2608 Sp Deminimus Calculations

Job: Sheet No. Calc by: Check by:

Sharon Hills SCS

1 of Date Date

De Minimus Calculations 80% TSS removal must be achieved on an average weighted basis from the site as a whole using the "Weighted Average Method". (from Vol. 3, Ch. 1, Page 35, Massachusetts Stormwater Handbook) Weighted Average %=

(Area1)(TSS1%)+(Area2)(TSS2%)+(Arean)(TSSn%) (Area1+Area2+Arean)

Drainage Areas Area Size (ac) TSS Removal (%) (AreaXTSS) Re2 0.34 97% 0.3298 Re3 0.07 97% 0.0679 P33 0.21 78% 0.1638 SUM= 0.62 SUM= 0.5615 Weighted Average %= (Area1)(TSS1%)+(Area2)(TSS2%)+(Area3)(TSS3%)+(Area4)(TSS4%)…. (Area1+Area2+Area3 +Area4+...) =

2 Year Q (P33)

= = 0.65

0.5615 0.62 0.91

91% cfs

Meets Deminimus for Treatment Meets Deminimus for Discharge (<1 cfs)

1 11/7/2008