to route the newly created impervious surfaces to the proposed drainage mitigation features. The total of the proposed sub-catchment areas is equal to the original i f A DIVISION OF THE MORIN CAMERON GROUP CS PROFESSIONAL AL ENGINEERS,AND LAND SURVEYORS 160 SUMMER STREET, HAVERHILL,MA 01830 tel:978-373-0310 www.csi-engr.com fax 978-372-3960 drainage area of the existing conditions. The design point for this project is at the culverts located at the crossing under Rea Street. This design point is the same for both the existing and proposed conditions. A reach was provided for each subcatchment to accurately model the flow path and time associated with each subcatchment prior to reaching the common design point. b. Catch basins are now proposed, c. No response required. 3. a. No response required, b. No response required. 4. a. No response required. b. TSS removal worksheets have been revised for the new drainage design. c. No response required. 5. No response required 6. No response required 7. No response required 8, a. No response required. b. No response required. c. No response required, d. No response required. e. The grassed channels are no longer proposed. 9. No response required. 10. No response required. CSCHRISTIANSEN A DIVISION OF THE MORIN CAM RON GROUP PROFESSIONAL ENGINEERS AND LAND SURVEYORS 160 SUMMER STREET,HAVERHILL,MA 01830 Lek 978.373-0310 www.csi•engr.com fax 978-372-3960 i Wetlands Review All comments concerning wetlands regulations will be resolved with the Conservation Commission and its agent during the Notice of Intent process. Additional Revisions 1. Only two infiltration areas are now proposed. All runoff from the proposed roadway will be collected using catch basins and directed into the infiltration areas. Contech CDS units are proposed to treat the runoff from the impervious areas. Very truly yours Q1 Stephen Sawyer, P.E. CHRISTIANSEN & SERGI A 01VIS/0N 01--, 1"HE MOOIN CAMERON GHOUF' P,/-Jk0FESS/ONA1. ENGINEERS AND I-AND SURVEYORS 160 11 S 0 H"T. I OWE-RH ILI,, MA OHM tO: T(:1-373 W10 9/8 3(2-2,060 September 28, 2018 Jean Enright Planning Director Town of North Andover Planning Department 120 Main Street North Andover, MA 01845 RE- Stormwater Review Improvement of Rea Street Dear Ms. Enright: We offer the following responses to comments received in a review letter of September 24, 2018 by SSV. General 5c. The ownership of the drainage system will be reviewed by the Town Engineer. Stormwater Review 2a. The area of the Post Development analysis now matches the Pre- Development analysis. 2b. The roof drywell on Lot I has been moved as requested. All driveways are to be directed towards the proposed drainage system. Spot grades have been provided for each driveway to ensure they drain towards the drainage system. The infiltration areas are within drainage casements that are labeled on Sheets 5 and 6 and dimensions are shown on sheet 2. 3c. The water quality units are designed to treat the required water quality volume. 9c. A. The ownership of the drainage system will be reviewed by the Town Engineer. Wetlands Review CSCHRISTIANSEN & SERGI A 1.)WISI(Ol Of` 71,1E MORIN CAME-.'ORON GF�OUI-) r',aoreSSIONAL, IMO 1,AND SORVEYOnS I, I INA..'PHILL, (MA GI 31M 918,V), 0:M 1;ax 9 N-3 11"'-T?G0 All comments concerning wetlands regulations will be resolved with the Conservation Commission and its agent during the Notice of Intent process, Additional Revisions 1 The walking path is just proposed as a cleared path through the wooded area which will be created during the installation of underground utilities. 2. The roof drywell on Lot I has been relocated as requested. 3. The drainage easements are dimensioned on Sheet 2. 4. A detail for the stone trench drain has been provided, S. The type, length, and slope of the pipe has been provided. The runoff collected by the trench is from woods and the stone trench drain will prevent sediment from entering the pipe. The need for a cleanout or structure is unnecessary for this application, 6. Runoff from all the proposed driveways is directed towards the drainage system, Spot grades have been provided for each driveway. 7. The outlet pipe from Infiltration Area 2 has been removed from the 50' Buffer. 8. The pump station design will be submitted for approval by the town, The design of the sewer pump station will not impact the stormwater calculations, 9. Specific details and models were provided for each water quality unit. Very truly yours Stephen Sawyer, P.E. i I CHRIS TIA NSEN & SE R GI A DIVISION OF THE MORIN CAMERON GROUP PROFESSIONAL ENGINEERS AND LAND SURVEYORS 160 SUMMER STREET,HAVERHILL, MA 01830 tel:978-373-0310 www,csl-engr.ccm fax 978-372-3960 September 28, 2018 Jean Enright Planning Director Town of North Andover Planning Department 120 Main Street North Andover, MA 01845 RE: Stormwater Review Improvement of Rea Street Dear Ms. Enright: We offer the following responses to continents received in a review letter of September 24, 2018 by S S V. General 5c. The ownership of the drainage system will be reviewed by the Town Engineer. Stormwater Review 2a. The area of the Post Development analysis now matches the Pre- Development analysis. 2b. The roof drywell on Lot 1 has been moved as requested. All driveways are to be directed towards the proposed drainage system. Spot grades have been provided for each driveway to ensure they drain towards the drainage system. The infiltration areas are within drainage casements that are labeled on Sheets 5 and b and dimensions are shown on sheet 2. 3c. The water quality units are designed to treat the required water quality volume. 9c. A. The ownership of the drainage system will be reviewed by the Town Engineer, Wetlands Review I CF►R►S TIA NSEN & SERG► A DIVISION OF THE MORIN CAMERON GROUP PROFESSIONAL ENGINEERS AND LAND SURVEYORS 160 SUMMER STREET,HAVERHILL,MA 01830 tel:978-373-0310 www.csi-engr.com fax 978-372-3960 All comments concerning wetlands regulations will be resolved with the Conservation Commission and its agent during the Notice of Intent process. Additional Revisions I. The walking path is just proposed as a cleared path through the wooded area which will be created during the installation of underground utilities. 2. The roof drywell on Lot 1 has been relocated as requested. 3. The drainage easements are dimensioned on Sheet 2. 4. A detail for the stone trench drain has been provided. 5. The type, length, and slope of the pipe has been provided. The runoff collected by the trench is from woods and the stone trench drain will prevent sediment from entering the pipe. The need for a cleanout or structure is unnecessary for this application. 6, Runoff from all the proposed driveways is directed towards the drainage system. Spot grades have been provided for each driveway. 7. The outlet pipe from Infiltration Area 2 has been removed from the 50' Buffer. 8. The pump station design will be submitted for approval by the town. Tile design of the sewer pump station will not iiiipact the stormwater calculations. 9. Specific details and models were provided for each water quality unit, Very truly yours Stephen Sawyer,P.E. i A DIVISION OF THE MORIN CAMERON GROUP CS PROFESSIONAL ENGINEERS ARID LAND SURVEYORS 160 SUMMER STREET,HAVERHILL,MA 01830 tel:978-373.0310 mm.cs€-enguom fax 978-372-3960 i 4 October 17, 2018 Jean Enright Planning Director Town of North Andover Planning Department 120 Main Street North Andover, MA 01845 RE: DPW Review Improvement of Rea Street Dear Ms. Enright: We offer the following responses to comments received in a review letter of October 15, 2018 by the Town of North Andover DPW. 1. The top of stone has been revised to 170.23. 2. The Homeowner's Association will be responsible for the maintenance of the stormwater structures located outside the R.O.W. 3. The drainage pipes have been revised to be reinforced concrete pipe. 4. Gate valves have been proposed at each end of the water main connections. 5. SMH 4 has been relocated as requested. 6. A note has been added to Sheet 6. 7. The proposed street trees along the northern side of Rea Street have been removed. The proposed street trees on the southern side of Rea Street have been moved out of the R.O.W, to be consistent with the subdivision road detail. Very truly yours, Stephen Sawyer, P.E. h CHRISTIANSEN & SERGI A DIVISION OF THE MORIN CAM'ERON GROUP PROFESSIONAL ENGINEERS AND LAND SURVEYORS 160 SUMMER STREET,HAVERHILL,MA 01030 tel:978-373-0310 wwwmi-engr.eom fox 978-372-3960 6 November 1,2018 Jean Enright Planning Director Town of North Andover Planning Department 120 Main Street North Andover,MA 01845 RE: Stormwater Review Improvement of Rea Street Dear Ms.Enright: We offer the following responses to comments received in a review letter of October 22, 2018 by SSV. General 5d. The Town will own the drainage system within the R.O.W. and the HOA will own the drainage structures located outside of the R.O.W. This was discussed with the Town Engineer and can be conditioned. Stormwater_Review 2D.a. The latest revised plan and Stormwater packet that were sent to you October 22, 2018 and dated October 17,2018 address this comment, The runoff from Pd is directed into the existing basin located to the north of Rea Street, The existing basin was modeled in HydroCAD. The basin discharges downstream of proposed conditions versus existing conditions. b. The'Town will own the drainage system within the R,O,W, and the HOA will own the drainage structures located outside of the R.O.W. This was discussed with the Town Engineer and can be conditioned. Very truly yours Stephen Sawyer, P.E. SSV ENGINtiliIUNG INC. 609 Winter Street Framingham,MA 01702 Phone: 508-745-4077 April 25, 2018 Ms. Jean Enright, Planning Director Planning Department 120 Main Street North Andover,MA 01845 Ms. Jennifer Hughes, Conservation Administrator Conservation Department 120 Main Street North Andover,MA 01845 RE: Stormwater Review Comments #1 Improvement of Rea Street Dear Ms. Enright and Ms. Hughes: Per your request I have conducted a stormwater technical review of the proposed Definitive Subdivision Plan for Improvement of Rea Street in North Andover. The applicant is proposing to construct a 1,304 foot long residential roadway and seven (7) new single-family house lots. Included in the materials I received and reviewed were the following documents: 1. Form C -Application for Definitive Subdivision Approval 2, Definitive Subdivision Plan for "Improvement of Rae Street" prepared by Christiansen & Sergi, lnc.dated June 11, 2018 and revised June 26, 2018. 3. Stormwater Management Report prepared by Christiansen & Sergi, Inc,dated June 11, 2018 and revised June 26, 2018. Attachment to this report include the "Pollution Prevention and Operations and Maintenance Plan for construction and post construction phase. My comments on the proposed project are outlined below: General 1. The applicant is requesting a waiver front the Environmental and Community Impact Statement under Section 5.1.5 of Forth C stating that only 5 new lots are proposed with 1 lot that exists already. However; the plans and the stormwater management report show a total of seven (7) lots, The applicant should clarify the number of lots and revise/update all material ssyGG INC, 609 Winter Street Framingham.MA 01702 Phone:508-745-4077 accordingly to be consistent. Storm-water Review -MADEP Checklist for Stormwater Report 1. Standard I states that no ne►v stortnwater conveyances may discharge untreated stortnwater directly to or cause erosion in wetlands of the Coln tttonwealth. The project proposes six(6)new outfall discharges alongside Mosquito Brook. It appears that stormwater is routed through infiltration basins prior to discharge through the new outfalls. It appears that Standard 1 is met; however, the Applicant should further address this as noted in my comments under Standards 2 and 4 below. 2. Standard 2 requires Heat post-development rent off does not exceed pre-development runoff off-site. a. The Applicant has analyzed one (1) design point(DP)under existing conditions and seven (7)undo proposed conditions within the project limits. Typically, the number of DPs and their locations match under the existing and proposed conditions to demonstrate that the proposed project results in net decrease in peals flows over the existing conditions. It is likely that the proposed project may meet this Standard given the proposed infiltration systems;however, the applicant should revise the HydroCAD modeling to match the DPs. b. The applicant should provide details on the Plan Set to show how runoff from roofs and driveways is conveyed to the infiltration systems, c. Runoff from Rae Street appears to be directed to the proposed grassed channel. Additional details must be provided in the Plan Set for placing stone to limit erosion and also capture debris and sediment as runoff from Rae Street enters the grassed channels. 3. Standard 3 requires that the anttrral recharge front post-developtttettt shall approximate annual recharge front pre-development conditions. a. The Applicant has provided Groundwater Recharge calculations that are included in the Stormwater Management Report. The Applicant has calculated the required recharge i E I S IV L:NGINFI311ING INC. 609 Winter Street Frantitighain.MA.01702 Phone; 508-745-4077 volume utilizing HSG A soils and 1.11 acres as the proposed impervious pavement and rooftop area. The HydroCAD report indicates a total impervious paved parking area of 1,284 acres and no rooftop area is listed. The Applicant should clarify the total new impervious area with a breakdown of Rae Street paved area,paved areas of the driveways to the lots and rooftop areas and revise/update the HydroCAD modeling accordingly. b. To further verify that the proposed development is in compliance with Standard 3, the Applicant must conduct infiltration tests to confirm the assumed infiltration rate of 8.27 in/hr. 4. Standard 4 requires that the storinwater system be designed to remove 80% Total Suspended Solids (TSS) and to treat 0.5-inch or 1.0-inch of volutne from the impervious area for water quality. a) The Applicant has provided water quality volume calculations that are included in the Stormwater Management Report. The Applicant has calculated the required water quality volume by multiplying the impervious area by 1.0 inch of runoff per Volume 3, Chapter 1,page 32 of the Massachusetts Stormwater Handbook. b) The Applicant must revise the TSS removal calculation worksheets to depict the proposed treatment train that combines the grass channel and infiltration system. c) The Applicant is seeking a TSS removal of 50% for the proposed grassed channel. In accordance with Volume 2, Chapter 2, page 73 of the Massachusetts Stormwater Handbook, a sediment forebay or equivalent inust be provided in order to take the 50% TSS removal credit. The Plan Set should be updated to include details for sediment bay or equivalent. 5. Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads (LUHPPL). a) Standard 5 is not applicable to this site. 6. Standard 6 is related to projects with storm water discharging into a critical area, a Zone H or an Interim Wellhead Protection Area of a public water supply. a) Standard 6 is not applicable to this site. I:N(;IRKIiItINU INC:. 609 Winter Street Framingham.MA 01702 Phone:508-745-4077 7, Standard 7 is relrited to projects considered Redeveloprttertt. a) Standard 7 is not applicable as the proposed project is new development. 8. Standard 8 requires a plan to control construction related impacts including erosion, sedimentation or other pollutant sources. a) The Applicant has acknowledged that a Storinwater Pollution Prevention Plan (SWPPP) will be prepared in accordance with the EPA Construction General Permit requirements for projects disturbing more than one acre of land. I recommend that the Conservation Commission consider including a Special Condition requiring the Applicant to provide the SWPPP to the Town a minimum of ld days prior to any land disturbance, b) The construction sequence prepared by the Applicant indicates that the crushed stone construction entrance will be installed after the trees have been cut and grubbing of the site is commenced/completed. I recommend that the construction entrances must be installed as part of the sedimentation control of the whole site prior to any activities on- site. The construction sequence must be revised accordingly. c) Sheet 9 of 12 of the Plan Set should indicate the anticipated location(s) of the crushed stone construction entrance for Rae Street construction and at each lot following construction of Rae Street so that the construction contractor knows of this requirement, d) I recommend that sedimentation control barrier must be installed around the temporary earth stockpile areas. This should be added to the Plan Set. e) The Applicant must clarify if the infiltration basins on the individual lots will be utilized as temporary sediment basins during construction. I would recommend that temporary sediment basins during construction cannot be placed at the same location as the proposed infiltration basins. 9. Standard 9 requires a Long Term Operation and Maintenance (O&M)Plan to be provided. a) The Applicant has provided a Pollution•Prevention and.Operation and.Maintenance (O &M)Pik ri that is included in the Stormwater Management Report. The Applicant indicates that ultimately the Town will take ownership of the storm.water'management system components'that lie both within Rae Street R-O-W and proposed drainage easements..In my opinion this is not a standard practice given that the stormwater V toE.N6tN. LliIt Nis INC, 609 Winter Street Framingham.MA 0 702 Phone: 508-745-4077 a systems are small and service priniarhy individual lots. Individual lot owners should take ownership of the stortnwater syste ins within them property and the Town can j take ownership of systems within the Rae Street R-O-W: b) 10. Standard 10 requires an Illicit Discharge Compliance Statement to be provided a) The Applicant appears to be in compliance with Standard 10. I would be happy to meet with you and the Applicant to review these comments at your convenience, Please feel free to contact me if you or the applicants have any questions regarding the issues addressed herein. Vet truly yours, Saar Bade President j i 5 Page i I I SS'V ENGINFERING INC, 609 Winter Street Framingham.MA 01702 Phone,508-745-4077 August 17, 2018 Ms. Jean Enright,Planning Director Planning Department 120 Main Street North Andover, MA 01845 Ms. Jennifer Hughes, Conservation Administrator Conservation Department 120 Main Street North Andover, MA 01845 RE: Stormwater Review Comments##2 Impl•ovement of Rea Street Dear Ms. Enright and Ms. Hughes: This letter memorandum summarizes review of the supplemental information submitted by Christiansen & Sergi to provide responses to my review continents letter dated July 18, 201& Inchided in the materials I received and reviewed were the following: ➢ Response to comments letter dated August 3, 2018, and prepared by Christiansen & Sergi. ➢ Definitive Subdivision Plan for "Improvement of Rae Street" prepared by Christiansen &Sergi, Inc. dated June 11, 2018 and revised July 31, 2018. ➢ Stormwater Management Report prepared by Christiansen & Sergi, Inc. dated June 11, 2018 and revised July 31, 2018. Please note that a revised Notice of Intent Application and related material have not been submitted at the time of this review. 1 .. too 8NCIN''iiliitINU INC. 609 Winter Street Franftgham.M.A.01702 Pho=509-745-4077 My supplemental comments are outlined below with the suffix "B" to my original comment number: General 113. The applicant states that the waiver request for the Site Evaluation Statement was erroneous and a Statement has been provided. No further comment 213. The applicant states that the proposed outlet pipes have been shortened where possible based on the minimum pipe slope and the rain garden has been removed from the riverfront area. The NACC Wetland Protection Regulations (Amended 3/23/16) states in part: "StormSvater structures and/or discharge may be allowed in the 50-foot No-Build Zone when no other feasible location exists or when it is necessary to maintain the hydrology of the resource.An alternatives analysis showing the net benefit of locating the structure in the No-Build Zone is required." Per the above requirement the Applicant must provide this alternatives analysis for structures proposed within the 50-ffot No-Build Zone. 3B. The applicant states that proposed dwelling on Lot 7 is located more than 100' from Mosquito Brook. This will be further reviewed upon the applicant's submission of a detailed alternatives analysis under the Rivers Protection Act. 413. The applicant states that a revised Alternatives Analysis would be provided for review during the Notice of Intent approval process. This will be reviewed upon receipt of revised NOI from the applicant. 513. The Applicant must coordinate with the Town Engineer to review the proposed mnoff treatment and management from Rae Street on private properties with drainage easements, Typically stormdrain system is located within street R-O-W with infiltration systems on individual lots for roof and driveway runoff only. i I SSV' IiNGINEERING INC.. 609 Winter Street Framingham.MA 01702 Phone; 508-745-4077 Stormwater Review - MADEP Checklist for Stormwater Report IB. Standard 1 states that no ne►v storrnwater conveyances may discharge untreated storntwater directly to or cause erosion in wetlands of the Contntonwealth. This Standard is met. No additional comment. 2B. Standard 2 requires thatpost-development runoff does not exceed pre-development runoff off-site. a. The Applicant has analyzed one (1) design point(DP)under existing conditions and seven (7)under proposed conditions within the project limits. Typically, the number of DPs and their locations match under the existing and proposed conditions to demonstrate that the proposed project results in net decrease in peak flows over the existing conditions.It is likely that the proposed project may meet this Standard given the proposed infiltration systems; however, the applicant should revise the HydroCAD modeling to match the DPs. This comment still stands. The total drainage area does not match between the existing and proposed conditions HydroCAD model inputs. Proposed subcatehment "PG'" is shown with a new outfall and does not discharge to the "Design Point". The existing storm drainage system at the North Cross Road intersection is shown; however, it is not clear if there is an existing outfall discharge for this drainage system. b. The applicant should provide details on the Plan Set to show how runoff from roofs and driveways is conveyed to the infiltration systems. The revised plan set shows that runoff from Rea Street will be conveyed to the proposed infiltration areas using "Rectangular Under Walk Drainage Pipe". Additional construction details and description may be required to show how flow from Rea Street will be routed to this drainage pipe along the granite curbing and avoid flow skipping downstream along Rea Street. c. Runoff from Rae Street appears to be directed to the proposed grassed channel. Additional details must be provided in the Plan Set for placing stone to limit erosion and also capture debris and sediment as runoff from Rae Street enters the grassed channels. Crushed stone has been added.No additional comment. 8SV* IiNGIi EEIRINti INC, 609 Winter Street Framingham.MA 01702 Phone: 508-745-4077 3B. Standard 3 requires that the annual recharge fi•orsr post-developrt:errt shall approximate annual recharge from pre-development conditions. a. The area of imperviousness and the required recharge volume has been revised and updated. No additional comment. b. No additional comment. 4B. standard 4 requires that the storm water system be designed to remove 80% Total Suspended Solids (TSS) and to treat 0.5-inch or I.0-inch of voltinie fr-oin the impervious area for water quality. a. No additional comment. b. The revised TSS removal calculations still does not combine the grass channel followed by infiltration system; however, it appears that 90% TSS Removal is achieved. No further comment. c. A,sediment forebay has been added to the grassed channel to receive 50% TSS removal. No further comment. 5B. Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads (L UHPPL). a. Standard 5 is not applicable to this site. 6B. Standard G is related to projects with storttiwttter discharging itxto a critical area, a Zone Hop an Interim Wellhead Protection Area of a public water supply. a. Standard b is not applicable to this site. 7B. Standard 7 is related to projects considered Redevelopment. a. Standard is not applicable as the proposed project is new development. I,NCAh'liiiltING INC. 609 Whiter street Framingham.MA 01702 Phone: 509-745-4077 8B. Standard 8 requires a plan to control construction related impacts including erosion, sedimentation or other pollutant sources. a. The Applicant has acknowledged that a Storrnwater Pollution Prevention Plan(SWPPP) will be prepared in accordance with the EPA Construction General Pert-nit requirements for projects disturbing more than one acre of land. I recommend that the Conservation Commission consider including a Special Condition requiring the Applicant to provide the SWPPP to the Town a minimum of 14 days prior to any land disturbance. b. The construction sequence prepared by the Applicant indicates that the crushed stone construction entrance will be installed after the trees have been cut and grubbing of the site is connnenced/completed. The applicant states that clearing, grubbing and grading will be needed prior to installation of stabilized construction entrance. A special condition could be added to state that the stabilized construction entrances be installed immediately following the clearing and grubbing. No further comment. c. No further comment. d. Siltation controls have been added around each soil stockpile area.No further comment. e. The Applicant states that the grassed channels will be used as sediment basins during construction.A special condition could be added to state that sediment captured in the grassed channels during construction will be removed and the channels will be graded with appropriate stabilization methods following completion of construction. 9B. Standard 9 requires a Long Teri Operation and Maintenance (O&MJ Plan to Ise provided a,` Tire Applicant states that the Homeowner's Association would be the responsible party for the proposed grassed channels and infiltration areas. The Board could discuss this itein and decide if it wants the individual homeowner to be the responsible party or the Homeowner's Association. ssyLNGIN�f RAUNG INC;. 609 Winter Street Framingham.MA 01702 Phone: 508-745-4077 10,8. Standard 10 requires an_Illicit Discharge Compliance Statement to be provider. a. The Applicant appears to be in compliance with Standard 10. No further comment. Wetlands Review The Applicant states the following: "All comments concerning wetlands regulations will be resolved with the Conservation Commission and its agent during the Notice of Intent Process." A review of the Notice of Intent submission will be completed upon receipt. Below are the preliminary comments from my review based on the initial submission: 1. Following are the overall comments based on the current documentation: a. The wetland flags shown on the Plan Set appear to be incomplete as they do not extent to at least the limits of the project and beyond, b. The Plan Set must show the centerline and the banks of Mosquito Brook and provide a description of how it was established and confirmed. c. The 100-year Floodplain shown on the Plan Set appears to be erroneous as it does not seem to follow an elevation. Also, the wetland flags are located above the floodplain, A description of how the floodplain was determined and established must be provided. d. It appears that there is beaver activity along Mosquito Brook. A description of how the applicant is proposing to manage this issue during construction and post-construction must be provided. e. The Applicant must provide a description a detailed description of how the proposed project complies with the Rivers Protection Act, 6 Page I �P a IiNGINEERING INC. to 609 Winter Street Framingham,MA 01702 Phone: 508-745-4077 i I would be happy to meet with you and the Applicant to review these comments at your convenience. Please feel free to contact me if you or the applicants have any questions regarding the issues addressed herein, Very truly yours, F� Sane Bade President 7 Page i i SS'V ENGINEERING INC. 609 Winter Street 1 Framingham.MA 01702 Phone: 509-745-4077 July 18,2018 I I Ms, Jean Enright,Planning Director Planning Department 120 Main Street North Andover, MA 01845 Ms. Jennifer Hughes, Conservation Administrator Conservation Department 120 Main Street North Andover,MA 01845 RE: Stormwater Review Comments ##1 Improvement of Rea Street Dear Ms. Enright and Ms. Hughes: Per your request I have conducted a stormwater technical review of the proposed Definitive Subdivision Plan for Improvement of Rea Street in North Andover. The applicant is proposing to construct a 1,304 foot long residential roadway and seven (7) new single-family House lots. Included in the materials I received and reviewed were the following documents: L Form C -Application for Definitive Subdivision Approval 2, Definitive Subdivision Plan for "Improvement of Rae Street" prepared by Christiansen& Sergi, Inc. dated June 11, 2018 and revised June 26, 2018, 3. Storrnwater Management Report prepared by Christiansen& Sergi, Inc. dated June 11, 2018 and revised June 26, 2018. Attaclnaent to this report include the "Pollution Prevention and Operations and Maintenance Plan for construction and post construction phase. 4. Notice of Intent prepared by Christiansen& Sergi, Inc. dated June 16, 2018, General 1. The applicant is requesting a waiver from the Environmental and Community Impact Statement under Section 5,1,5 of Form C stating that only 5 new lots are proposed with 1 lot that exists already, However; the plans and the stormwater management report show a total of seven(7) lots. The applicant should clarify the number of lots and revise/update all material accordingly to be consistent. ssy INC. 609 Winter Street Framingham,MA 01702 Phone: 508-745-4077 2. The applicant should consider eliminating the outlet pipes from the proposed infiltration basins or shorten the outlet pipe length so as not to have any stormwater infrastructure within any resource areas such as No Build Zone and Riverfront Corridor. 3. The proposed house and the infiltration system on Lot 7 cannot be approved. The footprint of the house does not comply with the Rivers Protection Act and the proposed infiltration system is placed within.the 50-foot No Build Zone. 4. Alternatives Analysis submitted by the Applicant is very rudimentary and requires a much more robust evaluation to satisfy the Rivers Protection Act. S. The Applicant must coordinate with the Town Engineer to review the proposed runoff treatment and management from Rae Street on private properties with drainage easements, Typically stormdrain system is located within street R-O-W with infiltration systems on individual lots for roof and driveway runoff only. Stornnvater Review -MADEP Checklist for Stormwater Report 1. Standard 1 states that no new storrnivater conveyances may discharge untreated storrrrwater directly to or cause erosion in wetlands of the Commonwealth. The project proposes six(6)new outfall discharges alongside Mosquito Brook. It appears that stormwater is routed through infiltration basins prior to discharge through the new outfalls. It appears that Standard 1 is met; however, the Applicant should further address this as noted in my comments under Standards 2 and 4 below. 2. Standard 2 requires that post-developrrrent runoff does not exceed pre-development runoff off-site. a. The Applicant has analyzed one(1) design point(DP)under existing conditions and seven (7)under proposed conditions within the project limits. Typically, the number of DPs and their locations match under the existing and proposed conditions to demonstrate that the proposed project results in net decrease in peak flows over the existing conditions. It is likely that the proposed project may meet this Standard given the proposed infiltration systems; however, the applicant should revise the HydroCAD modeling to match the DPs. b. The applicant should provide details on the Plan Set to show how runoff from roofs and driveways is conveyed to the infiltration systems. S' S"V toEiNGINF3,RING INC:. 609 Winter Street Framingham,MA 01702 Phone: 508-745-4077 c. Runoff from Rae Street appears to be directed to the proposed grassed channel. Additional details must be provided in the Plan Set for placing stone to limit erosion and also capture debris and sediment as runoff from Rae Street enters the grassed channels• 3. Standard 3 requires that the annual i-eeharge from post-developtfreret shall approximate annual recharge fr-ont pre-development conditions. a: The Applicant has provided Groundwater Recharge calculations that are included in the Stornwater Management Report. The Applicant has calculated the required recharge volume utilizing HSG A soils and 1.11 acres as the proposed impervious pavement and rooftop area. The HydroCAD report indicates a total impervious paved parking area of 1.284 acres and no rooftop area is listed. The Applicant should clarify the total new impervious area with a breakdown of Rae Street paved area, paved areas of the driveways to the lots and rooftop areas and revise/update the HydroCAD modeling accordingly, b• To fixther verify that the proposed development is in compliance with Standard 3, the Applicant must conduct infiltration tests to confirm the assumed infiltration rate of 8.27 inner, 4. Standard 4 requires that the storttnvater system be designed to remove 80% Total Suspended Solids (TSS) and to treat 0.5-inch or I.0-inch of volume front the impervious area for water quality. a) The Applicant has provided water quality volume calculations that are included in the Stormwater Management Report. The Applicant has calculated the required water quality volume by multiplying the impervious area by 1.0 inch of runoff per Volume 3, Chapter 1,page 32 of the Massachusetts Stormwater Handbook. b) The Applicant must revise the TSS removal calculation worksheets to depict the proposed treatment train that combines the grass channel and infiltration system. c) The Applicant is seeking a TSS removal of 50%for the proposed grassed channel. In accordance with Volume 2, Chapter 2, page 73 of the Massachusetts Stormwater Handbook, a sediment forebay or equivalent must be provided in order to take the 50% TSS removal credit, The Plan Set should be updated to include details for sediment bay or equivalent. SSV U.NGIN G UNG INC. 509 Winter Street Framingham,MA 01702 Phone:508-745-4077 5. Standard 5 is related to projects with a Lurid Use of Higher Potential Polluutant Loads (LUHPPL). a) Standard 5 is not applicable to this site. 6. Standard b is related to projects with stormwater discharging into a critical area, a Zone H or an Interim Wellhead Protection Area of a public water supply. a) Standard 6 is not applicable to this site. 7. Standard 7 is related to projects considered Redevelopment. a) Standard 7 is not applicable as the proposed project is new development. 8. Standard 8 requires a plan to control construction related impacts including erosion, sedimentation or other pollutant sources. a) The Applicant has acknowledged that a Stormwater Pollution Prevention Plan (SWPPP) will be prepared in accordance with the EPA Construction General Permit requirements for projects disturbing more than one acre of land. I recommend that the Conservation Commission consider including a Special Condition requiring the Applicant to provide the SWPPP to the Town a minimum of 14 days prior to any land disturbance. b) The construction sequence prepared by the Applicant indicates that the crushed stone construction entrance will be installed after the trees have been cut and grubbing of the site is commenced/completed. I recornrnend that the construction entrances must be installed as part of the sedimentation control of the whole site prior to any activities on- site. The construction sequence must be revised accordingly. c) Sheet 9 of 12 of the Plan Set should indicate the anticipated location(s) of the crushed stone construction entrance for Rae Street construction and at each lot following construction of Rae Street so that the construction contractor knows of this requirement. d) I recommend that sedimentation control barrier must be installed around the temporary earth stockpile areas. This should be added to the Plan Set. e) The Applicant must clarify if the infiltration basins on the individual lots will be utilized as temporary sediment basins during construction. I would recommend that temporary sediment basins during construction cannot be placed at the same location as the proposed infiltration basins. i r II S�1'3pv ENGINLER1NG INC. to 609 Winter Street Framingham.MA 01702 E Phone:508-745-40'7'7 9. Standard 9 requires a Long Term Operation and Maintenance (OEM) Plan to be provided. a) The Applicant has provided a Pollution Prevention and Operation and Maintenance (O &M) Plan that is included in the Stormwater Management Report. The Applicant indicates that ultimately the Town will take ownership of the stormwater management system components that lie both within Rae Street R-O-W and proposed drainage easements. In my opinion this is not a standard practice given that the stormwater systems are small and service primarily individual lots. Individual lot owners should take ownership of the stormwater systems within their property and the Town can take ownership of systems within the Rae Street R-O-W. 10.Standard 10 requires an Illicit Discharge Compliance Statement to be provided. a) The Applicant appears to be in compliance with Standard 10. Wetlands Review 1. Following are the overall conunents based on the current documentation: a. The wetland flags shown on the Plan Set appear to be incomplete as they do not extent to at least the limits of the project and beyond. b. The Plan Set must show the centerline and the banks of Mosquito Brook and provide a description of how it was established and confirmed. c. The 100-year Floodplain shown on the Plan Set appears to be erroneous as it does not seem to follow an elevation. Also, the wetland flags are located above the floodplain. A description of how the floodplain was determined and established must be provided. d. It appears that there is beaver activity along Mosquito Brook. A description of how the applicant is proposing to manage this issue during construction and post-construction must be provided. e. The Applicant must provide a description a detailed description of how the proposed project complies with the Rivers Protection Act. ........... . ............. ........................................ ...... . . 5 I P a g e ssyINURINC G INC 609 Winter Street Framing}iam,NIA 01702 Phone: 508-745-4077 I would be happy to meet with you and the Applicant to review these comments at your convenience. Please feel free to contact me if you or the applicants have any questions regarding the issues addressed herein, Very truly yours, ti ._ Sam Bade President 6 1 P a g e i GNiili UMAtING INC. 609 Winter Street 3 Framingham.MA 01702 3 Phone: 508-745-4077 October 22, 2018 Ms. Jean Enright,Planning Director Planning Department 120 Main Street North Andover, MA 01845 Ms. Jennifer Hughes, Conservation Administrator Conservation Department E 120 Main Street North Andover, MA 01845 RE: Stormwater Review Comments 04 Improvement of Rea Street Dear Ms. Enright and Ms. Hughes: This letter memorandum summarizes review of the supplemental information submitted by Christiansen & Sergi to provide responses to my review comments fetter dated September 24,2018. Included in the materials I received and reviewed were the following: ➢ Response to comments letter dated September 28, 2018, and prepared by Christiansen & Sergi. ➢ Definitive Subdivision Plan for "Improvement of Rae Street" prepared by Christiansen & Sergi, Inc. dated June 11, 2018 and revised September 28, 2018. ➢ Stormwater Management Report prepared by Christiansen & Sergi, Inc. dated June 11, 2018 and revised September 28, 2018. Please note that a revised Notice of Intent Application and related material have not been submitted at the time of this review. My supplemental comments are outlined below with the suffix "D" to my original comment number•. Updated comments are shown in bold and underlined text: II tot ntcirnt:r.itt�c.��vc:. S CAV 609 Winter Street Framingham.MA 01702 Phone: 508-745-4077 General ID. The applicant states that the waiver request for the Site Evaluation Statement was erroneous and a Statement has been provided. No further comment 2D. The applicant states that the proposed outlet pipes have been shortened where possible based on the minimum pipe slope and the rain garden has been removed from the riverfront area. The Applicant states that this will be addressed during the Notice of Intent process. The NACC Wetland Protection Regulations (Amended 3/23/16) states in part: "Stormwater structures and/or discharge may be allowed in the 50-foot No-Build Zone when no other feasible location exists or when it is necessary to maintain the hydrology of the resource. An alternatives analysis showing the net benefit of locating the structure in the No-Build Zone is required." Per the above requirement the Applicant must provide this alternatives analysis for structures proposed within the 50-foot No-Build Zone. No further comment 3D. The applicant states that proposed dwelling on Lot 7 is located more than 100'from Mosquito Brook. The Applicant states that this will be addressed during the Notice of Intent process. This will be further reviewed upon the applicant's submission of a detailed alternatives analysis under the Rivers Protection Act. No further comment 4D. The applicant states that a revised Alternatives Analysis would be provided for review during the Notice of Intent approval process. This will be reviewed upon receipt of revised NOI from the applicant. No further comment SD. The Applicant must coordinate with the Town Engineer to review the proposed runoff treatment and management from Rae Street on private properties with UT , IiNGIN[IF ItINC INC:. to 609 Winter Street Framingham,MA 01702 Phone: 508-745-4077 areas-, however,they do not include the proposed„catch basins and the Contech E Water Quality Unit. The applicant appears to ineet and exceeds the required 80% TSS removal. No additional cominent. c. Not applicable with the new desi::ri. 5D.Standard 5 is related to projects with a Land Use of Higher-Potential Pollutant Loads (L UHPPL). a. Standard 5 is not applicable to this site. 6D.Standard 6 is related to projects with stornnvater discharging into a critical area, a Zone H or an Interim Wellhead Protection Area of a public water supply. a. Standard 6 is not applicable to this site. 7D.Standard 7 is related to projects considered Redevelopment. No additional comment. 8D.Standard 8 requires a plan to control construction related impacts including erosion, sedimentation or other pollutant sources. a. The Applicant has acknowledged that a Stormwater Pollution Prevention Plan (SWPPP)will be prepared in accordance with the EPA Construction General Permit requirements for projects disturbing more than one acre of land, I recommend that the Conservation Commission consider including a Special Condition requiring the Applicant to provide the SWPPP to the Town a minimum of 14 days prior to any land disturbance. b. The construction sequence prepared by the Applicant indicates that the crushed stone construction entrance will be installed after the trees have been cut and grubbing of the site is commenced/completed. The applicant states that clearing, grubbing and grading will be needed prior to installation of stabilized construction entrance. A s ecial condition could be added to state that the stabilized construction entrances be installed immediately followin the clearing and rubbilt . No further Comment. ENGINEERINCING 609 Winter Street Cramingharn.MA 01702 Phone: 508-745-4077 c. No further comment. d. Siltation controls have been added around each soil stockpile area. No further comment. e. Not applicable with the new design. 9D. Standard 9 requires a Long Term Operation and Maintenance (O&M) Plan to be provided. a. The Applicant states that the Town or the Homeowner's Association would be the responsible party for the proposed storrnwater features. The applicant must discuss this with the Town Engineer and the Board. Table t titled "Best _Management Practice Maintenance" included in the Stormwater Management Report must identify the responsible party for the best management practice features proposed for the project. This comment still stands. No further comment. IOD. Standard 1 D requires an Illicit Discharge Compliance Statement to be provided. a. Tlme Applicant appears to be in compliance with Standard tO. No further comment. Wetlands Review The Applicant states the following: "All comments concerning wetlands regulations will be resolved with the Conservation Commission and its agent during the Notice of Intent Process." A review of the Notice of Intent submission will be completed upon receipt. Below are the preliminary comments from my review based on the initial submission: L Following are the overall comments based on the current documentation; a. The wetland flags shown on the Plan Set appear to be incomplete as they do not extent to at least the limits of the project and beyond. b. The Plan Set must show the centerline and the banks of Mosquito Brook and Q i I IiNCill\I:ERING INC, 609 Winter Street Framingliam.MA 01702 Phone: 508-745-4077 drainage easements. Typically stormdrain system is located within street R-O-W with infiltration systems on individual lots for roof and driveway runoff only. The ownership and wailltenauce of the proposed storinwater Inana elment features must be discussed with the Town Engineer and the Board. See Item 9 under Storinwater Review below. This comment still stands. Stormwater Review - MADEP Checklist for Storinwater Report ID,Standard 1 states that no new stormivater conveyances may discharge untreated storm water directly to or cause erosion in wetlands of the Commonwealth. This Standard is met. No additional comment. 2D.Standard 2 requires that post-development runoff does not exceed pre development runoff off-site.. a. The Applicant has analyzed one (1) design point(DP) under existing conditions and seven (7) under proposed conditions within the project limits. Typically, the number of DPs and their locations match under the existing and proposed conditions to demonstrate that the proposed project results in net decrease in peak flows over the existing conditions. It is likely that the proposed project may meet this Standard given the proposed infiltration systems; however, the applicant should revise the HydroCAD modeling to match the DPs. This comment still stands in part. Proposed subeatchment "P6" is shown with a new outfall and does not discharge to the "Design Point(DP-1)". Below is a description of wily this is significant: The HvdroCAD modeling lists the 2-year peak runoff'from existing to be 9.96 cfs at DPI (contributing area is 15.463 acres). The 27year peak runoff for the proposed conditions at DPI (contributing area is 14.912 acres) is 9.55 cfs. This does not include drainage area for sub-catchment P6 (0.482 acres)with a peak flow of 0.84 cfs. The total flow from the proposed rp oiect_is 10.39_efs which is neater than the 9.96 cfs under existing conditions. ENGINEERING INC:. 609 Winter Street Framingham.MA 01702 Phone: 508-745-4077 This applies to all of the design. storms. The project does not meet Standard #2 as presented. b. The applicant should provide details on the Plan Set to show how runoff from roofs and driveways is conveyed to the infiltration systems. This comment has been addressed. As mentioned above the ownership of the proposed drainage system and easements must be reviewed with the Town Enizineer. c. Runoff from Rea Street appeals to be directed to the proposed grassed channel. Additional details must be provided in the Plan Set for placing stone to limit erosion and also capture debris and sediment as runoff from Rae Street enters the grassed channels. This is no longer a lieable. 3D.Standard 3 requires that the annual recharge ft•om post-developmeni shall approximate annual recharge from pre-development conditions. a. The area of imperviousness and the required recharge volume has been revised and updated. No additional comment. b. No additional comment. c. Section VII Water Quality Volume Calculations must state the following: "The design of the infiltration areas provide for a volume of 7,470 cubic feet which exceeds the required water quality volume. 4D.Standard 4 requires that the stormwater system be designed to remove 80% Total Suspended Solids (TSS) and to treat 0.5-inch or 1.0-inch of volunte from the impervious area for water quality. a. No additional comment. b. The revised TSS removal calculations takes credit for the proposed two infiltration i i i I E NCI NI:EItING INC;. to 609 Winter Street Framingham MA 01702 Phone: 508-745-4077 provide a description of how it was established and confirmed, c. The 100-year Ploodplain shown on the Plan Set appears to be erroneous as it does not seem to follow an elevation. Also, the wetland flags are located above the floodplain. A description of how the floodplain was determined and established must be provided, d. It appears that there is beaver activity along Mosquito Brook. A description of how the applicant is proposing to manage this issue during construction and post-construction must be provided, e. The Applicant must provide a description a detailed description of how the proposed project complies with the Rivers Protection Act. New Comments on the Definitive Subdivision Plan dated September 18, 2018 1. Detail for the proposed walking path must be shown. No further comment. 2. Proposed roof drywell for Lot 1 could be relocated southwest of the driveway. This has been addressed. No further comment. 3. Details for the drainage easements such as width and lengths must be shown. This has been addressed. No further comment. 4. Detail for the proposed 2-foot wide trench drain along the north side of Rea Street must be included, This has been addressed. No further comment. 5. Details for the proposed stornidrain pipe between the 2-foot wide trench drain and the drain manhole located at corner of Lots 4 and 5 must be shown. This pipe is shown with a bend without a cleanout or similar structure for maintenance. This has been addressed. No further comment, 6. The applicant must indicate that the runoff from the proposed driveways is directed towards the proposed storm drain system and does not flow towards the wetlands. This has been addressed.No further comment. 7 Page OF ENC,INE:ERING IN(". 609 Winter Street Framinghani.MA 01702 Phone; 508-745-4077 7. Outfall from the proposed Infiltration Area 2 is located within the 50-foot No- Build Zone. The applicant could relocate the Infiltration Area further north in Lot 6 with an outlet that is located outside of the 50-foot No-Build Zone with an invert of 164.0'. This has been. addressed. No further comment. S. The applicant must provide additional details on the proposed sewer pump station. This could include a backup pump, high water alarm system, volume of storage in the wet well available and the duration before any overflow could occur towards the wetlands and the brook. The Applicant indicates that the sewer pump station will be submitted for approval by the Town. The concern is any sewage overflow due to pump failure and/or loss of power. This should be addressed during the review of the sewage sump pump station design submittal.No further comment. 9. The Construction Details Sheet includes a generic water quality unit. The model of the water quality unit and/or the design flow details must be specified. This has been addressed. No further comment. I would be happy to meet with you and the Applicant to review these comments at your convenience. Please feel free to contact me if you or the applicants have any questions regarding the issues addressed herein. Very truly yours, Sam Bade President 8 Page e a i S S.V,. ENGINEERING INC. 609 Winter Street Framingham.MA 01702 Phone: 508-745-4077 November 8, 2018 Ms. Jean Enright,Planning Director Planning Department 120 Main Street North Andover, MA 01845 Ms. Jennifer Hughes, Conservation Administrator Conservation Department 120 Main Street North Andover, MA 01845 RE: Stormwater Review Comments#5 Improvement of Rea Street Dear Ms. Enright and Ms. Hughes: This letter memorandum summarizes review of the supplemental information submitted by Christiansen & Sergi to provide responses to my review comment letter dated October 22, 2018. Included in the materials I received and reviewed were the following: ➢ Response to comments letter dated November 1, 2018, and prepared by Christiansen & Sergi. ➢ Definitive Subdivision Plan for "Improvement of Rae Street" prepared by Christiansen & Sergi, Inc. dated June 11, 2018 and revised October 17, 2018. ➢ Stormwater Management Report prepared by Christiansen & Sergi, Inc. dated June 11, 2018 and revised October 17, 2018, Please note that a revised Notice of Intent Application and related material have not been submitted at the time of this review. Below is a comprehensive listing and summary of all of the comments for the record. I have left text in bold and underline that requires your attention as you prepare the draft special conditions for the project. It appears that the Applicant has addressed my comments. i i i i 3 i SS.V. ENGINE RING INC 609 Winter Street Framingham.MA 01702 Phone; 508-745-4077 S General j ID. The applicant states that the waiver request for the Site Evaluation Statement was erroneous and a Statement has been provided. No further comment 2D. The applicant states that the proposed outlet pipes have been shortened where possible based on the minimum pipe slope and the rain garden has been removed from the riverfront area. The Applicant states that this will be addressed during the Notice of Intent process. The NACC Wetland Protection Regulations(Amended 3/23/16) states in part: "Stormwater structures and/or discharge may be allowed in the 50-foot No-Build Zone when no other feasible location exists or when it is necessary to maintain the hydrology of the resource. An alternatives analysis showing the net benefit of locating the structure in the No-Build Zone is required." Per the above requirement the Applicant must provide this alternatives analysis for structures proposed within the 50-foot No-Build Zone. No further comment 3D. The applicant states that proposed dwelling on Lot 7 is located more than 100'from Mosquito Brook. The Applicant states that this will be addressed during the Notice of Intent process. This will be further reviewed upon the applicant's submission of a detailed alternatives analysis under the Rivers Protection Act. No further comment 4D. The applicant states that a revised Alternatives Analysis would be provided for review daring the Notice of Intent approval process. This will be reviewed upon receipt of revised NOI frona the applicant. No further comment i M I SS-V LNUINEERINO INC;. 609 Winter Street Framingliam.MA 01702 Phone: 508-745-4077 5D. The Applicant must coordinate with the Town Engineer to review the proposed runoff treatment and management from Rae Street on private properties with drainage easements. Typically stormdrain system is located within street R O-W with infiltration systems on individual lots for roof and driveway runoff only. The ownership and maintenance of the proposed storrnwater management features must be discussed with the Town Engineer and the Board. See Item 9 under Stormwater Review below. The Applicant states that this issue was discussed with the Town Engineer and would accept a prolect special condition. The Board should discuss this and recommend appropriate lanl4ual4e for a special condition. Stormwater Review - MADEP Checklist for Storrnwater Report ID.Standard 1 states that no new stormwater conveyances may discharge untreated storinwater directly to or cause erosion in wetlands of the Commonwealth. This Standard is met. No additional comment. .2D.Standard 2 requires that post-development runoff does not exceed pre-development runoff off site. a. The Applicant has analyzed one(1) design point(DP) under existing conditions and seven (7)under proposed conditions within the project limits. Typically, the number of DPs and their locations match under the existing and proposed conditions to demonstrate that the proposed project results in net decrease in peak flows over the existing conditions. It is likely that the proposed project may meet this Standard given the proposed infiltration systems; however, the applicant should revise the HydroCAD modeling to match the DPs. Based on the review of the Storinwater Management Report with a revision date of October 17, 2018 the Applicant has addressed this issue. No additional comment. i SS'V' ENGINEERING INC, 609 Winter Street Framingham MA 01702 Phone: 508-745-4077 b. The applicant should provide details on the Plan Set to show how runoff from roofs and driveways is conveyed to the infiltration systems. This comment has been addressed. As mentioned above the ownership of the prioposed drainage system and easements must be reviewed with the Town Engineer. The Applicant states that this issue was discussed with the Town Engineer and would accept a project special condition. The Board should discuss this and recommend appropriate lanwua�ae for a special condition. c. Runoff from Rea Street appeals to be directed to the proposed grassed channel. Additional details must be provided in the Plan Set for placing stone to limit erosion and also capture debris and sediment as runoff from Rae Street enters the grassed channels. This comment is no longer applicable._ 3D.Standard 3 requires that the annual recharge fi-ont post-development shall approximate annual recharge from pre-developinent conditions. a. The area of imperviousness and the required recharge volume has been revised and updated, No additional comment. b. No additional comment. c. Section V11 Water uali Volume Calculations must state the followin ; "The design of the infiltration areas provide for a volume of 7,470 cubic feet which exceeds the required water quality volume. 4D.Standard 4 requires that the storntwater system be designed to re►nove 80% Total Suspender)Solids (TSS) and to treat 0.5-inch or 1.0-inch of volume from the impervious area for water quality. a. No additional comment. b. The revised TSS removal calculations takes credit for the proposed two infiltration S SV LNGIN1iLIMM, INC. 609 Winter Street Frainingiiam.MA 01702 Phone: 508-745-4077 areas,• howeverLhey do not include the proposed catch basins and the Contech Water ality Unit. The applicant appears to meet and exceeds the required 80%TSS removal, No additional comment. c. Not applicable with the new desi rir, SD.Standard 5 is related to projects with a Laud Use of Highest Potential Pollutant Loads (L UHPPL). a. Standard 5 is not applicable to this site. 6D.Standard 6 is related to projects with storinivater discharging into a critical area, a Zone H or an Interim Wellhead Protection Area of a public water supply. a. Standard 6 is not applicable to this site. 7D.Standard 7 is related to projects considered Redevelopment. No additional comment. 8D.Standard 8 requires a plan to control construction related impacts including erosion, sedimentation or other pollutant sources. a. The Applicant has acknowledged that a Stormwater Pollution Prevention Plan (SWPPP)will be prepared in accordance with the EPA Construction General Permit requirements for projects disturbing more than one acre of land. 1 recommend that the Conservation Commission consider including a Special Condition requiring the Applicant to provide the SWPPP to the Town a minimum of 14 days prior to any land disturbance. b. The construction sequence prepared by the Applicant indicates that the crushed stone construction entrance will be installed after the trees have been cut and grubbing of the site is commenced/completed. The applicant states that clearing, grubbing and grading will be needed prior to installation of stabilized construction entrance. A pecial condition could be added to state that the stabilized construction y g f 'ubbint".No further entrances be installed immediate) following the clearing and Comment. i '1 SSV ENGINEFRING INC:. 609 Winter Street Framingliam.MA 01702 Phone: 508-745-4077 c. No ftirther comment. d. Siltation controls have been added around each soil stockpile area. No further comment. e. Not applicable with the new design. 9D. Standard 9 requires a Long Term Operation and Maintenance (O&M) Plant to be provided a. The Applicant states that the Town or the Homeowner's Association would be the respqnsible.party for the proposed stormwater features. The applicant must discuss this with the Town Engineer and the Board. Table 1 titled "Best Management Practice Maintenance" included in the Storrnwater Management Report must identify the responsible party for the best management practice features proposed for the project, This issue has been addressed. The Applicant states that this issue was discussed with the Town Engineer and would accept a project special condition. The Board should discuss this and reconunend appropriate lanmua2e for a special condition. 10D. Standard 10 requires tin Illicit Discharge Compliance Statement to be provided. a. The Applicant appears to be in compliance with Standard 10, No further comment. Wetlands Review The Applicant states the following: "All comments concerning wetlands regulations will be resolved with the Conservation Commission and its agent during the Notice of Intent Process." A review of the Notice of Intent submission will be completed upon receipt. Below are the preliminary comments from my review based on the initial submission; 1, Following are the overall comments based on the current documentation; a. The wetland flags shown on the Plan Set appear to be incomplete as they do not i C s 3 I { SS'V ENCiINIiC.RING INC:, 609 Winter Street Framingham.MA 01702 Phone: 508-745-4077 E extent to at least the limits of the project and beyond, b. The Plan Set must show the centerline and the banks of Mosquito Brook and provide a description of how it was established and confirmed. c. The 100-year Floodplain shown on the Plan Set appears to be erroneous as it does not seem to follow an elevation. Also, the wetland flags are located above the floodplain. A description of how the floodplain was determined and established must be provided. d. It appears that there is beaver activity along Mosquito Brook. A description of how the applicant is proposing to manage this issue during construction and post-construction must be provided. e, The Applicant must provide a description a detailed description of how the proposed project complies with the Rivers Protection Act. New Comments oil the Definitive Subdivision Plait elated September 18, 2018 1. Detail for the proposed walling path must be shown. No further comment. 2. Proposed roof drywell for Lot 1 could be relocated southwest of the driveway, This has been addressed. No further comment. 3. Details for the drainage easements such as width and lengths must be shown. This has been addressed. No further comment. 4. Detail for the proposed 2-foot wide trench drain along the north side of Rea Street must be included. This has been addressed. No further con-rnent. 5. Details for the proposed stornidrain pipe between the 2-foot wide trench drain and the drain manhole located at corner of Lots 4 and 5 must be shown. This pipe is shown with a bend without a cleanout or similar structure for maintenance. This has been addressed. No further comment. 6. The applicant must indicate that the runoff from the proposed driveways is directed towards the proposed storm drain system and does not flow towards the wetlands. This has been addressed. No further comment, 7 Page i SS'V t:NG1NEERINC=INC. 609 Winter Street Framingliam,MA 01702 Phone; 508-745-4077 i i 7. Outfall from the proposed Infiltration Area 2 is located within the 50-foot No- Build Zone. The applicant could relocate the Infiltration Area further north in Lot 6 with an outlet that is located outside of the 50-foot No-Build Zone with an invert of 164.0'. This has been addressed, No further connivent. 8. The applicant niust provide additional details on the proposed sewer pump station. This could include a backup pump, high water alarin system, volume of storage in the wet well available and the duration before any overflow could occur towards (lie wetlands and the brook. The Applicant indicates that the sewer pump station will be submitted for approval by the Town. The concern is any sewage overflow due to pump failure and/or loss of power. This should be addressed during the review of the sewage sump pump station designs submittal.No further comment, 9. The Construction Details Sheet includes a generic water quality unit. The model of the water quality unit and/or the design flow details must be specified. This has been addressed, No fiirther continent. The Applicant appears to have addressed my comments. Please consider this letter as my final review. Please feel fi'ee to contact me if you or the applicants have any questions regarding the issues addressed herein. Very truly yours, Sam Bade President 8 Page