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HomeMy WebLinkAboutPeer Review 1 ............................ ..................................................................... .......................... ........... 8/2112017 Town of North Andover Mail-RE:SALEM STREET Rebecca Oldham <roldham@northandoverma.gov> RE: SALEM STREET Rebecca Oldham <roldham@northandoverma.gov> Mon, Aug 21, 2017 at 2:45 PM Draft Forwarded message From: Peter Ellison<PEllison@theengineeringr-orp.com> Date: Mon,Aug 21, 2017 at 2:35 PM Subject: RE:SALEM STREET To: Rebecca Oldham<roIdham@northandoverma.gov> Hi Rebecca, all stormwater concerns have been addressed. Thanks, Peter Peter Ellison, PE Civil Engineer "THC EN Of r4CCRI NO CC FZP.CCMr' 978-794-1792 1161 From: Rebecca Oldham [mailto:roldham@northandoverma.gov] Sent: Sunday,August 20, 2017 5:07 PM To: Peter Ellison Subject. Fwd: SALEM STREET https:lfmail.google.com/mail/u/01?ui=2&ik=ab4f3cb798&jsver--RKK5Ah87d4U.en.&view=pt&search=inbo-x&rnsg=l 5e061 d74c8ecd40&dsqt=4&siml='5eO6l43ae61 Sal a&sIrnl=15e061 d74c8ecd40 113 8/21/2017 Town of North Andover Mail-RE:SALEM STREET Please see updated plans for 1975 Salem and let me know if this satisfies all stormwater concerns. Thank you, --Rebecca Sent from my iPhone Begin forwarded message: From: Phil Christiansen <phil@csi-engr,com> Date:August 20,2017 at 2:10:50 PM EDT To: Rebecca Oldham<roldham@northandoverma.gov> Subject: SALEM STREET Rebecca believe the attached plans address the remaining issues for the project.The plans are a response to items 41,42,43,and 44. In response to item 45 1 have submitted colored pdf plans to ease the review, If and when approved I can supply black and white pdf plans but the colored plans can be printed in black and white and included as attachments to any decision. Please let me know if there are any outstanding items I have missed. PbRip Christiansen P.E. CHRISTLkNSEN&SERGI,INC. PROFESSIONAL ENGINEERS AND LAND SURVEYORS 160 Summer Stxeet HaveThi11,TVIA 0 1830 (978)373-0310 https:llmail.google.com/maiVu101?ui=2&ik=ab4f3cb798&jsver=RKK6Ah87d4U.en.&view=pt&search=inbox&msg=l5eO6l d74cBec.d4O&dsgt=l&siml=15e06143ae615al a&siml=15e061 d74c8ecd40 2/3 8/21/2017 Town of North Andover Mail-RE:SALEM STREET https://mail.google.com/mail/u/0/?ui=2&ik=ab4f3r-b798&jsver=RKK5Ah87d4U.en.&view=pt&search=inbox&msg=15eO6ld74c8ecd4C&dsgt=l&siml=l5eO6l43ae6l5ala&sim1=15e061d74c8ecd40 3/3 1 65 Glenn Street 169 ocean Blvd. TiEE; Lawrence,MA01843 Hampton, NH 03842 T:978.794.1792 T;603.601.8154 ARW TheEngineeringCorp.com €E k Rebecca Oldham, Staff Planner August 1, 2017 Town of North Andover Planning Department 1600 Osgood Street North Andover, MA 01845 i TEC Ref. T0652.08 i Re: Peer Review #4 Land Disturbance Permit Application 1975 Salem Street, North Andover, MA Dear Ms. Oldham: On behalf of the Town of North Andover, TEC, Inc. conducted a technical review of the April, 2017 Land Disturbance Permit Application for the proposed project to be located at 1975 Salem Street. Livingstone Development Corporation ("Applicant") submitted the following documents, which TEC reviewed for conformance with Chapter 160 of the General Bylaws of the Town of North Andover, the North Andover Stormwater Management and Erosion Control Regulations, and the Massachusetts Stormwater Handbook: • Response to Peer Review, 1975 Salem Street, North Andover, MA prepared by Christiansen & Sergi, Inc., dated July 3, 2017; • Site Plan for Special Permit, Lots 1-3 Salem Street, North Andover, MA, prepared by Christiansen &Sergi, Inc., dated October 3, 2016, revised December 28, 2016, February 17, 2017, April 7, 2017, June 14, 2017, and July 3, 2017; • Existing Drainage HydroCAD Report, Lots 1-3 Salem Street, North Andover, MA, prepared by Christiansen &Sergi, Inc., dated July 4, 2017; and • Proposed Drainage HydroCAD Report, Lots 1-3 Salem Street, North Andover, MA, prepared by Christiansen & Sergi, Inc., dated July 4, 2017. Upon review of the latest submission, TEC compiled the following list of comments. For consistency, the outstanding original comment numbers have been retained from the most recent TEC review letter dated April 26, 2017, The Applicant's response to comments is shown as bold; TEC responses are shown as italic. 1. The Board should note that the Applicant has requested multiple Special Permits from the Town of North Andover Zoning Bylaws which have been listed on the plans: a. Section 7.2.1 --Access across street frontage. b. Section 7.2.2 — Frontage exception. Applicant Response: We had filed for a common driveway in addition to the Frontage exception lot and access not through the lot frontage. TEC., Comment addressed. Plan Permit Design Construct Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review August 1, 2017 Page 2 of 16 2. It appears that the Applicant is proposing work within one hundred (100' feet to resource areas; the Applicant should verify that the project will be permitted with the Conservation Commission. Applicant Response: The project was reviewed by the Conservation Commission and an Order of Conditions issued by the Commission approving the project. TEC.• Comment addressed 3. Section 7.1 -the Applicant should provide a Stormwater Management Plan that meets the requirements of sections 7.1 &7.2 of the North Andover Stormwater Management and Erosion Control Regulations. Applicant Response: The plans as submitted comply with Section 7.1 and 7.2 of the North Andover Stormwater Management and Erosion Control regulations. Additional summaries, descriptions and modifications as requested by the TEC have been added in the attached plans and reports to supplement the original filing. TEC.• See detailed comments below. 4. Section 7.1.b -The Applicant should include a brief narrative description of the project including how and where stormwater is to be controlled. Applicant Response: This project has been before both the Conservation Commission and the Planning Board for many months and several public hearings were held. Both the Commission and the Board approved the project for the permits requested. The project was described to the Board on numerous occasions including a description of stormwater controls. Not including the project description in this application was an oversight and a description is contained with the submitted information. TEC.• Comment addressed 5. Section 7.1.e-The Applicant should revise the Stormwater Plan to include the size of entire parcel, each drainage area on or to the parcel, and the total square feet of land area subject to disturbance. Applicant Response: The entire parcel consists of three lots and the area of each is on the plan. The entire parcel area of 331,307 s.f. has been added to Sheetl. The drainage areas are listed on the drainage plans and the area for each drainage area is listed in the HydroCAD report. T have added the areas to the Drainage Plan to assist the reviewer. We had previously reviewed the total disturbance for a number of alternative designs suggested by the Board. Of those this project offered the least disturbance of the alternatives investigated. The total disturbance has been added to sheet 2. T:\T0652\T0652.08\Docs\Letters\T0652.08_1975 Salem Street Peer Review#4_8-1-2017.docx �� 0 i Ms, Rebecca Oldham Lots 1-3 Salem Street-- Peer Review August 1, 2017 Page 3 of 16 E TEC.• Comment addressed. 6. Section 7.1.h -The Applicant should clearly label all existing and proposed easements. Note 1 indicates an easement on lot 3. Applicant Response: The proposed drive easement was labeled on sheet 2 of 4. A l label has been added to sheet 1. The note has been corrected, TEC,• Comment addressed. 7, The Stormwater Management Plan should clearly label all three lots. i Applicant Response: The lot labels are on sheet 1 (see attached) TEC.• Comment addressed. 8. Section 7.1.i -The plan should include the edge of the existing driveway on the abutting property to the southeast of the project, Applicant Response: The driveway (actually a roadway) was shown on sheet 2. TEC. Comment addressed. 9. Section 7.1,j -The plan should be revised to label areas of steep slopes between 15-25% and areas of steep slopes over 25%. Also, the plan should include existing topography fifty feet beyond the perimeter of the parcel. Applicant Response: I have added a sheet which contains the required slope information. TEC, Comment partlally addressed, the Applicant has provided a Slope Analysis diagram, however, the Applicant has not provided existing topography fifty feet beyond the perimeter of the parcel. Applicant Response: Additional existing topography within 50 feet of the property boundary has been added to the plan adjacent to the onsite topography previously shown. TEC• Comment addressed. 10, Section 7.1,k-The plan should clearly identify and describe all wetland resource areas. Applicant Response: The only wetland resource area on site is a small isolated wetland/vernal pool in the extreme southerly corner of lot 3 as shown on sheet 1. The site lies within the buffer zone of a wetland to the west, a wetland to the east across Salem Street and an isolated wetland along the northerly property line, The T:\T0652\TO652.08\Docs\Letters\TO652.08_1975 Salem Street Peer Review#4 8-1-2017.docx WE Ms. Rebecca Oldham Lots 1-3 Salem Street-- Peer Review August 1, 2017 Page 4 of 16 portion of the site that borders Salem Street lies within the Riverfront area. All resource areas were identified on the submitted plans. TEC.• Comment addressed. 11. Section 7.1.m --the location, delineation, and description of habitats mapped by the NI-IESP and also potential and certified vernal pools. Applicant Response: A vernal pool is shown on sheet 1. The parcel is in both priority and estimated habitat area. The proposed work was determined by the NHESP to be a"no take". (see attached letter from Fisheries and Wildlife) TEC.• Comment addressed. 12. Section 7.1.n -The Applicant should revise the plans to provide the general outline of existing tree fine/vegetation and the proposed outline of tree line/vegetation. Applicant Response: The property is fully wooded so that a tree line cannot be shown on the plan. The limit of work labeled on the plan is the proposed tree line. TEC.- Comment not addressed; the proposed limit of work line is not provided on the plan. Applicant Response: The limit of work line was on the original submittal on sheet 2. It was not on sheet 2 on the remised plans submitted June 14,2017 but was clearly indicated on the Landscape submitted on that same date. It is shown and labeled on the Proposed Site Plan submitted herewith. TEC.• Comment addressed. 13. Section 7.1.o-The plan should show existing septic systems within 100'of property. Applicant Response: There aren't any septic systems within 100 ft of the property TEC.• Comment addressed. 14. Section 7.1.p - The drainage area map should demonstrate the stormwater flow paths. Applicant Response: The flow paths have been added to the plans TEC., Comment addressed. 15. Sections 7,1.q&r- A description of the existing soils and estimated seasonal high groundwater elevation should be provided on the plans. T:�T0652\T0652.08\Docs\Letters\T0652,08_1975 Salem Street Peer Review#4_8-1-2017.docx � � Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review August 1, 2017 Page 5 of 16 Applicant Response: The soil is listed as a Canton. The MRCS data is attached as well as the onsite soil testing results that showed the parent soil to be a loamy sand. Groundwater was not observed. Percolation rates ranged from i to 9 min/inch. TEC.• Comment addressed, however, the Applicant should clearly label the test pits so that the naming convention matches the provided test pit results. Applicant Response: The test pits (TP) locations are labeled on the plans. The Soil Evaluator, Steve Erikson labeled them Deep Holes (DH) in the Soils report but labeled them in the field notes as TP. DH and TP are equivalent. TEC.• Comment addressed. Further test pits may be required within the proposed leaching field but this will be reviewed and approved by the Board of Health. 16. Section 7.1.0 - The Applicant should include documentation/calculations for the time of concentrations, infiltration rates, culvert capacities and flow velocities used in the hydrologic calculations. Applicant Response: The information requested is contained within the HydroCAD report. TEC.• Comment partially addressed; the Applicant has not provided documentation/calculations for the time of concentrations used in the analysis Applicant Response: The times of concentration for all sub catchments are contained in the HydroCAD report. The length of flow path, slope and CN are all contained in the report and each of these is used to calculate the time of concentration. The capacity of the culvert is also contained in the report. Manual calculations of time of concentration, culvert capacities and flow velocities are not done when those parameters are calculated by a program that is national recognized as being accurate in its development and function. The infiltration rate selected of 4 inches per hour is reasonably conservative considering the percolation rates ranged from 1 to 9 min/in and the permeability of C horizon of a Carlton soil is 6 to 20 inches per hour. We have provided all that is necessary for a proper hydrologic analysis, TEC.• Comment addressed. 17. Section 7A -The locus map provided should be adjusted to a scale of 1"=800'. Applicant Response: The Locus map has been changed from 400 to $00 scale. TEC.• Comment addressed T:NT0652\T0652.08\Docs\Letters\T0652.08_1975 Salem Street Peer Review#4 8-1-2017.docx TAfE Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review August 1, 2017 Page 6of16 18. Section 7.2.A--The Applicant should provide documentation that the project meets the requirements listed including how the project will meet the requirements of the Massachusetts Stormwater Handbook. Applicant Response: The reference by the consultant to section 7.2A Low Impact Design is somewhat misplaced. Typically LID design refers to subdivision design that varies from traditional design in that pavement width are minimized, swales are used rather than hard piping and stormwater is treated throughout the site rather than at one device to which all drainage is directed. Additionally,the Massachusetts Stormwater Handbook does not contain requirements but rather "Guidance"as specified in 7.2Ab) of the North Andover Stormwater Management regulations. The project, a three lot development meets the requirements of the Massachusetts Stormwater Regulations in that it is only a three lot project and the regulations do not apply to a three lot project. The project utilizes a common drive to minimize pavement, super elevated drives to direct water to stone shoulders and infiltration chambers to recharge to ground water and to reduce peak flow rates. The use of these design components proves the project to be an LID project and one that meets the guidelines of the Massachusetts Stormwater Handbook. TEC.• Comment not addressed. Section 7,2 of the Town of North Andover Stormwater Management and Erosion Control Regulations specifically states 'At a minimum all projects subject to a Land Disturbance Permit shall comply with the criteria specifications, and performance standards of the most recent version of the Massachusetts Stormwater Management Standards and accompanying Storm water Management Handbook as well the criteria contained herein." Applicant Response: Massachusetts Stormwater Management Standards do not apply to projects of 4 or fewer lots. The project contains only 3 lots and therefore by definition without any controls what so ever complies with Massachusetts Stormwater Standards. The project complies with regulation 7.2A a) in that the design "attempts to reproduce natural hydrologic conditions with respect to ground and surface waters". The project complies with 7.2Ab) in that LID was used to the"maximum extent practicable". LID does not usually apply to individual lots. The concept of LID refers to alternative designs to minimize paving and to avoid the concentration of storm flows by eliminating drainage systems. The development of large commercial or industrial sites and subdivisions are projects in which the application of LID is most beneficial. Driveways must be paved and land must be cleared for houses and septic systems and wells. However,the project does utilize infiltration and super elevated drives to minimize runoff and reintroduce rainfall to the water table. The project complies fully with 7.28 T;\T0652\T0652.08\Docs\Letters�T0652.08_1975 Salem Street Peer Review#4_8-1-2017.docx TWL.� E i i Ms. Rebecca Oldham Lots 1-3 Salem Street— peer Review August 1, 2017 Page 7 of 16 The project complies with 7.2C in that reduction in peak flow rates are accomplished through infiltration through chambers and the detention pond. A review of the HydroCAD report will show that for all but the 100-year storm all of the stormwater is controlled by infiltration. Thus, confirming that infiltration exceeds the requirements of the Mass Stormwater Management Handbook. The project complies with 7.2D in that all the driveway runoff water is filtered through stone before entering the infiltration chambers and entering the ground. The BMPs are sized to accept and retain all but the 100-year storm and therefore far exceed the required water quality volume. of 1/2. inch of runoff. TEC.- TEC disagrees, based on our interpretation of the Land Disturbance Regulations, the Applicant is required to meet the 10 performance standards listed in the Massachusetts 51ormwater Handbook. However, TEC has conducted a review and it appears that the project meets the .10 standards as designed. 19. Section 7,2.B.b-The HydroCAD analysis should be revised to use a Type III storm event. Applicant Response: Revised drainage calculations are included as requested TEC., Comment addressed. 20. Section 7.2.B.c&f-The Applicant should provide a summary of pre- post- rainfall peak rates and volumes. Applicant Response: The summaries are included in the HydroCAD report for each drainage area. As required by c) the post-development peak rates were shown to be less than the pre-development peak rates. As required by item f) the total volume of discharge as well as peak rates were evaluated at each control point. TEC.- Comment partially addressed; it appears that the post-development peak rate for sub- catchment P-5 is higher than the pre-development peak rate. The total area of the sub watershed decreases, however there is a small increase in peak rate due to changing the ground cover from woods to lawn area. Because this is a small area flowing to an internal point, it appears the slight increase will have a negligible effect on drainage patterns. i Applicant Response: Drainage area P-5 is internal to the property and cannot affect offsite flow rates. This comment was adequately addressed in the previous responses. TEC., Comment addressed. P 21, Section 7.2.13A -The post watershed plan is not legible. Proposed conditions must be shown clearly. All key nodes from the HydroCAD analysis should be labeled on the plans. j T,\T0652\TO652.08\bocs\Letters\TO652.06L1975 Salem Street Peer Review#4 8-1-2017.docx i Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review August 1, 2017 Page 8 of 16 Applicant Response; I have included larger drawings for pre and post development drainage plans. TEC.- Comment addressed. 22. Section 7.2.B,e-The Applicant should provide separate HydroCAD files with area totals for pre- & post- development analysis. Applicant Response: The HydroCAD files have been separated as requested and are included with this submittal. TEC.- Comment partially addressed; it appears that the total pre-development and post development areas are not equivalent and several sub-watershed areas are inconsistent when comparing HydroCAD and Watershed plan. Applicant Response: See revised plans and Hydrology report. TEC, The pre-development drainage area is 4.819 acres and the post-development drainage area is 4.747 acres. These drainage maps and HydroCAD should be revised so that the areas are consistent. Applicant Response: The areas have been adjusted to within .008 acres. The existing conditions area is 4.819 acres and the proposed area is 4.811 acres. Considering the amount of reduction in off site flow the difference is insignificant. TEC, Comment addressed 23. Section 7.2.B.k-The hydrologic analysis should be revised to use a maximum sheet flow length of 50 feet. Applicant Response: The 50 ft sheet flow was used in all but two areas. In area P-3A sheet flow was used for 100 feet because it is sheet flow from a driveway and shallow concentrated flow was not appropriate for such a small distance. The distance used in P-1132 was 72 feet and only a minor difference both have been changed to reflect the 50 ft sheet flow, TEC., Comment not addressed, Applicant Response: The previous comment was addressed by changing all sheet flows to 50 feet. See revised hydrology report, TEC., Comment addressed. 24. Section 7.2.0-The Applicant should provide recharge calculations to meet all requirements listed in Section 7.2.C. T:�T0652\T0652.08\Docs\LettersNT0652,08_1975 Salem Street Peer Review#4_8-1-2017.docx ��� j Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review August 1, 2017 Page 9 of 16 Applicant Response: The total impervious pavement on the site is 12,200 square feet. The soil is a Canton which is in the B hydrologic group. Required recharge is .35 inches per square foot of impervious area. Total volume of recharge required is 12,200 s.f. x .3S inches/s.f./12 inches/ft = 355 c.f. The chambers volume plus the void volume of the stone on lot 3 is 658 c.f. The chamber volume plus the stone void volume on the common driveway is 5423 c.f. Total volume provided 6081 c.f. > 355 c.f. requires. The above does not include the infiltration provided by the system design. TEC.• Comment addressed. 25. Section 7.2.D--The Applicant should provide documentation and calculations that all BMPs are designed in accordance with the listed regulations. Applicant Response: The driveways in the areas of the infiltration chambers have a 5 foot wide shoulder of crushed stone that drains into the Stormtech chambers. The stone provides the pretreatment to the stormwater before it enters the chambers. The filter stone in the 5 foot shoulder is not included in the storage stone used in the above calculations. Infiltration provides, by BMP guidelines, 80% removal of TSS. Considering the application of the design system to the driveway it is more than sufficient to meet State regulations (which don't apply to projects of four lots or fewer) and more than sufficient to meet the BMP guidelines. TEC.• Comment addressed. 26. Section 7.2.F—The Applicant should provide landscape design in accordance with this section. Applicant Response: We have added a landscape plan to the design drawings. The majority of the site will remain wooded. The disturbed riverfront area along the drives will be allowed to revegetate to forest. The remainder of the cleared land will be lawn and ornamental planting beds common to new homes in North Andover. Specifics as to the type of grasses, mulch and ornamentals to be placed on each lot will be up to the new home owner or contractor who will build the homes. TEC• The Landscape Plan should be revised to have a consistent hatch for the 'Undisturbed Area — Woodland". Furthermore, the Applicant should clarify how the proposed Areas to be allowed to return to natural vegetation"shall be accomplished, Applicant Response: The legend has been corrected. Notes have been added concerning the"return to natural vegetation. T:\T0652\T0652.08\Dots\Letters\T0652.08_1975 Salem Street Peer Review#4_8-1-2017.docx TEC �, Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review August 1, 2017 Page 10 of 16 TEC, Comment addressed. 27. Section 8.0--The Applicant should provide a separate erosion and sedimentation control plan to meet all requirements in sections 8.1 &8.2. Applicant Response: An erosion and sedimentation control plan has been added to the plan set. TEC.• Comment partially addressed; the Applicant has provided an Erosion and Sedimentation Control Plan; however, there are various sections of Sections 8.1 & 8.2 that are missing from the Erosion and Sedimentation Control Plan, spedfically sections 8,1b), 8.1b)vii, 8.1c)i1 and 82t). Applicant Response: The plans must be taken as a whole and the information required by section 8.1b) is contained in all of the submitted information. Construction sequence and other notations have been added to the Proposed Site Plan to comply with the consultants review. TEC.• Comment addressed. 28,The Applicant should revise the plans to provide silt sacks in all existing catch basins that will receive stormwater runoff from the subject property. Applicant Response: A silt sack was included in the detail sheet and its designated use is the single catch basin shown on the plan. TEC• Comment addressed. 29. Note #7 on sheet 2 states that there is no disturbance within the 100' riverfront area; however, it appears that the Applicant is proposing work within this area. Applicant Response: The note has been corrected. TEC• Comment addressed. 30.The Applicant should provide a legend for all existing and proposed line types, symbols, and hatches, Applicant Response: A legend has been provided. TEG Comment partially addressed; it appears that a legend has been provided, however, there are multiple line types and symbols used on the plans and are not included in the legend. Applicant Response: The plans were adequate for Planning and Conservation review without the legend, l legend has been added and is adequate for the work. T:\T0652\TG652.08\Docs\Lefiters�T0652.08_1975 Salem Street Peer Review*4_8-1-2017.docy TEC Ms. Rebecca Oldham Dots 1-3 Salem Street-- Peer Review August 1, 2017 Page 11 of 16 TEC., Comment addressed. 31. It appears that the Applicant is proposing an increase in peak runoff rates for one of the subcatchments on the subject property; the Applicant should revise the stormwater management system to decrease all proposed peak runoff rates in accordance with Section 7.2.B.c of the North Andover Stormwater Management and Erosion Control Regulations. Applicant Response: The only drainage area increase in peak is to an area within the site. There isn't any requirement within the rules prohibiting increases in flow or rates on one's own properties. There isn't any need to revise the plans as the peer reviewer has requested. TEC.• The peak flow rate and volume to this area is slightly increased over existing conditions. The total area of the sub watershed decreases, however there is a small increase in peak rate due to changing the ground cover from woods to lawn area. Because this is a small area flowing to an internal paint, it appears the slight increase will have a negligible effect on drainage patterns 32,The Applicant should revise the proposed Operation and Maintenance (0&M) Plan to be in compliance with Section 9.0 of the Town of North Andover Stormwater Management and Erosion Control Regulations. Specifically Sections 9.I.a.ii, 9.I.a.iv, 9.I.a.v and 9.I.a.vi. Applicant Response: The O&M plan will be signed by the applicant as required by 9.1a)ii prior to start of construction and with the posting of the bond. The information as required by 9.1a)iv has been provided. Information required by 9.1a)v is included in the submittal. Separate Stormwater easements are not required. The common driveway easement will include the stormwater system in that area. It will be recorded with the plan. TEC. Comment partially addressed, it appears that there is not a designated area on the O&M Plan for signatures The O&M Plan is meant to be a stand-alone document, and therefore a separate plan or map showing the location of the systems should be provided as part of the O&M Plan. Applicant Response: The O&M Plan for post construction BMP maintenance has been modified to include a signature and a map as requested. TEC. Comment addressed. 33. A separate 0&M plan should be provided to meet the requirements of Section 9.0 for the long term maintenance of the permanent storm water management system. Applicant Response: An O&M plan is included TEC.• Comment addressed. T:\T0652\TO652,08\Docs\Letters\T0652,08_1975 Salem Street Peer Review#'_8-1-2017.docx TEC Ms. Rebecca Oldham Lots 1-3 Salem Street-- Peer Review August 1, 2017 Page 12 of 16 34.The Applicant should revise the plans to have consistent line types for resource area buffers and provide all buffers on the plans. Applicant Response: All buffers are on the plan and the 200 ft riverfront line type has been changed. TEC.• Comment addressed. 35. It appears that the potential vernal pool on the subject property is within one hundred (100' feet to the proposed leaching system. The Applicant should revise the plans to provide distances to all property lines and resource areas to ensure compliance with 310 CMR 15,211 of the Department of Environmental Protection. Applicant Response: The Conservation Commission has since determined the potential vernal pool is not a vernal pool but rather an isolated wetland. The septic system as shown is greater than 100 ft from the wetland. TEC• Comment addressed. 36,The Applicant should revise the plans to provide the following details: a. Rip-rap for flared end section; Applicant Response: The riprap detail is on sheet 4 TEC.• Comment addressed. b. Leaching pits; Applicant Response. the leach chambers are on sheet 3 TEC, Comment addressed. c. Septic tank/systems; Applicant Response: details of the septic systems and septic tanks are not need to review this stormwater plan. TEC.• Comment addressed. d. Proposed well; Applicant Response. The location of the wells are on the plans. Details are not needed. TEC.• Comment addressed. T;\T0652\TO652,08\Docs\Letters\T0652,p8_1975 Salem Street Peer Review#4_8-1-2017,doa ' E Ms. Rebecca Oldham Lots 1-3 Salem Street-- Peer Review August 1, 2017 Page 13 of 16 e. Underground utilities; Applicant Response: Underground utility details are not necessary. e i TEC., Comment not addressed. Applicant Response: A detail has been added. TEC., Comment addressed. f. Detention pond; Applicant Response: A detention pond detail has been included. TEC.- Comment addressed. g. Loam & seed detail; Applicant Response: A note has been added to the landscape plan concerning loam and seed. TEC., Comment addressed. h. Roof drain connections; Applicant Response: Roof drains are not being used. TEC,It is unclear what the line type from each of the proposed houses to the infiltration areas represents(u/u). If roof drains are not being proposed; the Applicant should specify how storm water runoff from the roofs will be controlled. Applicant Response: The u/u is underground utilities as stated in the legend. The roof drainage is included in the total impervious area of each catchment area. TEC., Comment addressed. i. Revise the temporary stockpile detail to demonstrate a maximum side slope of 2:1; and Applicant Response: There isn't any need to restrict a temporary stockpile to 2:1. It is not realistic to expect such a requirement to be followed. TEC.- Comment not addressed; Section 8.2r) of the Town of North Andover Stormwater Management and Erosion Controls Regulations specifically states that "Soil stockpiles must he stabilized or covered at the end of each workday. Stockpile side slopes shall not be greater than 2:.1, All stockpiles shall be surrounded by sediment controls" T:\T0652\T0652.08\1)ocs\LettersNT0652.08_1975 Salem Street Peer Review#9 8-1-2017,doCX TEC Ms. Rebecca Oldham Lots 1-3 Salem Street-- Peer Review August 1, 2017 Page 14 of 16 Applicant Response: A 2:1 slope has been added to the detail TEC.• Comment addressed. j. Revise the construction exit detail to comply with MassDEP standards. Applicant Response: There are any standards for construction exits developed by Mass DEP, there are only guidelines. The Construction entrancelexit detail is one we have used for 30 years and has proved to be effective. It is far wider than the state recommends which I consider to be better than the state recommendation. The detail will not be changed. TEC.• Comment not addressed. Applicant Response: The comment was addressed previously and the construction entrance is adequate. TEC.•MassDEP recommends a construction exit that is a minimum of 50 Feet in length for a project of this size(longer construction exits provide better cleaning). The Applicant has provided a construct exit that is 25 feet in length, half the minimum recommended by DEP. The construction exits will playa vital role in keeping sediment off of Salem Street, and out of the resource areas directly adjacent to the street. Both of the proposed construction exits are within the .I DO foot buffer to a resource area Applicant Response: The construction entrance has been lengthened to 50 feet. TEC' Comment addressed. 37.The Applicant should revise the plans and/or the HydroCAD analysis to have consistent culvert sizes. The HydroCAD analysis specifies a 12"x 36"box culvert; however, the plans and details specify a 3'x 5'culvert. Applicant Response: The plan has been revised. TEC.• Comment not addressed. The plan has not been revised, see sheet 3 "Construction Details"for 3 X 5 Concrete Culvert and Rip Rap Apron. Applicant Response: The plan has been revised. TEC.• Comment addressed. 38.The Applicant should revise the HydroCAD analysis to provide a manning n value that resembles straight and clean concrete. The HydroCAD analysis uses a manning n value of 0.009; however, the typical manning n value for the proposed type of culvert should be 0.011. T;\T0652\TO652,08\Docs\Letters\TO652.08_1975 Salem Street Peer Review#4_8-1-2017,doa �� i r i Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review August 1, 2017 Page 15 of 16 i Applicant Response: The manning value has been changed as suggested. TEC.• Comment addressed. i 39.The Applicant should revise the proposed detention basin to provide one (1� foot of freeboard from the peak elevation of the 100-year design storm and the top of the detention basin. Applicant Response: The detention basin has been corrected. TEC.• Comment addressed. 40. It appears that the areas listed on the drainage map do not match up to the areas in the HydroCAD analysis. The Applicant should revise the areas to be consistent, and include the proposed impervious roof runoff in the sub-catchments. Applicant Response: The changes have been made as requested. TEC.• Comment addressed. 41.The"Proposed Conditions Drainage Areas" map should be revised to display the proposed conditions of the development. It is impossible to verify that the subwatershed boundaries are accurate without any grading information or proposed conditions displayed. All labels on the map should match the HydroCAD analysis for cross reference and the map should display the proposed detention pond and subsurface chambers with labels that match the HydroCAD analysis. Applicant Response: The plan has been revised. TEC.- Comment not addressed. The Applicant has not resubmitted "Proposed Conditions Drainage Areas`. 42. Pond 3P is currently modeled in HydroCAD as 1 row of 16 StormTech SC-740 chambers, with the invert of the chambers at elevation 101. Sheet 3 of the Site Plans call for 10 StormTech 310 chambers, which is inconsistent with the HydroCAD. The Site Plan also shows that the driveway is proposed at an elevation of 100 near Salem Street. This would mean that the chambers are above the driveway elevation, which does not make sense. Additionally, the HydroCAD analysis assumes that this system is being installed with a flat bottom, however the driveway grade is approximately 11% and drops 8 vertical feet where the chambers are proposed. The Applicant should provide further detail on the subsurface chambers beyond a general cross section. This level of detail should be provided for the subsurface systems on Lot I & 2 as well to ensure they will function as designed. Applicant Response: The plans have been revised. T:\T0652\T0652.08\Docs\Letters\T0652,08_1975 Salem Street Peer Review#4_8-1-2017.doCX life. Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review August 1, 2617 Page 16 of 16 TEC- Comment not addressed. The number of chambers shown on the plans does not match the number of chambers in the HydroCAD. The plans/HydroCAD should be consistent. Exfrltration Lot 3 Site Plans, Sheet 2 of 4-14 chambers shown on Plan Site Plans, Sheet 3 of 4-14 chambers shown on Plan Site Plans, Sheet 3 of 4- Plan View title reads "USE 10 STORMTECH 740 CHAMBERS" HydroCAD-16 chambers shown in model Exfiltration Lots 1 & 2 Site Plans, Sheet 2 of 4-27 chambers shown on Plan Site Plans, Sheet 3 of 4-27 chambers shown on Plan Site Plans, Sheet 3 of 4-Plan View title reads "USE 38 STORMTECH 740 CHAMBERS" HydroCAD-27 chambers shown in model 43. The construction details for the subsurface infiltration chambers do not show a "water stop': The site plans should be revised to show further detail on the water stop including width, depth, length, and specifically call for the proposed material 44. The proposed contours are not displayed on Sheet 2 of 4 The Site Plans should be revised to show the proposed grading. 45. IfApproved by the Board, the Site Plans will be recorded as an attachment to the decision. The Plans should be submitted in black& white for recording. Please do not hesitate to contact TEC at (978) 794-1792 if you have any questions regarding our comments. Thank you for your consideration. Sincerely, TEC, Inc. "TheEngineeringCorp.com" Peter F. Ellison, P.E. Civil Engineer T:\T0652\T0652,08\©ocs\Letters\TO652.08_1975 Salem Street Peer Review#4—1-2017.dou �� i 65 Glenn Street 169 Ocean Blvd. Lawrence,MA 01843 Unit 101, PO Box 249 Hampton, NH 03842 T:978.794.1792 T:603,601,8154 TheEngineeringCorp.com AMW Rebecca Oldham, Staff Planner July 13, 2017 Town of North Andover Planning Department 1600 Osgood Street North Andover, MA 01845 TEC Ref, T0652,08 Re: Peer Review #3 Land Disturbance Permit Application 1975 Salem Street, North Andover, MA Dear Ms. Oldham: On behalf of the Town of North Andover, TEC, Inc, conducted a technical review of the April, 2017 Land Disturbance Permit Application For the proposed project to be located at 1975 Salem Street. Llvingstoi e Development Corporation ("Applicant's submitted the following documents, which TEC reviewed for conformance with Chapter 160 of the General Bylaws of the Town of North Andover, the North Andover Stormwater Management and Erosion Control Regulations, and the Massachusetts Stormwater Handbook: • Response to Peer Review, 1975 Salem Street, North Andover, MA prepared by Christiansen &Sergi, Inc., dated July 3, 2017; • Site Plan for Special Permit, tots 1-3 Salem Street, North Andover, MA, prepared by Christiansen &Sergi, Inc., dated October 3, 2016, revised December 28, 2016, February 17, 2017, April 7, 2017,June 14, 2017, and July 3, 2017, • Existing Drainage HydroCAD Report, Lots 1-3 Salem Street, North Andover, MA, prepared by Christiansen &Sergi'Inc., dated July 4, 2017; and • Proposed Drainage'HydroCAD Report, Lots 1-3 Salem Street,.North Andover, MA, prepared by Christiansen &Sergi, Inc., dated July 4, 2017, Upon review of the latest submission, TEC compiled the following list of comments. For consistency, the outstanding original comment numbers have been retained from the most recent TEC review letter dated April 26, 2017. The Applicant's response to comments is shown as bold; TEC responses are shown as italic. 1. The Board should note that the Applicant has requested multiple Special Permits from the Town of North Andover zoning Bylaws which have been listed on the plans: a. Section 7.2.1 —Access across street frontage. b. Section 7.2.2—Frontage exception. Applicant Response: We had filed for a common driveway in addition to the / Frontage exception lot and access not through the lot frontage. TEC.• Comment addressed. Plan I Permit ( Design I Construct I' Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review July 13, 2017 Page 2 of 15 2. It appears that the Applicant is proposing work within one hundred (100') feet to resource areas; the Applicant should verify that the project will be permitted with the Conservation Commission, Applicant Response: The project was reviewed by the Conservation Commission and /an Order of Conditions issued by the Commission approving the project. o TEC, Comment addressed. 3. Section 7A - the Applicant should provide a Stormwater Management Plan that meets the requirements of sections 7.1 & 7.2 of the North Andover Stormwater Management and Erosion Control Regulations. Applicant Response: The plans as submitted comply with Section 7.1 and 7.2 of the North Andover Stormwater Management and Erosion Control regulations. Additional summaries, descriptions and modifications as requested by the TEC have been added in the attached plans and reports to supplement the original filing. TEC.•See detalled comments below. 4. Section 7.1.b - The Applicant should include a brief narrative description of the project including how and where stormwater is to be controlled, Applicant Response: This project has been before both the Conservation Commission and the Planning Board for many months and several public hearings were held. Both the Commission and the Board approved the project for the permits requested. The project was described to the Board on numerous occasions including a description of stormwater controls. Not including the project description in this application was an oversight and a description is contained with the submitted information. AEC, Comment addressed. 5. Section 7.1,e-The Applicant should revise the Stormwater Plan to include the size of entire parcel, each drainage area on or to the parcel, and the total square feet of land area subject to disturbance. Applicant Response: The entire parcel consists of three lots and the area of each is on the plan. The entire parcel area of 331,307 s.f. has been added to Sheets. The drainage areas are listed on the drainage plans and the area for each drainage area is listed in the HydroCAD report. I have added the areas to the Drainage Plan to assist the reviewer. We had previously reviewed the total disturbance for a number of alternative designs suggested by the Board. Of those this project offered the least disturbance of the alternatives investigated. The total disturbance has been added to sheet 2. T;\T0652NT0652.08\©ocs\Letters\TO652.08_1975 Salem Street Peer Review#3_7-11-2017.docx AMW TEC' I Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review July 13, 2017 Page 33 of 15 TEC.• Comment addressed 6. Section 7.1.h --The Applicant should clearly label all existing and proposed easements. Note 1 indicates an easement on lot 3. Applicant Response: The proposed drive easement was labeled on sheet 2 of 4. A label has been added to sheet 1. The note has been corrected. f r/ TEC.• Comment addressed, 7. The Stormwater Management Plan should clearly label all three lots. Applicant Response: The lot labels are on sheet 1 (see attached) TEC.• Comment addressed. 8. Section 7.1.i —The plan should include the edge of the existing driveway on the abutting property to the southeast of the project. Applicant Response: The driveway (actually a roadway) was shown on sheet 2. TEC.• Comment addressed. 9. Section 7.1.j —The plan should be revised to label areas of steep slopes between 15-25% and areas of steep slopes over 25%. Also, the plan should include existing topography fifty feet beyond the perimeter of the parcel. Applicant Response: I have added a sheet which contains the required slope information. TEC. Comment partially addressed; the Applicant has provided a Slope Analysis diagram, however, the Applicant has not provided existing togranhy fi feet 6e ony d the perimeter of _ the parcel. Applicant Response: Additional existing topography within 50 feet of the property boundary has been added to the plan adjacent to the onsite topography previously shown. TEC• Comment addressed. 10. Section 7.1.k--The plan should clearly identify and describe all wetland resource areas. Applicant Response. The only wetland resource area on site is a small isolated wetland/vernal pool in the extreme southerly corner of lot 3 as shown on sheet 1. The site lies within the buffer zone of a wetland to the west, a wetland to the east across Salem Street and an isolated wetland along the northerly property line. The low- T:\T0652\T0652,08\Docs\Letters\T0652.08_1975 Salem Street Peer Review#3_7-11-2017.docx TEC Ms. Rebecca Oldham Lots 1-3 Salem Street-- Peer Review July 13, 2017 i Page 4 of 15 portion of the site that borders Salem Street lies within the Riverfront area. All resource areas were identified on the submitted plans. TEC.• Comment addressed. 11. Section 7.1.m - the location, delineation, and description of habitats mapped by the NHESP and also potential and certified vernal pools. Applicant Response: A vernal pool is shown on sheet 1. The parcel is in both priority and estimated habitat area. The proposed work was determined by the NHESP to be /a "no take". (see attached letter from Fisheries and Wildlife) TEC.• Comment addressed. 12. Section 7.1.n - The Applicant should revise the plans to provide the general outline of existing tree line/vegetation and the proposed outline of tree line/vegetation. Applicant Response: The property is fully wooded so that a tree line cannot be shown on the plan. The limit of work labeled on the plan is the proposed tree line. TEC.• Comment not addressed; the proposed limit of work line is not provided on the plan. Applicant Response: The limit of work line was on the original submittal on sheet 2. It was not on sheet 2 on the revised plans submitted June 14,2017 but was clearly indicated on the landscape submitted on that same date. It is shown and labeled on /the Proposed Site Plan submitted herewith. Comment addressed. 13. Section 7.i.o--The plan should show existing septic systems within 100' of property. Applicant Response: There aren't any septic systems within 100 ft of the property 'f TEC,• Comment addressed. 14. Section 7.1.p - The drainage area map should demonstrate the stormwater flow paths. /Applicant Response: The flow paths have been added to the plans TEC.• Comment addressed. 15. Sections 7.1.q&r - A description of the existing soils and estimated seasonal high groundwater elevation should be provided on the plans. � II' T;\T0652\T0652.08\Docs\Letters\T0652.08-1975 Salem Street Peer Review#3_7-11-2017.docx ��� I i I Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review July 13, 2017 Page 5 of 15 Applicant Response: The soil is listed as a Canton. The NRCS data is attached as well as the onsite soil testing results that showed the parent soil to be a loamy sand. Groundwater was not observed. Percolation rates ranged from 1 to 9 min/inch. i TEC.• Comment addressed, however, the Applicant should clearly label the test pits so that the naming convention matches the provided test pit results Applicant Response: The test pits (TP) locations are labeled on the plans. The Soil Evaluator, Steve Erikson labeled them Deep Holes (DH) in the Soils report but labeled them in the field notes as TP. DH and TP are equivalent. ✓TEC. Comment addressed. Further test pits may be required within the proposed leaching field but this will be reviewed and approved by the Board of Health. 16. Section 7.1.0 - The Applicant should include documentation/calculations for the time of concentrations, infiltration rates, culvert capacities and flow velocities used in the hydrologic calculations. Applicant Response: The information requested is contained within the HydroCAD report. TEC.• Comment partially addressed,• the Applicant has not provided documentation/calculaflons for the time of concentrations used in the analysis Applicant Response: The times of concentration for all sub catchments are contained in the HydroCAD report. The length of flow path, slope and CN are all contained in the report and each of these is used to calculate the time of concentration. The capacity of the culvert is also contained in the report. Manual calculations of time of concentration, culvert capacities and flow velocities are not done when those parameters are calculated by a program that is national recognized as being accurate in its development and function. The infiltration rate selected of 4 inches per hour is reasonably conservative considering the percolation rates ranged from i to 9 min/in and the permeability of C horizon of a Carlton soil is 6 to 20 inches per hour. We have provided all that is necessary for a proper hydrologic analysis. ITEC.• Comment addressed. 17. Section 7.1 - The locus map provided should be adjusted to a scale of 1"=800'. Applicant Response: The Locus map has been changed from 400 to 800 scale. V TEC.• Comment addressed. a T;\T0652\T0652.08\Docs\Letters\TO652.08_1975 Salem Street Peer Review#3_7-11-2017,docx ��� i 1 Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review July 13, 2017 Page 6 of 15 i 18. Section 7.2.A-The Applicant should provide documentation that the project meets the requirements listed including how the project will meet the requirements of the Massachusetts Stormwater Handbook, Applicant Response: The reference by the consultant to section 7.2A Low Impact Design is somewhat misplaced. Typically LID design refers to subdivision design that varies from traditional design in that pavement width are minimized, swales are used rather than hard piping and Stormwater is treated throughout the site rather than at one device to which all drainage is directed. Additionally, the Massachusetts Stormwater Handbook does not contain requirements but rather "Guidance"as specified in 7.2Ab) of the North Andover Stormwater Management regulations. E The project, a three lot development meets the requirements of the Massachusetts Stormwater Regulations in that it is only a three lot project and the regulations do not apply to a three lot project. The project utilizes a common drive to minimize pavement, super elevated drives to direct water to stone shoulders and infiltration chambers to recharge to ground water and to reduce peak flow rates. The use of these design components proves the project to be an LID project and one that meets the guidelines of the Massachusetts Stormwater Handbook. TEC. Comment not addressed. Section 7.2 of the Town of North Andover Stormwater Management and Erosion Control Regulations specifically states 'At a minimum all projects subject to a Land Disturbance Permit shall comply with the criteria specifications, and performance standards of the most recent version of the Massachusetts Storm water Management Standards and accompanying Storm water Management Handbook as well the criteria contained herein." Applicant Response: Massachusetts Stormwater Management Standards do not apply to projects of 4 or fewer lots. The project contains only 3 lots and therefore by definition without any controls what so ever complies with Massachusetts Stormwater Standards. The project complies with regulation 7.2A a) in that the design "attempts to reproduce natural hydrologic conditions with respect to ground and surface waters". The project complies with 7.2Ab) in that LID was used to the "maximum extent practicable". LID does not usually apply to individual lots. The concept of LID refers to alternative designs to minimize paving and to avoid the concentration of storm flows by eliminating drainage systems. The development of large commercial or industrial sites and subdivisions are projects in which the application of LID is most beneficial. Driveways must be paved and land must be cleared for houses and septic systems and wells. However, the project does utilize infiltration and super elevated drives to minimize runoff and reintroduce rainfall to the water table. The project complies fully with 7.213 T;\T06521T0652.08\Docs\Letters\T0652.08�1975 Salem Street Peer Review#3_7-11-2017,docx � TIC I Ms. Rebecca Oldham Lots 1-3 Salem Street-- Peer Review July 13, 2017 Page 7 of 15 The project complies with 7.2C in that reduction in peak flow rates are accomplished through infiltration through chambers and the detention pond. A review of the HydroCAD report will show that for all but the 100-year storm all of the stormwater is controlled by infiltration. Thus, confirming that infiltration exceeds the requirements of the Mass Stormwater Management Handbook. The project complies with 7.2D in that all the driveway runoff water is filtered through stone before entering the infiltration chambers and entering the ground. The BMPs are sized to accept and retain all but the 100-year storm and therefore far /exceed the required water quality volume. of 1/2 inch of runoff. TEC. TEC disagrees, based on our interpretation of the Land Disturbance Regulations, the Applicant is required to meet the 10 performance standards listed in the Massachusetts Stormwater Handbook. However, TEC has conducted a review and it appears that the project meets the 10 standards as designed. 19, Section 7.2.B.b—The HydroCAD analysis should be revised to use a Type III storm event. /Applicant Response: Revised drainage calculations are included as requested ✓ TEC., Comment addressed. 20. Section 7.2.B.c&f—The Applicant should provide a summary of pre- post- rainfall peak rates and volumes. Applicant Response: The summaries are included in the HydroCAD report for each drainage area. As required by c) the post-development peak rates were shown to be less than the pre-development peak rates. As required by item f) the total volume of discharge as well as peak rates were evaluated at each control point. TEC., Comment partially addressed; it appears that the post-development peak rate for sub- catchment P-5 is higher than the pre-development peak rate. The total area of the sub watershed decreases, however there is a small increase in peak rate due to changing the ground cover from woods to lawn area. Because this is a small area flowing to an internal point, it appears the slight increase will have a negligible effect on drainage patterns. Applicant Response: Drainage area P-S is internal to the property and cannot affect offsite flow rates. This comment was adequately addressed in the previous responses. •✓TEC• Comment addressed. 21. Section 7.2.13.d —The post watershed plan is not legible. Proposed conditions must be shown clearly. All key nodes from the HydroCAD analysis should be labeled on the plans. T:�T0652\T0652.08\Docs\Letters\T0652.08_1975 Salem Street Peer Review*3_7-11-2017.docx I P Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review July 13, 2017 Page 8 of 15 Applicant Response: I have included larger drawings for pre and post development drainage plans. ✓ TEC- Comment addressed. 22, Section 7.2.B.e—The Applicant should provide separate HydroCAD files with area totals for pre- & post- development analysis. Applicant Response: The HydroCAD files have been separated as requested and are included with this submittal. TEC, Comment partially addressed;it appears that the total pre-development and post- development areas are not equivalent and several sub-watershed areas are inconsistent when comparing HydroCAD and Watershed plan. Applicant Response: See revised plans and Hydrology report, TEC, The pre-development drainage area is 4.619 acres and the post-development drainage area is 4.747 acres These drainage ma s and HydroCAD should be revised so that the areas are consistent. 23. Section 7.2.B.k—The hydrologic analysis should be revised to use a maximum sheet flow length of 50 feet. Applicant Response; The 50 ft sheet flow was used in all but two areas. In area P-3A sheet flow was used for 100 feet because it is sheet flow from a driveway and shallow concentrated flow was not appropriate for such a small distance. The distance used in P-11132 was 72 feet and only a minor difference both have been changed to reflect the 50 ft sheet flow. TEC, Comment not addressed Applicant Response: The previous comment was addressed by changing all sheet flows to 50 feet. See revised hydrology report. ,/ TEC., Comment addressed. 24. Section 7.2.0—The Applicant should provide recharge calculations to meet all requirements listed in Section 7.2.C. Applicant Response: The total impervious pavement on the site is 12,200 square feet. The soil is a Canton which is in the B hydrologic group. Required recharge is .35 inches per square foot of impervious area. Total volume of recharge required is 12,200 s.f. x .35 inches/s,f./12 inches/ft 355 c.f. T:\T0652\T0652.08\Dots\Letters\T0652.08_1975 Salem Street Peer Review#3_7-11-2017,docx TEC' i V I I I Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review July 13, 2017 Page 9 of 15 The chambers volume plus the void volume of the stone on lot 3 is 658 c.f, The chamber volume plus the stone void volume on the common driveway is 5423 c.f. 6 Total volume provided 6081. c.f. > 355 c.f, requires. The above does not include the infiltration provided by the system design. v/TEC.• Comment addressed 25. Section 7.2.D -The Applicant should provide documentation and calculations that all BMPs are designed in accordance with the listed regulations. Applicant Response: The driveways in the areas of the infiltration chambers have a 5 foot wide shoulder of crushed stone that drains into the Stormtech chambers. The stone provides the pretreatment to the stormwater before it enters the chambers. The filter stone in the 5 foot shoulder is not included in the storage stone used in the above calculations. Infiltration provides, by BMP guidelines, 800/n removal of TSS. Considering the application of the design system to the driveway it is more than sufficient to meet State regulations (which don't apply to projects of four lots or fewer) and more than sufficient to meet the BMP guidelines. I 'JTEC., Comment addressed. 26. Section 7.2.F-The Applicant should provide landscape design in accordance with this section, Applicant Response: We have added a landscape plan to the design drawings. The majority of the site will remain wooded. The disturbed riverfront area along the drives will be allowed to revegetate to forest. The remainder of the cleared land will be lawn and ornamental planting beds common to new homes in North Andover. Specifics as to the type of grasses, mulch and ornamentals to be placed on each lot will be up to the new home owner or contractor who will build the homes. TEC., The Landscape Plan should be revised to have a consistent hatch for the 'Undisturbed Area - Woodland': Furthermore, the Applicant should clarify how the proposed Areas to be allowed to return to natural vegetation"shall be accomplished. Applicant Response: The legend has been corrected. Notes have been added concerning the"return to natural vegetation. �TEC• Comment addressed. 27. Section 8,0 -The Applicant should provide a separate erosion and sedimentation control plan to meet all requirements in sections 8.1 & 8.2. i i T,\T0652\T0652.08\Docs\Letters\T0652,08_1975 Salem Street Peer Review#3_7-11-2017,docx I i Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review July 13, 2017 Page 10 of 15 E Applicant Response: An erosion and sedimentation control plan has been added to the plan set. E j TEC.• Comment partially addressed; the Applicant has provided an Erosion and Sedimentation Control Plan;however, there are various sections of Sections 8.1 & 8.2 that are missing from the Erosion and sedimentation Control Plan;specifically sections 8.1b), 8.1b)vii, 8.1c)ii and 8.2t). Applicant Response: The plans must be taken as a whole and the information required by section 8.1b) is contained in all of the submitted information. Construction sequence and other notations have been added to the Proposed Site Plan to comply with the consultants review. i ✓TEC.• Comment addressed 28. The Applicant should revise the plans to provide silt sacks in all existing catch basins that will receive stormwater runoff from the subject property. Applicant Response: A silt sack was included in the detail sheet and its designated use is the single catch basin shown on the plan. •�TEC• Comment addressed. 29. Note #7 on sheet 2 states that there is no disturbance within the 100' riverfront area; however, it appears that the Applicant is proposing work within this area. Applicant Response: The note has been corrected. VITEC.• Comment addressed. 30. The Applicant should provide a legend for all existing and proposed line types, symbols, and hatches. Applicant Response: A legend has been provided. TEC. Comment partially addressed; it appears that a legend has.been provided, however, there are multiple line types and symbols used on the plans and are not included in the legend. Applicant Response: The plans were adequate for Planning and Conservation review without the legend. I legend has been added and is adequate for the work. VITEC. Comment addressed. 31. It appears that the Applicant is proposing an increase in peak runoff rates for one of the subcatchments on the subject property; the Applicant should revise the stormwater T:\T0652\TO652.08�Docs\Letters\T0652.08_1975 Salem Street Peer Review#3-7-11-2017.docx ��� Ms. Rebecca Oldham Lots 1-3 Salem Street-- Peer Review July 13, 2017 j Page 11 of 15 management system to decrease all proposed peak runoff rates in accordance with Section 7.2.B.c of the North Andover Stormwater Management and Erosion Control Regulations. Applicant Response: The only drainage area increase in peak is to an area within the site. There isn't any requirement within the rules prohibiting increases in flow or { rates on one's own properties. There isn't any need to revise the plans as the peer reviewer has requested. TEC.• The peak flow rate and volume to this area is slightly increased over existing conditions The total area of the sub watershed decreases, however there is a small increase in peak rate due to changing the ground cover from woods to lawn area. Because this is a small area flowin to an internal oint it a ears the slight increase will have a negligible effect on drainage patterns. 32. The Applicant should revise the proposed Operation and Maintenance (O&M) Plan to be in compliance with Section 9.0 of the Town of North Andover Stormwater Management and Erosion Control Regulations. Specifically Sections 9.1.a.ii, 9.1.a.iv, 9.1.a.v and 9A.a.vi. Applicant Response: The O&M plan will be signed by the applicant as required by 9.1a)ii prior to start of construction and with the posting of the bond. The information as required by 9.1a)iv has been provided. Information required by 9.1a)v is included in the submittal. Separate Stormwater easements are not required. The common driveway easement will include the stormwater system in that area. It will be recorded with the plan. TEC.• Comment partially addressed; it appears that there is not a designated area on the O&M Plan for signatures. The O&M Plan&meant to be a stand-alone document, and therefore a separate plan or map showing the location of the systems should be provided as part of the O&M Plan. 33. A separate O&M plan should be provided to meet the requirements of Section 9.0 for the long term maintenance of the permanent storm water management system. Applicant Response: An O&M plan is included TEC.- Comment addressed. 34.The Applicant should revise the plans to have consistent line types for resource area buffers and provide all buffers on the plans, Applicant Response: All buffers are on the plan and the 200 ft riverfront line type /has been changed. �/ TEC., Comment addressed. a T:\T0652\T0652.08�Docs\Letters\T0652.08_1975 Salem Street Peer Review#3�7-11-2017.docx ��� V' E i i Ms. Rebecca Oldham Lots 1-3 Salem Street-- Peer Review July 13, 2017 Page 12of15 35. It appears that the potential vernal pool on the subject property is within one hundred (100� feet to the proposed leaching system. The Applicant should revise the plans to provide distances to all property lines and resource areas to ensure compliance with 310 CMR 15.211 of the Department of Environmental Protection. Applicant Response: The Conservation Commission has since determined the potential vernal pool is not a vernal pool but rather an isolated wetland. The septic system as shown is greater than 100 ft from the wetland. AEC, Comment addressed. i 36. The Applicant should revise the plans to provide the following details: a. Rip-rap for flared end section; Applicant Response: The riprap detail is on sheet 4 TEC.• Comment addressed b. teaching pits; Applicant Response: the leach chambers are on sheet 3 v1 TEC.• Comment addressed. c. Septic tank/systems; Applicant Response: details of the septic systems and septic tanks are not need to review this stormwater plan. /TEC• Comment addressed. d. Proposed well; Applicant Response: The location of the wells are on the plans. Details are not needed. �TEC.• Comment addressed. 1, e. Underground utilities; Applicant Response: Underground utility details are not necessary. TEC.• Comment not addressed. f, Detention pond; T;\T0652\T0652.08\Docs\Letters\T0652.08_1975 Salem Street Peer Review#3_7-11-2017.docx life.L.� Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review July 13, 2017 Page 13 of 15 Applicant Response: A detention pond detail has been included. 11TEC.• Comment addressed. g. Loam & seed detail; Applicant Response. A note has been added to the landscape plan concerning loam and seed. TEC. Comment addressed. h. Roof drain connections; Applicant Response: Roof drains are not being used. TEC.•it is unclear what the line type from each of the proposed houses to the infiltration areas represents(u/u). If roof drains are not beinq proposed; the Applicant should specify how storm water runoff from the roofs w 11 be controlled Applicant Response: The u/u is underground utilities as stated in the legend. The roof drainage is included in the total impervious area of each catchment area. / TEC.• Comment addressed. L Revise the temporary stockpile detail to demonstrate a maximum side slope of 2:1; and Applicant Response: There isn't any need to restrict a temporary stockpile to 2:1. It is not realistic to expect such a requirement to be followed. TEC.• Comment not addressed; Section 8.2r)of the Town of North Andover stormwater Management and Erosion Controls Regulations specifically states that "Soil stockpiles must be stabilized or covered at the end of each workday. Stockpile side slopes shall not be greater than 2:1. All stockpiles shall be surrounded by sediment controls" Applicant Response: A 2:1 slope has been added to the detail V TEC.• Comment addressed. j. Revise the construction exit detail to comply with MassDEP standards. Applicant Response: There are any standards for construction exits developed by Mass DEP,there are only guidelines. The Construction entrance/exit detail is one we have used for 30 years and has proved to be effective. It is far wider than the state recommends which I consider to be better than the state recommendation. The detail will not be changed. T:\T0652\T0652.08\Docs\Letters\T0652.08_1975 Salem Street Peer Review#3�7-11-2017.docx ��� i 1 Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review .duly 13, 2017 Page 14of15 TEC• Comment not addressed. Applicant Response: The comment was addressed previously and the construction entrance is adequate. TEC. MassDEP recommends a construction exit that is a minimum of 50 feet in length fora project of this size(longer construction exits provide better cleaning). The Applicant has provided a construct exit that is 25 feet in length, half the minimum recommended by DEP The construction exits will plan a vital role in keepin_g_5 diment off of Salem Street, and out of the resource areas directly adjacent to the street. Both of the proposed construction exits are within the 100 foot buffer to a resource area 37. The Applicant should revise the plans and/or the HydroCAD analysis to have consistent culvert sizes. The HydroCAD analysis specifies a 12"x 36" box culvert; however, the plans and details specify a 3'x 5'culvert. Applicant Response: The plan has been revised. TEC.• Comment not addressed. The plan has not been revised, see sheet 3 °Construction Details-for 3 X 5 Concrete Culvert and Rip Rap Apron. 38. The Applicant should revise the HydroCAD analysis to provide a manning n value that resembles straight and dean concrete. The HydroCAD analysis uses a manning n value of 0.009; however, the typical manning n value for the proposed type of culvert should be 0.011. Applicant Response: The manning value has been changed as suggested. '' TEC,, Comment addressed. 39.The Applicant should revise the proposed detention basin to provide one (1� foot of freeboard from the peak elevation of the 100-year design storm and the top of the detention basin. Applicant Response: The detention basin has been corrected. TEC.• Comment addressed. 40. 1t appears that the areas listed on the drainage map do not match up to the areas in the HydroCAD analysis. The Applicant should revise the areas to be consistent, and include the proposed impervious roof runoff in the sub-catchments. Applicant Response: The changes have been made as requested. AEC- Comment addressed T:�T0652\T0652.08\Docs\Letters\T0652,08_1975 Salem Street Peer Review#3_7-11-2017.docx T�ir� E ! I Ms, Rebecca Oldham Lots 1-3 Salem Street— Peer Review .July 13, 2017 Page 15of15 41. The"Proposed Conditions Drainage Areas" map should be revised to display the proposed conditions of the development, It is impossible to verify that the subwatershed boundaries are accurate without any grading information or proposed conditions displayed. All labels on the map should match the HydroCAD analysis for cross reference and the map should display the proposed detention pond and subsurface chambers with labels that match the HydroCAD analysis. 42. Pond 3P is currently modeled in HydroCAD as 1 row of 16 StormTech SC-740 chambers, with the invert of the chambers at elevation 101. Sheet 3 of the Site Plans call for 10 StormTech 310 chambers, which is inconsistent with the HydroCAD. The Site Plan also shows that the driveway is proposed at an elevation of 100 near Salem Street, This would mean that the chambers are above the driveway elevation, which does not make sense. Additionally, the HydroCAD analysis assumes that this system is being installed with a flat bottom, however the driveway grade is approximately 11% and drops 8 vertical feet where the chambers are proposed, The Applicant should provide further detail on the subsurface chambers beyond a general cross section. This level of detail should be provided for the subsurface systems on Lot 1 & 2 as well to ensure they will function as designed. Please do not hesitate to contact TEC at (978) 794-1792 if you have any questions regarding our comments, Thank you for your consideration. Sincerely, TEC, Inc. 'TheEngineeringCorp,cam" Peter F. Ellison, P.E. Civil Engineer i E 1 T:\T0652\T0652.08\Docs�Letters\T0652.08_1975 Salem Street Peer Review#3_7-11-2017,docx � 65 Glenn Street 169 Ocean Blvd. E Lawrence,MA01843 I U a I t 101, PO Box 249 Ti Hampton, NH 03842 T:978.794.1792 T:643.601.8154 ECTheEngineeringCorp,com Rebecca Oldham, Staff Planner June 28, 2017 Town of North Andover Planning Department 1600 Osgood Street North Andover, MA 01845 TEC Ref, T0652.08 Re: Peer Review #2 Land Disturbance Permit Application 1975 Salem Street, North Andover, MA Dear Ms. Oldham: On behalf of the Town of North Andover, TEC, Inc. conducted a technical review of the April, 2017 Land Disturbance Permit Application for the proposed project to be located at 1975 Salem Street. Livingstone Development Corporation ("Applicant'D submitted the following documents, which TEC reviewed for conformance with Chapter 160 of the General Bylaws of the Town of North Andover, the North Andover Stormwater Management and Erosion Control Regulations, and the Massachusetts Stormwater Handbook: • Response to Peer Review, 1975 Salem Street, North Andover, MA prepared by Christiansen &Sergi, Inc., dated June 14, 2017; • Project Description —Three Lot Development— 1975 Salem Street, prepared by Christiansen 8t Sergi, Inc., not dated; • Operations and Maintenance Plan Construction Phase, 1975 Salem Street, North Andover Mass, prepared by Christiansen &Sergi, Inc., dated April 10, 2017; • Operations and Maintenance Plan Post Construction Phase, 1975 Salem Street, North Andover Mass, prepared by Christiansen &Sergi, Inc., dated June 14, 2017; • Site Plan for Special Permit, Lots 1-3 Salem Street, North Andover, MA, prepared by Christiansen &Sergi, Inc., dated October 3, 2016, revised December 28, 2016, February 17, 2017, April 7, 2017 and June 14, 2017; • Existing Drainage HydroCAD Report, Lots 1-3 Salem Street, North Andover, MA, prepared by Christiansen &Sergi, Inc., dated May 25, 2017; and • Existing Drainage HydroCAD Report, Lots 1-3 Salem Street, North Andover, MA, prepared by Christiansen &Sergi, Inc,, dated June 13, 2017. Upon review of the latest submission, TEC compiled the following list of comments. For consistency, the outstanding original comment numbers have been retained from the most recent TEC review letter dated April 26, 2017. The Applicant's response to comments is shown as bold; TEC responses are shown as italic. 1. The Board should note that the Applicant has requested multiple Special Permits from the Town of North Andover Zoning Bylaws which have been listed on the plans: a. Section 7.2.1 —Access across street frontage. b. Section 7.2.2 — Frontage exception. Plan Permit Design Construct V I Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review j June 28, 2017 Page 2of12 Applicant Response: We had filed for a common driveway in addition to the Frontage exception lot and access not through the lot frontage. TEC, Comment addressed. 2, It appears that the Applicant is proposing work within one hundred (100' feet to resource areas; the Applicant should verify that the project will be permitted with the Conservation Commission. Applicant Response; The project was reviewed by the Conservation Commission and an Order of Conditions issued by the Commission approving the project. TEC.- Comment addressed. I/ 3, Section 7.1 —the Applicant should provide a Stormwater Management Plan that meets the requirements of sections 7.1 & 7.2 of the Borth Andover Stormwater Management and Erosion Control Regulations. Applicant Response; The plans as submitted comply with Section 7.1 and 7.2 of the North Andover Stormwater Management and Erosion Control regulations. Additional summaries, descriptions and modifications as requested by the TEC have been added in the attached plans and reports to supplement the original filing. TEC., See detailed comments below. j 4. Section 7.1.b - The Applicant should include a brief narrative description of the project including how and where stormwater is to be controlled. Applicant Response: This project has been before both the Conservation Commission and the Planning Board for many months and several public hearings were held. Both the Commission and the Board approved the project for the permits requested. The project was described to the Board on numerous occasions including a description of stormwater controls. Not including the project description in this application was an oversight and a description is contained with the submitted information. TEC., Comment addressed. 5. Section 7.1.e—The Applicant should revise the Stormwater Plan to include the size of entire parcel, each drainage area on or to the parcel, and the total square feet of land area subject to disturbance. Applicant Response: The entire parcel consists of three lots and the area of each is on the plan. The entire parcel area of 331,307 s.f. has been added to Sheetx. The drainage areas are listed on the drainage plans and the area for each drainage area T:\T0652\TO652.08\Docs\Letters\TO652.08_1975 Salem Street Peer Review#2_6-28-2017.docx T,fE� I f Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review June 28, 2017 Page 3 of 12 is listed in the HydroCAD report. T have added the areas to the Drainage Plan to assist the reviewer. We had previously reviewed the total disturbance for a number of alternative designs suggested by the Board. Of those this project offered the least disturbance of the alternatives investigated. The total disturbance has been added to sheet 2. TEC: Comment addressed. 6, Section 7.1.h —The Applicant should clearly label all existing and proposed easements. Note 1 indicates an easement on lot 3. Applicant Response: The proposed drive easement was labeled on sheet 2 of 4. A label has been added to sheet 1. The note has been corrected. TEC, Comment addressed. ' 7. The Stormwater Management Plan should clearly label all three lots, Applicant Response, The lot labels are on sheet 1 (see attached) TEC Comment addressed. ' 8. Section 7.1.i —The plan should include the edge of the existing driveway on the abutting property to the southeast of the project. Applicant Response: The driveway (actually a roadway) was shown on sheet 2. TEC: Comment addressed. i 9. Section 7.i.j —The plan should be revised to label areas of steep slopes between 15-25% and areas of steep slopes over 25%. Also, the plan should include existing topography fifty feet beyond the perimeter of the parcel. Applicant Response; It have added a sheet which contains the required slope information. : ( A TEC Comment partially addressed; the Applicant has provided a Slope Analysis diagram., however, the Applicant has not provided existing topography fifty feet beyond the perimeter of the parcel. 10. Section 7.1,k-The plan should clearly identify and describe all wetland resource areas. Applicant Response: The only wetland resource area on site is a small isolated wetland/vernal pool in the extreme southerly corner of lot 3 as shown on sheet 1. The site lies within the buffer zone of a wetland to the west, a wetland to the east across Salem Street and an isolated wetland along the northerly property line. The T.\T0652\To652.08\Docs\Letters\T0652.08_1975 Salem Street Peer Review#2_6-28-2017.docx ��� F I Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review June 28, 2017 Page 4 of 12 portion of the site that borders Salem Street lies within the Riverfront area. All resource areas were identified on the submitted plans. TEC.- Comment addressed. 11. Section 7.1.m -the location, delineation, and description of habitats mapped by the NHESP and also potential and certified vernal pools. Applicant Response: A vernal pool is shown on sheet 1. The parcel is in both priority and estimated habitat area. The proposed work was determined by the NHESP to be a "no take". (see attached letter from Fisheries and Wildlife) TEC: Comment addressed. 12. Section 7.1.n - The Applicant should revise the plans to provide the general outline of existing tree line/vegetation and the proposed outline of tree line/vegetation. Applicant Response: The property is fully wooded so that a tree line cannot be shown on the plan. The limit of work labeled on the plan is the proposed tree line. TEC; Comment not addressed; the proposed limit of work line is not provided on the plan. 13. Section 7.1.o -The plan should show existing septic systems within 100'of property. Applicant Response: There aren't any septic systems within 100 ft of the property TEC., Comment addressed. 14. Section 7.1.p - The drainage area map should demonstrate the stormwater flow paths. Applicant Response: The flow paths have been added to the plans TEC: Comment addressed. 15. Sections 7.1.q&r A description of the existing soils and estimated seasonal high groundwater elevation should be provided on the plans. Applicant Response: The soil is listed as a Canton. The NRCS data is attached as well as the onsite soil testing results that showed the parent soil to be a loamy sand. Groundwater was not observed. Percolation rates ranged from 1 to 9 min/inch. TEC., Comment addressed, however, the Applicant should clearly label the test pits so that the naming convention matches the provided test pit results. , T.\T0652\T0652,08\Oocs\Letters\T0652.08_1975 Salem Street Peer Review#2_6-28-2017.docx ��� E I Ms. Rebecca Oldham Lots 1-3 Salem Street-- Peer Review June 28, 2017 Page 5 of 12 16, Section 7.1.0 - The Applicant should include documentation/calculations for the time of concentrations, infiltration rates, culvert capacities and flow velocities used in the hydrologic calculations. Applicant Response: The information requested is contained within the HydroCAD report. Cry TEC.• Comment partially addressed; the Applicant has not provided documentation/calculations for the time of concentrations used in the analysis. 17. Section 7.1 - The locus map provided should be adjusted to a scale of 1"=800'. Applicant Response: The Locus map has been changed from 400 to 800 scale. TEC• Comment addressed. 18. Section 7.2.A—The Applicant should provide documentation that the project meets the requirements fisted including how the project will meet the requirements of the Massachusetts Stormwater Handbook. Applicant Response: The reference by the consultant to section 7.2A Low Impact Design is somewhat misplaced. Typically LID design refers to subdivision design that varies from traditional design in that pavement width are minimized, swales are used rather than hard piping and Stormwater is treated throughout the site rather than at one device to which all drainage is directed. Additionally, the Massachusetts Stormwater Handbook does not contain requirements but rather "Guidance"as specified in 7.2Ab) of the North Andover Stormwater Management regulations. The project, a three lot development meets the requirements of the Massachusetts Stormwater Regulations in that it is only a three lot project and the regulations do not apply to a three lot project. The project utilizes a common drive to minimize pavement, super elevated drives to direct water to stone shoulders and infiltration chambers to recharge to ground water and to reduce peak flow rates. The use of these design components proves the project to be an LID project and one that meets the guidelines of the Massachusetts Stormwater Handbook. TEC Comment not addressed. Section 7.2 of the Town of North Andover Stormwater Management and Erosion Control Regulations specifically states 'At a minimum all projects subject to a .Land Disturbance Permit shall comply with the criteria specifications, and performance standards of the most recent version of the Massachusetts Stormwater Management Standards and accompanying Stormwater Management Handbook as well the criteria contained herein." 19. Section 7,2.B.b —The HydroCAD analysis should be revised to use a Type III storm event. T;\T0652\T0652,08\Dm\Letters\TO652.08_1975 Salem Street Peer Review#2 6-28-2017.docx ��� Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review .dune 28, 2017 Page 6 of 12 Applicant Response: Remised drainage calculations are included as requested TEC.• Comment addressed. 20. Section 7.2.B.c&f—The Applicant should provide a summary of pre- post- rainfall peak rates and volumes. Applicant Response: The summaries are included in the HydroCAD report for each drainage area. As required by c) the post-development peak rates were shown to be less than the pre-development peak rates. As required by item f) the total volume of discharge as well as peak rates were evaluated at each control point. �. TEC Comment partially addressed; it appears that the post-development peak rate for sub- catchment P-5 is higher than the pre-development peak rate. The total area of the sub watershed decreases, however there is a small increase in peak rate due to changing the ground cover from woods to lawn area. Because this is a small area flowing to an internal point, it appears the slight increase will have a negligible effect on drainage patterns 21. Section 7.2.13.d —The post watershed plan is not legible, proposed conditions must be shown clearly. All key nodes from the HydroCAD analysis should be labeled on the plans. Applicant Response: I have included larger drawings for pre and post development drainage plans. TEC.• Comment addressed 22. Section 7.2.B.e—The Applicant should provide separate HydroCAD files with area totals for pre- & post- development analysis, Applicant Response: The HydroCAD files have been separated as requested and are included with this submittal. TEC Comment partially addressed; it appears that the total pre-development and post- development areas are not equivalent and several sub-watershed areas are inconsistent when comparing HydroCAD and Watershed plan. 23. Section 7.2.B.k—The hydrologic analysis should be revised to use a maximum sheet flow length of 50 feet. Applicant Response: The 50 ft sheet flow was used in all but two areas. In area PM3A sheet flow was used for 100 feet because it is sheet flow from a driveway and shallow concentrated flow was not appropriate for such a small distance. The distance used in P-11132 was 72 feet and only a minor difference both have been changed to reflect the 50 ft sheet flow. TEC.• Comment not addressed, r is a T:\T0652\T0652.08\Docs\Letters\T0652,08_1975 Salem Street Peer Review#2_6.28-2017.docx ��� Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review June 28, 2017 Page 7 of 12 24. Section 7.2.0-The Applicant should provide recharge calculations to meet all requirements listed in Section 7.2.C. Applicant Response: The total impervious pavement on the site is 12,200 square feet. The soil is a Canton which is in the B hydrologic group. Required recharge is .35 inches per square foot of impervious area. Total volume of recharge required is 12,200 s.f. x .35 inches/s.f./12 inches/ft = 355 c.f. The chambers volume plus the void volume of the stone on lot 3 is 658 c.f. The chamber volume plus the stone void volume on the common driveway is 5423 c.f. Total volume provided 6081 c.f. > 355 c.f. requires. The above does not include the infiltration provided by the system design. TEC: Comment addressed. 25. Section 7.2.D -The Applicant should provide documentation and calculations that all BMPs are designed in accordance with the listed regulations. Applicant Response: The driveways in the areas of the infiltration chambers have a 5 foot wide shoulder of crushed stone that drains into the Stormtech chambers.The stone provides the pretreatment to the stormwater before it enters the chambers. The filter stone in the 5 foot shoulder is not included in the storage stone used in the above calculations. Infiltration provides, by BMP guidelines, 800/o removal of TSS. Considering the application of the design system to the driveway it is more than sufficient to meet State regulations (which don't apply to projects of four lots or fewer) and more than sufficient to meet the BMP guidelines. TEC Comment addressed. 26. Section 7.2.F-The Applicant should provide landscape design in accordance with this section. Applicant Response: We have added a landscape plan to the design drawings. The majority of the site will remain wooded. The disturbed riverfront area along the drives will be allowed to revegetate to forest. The remainder of the cleared land will be lawn and ornamental planting beds common to new homes in North Andover. Specifics as to the type of grasses, mulch and ornamentals to be placed on each lot will be up to the new home owner or contractor who will build the homes. TEC.• The Landscape Plan should be revised to have a consistent hatch for the 'Undisturbed Area -- Woodland" Furthermore, the Applicant should clarify how the proposed Areas to be allowed to return to natural vegetation'shall be accomplished. r� L, T:\T0652\T0652.08\Docs\Letters\T0652.08_1975 Salem Street Peer Review#2_6-28-2017.docx ��� E i Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review June 28, 2017 Page 8 of 12 27. Section 8,0 —The Applicant should provide a separate erosion and sedimentation control plan to meet all requirements in sections 8.1 &8.2. Applicant Response: An erosion and sedimentation control plan has been added to the plan set, 'i� 1 TEC., Comment partially addressed; the Applicant has provided an Erosion and Sedimentation Control Plan;however, there are various sections of Sections 8,1 & A that are missing From the Erosion and Sedimentation Control Plan;speciFcally sections 8,lla), 81b)vi, 8 )ianCd 8.2i). 28, The Applicant should revise the plans to provide silt sacks in all existing catch basins that will receive stormwater runoff from the subject property, Applicant Response: A silt sack was included in the detail sheet and its designated use is the single catch basin shown on the plan. TEC, Comment addressed. 29. Note #7 on sheet 2 states that there is no disturbance within the 100' riverfront area; however, it appears that the Applicant is proposing work within this area, Applicant Response: The note has been corrected. TEC., Comment addressed. 30. The Applicant should provide a legend for all existing and proposed line types, symbols, and hatches. Applicant Response: A legend has been provided. TEC., Comment partially addressed; it appears that a legend has been provided, however, there are multiple line types and symbols used on the plans and are not included in the legend. 31, It appears that the Applicant is proposing an increase in peak runoff rates for one of the subcatchments on the subject property; the Applicant should revise the stormwater management system to decrease all proposed peak runoff rates in accordance with Section 7.2.B.c of the North Andover Stormwater Management and Erosion Control Regulations, Applicant Response: The only drainage area increase in peak is to an area within the site. There isn't any requirement within the rules prohibiting increases in flow or rates on one's own properties. There isn't any need to revise the plans as the peer reviewer has requested. T:\T0652\T0652,08\Data\Letters\T0652,08_1975 Salem Street Peer Review#2_6-28-2017,dccx ��� Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review June 28, 2017 Page 9 of 12 ;; A TEC.• The peak flow rate and volume to this area is slightly increased over existing conditions. The total area of the sub watershed decreases, however there is a small increase in peak rate due to changing the ground cover from woods to lawn area. Because this is a small area flowing to an internal point, it appears the slight increase will have a negligible effect on drainage patterns. 32. The Applicant should revise the proposed Operation and Maintenance (0&M) Plan to be in compliance with Section 9.0 of the Town of North Andover Stormwater Management and Erosion Control Regulations. Specifically Sections 9,1.a.ii, 9.1.a.iv, 9,1.a,v and 9.1.a.vi. Applicant Response: The O&M plan will be signed by the applicant as required by 9.1a)ii prior to start of construction and with the posting of the bond. The information as required by 9.1a)iv has been provided. Information required by 9.1a)v is included in the submittal. Separate Stormwater easements are not required. The common driveway easement will include the stormwater system in that area. It will be recorded with the plan. TEC.• Comment partially addressed; it appears that there is not a designated area on the O&M Plan for signatures. The O&M Plan is meant to be a stand-alone document, and therefore a separate plan or map showing the location of the systems should be provided as part of the O&M Plan. 33. A separate 0&M plan should be provided to meet the requirements of Section 9.0 for the long term maintenance of the permanent storm water management system, Applicant Response; An O&M plan is included TEC.• Comment addressed 34. The Applicant should revise the plans to have consistent line types for resource area buffers and provide all buffers on the plans. Applicant Response: All buffers are on the plan and the 200 ft riverfront line type has been changed. TEC.• Comment addressed. 35. It appears that the potential vernal pool on the subject property is within one hundred (100) feet to the proposed leaching system. The Applicant should revise the plans to provide distances to all property lines and resource areas to ensure compliance with 310 CMR 15.211 of the Department of Environmental Protection, Applicant Response: The Conservation Commission has since determined the potential vernal pool is not a vernal pool but rather an isolated wetland. The septic system as shown is greater than 100 ft from the wetland. T;\T0652\TO652.08\Docs\Letters\TO652.08_1975 Salem Street Peer Review#2j-28-2017,docx Amu i I I i I i Ms. Rebecca Oldham Lots 1-3 Salem Street- Peer Review June 28, 2017 Page 10 of 12 TEC.• Comment addressed. 36. The Applicant should revise the plans to provide the following details; a. Rip-rap for flared end section; Applicant Response: The riprap detail is on sheet 4 TEC.• Comment addressed. b. Leaching pits; Applicant Response: the leach chambers are on sheet 3 TEC.• Comment addressed. c. Septic tank/systems; Applicant Response: details of the septic systems and septic tanks are not need to review this stormwater plan. TEC Comment addressed, v' d. Proposed well; Applicant Response: The location of the wells are on the plans. Details are not needed. TEC.• Comment addressed. e. Underground utilities; Applicant Response: Underground utility details are not necessary. TEC• Comment not addressedy f. Detention pond; Applicant Response: A detention pond detail has been included. TEC.• Comment addressed. g. Loam &seed detail; Applicant Response: A note has been added to the landscape plan concerning loam and seed. T:\T0652\T0652,08\Docs�Letters\T0652.08_1975 Salem Street Peer Review#2_6-28-2017.docx ARM i Ms. Rebecca Oldham Lots 1-3 Salem Street— peer Review June 28, 2017 Page 11of12 TEC.• Comment addressed. h. Roof drain connections; Applicant Response: Roof drains are not being used. r, TEC.•It is unclear what the line type from each of the proposed houses to the infiltration areas representsu u . If roof drains(/� are not bung proposed; the Applicant should specify how stormwater runoff from the roofs will be controlled. i. Revise the temporary stockpile detail to demonstrate a maximum side slope of 2;1; and Applicant Response: There isn't any need to restrict a temporary stockpile to 2:1. It is not realistic to expect such a requirement to be followed. TEC,• Comment not addressed;Section 8.2r)of the Town of North Andover Stormwater Management and Erasion Controls Regulations specifically states that "soil stockpiles must he stabilized or covered at the end of each workday. Stockpile side slopes shall not be greater than 2.1. All stockpiles shall be surrounded by sediment controls. 0 j. Revise the construction exit detail to comply with MassDEP standards, Applicant Response. There are any standards for construction exits developed by Mass DEP, there are only guidelines. The Construction entrance/exit detail is one we have used for 30 years and has proved to be effective. It is far wider than the state recommends which I consider to be better than the state recommendation. The detail will not be changed. TEC.• Comment not addressed. TEC has also identified the following additional comments from the revised information submitted by the Applicant. 37.The Applicant should revise the plans and/or the HydroCAD analysis to have consistent culvert sizes. The HydroCAD analysis specifies a 12"x 36" box culvert; however, the plans and details specify a Y x 5'culvert. 38. The Applicant should revise the HydroCAD analysis to provide a manning n value that resembles straight and clean concrete. The HydroCAD analysis uses a manning n value of 0,009; however, the typical manning n value for the proposed type of culvert should be 0.011. 39.The Applicant should revise the proposed detention basin to provide one (1' foot of freeboard from the peak elevation of the 100-year design storm and the top of the detention basin. i T:NT0652\T0652.08\Docs\Letters�T0652.08_1975 Salem Street Peer Review#2_6-28-2017.docx TEC i f Ms. Rebecca Oldham Lots 1-3 Salem Street— Peer Review June 28, 2017 Page 12 of 12 40. It appears that the areas listed on the drainage map do not match up to the areas in the HydroCAD analysis. The Applicant should revise the areas to be consistent, and include the proposed impervious roof runoff in the sub-catchments. Please do not hesitate to contact TEC at (978) 794-1792 if you have any questions regarding our comments, Thank you for your consideration. Sincerely, TEC, Inc, "TheEngineeringCorp,cam" Peter E. Ellison, P,E, Civil Engineer T;\T0652\T0652.08\Docs\Letters\T0652.08_1975 Salem Street Peer Review#2_6.28-2017.docx TES i