HomeMy WebLinkAboutFile Documents.1265 Mountain View Dr.0031-2021-BCHO (13)1265 MOUNTAIN VIEW DRIVE
LOT 7, WEST MEADOWS
CITY OF ASPEN, COLORADO
DRAINAGE REPORT
Revised: September 12, 2021
August 8, 2021
July 6, 2021
Prepared by
3C GROUP, LLC
4530 Running W DR Gillette, WY 82718 970.875.4411
09/29/2021
Lot 7, West Meadows July 2021
Drainage Report ii
“I hereby affirm that this report and the accompanying plans for the drainage improvements at Lot 7,
West Meadows were prepared by me or under my direct supervision for the owners thereof in
accordance with the provisions of the City of Aspen URMP”
Scott P. Gregory, PE License No. 41690
Licensed Professional Engineer, State of Colorado
09/29/2021
Lot 7, West Meadows July 2021
Drainage Report iii
TABLE OF CONTENTS
1.0 General 1-1
1.1 Project Background and Location 1-1
2.0 Drainage Basins and Sub-basins 2-1
Offsite Drainage 2-1
On-Site Drainage 2-2
3.0 Low Impact Site Design 3-2
4.0 Hydrologic Criteria 4-2
5.0 Hydraulic Criteria 5-2
6.0 Proposed Facilities 6-2
7.0 Maintenance Plan 7-2
8.0 Conclusions 8-3
LIST OF APPENDICES
Appendix A
Existing and Proposed improvement drawings
Appendix B
Proposed Basin Calculations
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Lot 7, West Meadows July 2021
2-1
Drainage Report
1.0 General
1.1 Project Background and Location
The proposed project is located at 1265 Mountain View Dr in this City of Aspen, Pitkin
County Colorado. Currently there is an existing Single-Family Residence, driveway and
landscaping.
This project proposes to remove and replace the existing concrete driveway and parking
area, along with the walkway to the front door and replace them in like kind. There is also
additional landscaping area and xeriscape gravel areas proposed as part of the overall
landscaping plan for the lot. The total affected impervious area is 3,360 square feet.
There are no previous drainage studies to our knowledge
2.0 Drainage Basins and Sub-basins
The overall development of Lot 7 consists of a single-family home consisting of one overall
drainage basin. The proposed drainage patterns as part of the original design are
consistent with historic drainage patterns and represent the existing conditions.
Offsite Drainage
The surrounding lots and cemetery area to the south are not proposed to change, and do
not adversely affect this parcel with respect to offsite runoff. These areas have not been
accounted for in this report due their unchanged status.
There are no offsite drainage basins or flood hazard delineations on the property.
There are no irrigation facilities or waterways in the vicinity of the project. The Roaring Fork
River is approximately 0.25 miles to the northeast of the site and is not impacted with runoff
from the project location.
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Lot 7, West Meadows July 2021
7-2
Drainage Report
On-Site Drainage
Runoff from the developed area was designed to be released at a rate consistent with
historic flows. Runoff from the developed areas, which includes the xeriscape gravel areas,
driveway, and parking area, are conveyed via a series of drainage swales and downspout
piping to onsite landscaped areas for bio retention of total affected impervious area of 3,360
square feet for the 100-year storm event. The detention volume was calculated by finding
the runoff volume of the disturbed area using the rational method and determining volume
was modeled with a FAA spreadsheet for storage volume
A summary of the drainage basin and peak runoff for the 5-year and 100-year design storms
are summarized in the appendix of this report
3.0 Low Impact Site Design
The use of planting and Bio-Retention areas is the proposed method for stormwater
treatment located near the areas of disturbance. A detail of the Bio-Retention cross section
and material is on sheet PRDR1
4.0 Hydrologic Criteria
All hydraulic criteria are derived from the Aspen URMP and URDFCD calculation sheets.
These output data sheets are shown in the appendix of this report.
5.0 Hydraulic Criteria
This project does not contribute any runoff to the existing COA storm system; nor has it any
storm water conveyance structures other than the bio-Retention planting areas described
above.
6.0 Proposed Facilities
The only proposed facilities proposed with this project are described in the low impact
section of this report and will all be contained onsite within the existing drainage and utility
easements.
7.0 Maintenance Plan
All the stormwater mitigation improvements will be owned and maintained by the property
owner and the following maintenance program should be followed to ensure proper functioning
of these proposed improvements. Rain Gardens: Sediment build-up may require periodic
removal of sediments and plants when clogging reduces infiltration capacity to unacceptable
levels. Plant materials in areas prone to sediment build-up should be limited to grass and
groundcovers tolerant of periodic wet-dry cycles.
• Inspect detention area to determine if the sandy grow media is allowing acceptable
infiltration. This should be performed annually.
• Occasional removal of weeds and unwanted vegetation will be required.
• Remove debris and litter from detention area to minimize clogging of filter grow media.
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Provide a summary
of detention
calculations in the
body of the report.
Provide a summary
of the bioretention
areas in the body of
the report.
Provide a detailed
analysis showing
how each
bioretention area was
sized. Show where
all the impervious
area is directed. All of
this should be
provided in the body
of the report.
Describe existing and
proposed subbasins.
Lot 7, West Meadows July 2021
8-3
Drainage Report
• The grow media will clog in time as materials accumulate on it. This layer will need to be
removed and replaced to rehabilitate infiltration rates, along with all turf and other
vegetation growing on the surface. This will be required every 5- 15 years, depending
on infiltration rates needed to drain the WQCV in 12-hours or less.
8.0 Conclusions
As previously stated, the intent of any proposed improvements to the driveway and landscape areas
is to maintain the drainage runoff conditions as are currently operating and to incorporate water quality
storage to offset the proposed improvements. The grass lined swales and planting areas accomplish
this goal with keeping the as-is natural feel of the subject lot.
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Lot 7, West Meadows July 2021
D
Drainage Report
Appendix A
Existing and Proposed improvement drawings
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Include appendices
in the submittal.
Lot 7, West Meadows July 2021
E
Drainage Report
Appendix B
Proposed Basin Calculations
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