HomeMy WebLinkAboutArchitects Drainage letter.pdf
January 2, 2017
Town of Vail
75 S. Frontage Road
Vail, CO 81657
Re: Sundial Townhomes: Garage Replacement
Martin/Martin, Inc. Project No.: MC15.0036
To Whom It May Concern,
Martin/Martin has completed a review of the existing and proposed drainage patterns for the proposed
Sundial Townhomes Garage Replacement located on the Sundial Phase 2 property and addressed at 5040
Main Gore Place Vail, CO. The property area within the study is 3.63 ac. acres. The project as proposed
consists of replacement of the existing garage facilities and associated site hardscape adjustments. The
purpose of this drainage memorandum is to summarize both the existing and proposed drainage patterns as
well as identify the anticipated drainage modifications that will be necessary to accommodate the proposed
site improvements.
The existing site consists of an asphalt parking, asphalt driveway, various landscaping areas and the existing
garage facilities. The drainage patterns appear to be generally flowing from the south to the north end of
the site, where it discharges to a vegetated swale. The swale is approximately 230 feet in length sloped at
approximately 1.0% to the discharge point into Gore Creek. The proposed site reconstructs and adds to the
existing concrete pan on site and reorients the building locations. Overall the drainage patterns remain the
same in the proposed and existing conditions as shown in the construction documents.
The site imperviousness was calculated for the existing and proposed conditions as detailed in the attached
Site Imperviousness Summary. The existing site has an imperviousness of 59.8% and the proposed site has
an imperviousness of 60.3% an increase of 0.48%. The imperviousness increase is caused by an overall
increase in building size (roof area) of 1622 sf, while landscape and parking/drive area decreased in area by
919 sf and 703 sf respectively. Given the negligible imperviousness increase to the site and reduction in
asphalt dive area, the anticipated increase in pollutant loads is negligible. The swale along the north end of
the site will continue to provide water quality enhancement for the site prior to the ultimate discharge point
at Gore Creek. The proposed improvements on site are not anticipated to negatively impact downstream
properties and drainageways.
Sincerely,
Mark Luna PE
Associate
Attachments: Site Imperviousness Summary
AREA IMPERVIOUSNESS
(SF)(%)
LANDSCAPE 10562 0.0%
ASPHALT 12617 100.0%
ROOF 6027 90.0%
RESIDENTIAL MULTI-UNIT 128961 60.0%
SITE TOTAL 158167 60.3%
AREA IMPERVIOUSNESS
(SF)(%)
LANDSCAPE 11481 0.0%
ASPHALT 13320 100.0%
ROOF 4405 90.0%
RESIDENTIAL MULTI-UNIT 128961 60.0%
SITE TOTAL 158167 59.8%
AREA IMPERVIOUSNESS
(SF)(%)
LANDSCAPE -919 -
ASPHALT -703 -
ROOF 1622 -
SITE TOTAL -0.48%
SITE IMPERVIOUSNESS SUMMARY
PROPOSED SITE
EXISTING SITE
LAND USE
LAND USE
LAND USE
PROPOSED TO EXISTING DIFFERENCE