HomeMy WebLinkAboutREGISTRY RIDGE, 5TH FILING - PDP - 32-95I - SUBMITTAL DOCUMENTS - ROUND 2 - REVISIONSprovides a better mechanism for removal of particulates from the runoff than would a small on -
site water quality pond. Use of existing swales for water quality will also be visually pleasing
and consistent with the rest of the sub -division. Please reference Appendix D for supporting
photographs of the existing swales and pond areas.
There will be multiple erosion control devices implemented within the site project. Sand bag
check dams will be used in three places along the existing swale to decrease the amount of
sediment accumulation at Design Point A. Straw bale sediment traps shall be installed at both
combination inlets. In addition, silt fencing shall be installed and maintained along the perimeter
of the project site.
In essence, the proposed Design Point A will remain in the same location as the historic Design
Point, ultimately being routed into Pond 603 through the use of existing drainage features. The
proposed runoff coefficients are reduced from the historical design and proper erosion control
and water quality devices shall be installed and maintained.
Please feel free to contact me with any questions you may have regarding this letter.
Respectfully,
4 4 4
Cody N. Snowdon, EI
Reviewed By:
Bud Curtiss, PE
Senior Engineer
•.7
_J
ADDRESS: PHONE:970.221.4158
NORTHERN WEBSITE:
200 S. College Ave. Suite 100
ENGINEERING Fort Collins, CO80524 FAX:410.221.4159 www.northernengineering.00m
May 30`h, 2007
Basil Hamdan
City of Fort Collins
700 Wood Street
Fort Collins, CO 80549
RE: Registry Ridge Fifth Filing
Basil,
This letter is in regards to Registry Ridge Fifth Filing development in Fort Collins, specifically,
the proposed drainage patterns of the project.
The site is a replat of Tract C, Tract H and Tract F of the Corrected Plat of the Final Plat of
Registry Ridge P.U.D., First Filing. The overall area being conveyed is 16.18 acres composed of
historical drainage Basins 403G, 403H, 4031 and 402D of Registry Ridge First Filing. The storm
water is conveyed by a combination of overland, Swale and gutter flow from the northwest
corner of the site to historical Design Point 22 with a further destination of Pond 603. This site
was originally designed and approved in June of 1999 as a combined Regional Park and School
area. The composite runoff for the proposed development is 0.38 for the 2-year storm and 0.48
for the 100-year storm, thus the proposed site will have less imperviousness then originally
anticipated. For specific calculations, see the attached spreadsheet in Appendix A.
The capacity needed for the inlets at historical Design Point 10 and 18 will be decreased due to
7% of historic Basin 402D and 31% of historic Basin 403G being redirected to the proposed site
by form of overland and gutter flow.
Proposed Basin A and off -site Basin OS 1 will convey stormwater by a modified Swale to Design
Point A (historical Design Point 22). The Swale for Basin A and off -site Basin OS1 was
designed to handle a water depth of 1.5 feet before entering the existing lots to the west. At this
depth, the Swale can convey a flow of 43.7 cfs (530% of the 100-year flow). Proposed Basins B
and C will convey runoff by a combination of overland, gutter flow and Swale into two
combination inlets and further to Design Point A. Proposed Basin B will have a system of
swales conveying storm water out to the street. All swales have been designed to capture 150%
of the 100-year flows. For supportive Swale calculations and diagrams, please refer to Appendix
B. Proposed Basin D shall create overland runoff to the southern Swale as previously designed.
All proposed on -site and off -site drainage basins will be collected at Design Point A. Through a
network of established swales, water quality will be achieved through 931 feet of an existing
grassed Swale. The first water quality treatment will occur after exiting the proposed site into a
small pond lined with maintained landscape. The remainder of the water quality shall occur
through an 805' long channel heavily vegetated with high grasses. This established channel