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To: City of Aspen Engineering Dept.
From: Richard Goulding, P.E.
cc: Vince Tomczak
Date: 09/14/2018
Re: 1108 Waters Ave. Stream Margin Memo
The purpose of this memo is to describe the proposed drainage strategies for the 1108 Waters
Avenue remodel to satisfy the requirements of the Stream Margin review. Zone 4 and Roaring
Fork Engineering have recently met with the City of Aspen to discuss these drainage concepts.
The site is located within the Aspen Mountain drainage basin which typically only requires the
water quality capture volume (WQCV) be detained. However, since this project is adjacent to
the Roaring Fork River, full detention of stormwater is planned to prevent any runoff flowing over
the bank and causing erosion.
To mitigate runoff from impervious areas, pervious pavers are planned for the proposed
hardscaped areas within the site. This would include any driving/parking surfaces. Planter
boxes could be used to fully detain any roof drainage. These planter boxes would have weep
holes at the bottom to allow for infiltration into the native soils. We do not believe that drywells
are a feasible storage option due to the assumed high groundwater given the proximity to the
River. The City Engineering Department requires that drywells be 10’ deep and 5’ above
groundwater. The highwater mark is approximately 13’ below the highest point on the site.
RFE performed initial sizing calculations for the stormwater detention volumes. Please see the
attached drawing which includes the roof basin delineations and results.
Richard Goulding, P.E.
592 Highway 133
Carbondale, CO 81623
970-340-4130
richardg@rfeng.biz
Exhibit 11