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TREATMENT It is proposed to construct a skimmer within the detention basin and at the curb outlets to treat the runoff water from the site. The watershed's desire is to treat the 1-yr storm while ma_ntaining a maximum velocity of 0.5 fps through the skimmer. Since the runoff from the present site is not treated and due to the large size of skimmers needed to reduce the velocity to 0.5 fps, it is pro- posed to maintain a ve locity P of 1.0 fps through the Eastern and Northwestern skimmers and a velocity of 2.0 fps through the southern skimmer. No skimmer will be provided for the Northeastern area since the drainage flows directly to County Road C. SOUTHERN AREA Q1 = 14.9 cfs Q = V x A , A = Q/V = 14.9 cfs/2.0 fps = 7.5 sq. ft. Using 6" x 6" posts for construction of the skimmer, the vertical flow dim- ension is 6" = 0.5', therefore, the minimum length of skimmer board required = 7.5 sq. ft./O.5 ft. = 15.0 ft. EASTERN AREA Q1 = 7.4 cfs Q = V x A, A = 7.4 cfs/1.0 fps = 7.4 sq. ft. Using 6" x 6" posts, skimmer board required = 7.4 sq. ft./0.5 ft. = 14.8 ft. NORTHWESTERN AREA Q1 = 8.0 cfs Q = V x A, A = 8.0 cfs/1.0 fps = 8.0 sq. ft. Using 6" x 6" posts, skimmer board required = 8.0 sq. ft./O.5 ft. = 16.0 ft. CONTROL OF RUNOFF EASTERN AREA The peak discharges for the 1-year and 100-year storms will be controlled by a two -staged outlet structure attached to the skimmer. + Orifice formula: Q = 0.6 x II x r2 x (2 x 32.2 x H)1/2 , r = 0.625 Ft. Weir formula: Q=3.33x (L-0.2xH) xH1.5, L=8.2ft. DISCHARGE RESULTS Elevation Head (ft.) Discharge (cfs) 836.0 0.0 0.0 837.0 1.0 5.9 1-yr. level 837.5 1.5 7.4 100-yr. level 838.0 2.0 17.9 OTHER AREAS The other drainage areas will not be controlled by a structure (other than a skimmer), but will have discharges consistent with predeveloped conditions.