1600 MADISON ST 2016-01-01 MF Import

! I Section IV. Off-sile Analysis Existin�Conditions On-site The site slopes to the east and contributes runoff to two separate drainage basins. Sitc drainage outlets to the existing storm systems in Colby. 'I lie site was previously developed with single-family residences and a fire station. See Cigure 2. Off-site Llpstream There is no contributory area to the site. Downstream Drainage System Runoff from the north basin enters a catch basin on thc property linc in the existing driveway which outlets runoff to a catch basin in Colby vi� an S" pipe a distance oi appro�cimately 12'. Runoff then turns north and flows through an 8" pipe to anotlier catch basin in Colby approximately 35' noRh. Plow continues north for another 2'' to a storm manhole at the southwest comer of Colby and Madison. There rnnoff turns and flows northeast about 30' to a manhole about G' south of the center lir�e of Madison via a 10 pipe. Plow outlets this manhole and travels east approximately 1025' in a series of 18" pipes. Plow then tums noRhwest via an 18" pipe in Commercial Ave�we to a catchbasin in 1-Ioward a distance of approximately 380'. I�low then travels east and is outside the t/a mile study area. (See Pigure G) Some of the runoff from the south drainage basin reaches an 8" culvert in Colby that flo�vs to a catchUasin approximately 133' south. The remainder of the soudi portion of the site flows into Colby and reaches this same catchbasin. Plow continues south in a series of 12" pipes for a distance o( approximately 3G0'. Plow oudets the 12" pipe into a roadside ditch still travelling south. The runo(f continues south in a series of driveway culverts and open ditches for approximately 440'. Runoff then crosses ColUy in a 12" culvert to the eastside of the road. Clow dien heads south enters another short drivc�vay culvert and retums to open flow heading south. T'he ditch turns ac thc R/�V for Commercial and heads northeast. (See Pigure G) DeveloQed Condition On-site ( On-site drainage will outlet to the catclibasins in Colby. Off-site . No changes in the downstream system are proposed.