Montclair Stables Drainage Report 1 10 25

Drainage Area D includes the easterly half of the barn roof, a gravel driveway to the east of the barn, existing paddocks, a small portion of adjacent Lot 132, the site area to the rear of the barn, a portion of Nicholas Avenue, and a portion of the existing bridle path on Lots 1 and 2 in Block 152.26. The total area is 54, 179 square feet. Drainage Area D drains into a riprap swale and open ended 15” RCP pipe and ultimately though the same municipal drainage system as Drainage Area C. Drainage Area E includes 14,677 square feet that drain toward Nicholas Avenue. This drainage area is near the southwest corner of the site and consists of a portion of the existing sand riding arena. PROPOSED DRAINAGE IMPROVEMENTS Under present conditions, no formal drainage system exists for the parking lot and roof runoff simply drips from the roofs onto the ground. 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 12” 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. Disregarding any infiltration that will occur during a rainfall event, we estimate that the riding arena will be able to store approximately 4 ½” of rainfall. 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

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 A is located at the west side of the site and is a smaller version of Existing Drainage Area A due to the interception of runoff by the new riding arena and the parking lot construction. The area tributary to Lots 162 and 172 will be 10,971 square feet. Post Construction Drainage Area B contains 19,252 square feet of area and still includes most of the front of the site. The net area will be reduced by approximately 3,400 square feet due to the outdoor riding arena construction. Runoff from the western half of this drainage area will now be directed into the existing storm drain system, thereby reducing the amount of curbline flow to the downstream inlet in Woodland Avenue. The lower level will be constructed over a crawl space having a concrete floor to provide for the existing flood storage capacity of the property to remain after construction. The lower floor will be set at least one foot above the flood hazard area design flood elevation. The handicapped accessible parking space and access aisle will be constructed as a slab on-grade. Page 2