HomeMy WebLinkAboutSite Certifications - 09/21/2017August 28, 2017
Mr. Wes Lamarque
City of Fort Collins Storm Water Division
700 Wood Street
Fort Collins, CO 80524
(970) 221-6700
Re: Grading Certification for Crowne on Timberline Subdivision, Larimer County Colorado
Dear Mr. Lamarque,
The purpose of this letter is to provide the overall site grading certification for the Crowne on Timberline
Subdivision, located at the site address of 2001 Rosen Drive in Fort Collins, Colorado. The site is bounded by
Prairie Hill Drive to the south, Red Willow Drive to the west, Rosen Drive to the north and Timberline Road to
the east.
Aspen Engineering reviewed the record survey for Pond 100, prepared by King Surveyors, with survey
measurements dated June 28, 2017. Aspen also visited the project site on several dates throughout construction
as the buildings were constructed. Grading certifications were completed for each building and townhome
buildings individually as they were completed. This certification is intended to cover the overall site grading,
drainage and pond certification. Based on the provided record surveys for Pond 100 and the individual building
grading certification surveys and visual observation during site visits, Aspen Engineering asserts that the proposed
grading appears to meet the intent of the approved grading and drainage plan.
Aspen is providing the following as the assessment of the drainage within Crowne on Timberline Subdivision:
1) The storm sewer system record drawings are provided as an attachment with this certification. As
noted on the record drawings, the invert elevations represent the bottom of box (drainage
structure) and not the pipe invert where delineated on the plan. The majority of the pipe slopes
are over the 0.40% minimum slope. Slopes of less than 0.40% occurred on line segments within
Storm B, Storm C, Storm D, and Storm F. However, these are within the construction tolerances
and are not expected to significantly impact the capacity of the storm sewer system.
2) Porous pavers with underdrains were constructed within the parking areas of the site in general
conformance with the approved grading and drainage plans.
Accepted 9/21/2017 WL
12/15 Page 2
Permeable Interlocking Concrete Pavers
Item/Activity Yes No N/A Documentation/Submittal Requirements
Excavation
Post-excavation infiltration rates are consistent with design
infiltration capacity (for “full or partial infiltration” designs)
Impermeable Liner
Impermeable liner meets design specifications
Impermeable liner attached to concrete perimeter wall
Impermeable liner is not exposed
Any penetrations of the impermeable liner have been sealed
and checked for water-tightness.
Concrete Cut-Off Wall
Meets specifications for:
-Dimensions
-Reinforcement
-Footings
Underdrain System
Underdrain pipe is per design specifications
At least one cleanout is provided per underdrain lateral
Cleanout pipe is not perforated
Cleanout covers are installed and watertight
Underdrain is NOT wrapped in geotextile fabric
Underdrain orifice plate installed at outlet structure
Underdrain integrity tested after backfilling using TV and/or
water test
Aggregate
Base coarse (e.g., #2/4) has 90% fractured faces
Bedding coarse (e.g., #89) is thoroughly washed
Sub-base materials are installed and compacted according to
manufacturer’s specifications
Protection During Construction
PICP area is protected from construction site sediment,
including runoff from the upstream catchment and
construction equipment traffic
Close Out
Upstream catchment is stabilized prior to diverting runoff
into PICP system
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12/15 Page 3
Bioretention Cells
Item/Activity Yes No N/A Documentation/Submittal Requirements
Excavation
Heavy equipment did not travel over bioretention cell during
excavation
Bottom of cell was “ripped” after excavation Photograph before/after “ripping”
Bottom of cell is flat and level Photograph
Excavated area is protected/surrounded by sediment/runoff
control BMPs during construction
Photograph
Inlet
Overflow inlet elevation is set above bioretention media per
plan (typically 12 inches)
Overflow inlet invert elevation is at least 3 inches below
containment wall/berm (to direct overflow into inlet)
Measure/record distance between inlet and top of
containment wall/berm
Upstream catchment drains to inlet
Forebay
Forebay is installed according to design specifications
Forebay has flat, concrete bottom
Outlet Structure/Overflow
Outlet structure/overflow elevation is confirmed Measure/record distance from overflow to top of media
filter
Impermeable Liner
Impermeable liner meets design specifications
Impermeable liner attached to concrete perimeter wall
Impermeable liner is not exposed
Underdrain System
Underdrain pipe is per design specifications
At least one cleanout is provided per underdrain lateral
Cleanout pipe is not perforated
Cleanout covers are installed and watertight
Underdrain is NOT wrapped in geotextile fabric
Underdrain orifice plate installed at outlet structure
Underdrain integrity tested after backfilling using TV and/or
water test
12/15 Page 4
Filter Media
Filter media composition is per design specifications
Filter media was “machine mixed” by supplier prior to delivery
Filter media installed flat and level
Other Structural Components
Containment wall/berm is continuous and level
Landscaping
Final landscaping does NOT include sod
Final landscaping (wood/rock mulch) is flat and level
Vegetation is planted according to landscape design
specifications
Verify that weed barrier is not installed
Temporary irrigation installed If N/A, then verify that permanent irrigation is installed to
establish/maintain vegetation
Close Out
Upstream catchment stabilized prior to diverting runoff into
bioretention cell
Signature:
Name:
Title:
Email:
Phone:
Company:
Address:
Matt Otero
Coo
Stonescape@q.com
720-273-4526
Designs By stonescapes
15707 E 109th ave Commerce City
Colorado Co 80022
LEGEND
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