HomeMy WebLinkAboutOLD OAK ESTATES (5227 STRAUSS CABIN RD.) - PDP - 25-07A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT0
LOT IMPERVIOUSNESS
SINGLE FAMILY RESIDENTIAL
(TYPICAL ALL LOTS)
::,.:....,
..
ROOF = 1,806 S.F.
::...........
h.�
PATIO = 299
S.F.
;
DRIVEWAY = 483
S.F.
R.O.W.
WALKS = 75 S.F.
TOTAL = 2,663
S.F. 4 1,2-0 =3Mo %7
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CENTERLINE OF ROAD 'v
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N01ITTH ild SERVICES l ".'« 9811.00 FIGURE 2
420 SOUIN MONTH SUNS ML Fr. COLLINS. COLOR IW SOfY11 ) TYPICAL �tVO M ARMA � LOT (270) 221-41W aw,rwe ,an r�erimnarwi
DEVELOPED COMPOSITE RUNOFF COEFFICIENT CALCULATIONS
Charad.er of Surface
% Impervlou5
Old Oak Estates
By: K. Dail
September 18, 2007
5tructs, Pariking Lots, Roofs, Alleys, and Dnves:
As halt.................................................................................
100%
Concrete..............................................................................
100%
Gravel..................................................................................
40%
Roofs.................................................................................1
90%
Lawns and Landscaping
Sandy5oil................................................................... _.......
0%
Clayey5011............................................................................
0%
I'ei �rnt Imp. i,i i, ��lues m� Cdk n #'om `ahl« 3 of .h� �.,.� DraIi
Type
Area
(s uare feet)
Area of Roofs
(square feet)
Area of Impervious
Surfaces
(square feet)
Area of Gravel
Parking
and Drives
(5cluare feet)
Area of Vegetated
Surfaces
(square feet)
Percent
Impervious
Ifxi5bn6j Lot
5021 I.00
2600.00
600.00
5250.00
41361.00
10.6%
Existin streets and sidewalks
5440.00
0.00
5440.00
0.00
0.00
100.0%
Proposed streets and sidewalks
24213
0.00
15066.50
0.00
62 16.50
74.4%
Proposed Lots
37232.00
10836.00
2244.00
388.00
23600.00
5.0%
Total
217166.00
13636.00
26550.50
I6638.00
173977.50
15.3%
•
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proposed development. Given that the completed project overall basin imperviousness is
15%, the detention and water quality components are already provided with the
McClellan Creek basin and no additional detention or water quality features are required
with this development. Erosion control measures such as silt fence and strawbales will
be in place during construction to help alleviate any potential sources of sediment
pollution to the basin.
In summary, the Old Oak Estates development will follow the historic drainage patterns
of the site with low slopes and heavy vegetation; the site is less impervious than the
assumed value for the site with the McClellan Creek basin creating minimal impact to the
drainage basin. The McClellan Creek basin provides the detention and water quality for
the site.
Please feel free to contact me with any questions you may have regarding this letter.
Sincerely,
Kimberlya/D,ay, PE
NORTHERN ADDRESS: PHONE: 970.221.4158
200 S. College Ave. Suite 100 WEBSITE:
ENGINEERING Fort Collins, CO80524 FAX: 970.221,4159 www.northernengineering.com
September 18, 2007
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: Old Oak Estates
Drainage Letter
This letter is in regards to the Old Oak Estates development in Fort Collins, specifically,
the proposed drainage patterns of the project.
The site is located at Strauss Cabin Road, directly south and adjacent to Sunrise Ridge
Second Filing and is just below five acres in area. A residential home and a barn are
located near the center of the rectangular property, along with a long gravel drive to serve
as access from Strauss Cabin Road. Several trees are on the property; the grasses are lush
and thick, covering most of the site. The existing grades of the lot are very flat; the
average slope is approximately 1 %. The site generally drains west to east; due to the
heavy vegetation and minimal slope, virtually all stormwater infiltrates into the ground.
The existing site imperviousness is less than 3%.
The proposed development of Old Oak Estates will subdivide the property into a total of
six lots; four of the lots will be lh acre in size, the remaining two lots will be 1.15 acres
each. As part of the project, Big Dipper Drive will be extended along the south boundary
of the property from the end of road within Willowbrook Subdivision (Observatory
Village) to Strauss Cabin Road; sidewalks will be constructed along both Big Dipper
Drive and Strauss Cabin Road. For the purposes of analyzing the drainage patterns, a
typical lot is assumed to have 3,196 square feet of impervious area. Please reference the
attached documentation for a breakdown of lot impervious area. The proposed
development with finished construction of houses, drives, roads and walks will raise the
overall site imperviousness from less than 3% to just over 15%. Please reference the
attached documentation for the impervious area calculations. The proposed drainage
patterns of the site will remain as close to existing patterns as possible; it is expected that
the runoff from the site will infiltrate into the ground rather than flow offsite due to the
heavy vegetation and flat slope. Any runoff that would leave the property will be
conveyed east to the roadside ditch along Strauss Cabin Road; the road side ditch is in
good condition with heavy grass vegetation, the culverts are in good condition as well.
The site is located within the East Harmony portion of the McClellan Creek drainage
basin; this basin assumed the pre -development impervious area for this site to be at 20%.
As directed by the City, as long as the additional improvements proposed maintain an
overall impervious area of 20% or less, for the entire subdivided property including half
of the street, then no detention or water quality requirements would need to be met for the