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HomeMy WebLinkAbout2015-12-17 Stormwater The, M6rrn-Cameron........... o�.5�` _ 1 3 1,, January 20, 2015 NORTH ANOOVER Or La N T NNINGDEPARTMEN North Andover Planning Board 1600 Osgood Street / North Andover, MA 01845 Re: Bake'n Joy Foods, 351 Willow Street South Response to Eggleston Environmental Dear Board Members: Please find enclosed revised plans, calculations, a revised Construction Pollution Prevention Plan and a revised Long Term Pollution Prevention Plan. This information has been prepared to address comments raised by Eggleston Environmental in their project review letter dated, December 8, 2014, comments raised at the Planning Board meeting on December 161h and at the Conservation Commission meeting held on December 3rd. Ms. Eggleston's review is based on information submitted by The Morin-Cameron Group, Inc. (MCG) to obtain Special Permits for the construction of a building addition, additional parking and associated drainage at the above referenced facility. The following numbered responses coincide with the numbered comments in Ms. Eggleston's review letter. For ease of reference Ms. Eggleston's comments are included, in italics, with our response. 1. As is required by DEP Standard 1, discharge calculations are needed to demonstrate that the outlet of the new infiltration/detention basin is appropriately designed to prevent scour. A design detail for the stone apron is also needed. Discharge calculations have been prepared, find attached, to demonstrate that discharge over the spillway from the infiltration basin will not cause scouring at the spillway crest or further down slope beyond the rip-rap protection. The maximum velocity of flows from the spillway has been calculated to be 1.35 ft/sec during the 100 year storm event. Data published in "Fundamentals of Engineering Design", Department of Reclamation and US Army Corps of Engineers indicate that damaging scour starts at about 3.0 ft/sec on average soils and 6.0 ft/sec on Sedimentary Rock. A design detail for the stone apron has also been added to the design plans. 2. The hydrologic analysis is based on 1986 rR-55 data, with a 100 yrstorm volume of 6.5 inches. This is consistent with the DEP 5tormwater Handbook and current North Andover regulations; however, it is not reflective of current climatology. Based on extreme precipitation tables from the Northeast Regional Climate Center's precip.net website, the 100 yr 24-hr storm volume for North Andover should be 8.79 inches. While this larger storm volume does not have to be fully mitigated, it should at least be evaluated to more realistically assess the impacts of the proposed project. CIVIL ENGINEERS • LAND SURVEYORS • ENVIRONMENTAL CONSULTANTS • LAND USE PLANNERS 447 Boston Street (U.S. Route 1), Topsfield, MA 01983 978.887.8586 FAX 978.887.3480 Providing Professional Services Since 1978 www.morincameron.com i I North Andover Planning Board Page 2 January 20, 2015 For demonstration purposes only, MCG has re-run the hydrologic analysis utilizing the 100 year rainfall (8.79 inches) shown in the Northeast Regional Climate Center's precip.net website. The analysis produced a total runoff at Design Point #1, North wetlands, of 19.99 cfs post developed and 18.46 cfs pre developed (see calculations attached). The minor increase in the flow rate to the design point should not have any adverse impacts to the resource area or surrounding areas. The runoff is contained within the existing and proposed drainage basins. As expected there is attenuation in the existing drainage system, however, the surcharge is contained within the drainage system itself and within the existing low areas of the existing parking area. In addition, flows from the new parking area are contained by the two new catchbasins and discharge does not overflow the ramps to the existing parking/ loading area. 3. Per the attached photo, the existing detention pond contained a good deal of standing water at the time of my visit. According to National Climatic Data Center records there was just under 0.5 inches of rainfall in the area within the preceding 72 hours and the water level in the basin appeared to be commensurate with the adjacent wetlands, hence l question whether the basin fully drains between storm events. A permanent pool does enhance the stormwater treatment provided by the basin; however, it also depletes the storage available for flow attenuation and would need to be factored into the drainage calculations. We have seen the existing detention basin dry on several occasions so it appears the basin will drain between storm events. By examining the original drainage calculations you will see that the flood elevation of the basin is the same for the pre and post developed conditions for the 2, 10 & 100 year storm events. This calculation shows that the existing basin will operate the same in the post developed condition as the pre developed condition. Therefore, if the basin holds some water between significant rain events the post developed condition will operate the same as the existing condition which has not proven to have any adverse impacts. 4. The proposed plan calls for runoff from the new parking lot to be delivered to the infiltration basin via a closed drainage system, and for the basin to attenuate runoff flows from large storm events. It needs to be demonstrated that the system is designed to allow runoff flow from all design storm events into the catchbasins and conveyed through the closed system, rather than backing up and flowing down the driveway ramps onto the lower parking area. The closed drainage system in the upper parking lot has been designed such that there will be neither backup nor overflow down the ramps to the existing parking/loading area. We have investigated two conditions to show this. The first is back-up from the sediment forebay through the 12 inch discharge line to the catchbasins. The maximum water level in the catchbasin during a 100 year event is elevation 258.7 with a catchbasin rim elevation of 260.5. Secondly, MCG evaluated the discharge capacity of the two cathhbasin inlets, We are calling for the use of Neenah R-2500G catchbasin frames and grates. The differential between the rim and overflow to the ramps is 0.2 FT. The 100 year discharge from the new parking area is 1.8 CFS. At this low head the grates will North Andover Planning Board Page 3 January 20, 2015 function under weir control, Calculations indicate that each grate has a capacity of 1.85 CFS immediately before overtopping to the ramps; therefore, the total capacity of the two catchbasin grates is 3.7 CFS well above the generated 1.8 CFS, Either of the proposed grates could handle the 100 year flow should the other grate be blocked. The maximum head at each grate will be 0.12 FT during the 100 year event. Even when using a value of 8.79 inches of runoff for the 100 year event, see item 2 above, the total flow to the catchbasins is 2.44 CFS, As pointed out above the catchbasin rims combined have an inlet capacity of 3.7 CFS so they will handle the flow generated if the larger number was used. The capacity of the proposed drain pipe discharging to the sediment forebay exceeds the 1.8 CFS generated during the 100 year event. S. It is not clear from the grading plan that runoff from the driveway ramps to the new parking area would drain to the onsite catchbasin and not directly toward the wetland, The existing edge of pavement is not curbed. The site is relatively flat in this area with a shallow divide just to the North of the paving. We will install a Cape Cod Berm for about 120 ft along the edge of the existing pavement to insure that flows coming from the driveway ramps do not enter the adjacent wetlands but are directed towards the existing catchbasin. 6. It is also not clear from the grading plan that the runoff from the pavement areas to the west and southwest of the proposed building addition would drain to the new catchbasin at the opposite corner of the building and not get trapped in the proposed ramp or dumpster area. There is a high point at the southwest corner of the existing building that causes runoff to travel northerly along the building to the parking area and subsequently to the existing catchbasins. The proposed drainage and grading mimics the existing conditions, We have Indicated the highpoint on the proposed site plan and added additional spot grades to show that runoff will be directed to the new catchbasin. 7. The design detail on Sheet 4 calls for the bottom of the infiltration basin to have a minimum bottom area of 1,700 sf, which appears to be consistent with the area shown on the plan. It is not clear, therefore, why the hydrologic analysis assumes a bottom area of 2,280 sf, and the drawdown analysis uses an even larger bottom area for the basin. The sediment forebay can be included in the storage volume of the basin, however no exfiltration should be assumed over the bottom of the forebay since its function is to trap and accumulate sediment. Exfiltration should be calculated over the bottom area (not surface area) of the infiltration basin only. The bottom of the proposed infiltration basin has an area of 1,700 SF The bottom of the combined sediment forebay/infiltration basin has an area of 2,280 SF, Different areas were utilized to satisfy various standards, For infiltration recharge only the 1,700 SF was utilized. For attenuation storage and to calculate drawdown the combined sediment forebay/infiltration basin was utilized. However, as pointed out by Ms. Eggleston, the 3 'I North Andover Planning Board Page 4 January 20, 2015 bottom of the forebay should not be used when calculating exfiltration or in the drawdown calculations. The attached calculations have been revised to reflect this. For drawdown calculations the average surface area was used which did not include the bottom of the forebay. We have also modeled the infiltration basin with no exfiltration for all storm events find calculations attached); the calculations show that without exfiltration flow to Design Point 1 is mitigated for the 2, 10 and 100 year events and the pond still has a minimum of one foot of freeboard during the 100 year event. 8. The outlet for the proposed infiltration basin is modeled as a broad-crested rectangular weir 5-ft long with a 5-ft breadth, This is not consistent with the design detail, which shows the overflow weir as being 10-ft long and 5-ft in breadth. It is also not clear from the detail that the spillway "weir"is rectangular versus trapezoidal. The proposed trapezoidal broad-crested weir is 5 Ft long with a 5 FT breadth and 3 to 1 side slopes. The detail and hydrology model have been corrected to reflect this. 9. Standard 3 of the DEP Standards calls for projects to provide compensatory stormwater recharge on an average annual basis. The recharge volume provided should therefore be calculated on the basis of the total capture/dead storage volume in the infiltration basin, not the volume infiltrated during the infrequent 2 yr design storm. The required groundwater recharge volume is 355 CF. The recharge volume provided, not including the volume within the forebay, is 3,794 cf (see revised stormwater management calculations attached). 10, Based on the test pit log for TP14-3 there is an existing 66-inch layer of fill in a portion of the proposed infiltration basin footprint All such fill will need to be removed prior to system installation. A note has been added to the plans stating that during the construction of the infiltration basin/sediment forebay the excavation shall extend into existing parent soil to ensure that all topsoil, subsoil and fill material has been removed. The excavated material shall be replaced with clean, well graded sand or gravel. The soil test pit data has been added to the site plans. 11. TSS calculations are needed for the increased impervious area and new pavement behind the existing building. (f it can be demonstrated that the existing detention pond either functions as a wet pond and/or retains the water quality volume, the existing treatment train would meet the 80965 TSS removal requirement with the addition of the Vortsentry unit to provide pretreatment, The proposed development reduces the amount of pavement discharging to the existing detention basin by approximately 5,080 sf. Additional roof area (i.e.: clean runoff) is proposed to discharge to the existing basin, however, the drainage calculations show that the proposed changes in the runoff subcatchment result in the existing basin operating almost identical to the existing conditions. Therefore, by reducing the amount of pavement discharging into the existing basin we have automatically reduced the amount of TSS discharging to the basin. For i i North Andover Planning Board Page 5 January 20, 2015 additional treatment we are proposing a Vortsentry unit on tine (using a 25% TSS removal rating) to provide additional treatment. Calculations attached show that by reducing the amount of pavement, and adding the Vortsentry we are improving the TSS removal by approximately 26% from the existing conditions. 12. Per DEP requirements, the proposed Vortsentry unit should be sized for the water quality volume for the tributary area on an equivalent flow basis, and should be placed in an offline configuration. The Vortsentry unit was sized based on the amount of pavement discharging to it which is included in the original drainage report. We have chosen to use the lower TSS removal of 25% for the unit being installed in-line. As stated above the TSS removal improves by approximately 26% by reducing the amount of impervious area discharging to the basin and installing the Vortsentry. I 13. The new catchbasin to the north of the proposed addition,should also be placed in an offline configuration. Roof drainage and any existing piping that is not being abandoned should be connected directly to a new drain manhole. The proposed catchbasin has been placed off tine and a proposed manhole has been added to intercept the roof drainage and any other existing piping. 14. The design detail for the new catchbasin should specify a minimum 4-foot sump and the type of outlet hood proposed The catchbasin detail has been revised to show a 48" sump and the use of the "Eliminator" for an outlet hood. 15. Detail Sheet 4 includes notes for a level spreader, but there is no accompanying design detail. The infiltration system detail only shows a stone apron without a level spreader. The proposed design plans do not incorporate the use of a level spreader so those notes have been removed. 16. A design detail is needed for the emergency spillway. The proposed infiltration basin does not include an emergency spillway since the only outlet is the spillway. Additional dimensions have been added to the plan to clarify the spillway. 17. A design detail is needed for the forebay berm. It is unclear whether the "6"12"crushed stone berm"label on the infiltration basin detail pertains to the size of the stone or the height of the berm since the detail does specify a top invert for the berm 12 inches above the bottom of the forebay. 1 also note that the top of the forebay berm is only b inches below the outlet elevation of the basin, thus providing relatively little time during a runoff event between the forebay berm being overtopped and the basin beginning to discharge. If it is consistent with the North Andover Planning Board Page 6 January 20, 2015 forebay volume required, 1 would suggest lowering the forebay berm to facilitate the distribution of flow in the basin and allow more time for the flow to infiltrate. A new detail of the weir has been provided indicating that the referenced 6" to 12" stone is the size of the stone to be utilized in the construction of the weir. The overflow section of the sediment forebay has been lowered by 0.5 FT to a new proposed elevation of 257.5 FT. The new volume behind the weir provides 330 CF of storage and satisfies the required storage from the new parking area of 307 CF. 18. The Construction Period Pollution Prevention Plan calls for a silt fence sediment barrier around the limit of work and a detail for the silt fence is provided on the plan. The Conservation Commission may want to consider requiring additional erosion and sediment controls, such as straw wattles, inlet protection for existing catchbasins, and measures to prevent sediment tracking onto paved areas of the site. a We have had one meeting with the Conservation Commission, and the idea of the need for additional erosion controls did not come up. We have discussed this issue with the Conservation office and we have revised the plans to show additional erosion controls in the form of the filter sock backed with silt fence in several areas where the proposed work is close to the wetlands. The Construction Period Pollution Prevention Plan proposes the use of silt sacks in the existing and proposed catchbasin structures, Additional notes have been added to the plan to reflect this. Street sweeping is proposed to minimize tracking of sediment on the site and has been added to the "Construction Period Pollution Prevention Plan" under the section "Dust Control & Sediment Tracking" (find enclosed). 19. The plan shows a designated snow storage area at the southern end of the new parking lot within 50 feet of the wetland. 1 recommend moving the snow storage to the western edge of the lot, outside of the bufferzone. This item was also raised by the Conservation Commission, but they did not require that the snow stockpile area be removed completely from the buffer zone. The proposed snow stockpile area has been relocated to the westerly side of the proposed parking area. The closest point from the wetland to the snow stockpile area is approximately 70 feet. 20. 1 have the following additional comments on the Long Term Pollution Prevention Plan: • Catchbasins and hydrodynamic separators should be cleaned a minimum of once per year. Cleaning of the separator will require a vacuum truck. • The plan should be integrated with the LTPPP/O&M Plan for the entire Bake N Joy property. • The Plan should include a simple figure showing the locations of the BMPs to be j maintained. A revised Long Term Pollution Prevention Plan is enclosed which incorporates atl comments above. North Andover Planning Board Page 7 January 20, 2015 21. The Illicit Discharge Compliance Statement submitted with the plan does not address existing discharges from the building. At a minimum, the existing closed drainage system should be inspected to verify that the system receives storm drainage only. The Illicit Discharge Compliance Statement provided states that I have not witnessed nor am I aware of any existing illicit discharges at the site. This is based on site inspections and discussions with Bake'n Joy. During the Planning Board meeting held on December 161" Mrs, Prochniak, who is an abutter to the south west located at 24 Kathleen Drive, Andover, expressed concern regarding the removal of the berm. As discussed at the Board meeting, the uses at the facility that led to the construction of the berm no longer exist. Bake'n Joy has always tried to work with their abutters over the years; in an effort to replicate the berm, a 6 foot high stockade fence is proposed on the west side of the proposed addition. The top elevation of the existing berm in this location is approximately 271 feet. The top of the proposed fence ranges from 270 feet to 274 feet, A fence is not proposed around the new proposed parking area as it is expected that the second shift, which employs approximately 50 people, will be utilizing the 98 parking spaces in the front of the building. I believe this additional information addresses the comments by Eggleston Environmental as well as comments raised during the Planning Board and Conservation Commission meetings. We look forward to meeting with the Board to further discuss this project, If you have any questions prior to the meeting please do not hesitate to contact me. Sincerely, THE MORIN-CAMERON GROUP, INC. John M. Morin, PE Principal Attachments JMM/kmm cc: Bake'n Joy Foods, Inc. Lisa Eggleston North Andover Conservation Commission DEP F:1N eve MorinSC\SDP\Bake N}oy\Proposed Addition-Rear twest) 2014\response letter I.docx The M6rin-Cameron PROJECT ADDRESS JG Y • SHEET NO. OF CIVIL ENGINEERS I ENVIRONMENTAL CONSULTANTS CALCULATED BY DATE �W LAND SURVEYORS ILAND USE PLANNERS CHECKED BY DATE 447 Boston Street, Rte. 1, Topsfield, MA01983 P: 978-887-8586 • F: 978-887-3480 JOB NO. CLIENT www.morincameron.com c V 1 YI a` [ye [ . I S � s A dr M a 7 P C) , /16 G i ®. f a� a BPI `. LA ci 1 �,�- � , � I The PROJECT ADDRESS Lorin-Cameron SHEET NO, OF CIVIL ENGINEERS 1 ENVIRONMENTAL GONSULTANTS CALCULATED BY DATE LAND SURVEYORS I LAND USE PLANNERS CHECKED BY DATE 447 Boston Street, Rte. 1, Topsfield, MA 01983 P: 978-887-8586 • F: 978-887-3480 JOB NO. CLIENT www.morincameron.com fqAj ( - 2- C4 + A I a I � $ - & v The M6rin-Cameron PROJECT ADDRESS SHEET NO. 13 OF CIVIL ENGINEER5 I ENVIRONMENTAL CON5ULTANTS CALCULATED BY DATE LAND 5LIRVEYOR5 I LAND 05E PLANNER$ CHECKED BY DATE 447 Boston Street, Rte. 1, Topsfieid, MA 01983 P: 978-887-8586 • F: 978-887-3480 JOB NO, CLIENT www.morincameron.com X au v r v (170'_ jc' k"I CIO 1 f-krk e T 2 6 c (q al V t ci oa 4> - I t. L: x j u - aS __ �9 e., .. ei The 1V16rin-Cameron PROJECT ADDRESS, SHEET NO. "' OF CIVIL ENGINEERS I ENVIRONMENTAL CONSULTANTS CALCULATED BY DATE LAND SURVEYORS I LAND USE PLANNERS CHECKED BY DATE 447 Boston Street, Rte. 1, Topsfield, MA 01983 P: 978-887-8586 • F: 978-887-3480 JOB NO. CLIENT www.morincameron.com 3 „.-( `° — 61 v 00 r le w. , .. Ott ( _ iv 1 41 e tv ft } t y i � 4 ' V � i I FoF VEL_oc_ +T Y CALcUL.A-r toti1S Bake N Joy - Post Developed Type III 24-hr 100-Year Rainfall=6.50" 3 Prepared by The Morin-Cameron Group, Inc. Printed 1/16/2015 i HydroCADO 10.00 s/n 00401 ©2011 HydroCAD Software Solutions LLC Summary for Pond Inf. Sediment Forebayl Infiltration Basin [81]Warning: Exceeded Pond park by 0.34' @ 19,99 hrs Inflow Area = 0.689 ac, 47.90% Impervious, Inflow Depth > 4.61" for 100-Year event Inflow = 3.10 cfs @ 12.09 hrs, Volume= 0.227 of Outflow - 1.20 cfs @ 12.32 hrs, Volume= 0.131 af, Atten= 61%, Lag= 14.2 min Discarded = 0,03 cfs @ 12.32 hrs, Volume= 0.028 of i Primary - .18 cfs @ 12.32 hrs, Volume= 0.103 of Routing by Stor-Ind method, Time Span= 0.01-20.00 hrs, dt= 0.01 hrs Peak Elev= 258.56' @ 12.32 hrs Surf.Area=4,139 sf Storage=4,780 cf Plug-Flow detention time= 156.2 min calculated for 0.131 of(58% of inflow) Center-of-Mass det. time= 68.2 min ( 812.5- 744.3) Volume Invert Avail.Stora a Storage Description #1 257.00' 10,484 cf Custom Stage Data (Conic) Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) - (sq-ft) (cubic-feet) (cubic-feet) _ (sg-ft) 257.00 2,280 0 0 2,280 268.00 3,184 2,719 2,719 3,203 259.00 4,961 4,040 6,759 4,994 259.70 6,690 3,725 10,484 6,745 Device Routing Invert Outlet Devices #1 Discarded 257.00' 0.270 inlhr Exfiitration over Surface area #2 Primary 268.40' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 Width (feet) 5,00 11.00 Qiscarded OutFtow Max=0.03 cfs @ 12.32 hrs HW=258.56' (Free Discharge) z-1=Exfiitration (Exfiltration Controls 0.03 cfs) Primary OutFiow Max=1.18 cfs @ 12,32 hrs HW=258.56' (Free Discharge) t-2=Custom Weir/Orifice (Weir Controls 1.18 cfs @ 1.30 fps) 10C E A R 100 Year Storm (8.79 in) Bake N Joy - Pre Developed Type 11124-hr Rainfall=8.79" Prepared by The Morin-Cameron Group, Inc. Printed 1/19/2015 HydroCADO 10.00 s1n 00401 0 2011 HydroCAD Software Solutions LLC Page 1 Summary for Reach DPI: North wetlands i Inflow Area = 2.862 ac, 50.67% Impervious, Inflow Depth > 6.64" Inflow - 18.46 cfs @ 12.11 hrs, Volume= 1.583 of Outflow = 18.46 cfs @ 12.11 hrs, Volume= 1.583 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 1.00-20.00 hrs, dt= 0.05 hrs 7 Summary for Pond Det Pd., Detention Pond Inflow Area = 1.864 ac, 77.79% Impervious, Inflow Depth > 7.53" Inflow - 14.88 cfs @ 12.08 hrs, Volume= 1.169 of Outflow - 14.83 cfs @ 12.09 hrs, Volume= 1.154 af, Atten= 0%, Lag= 0.7 min Primary - 14.83 cfs @ 12.09 hrs, Volume= 1.154 of Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 249.67' @ 12.09 hrs Surf.Area= 1,299 sf Storage= 1,328 cf Plug-Flow detention time= 13.6 min calculated for 1.151 of(98% of inflow) Center-of-Mass det. time= 7.9 min ( 739.5- 731,6) Volume Invert Avail.Storage Storage Description #1 247.60' 4,545 cf Custom Stage Data (Prismatic) Listed below(Recalc) - Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 247.50 0 0 0 248.00 224 56 56 250.00 1,510 1,734 1,790 251.00 4,000 2,755 4,545 Device Routing Invert Outlet Devices #1 Primary 249.00' 10.0' long x 10.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64 Primary OutFlow Max=14.65 cfs @ 12.09 hrs HW=249.67' (Free Discharge) t-1=Broad-Crested Rectangular Weir (Weir Controls 14.65 cfs @ 2.20 fps) i E 100 Year Storm (8.79 in) Bake N Joy - Post Developed Type It!24-hr Rainfall=8.79" Prepared by The Morin-Cameron Group, Inc. Printed 1/19/2015 HydroCAD®10.00 sln 00401 O 2011 HydroCAD Software Solutions LLC Page 2 Summary for Reach DPI: North wetlands Inflow Area = 2.935 ac, 63.84% Impervious, Inflow Depth > 6,54" Inflow 19.99 cfs @ 12.12 hrs, Volume= 1.598 of Outflow = 19.99 cfs @ 12.12 hrs, Volume= 1.598 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.01-20.00 hrs, dt= 0.01 hrs Summary for Pond Det Pd: Existing Detention Pond Inflow Area = 1,948 ac, 81.69% Impervious, Inflow Depth > 7,64" Inflow = 15.21 cfs @ 12.10 hrs, Volume= 1.240 of Outflow - 15.10 cfs @ 12.11 hrs, Volume= 1.226 af, Atten= 1%, Lag= 0.7 min Primary - 15.10 cfs @ 12,11 hrs, Volume= 1,226 of Routing by Stor Ind method, Time Span= 0.01-20.00 hrs, dt= 0.01 hrs Peak Elev= 249.68' @ 12.11 hrs Surf.Area= 1,304 sf Storage= 1,339 cf Plug-Flow detention time= 13.0 min calculated for 1.225 of(99% of inflow) Center-of-Mass dot. time= 7.7 min ( 737.6- 729.9} Volume Invert Avail.Stora a Storage Description #1 247.50' 4,545 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store feet s -ft cubic-feet cubic-feet 247.50 0 0 0 248.00 224 56 56 250.00 1,610 1,734 1,790 251.00 4,000 2,755 4,545 Device Routing Invert Outlet Devices #1 Primary 249.00' 10.0' long x 10.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.49 2.56 2.70 2,69 2.68 2.69 2.67 2.64 Primary OutFlow Max=15.10 cfs @ 12.11 hrs HW=249.68' (Free Discharge) t-1=Broad-Crested Rectangular Weir (Weir Controls 15.10 cfs @ 2.22 fps) Summary for Pond Inf: Sediment Forebayl Infiltration Basin Inflow Area = 0.589 ac, 47.90% Impervious, Inflow Depth > 6.66" Inflow - 4.46 cfs @ 12.09 hrs, Volume= 0.327 of Outflow = 3.40 cfs @ 12.15 hrs, Volume= 0,231 A Atten= 24%, Lag=4.0 min Discarded = 0.03 cfs @ 12.15 hrs, Volume= 0,029 of Primary = 3.37 cfs @ 12.15 hrs, Volume= 0,202 of Routing by Stor-Ind method, Time Span= 0.01-20,00 hrs, dt= 0.01 hrs j 100 Year Storm (8.79 in) Bake N Joy - Post Developed Type 11124-hr Rainfall=8.79" Prepared by The Morin-Cameron Group, Inc. Printed 1/19/2015 HydroCADO 10.00 sln 00401 ©2011 HydroCAD Software Solutions LI_C Page 3 i Peals Elev= 258.72' @ 12.15 hrs Surf.Area=4,419 sf Storage= 5,434 cf Plug-Flow detention time= 128.6 min calculated for 0.231 of(71% of inflow) Center-of-Mass det. time= 57.4 min (797.6- 740.2 ) Volume Invert Avail.Stora a Storage Description ##1 257.00' 10,484 of Custom Stage Data (Conic) Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area feet s -ft cubic-feet cubic-feet s -ft 257.00 2,280 0 0 2,280 258.00 3,184 2,719 2,719 3,203 259.00 4,961 4,040 6,759 4,994 259.70 5,690 3,725 10,484 5,745 Device Routing Invert Outlet Devices #1 Discarded 257.00' 0.270 inlhr Exfiltratlon over Surface area #2 Primary 258.40' Custom Weir/Orifice, Cv=2.62 (C= 3.28) Head (feet) 0.00 1.00 Width (feet) 6,00 11.00 i Qiscarded OutFlow Max=0.03 cfs @ 12.15 hrs HW=256.72' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=3.37 cfs @ 12.15 hrs HW=258.72' (Free Discharge) "L2=Custom Weir/Orifice (Weir Controls 3.37 cfs @ 1.79 fps) i Stormwater Mana ement Calculations Revised: January 19, 2015 Standard 3: Recharge To Groundwater: Static Method Limit of Work Area only Existing Impervious Area= 65,337 SF Proposed Impervious Area = 82,373 SF There is an increase in the amount of impervious surface of 17,036SF New Development Areas Hydrologic Soil Group Recharge Rainfall Depth C 0.25" Recharge Volume Required for New Development area only-- [0.25" x 17,036 SF] = 4,259/12 SF-In = 355 CF Infiltration calculated at 1,700 SF only, not full basin. Recharge Volume provided @ spillway crest (excluding forebay) _ (1,700 SF/2,280 SF) 4,124=3,075 CF provided. Standard is met. (No Recharge above the 10-Year Storm Elevation, Mounding Analysis Not Required) Drawdown Analysis: Static Method Sediment Forebay/Infiltration Basin Average bottom Area of Infiltration Areas, New Detention Pond, excluding area of sediment forebay Area of sediment forebay = 568SF Effective area at bottom elev. 257.0 = 2280 -568=1,712SF Effective area at spillway crest 258.4= 3,848-568=3,280SF i i Effective average area-- (1,712+3,280)/2=2,496SF I Volume in sediment forebay below weir elev. 257.6 =330CF Total volume to be infiltrated = volume at spillway crest (258.4)—sediment forebay storage =4,124-330=3,794CF New Detention Pond Drawdown Time = [(3,794 CF/ 0.27 in/Hr.) x 12 in/ft.] / 2,496 SF = 67.6 hours Standard 4: Water uali Volume : New Development Area Use water quality depth of 1.0" For Moderately Draining Soil over 2.41 Inches/Hour WQV = 1.0 "X 17,036 SF Pavement/12 = 1,420 CF 3,794 CF below outlet of infiltration basin. The standard is met. Sediment Forebay Sizing Sediment Forebay/Infiltiration Basin Area new parking lot= 12.297 SF Volume = 0.25 X 12.297 SF/12" = 307 CF Provided 330CF a 257.5 weir crest, Standard is met CNC> E.x i n uT rz AT t O R No Exfiltration in Basin Bake N Joy - Post Developed Type IN 24-hr 2-Year Rainfall=3.10" Prepared by The Morin-Cameron Group, Inc. Printed 1/20/2015 H droCADO 10.00 sin 00401 ©2011 H droCAD Software Solutions LLC Page 1 Summary for Reach DP1: North wetlands Inflow Area = 2.936 ac, 63.84% Impervious, Inflow Depth > 1.59" for 2-Year event Inflow = 5.04 cfs @ 12,11 hrs, Volume= 0.389 of Outflow - 5.04 cfs @ 12.11 hrs, Volume= 0.389 af, Aften= 0%, Lag=0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.01-20.00 hrs, dt= 0.01 hrs Summary for Pond Inf. Sediment Forebayl Infiltration Basin Inflow Area = 0.589 ac, 47.90% Impervious, Inflow Depth > 1.77" for 2-Year event Inflow = 1.18 cfs @ 12,09 hrs, Volume= 0.087 of Outflow -- 0.00 cfs @ 0.01 hrs, Volume= 0.000 af, Aften= 100%, Lag= 0.0 min Primary = 0.00 cfs @ 0.01 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.01-20.00 hrs, dt= 0.01 hrs Peak Elev= 258.31' @ 20.00 hrs Surf.Area= 3,693 sf Storage= 3,785 cf Plug-Flow detention time= (not calculated: initial storage excedes outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Stora a Storage Description #1 257.00' 10,484 cf Custom Stage Data (Conic) Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq—ft) (cubic-feet) (cubic-feet) - --(sq-ft) 257.00 2,280 0 0 2,280 258.00 3,184 2,719 2,719 3,203 259.00 4,961 4,040 6,759 4,994 259.70 5,690 3,725 10,484 5,745 Device Routine Invert Outlet Devices #1 Primary 258.40' Custom Weir/Orifice, Cv=2.62 (C= 3.28) Head (feet) 0.00 1.00 Width (feet) 5.00 11.00 Primary Outflow Max=0.00 cfs @ 0.01 hrs HW=257.00' (Free Discharge) "L1-Custom Weir/Orifice (Controls 0.00 cfs) I i i 1 . I No Exfiltration in Basin Bake N Joy - Post Developed Type 11124-hr 10-Year Rainfall=4.50" Prepared by The Morin-Cameron Group, Inc. Printed 1/20/2015 H droCADO 10.00 s/n 00401 ©2011 H droCAD Software Solutions LLC Page 2 Summary for Reach DP1: North wetlands Inflow Area = 2,935 ac, 63.84% Impervious, Inflow Depth > 2.76" for 10-Year event Inflow = 7.91 cfs @ 12.11 hrs, Volume= 0.675 of Outflow - 7.91 cfs @ 12.11 hrs, Volume= 0.675 af, Atten= 0%, Lag= 0.0 min E Routing by Stor-Ind+Trans method, Time Span= 0.01-20.00 hrs, dt= 0.01 hrs Summary for Pond Inf: Sediment Forebayl Infiltration Basin Inflow Area = 0.589 ac, 47.90% Impervious, Inflow Depth > 2.90" for 10-Year event Inflow = 1.94 cfs @ 12.09 hrs, Volume= 0.142 of Outflow - 0.17 cfs @ 13.07 hrs, Volume= 0.046 af, Atten= 91%, Lag= 58.7 min Primary -- 0.17 cfs @ 13.07 hrs, Volume= 0.046 of Routing by Star-Ind method, Time Span= 0.01-20.00 hrs, dt= 0.01 hrs Peak Elev= 258.45' @ 13.07 hrs Surf.Area= 3,927 sf Storage=4,301 cf Plug-Flow detention time= 308.3 min calculated for 0.046 of(33% of inflow) Center-of-Mass det. time= 167.9 min (916.8- 748.9 ) Volume Invert Avail.Stora a Storage Description #1 257.00' 10,484 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area feet s -ft cubic-feet cubic-feet s -ft 267.00 2,280 0 0 2,280 258.00 3,184 2,719 2,719 3,203 259.00 4,961 4,040 6,759 4,994 259.70 5,690 3,725 10,484 5,745 Device Routing Invert Outlet Devices #1 Primary 258.40' Custom Weir/Orifice,Cv=2.62 (C=3.28) Head (feet) 0.00 1.00 Width (feet) 5.00 11.00 Primary OutFlow Max=0.16 cfs @ 13.07 hrs HW=258.45' (Free Discharge) L1=Custom Weir/Orifice (Weir Controls 0.16 cfs @ 0.69 fps) I No Exfiltration in Basin Bake N Joy - Post Developed Type 11124-hr 100-Year Rainfall=6.50" Prepared by The Morin-Cameron Group, Inc. Printed 1/20/2015 HydroCADD 10.00 s/n 00401 0 2011 HydroCAD Software Solutions LLC Page 3 Summary for Reach DP1; North wetlands Inflow Area = 2.935 ac, 63.84% Impervious, Inflow Depth > 4.55" for 100-Year event Inflow = 12.71 cfs @ 12.13 hrs, Volume= 1.113 of Outflow - 12.71 cfs @ 12.13 hrs, Volume= 1.113 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span=0.01-20.00 hrs, dt= 0.01 hrs i Summary for Pond Inf: Sediment Forebayf Infiltration Basin Inflow Area = 0.589 ac, 47.90% Impervious, Inflow Depth > 4.61" for 100-Year event Inflow = 3.10 cfs @ 12.09 hrs, Volume= 0.227 of Outflow - 1.52 cfs @ 12.24 hrs, Volume= 0.130 af, Atten= 51%, Lag= 9.2 min Primary = 1.52 cfs @ 12.24 hrs, Volume= 0.130 of Routing by Stor Ind method, Time Span= 0.01-20.00 hrs, dt= 0.01 hrs Peak Elev= 258.59' @ 12.24 hrs Surf.Area= 4,191 sf Storage=4,900 cf Plug-Flow detention time= 182.0 min calculated for 0.130 of(58% of inflow) Center-of-Mass det. time= 93.7 min ( 838.0-744.3) Volume Invert Avail.Storage Storage Description #1 257.00' 10,484 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area {feet} (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 257,00 2,280 0 0 2,280 258.00 3,184 2,719 2,719 3,203 259.00 4,961 4,040 6,759 4,994 259.70 5,690 3,725 10,484 5,745 Device Routing Invert Outlet Devices #1 Primary 258.40' Custom Weir/Orifice, Cv= 2.62(C= 3.28) Head (feet) 0.00 1.00 Width (feet) 5.00 11.00 Primary OutFlow Max=1.52 cfs @ 12.24 hrs HW=258.59' (Free Discharge) t-1=Custom Weir/Orifice (Weir Controls 1.52 cfs @ 1.41 fps) I i j E I Enright, Jean From: Lisa Eggleston <lisa@egglestonenvironmental.com> Sent: Wednesday,January 28, 2015 9:11 AM To: Enright,Jean Cc: John Morin Subject: FW: Bake N Joy - Revised plans and infomration i Hi Jean, See below - this one's all set from my end. Lisa D. Eggleston, P.E. Eggleston Environmental 32 Old Framingham Rd, Unit #29 Sudbury, MA 01776 Tel 508.259.1137 From: Lisa Eggleston<lisa@egglestonenvironmental.com> Date:Tuesday,January 27, 2015 at 12:14 PM To:john morin <lohn@morincameron.com>, "Gaffney, Heidi" <HGaffnev@townofnorthandover.com>,Jennifer Hughes <Jhughes@townofnorthandover,com> Subject: Re: Bake N Joy- Revised plans and infomration Jennifer, Just want to let you know that I have reviewed the January 20, 2015 response from Morin-Cameron Group on this project, and that it satisfactorily and thoroughly addresses my December 8th comments. I have no additional comments on this project. Please let me know if you have any questions. Lisa D. Eggleston, P.E. Eggleston Environmental 32 Old Framingham Rd, Unit#29 Sudbury, MA 01776 Tel 508.259.1137 From:john morin<john@morincameran.com> Date:Tuesday,January 20, 2015 at 3:26 PM To: "Gaffney, Heidi" <HGaffnev@townofnorthandover,com> Cc: Lisa Eggleston<__lisa@egglestonenvironmental.com> Subject: Bake N Joy- Revised plans and infomration Hi Held!, Please find attached revised Information that has been prepared in response to Lisa's review letter; hard copies will be dropped off at your office tomorrow morning. Any questions please give me a call. Thanks, E • 1 Hi Lisa.....Hard copies of the attached information is being sent to you overnight mail. The revised plans and responses are pretty much in line with what we discussed. We are scheduled to appear before the Conservation Commission on Wednesday Jan, 28 and the Planning Board on Tuesday Feb. P, 1 am hoping you will have time to review the additional Information prior to the Conservation Commission meeting on Jan. 28; if not we may go to the meeting to discuss the changes and then continue. Any questions please give me a call. Thanks, John M. Morin, P.E. THE MORIN-CAMERON CROUP, INC.447 Boston Street, US Route I,Topsfield, MA 0198:3 pl978.887.8586#J978.887.3480Fav I www,morincameron.com 2 I Long Term Pollution Prevention Plan Bake N Joy Foods, Inc. 351 Willow Street South Nor h Andover Massachusetts November 12, 2014 Revised:January 19, 2015 The following operation and maintenance plan has been provided to satisfy the requirements of Standard 9 of the MassDEP Stormwater Management Handbook. The success of the Stormwater Management Plan depends on the proper implementation, operation and maintenance of several management components. The following procedures shall be implemented to ensure success of the Stormwater Management Plan: 1. The contractor shall comply with the details of construction of the site as shown on the approved plans. 2. The Catch Basins, Sediment Fore bay/infiltration Basin, Detention Basin, VortSentry Unit, Water Quality Swale, First Defense Units and Cultec Infiltrator Chamber System shall be inspected and maintained as shown in the manufacturer's guidelines and as indicated below. The attached "BMP Key Plan" shows the approximate locations of the BMP`s mentioned above. 3. Effective erosion control measurers during and after construction shall be maintained until a stable turf is established on all altered areas. Basic Information Stormwater Management System Owner: Muffin Realty Trust Bake N Joy Foods, Inc. 351 Willow Street North Andover, MA 01845 978-683-1.414 North Andover Department of Public Works: Bruce D. Thibodeau, P.E. Director 384 Osgood Street North Andover, MA 01845 978-685-0950 North Andover Planning Department: Town Planner 1600 Osgood Street North Andover, MA 01845 978-688-9535 North Andover Conservation Commission: Ms. Jennifer Hughes Conservation Administrator 1600 Osgood Street North Andover, MA 01845 978-688-9530 E i { Erosion and Sedimentation ControjE. During C nstruction: The site and drainage construction contractor shall be responsible for maintaining the stormwater system during construction. Routine maintenance of all items shall be performed to ensure adequate runoff and pollution control during construction. i A combination of proposed silt fence and filter sock backed with silt fence will be placed as j shown on the proposed plan prior to the commencement of any clearing, grubbing, and earth removal or construction activity. The integrity of the erosion control barrier will be maintained by periodic inspection and replacement as necessary. The erosion control barrier will remain in place until the first course of pavement has been placed and all side slopes have been foamed and seeded and vegetation has been established. A silt sack will also be placed over the existing catch basins and the new catch basins once they are constructed. General Conditions 1. The property owner shall be responsible for scheduling regular inspections and maintenance of the stormwater BMP's as detailed in the following long-term pollution prevention plan and illustrated on the approved design plans: "Site Plan of Land" Prepared For Muffin Realty Trust, 351 Willow Street, North Andover, Massachusetts, Sheets 1-4, prepared by The Morin-Cameron Group, Inc. dated November 12, 2014 as revised and approved by the North Andover Planning Board and Conservation Commission, hereinafter referred to as the Site Plans. 2. All Stormwater BMP's shall be operated and maintained in accordance with the design plans and the following Long-Term Pollution Prevention Plan. 3. The owner shalt: a. Maintain an Operation and Maintenance Log (see Attachment A) for the last three years. The log shall include all BMP inspections, repairs, replacement activities and disposal activities (disposal material and disposal location shall be included in the log), b. Make the log available to the North Andover Department of Public Works, Conservation Commission and Planning Department upon request; c. Allow members and agents of the North Andover Department of Public Works, Conservation Commission and Planning Department to enter the premises and ensure that the Owner has complied with the Operation and Maintenance Plan requirements for each BMP. 4. A recommended inspection and maintenance schedule is outlined below based on statewide averages. This inspection and maintenance schedule shall be adhered to at a minimum for the first year of service of all BMP's referenced in this document. At the commencement of the first year of service, a more accurate inspection/maintenance schedule shall be determined based on the level of service for this site if required. 3 1 1 . 1 Long-Term Pollution Prevention Plan (LTPPP) E i Ve etated Areas: Immediately after construction, monitoring of the erosion control systems shall occur until establishment of natural vegetation. Afterwards, vegetated areas shall be maintained as such. Vegetation shall be replaced as necessary to ensure proper stabilization of the site. Cost: Included with annual landscaping budget, Consult with local landscape contractors. QeeP Sump Catch Basins The catch basin grates shall be checked quarterly and following heavy rainfalls to verify that the inlet openings are not clogged by debris. Debris shall be removed from the grates and disposed of properly. Deep sump catch basins shall be inspected and cleaned quarterly as needed when accumulated sediments exceed 2' from the bottom of the sump (approximately 1/2 of the sump capacity). Catch basins with hoods shall be inspected annually to check oil buildup and outlet obstructions. Material shall be removed from catch basins and disposed of in accordance with all applicable regulations by a licensed hauler. At a minimum catch basins shall be cleaned once per year. Cost: Estimated $50 - $100 per cleaning per catch basin as needed. The Owner shall consult local waste haulers for detailed cost estimates. Public Safety Concerns: Catch basins shall not be left open and unattended at any time during inspection, cleaning or otherwise. Broken grates or frames shall be replaced immediately. At no time shall any person enter the basin structure unless measures have been taken to ensure safe access in accordance with enclosed space regulations. Sediment Forebay/fnfiltra,ion Basin: The sediment forebay/infiltration basin shall be inspected after every major storm event for the first 3 months after construction; a major storm event is 3.9 inches of rainfall in a 24 hour period (5 year storm). Thereafter, the basin shall be inspected twice per year (April/October). If the system does not drain within 72 hours of a rainstorm, the operator shall inform the design engineer. Snow shad not be stored in the infiltration basin. The following maintenance is required: • Side slopes and bottom to be mowed twice during growing season and accumulated trash and debris removed (May &August). • Sediment to be removed as necessary. Sediment removal should not take place until bottom of forebay/basin is dry. • Deep tilling can be used to break up clogged surface areas. Any tilled area to be revegetated immediately. Cost: $80041,000 per cleaning of each system. Consult local pumping companies for costs associated with cleaning of basins if necessary to remove sediment. i Detention Basin: The basin shall be inspected twice per year(ApriVOctober). Snow shall not be stored in the infiltration basin. The following maintenance is required: • Side slopes and bottom to be mowed twice during growing season and accumulated trash and debris removed (May&August). • Sediment to be removed as necessary. Sediment removal should not take place until bottom of basin is dry. • Deep tilling can be used to break up clogged surface areas. Any tilled area to be revegetated immediately. Vort5entry Water Quality Unit: The VortSentry water quality pretreatment unit shall be inspected twice per year in April and October. The unit shall be cleaned per manufacturer instructions included herein and at a minimum once per year. (Note: A vacuum truck will be required for the maintenance of this unit.) Water Qualft Swales: Inspect the swale twice a year (ApriVOctober). During the inspection check swale for slope integrity, soil moisture, vegetative health, soil stability, soil compaction, soil erosion, ponding and sedimentation. The following maintenance is required: i Mow swales at least once per year, do not cut the grass shorter than three to four inches. Do not let grass height exceed six inches. • At least once per year manually remove sediment and debris. • Periodically re-seed, if required, to maintain a dense growth of vegetation. First Defense Unit: Inspections shall occur every six months unless six month inspections show the need for more frequent inspections. The following maintenance is required: • Remove sediment a minimum of once a year or as needed (ie: once depth reaches 26") • Remove Sediment following a spill in the drainage area • Remove Oil& Floatables once a year or with sediment removal • Remove Oil& Floatables following a spill in the drainage area i i C.uttec Infiltrator Chamber System Inspections shall occur twice a year(April/October) The following maintenance is required: • Measure water depths in inspection ports at 24 and 48 hour intervals after a storm to verify structure is draining. • Rehabilitate structure if it fails due to clogging Debris& Litter: All debris and litter shalt be removed from the parking area as necessary to prevent migration into the drainage system. Pesticides, Herbicides, and Fertilizers: Pesticides and herbicides shall be used in accordance with the Town of North Andover regulations and Zoning Bylaw as amended from time to time. Fertilizers shalt be restricted to the use of organic fertilizers only. Alf fertilizers, herbicides, pesticides, and the like shall be stored in a dry area that is protected from weather. Cost: Included in the routine landscaping maintenance schedule. The Owner shall consult local landscaping contractors for details. Public Safety Concerns: Chemicals shall be stored in a secure area to prevent children from obtaining access to them. Any major spitts shall be reported to municipal officials. Snow Storage and Removal: Snow storage areas are designated on the approved design plans. Snow shall only be stored in designated areas. In heavy snow seasons, snow shall be removed from the property and disposed of in accordance with applicable regulations and a certified snow disposal site. The owner shall be responsible for informing snow removal contractors of the location for snow storage areas on the property. Cost: Annual snow removal budget to be established by the Owner. The Owner shall consult local snow removal contractors for details. Prevention of Illicit Di scharpes Illicit discharges to the stormwater management system are not allowed. Illicit discharges are discharges that are not comprised entirely of stormwater. Pursuant to MassDEP Stormwater Standards the following activities or facilities are not considered illicit discharges; firefighting, water line flushing, landscape irrigation, uncontaminated groundwater, potable water sources, foundation drains, air conditioning condensation, footing drains, individual resident car washing, flows from riparian habitats and wetlands, dechlorinated water from swimming pools, water used for street washing and water used to clean residential building without detergents. I To prevent illicit discharges to the stormwater management system the following policies should be implemented: 1. Provisions For Storing Materials and Waste Products Inside or Under Cover z. Vehicle Maintenance and Washing Controls 3. Requirements for Routine Inspections of the Stormwater Management System (ie: catch basins, proprietary treatment unit &subsurface infiltration system.) 4. Spill Prevention and Response Plans. 3 1 i` I I I E Project Location: Bake N Joy Foods, Inc — 351 Willow Street South, North Andover, MA Date: Stormwater Management — Post Construction Phase Best Management Practices — Inspection Schedule and Evaluation Checklist Long Term Practices Best Cleaning/Repair Date of Inspection Date Minimum Maintenance and Key Management Frequency Inspected Inspector Items to Check Needed: Cleaning/ Performed by Practice (List Items) Repair Ayes []no (1) Refer to the Massachusetts Stormwater Handbook issued January 2,2008 Notes(Include deviations from : Site Plan Approval and Order of Conditions and Approved Plans): 1. Limited or no use of sodium chloride slats,fertilizers or pesticides recommended. Slow release fertilizer recommended if necessary. Stormwater Control Manager i Construction Period Pollution Prevention Plan November 12, 2014 Revised:January 19, 2015 Erosion and Sedimentation will be controlled at the site by utilizing Structural Practices, Stabilization Practices, and Dust Control. These practices correspond with ptans entitled "Site Plan Of Land" Prepared For Muffin Realty Trust, 351 Willow Street South, North Andover, Massachusetts, Sheets 1-4", prepared by The Morin-Cameron Group, Inc. dated November 12, 2014 as revised and approved by the North Andover Planning j Board and Conservation Commission, hereinafter referred to as the Site Plans. Responsible Party Contact Information: Stormwater Management System Owner: Muffin Realty Trust Bake N Joy Foods, Inc. 351 Willow Street South North Andover, MA 01845 P: (978) 683-1414 Town of North Andover Contact Information: North Andover Planning Department Town Planner 1600 Osgood Street North Andover, MA 01845 Phone: (978) 688-9535 North Andover Conservation Commission Ms.Jennifer Hughes 1600 Osgood Street North Andover, MA 01845 Phone: (978) 688-9530 North Andover public Works Bruce D. Thibodeau, P.E. 384 Osgood Street North Andover, MA 01845 Phone: (978) 685-0950 Site Design Engineer Information: The Morin-Cameron Group, Inc. 447 Boston Street, Route 1 Topsfield, MA 01983 Phone: (978) 887-8586 Structural Practices: 1) Sediment Barriers--A combination of silt fence and filter sock backed with silt fence shall be constructed around the limit of work as indicated on the approved plans to prevent the spreading of fine sediments from the site. This control will be installed prior to major soil disturbance on the site. Sediment Barrier Requirements a) locate the silt fence and filter sock backed with silt fence upland where identified on the plans. b) The silt fence and filter sock backed with silt fence should be nearly level through most of its length to impound a broad, temporary pool. The last 10 to 20 feet at each end of the silt fence and filter sock backed with silt fence should be swung slightly uphill(approximately 0.5 feet in elevation) to provide storage capacity. c) Stake the silt fence and filter sock in accordance with the construction details. d) The silt fence and filter sock should be removed when it has served its useful purpose, but not before the upslope area has been permanently stabilized through one growing season and only following approval by the Conservation Commission or their representative. Retained sediment must be removed and properly disposed of, or mulched and seeded. Sediment Barrier Inspection/Maintenance a) Silt fence and filter sock backed with silt fence should be inspected immediately after each rainfall event of 1-inch or greater, and at least daily during prolonged rainfall. Inspect the depth of sediment, tears, if the silt fence is securely attached to the stakes, and to see that the stakes are firmly In the ground. Repair or replace as necessary. b) Remove sediment deposits promptly after storm events to provide adequate storage volume for the next rain and to reduce pressure on the silt fence and filter sock. Sediment will be removed from behind the silt fence and filter sock when it becomes about 4" deep at the silt fence/filter sock. Take care to avoid undermining the silt fence/filter sock during cleanout. c) If the silt fence tears, or in any way becomes ineffective, replace it immediately. d) Remove all silt fence/filter sock materials after the contributing drainage area has been properly stabilized. Sediment deposits remaining after the silt fence/filter sock have been removed should be graded to conform to the existing topography and vegetation. i I 2) Inlet Protection —Inlet Protection will be utilized around the existing catch basin grates and in the new grates once installed. The inlet protection wilt allow the storm drain inlets to be used before finat stabilization. This structural practice will allow early use of the drainage system. Sittsack or equivalent will be utilized for the inlet protection. Siltsack is manufactured by ACF Environmental. The telephone number is 800-448-3636. Regular flow siltsack wilt be utilized, and if it does not allow enough storm water flow, hi-flow siltsack wit(be utilized. Silt Sack(or equivalent) Inlet Protection Inspection/Maintenance Requirements a) The sitt sack trapping device and the catch basin should be inspected after every rain storm and repairs made as necessary. b) Sediment should be removed from the silt sack after the sediment has reached a maximum depth of one-half the depth of the trap. c) Sediment should be disposed of in a suitable area and protected from erosion by either structural or vegetative means. Sediment material removed shalt be disposed of in accordance with all applicable local, state, and federal regulations. d) The silt sack must be replaced if it is ripped or torn in any way. e) Temporary traps should be removed and the area repaired as soon as the contributing drainage area to the inlet has been completely stabilized. Stabilization Practices: Stabilization measures shall be implemented as soon as practicable in portions of the site where construction activities have temporarily or permanently ceased, but in no case more than 14 days after the construction activity in that portion of the site has temporarily or permanently ceased, with the following exceptions. • Where the initiation of stabilization measures by the 14th day after construction activity temporary or permanently cease is precluded by snow cover, stabilization measures shalt be initiated as soon as practicable. • Where construction activity will resume on a portion of the site within 21 days from when activities ceased, (e.g. the total time period that construction activity is temporarily ceased is less than 21 days) then stabilization measures do not have to be initiated on that portion of the site by the 141h day after construction activity temporarily ceased I) Temporary Seeding—Temporary seeding will allow a short-term vegetative cover on disturbed site areas that may be in danger of erosion. Temporary seeding will be done at stock piles and disturbed portions of the site where construction activity will temporarily cease for at least 21 days. The temporary seedings wit[ stabilize cleared and unvegetated areas that will not be brought into final grade for several weeks or months. Temporary Seeding Planting.Procedures a) Planting should preferably be done between April V and June 30`h, and j September 1"through September 31'. If planting is done in the months of July and August, irrigation may be required. If planting is done between October I" and March 31", mulching should be applied immediately after planting. If seeding is done during the summer months, irrigation of some sort will probably be necessary. i b) Before seeding, install structural practice controls. Utilize Amoco supergro or equivalent. c) Select the appropriate seed species for temporary cover from the following table. Species Seeding Rate Seeding Rate Recommended Seeding Seed Cover (lbs/1,000 s .ft.) (lbs/acre) Dates required Annual 1 40 April 1'to June V 1/4 inch R e rass Au ust 15`h to Sept. 15'h Foxtail 0.7 30 May 15`to June 30` 1/2 to 3/4 inch Millet Oats 2 80 April V to July 15` 1 to 1-1/2 August 1511)to Sept. 15`'' inch Winter 3 120 August 15'h to Oct. 15 1 to 1-V2 Rye inch Apply the seed uniformly by hydroseeding, broadcasting, or by hand. i d) Use effective mulch, such as clean grain straw, tacked and/or tied with netting to protect seedbed and encourage plant growth. Temporary Seeding Inspection/Maintenance a) Inspect within 6 weeks of planting to see if stands are adequate. Check for damage within 24 hours of the end to a heavy rainfall, defined as a 2-year storm event (i.e., 3.2 inches of rainfall within a twenty-four hour period). Stands should be uniform and dense. Reseed and mulch damaged and sparse areas immediately. Tack or tie down mulch as necessary. b) Seeds should be supplied with adequate moisture. Furnish water as needed, especially in abnormally hot or dry weather. Water application rates should be controlled to prevent runoff. 2) Geotextites - Geotextiles such as jute netting will be used in combination with other practices such as mulching to stabilize slopes. The following geoteWle materials or equivalent are to be utilized for structural and nonstructural controls as shown in the following table. � Practice Manufacturer Product Remarks :Secliment Fence Amoco Woven polypropylene J 0.425 mm opening i I 1198 ore uivatent Construction Amoco Woven polypropylene 0.300 mm opening Entrance 2002 orequivalent Outlet Amoco Nonwoven polypropylene 0.150 mm opening Protection 4551 orequivalent Erosion Control Amoco Supergro or equivalent Erosion control (slope stability) revegetation mix, open polypropylene fiber on degradable polypropylene net scrim Amoco may be reached at (800) 445-7732 Geotextile Installation a) Netting and matting require firm, continuous contact between the materials and the soil. If there is no contact, the material will not hold the soil and erosion will occur underneath the material. Geotextile Ins ection Maintenance a) In the field, regular inspections should be made to check for cracks, tears, or breaches in the fabric. The appropriate repairs should be made. 3) Mulching and Netting— Mulching wilt provide immediate protection to exposed soils during the period of short construction delays, or over winter months through the application of plant residues, or other suitable materials, to exposed soil areas. In areas, which have been seeded either for temporary or permanent cover, mulching should immediately follow seeding. On steep slopes, mulch must be supplemented with netting. The preferred mulching material is straw. Mulch (Hay or Straw) Materials and Installation a) Straw has been found to be one of the most effective organic mulch materials. The specifications for straw are described below, but other material may be appropriate. The straw should be air-dried; free of undesirable seeds &coarse materials. The application rate per 1,000 sq.ft. is 90-100 lbs. (2-3 bales) and the application rate per acre is 2 tons (100-120 bales). The application should cover about 90% of the surface. The use of straw mulch is appropriate where mulch is maintained for more than three months. Straw mulch is subject to wind blowing unless anchored, is the most commonly used mulching material, and has the best microenvironment for germinating seeds. Mulch Maintenance a) Inspect after rainstorms to check for movement of mulch or erosion. If washout, breakage, or erosion occurs, repair surface, reseed, remulch, and install new netting. b) Straw or grass mulches that blow or wash away should be repaired promptly. c) If plastic netting is used to anchor mulch, care should be taken during initial mowings to keep the mower height high. Otherwise, the netting can wrap up on the mower blade shafts. After a period of time, the netting degrades and becomes less of a problem. d) Continue inspections until vegetation is well established. 4) Land Grading—Grading on fill slopes, cut slopes, and stockpile areas will be done with full siltation controls in place. Land Grading Desian/lnstallgtion Requirements a) Areas to be graded should be cleared and grubbed of all timber, logs, brush, rubbish, and vegetated matter that will interfere with the grading operation. Topsoil should be stripped and stockpiled for use on critical disturbed areas for establishment of vegetation. Cut slopes to be topsoiled should be thoroughly scarified to a minimum depth of 3-inches prior to placement of topsoil. b) Fill materials should be generally free of brush, rubbish, rocks, and stumps. Frozen materials or soft and easily compressible materials should not be used in fills intended to support buildings, parking lots, roads, conduits, or other structures. c) Earth fill intended to support structural measures should be compacted to a minimum of 90 percent of Standard Proctor Test density with proper moisture control, or as otherwise specified by the engineer responsible for the design. Compaction of other fills should be to the density required to control sloughing, erosion or excessive moisture content. Maximum thickness of fill layers prior to compaction should not exceed 9 inches. d) The uppermost one foot of fill slopes should be compacted to at least 85 percent of the maximum unit weight(based on the modified AASHTO compaction test). This is usually accomplished by running heavy equipment over the fill. e) Fill should consist of material from borrow areas and excess cut will be stockpiled in areas shown on the Site Plans. All disturbed areas should be free draining, left with a neat and finished appearance, and should be protected from erosion. Land Grading Stabilization inspection/Maintenance a) Alt slopes should be checked periodically to see that vegetation is in good condition, Any rills or damage from erosion and animal burrowing should be repaired immediately to avoid further damage. b) If seeps develop on the slopes, the area should be evaluated to determine if the seep will cause an unstable condition. Subsurface drains or a gravel mulch may be required to solve seep problems. However, no seeps are anticipated. I c) Areas requiring revegetation should be repaired immediately. Control undesirable vegetation such as weeds and woody growth to avoid bank stability problems in the future. i 5) T_o soilin *_Topsoiling will help establish vegetation on all disturbed areas throughout the site during the seeding process. The soil texture of the topsoil to be used will be a sandy loam to a silt loam texture with 15%to 20% organic content. Topsoiting Placement a) Topsoil should not be placed while in a frozen or muddy condition, when the subgrade is excessively wet, or when conditions exist that may otherwise be detrimental to proper grading or proposed seeding, b) Do not place topsoil on slopes steeper than 2.5:1, as it will tend to erode. c) If topsoil and subsoil are not properly bonded, water will not infiltrate the soil profile evenly and it will be difficult to establish vegetation. The best method is to actually work the topsoil into the layer below for a depth of at least 6 inches. 6) Permanent Seeding — Permanent Seeding should be done immediately after the final design grades are achieved. Native species of plants should be used to establish perennial vegetative cover on disturbed areas. The revegetation should be done early enough in the fall so that a good cover is established before cold weather comes and growth stops until the spring. A good cover is defined as vegetation covering 75 percent or more of the ground surface. Permanent Seeding Seedbed Preparation a) In infertile or coarse-textured subsoil, it is best to stockpile topsoil and re-spread it over the finished slope at a minimum 2 to 6-inch depth and roll it to provide a firm seedbed. The topsoil must have a sandy loam to silt loam texture with 15% to 20%organic content. If construction fill operations have left soil exposed with a loose, rough, or irregular surface, smooth with blade and roll. b) Loosen the soil to a depth of 3-5 inches with suitable agricultural or construction equipment. c) Areas not to receive topsoil shall be treated to firm the seedbed after incorporation of the lime and fertilizer so that it is depressed no more than V2 - 1 inch when stepped on with a shoe. Areas to receive topsoil shall not be firmed until after topsoiling and time and fertilizer is applied and incorporated, at which time it shall be treated to firm the seedbed as described above. Permanent Seeding Grass Selection/Application a) Select an appropriate cool or warm season grass based on site conditions and seeding date. Apply the seed uniformly by hydro-seeding, broadcasting, or by hand. Uniform seed distribution is essential. On steep slopes, hydroseeding may be the most effective seeding method. Surface roughening is particularly Important when preparing slopes for hydroseeding, b) Lime and fertilize. Organic fertilizer shall be utilized in areas within the 100 foot buffer zone to a wetland resource area. c) Mulch the seedings with straw applied at the rate of Yz tons per acre. Anchor the mulch with erosion control netting or fabric on sloping areas. Amoco supergro or equivalent should be utilized. Permanent Seeding Inspection/Maintenance a) Frequently inspect seeded areas for failure and make necessary repairs and reseed immediately, Conduct or follow-up survey after one year and replace failed plants where necessary. b) If vegetative cover is inadequate to prevent rill erosion, overseed and fertilize in accordance with soil test results. c) If a stand has less than 40%cover, reevaluate choice of plant materials and quantities of time and fertilizer. Re-establish the stand following seedbed preparation and seeding recommendations, omitting time and fertilizer in the absence of soil test results, If the season prevents resowing, mulch or jute netting is an effective temporary cover. d) Seeded areas should be fertilized during the second growing season. Lime and fertilize thereafter at periodic intervals, as needed. Organic fertilizer shall be I utilized in areas within the 100-foot buffer zone to a wetland resource area. Dust Control&Sediment Tracking. Dust control will be utilized throughout the entire construction process of the site. For example, keeping disturbed surfaces moist during windy periods will be an effective control measure, especially for construction access roads. The use of dust control will prevent the movement of soil to offsite areas. However, care must be taken to not create runoff from excessive use of water to control dust. The following are methods of Dust Control that may be used on-site: • Vegetative Cover—The most practical method for disturbed areas not subject to traffic, • Calcium Chloride—Calcium chloride may be applied by mechanical spreader as loose, dry granules or flakes at a rate that keeps the surface moist but not so high as to cause water pollution or plant damage. • Sprinkling —The site may be sprinkled until the surface is wet, Sprinkling will be effective for dust control on haul roads and other traffic routes. • Stone—Stone will be used to stabilize construction roads;will also be effective for dust control. The general contractor shall employ an on-site water vehicle for the control of dust as necessary. Sediment tracking onto paved areas shall be prevented through the use of street sweeping during construction. Depending on construction activities sweeping frequency shall vary. Sweeping shall be conducted at a frequency that prevents tracking of sediment onto public ways or as directed by the Environmental Monitor. Non-Stormwater Discharges: The construction de-watering and all non-stormwater discharges will be directed into a sediment dirt bag (or equivalent inlet protection) or a sediment basin. Sediment material removed shall be disposed of in accordance with all applicable local, state, and federal regulations. The developer and site general contractor will comply with the E.P.A.'s Final General Permit for Construction De-watering Discharges, (N.P.D.E,S,, Section 402 and 40 C.F.R. 122.26(b)(14)(x). Inspection/Maintenance: Operator personnel must inspect the construction site at least once every 14 calendar days and within 24 hours of a storm event of Vz-inch or greater. The applicant shall be responsible to secure the services of a design professional or similar professional (inspector) on an on-going basis throughout all phases of the project. Refer to the Inspection/Maintenance Requirements presented earlier in the "Structural and Stabilization Practices." The inspector should review the erosion and sediment controls with respect to the following: • Whether or not the measure was installed/performed correctly. • Whether or not there has been damage to the measure since it was installed or performed. • What should be done to correct any problems with the measure. The inspector should complete the Stormwater Management Construction Phase BMP Inspection Schedule and Evaluation Checklist, as attached, for documenting the findings and should request the required maintenance or repair for the pollution prevention measures when the inspector finds that it is necessary for the measure to be effective, The inspector should notify the appropriate person to make the changes and submit copies of the form to the North Andover Engineering Department, It is essential that the inspector document the inspection of the pollution prevention measures. These records will be used to request maintenance and repair and to prove that the inspection and maintenance were performed. The forms list each of the measures to be inspected on the site, the inspector's name, the date of the inspection, the condition of the measure/area inspected, maintenance or repair performed and any changes which should be made to the Operation and Maintenance Plan to control or eliminate unforeseen pollution of storm water. Project Location: Bake N Joy, North Andover, MA Date: Stormwater Management— Construction Phase Best Mana ement Practices -- Ins ection Schedule and Evaluation Checklist air Date of/Rep Inspection Date Minimum Maintenance and Cleaning Performed Frequency Inspected Inspector Key Items to Check Needed: Cleaning/ by List Items Repair 1. Silt Fence Design/Installation After heavy rainfall Requirements Oyes Ono Silt Fence events(minimum 2. Mulch Sock Inspection/Maintenance Barrier Controls weekly) 3. Deteriorated sections must be replaced. 4. Remove accumulated sediment over 4". 5. Evidence of sediment past mulch sock. After heavy rainfall 1. Silt Sack(or equivalent)Inlet Protection Oyes Ono Inlet Protection events(minimum Inspection/Maintenance weekly) After heavy rainfall 1. Temporary Seeding Planting Oyes. [:]no Temporary events(minimum Procedures Seeding weekly) 2. Temporary Seeding Inspection/ Maintenance After heavy rainfall Oyes, Ono Geotextiles events (minimum 1. Geotextile lnspectionfMaintenance weekly) Mulching & After heavy rainfall Oyes [--]no Netting events(minimum 1. Mulch Maintenance weekly) After heavy rainfall 1. Land Grading Stabilization lnspectbn/ ❑ es ❑no Land Grading events (minimum Maintenance weekly) Permanent After heavy rainfall 1. Permanent Seeding Inspection/ ❑ es Ono Seeding events(minimum Maintenance weekly) After heavy rainfall ❑ e,, Ono Dust Control events(minimum weekly) After heavy rainfall Soil Stockpiling events(minimum Oyes Ono weekly) (1) Refer to the Massachusetts Stormwater Handbook issued January 2,2008 and the Town of North Andover Bylaws. Stormwater Control Manager