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HomeMy WebLinkAbout2016/05/27 - Stormwater Report - 384 Osgood Street STORMWATER REPORT STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 This report details the existing and proposed hydrological and hydraulic conditions for the Improvements to the Town of North Andover Department of Public Works Building located at 384 Osgood Street in North Andover, MA. This report has been prepared in conformance with the requirements of the Massachusetts Department of Environmental Protection (MADEP) 2008 Stormwater Handbook and the 2008 amendments to 310 CMR 10.00 et. seq. (Massachusetts Wetlands Act Regulations (MAWPA Regs)) and the Town of North Andover Wetlands Protection Bylaw and Regulations and the Town of North Andover Stormwater Management & Erosion Control Bylaw and Regulations. The report has been organized to follow the MADEP Stormwater Checklist. Site Description: The project which is the subject of this report is located at 384 Osgood Street on the northwestern side of Osgood Street and the northeastern side of Wayne Street in North Andover, MA. The site contains a total of 3.56± acres and is the location of the existing Department of Public Works facility. The property is shown on the Town of North Andover Assessor's Map 94 as Lot 2. Existing Conditions: The portion of the site which is the subject of the base bid work is the portion of the site between the existing building and Osgood Street. The area is presently occupied by a parking area and lawn area. Drainage from the majority of the area flows overland into Cochichewick Brook. Drainage from the remainder of the area flows overland into Wayne Street. The portion of the site which is the subject of the alternate bid work is the portion of the site to the rear of the existing building. The area is presently occupied by paved and unpaved storage areas and an existing storage building. Drainage from the majority of the area flows overland into Cochichewick Brook. Drainage from the remainder of the area flows overland into Wayne Street and the wetlands located across Wayne Street from the site. Proposed Conditions: The base bid project consists of the redevelopment of the front portion of the site for the construction of a two story addition to the existing building along with May 27, 2016 Page 3 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 27, 2016 reconfiguration of parking, utility work on site, in Osgood Street and in Wayne Street as well as drainage improvements to the front of the existing DPW building The bid alternate consists of the replacement of the existing salt shed at the rear of the site along with reconfiguration of pavement areas on site and in Wayne Street and drainage improvements at the rear of the existing DPW building.. Standard 1: No New Untreated Discharges The proposed project will include one new drainage outlets and a second new drainage outlet if the bid alternate is accepted. Runoff to each of the outlets will be treated by the use of deep sump catch basins and Stormceptor stormwater treatment units and the peak rates of runoff from the project area will be reduced compared to the existing conditions due to a reduction in impervious area. A review of the attached calculations shows that the maximum velocity exiting new outlet #1 at the front of the site for a 100 year storm is 3.50 feet/second. A riprap apron will be provided at the outlet pipe to eliminate any possible erosion. A review of the attached calculations also shows that the maximum velocity exiting new outlet #2 at the rear of the site for a 100 year storm is 2.81 feet/second. A riprap apron will also be provided at the outlet pipe to eliminate any possible erosion. Since stormwater treatment is being provided for the new outlets and erosion concerns have been addressed by low discharge velocities and riprap aprons, Standard 1 has been fully met by the proposed project. Standard 2: Peak Rate Attenuation The proposed project involves the redevelopment of an existing developed site. As such, compliance with Stormwater Standard 2 is required only to the maximum extent practicable and measures must be been taken to improve existing conditions. Attached to this report are the existing and proposed runoff calculations for the project for the 2, 103 25 and 100 year storms. All of the stormwater modeling calculations were prepared using SCS Methods consistent with the requirements of the Wetland Protection Regulations and the MADEP 2008 Stormwater May 27, 2016 Page 4 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 Handbook. The calculations were prepared using HydroCAD software, Version 10.00 by Applied Microcomputers Systems. Soils data for the stormwater study was obtained from the National Resource Conservation Service Soil Map for the Town of North Andover as well as on-site test pits by a Massachusetts Licensed Soil Evaluator. Our firm analyzed that data and made our determination of what Hydrologic Soils Groups to use for the calculations. Ground cover data is based on the existing and proposed site conditions using on the ground survey and observations of the site. Times of concentration are based on the tributary watershed characteristics and SCS Methodology with a minimum time of concentration of 6 minutes as prescribed by the methodology. Rainfall data for the study is based on the Town of North Andover Wetlands Regulations. Stormwater mitigation for the proposed project is provided by reducing the impervious areas on the site. Due to the reduction in the impervious surfaces there is no increase in the peak rate of runoff from the project area after the project is constructed. Detailed printouts of the results of the stormwater modeling are provided for the 2, 10, 25 and 100 year storms. A summary of the peak rate of runoff calculations from the project area through the discharge pipe is as follows: A summary of the peak rates of runoff from the site to the various analysis points and points of discharge (see the attached watershed plans) is as follows: RUNOFF FROM MAIN PORTION OF FRONT OF SITE TO BROOK (EXISTING HYDROCAD NODE 1 E, PROPOSED NODE BP1) Storm Existing Existing Proposed Proposed Peak Runoff Return Peak Rate Runoff Peak Rate Runoff Rate Volume Period of Runoff Volume of Runoff Volume Change Change (years) (c.f.s.) (ac. ft.) (c.f.s.) (ac. ft.) (c.f.s.) (c.f.s.) 2 0.85 0.061 0.80 0.064 -0.05 +.003 (-5.8%) (+4.9%) 10 1.66 0.118 1.52 0.117 -0.14 -0.001 (-8.40)/0) (-0.8%) May 27, 2016 Page 5 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 RUNOFF FROM MAIN PORTION OF FRONT OF SITE TO BROOK (EXISTING HYDROCAD NODE 1 E, PROPOSED NODE BP1) 25 2.30 0.164 2.10 0.161 -0.20 -.003 (-8.7%) (-1.8%) 100 3.71 0.269 3.41 0.261 -0.30 -.008 1 1 1 1 1 (8.0%) 1 (-2.9 RUNOFF FROM SOUTHWEST PORTION OF FRONT OF SITE TO WAYNE ST (EXISTING HYDROCAD NODE 2E, PROPOSED NODE 2P) Storm Existing Existing Proposed Proposed Peak Runoff Return Peak Runoff Peak Rate Runoff Rate Volume Period Rate of Volume of Runoff Volume Change Change (years) Runoff (ac. ft.) (c.f.s.) (ac. ft.) (c.f.s.) (c.f.s.) (c.f.s.) (%) (%) 2 0.12 0.009 0.13 0.010 +0.01 +.001 (+8.3%) (+11.1%) 10 0.26 0.018 0.25 0.019 -0.01 +.001 (-3.8%) (+5.6%) 25 0.37 0.026 0.35 0.027 -0.02 +.001 (-5.4%) (+3.8%) 100 0.61 0.044 0.58 0.045 -0.03 +.001 I 1 1 1 (-4.9%) 1 (+2.3%) 1 RUNOFF FROM SOUTHERN PORTION OF FRONT OF SITE TO OSGOOD STREET AT WAYNE STREET (EXISTING HYDROCAD NODE 3E, PROPOSED NODE 3P) Storm Existing Existing Proposed Proposed Peak Runoff Return Peak Runoff Peak Rate Runoff Rate Volume Period Rate of Volume of Runoff Volume Change Change (years) Runoff (ac. ft.) (c.f.s.) (ac. ft.) (c.f.s.) (c.f.s.) (c.f.s.) (%) (%) 2 0.02 0.001 0.02 0.001 +0.0 +0.0 (+0.0%) (+0.0%) 10 0.04 0.003 0.04 0.003 +0.0 +0.0 (+0.0%) (+0.0%) 25 0.06 0.004 0.06 0.004 +0.0 +0.0 May 27, 2016 Page 6 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 RUNOFF FROM SOUTHERN PORTION OF FRONT OF SITE TO OSGOOD STREET AT WAYNE STREET (EXISTING HYDROCAD NODE 3E, PROPOSED NODE 3P) (+0.0%) (+0.0%) 100 0.11 0.008 0.11 0.008 +0.0 +0.0 I I I 1 (+0.0%) 1 (+0.0 RUNOFF FROM REAR PORTION OF SITE TO BROOK (EXISTING HYDROCAD NODE B2, PROPOSED NODE BP2) Storm Existing Existing Proposed Proposed Peak Runoff Return Peak Runoff Peak Rate Runoff Rate Volume Period Rate of Volume of Runoff Volume Change Change (years) Runoff (ac. ft.) (c.f.s.) (ac. ft.) (c.f.s.) (c.f.s.) (c.f.s.) (%) (%) 2 2.10 0.153 1.78 0.138 -0.32 -0.015 (-15.2%) (-9.8%) 10 3.41 0.255 3.02 0.233 -0.39 -0.022 (-11.4&) (-8.6%) 25 4.39 0.332 3.98 0.308 -0.41 -0.024 (-9.30%) (-7.2%) 100 6.47 0.501 6.11 0.474 -0.36 -0.027 1 1 (-5.5) (-5.3 RUNOFF FROM REAR PORTION OF SITE SOUTHWESTERLY TO WAYNE STREET (EXISTING HYDROCAD NODE 7E, PROPOSED NODE 7P) Storm Existing Existing Proposed Proposed Peak Runoff Return Peak Runoff Peak Rate Runoff Rate Volume Period Rate of Volume of Runoff Volume Change Change (years) Runoff (ac. ft.) (c.f.s.) (ac. ft.) (c.f.s.) (c.f.s.) (c.f.s.) (%) (%) 2 1.42 0.106 1.35 0.100 -0.07 -0.006 (-4.9%) (-5.6%) 10 2.24 0.170 2.13 0.162 -0.11 -0.008 (-4.90%) (-4.7%) 25 2.84 0.220 2.70 0.209 -0.14 -0.011 May 27, 2016 Page 7 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 RUNOFF FROM REAR PORTION OF SITE SOUTHWESTERLY TO WAYNE STREET (EXISTING HYDROCAD NODE 7E, PROPOSED NODE 7P) (-4.9%) (-5%) 100 4.14 0.327 3.93 0.311 -0.21 -0.016 (-5.0) (-4.8%) A review of the above summaries INDICATES THE FOLLOWING: • While there are decreases in the peak runoff from the main portion of front of site to the brook there is a small (0.003 ac. ft. increase in runoff volume from this area for the two year storm. There are decreases in the volume for the 10, 25 & 100 year storms; • For the runoff from southwest portion of front of site to Wayne Street there is a small increase in the peak rate of runoff (0.01 cfs) for the two year storm and small (0.001 ac. ft. increase in runoff volume from this area for the 2, 10) 25 & 100 year storms. These increases are caused by the emergency egress walkways from the connecting lobby and the building addition to Wayne Street. • There are no changes in the runoff from southern portion of front of site to Osgood Street at Wayne Street • There are decreases in the peak runoff rate and runoff volume from the rear portion of site to the brook. These decreases are due to a reduction in impervious surface. These decreases are more than sufficient to mitigate the small increase in runoff volume from the front of the site to the brook for a 2 year storm. • There are decreases in the peak runoff rate and runoff volume from the rear portion of site southwesterly to Wayne Street. These decreases are due to a reduction in impervious surface. Based on the results of the calculations we feel that Standard 2 has been met by the proposed project to the maximum extent practicable. May 27, 2016 Page 8 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 Standard 3: Recharge The proposed project involves the redevelopment of an existing developed site. As such, compliance with Stormwater Standard 3 is required only to the maximum extent practicable and measures must be been taken to improve existing conditions. Test pits conducted in the front portion of the site indicate that the ground is miscellaneous fill which overlays a peat layer. Infiltration into this soil is not practicable. Test pits conducted on the rear portion of the site indicate that the soil is also miscellaneous fill with clay and a high Estimated Seasonal High Ground Water Table rendering infiltration into this soil is not practicable. For these reasons, as well as the fact that the project is a Redevelopment Project and the impervious areas on the site are being reduced, recharge of surface water in not being provided. Standard 4: Water Quality The proposed project involves the redevelopment of an existing developed site. As such, compliance with Stormwater Standard 4 is required only to the maximum extent practicable and measures must be been taken to improve existing conditions. Treatment for the runoff from the majority of the impervious surfaces is provided by new deep sump catch basins with hooded outlets and Stormceptor STC-900 Treatment Units. Attached to this report is a TSS Removal calculation sheet showing the TSS removal for the proposed system. Runoff from a portion of the pavement adjacent to Wayne Street at both the the front and rear of the site is not included in the treatment due to the elevations of the wetlands and the pavement which prohibits the installation of a drainage system to collect and treat the runoff. The sizing of the Stormceptor Unit for the base bid work is based on the MADEP Regulation regarding the sizing for all proprietary stormwater treatment units. The sizing calculations for the Unit are as follows: Impervious Area = 9238 s.f., time of concentration = 0.10 hours WQ F = (qu)(A)(WQV) WQF = (752 csm/in)((9238/43560) acres)(0.0015625 mi2/acre)(0.5 in) WQF ~ 0.13CFS May 27, 2016 Page 9 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 Note: The chosen Unit can treat 3.4 c.f.s. The STC-900 was chosen over the STC-450i as the STC-900 unit can retain 193% as much sediment and 291% as much hydrocarbons as the STC-450i. Attached hereto is data to support the use of the STC-900 unit. Stormceptor is MASTEP accepted with a rating of 2. The sizing of the Stormceptor Unit for the bid alternate work is based on the MADEP Regulation regarding the sizing for all proprietary stormwater treatment units. The sizing calculations for the Unit are as follows: Impervious Area =17499 s.f., time of concentration = 0.10 hours WQF = (qu)(A)(WQV) WQF = (752 csm/in)((8900/43560) acres)(0.0015625 mi2/acre)(0.5 in) WQF ~ 0.23 CFS Note: The chosen Unit can treat 3.4 c.f.s. The STC-900 was chosen over the STC-450i as the STC-900 unit can retain 193% as much sediment and 291% as much hydrocarbons as the STC-450i. Attached hereto is data to support the use of the STC-900 unit. Stormceptor is MASTEP accepted with a rating of 2. The runoff quality from the proposed development represents a significant improvement compared to existing conditions (which has no stormwater treatment) and for the majority of the altered site will meet the 80% TSS Removal Standard of the MADEP 2008 Stormwater Handbook. Therefore, Standard 4 has been met by the proposed project to the extent practicable. Standard 5: Land Uses with Higher Potential Pollutant Loads (LUHPPLs) The portion of the site where the base bid work will be conducted does not contain any activities that are classified as Land Uses with Higher Potential Pollutant Loads as defined by the 2008 MADEP Stormwater Handbook and the 2008 amendments to 310 CMR 10.00 et. seq. (MAWPA Regs), The portion of the site where the bid alternate work will be conducted contains activities that are classified as Land Uses with Higher Potential Pollutant Loads as defined by the 2008 MADEP Stormwater Handbook and the 2008 amendments to 310 CMR 10.00 et. seq. (MAWPA Regs), The proposed project will provide improvements for the storage of materials and collection and treatment of runoff. Therefore Standard 5 has been met by the proposed project to the extent practicable. May 27, 2016 Page 10 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 Standard 6: Critical Areas The proposed project does not discharge stormwater runoff to a critical area as defined by the 2008 MADEP Stormwater Handbook and the 2008 amendments to 310 CMR 10.00 et. seq. (MAWPA Regs). Therefore Standard 6 has been fully met by the proposed project. Standard 7: Redevelopments and Other Projects Subject to the Standards only to the maximum extent practicable The proposed project involves the redevelopment of an existing developed site. As such, compliance with Stormwater Standards 2, 3, 4, 5, and 6 is required only to the maximum extent practicable and measures must be been taken to improve existing conditions. Throughout this report we have listed the areas of compliance with the standards in the 2008 MADEP Stormwater Handbook. The proposed project has been carefully thought through and designed to meet the requirements of stormwater standards 2, 31 41 5 & 6 to the maximum extent practicable. Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control Erosion Control and Construction Sequencing With regard to work proposed on the project and erosion and siltation control, the sequence of activities will generally take place as follows: 1. Prior to general pavement removal, or topsoil stripping, place all erosion controls (siltation control fencing & filtrexx soxx and silt sacks) in the locations shown on the drawings. 2. Damaged or loose siltation control fence and filtrexx soxx shall be replaced as necessary to maintain their function of controlling erosion and siltation. Silt sacks in catch basins shall be replaced as necessary to maintain its function of controlling erosion and siltation. 3. Remove any accumulation of silt or soil build-up behind the filtrexx soxx, straw bales and straw wattles as it occurs. May 27, 2016 Page 11 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 27, 2016 4. Throughout excavation, and grading operations the Contractor shall take other necessary precautions, including installation of temporary drainage w wales, siltation sumps/filtration dams, check dams, straw bales, straw wattles, silt fences, and temporary pipe, to direct and control drainage from disturbed areas on the site so that erosion and siltation is minimal. In addition, no erosion or discharge of silt or larger particles shall occur in wetland areas or onto adjacent properties. 5. Remove all erosion control measures, including the filtrexx soxx, straw bales or straw wattles only when construction is completed, upland surfaces are stabilized and the piped drainage system is fully operational and the removal of the devices has been approved by the Architect/Civil Engineer and the Town of North Andover Conservation Commission. If the Contractor anticipates deviations from the above procedures, he shall obtain written approval from the Architect/Civil Engineer prior to proceeding. Erosion and Sediment Control BMP's The Erosion and Sediment Controls represent the suggested best management practices proposed for the project. The Contractor's approach to controlling stormwater runoff from the site may vary however he must implement appropriate corresponding erosion control measures. The use of erosion and sediment controls are mandatory and must be employed to minimize impacts to adjacent areas during construction. If sediment escapes the construction site, off-site accumulations of sediment must be removed at a frequency sufficient to minimize off-site impacts. The control practices which are required to minimize stormwater pollution during construction must remain functional until disturbed areas have been stabilized. Erosion control products are to be installed and maintained in accordance with manufacturer's specifications and good engineering practices. The most important aspects of controlling erosion and sedimentation are limiting the extent of drainage structures. These fundamental principles will be the key factors in the contractor's control of erosion on the project site. If appropriate, the May 27, 2016 Page 12 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 contractor will construct temporary diversion swales and settling basins or use a settling tank. If additional drainage or erosion control measures are needed, they will be located up-gradient from the straw bales and silt fences. The contractor is responsible for the maintenance and repair of all erosion control devices on-site. All erosion control devices will be regularly inspected. At no time will silt-laden water be allowed to enter sensitive areas (wetlands, streams, and drainage systems). Any runoff from disturbed surfaces will be directed through a sedimentation process prior to being discharged to the existing on site drainage system. The contractor will establish a staging area for the overnight storage of equipment and stockpiling of materials. In the staging area, the contractor will have a stockpile of materials required to control erosion on-site to be used to supplement or repair erosion control devices. These materials will include, but are not limited to filtrexx soxx (filled with compost and ready for use), straw bales, siltation control fence, stakes, erosion control matting, and crushed stone. As mentioned previously, erosion and sedimentation controls will be employed to minimize the erosion and transport of sediment into resource areas during the earthwork and construction phases of the Project. Erosion and sedimentation control measures will be installed prior to site excavation or disturbance and will be maintained throughout the construction period. The contractor is responsible for erosion control on the site and will utilize supplemental erosion control measures to supplement the erosion controls shown on the plans prepared for this project to work with his day to day operations at the site. Primary erosion control techniques proposed include compost filled filtrexx soxx, siltation control fence with straw bale barriers and silt sacks, inlet sediment traps, siltation control dikes, a stabilized construction entrance, temporary diversion channels, and temporary sedimentation ponds when applicable. A detailed description of each technique is discussed below. During the growing season, slope stabilization will be achieved by applying topsoil followed by seeding and mulching as soon as final grades are achieved. Organic mulching, jute netting, geo-textiles, or a combination will be used to stabilize slopes completed outside of the growing season. May 27, 2016 Page 13 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 Best Management Practices (BMPs) Filtrexx Soxx and Silt Fence/Straw bales Erosion control barriers (filtrexx soxx, silt fences with straw bales) will be installed in the locations shown on the drawings or as directed in the field by the Architect/Civil Engineer prior to the start of construction. These barriers will remain in place until all tributary surfaces have been fully stabilized. The barriers will be placed to trap sediment transported by runoff before it reaches the drainage system or leaves the construction site. In areas where high runoff velocities or high sediment loads are expected, silt fencing may be installed adjacent to the straw bale barriers. This semi-permeable barrier made of a synthetic porous fabric will provide additional protection. The filtrexx soxx and siltation fences with straw bale barrier will be replaced as determined by periodic field inspection. The underside of the soxx and straw bales will be kept in close contact with the earth and reset as necessary. Straw bale barriers, straw wattles and siltation fences will be maintained and cleaned until slopes have healthy stands of grass and all proposed paved areas have been paved with the binder course of pavement. Drain System Protection Silt Sack sediment traps supplemented with straw bale erosion checks will be installed at drainage structures and maintained and cleaned until slopes have healthy stands of grass. Catch basins, drain inlets, stormwater treatment units, storm drain pipes and detention basins will be cleaned of sediment and debris after the completion of construction. Sediment collected in structures will be disposed of properly and covered, if stored on-site. • Until tributary areas are stabilized, catch basin inlets will be fitted with Silt Sacks. If intense rainfall is predicted before all tributary areas are stabilized, erosion control measures will be reinforced for the duration of the storm. Downstream areas will be inspected and any sediment removed at the end of the storm. • Unfiltered water will not be allowed to enter pipes from unstabilized surfaces. May 27, 2016 Page 14 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 • Trench excavation will be limited to the minimum length required for daily pipe installation. All trenches will be backfilled as soon as possible. The ends of pipes will be closed nightly with plywood • During construction of the site, silt-laden waters should be intercepted prior to reaching catch basins. Any gross depositions of materials on paved surfaces will be removed by sweeping. • All paved areas will be swept on a weekly basis, as permitted by weather, during the construction period. • Catch basins should be inspected monthly and cleaned in anticipation of the winter season in November and at the same time the roads are swept in the spring. Utility Construction The Contractor will construct utility trenches in a manner that will not direct runoff toward wetlands or to drainage system structures. Stabilization Activities All disturbed surfaces will be stabilized within 14 days after construction in any portion of the project site is completed or is temporarily halted, unless additional construction is intended to be initiated within 14 days. The Contractor will not disturb more area than can be stabilized within 14 days unless the area is to remain active. The Contractor will not disturb more area than can be stabilized within the same construction season. Slope Stabilization The smallest practicable area of land will be exposed at a time. Slopes greater than three-to-one (horizontal to vertical) will be stabilized with seed, organic mulch, jute fabric, or rip-rap, as appropriate, to prevent erosion during construction. After disturbed areas have been stabilized, the temporary erosion control measures will be removed and accumulated sediment will be removed and May 27, 2016 Page 15 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 disposed of in an appropriate location. Disturbed areas will be stabilized with appropriate ground cover as soon as possible. After the removal of temporary erosion control measures, disturbed areas will receive a layer of topsoil for stabilization. Stabilized Construction Entrance Temporary stabilized construction entrance or entrances will be installed at the project site. The purpose of the construction entrance is to remove sediment attached to vehicle tires and to minimize sediment transport and deposition onto public road surfaces. The construction entrance or entrances will be composed of crushed stone which will be replenished as necessary to maintain their proper function. Inspections Although not applicable to the base bid project (since the disturbed area is less than 1 acre if the bid alternate is not accepted), the Contractor shall perform the following inspections for both the base bid and bid alternate work (if accepted) in accordance with the 2012 EPA Construction General Permit Conditions which require routine inspections of the site and careful documentation of events and conditions. The following inspection activities will be completed by a qualified, designated site monitor. • Erosion control, sedimentation prevention, and stormwater management measures will be inspected at least once per week throughout the construction period. • All controls, outfalls, and potential problem areas will also be inspected within 24 hours of any storm exceeding 0.25 inches of precipitation. A log of inspection results will be maintained on-site and will include the name of the inspector, date, major observations, and necessary corrective measures. Built up sediment will be removed when it has reached one-third the height of the silt fence or filtrexx soxx. May 27, 2016 Page 16 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 All needed repairs or modifications will be reported to the contractors to permit the timely implementation of required actions. Where necessary repairs do not pose an immediate concern, repairs or modifications will be implemented within two (2) days of inspection. A report summarizing the scope of the inspection, name(s) and qualifications of personnel making the inspection, the date(s) of the inspection, major observations relating to the implementation of this CPPPP, and actions taken will be made and retained as part of the CPPPP. Maintenance The following maintenance practices will be used by the Contractor to maintain erosion and sediment controls. Maintenance activities will be documented on his Inspection Report. Erosion and sediment control measures and other protective measures must be maintained in effective operating condition. • If site inspections indicate that the BMPs are not operating effectively, maintenance must be performed as soon as possible and before the next storm event whenever practicable to maintain the continued effectiveness of the BMPs. • If existing BMPs need to be modified or if additional BMPs are necessary for any reason, implementation must be completed before next storm event whenever practicable. • Pollution prevention measures must be maintained in good working order. If a repair is necessary, it will be initiated, if practicable, within 24 hours of report. • Accumulated sediment within the catch basin inlet protection must be removed on a weekly basis. • Maintenance and inspection of pollution prevention measures must be continued on the site for as long as a portion of the site remains disturbed. • Stabilization measures will be initiated as soon as practicable on portions of the site where construction has temporarily or permanently ceased. This will occur in NO CASE more than 14 days after construction activities have temporarily or permanently ceased. • If issues are identified at hazardous materials storage areas, corrective actions will be implemented immediately. If leaks or spills are identified procedures outlined in Standard 9 will be followed. May 27, 2016 Page 17 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 Standard 9: Operation and Maintenance Plan An Operation and Maintenance Plan is summarized below and will be incorporated into the construction documents for this project. In accordance with the Stormwater Management Policy issued by the Department of Environmental Protection (DEP), Linden Engineering Partners, LLC has prepared the following Operation and Maintenance Plan for the Improvements To The Public Works Building project. This plan is broken into two major sections. The first section describes construction-related controls and practices. The second section is devoted to the post-construction operation and maintenance plan. Basic Information Owner: Town of North Andover Department of Public Works Contact: Mr. Bruce D. Thibodeau P.E., Director Address: 384 Osgood Street City: North Andover, MA 01950 Good Housekeeping BMP's (Construction and Post Construction Periods) The following good housekeeping practices will be followed onsite during and after the construction project: • An effort will be made to store only enough product required to do the job. All materials stored onsite will be stored in a neat, orderly manner in their appropriate containers and, if possible under a roof or other enclosure • Products will be kept in their original containers with the original manufacturer's label • Substances will not be mixed with one another unless recommended by the manufacture • Whenever possible, all of a product will be used up before disposing of the container • Manufacturer's recommendations for proper use and disposal will be followed May 27, 2016 Page 18 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 • The site superintendent will inspect daily to ensure proper use and disposal of materials CONSTRUCTION PERIOD Refer to Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control for information regarding the erosion and sediment control measures during the construction period. Material Handling and Waste Management Hazardous Products: These practices will be used to reduce the risks associated with hazardous materials. Material Safety Data Sheets (MSDSs) for each substance with hazardous properties that is used on the job site will be obtained and used for the proper management of potential wastes that may result from these products. An MSDS will be posted in the immediate area where such product is stored and/or used and another copy of each MSDS will be maintained in the SWPPP file at the job site construction trailer office. Each employee who must handle a substance with hazardous properties will be instructed on the use of MSDS sheets and the specific information in the applicable MSDS for the product they are using, particularly regarding spill control techniques. • Products will be kept in original containers unless they are not re-sealable • Original labels and material safety data will be retained; they contain important product information • If surplus product must be disposed of, manufacture's or local and State recommended methods for proper disposal will be followed Hazardous Waste All hazardous waste material will be disposed of by the Contractor in the manner specified by local, state, and/or federal regulations and by the manufacturer of such products. Site personnel will be instructed in these practices by the job site superintendent, who will also be responsible for seeing that these practices are followed. May 27, 2016 Page 19 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 Solid and Construction Wastes All waste materials will be collected and stored in accordance with state and federal law in an appropriately covered container and/or securely lidded metal dumpster. All trash and construction debris from the site will be deposited in the dumpster. No construction waste materials will be buried on site. All personnel will be instructed regarding the correct procedures for waste disposal. All waste dumpsters and roll-off containers will be located in an area where the likelihood of the containers contributing to storm water discharges is negligible. If required, additional BMPs must be implemented, such as sandbags around the base, to prevent wastes from contributing to storm water discharges. Sanitary Wastes All sanitary waste will be collected from the portable units a minimum of three times per week by a licensed portable facility provider in complete compliance with local and state regulations. All sanitary waste units will be located in an area where the likelihood of the unit contributing to storm water discharges is negligible. If required, additional BMP's must be implemented, such as sandbags around the base, to prevent wastes from contributing to storm water discharges. Washout Areas The Contractor will provide wheel wash stations and concrete washout areas at the site as described below. Wheel Wash Stations The Contractor will provide wheel wash stations adjacent to the construction entrance which lead directly to a public way or portions of the site outside the limits of work Concrete Washout May 27, 2016 Page 20 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 Trucks will be allowed to washout or discharge surplus concrete or drum wash water on the site, but only in specifically designated diked and impervious washout areas which have been prepared to prevent contact between the concrete wash and stormwater. Waste generated from concrete wash water shall not be allowed to flow into drainage ways, inlets, receiving waters or highway right of ways, or any location other than the designated concrete washout. Waste concrete may be poured into forms to make riprap or other useful concrete products. Proper signage designating the "concrete washout" shall be placed near the facility. The hardened residue from the concrete washout diked areas will be disposed of in the same manner as other non-hazardous construction waste materials or may be broken up and used on site as deemed appropriate by the Contractor. Maintenance of the washout is to include removal of hardened concrete. Facility shall have sufficient volume to contain all the concrete waste resulting from washout and a minimum freeboard of 1 foot. Facility shall not be filled beyond 95% capacity and shall be cleaned out once 75% full unless a new facility is constructed. Vehicle and Equipment Fueling There is a previously established vehicle fueling area at the rear of the site. The fueling area will be inspected and cleaned weekly. Spill Prevention and Control Plan The Contractor will train all personnel in the proper handling and cleanup of spilled materials. No spilled hazardous materials or hazardous wastes will be allowed to come in contact with storm water discharges. If such contact occurs, the storm water discharge will be contained on site until appropriate measures in compliance with state and federal regulations are taken to dispose of such contaminated storm water. It shall be the responsibility of the job site superintendent to properly train all personnel in spill prevention and clean up procedures. In order to minimize the potential for a spill of hazardous materials to come into contact with storm water, the following steps will be implemented: May 27, 2016 Page 21 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 1. All materials with hazardous properties (such as pesticides, petroleum products, fertilizers, detergents, construction chemicals, acids, paints, paint solvents, cleaning solvents, additives for soil stabilization, concrete curing compounds and additives, etc.) will be stored in a secure location, with their lids on, preferably under cover, when not in use. 2. During construction, liquid petroleum products and other hazardous materials with the potential to contaminate groundwater may not be stored or handled in areas of the site draining to an infiltration area, An "infiltration area" is any area of the site that by design or as a result of soils, topography and other relevant factors accumulates runoff that infiltrates into the soil. Dikes, berms, sumps, and other forms of secondary containment that prevent discharge to groundwater may be used to isolate portions of the site for the purposes of storage and handling of these materials 3. The minimum practical quantity of all such materials will be kept on the job site at all times. 4. A spill control and containment kit (containing, for example, absorbent materials, acid neutralizing powder, brooms, dust pans, mops, rags, gloves, goggles, plastic and metal trash containers, etc.) will be provided at the storage site. Catch basin inlet cover blankets and inflatable pipe plugs will be used to seal the openings in the outlet pipes and isolate product in the drainage system should a spill occur. 5. Manufacturer's recommended methods for spill cleanup will be clearly posted and site personnel will be trained regarding these procedures and the location of the information and cleanup supplies. In the event of a spill, the following procedures should be followed: 1. All spills will be cleaned up immediately after discovery. 2. The spill area will be kept well ventilated and personnel will wear appropriate protective clothing to prevent injury from contact with the hazardous substances. May 27, 2016 Page 22 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 3. The project manager and the Engineer of Record will be notified immediately. 4. Spills of toxic or hazardous materials will be reported to the appropriate federal, state, and/or local government agency, regardless of the size of the spill. 5. If the spill exceeds a Reportable Quantity, MADEP must be notified and provided with a description of the release, the circumstances leading to the release, and the date of the release and all abatement and followup measures implemented. The job site superintendent will be the spill prevention and response coordinator. He will designate the individuals who will receive spill prevention and response training. These individuals will each become responsible for a particular phase of prevention and response. The names of these personnel will be posted in the material storage area and in the office trailer onsite. Allowable Non-Stormwater Discharge Management Certain types of will be allowed under the conditions that no pollutants will be allowed to come into contact with the water prior to or after its discharge. The control measures that have been outlined previously in this O & M Plan will be strictly followed to ensure that no contamination of these non-stormwater discharges takes place. The following non-stormwater discharges that may occur from the job site include: • Discharges from fire-fighting activities • Fire Hydrant flushings • Waters used to wash vehicles where detergents are not used • Water used to control dust in accordance with off-site vehicle tracking • Potable water including uncontaminated water line flushings • Routine external building wash down that does not use detergents • Pavement wash waters where spills or leaks of toxic or hazardous materials have not occurred (unless all spilled material has been removed) and where detergents are not used May 27, 2016 Page 23 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 • Uncontaminated air conditioner compressor condensate • Uncontaminated ground water or spring water • Foundation or footing drains where flows are not contaminated with process materials such as solvents • Uncontaminated excavation dewatering • Landscape irrigation POST CONSTRUCTION PERIOD Post-Construction BMP's Several types of structural and non-structural water quality controls in various combinations are proposed to treat stormwater generated on the site. These measures include deep sump catch basins with hoods and stormwater treatment units. These Water quality treatment measures will result in the removal of a minimum of 80 percent of the total suspended solids JSS) load in runoff prior to discharge from the site, consistent with DEP's TSS removal standard. The following best management practices are specified in the proposed development program to mitigate the increase in stormwater runoff from the site. B M Ps Used ➢ Drainage Inlet with Deep Sump ➢ Stormceptor Proprietary Treatment Unit Post-Development Activities 1. Paved Areas: Paved Areas shall be mechanically swept during the dry weather to remove excess sediments, thereby reducing the amount of sediments that the drainage system will have to remove from the runoff. Paved areas shall be mechanically swept a minimum of once each year (in the spring). 2. The use of salt or chemicals for de-icing on the paved areas during the winter months shall be limited to the amount necessary to maintain pedestrian and vehicle safety. May 27, 2016 Page 24 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 275 2016 3. Catch Basins with Deep Sump and Hood: The catch basins shall be inspected at least four times/year and at the end of the snowfall and foliage seasons to verify that the inlet openings are not clogged by debris. Debris shall be removed from the grates and disposed of properly. The catch basin sumps shall also be inspected and cleaned a minimum of four times per year and whenever the depth of the sediment is 25% or more of the sump depth or a minimum of twice annually. Material shall be removed from the drain inlet and disposed of in accordance with all applicable regulations. 4. The Stormceptor Stormwater Treatment Unit shall be cleaned and inspected a minimum of four times per year for the first year and twice per year thereafter if the silt trap is not full the in six months. Cleaning shall be in strict conformance with the manufacturer's recommendations which are attached to this report. All maintenance responsibilities as identified on the site plans and within this document will be owned and maintained by the owner of the property and shall run with the title of the property. Annual Operating Budget The estimated annual operating budget for the O & M Plan for the base bid project is $ 750. The estimated annual operating budget for the O & M Plan for the bid alternate project is $ 1,250. Plan of BMP's Reference is made to the project plans for the location of all BMP's. Conclusion The construction of the proposed site development as proposed will provide runoff control for the completed development as required by the MADEP Stormwater Standard 10: Prohibition of Illicit Discharges May 27, 2016 Page 25 of 23 STORMWATER REPORT TOWN OF NORTH ANDOVER DEPARTMENT OF PUBLIC WORKS, IMPROVEMENTS TO THE PUBLIC WORKS BUILDING 384 OSGOOD STREET, NORTH ANDOVER, MA MAY 27, 2016 As provided for in the 2008 MADEP Stormwater Handbook and the 2008 amendments to 310 CMR 10.00 et. seq. (MAWPA Regs) an Illicit Discharge Compliance Statement is not attached to this Stormwater Report. However, the project has been designed to avoid illicit discharges. As provided for in the MADEP Stormwater Regulations, an Illicit Discharge Compliance Statement will be completed prior to the discharge of any stormwater to the post-construction BMP's. Therefore, Standard 10 has been fully met by the proposed project. May 27, 2016 Page 26 of 23