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MEMORANDUM
To: Alex Jordan, Plan Review Coordinator – City of Carmel Engineering Department
From: Brian Stephens-Hotopp P.E. – VS Engineering
Date: 10/08/2019
Re: 10155 Ditch Road Plan Set, Variance for Drainage Proposed Release Rates
Alex,
VS Engineering is requesting a variance from the City’s requirement for the Proposed Release Rate to be higher than the calculated allowable release rates of 0.1 cfs/acre for the 10-year
storm event and 0.3 cfs/acre for the 100-year storm event. The proposed calculated release rates for 10155 Ditch Road are 5.07 cfs for the 10-year storm event and 12.98 cfs for the
100-year storm event. The existing site generally drains from Ditch Road to the west towards Spring Mill Run located along the eastern property boundary. The proposed project is separated
into two separate watershed areas, 1S and 2S. Watershed 1S will be developed and detained into a proposed pond. The proposed release rates for flows from Watershed 1S are below the
allowable release rates. Watershed 2S is not changed from existing conditions less the addition of a new 0.05 acre drive, this watershed is not able to be detained, contributing to
high proposed release rates. See enclosed plan set and drainage report for the necessary sheets to review.
Sincerely,
/
Brian Stephens-Hotopp, P.E.