HomeMy WebLinkAboutSite Certifications - 11/20/2020
1218 Ash Street | Suite A
Windsor, CO 80550
970.674.3300
November 11, 2020
Mr. Dan Mogen
City of Fort Collins Stormwater
700 Wood Street
Fort Collins, CO 80521
Re: Living Oaks – Overall Site and Drainage Certification
Dear Dan,
Please accept this letter as the Overall Site and Drainage Certification for the Living Oaks development which is
located at 221 East Oak Street. Survey of the site was completed in October by King Surveyors. A site visit was
conducted by Mike Oberlander on October 27, 2020. Photos of the site visit are attached.
The site work has been completed and is in general conformance with the approved design.
The stamped as-built survey and the as-built drawings of the Storm System and Grading Plans and the Overall Site
Drainage Certification are attached to this letter. Also attached is the During Construction Inspection Checklist that
was completed by the Construction Superintendent.
We appreciate your time and consideration in reviewing this submittal. If you have any questions or comments,
please contact me at (970) 460-8471.
Sincerely,
Michael Oberlander, P.E.
Colorado Professional Engineer 34288
Attachments
OVERALL SITE
AND
DRAINAGE CERTIFICATION
Page 1
OVERALL SITE and DRAINAGE CERTIFICATION
Commercial, Multi-Family and Subdivision Certification Form and Checklist
Project Name:
Date:
Building Permit Numbers:
(Commercial or multi-family)
Per the requirement in Fort Collins Stormwater Criteria Manual (FCSCM) Chapter 3, Section 3.0 to certify as-
built construction to the approved drainage and grading plans, please fill in all applicable items in this
Certification Form for Commercial, Multi-Family and Overall Single Family sites. NOTE: several items must be
verified during construction. A copy of the approved grading plan must be submitted with the as-built grading
plan. (As-built elevations must be written in red next to the approved elevations.)
•Use “Yes” for items completed as described.
•Use “N/A” for items that are not applicable to the site being certified.
•If any blanks are “No,” attach an explanation referencing the item number below.
Attach an explanation or description of the as-built condition for any items listed or for anything not listed but
shown on the approved construction plans.
Provide an as-built redline or Mylar drawing with the following:
I.Water Quality and Quantity Detention Basin - FCSCM Ch. 6 and 7
For multiple detention basins on a site, provide the following for each basin separately:
A. Volume: As-built topographic verification is attached at 1-foot (or less) contour intervals and
volume verification calculations for the water quality capture volume and the 100-year detention storage
volume.
1. Detention basin topography was prepared by a professional land surveyor registered in the state
of Colorado.
2.Both proposed and as-built contours are shown on the same plan sheet (dashed lines for
proposed and solid lines for as-built).
3.All critical spot elevations as shown on the approved construction plans have been verified and
the as-built elevations are shown on the plan sheet.
4.Stage-storage-discharge tables are provided on a separate document.
5.Verification that designed drain time is in compliance with Colorado Revised Statute § 37-92-
602(8) is attached and has been uploaded to the Statewide Compliance Portal
(tinyurl.com/COCompliancePortal) for approval. Uploaded documents must include:
a.The cover sheet from the approved drainage report
b.The stamped certification page from the approved drainage report
c.As-built topographic survey
d.Stamped certification page from the Overall Site & Drainage Certification
e.PDF output from the Stormwater Detention and Infiltration Design Data Speadsheet
11/19
Living Oaks
11-16-20
B1704008
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Page 2
B.Water Quality and Quantity Detention Basin Grading: Attached is as-built verification that there is
a minimum 2% positive fall into the concrete trickle pans or flow-line(s) from all areas in the bottom of
the detention pond. If there is a “soft pan” in the flow-line, all areas still must meet the minimum 2%
grade requirement.
1.Low Flow: Choose one of the following detention basin low flow options as applicable:
a. Turf swale for low flow path in detention basin.
There is a minimum 2% grade in the flow-line(s) of the detention basin. The flattest as-built grade
is .
b.Concrete pan for low flow in detention basin.
There is a concrete pan installed that meets the grades as shown on the approved construction
plans. (Show as-built spot elevations.)
c.Soft pan for low flow in detention basin.
•Verify and document the soft pan material gradation, trench width and depth - to be verified
during construction by engineer. Picture documentation is preferred or engineer’s statement of
visual inspection and compliance. (Choose one below.)
o There is a soft pan with an underdrain installed that meets the design on the approved
construction plans. (Show the underdrain grades, bedding material, geotextile, spot elevations,
bends, cleanouts, etc.)
o There is soft pan installed without an underdrain but there is a type A or B soil. The soil
type must be documented by supplying verification from a registered professional geotechnical
engineer.
NOTE: Spot elevations are to be within 0.2 ft. +/-.
2. Side Slopes: The as-built side slopes of the detention basin have been calculated and are shown.
Indicate the side slope with an arrow and a numerical value (e.g., 6.25:1). The maximum slope allowed
is 4:1. Small areas of 3:1 may be acceptable, but slopes steeper than 3:1 must be stabilized or re-
graded. Provide documentation if a variance was granted for steeper slopes during the design process.
3.Spillway: The following items must be field verified:
a.The location of the spillway is indicated on the as-built plan.
b.The width of the spillway is indicated on the as-built plan.
c.The elevation(s) of the spillway is shown on the as-built plan.
d.A concrete ribbon defines the location and grade of the spillway.
e.There is downstream scour protection in the spillway as per the construction plans. Indicate
type: (riprap size “D50” gradation and bedding type, geotextile, buried
riprap with inches of bury, etc.).
f.There are no obstructions in the spillway, such as trees, bushes, sidewalks, landscape
features, rocks, etc.
11/19
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Page 3
4.Outlet Structure:
a.The orifice plate for the approved release rate is installed with the correct size and location of
the orifice.
b.The orifice plate for the water quality outlet is installed with the correct hole size, number of
rows and columns of holes.
c.The bottom hole on both the water quality and quantity outlets are at the bottom of the plate
so no water ponds in front of the plate.
d.The well screen is the correct material and is installed as shown on the construction plans.
e.100-year overflow grate elevation is . (Elev. A on detail D-46)
f.The top elevation of the water quality capture volume is . (Elev. B on detail
D-46)
g.Overflow grate is made of the correct material, has the correct bar spacing, is hinged at the
top and bolted at the bottom.
h.The bottom of the outlet box has no obstructions or misalignments that will cause it to retain
runoff water and is sloped at 2% towards outlet.
II.Channels/Swales - FCSCM Ch. 8, Sec. 2.0 and Ch. 9, Sec. 5.0
A. Capacity: The as-built capacity of all the major channels and swales has been verified. They meet
or exceed capacity requirements shown in the approved drainage study for this project.
1.All swales are located within the drainage easements as shown on the construction plans.
2.Longitudinal slopes and side-slopes (cross-sections) have been verified. Design criteria requires
longitudinal slopes of 2% min. (on vegetated swales) and side-slopes no steeper than 4:1. If these
criteria are not met, the certification engineer will write a justification and propose mitigation for each
instance or have the issues corrected. If variances to these criteria have previously been approved and
are shown on the construction plans, no justification is needed.
3.As-built spot elevations on channels/swales are shown that correspond to spot elevations
shown on the approved construction plans.
4.All permanent erosion control measures are installed as shown on the approved construction
plans (e.g., drop structures, riprap, TRMs, etc.). (Include pictures and verification of the materials used
as part of this verification.)
5.All pans, curbs, storm pipes or other appurtenances appropriately tie into each other in the
system. (Pictures at tie-in points suggested.)
6.The minimum freeboard is provided for all channels and swales as shown on the approved
construction plans or as identified in the approved drainage study. (Show the freeboard provided on
the cross-sections as on the construction plan set or attached as separate documentation.)
7.The low flow portion of all channels or swales is clear of obstructions. (No landscaping, trees,
shrubs, sod, etc. infringe on the low flow portion of channels or swales.)
11/19
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Page 4
III.Storm Pipes (aka storm drains) - FCSCM Ch. 9, Sec. 4.0
A. Storm Drain Pipe Capacity: The as-built capacity of all pipes installed on this project has been
verified and meets or exceeds the capacity requirements shown in the approved drainage study for this
project.
1.All storm drain pipe sizes and materials have been verified and are in conformance with the
approved construction plans. (Indicate on the plan and profile sheets that they have been verified.)
Material and size substitutions must be approved prior to installation. If a pipe size or material was
changed during construction, the certification engineer must attach the approval documents or supply
them with this certification. Approval documents must include a calculation documenting the capacity
equivalency (equal or greater) of the substituted size.
2.The longitudinal slope of the pipe is as shown on the approved construction plans. The
acceptable minimum slope is 0.4%. All slopes flatter than the designed slope on the construction plans
must be justified with capacity calculations on an attached sheet.
3.The as-built invert elevations have been verified and are shown on the plan and profile sheets of
the approved construction plans.
B.Storm Drain Pipe Installation Requirements: All pipes are installed in accordance with the
approved construction plans and construction specifications.
1.The minimum cover requirements for all pipes have been met as shown on the approved
construction plans. These will be called out in critical locations.
2.All encasements and clearances as specified on the approved construction plans have been met.
3.Any specific joint types or construction methods specified on the approved construction plans
have been met. (List on a separate sheet and attach to this certification.)
IV.Concrete Pans - FCSCM Ch. 8, Sec. 2.0
A. Construction/Installation: All concrete pans have been constructed in accordance with the
approved construction plans.
1.The concrete pans are the correct size/width as shown on the approved construction plans.
2.The longitudinal slopes of the pans are as shown on the approved construction plans. The
certification engineer must justify or mitigate longitudinal slopes less than the minimum of 0.4% unless
a flatter slope was approved and is shown on the approved construction plans. Provide mitigation or
justification by separate document.
3.The cross-section of the pan is as shown on the construction plans. (Specifically, the pan cross-
section is “V” shaped and meets the side slope shown on the detail.)
4.The concrete pans are a minimum of 6 inches thick without reinforcement and a minimum of 4
inches thick with a minimum of 6X6-W14xW14 reinforcement per detail D20B and D20C. (Provide
documentation of the reinforcement used if different than shown on the details or on the approved
construction plans.)
5.The spot elevations shown on the concrete pan(s) have been verified and are shown on the as-
built drawings.
11/19
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Everything designed to sheet flow if the pipes are overwhelmed.
Page 5
V. Storm Drain Inlets - FCSCM Ch. 9, Sec. 3.0
A. Construction/Installation: All storm drain inlets have been constructed in accordance with the
approved construction plans and construction specifications.
1.The size and type of inlets are consistent with the inlets shown on the approved construction
plan. Indicate by writing “Verified” on each inlet on the plan sheet or list on a separate document the
inlet number(s), type and size (length). If the inlet installed is other than the one on the approved
construction plan detail sheet, provide the name and source of the detail with justification for equal or
better capacity.
2.The size of the inlet opening is consistent with the approved detail. (Check height and width.)
3.The elevation of the grate (if applicable) is at the elevation shown on the street profile or as
indicated by a spot elevation on the construction plans.
4.The as-built invert elevations of all pipes entering and leaving the inlet are shown on the plan
and profile sheets within construction tolerance of 0.2 feet. If substantially different, provide
justification and capacity calculations to show the capacity is not affected or propose mitigation.
5.The as-built size of the inlet box is as shown on the construction plans or an explanation or
justification is attached.
6.All Type C, R, 13 and 16 inlet covers are stenciled or stamped with the following designation (or
an equivalent): NO DUMPING – DRAINS TO POUDRE RIVER.
VI.Culverts - FCSCM Ch. 9, Sec. 4.0
A. Construction/Installation: All culverts have been constructed and/or installed in accordance with
the approved construction plans and construction specifications.
1.All culvert sizes have been verified as indicated on the as-built construction plans as correct.
2.The culvert material type for all culverts installed is as on the approved construction plans and is
indicated on the as-built plans.
3.The as-built invert “in and out” elevations have been verified and are indicated on the as-built
construction plans.
4.The culvert headwalls or wing walls have been installed as shown on the approved construction
plans. Headwalls or wing walls may be needed in the as-built conditions onsite if the slopes adjacent to
the culvert are greater than 4:1. Please note areas needing stabilization in the certification narrative.
An alternative to consider is a turf reinforcement mat (TRM).
VII.Sub-Drains
A. Construction/Installation: All sub-drains shown on the construction plans have been installed in
accordance with those plans and the construction specifications. Sub-drains installed with the sanitary
sewer are to be verified on the sanitary sewer plan and profile sheets of the construction plans. (NOTE:
Indicate any sub-drains installed after the plans were approved on the as-built plans.)
1.The size of the sub-drains are as approved on the construction plans and are indicated on the as-
built plans.
2.The type of sub-drain, in particular the perforated and non-perforated sections of the drain, are
as indicated on the approved construction plans.
11/19
Yes
Yes
Yes
Yes
Yes
Yes
N/A
N/A
N/A
N/A
N/A
N/A
Yes
Yes
Yes
N/A
Page 6
3.The cover requirements per the construction plans are provided.
4.The cleanouts have been installed at the locations shown on the construction plans and are
accessible for cleaning. (Cleanouts can be buried a maximum of 6 inches deep with their locations
marked.)
5.The backfill materials for sub-drains are as shown on the approved construction plans. (This
includes the type, depth and width.)
6.The geo-textile liner completely wraps the sub-drain and the permeable backfill material unless
shown otherwise on the approved construction plans. (Sub-drain pipe wrapped in a sock filter material
is accepted only if approved prior to installation.)
VIII.Curb Cuts
A. Construction: All curb cut openings are constructed in accordance with the approved construction
plans and construction specifications.
1.The size (width) of the curb cut opening is as shown on the approved construction plans.
2.The curb cut openings tie into a downstream swale, pipe, or other appurtenances with a smooth
transition and there no obstructions such as riprap or sod impeding the flow downstream of the curb
cut.
IX.Sidewalk Culverts & Chases
A. Construction/Installation: All sidewalk culverts have been installed at the locations shown on the
approved construction plans.
1.The size (width and length) of the culverts are as shown on the approved construction plans.
2.The cover plate is a minimum 5/8-inch galvanized plate bolted to a galvanized angle iron per the
detail shown on the approved construction plans or per the City’s detail.
3.The sidewalk culvert invert “in and out” elevations have been verified and are indicated on the
as-built plans.
4.The sidewalk culvert opening is as shown on the approved construction plans or per the City’s
detail.
5.There is a smooth transition both on the inlet and outlet ends of the sidewalk culvert with no
obstructions such as riprap or sod impeding the flow into or out of the sidewalk culvert.
X. Site Grading - FCSCM Ch. 8
A. Construction: All common open spaces have been graded in accordance with the approved
construction plans.
1.The grading on all common open spaces bordering private lots has been verified as correct and
the as-built rear lot corner elevations have been shown on the as-built plans.
11/19
Yes
Yes
Yes
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Yes
Yes
N/A
N/A
Page 7
2.The as-built contours for “overlot grading” are shown on the as-built construction plans for all
common open spaces, tracts, outlots, etc. If not in compliance, please attach a narrative describing the
situation for noncompliance and when it may be corrected. An escrow for overlot grading may be
required. (NOTE: Residential Lot Grading Certification is a separate process from this Overall Site
Certification. It is understood that residential lots will be brought to final grade once the foundation is
backfilled so they may be lower than the plan shows at this Overall Site Certification stage.)
3.All turf reinforcement mats (TRMs) have been installed as shown on the approved construction
plans and the slopes are stabilized.
XI.Permanent Erosion Control BMPs - FCSCM Ch. 9, Sec. 7.0
A. Construction: All permanent erosion control BMPs have been installed per the approved
construction plans.
1.All riprap has been installed in the locations and sizes indicated on the approved construction
plans.
2.All fabric has been installed in the locations and sizes indicated on the approved construction
plans.
a.All fabric was installed per the details on the approved construction plans.
XII.Post-Construction Site Cleanup - FCSCM Ch. 3, Sec. 2.0
A. Construction: All construction debris and obstructions of any kind have been removed from
drainage paths.
1.All construction debris has been removed except in staging area(s).
2.All ruts have been smoothed out in all construction areas.
3.All areas needing reseeding have been identified and future stabilization goals have been
coordinated with the Erosion Control Inspector and in accordance with FCSCM Vol.2 Chapter 12. Note
the area needing stabilization in the narrative.
XIII.Certification of LID and Water Quality Facilities - FCSCM Ch. 7
A.Attached are the During Construction Inspection Checklist for Low Impact Development (LID) and
other items to be verified during construction, along with pictures and other required documentation.
B.Attached is verification of the rain garden and/or sand filter flat surface area(s) and ponding
volume(s). This verification includes survey of critical elevations.
C.Attached is verification of the underground infiltration required volume(s), weir elevations,
orifices, inspection ports and filtering fabric. This verification includes survey of critical elevations.
D.All visible LID design features were verified as part of the engineer's site visit.
11/19
No
N/A
Yes
N/A
N/A
N/A
Yes
Yes
Yes
Yes
Yes
N/A
N/A
Yes
Only spot elevations are shown on the grading plan.
DURING CONSTRUCTION INSPECTION CHECKLIST
AND SUPPORTING DOCUMENTATION
Jesse Schlam
completed regular
inspections
Load ticket info provided by Ewing
Irrigation and Landscape Supply
STAMPED SURVEY
AND
RECORD DRAWINGS
SITE VISIT PHOTOS
2/14/17 Page 1
CERTIFICATION OF LOT GRADING
Pursuant to Fort Collins City Code § 26-544 & City Land Use Code § 3.3.2 (e)
Date:
Address:
Lot: Block:
Subdivision:
Permit Application #:
Larimer County Parcel #:
Larimer County Reception #:
(on development agreement)
I, (print) , a Colorado registered professional engineer, verify that construction
of all stormwater facilities and grading is complete and hereby submit this certification.
Please answer the following questions by initialing the appropriate response. For each question initialed “No,” attach an
explanation detailing how this will affect stormwater drainage for this lot and any adjacent lots.
1.Certification includes attached Stormwater-approved grading plan. (NOTE: City’s
Building Department does not approve grading plans).
2.Certification includes the attached as-built survey dated (must be within 60
days of the date the certification is submitted) accurately and truthfully depicting
elevations for:
Top of foundation/finished floor
Finished grade on each side of the structure
Quarter points along each lot line (not more than 50 feet apart)
Break points/high points
Swales
Berms
Retaining walls
Air conditioning pads
Window wells
Any other appurtenance(s) within an easement
3.All elevations are within a 0.2 foot tolerance of the approved grading plan.
4.The top of foundation is at least 6 inches above the highest grade surrounding the
structure.
5.There is a minimum grade of 5% away from the structure within the first 5 to 10 feet
adjacent to the residence.
6.All slopes meet or exceed the minimum requirement of 2% (1% is acceptable on single
family lots when the swale is draining the runoff from only two adjoining properties)
and are not steeper than 33% (3:1).
7.All flow lines of stormwater drainage swales are a minimum of 6 inches below the
elevation of ground adjacent to the structure and will direct drainage as shown on the
Stormwater-approved grading plan.
8.All downspout locations and discharge directions are shown on the as-built survey.
Runoff is directed into an appropriate drainage system or lot line swale, and it is not
directed onto neighboring properties.
No Yes
No Yes
No Yes
No Yes
No Yes
No Yes
No Yes
No Yes
11-16-2020 Town of Fort Collins
221 E. Oak Street B1704008
Fort Collins, CO 80524 9712320020
E 92.16 FT of Lot 8 132 20180006949
Michael Oberlander
10/28/2020
MPO
MPO
MPO
MPO
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MPO
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MPO
1218 Ash Street | Suite A
Windsor, CO 80550
970.674.3300
November 11, 2020
Mr. Dan Mogen
City of Fort Collins Stormwater
700 Wood Street
Fort Collins, CO 80521
Re: Living Oaks – Certification of Lot Grading
Dear Dan,
Interwest Consulting Group was the design engineer for the Living Oaks development which is located at 221 East
Oak Street. The design consists of a new building and drive aisle/hardscape area behind and tucked under the upper
floors of the building.
Please accept this letter and attachments as the Certification of the Living Oaks development. The elevations are in
general conformance with the elevations shown on the City approved Grading Plan. The Certificate of Lot Grading
form is attached. The following items are checked “no” on the form and require additional explanation:
3. All elevations are within a 0.2 foot tolerance of the approved grading plan – There are some as built elevations
that exceed the 0.2 foot tolerance but the original intent for the drainage is in general conformance of the approved
grading plan.
4. The top of foundation is at least 6 inches above the highest grade surrounding the structure - Positive drainage
is achieved away from the structure.
5. There is a minimum grade of 5% away from the structure within the first 5 to 10 feet adjacent to the residence
- Positive drainage is achieved away from the structure.
6. All slopes meet or exceed the minimum requirement of 2% (1% is acceptable on single family lots when the
swale is draining the runoff from only two adjoining properties) and are not steeper than 33% (3:1) – Not
applicable to this development. The site slopes are per the approved design.
2
7. All flow lines of stormwater drainage swales are a minimum of 6 inches below the elevation of ground adjacent
to the structure and will direct drainage as shown on the Stormwater-approved grading plan – Not applicable to
this development. There are no drainage swales on site.
This letter is intended to supplement the Certification of Lot Grading and supports our belief that the grading for the
referenced project provides positive drainage away from structure. Therefore, we request that the lot listed above
be deemed acceptable to the City of Fort Collins.
We appreciate your time and consideration in reviewing this submittal. If you have any questions or comments,
please contact me at (970) 460-8471.
Sincerely,
Michael Oberlander, P.E.
Colorado Professional Engineer 34288
Attachments