Drainage Report and Supplement 82625

Drainage Area E-1 includes the front yards of the buildings, a small portion of the roof area, the existing paved parking lot and most of Lot 176. Area E-1 drains to Woodland Avenue. The surface area is 32,101 square feet. Drainage Area E-2 includes the remainder of the study area and has 143,746 square feet of surface area. This drainage area drains toward Nicholas Avenue with a slight portion of it draining toward the residential properties on Terrace Avenue and Nicholas Avenue. The portion of Nicholas Avenue that the Applicant proposes to improve is also included in drainage area E-1. Under present conditions, no formal drainage system exists for the parking lot and runoff from the roofs simply drips from the roof edges onto the ground. PROPOSED DRAINAGE IMPROVEMENTS The applicant proposes to construct a drainage system for the re-configured parking lot which will include a type D inlet, 15” RCP pipe, and a doghouse manhole at the connection point to the existing storm drain in Woodland Avenue. A road opening permit will be required for this work. The applicant also proposes installing gutters on the barn and on the indoor riding arena. Downspouts will be piped to collector pipes which will connect to the existing drainage systems as shown on Sheet SE-4 of the application set. The reconstruction of the outdoor riding arena will also be an improvement to stormwater runoff and groundwater recharge. The new arena will be totally level and will capture the rainfall over its entire area. The arena will consist of a 6” thick sand surface over a layer of filter fabric over a 15” thick layer of 1 ½” clean crushed stone. The subgrade below the stone will be scarified prior to stone installation. A flush concrete curb will surround the entire arena and will serve to confine the sand and stone as well as rainfall. A subsurface bulkhead wall will be installed to separate the sections of the new riding arena that will drain toward Nicholas Avenue and toward Woodland Avenue. Each section of the riding arena will have an independent perforated pipe subdrain with the inverts being 3” above the soil subgrade. At maximum capacity, we estimate that the riding arena will be able to store approximately 4 ½” of rainfall in the clean stone bed. The Applicant also proposes to locate, expose, and make any necessary repairs to an existing inlet that is part of the municipal

be able to store approximately 4 ½” of rainfall in the clean stone bed. The Applicant also proposes to locate, expose, and make any necessary repairs to an existing inlet that is part of the municipal drainage system in Nicholas Avenue. This inlet was identified on the original topographic survey but is not visible at this time. POST CONSTRUCTION DRAINAGE AREAS. Post Construction Drainage Area P-1 contains 32,238 square feet of area including most of the front yards of the buildings, a small portion of the building roofs, the re-configured parking lot and 11,500 square feet of the re-configured riding arena. Drainage area P-1 drains toward Woodland Avenue Post Construction Drainage Area P-2 contains143,609 square feet of surface area including most of the building roof area, the courtyard between the riding ring and the barn, the paddocks and driveway at the east end of the site, 22,575 square feet of the sand riding arena, the paddocks at the west end of the site and the portion of Nicholas Avenue under consideration. Page 2.