HomeMy WebLinkAboutFile Documents.1010 E Hyman Ave.0025-2022-BCHO (21) RIVERCITY
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MEMORANDUM
Re: 1010 E. Hyman Avenue,Aspen: Drywell Setback Variance Request
To: Carly McGowan, E.I.T., Project Manager II, City of Aspen Engineering Department
From: Paul Southworth, P.E. River City Consultants
Date: February 24, 2023
Below is a response to each Engineering Comment made on the 1010 E. Hyman Civil Set. City of Aspen
comments received 1/30/2023 and a follow-up email received 1/31/2023. City of Aspen comments are
transposed in black font. River city Consultant's responses to the City's comments are provided in red
font.
Drywell Setback Variance Request
1) Variance in setback distance from ROW is acceptable.Variance from adjacent property line is
not acceptable. Project team must provide either a drainage easement on the adjacent property
or an impermeable liner between drywell and property line to prevent cross-lot drainage. If this
route is chosen, show that the drywell will have adequate percolation that doesn't rely on side
of drywell that drains into impermeable liner.Variance Call out distance from each drywell to
property line with neighboring property and distance between dry well and property line and
ROW. Stormwater drywell must be located 10' away from all property lines and building
foundations.
An impermeable liner has been added by coating the inside of the western half of the primary
dry well with hydraulic waterproofing cement.This waterproofing method was approved by the
Engineering Department per an email received 2/21/23.A variance request memo for the
setback distances with a figure specifying distances of proposed dry wells to property lines,
structures, and the public right-of-way is included with this submittal. Calculations proving the
minimum percolation area can be met without relying on the side of the drywell that drains
towards the impermeable liner are included with the drainage report.
Drainage Report
2) Drainage report shall include calculations that show adequate pipe capacity on-site at 80%full.
Calculations showing adequate pipe capacity on-site at 80%full are included in the drainage
report.
3) Any proposed drainage improvements in the ROW would require a permanent encroachment
license and would be the responsibility of the private property.There are no proposed drainage
improvements in the ROW, so this statement shall be removed.
03/01/2023
ASPEN
BUILDING DEPARTMENT
_ RIVERCITY
CONSULTANTS
The statement regarding City of Aspen ownership of drainage improvements within the public
right of way has been removed from the drainage report.There are no proposed drainage
improvements within the public right of way.
4) Drainage report must state that there will be no potential for cross lot water flow.
Drainage report states that there will be no potential for cross lot water flow.
5) Total V required is not the addition of WQCV+ 100 yr detention. It is whatever is greater. In this
case,the total required volume is 221.4 cu ft.
Total volume required has been updated to be the 100 year detention volume only because the
100 year detention volume is larger than the WQCV.
6) This calculation shall be updated to reflect the foundation drain and the drainage footprint that
will be utilized by the foundation dry well and therefore not available for the stormwater
drywell. Additionally, if the project opts for an impermeable liner to protect the neighboring
property, this calculation shall be updated to reflect actual conditions.
An impermeable liner is proposed to protect the neighboring property. Calculations provided in
the drainage report prove that the percolation area requirement can still be met when
subtracting out the stone on the western side of the primary dry well as well as the stone that
overlaps with the 4-foot foundation drain dry well percolation area.
Civil Plan Set
7) Please add a note on the civil set that the path is snowmelted. Show exact extents.Additionally,
add a note that the snowmelt in the ROW will be on a separate zone and a permanent
encroachment license will be obtained prior to CO.
Sheet C3 has been added to the civil plan set showing snowmelt extents at grade. The requested
note regarding snowmelt in the public right-of-way has been added to the civil plan set.
40AZ
Paul J. Southworth, P.E.
CO Professional Engineer No 60123
RECEIVED
03/01/2023
ASPEN
BUILDING DEPARTMENT