To: Ms. Mary Barry Date: April 4, 2018 Chair, Barnstable Planning Board Project #: 14147.00 From: Jocelyn Mayer, PE Re: Stormwater Memorandum Griffin Ryder, PE Cape Cod Mall – Sears Repositioning Hyannis, Massachusetts Project Description & Introduction The Applicant, Mayflower Cape Cod, LLC, is proposing to redevelop a portion of the Cape Cod Mall, located at 793 Iyannough Road in the village of Hyannis in Barnstable, Massachusetts (the Site). The Project will include building modifications to accommodate new tenants within the exiting Sears anchor space, demolition of the existing 13,250- square foot Sears Auto building, reconfiguration of the eastern parking lot, access improvements, accessible parking upgrades, and associated landscape improvements. With the exception of the accessible parking upgrades, the majority of the work associated with this Project will be limited to the eastern most parking lot, encompassing approximately 10-acres of the 35.57-acre mall parcel. The Cape Cod Mall property is generally bounded by Iyannough Road to the north, Falmouth Road/ commercial properties to the south, a Marriott Courtyard to the east, and Enterprise Road/ commercial properties to the west. See Figure 1, Site Locus Map. Existing Conditions Under existing conditions, the mall property is almost entirely impervious and is occupied by the mall building and associated parking. There are landscaped islands scattered throughout the existing parking fields, a planting strip along Iyannough Road and a buffer along portions of the eastern perimeter of the property. Between Iyannough Road and the front of the Mall, the Sites topography generally slopes down from the roadway at elevation 55 (NAVD88) to elevation 43 at an approximate 4.5% slope. The topography to the east of the building within the parking lot is generally flat with steeper slopes within the drive aisle adjacent to the eastern building face. Under existing conditions stormwater within the project area is collected by catchbasins and piped via a closed pipe drainage system to an existing detention basin to the south of the mall. According to the National Resources Conservation Service (NRCS), surface soils on the Site include Urban Land. Based on geotechnical investigations in the area of proposed infiltration on-site soils are primarily sands, classified as Hydrologic Soil Groups (HSG) A. Based on the soil evaluation the Site is considered to be within an area of rapid infiltration (soils with a saturated hydraulic conductivity greater than 2.4 inches per hour). Proposed Conditions The majority of the site work is associated with the demolition of the existing 13,250-sqaure foot Sears Auto building and reconfiguration of the existing parking lot to the east of the Mall. The existing right-out onto Iyannough Road will be modified to incorporate a right-in/ right-out driveway and a new sidewalk will be constructed to provide a pedestrian connection from Iyannough Road to the new retail tenants. Overall, the Project will increase landscape and open space areas, resulting in a reduction of approximately 16,170-square feet in impervious area. The 101 Walnut Street PO Box 9151 Watertown, MA 02472 -4026 \\vhb\proj\Wat-LD\14147.00 Simon CC Mall\reports\Stormwater\14147.00_Stormwater Report.docx P 617.924.1770 Ref: 14147.00 April 4, 2018 Page 2 redevelopment project will maintain existing grading and drainage patterns to the maximum extent practicable. The Project is not subject to the Massachusetts Stormwater Management Standards as it is not located within a jurisdictional area as defined by the Wetlands Protection Act (WPA), however the Project has been designed to meet the Stormwater Management Standards in addition to providing for enhanced nitrogen removal, improvements to water quality as well as increase stormwater recharge. Under proposed conditions, approximately 60,900-sqaure feet of pavement within the east parking lot will sheet flow toward proposed bioretention basins located within the new landscaped islands. The planted bioretention basins will enhance nitrogen removal and provide for 0.52-inches of water quality treatment, both improvements compared to existing condition. Furthermore, the basins are sized to exceed the 1-inch water quality volume required for the 13,250 square feet of roof top area that is being converted to pavement with the demolition of the Sears Auto building. The bioretention basins are equipped with stone diaphragms sized to provide adequate pretreatment and ultimately provide for 90% TSS removal prior to infiltration. The Project will increase landscape and open space areas, resulting in a reduction of approximately 16,170-square feet of impervious area. The increase in pervious area on site will allow more stormwater to infiltrate, thus reducing peak discharge rates. Figures • Figure 1: Site Location Map • Figure 2: Existing Conditions Figure • Figure 3: Proposed Conditions Figure Attachments • Attachment 1 o NRCS Soil Survey o Geotechnical Boring Logs & Gradation Summaries • Attachment 2 o TSS Removal Calculations o Water Quality Volume Calculations • Attachment 3 o Long Term Best Management Practices – Maintenance/Evaluation Checklist \\vhb\proj\Wat-LD\14147.00 Simon CC Mall\reports\Stormwater\14147.00_Stormwater Report.docx \\vhb\proj\Wat-LD\14147.00 Simon CC Mall\reports\Stormwater\Figures\14147.00 Locus Map.dwg Iyannough Road/Route 132 PROJECT LOCATION Bearses Way 132 28 Falmouth Road/Route 28 Barnstable Locus Map Figure 1 0 100.0002200.0004 400.0008Feet Cape Cod Mall Sears Redevelopment 793 Lyannough Road 3/15/2018 Barnstable (Hyannis), MA \\vhb\proj\Wat-LD\14147.00 Simon CC Mall\reports\Stormwater\Figures\14147.00-Drainage Figures.dwg ROUTE 132 (IYANNOUGH ROAD ROAD) Way Legend X X EX CAPE COD MALL Cape Cod Mall Cod Cape CINEMA 1 Existing Conditions Figure 2 0 50 100 200Feet Cape Cod Mall Sears Redevelopment April 04, 2018 Barnstable (Hyannis), MA \\vhb\proj\Wat-LD\14147.00 Simon CC Mall\reports\Stormwater\Figures\14147.00-Drainage Figures.dwg ROUTE 132 (IYANNOUGH ROAD ROAD) Way Legend X X PROPOSED RETAIL GFA=46,050± SF FFE=44.9± PROPOSED RETAIL GFA=77,450± SF FFE=44.9± 1 CAPE COD MALL EXISTING Mall Cod Cape CAPE COD MALL CINEMA 2 1 Proposed Conditions Figure 3 0 50 100 200Feet Cape Cod Mall Sears Redevelopment April 04, 2018 Barnstable (Hyannis), MA Ref: 14147.00 April 4, 2018 Page 3 ° Attachment 1 o NRCS Soil Survey o Geotechnical Boring Logs & Gradation Summaries \\vhb\proj\Wat-LD\14147.00 Simon CC Mall\reports\Stormwater\14147.00_Stormwater Report.docx Hydrologic Soil Group—Barnstable County, Massachusetts 70° 18' 22'' W 22'' 18' 70° W 9'' 17' 70° 391300 391400 391500 391600 391700 391800 391900 392000 392100 392200 392300 392400 392500 392600 392700 392800 392900 41° 40' 21'' N 41° 40' 21'' N 4614200 4614200 4614100 4614100 4614000 4614000 4613900 4613900 4613800 4613800 4613700 4613700 4613600 4613600 4613500 4613500 4613400 4613400 4613300 4613300 Soil Map may not be valid at this scale. 4613200 4613200 41° 39' 45'' N 41° 39' 45'' N 391300 391400 391500 391600 391700 391800 391900 392000 392100 392200 392300 392400 392500 392600 392700 392800 392900 Map Scale: 1:7,730 if printed on A landscape (11" x 8.5") sheet. Meters 70° 17' 9'' W 9'' 17' 70° 70° 18' 22'' W 22'' 18' 70° N 0 100 200 400 600 Feet 0 350 700 1400 2100 Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 19N WGS84 Natural Resources Web Soil Survey 3/1/2018 Conservation Service National Cooperative Soil Survey Page 1 of 4 Hydrologic Soil Group—Barnstable County, Massachusetts MAP LEGEND MAP INFORMATION Area of Interest (AOI) C The soil surveys that comprise your AOI were mapped at Area of Interest (AOI) 1:25,000. C/D Soils D Warning: Soil Map may not be valid at this scale. Soil Rating Polygons Enlargement of maps beyond the scale of mapping can cause A Not rated or not available misunderstanding of the detail of mapping and accuracy of soil A/D Water Features line placement. The maps do not show the small areas of Streams and Canals contrasting soils that could have been shown at a more detailed B scale. Transportation B/D Rails Please rely on the bar scale on each map sheet for map C Interstate Highways measurements. C/D US Routes Source of Map: Natural Resources Conservation Service Web Soil Survey URL: D Major Roads Coordinate System: Web Mercator (EPSG:3857) Not rated or not available Local Roads Maps from the Web Soil Survey are based on the Web Mercator Soil Rating Lines projection, which preserves direction and shape but distorts Background A distance and area. A projection that preserves area, such as the Aerial Photography Albers equal-area conic projection, should be used if more A/D accurate calculations of distance or area are required. B This product is generated from the USDA-NRCS certified data as B/D of the version date(s) listed below. C Soil Survey Area: Barnstable County, Massachusetts Survey Area Data: Version 14, Oct 6, 2017 C/D Soil map units are labeled (as space allows) for map scales D 1:50,000 or larger. Not rated or not available Date(s) aerial images were photographed: Dec 31, 2009—Mar 22, 2017 Soil Rating Points A The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background A/D imagery displayed on these maps. As a result, some minor B shifting of map unit boundaries may be evident. B/D Natural Resources Web Soil Survey 3/1/2018 Conservation Service National Cooperative Soil Survey Page 2 of 4 Hydrologic Soil Group—Barnstable County, Massachusetts Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Water 7.0 3.3% 245A Hinckley loamy sand, 0 A 16.6 7.8% to 3 percent slopes 245B Hinckley loamy sand, 3 A 4.7 2.2% to 8 percent slopes 264B Eastchop loamy fine A 0.6 0.3% sand, 3 to 8 percent slopes 602 Urban land 183.8 86.4% Totals for Area of Interest 212.8 100.0% Natural Resources Web Soil Survey 3/1/2018 Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group—Barnstable County, Massachusetts Description Hydrologic soil groups are based on estimates of runoff potential.