Engineering Report. 1 Garfield Circle

Transcription

1 Engineering Report for 1 Garfield Circle a Proposed Office Building in Burlington, Massachusetts Prepared by: DeCelle-Burke and Associates, Inc Furnace Brook Parkway Suite 401 Quincy, MA Prepared for: Barons Custom Homes 4 Bowser Road Lexington, MA April 28, 2016

2 Table of Contents Transmittal Letter Section 1 Project Narrative Existing Conditions Proposed Conditions Stormwater Management Section 2 Section 3 Section 4 Supporting Maps Assessors Map USGS Map FEMA Panel Soils Map Management Plans Stormwater Operation & Maintenance Plan Erosion and Sedimentation Control Plan Stormwater Management Data Standard 3 Compliance Standard 4 Compliance (TSS Removal) HydroCAD Calculations Existing Conditions 2-Year 10-Year 25-Year 100-Year Proposed Conditions 2-Year 10-Year 25-Year 100-Year Watershed Maps

3 SECTION 1 - PROJECT NARRATIVE

4 Existing Conditions The project locus is located at 1 Garfield Circle in Burlington, Massachusetts. The lot is currently developed with a single building that is currently being used as an office. According to the Assessor s Office the property was developed in The property zoning is general Industrial (IG) and the Assessor s lot identification is Map 56 Lot 70. The lot is also located in the Aquifer Protection District. The 22,143 square foot lot is essentially impervious except for some limited grass islands located to the north and south of the parcel where the curb cuts exist. The lot is comprised of the existing 4,400 square foot building whose roof drainage runs over ground, an 18-space paved parking lot in front of the building and a 16-space paved parking lot. All of the pavement on-site is in a deteriorated condition. The site is delineated by deteriorated bituminous berm. The berm follows the limit of the right of way. No sidewalks are present on Garfield Circle. The front parking lot is at elevation 182. The rear parking lot is ten feet lower at elevation 172. All elevations are based on the North American Vertical Datum of 1988 (NAVD 88). The site also has limited on-site stormwater management. The majority of the roof and front parking lot flow uncontrolled into the Garfield Circle gutter and into the town system. The rear of the property inclusive of a portion of the building flows to an on-site catch basin which connects to the town system. All site runoff from the lot is eventually captured by the Garfield Circle drainage system. The building is also serviced by public water, public sewer, and overhead power and communications from the Garfield Circle public layout. The water service is located to the north of the site while the sewer service has no record location. The overhead power and communications is connected to the structure form the south. The site is currently accessed by four curb cuts, two for the upper parking lot and two for the lower parking lot. The driveway for the lower parking lot is one way north to south. There is no significant natural vegetation found on the site and site soils are defined by the Natural Resources Conservation Service (NRCS) as Urban land. However, the soils where examined on April 25, 2016 and coarse gravelly sands were found, with no groundwater observed. The locus soils are classified as hydrological soil group (HSG) A as these soils are very well-drained. Proposed Conditions The proposed project includes a 40-foot by 100-foot foundation with two-story commercial building and walkout basement used for business as well with a 25 on-site parking spaces. The proposed building will be slab-on-grade walk-out, wood-frame structure with access provided on the front and rear of the building. The building will have a two stories above the front parking lot with the second story being 45- feet by 100-feet. The overhang will provide a covered walkway along the front of the building. Access to site will be from three separate re-located and re-adjusted curb cuts off of Garfield Circle. The only southerly curb cut to the site provides one-way access into the upper 20-space parking lot. The other curb cut located to the north of the upper lot provides the egress to Garfield Circle. The other northerly curb cut provides access to the lower driveway and parking area. Stairs lead form the lower parking area to the proposed covered walkway for the building. Handicap parking is available at the front of the building.

5 The existing bituminous berm shall be removed and replaced with new bituminous berm. This will assist in demarking the new curb cut locations and improve the gutter of Garfield Circle. All grading will meet the existing back edge of the traveled way. The pavement proposed for the site will be graded to minimize uncontrolled impervious runoff off site. Stormwater generated from the parking lot and driveways shall be captured by five catch basins. Two are located at the parking lot northerly egress and another catch basin is located at the southerly driveway entrance. Two other catch basins are situated on-site to capture the rear parking lot s runoff. All catch basins have four-foot deep sumps and the outlet is fitted with a pre-treatment device called a Snout. The Snout removes trash, sediment, particulates and floatable pollutants including oil from the stormwater. The catch basin conveys stormwater to an additional pre-treatment device, a drain manhole which also has four-foot deep sumps and a Snout fitted outlet. This tandem treatment train removes the sediment up to 44% as required by DEP s Stormwater Management Standards. All of the site runoff captured by the catch basins and the roof runoff are conveyed to a single underground recharge structure. The recharge structure consists of 32 pre-cast concrete 4 X4 X4 leaching galleys in a four rows of eight configuration with 12 of surrounding stone. The roof runoff is conveyed directly to this underground recharge structure by pipe. The stormwater control structures are designed to control the flow of stormwater offsite during a major rain storm event. The site design will contain all stormwater onsite during a 100-year storm event with some isolated ponding near the northerly catch basin. The proposed drainage system meets current stormwater management regulations by reducing the off-site peak flow, providing for the recharge of stormwater runoff and providing for short and long term stormwater management practices to minimize pollutants entering the storm drain system. In addition to improved stormwater management, the project shall also be serviced by a new sewer service and new domestic water service. Overhead power and communications shall be extended on site as well. A 1-1/2-inch copper water service tapped off the main will supply the building for potable water. The sewer service shall be a 6-inch PVC sewer pipe with a connection to the Garfield Circle sewer main. Power and communications shall be extended from the overhead wires found along Garfield Circle. A riser pipe shall extend down the utility pole and underground conduits will convey the power and communications to the building. All utility connections shall conform to town and utility purveyor requirements. Stormwater Management It is the intent of this report to show compliance with the Massachusetts Stormwater Management Standards (the Standards ). This office generated hydrographs for both existing and proposed conditions to compare overall storm water offsite for various storms. We calculated land coverage numbers (CN) using Hydrologic Group A soils and used minimums for Times of Concentration for both existing and proposed conditions for hydrograph generation. A Rawl s Rate of 8.27 inches per hour was used for exfiltration based on on-site soil testing and observation. Impervious land coverage increases slightly but the majority of runoff will now be treated in the underground stormwater recharge chambers. The runoff for the 2, 10, 25 and 100-year storm events are reduced and the project as proposed exceeds the recharge volume requirement.

6 The results of the calculations are tabulated below for comparison with the existing and proposed condition values. The project also complies with the other stormwater management standards outlined in the Standards. The project complies with the following Standards: Standard 1 - No New stormwater conveyances discharge untreated stormwater directly to the waters of the Commonwealth; Standard 2 - Post Development peak discharge rates are less than pre-development; Standard 3 - The recharge volume required for this project is exceeded. Standard 4 - The project meets the water quality standards. Standard 5 - N/A Standard 6 - N/A Standard 7 - The project is re-development but the project complies with all ten standards. Standard 8 - A demolition and erosion control plan has been prepared for the short term prevention of erosion, sedimentation and the off-site transport of suspended solids. Standard 9 - A Long Term Operation and Maintenance Plan is attached. Standard 10 - Per Standard No. 10 of the MassDEP Stormwater Management Standards, there shall be no illicit discharges to the stormwater management system. The Property Manager is responsible for implementing the Operation and Maintenance Plan and overseeing activities at the facility to prevent illicit discharges to the drainage system from occurring. It is strictly prohibited to discharge any products or substances onto the ground surface or into any drainage structures, such as catch basin inlets, manholes, or drainage outlets that would be a detriment to the environment. HydroCAD calculations are attached for review.

7 Stormwater Runoff Comparison for Pre- and Post-Construction Northerly Flow 2-Year Storm (3.25 ) Existing Conditions (XC-1) Proposed Conditions (DR) Area Description Flow (CFS) Area Description Flow (CFS) Flow off-site 1.28 Flow off-site Year Storm (5.14 ) Existing Conditions (XC-1) Proposed Conditions (DR) Area Description Flow (CFS) Area Description Flow (CFS) Flow off-site 2.06 Flow off-site Year Storm (6.39 ) Existing Conditions (XC-1) Proposed Conditions (DR) Area Description Flow (CFS) Area Description Flow (CFS) Flow off-site 2.54 Flow off-site Year Storm (8.13 ) Existing Conditions (XC-1) Proposed Conditions (DR) Area Description Flow (CFS) Area Description Flow (CFS) Flow off-site 3.28 Flow off-site 2.26

8 Stormwater Runoff Comparison for Pre- and Post-Construction Southerly Flow 2-Year Storm (3.25 ) Existing Conditions (XC-2) Proposed Conditions (PC-2) Area Description Flow (CFS) Area Description Flow (CFS) Flow off-site 0.25 Flow off-site Year Storm (5.14 ) Existing Conditions (XC-2) Proposed Conditions (PC-2) Area Description Flow (CFS) Area Description Flow (CFS) Flow off-site 0.45 Flow off-site Year Storm (6.39 ) Existing Conditions (XC-2) Proposed Conditions (PC-2) Area Description Flow (CFS) Area Description Flow (CFS) Flow off-site 0.57 Flow off-site Year Storm (8.13 ) Existing Conditions (XC-2) Proposed Conditions (PC-2) Area Description Flow (CFS) Area Description Flow (CFS) Flow off-site 0.75 Flow off-site 0.05

9 Section 2 Supporting Maps Assessors Map USGS Map FEMA Panel Soils Map

10 Map 56 Lot 70 DATE: April 28, 2016 TITLE: ASSESSORS MAP SCALE: NOT TO SCALE PREPARED FOR: Baron Custom Homes 4 Bowser Road Lexington, MA PROJECT TITLE: Proposed Office Building 1 Garfield Circle Burlington, MA Furnace Brook Parkway, Suite 401 Quincy, MA (617) (O) (617) (F)

11 DATE: April 28, 2016 TITLE: USGS MAP SCALE: NOT TO SCALE PREPARED FOR: Baron Custom Homes 4 Bowser Road Lexington, MA PROJECT TITLE: Proposed Office Building 1 Garfield Circle Burlington, MA Furnace Brook Parkway, Suite 401 Quincy, MA (617) (O) (617) (F)

12 DATE: April 28, 2016 TITLE: FEMA FLOOD MAP SCALE: NOT TO SCALE PREPARED FOR: Baron Custom Homes 4 Bowser Road Lexington, MA PROJECT TITLE: Proposed Office Building 1 Garfield Circle Burlington, MA Furnace Brook Parkway, Suite 401 Quincy, MA (617) (O) (617) (F)

13 Soils Map provided by a website maintained by the University of California-Davis and supported by the Natural Resources Conservation Service. DATE: April 28, 2016 TITLE: Soils MAP SCALE: NOT TO SCALE PREPARED FOR: Baron Custom Homes 4 Bowser Road Lexington, MA PROJECT TITLE: Proposed Office Building 1 Garfield Circle Burlington, MA Furnace Brook Parkway, Suite 401 Quincy, MA (617) (O) (617) (F)

14 Section 3 Management Plans Stormwater Operation & Maintenance Plan Erosion and Sedimentation Control Plan

15 Stormwater Operation & Site Maintenance Plan for 1 Garfield Circle a Proposed Office Building in Burlington, Massachusetts Prepared by: DeCelle-Burke and Associates, Inc Furnace Brook Parkway Suite 401 Quincy, MA Prepared for: Baron Custom Homes. 4 Bowser Road Lexington, MA April 28, 2016

16 Introduction This Stormwater Operation & Maintenance Plan (OMP) for a 4,500 square foot office building and 25-space parking lot located at 1 Garfield Circle in Burlington, Massachusetts. The OMP is outlined below to provide long term operation and maintenance procedures of the stormwater controls installed to manage the stormwater flow generated on the site and improve runoff quality. The landowner is required to implement the procedures and ensure the long term benefits of the stormwater controls approved and installed for this project. The OMP provides simple operational and maintenance procedures for the stormwater control structures as well as perform various tasks to remove pollutants from areas that would have potential to be picked up on site and moved via stormwater offsite. The landowner shall be responsible to inspect, maintain and operate the stormwater management system as well as inspect the grounds for eroded areas and collected pollutants. Appointing a responsible person in charge to implement this OMP on behalf of the landowner is preferred but the landowners shall be responsible at all times for implementing this OMP. The purpose of the OMP is to maintain the long term benefits from the Stormwater Management features constructed that support groundwater recharge and pollution prevention. Responsible Party - Mark Barons Barons Custom Homes 4 Bowser Road Lexington, MA The responsible party listed above is responsible for inspecting, maintaining and keeping copies of maintenance records for the following plan. If another individual/company is responsible for the every day management of the property the name and contact information shall be made available to the Town of Burlington. The responsible party can expect a yearly budget of $1,000 to $1,200 per year to maintain the site. The responsible party will be referenced as the Manager throughout the rest of this OMP. Non-Structural Operations Parking Lot Sweeping Parking lot sweeping of the surface parking lot will be performed twice during the year, in April- May and in September-October. The Manager shall contract with a company that provides street sweeping services. The contractor shall be a company in good standing in the Commonwealth of Massachusetts and experienced in performing these services. All sweepings shall be disposed of by the hired company off-site in a legal manner. Snow Management Proper snow management practices will be implemented to minimize runoff and pollutant loading impacts. Plowed snow will be placed in pervious areas at the edges of the parking lot where it can slowly infiltrate. Plowed snow will be placed on to pervious areas that are not subject to excessive shade from buildings or vegetation. This will also allow snowmelt to run off onto paved areas and enter the stormwater management facilities. All accumulated sediment from snowmelt shall be removed each spring. If excessive snow inhibits movement around the site or the stormwater management facilities the contractor will be responsible to remove the snow from the site and disposed of in a legal manner. Stormwater Operation & Maintenance Plan Page 2 of 5 Proposed Office Building April 28, Garfield Circle Burlington, MA

17 Structural Operations Catch Basins, Deep Sump Drain Manholes Catch basins and deep sump manholes were installed to remove trash, debris, sediment and a percentage of grease and oil from stormwater. Oil and grease will float on the surface of the pooled water and be trapped by the Snout outlet. To ensure maximum capacity and efficiency, the sumps will be cleaned when half of the available capacity of the deep sump has been used or at a minimum of once per year. The Manager shall inspect the manhole sumps at least twice per year. The catch basins and drain manholes shall be inspected for structural integrity. The frame and grates or covers shall be inspected for cracks, the basin shall be inspected for disintegrating mortar and concrete cracking and the Snout inspected for structural stability. The Manager shall hire a contractor in good standing in the Commonwealth of Massachusetts with experience in cleaning stormwater sumps with a vacuum truck and the inspections of catch basin structures. All sediment and water retrieved from the tanks shall be shall be disposed of by the hired company off-site in a legal manner. The Manager shall provide a written inspection report of which an example form is attached. Underground Leaching Chambers The underground leaching chambers were installed to recharge stormwater runoff from the roof of the building. The benefit of this structural stormwater BMP is groundwater recharge and peak flow attenuation. The responsible party (Manager) shall inspect the chambers using the observation ports brought to surface. The Manager shall check for sedimentation or ponding within the chamber. Sedimentation and ponding will impact the recharge capabilities of the chamber. The chambers shall be inspected a minimum of twice per year or if other evidence requires more frequent inspections such as consistent overflows or breakout is observed. The Manager shall hire a contractor in good standing in the Commonwealth of Massachusetts with experience in cleaning stormwater structures with a vacuum truck. All sediment and water retrieved from the chambers shall be shall be disposed of by the hired company off-site in a legal manner. The Manager shall provide a written inspection report of which an example form is attached. Drain Lines Drain lines convey the stormwater from catch basins to drain manholes and to drain manholes. The Manager shall inspect the drain lines a minimum of once per year to ensure the hydraulic capacity of the pipes are effective. If sediment is observed the sediment shall be removed. All sediment retrieved from the pipes shall be shall be disposed of by the hired company off-site in a legal manner. The Manager shall provide a written inspection report of which an example form is attached. Site Management The entire property shall be inspected on a quarterly basis for rutting, potholes, broken berms, depressions eroded areas and any other site damage caused by vehicular or human activity. The access drive, sidewalks and parking areas shall be inspected for broken pavement, potholes, oxidation, rutting and cracking. If evidence of any deterioration of pavement occurs a pavement repair plan shall be implemented that may include, crack sealing or pavement pitching. Stormwater Operation & Maintenance Plan Page 3 of 5 Proposed Office Building April 28, Garfield Circle Burlington, MA

18 Landscaped areas shall be inspected to identify any erosion or dying plants. If any erosion is observed on site the area shall be raked as necessary to maintain grade and revegetated as needed. A cause of the erosion shall be identified to prevent future incidents. Solutions may include slope reinforcement or minor regarding to prevent channelization of runoff. Grassed areas shall be raked out and seeded as needed to maintain an even vegetated surface. The Manager shall hire a contractor in good standing in the Commonwealth of Massachusetts with experience in paving to repair any potholes, broken berms or other damaged paved area. The Manager shall hire a landscaper in good standing in the Commonwealth of Massachusetts with experience in re-vegetating eroded areas and a pavement contractor in good standing Commonwealth of Massachusetts with experience in repairing existing paved areas and curbing. Record Keeping Records of the inspections and maintenance for the Non-Structural and Structural Operations performed or organized by Manager for the property shall be up to date and available for review and inspection. An example record keeping sheet is attached. Stormwater Operation & Maintenance Plan Page 4 of 5 Proposed Office Building April 28, Garfield Circle Burlington, MA

19 1 Garfield Circle Burlington, MA Office Building Stormwater Operation & Site Maintenance Plan INSPECTION SCHEDULE AND EVALUATION CHECKLIST Best Management Practice Inspection Frequency Date Inspected Contractor Current Conditions and Minimum Maintenance / Repairs, if necessary Completed Maintenance / Repair (i.e. date, contractor, tasks complete, etc...) Street Sweeping Biannual Catch Basins& Drain Manholes Biannual Leach Pits Biannual Parking Lot, Driveways & Sidewalks Quarterly Vegetated Areas Quarterly Overall Site Condition Quarterly Property Manager: Date

20 Erosion Control Plan for 1 Garfield Circle a Proposed Office Building in Burlington, Massachusetts Prepared by: DeCelle-Burke and Associates, Inc Furnace Brook Parkway Suite 401 Quincy, MA Prepared for: Barons Custom Homes 4 Bowser Road Lexington, MA April 28, 2016

21 Proposed Office Building Page 2 of 8 Barons Custom Homes. 1 Garfield Circle Burlington, MA April 28, 2016 Table of Contents Section Plan Objectives Page 3 Section Introduction Page 3 Section Current Site Conditions Page 3-4 Section Project Description Page Proposed Site Conditions Page 4-5 Section Erosion & Sedimentation Control Plan Page Major Const. Sequence for Site Page Best Management Practices Page Dumpster Crushed Stone Apron Erosion Control Barrier Level Spreader Dust Control Disturbed Surface Maintenance Temp. Stormwater Controls DeCelle-Burke & Associates, Inc Furnace Brook Pkwy., #401 Quincy, MA PH: FX:

22 Proposed Office Building Page 3 of 8 Barons Custom Homes. 1 Garfield Circle Burlington, MA April 28, Plan Objectives To protect abutting properties, public ways and drainage infrastructure from construction related pollutant impacts generated from land disturbance and construction activities; Control existing, and potential erosion, sediment transport and pollutant impact events by installing and maintaining construction related Best Management Practices (BMP's) to reduce and/or prevent the discharge of stormwater pollutants into wetland resources of the Commonwealth of Massachusetts; To protect surface stormwater quality, ground water quality, and minimize off-site sediment transport offsite during construction; To prevent local and off-site flooding by controlling peak rates and volumes of stormwater runoff during construction; and To eliminate illicit discharges to stormwater drainage systems that causes pollution during construction Introduction This Erosion and Sedimentation Control Plan (The Plan ) has been devised for the construction of a 4,500 square foot building and new parking lot to be located at 1 Garfield Circle in Burlington, Massachusetts. The purpose of the Plan is to protect the surrounding environment from contaminated stormwater during construction of the development. The stormwater will be treated before release and surfaces stabilized to minimize erosive events by implementing, installing and maintaining construction related Best Management Practices (BMP's) to reduce and/or prevent the discharge of stormwater pollutants into wetland resources of the Commonwealth of Massachusetts. The BMP's are described in the Stormwater Management Standards developed by the Massachusetts Department for Environmental Protection and it is our belief that short term construction related pollution prevention generated from this site can be achieved Current Site Conditions The project locus is located at 1 Garfield Circle in Burlington, Massachusetts. The lot is currently developed with a single building that is currently being used as an office. According to the Assessor s Office the property was developed in The property zoning is general Industrial (IG) and the Assessor s lot identification is Map 56 Lot 70. The lot is also located in the Aquifer Protection District. The 22,143 square foot lot is essentially impervious except for some limited grass islands located to the north and south of the parcel where the curb cuts exist. The lot is comprised of the existing 4,400 square foot building whose roof drainage runs over ground, an 18-space paved parking lot in front of the building and DeCelle-Burke & Associates, Inc Furnace Brook Pkwy., #401 Quincy, MA PH: FX:

23 Proposed Office Building Page 4 of 8 Barons Custom Homes. 1 Garfield Circle Burlington, MA April 28, 2016 a 16-space paved parking lot. All of the pavement on-site is in a deteriorated condition. The site is delineated by deteriorated bituminous berm. The berm follows the limit of the right of way. No sidewalks are present on Garfield Circle. The front parking lot is at elevation 182. The rear parking lot is ten feet lower at elevation 172. All elevations are based on the North American Vertical Datum of 1988 (NAVD 88). The site also has limited on-site stormwater management. The majority of the roof and front parking lot flow uncontrolled into the Garfield Circle gutter and into the town system. The rear of the property inclusive of a portion of the building flows to an on-site catch basin which connects to the town system. All site runoff from the lot is eventually captured by the Garfield Circle drainage system. The building is also serviced by public water, public sewer, and overhead power and communications from the Garfield Circle public layout. The water service is located to the north of the site while the sewer service has no record location. The overhead power and communications is connected to the structure form the south. The site is currently accessed by four curb cuts, two for the upper parking lot and two for the lower parking lot. The driveway for the lower parking lot is one way north to south. There is no significant natural vegetation found on the site and site soils are defined by the Natural Resources Conservation Service (NRCS) as Urban land. However, the soils where examined on April 25, 2016 and coarse gravelly sands were found, with no groundwater observed. The locus soils are classified as hydrological soil group (HSG) A as these soils are very well-drained Project Description Proposed Project The proposed project includes a 40-foot by 100-foot foundation with two-story commercial building and walkout basement used for business as well with a 25 on-site parking spaces. The proposed building will be slab-on-grade walk-out, wood-frame structure with access provided on the front and rear of the building. The building will have a two stories above the front parking lot with the second story being 45-feet by 100-feet. The overhang will provide a covered walkway along the front of the building. Access to site will be from three separate re-located and re-adjusted curb cuts off of Garfield Circle. The only southerly curb cut to the site provides one-way access into the upper 20-space parking lot. The other curb cut located to the north of the upper lot provides the egress to Garfield Circle. The other northerly curb cut provides access to the lower driveway and parking area. Stairs lead form the lower parking area to the proposed covered walkway for the building. Handicap parking is available at the front of the building. The existing bituminous berm shall be removed and replaced with new bituminous berm. This will assist in demarking the new curb cut locations and improve the gutter of Garfield Circle. All grading will meet the existing back edge of the traveled way. The pavement proposed for the site will be graded to minimize uncontrolled impervious runoff off site. DeCelle-Burke & Associates, Inc Furnace Brook Pkwy., #401 Quincy, MA PH: FX:

24 Proposed Office Building Page 5 of 8 Barons Custom Homes. 1 Garfield Circle Burlington, MA April 28, 2016 Stormwater generated from the parking lot and driveways shall be captured by five catch basins. Two are located at the parking lot northerly egress and another catch basin is located at the southerly driveway entrance. Two other catch basins are situated on-site to capture the rear parking lot s runoff. All catch basins have four-foot deep sumps and the outlet is fitted with a pre-treatment device called a Snout. The Snout removes trash, sediment, particulates and floatable pollutants including oil from the stormwater. The catch basin conveys stormwater to an additional pre-treatment device, a drain manhole which also has four-foot deep sumps and a Snout fitted outlet. This tandem treatment train removes the sediment up to 44% as required by DEP s Stormwater Management Standards. All of the site runoff captured by the catch basins and the roof runoff are conveyed to a single underground recharge structure. The recharge structure consists of 32 pre-cast concrete 4 X4 X4 leaching galleys in a four rows of eight configuration with 12 of surrounding stone. The roof runoff is conveyed directly to this underground recharge structure by pipe. The stormwater control structures are designed to control the flow of stormwater offsite during a major rain storm event. The site design will contain all stormwater onsite during a 100-year storm event with some isolated ponding near the northerly catch basin. The proposed drainage system meets current stormwater management regulations by reducing the off-site peak flow, providing for the recharge of stormwater runoff and providing for short and long term stormwater management practices to minimize pollutants entering the storm drain system. In addition to improved stormwater management, the project shall also be serviced by a new sewer service and new domestic water service. Overhead power and communications shall be extended on site as well. A 1-1/2-inch copper water service tapped off the main will supply the building for potable water. The sewer service shall be a 6-inch PVC sewer pipe with a connection to the Garfield Circle sewer main. Power and communications shall be extended from the overhead wires found along Garfield Circle. A riser pipe shall extend down the utility pole and underground conduits will convey the power and communications to the building. All utility connections shall conform to town and utility purveyor requirements Erosion & Sedimentation Control Plan The contractor shall implement an Erosion and Sedimentation Control Plan that protects the surrounding environment from sediment laden stormwater runoff generated during construction activities and from other pollutants generated from construction activities such as litter and dust. Construction sequencing is part of managing a site as is implementing many BMP's that assist in controlling construction related pollutants Major Construction Sequence for Site The sequence is developed to contain all potential sedimentation and erosion incidents that could occur during the construction of the project. The contractor however is responsible to manage the site effectively to control offsite sediment transport which may not be included in this plan. The sequence will coordinate the work within the erosion barrier and coordinate other sedimentation control features to reduce the stress upon a silt fence as well as limit off-site sediment transport. The sequencing is as follows: DeCelle-Burke & Associates, Inc Furnace Brook Pkwy., #401 Quincy, MA PH: FX:

25 Proposed Office Building Page 6 of 8 Barons Custom Homes. 1 Garfield Circle Burlington, MA April 28, 2016 Place safety fence around property to limit access and protect the public. Place erosion control barrier at limit of work where possible. Install silt sacks in catch basins that have potential to capture sediment laden runoff generated form the work site. Place gravel for construction vehicle egress to minimize soil tracking off-site. Raze and remove the existing buildings and dispose of in a legal manner. Remove any and all existing bituminous concrete driveways and dispose of in a legal manner. Remove old drainage structure and dispose of in a legal manner. Have a water truck on-site to minimize fugitive dust during the demolition process. Rough grade lot to control construction site runoff. Excavate for foundation and concrete floor slab. Remove deleterious material from excavation and stockpile at location shown until able to remove from site. Backfill and compact excavation as needed to construct foundation in accordance with the approved plans. Place excavated soils as backfill for foundation if possible to minimize stockpiled soils or have the unusable soils removed from the site. Rough grade ground around foundations and parking lot area to continue to drain toward the site. Tap existing sewer for sewer services and extend service to building. Backfill excavation as soon as possible to minimize stockpiled soils. Install domestic water service and extend to building. Backfill excavation as soon as possible to minimize stockpiled soils. Install electrical and communication conduits. Backfill excavation as soon as possible to minimize stockpiled soils. Begin vertical construction of buildings. Install catch basins, water quality manhole and underground recharge structures for stormwater collection. Install silt sacks once catch basins are installed. Rough grade parking lot area. Clean and remove stone apron during this process. Begin fine grade parking lot area. Place binder for parking lot. Install final landscaping, including hydroseed, plantings, walkways and concrete pads. Install concrete curbs and final pave site. Clean up site. The contractor has several procedures to perform to maintain the site. They include but are not limited to: DeCelle-Burke & Associates, Inc Furnace Brook Pkwy., #401 Quincy, MA PH: FX:

26 Proposed Office Building Page 7 of 8 Barons Custom Homes. 1 Garfield Circle Burlington, MA April 28, 2016 Clean site and erosions control measures sediment as needed, to be inspected on a daily basis. Replace erosion control barrier at limit of work as needed. Barrier to be inspected on a weekly basis. Empty silt sacks after each rain event. Catch basins and manholes to be cleaned once sediment occupies 1/2 the sump available. Structures to be inspected on a weekly basis. Stone apron used for construction egress to be replaced as sediment builds up. Apron to be inspected on a daily basis. Any stockpiled soils to be covered to minimize fugitive dust. Maintain a covered dumpster on site to minimize wind blown debris from littering neighborhood and resource areas. Have a water truck onsite during the demolition portion of the project and during rough grading to minimize fugitive dust Best Management Practices The contractor shall use various types of structural and non-structural methodologies to minimize offsite polluting from construction activities. The following is a list of some BMP's that can be utilized; however, it is the contractor's responsibility to implement his strategies to minimize offsite sediment transport and fugitive dust and trash Dumpster The contractor shall have a dumpster on-site for the disposal of construction debris. The contractor shall cover the dumpster as needed to prevent wind blown debris from becoming litter in the environment Crushed Stone Construction Apron A crushed stone apron shall be installed at the entrance to the site to assist in removing caked soil on construction vehicles tires. The apron shall be a minimum of forty feet long and twenty feet wide. The contractor shall inspect the apron on a daily basis and supplement new stone as needed Erosion Control Barrier An erosion control barrier shall be installed at the downradient Limit of Work and used around the site as needed. If the level spreader is sufficient to provide erosion protection the barrier is not necessary. However, the barrier shall be used around soil stockpiles and localized excavations on site. The barrier needs to be effective in controlling sediment transport and not becoming strained as the project moves forward. The contractor shall inspect the barrier weekly or after a large storm event to identify any stressed areas and replace the barrier as needed. The barrier can be one or many of several types. Staked haybales, a geotextile fabric or a geotextile erosion control sock are typical types of barriers. The DeCelle-Burke & Associates, Inc Furnace Brook Pkwy., #401 Quincy, MA PH: FX:

27 Proposed Office Building Page 8 of 8 Barons Custom Homes. 1 Garfield Circle Burlington, MA April 28, 2016 contractor shall inspect the barriers on a daily basis and repair the barriers as needed Dust Control The use of a water truck or other method to spray water over the site during the dry season to minimize blown dust shall be implemented. The water shall not be excessively spread so erosive forces occur. The contractor shall sweep the pavement once installed and cover stockpiled soils as needed to minimize dust Disturbed Surface Maintenance The contractor shall stabilize the ground surface as needed to prevent erosion. Stabilization of surfaces includes the placement of pavement, rip rap, wood bark mulch and the establishment of vegetated surfaces. Upon the completion of construction of a particular phase, all surfaces should be stabilized even though it is apparent that future construction efforts will cause their disturbance. Vegetated cover should be established during the proper growing season and should be enhanced by soil adjustment for proper ph, nutrients and moisture content. Surfaces that are disturbed by erosion processes or vandalism should be stabilized as soon as possible. Areas where construction activities have permanently or temporarily ceased should be stabilized within 14 days from the date of last construction activity, except when construction activity will resume within 21 days (e.g., the total time period that construction activity is temporarily ceased is less than 21 days). Hydro-mulching of grass surfaces is recommended, especially if seeding of the surfaces is required outside the normal growing season. Mulching may be used for temporary stabilization. Haybale dikes or silt fences should be set where required to trap products of erosion and should be maintained on a continuing basis during the construction process. Wheel ruts should be filled in and graded to prevent concentration of stormwater runoff. Vehicle tracks leading downhill should be blocked during periods of intense precipitation by haybales, dikes or silt fences which should be constructed to entrap the sediment Temporary Stormwater Controls The contractor shall rough grade the site as to not concentrate the stormwater runoff and cause erosive forces. The catch basins and manholes can be installed to assist in capturing the construction site runoff once installed but the tanks will need to be cleaned out of all sediment before connecting the tanks to the recharge system and final paving. The use of silt sacks on the catch basin will help minimize the cleaning of the sumps. The contractor shall sweep the pavement once installed as needed to minimize suspended solids in the stormwater. DeCelle-Burke & Associates, Inc Furnace Brook Pkwy., #401 Quincy, MA PH: FX:

28 Section 4 Stormwater Management Data Standard 3 Compliance Standard 4 Compliance (TSS Removal) HydroCAD Calculations Existing Conditions 2-Year 10-Year 25-Year 100-Year Proposed Conditions 2-Year 10-Year 25-Year 100-Year Watershed Maps

29 Calculation Sheet Project: Client: Date: Proposed Office Building One Garfield Circle Burlington, MA Barons Custom Homes 4 Bowser Road Lexington, MA April 28, 2016 Standard 3 Compliance for Pond 1 Find: Recharge Volume Requirement Given: Rv = (AF) Rv = (impervious area x depth factor) A = 17,505 s.f. impervious area F= 0.6 " for A-soils Solve: Rv = 17,505 s.f. x 0.6 "/12'= c.f. Rv = c.f./43,560 s.f= acre/ft Find: Recharge System Infiltration Rate; i Given: i= A x RR Rawls Rate for in-situ-soils = RR = 8.27 in/hr Recharge System Size 37.2 x 18 = 670 s.f. Solve: i= i= (669.6s.f. x 8.27in/hr)/(12in/ft X 60min/hr X 60sec/min 0.13 cfs DeCelle-Burke Asscociates, Inc Furnace Brook Pkwy., #401 Quincy, MA (o) (f) 1 of 2

30 Calculation Sheet Project: Client: Date: Proposed Office Building One Garfield Circle Burlington, MA Barons Custom Homes 4 Bowser Road Lexington, MA April 28, 2016 Standard 3 Compliance continued. Determine if Recharge System can handle Required Recharge Volume; Rv Given: Rv = acre/ft Recharge Field Height = 6 ft Find: Depth of Rv within Recharge Field Solve: See HydroCAD Calculations Attached Rainfall Depth generating ac/ft is 1.30 in Corresponding Field Depth is = 1.08 ft. DEPTH CHECKS OK Drawdown Time, T Find: T= Rv / (A x RR) Given: Recharge System= 670 s.f. RR= 8.27 in/hr Rv= c.f c.f./(669.6 s.f. x 8.27 in/hr)12in/ft = 1.90 hrs < 72 hrs CHECKS OK DeCelle-Burke Asscociates, Inc Furnace Brook Pkwy., #401 Quincy, MA (o) (f) 2 of 2

31 On-Site Pond On-Site Flow Recharge Subcat Reach Pond Link Routing Diagram for One Garfield Drainage-STD 3 Prepared by DeCelle-Burke & Associates, Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC

32 One Garfield Drainage-STD 3 Prepared by DeCelle-Burke & Associates HydroCAD s/n HydroCAD Software Solutions LLC Type III 24-hr Rainfall=1.30" Printed 5/3/2016 Page 2 Summary for Subcatchment On-Site: On-Site Flow Runoff = hrs, Volume= af, Depth> 0.60" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr Rainfall=1.30" Area (sf) CN Description 4, Roofs, HSG A 13, Paved parking, HSG A 17, Weighted Average 17, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond Pond: Recharge Inflow Area = ac,100.00% Impervious, Inflow Depth > 0.60" Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 73%, Lag= 21.1 min Discarded = hrs, Volume= af Primary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.05 hrs Peak Elev= hrs Surf.Area= 670 sf Storage= 307 cf Plug-Flow detention time= 16.3 min calculated for af (79% of inflow) Center-of-Mass det. time= 9.1 min ( ) Volume Invert Avail.Storage Storage Description #1A ' 853 cf 37.20'W x 18.00'L x 6.00'H Field A 4,018 cf Overall - 1,884 cf Embedded = 2,134 cf x 40.0% Voids #2A ' 1,419 cf Galley 4x4x4 x 32 Inside #1 Inside= 42.0"W x 43.0"H => sf x 3.50'L = 44.3 cf Outside= 52.8"W x 48.0"H => sf x 4.00'L = 58.9 cf 8 Rows of 4 Chambers # ' 645 cf Custom Stage Data (Prismatic) Listed below (Recalc) 2,917 cf Total Available Storage Storage Group A created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) ,

33 One Garfield Drainage-STD 3 Prepared by DeCelle-Burke & Associates HydroCAD s/n HydroCAD Software Solutions LLC Type III 24-hr Rainfall=1.30" Printed 5/3/2016 Page 3 Device Routing Invert Outlet Devices #1 Discarded ' in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 0.00' #2 Primary ' 8.0" Round Culvert L= 20.0' CPP, projecting, no headwall, Ke= Inlet / Outlet Invert= ' / ' S= '/' Cc= n= 0.011, Flow Area= 0.35 sf Discarded OutFlow Max= hrs HW=165.88' (Free Discharge) 1=Exfiltration ( Controls 0.13 cfs) Primary OutFlow Max= hrs HW=164.81' (Free Discharge) 2=Culvert ( Controls 0.00 cfs)

34 Project: Proposed Office Building Location: 1 Garfield Circle Burlington, MA Date: 4/28/2016 Subject: Total Suspended Solids Removal Calculations BMP TSS Start Amount Remaining Removal Load Removed Load 4' Deep Sump Catch Basins 25% 100% 25% 75% 4' Deep Sump Manholes 25% 75% 19% 56% Underground Recharge Chambers 90% 56% 51% 6% Remaining Load 6% 0% 6% DeCelle-Burke & Associates, Inc Furnace Brook Pkwy., #401 Quincy, MA PH:(617) FX:(617)

35 1-XC Northerly Flow 2-XC Southerly Flow On-Site On-Site Flow Pond Recharge 2-PC Southerly Flow 1-PC DR Northerly Flow Northerly Flow Subcat Reach Pond Link Routing Diagram for One Garfield Drainage Prepared by DeCelle-Burke & Associates, Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC

36 One Garfield Drainage Type III 24-hr 2YR Rainfall=3.25" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1-PC: Northerly Flow Runoff = hrs, Volume= af, Depth= 0.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 2YR Rainfall=3.25" Area (sf) CN Description 2, >75% Grass cover, Good, HSG A 2, % Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 1-XC: Northerly Flow Runoff = hrs, Volume= af, Depth> 2.73" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 2YR Rainfall=3.25" Area (sf) CN Description 3, Roofs, HSG A 13, Paved parking, HSG A % Grass cover, Fair, HSG A 17, Weighted Average % Pervious Area 17, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2-PC: Southerly Flow Runoff = hrs, Volume= af, Depth= 0.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 2YR Rainfall=3.25" Area (sf) CN Description 2, >75% Grass cover, Good, HSG A 2, % Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry,

37 One Garfield Drainage Type III 24-hr 2YR Rainfall=3.25" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment 2-XC: Southerly Flow Runoff = hrs, Volume= af, Depth> 2.08" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 2YR Rainfall=3.25" Area (sf) CN Description Roofs, HSG A 2, Paved parking, HSG A % Grass cover, Fair, HSG A 4, Weighted Average % Pervious Area 3, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment On-Site: On-Site Flow Runoff = hrs, Volume= af, Depth> 2.82" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 2YR Rainfall=3.25" Area (sf) CN Description 4, Roofs, HSG A 13, Paved parking, HSG A 17, Weighted Average 17, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Reach DR: Northerly Flow Inflow Area = ac, 88.35% Impervious, Inflow Depth = 0.00" for 2YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= hrs, dt= 0.05 hrs

38 One Garfield Drainage Type III 24-hr 2YR Rainfall=3.25" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 4 Summary for Pond Pond: Recharge Inflow Area = ac,100.00% Impervious, Inflow Depth > 2.82" for 2YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 90%, Lag= 42.8 min Discarded = hrs, Volume= af Primary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.05 hrs Peak Elev= hrs Surf.Area= 670 sf Storage= 1,455 cf Plug-Flow detention time= 80.0 min calculated for af (100% of inflow) Center-of-Mass det. time= 79.3 min ( ) Volume Invert Avail.Storage Storage Description #1A ' 853 cf 37.20'W x 18.00'L x 6.00'H Field A 4,018 cf Overall - 1,884 cf Embedded = 2,134 cf x 40.0% Voids #2A ' 1,419 cf Galley 4x4x4 x 32 Inside #1 Inside= 42.0"W x 43.0"H => sf x 3.50'L = 44.3 cf Outside= 52.8"W x 48.0"H => sf x 4.00'L = 58.9 cf 8 Rows of 4 Chambers # ' 645 cf Custom Stage Data (Prismatic) Listed below (Recalc) 2,917 cf Total Available Storage Storage Group A created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , Device Routing Invert Outlet Devices #1 Discarded ' in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 0.00' #2 Primary ' 8.0" Round Culvert L= 20.0' CPP, projecting, no headwall, Ke= Inlet / Outlet Invert= ' / ' S= '/' Cc= n= 0.011, Flow Area= 0.35 sf Discarded OutFlow Max= hrs HW=168.29' (Free Discharge) 1=Exfiltration ( Controls 0.13 cfs) Primary OutFlow Max= hrs HW=164.80' (Free Discharge) 2=Culvert ( Controls 0.00 cfs)

39 One Garfield Drainage Type III 24-hr 10YR Rainfall=5.14" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 1-PC: Northerly Flow Runoff = hrs, Volume= af, Depth> 0.18" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 10YR Rainfall=5.14" Area (sf) CN Description 2, >75% Grass cover, Good, HSG A 2, % Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 1-XC: Northerly Flow Runoff = hrs, Volume= af, Depth> 4.47" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 10YR Rainfall=5.14" Area (sf) CN Description 3, Roofs, HSG A 13, Paved parking, HSG A % Grass cover, Fair, HSG A 17, Weighted Average % Pervious Area 17, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2-PC: Southerly Flow Runoff = hrs, Volume= af, Depth> 0.18" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 10YR Rainfall=5.14" Area (sf) CN Description 2, >75% Grass cover, Good, HSG A 2, % Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry,

40 One Garfield Drainage Type III 24-hr 10YR Rainfall=5.14" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 2-XC: Southerly Flow Runoff = hrs, Volume= af, Depth> 3.79" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 10YR Rainfall=5.14" Area (sf) CN Description Roofs, HSG A 2, Paved parking, HSG A % Grass cover, Fair, HSG A 4, Weighted Average % Pervious Area 3, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment On-Site: On-Site Flow Runoff = hrs, Volume= af, Depth> 4.55" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 10YR Rainfall=5.14" Area (sf) CN Description 4, Roofs, HSG A 13, Paved parking, HSG A 17, Weighted Average 17, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Reach DR: Northerly Flow Inflow Area = ac, 88.35% Impervious, Inflow Depth > 0.76" for 10YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= hrs, dt= 0.05 hrs

41 One Garfield Drainage Type III 24-hr 10YR Rainfall=5.14" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 7 Summary for Pond Pond: Recharge Inflow Area = ac,100.00% Impervious, Inflow Depth > 4.55" for 10YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 56%, Lag= 10.7 min Discarded = hrs, Volume= af Primary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.05 hrs Peak Elev= hrs Surf.Area= 670 sf Storage= 1,915 cf Plug-Flow detention time= 81.2 min calculated for af (100% of inflow) Center-of-Mass det. time= 80.7 min ( ) Volume Invert Avail.Storage Storage Description #1A ' 853 cf 37.20'W x 18.00'L x 6.00'H Field A 4,018 cf Overall - 1,884 cf Embedded = 2,134 cf x 40.0% Voids #2A ' 1,419 cf Galley 4x4x4 x 32 Inside #1 Inside= 42.0"W x 43.0"H => sf x 3.50'L = 44.3 cf Outside= 52.8"W x 48.0"H => sf x 4.00'L = 58.9 cf 8 Rows of 4 Chambers # ' 645 cf Custom Stage Data (Prismatic) Listed below (Recalc) 2,917 cf Total Available Storage Storage Group A created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , Device Routing Invert Outlet Devices #1 Discarded ' in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 0.00' #2 Primary ' 8.0" Round Culvert L= 20.0' CPP, projecting, no headwall, Ke= Inlet / Outlet Invert= ' / ' S= '/' Cc= n= 0.011, Flow Area= 0.35 sf Discarded OutFlow Max= hrs HW=169.27' (Free Discharge) 1=Exfiltration ( Controls 0.13 cfs) Primary OutFlow Max= hrs HW=169.27' (Free Discharge) 2=Culvert (Inlet Controls fps)

42 One Garfield Drainage Type III 24-hr 25YR Rainfall=6.31" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment 1-PC: Northerly Flow Runoff = hrs, Volume= af, Depth> 0.46" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 25YR Rainfall=6.31" Area (sf) CN Description 2, >75% Grass cover, Good, HSG A 2, % Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 1-XC: Northerly Flow Runoff = hrs, Volume= af, Depth> 5.54" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 25YR Rainfall=6.31" Area (sf) CN Description 3, Roofs, HSG A 13, Paved parking, HSG A % Grass cover, Fair, HSG A 17, Weighted Average % Pervious Area 17, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2-PC: Southerly Flow Runoff = hrs, Volume= af, Depth> 0.46" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 25YR Rainfall=6.31" Area (sf) CN Description 2, >75% Grass cover, Good, HSG A 2, % Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry,

43 One Garfield Drainage Type III 24-hr 25YR Rainfall=6.31" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 2-XC: Southerly Flow Runoff = hrs, Volume= af, Depth> 4.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 25YR Rainfall=6.31" Area (sf) CN Description Roofs, HSG A 2, Paved parking, HSG A % Grass cover, Fair, HSG A 4, Weighted Average % Pervious Area 3, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment On-Site: On-Site Flow Runoff = hrs, Volume= af, Depth> 5.61" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 25YR Rainfall=6.31" Area (sf) CN Description 4, Roofs, HSG A 13, Paved parking, HSG A 17, Weighted Average 17, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Reach DR: Northerly Flow Inflow Area = ac, 88.35% Impervious, Inflow Depth > 1.40" for 25YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= hrs, dt= 0.05 hrs

44 One Garfield Drainage Type III 24-hr 25YR Rainfall=6.31" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 10 Summary for Pond Pond: Recharge Inflow Area = ac,100.00% Impervious, Inflow Depth > 5.61" for 25YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 35%, Lag= 6.0 min Discarded = hrs, Volume= af Primary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.05 hrs Peak Elev= hrs Surf.Area= 670 sf Storage= 2,113 cf Plug-Flow detention time= 76.7 min calculated for af (98% of inflow) Center-of-Mass det. time= 67.6 min ( ) Volume Invert Avail.Storage Storage Description #1A ' 853 cf 37.20'W x 18.00'L x 6.00'H Field A 4,018 cf Overall - 1,884 cf Embedded = 2,134 cf x 40.0% Voids #2A ' 1,419 cf Galley 4x4x4 x 32 Inside #1 Inside= 42.0"W x 43.0"H => sf x 3.50'L = 44.3 cf Outside= 52.8"W x 48.0"H => sf x 4.00'L = 58.9 cf 8 Rows of 4 Chambers # ' 645 cf Custom Stage Data (Prismatic) Listed below (Recalc) 2,917 cf Total Available Storage Storage Group A created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , Device Routing Invert Outlet Devices #1 Discarded ' in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 0.00' #2 Primary ' 8.0" Round Culvert L= 20.0' CPP, projecting, no headwall, Ke= Inlet / Outlet Invert= ' / ' S= '/' Cc= n= 0.011, Flow Area= 0.35 sf Discarded OutFlow Max= hrs HW=170.14' (Free Discharge) 1=Exfiltration ( Controls 0.13 cfs) Primary OutFlow Max= hrs HW=170.14' (Free Discharge) 2=Culvert (Inlet Controls fps)

45 One Garfield Drainage Type III 24-hr 100YR Rainfall=8.13" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment 1-PC: Northerly Flow Runoff = hrs, Volume= af, Depth> 1.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 100YR Rainfall=8.13" Area (sf) CN Description 2, >75% Grass cover, Good, HSG A 2, % Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 1-XC: Northerly Flow Runoff = hrs, Volume= af, Depth> 7.20" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 100YR Rainfall=8.13" Area (sf) CN Description 3, Roofs, HSG A 13, Paved parking, HSG A % Grass cover, Fair, HSG A 17, Weighted Average % Pervious Area 17, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2-PC: Southerly Flow Runoff = hrs, Volume= af, Depth> 1.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 100YR Rainfall=8.13" Area (sf) CN Description 2, >75% Grass cover, Good, HSG A 2, % Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry,

46 One Garfield Drainage Type III 24-hr 100YR Rainfall=8.13" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 12 Summary for Subcatchment 2-XC: Southerly Flow Runoff = hrs, Volume= af, Depth> 6.55" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 100YR Rainfall=8.13" Area (sf) CN Description Roofs, HSG A 2, Paved parking, HSG A % Grass cover, Fair, HSG A 4, Weighted Average % Pervious Area 3, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment On-Site: On-Site Flow Runoff = hrs, Volume= af, Depth> 7.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type III 24-hr 100YR Rainfall=8.13" Area (sf) CN Description 4, Roofs, HSG A 13, Paved parking, HSG A 17, Weighted Average 17, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Reach DR: Northerly Flow Inflow Area = ac, 88.35% Impervious, Inflow Depth > 2.47" for 100YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= hrs, dt= 0.05 hrs

47 One Garfield Drainage Type III 24-hr 100YR Rainfall=8.13" Prepared by DeCelle-Burke & Associates Printed 5/3/2016 HydroCAD s/n HydroCAD Software Solutions LLC Page 13 Summary for Pond Pond: Recharge Inflow Area = ac,100.00% Impervious, Inflow Depth > 7.26" for 100YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 21%, Lag= 3.7 min Discarded = hrs, Volume= af Primary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.05 hrs Peak Elev= hrs Surf.Area= 1,765 sf Storage= 2,389 cf Plug-Flow detention time= 67.7 min calculated for af (95% of inflow) Center-of-Mass det. time= 48.8 min ( ) Volume Invert Avail.Storage Storage Description #1A ' 853 cf 37.20'W x 18.00'L x 6.00'H Field A 4,018 cf Overall - 1,884 cf Embedded = 2,134 cf x 40.0% Voids #2A ' 1,419 cf Galley 4x4x4 x 32 Inside #1 Inside= 42.0"W x 43.0"H => sf x 3.50'L = 44.3 cf Outside= 52.8"W x 48.0"H => sf x 4.00'L = 58.9 cf 8 Rows of 4 Chambers # ' 645 cf Custom Stage Data (Prismatic) Listed below (Recalc) 2,917 cf Total Available Storage Storage Group A created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , Device Routing Invert Outlet Devices #1 Discarded ' in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 0.00' #2 Primary ' 8.0" Round Culvert L= 20.0' CPP, projecting, no headwall, Ke= Inlet / Outlet Invert= ' / ' S= '/' Cc= n= 0.011, Flow Area= 0.35 sf Discarded OutFlow Max= hrs HW=171.69' (Free Discharge) 1=Exfiltration ( Controls 0.33 cfs) Primary OutFlow Max= hrs HW=171.69' (Free Discharge) 2=Culvert (Inlet Controls fps)

48 GENERAL NOTES: GARFIELD CIRCLE ADAMS STREET PROJECT TITLE & LOCATION: PROPOSED OFFICE BUILDING 1 GARFIELD CIRCLE BURLINGTON, MA PLAN TITLE: EXISTING WATERSHED PREPARED FOR: BARONS CUSTOM HOMES 4 BOWSER ROAD LEXINGTON, MA DATE: REVISED: APRIL 28, 2016 JOB NUMBER: SHEET 1 OF SCALE: 1"=20'

49 GENERAL NOTES: GARFIELD CIRCLE ADAMS STREET PROJECT TITLE & LOCATION: PROPOSED OFFICE BUILDING 1 GARFIELD CIRCLE BURLINGTON, MA PLAN TITLE: PROPOSED WATERSHED PREPARED FOR: BARONS CUSTOM HOMES 4 BOWSER ROAD LEXINGTON, MA DATE: REVISED: APRIL 28, 2016 JOB NUMBER: SHEET 2 OF SCALE: 1"=20'