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Date: December 13,x.010 <br /> Y <br /> Project No.- .11009.00 <br /> Peal discharge rates for the 2,10,25 and 100 year storms were evaluifted.for the proposed and <br /> existing conditions using a HydroCAD model base on MRCS Technical Release 20(TR-20). Th <br /> Type III, -hour storm evert for Barnstable County for the 2,10,25,and 100-year events are 3.5,4.8, <br /> 5.7,and 7.2 inches,respectively..Runoff coefficients for the pre-and post-development t~ nditions <br /> were determined using DRGs Technical release TR-55 methodology as provided in HydroCAD. . <br /> The results c the analysis indicate that there is no increase in peak discharge rates between the pre- <br /> and post--development conditions for the 2,10, 5,and 100-year stormvents. The results for the <br /> peals discharge rates are shown in Table 1 keel : <br /> Table 1 <br /> Peak Discharge Rates ( fa*) <br /> Design Point 1 -y ar o-year -year 100 ar <br /> Existing 12 5.2 .0 <br /> Proposed 2.8 4.6 5.8 8.0 <br /> *Expressed in cubic feet per second <br /> In conclusions,with the decrease in impervious area,the post-development st rmwater runoff <br /> conditions will not exceed pre-development conditions as shown in Table 1). Based on this,n <br /> negative stormwater impacts are anticipated by the redevelopment of this site. <br /> Attachments: Figure 1 -Site Focus Map <br /> Figure 2-FEMA Flood Insurance Rate Map <br /> Attachment 1--DRGs Soil Surrey <br /> Documents and Setti ngs\dgriecd Local Settings\Temporary Internet Files\Content.MSO\11009,00-Site Drainage Memo.doc <br />