HomeMy WebLinkAboutSite Certifications - 01/06/2015NORTHERN
ENGINEERING
Mr. Wes Lamarque
City of Fort Collins Stormwater Utility
700 Wood St.
Fort Collins, CO
December 7, 2015
RE: Drainage Certification for River District Block One Mixed Use
Dear Mr. Lamarque,
This drainage certification letter is provided to verify as -constructed conditions for River District Block One
Mixed Use. Northern Engineering completed survey work November of 2015 to verify general compliance
with the Final Utility Plans for River District Block One Mixed Use, dated 8/5/13 by Northern Engineering.
Included in this drainage certification submittal are the following:
Attachment 1 - City of Fort Collins Drainage Certification Form.
Attachment 2 - As -constructed pond volume calculations.
Attachment 3 - As -constructed record drawings for Grading and Storm Drain Plan and Profile Sheets.
Based on the calculations shown in Attachment 2, the as -built water quality pond provides the required
design volume of 0.012 acre-feet of storage at an elevation of 4952.45. The original pond design achieved
the required volume at elevation = 4952.30. The as -built pond was constructed to provide the required
water quality volume per the Final Drainage and Erosion Control Report for River District Block One Mixed
Use prepared by Northern Engineering dated August 5, 2013.
We have concluded, based on the attached information and personal site inspection, that the drainage
features for the project site have been constructed in substantial compliance with the above referenced Final
Utility Plans.
Please feel free to contact me with any questions you may have.
Thank you,
NORTHERN ENGINEERING
Frederick S. Wegert, PE
Project Engineer
301 N. Howes Street, Suite 100, Fort Collins, CO 80521 1 970.221.4158 1 www.northernengineering.com
Attachment 1
IN
Fo` rt Collins
COMMERCIAL, MULTI -FAMILY AND SUBDIVISION
CERTIFICATION FORM & CHECKLIST
(Overall Site Drainage)
River District Block One Mixed Use
(Project Name)
12 2 2015
(Date)
(For Commercial or Multi -family, please list any applicable building permit numbers)
Please fill in all applicable items in this Certification Form for Commercial, Multi -Family and Overall Single Family
sites. A copy of the approved grading plan must be submitted with the as -built grading plan. (It is preferred to
have the as -built elevations written in red next to the approved elevations)
Use "OK" for items checked or actual numbers for items verified/surveyed in the field.
Use "N/A" for items that are not applicable to the site that is being certified.
Please provide an As -Built Redlined or Mylar drawing showing the following:
A. Detention, Drainage Facilities, and Common Open Spaces
1. Pond Certification
Provide Topographic Records (grading certification with as —built spot elevations) and Volume
Verification Calculations. Show both the proposed and as -built elevations on the same plan sheet — Ok.
(See attached computations.)
Provide Pond Cross -Sections and Spot Elevations (especially @ Pond Embankment and Pond Flow Line)
— Ok.
— Positive Fall to Pan (if applicable) —Ok.
— General Pond Grading including all Side -Slopes — Ok.
— Invert Elevation —Ok.
— Forebay Construction and Elevation —Ok.
Spillway Weir (Location, Elevation; Height, Opening Width) - N/A. (Concrete weirs not part of design;
all pond weirs graded into pond embankments.)
Placement and size of riprap or alternative permanent erosion control measures — Ok. (To the extent
we were able to visually verify.)
Orifice Plate and/or Water Quality Outlet Structure Installation —Ok. (See attached water quality
outlet structure detail markup.)
12/12/2014 Revision — Page 1 of 6
Fort Collins
Water Quality Capture Volume (Volume Required, Volume Provided and Water Surface Elevation) — Ok.
(See attached computations.)
Berm and Embankment Compaction Level —Unable to verify.
— Subsurface Media for Water Quality Ponds and Swales —Unable to verify.
2. Swales
— Location (are they within easement?) — N/A.
— Dimension and Cross -Section Verification — N/A.
— Longitudinal Slopes and Side -Slopes —N/A.
— Spot Elevations— N/A.
— Permanent Erosion Control Measures (drop structures, riprap, lining) —N/A.
— Tie-in to Storm Lines, Pans, Curbs, or other appurtenances— N/A.
— Required Minimum Freeboard, Provided Freeboard —N/A.
— Landscaping Infringement on Flow Line?— N/A.
3. Piaes — See attached Storm Sewer Plan and Profile Sheets.
— SizeandType—Ok.
— Slopes (As -Built and comparison to 0.4% Minimum) — Ok.
Pipe Capacity Calculations (if slopes are significantly altered from design) — Ok.
— Invert Elevations —Ok.
Installation and Backfill — Unable to verify.
— Cover — Ok.
— Encasement and Clearance from other nearby utility lines —Unable to verify.
— Joints Type and construction —Unable to verify.
4. Concrete Pan Channels
— Size — N/A.
12/12/2014 Revision — Page 2 of 6
— Slope — N/A.
— Cross Section — N/A.
— Thickness — N/A.
— Elevations —_N/A.
5. Inlets
— Size and Type—Ok.
— Size of Opening (or name of Standard Detail used) —Ok.
— Grate Elevation — Ok.
— Invert Elevation —Ok.
— Box Size — Ok.
6. Street Cross -Pans
— Size — Ok.
— Type — Ok.
— Grade—Ok.
— Elevations—Ok.
— Cross -Sectional Depth — Unable to verify.
— Tie-in to Curb and Gutter —Ok.
0
7. Culverts
— Size — N/A.
— Type — N/A.
— Invert Elevations —N/A.
— Headwalls or Wing Walls — N/A.
8. Sub -Drains
Fort Collins
12/12/2014 Revision — Page 3 of 6
Fort Collins
— Size — N/A.
— Type (Perforated/Solid)—N/A.
— Cover — N/A.
— Backfill — N/A.
— Geo-Textile Liners— N/A.
— Clean -Outs —N/A.
9. Curb Cuts
— Size — N/A.
— Tie-in to Swale, Pipe or other appurtenances — N/A.
10. Common Open Spaces
— Overall grading contours of open spaces-Ok.
— Spot elevations adjacent to private lots (property corners) — N/A.
B. Low Impact Development (LID) Certification
1. LID Technique Specific Checklists (see attached)
Permeable Interlocking Concrete Pavers (complete if technique utilized on site) — N/A. Not part of
project.
— Bioretention Cells (complete if technique utilized on site) —See attached.
C. Grading Certification
1. Certification of Grade Elevations —Unable to verify with the current overlot grading.
— Minimum Opening Elevations —Unable to verify with the current overlot grading.
— Top of Foundation Elevations — Unable to verify with the current overlot grading.
— Comparison to 100-year Water Service Elevations —Unable to verify with the current overlot grading.
— Comparison to Freeboard Elevations and Base Floodplain Elevations — BFE —Unable to verify with the
current overlot grading.
2. Verification of Site Grading
12/12/2014 Revision — Page 4 of 6
r
Of
Fort Collins
— Engineer to evaluate site grading compliance with the approved grading plan. -See attached record
drawing grading sheets.
As -built elevations are to be redlined onto the approved grading plan sheet showing the as -built spot
elevations next to the design spot elevations so compliance can be verified and documented. - See
attached record drawings grading sheets.
D. Post -Construction Site Cleanup
1. Permanent BMP Measures
— Construction Debris Clean -Up (In particular debris affecting the drainage) - Ok.
— Smoothing of Ruts in all Construction Areas - Ok.
Reseeding of all Areas Affected by Construction Activities (Usually enforced by the City's Erosion
Control Inspector but the engineer certifying the site needs to notify the contractor if areas are not
seeded) - Contractor notified of areas not seeded.
E. Statement of Compliance
This certification is signed and stamped and by signing this form the Engineer(s) attests that they have
inspected the site and to the best of their knowledge the as -built conditions of the drainage facilities are as
described in the above form and in the As -Built plans enclosed.
Failure to properly disclose all known information could result in the rejection of this certification and
prevent the release of any and all Stormwater Utility permit holds on Building Permits and/or Certificates of
Occupancy within this development.
F. Signature and Stamp by a Colorado Registered Professional Engineer
Engineer's contact information:
Fee de,-:ck k/Ggeet N0r-141C'et En9 -%,nc.0 Z2L
(Name) (Company Name)
fredC na�i�►crnCn�:�►eU:.�,�Gwy 3U1 (�. HowcS Sk:+cloo
(Email address) (Company Address)
(9?e) 5-6E- Co IL®szl
(Telephone number)
0 L /CF �C
scorr�N�^
: LL 45018 � :
�aSS/ONAL
IPE STAMP
12/12/2014 Revision - Page 5 of 6
Fort Collins
}
12/12/2014 Revision — Page 6 of 6
Fo` rt ColUns
Construction Inspection Checklist for Permeable Interlocking Concrete Pavers
Itern/Activity
Yes I
No
I N/A
I Documentation/Submittal Requirements
Excavation
Post -excavation infiltration rates are consistent with
design infiltration capacity (for "full or partial
infiltration" designs)
N/A
Impermeable
Liner
Impermeable liner meets designspecifications
N/A
Impermeable liner attached to concrete perimeter wall
N/A
Impermeable liner is not exposed
N/A
Any Penetrations of the impermeable liner have been
sealed and checked for water -tightness.
N/A
Concrete Cut -Off
Wall
Meets Specifications for:
N/A
- Dimensions
N/A
- Reinforcement
N/A
- Footings
N/A
Underdrain System
Underdrain pipe is per design specifications
N/A
At least one cleanout is provided per underdrain lateral
N/A
Cleanout pipe is not perforated
N/A
Cleanouts covers are installed and watertight
N/A
Underdrain is NOT wrapped in geotextile fabric
N/A
Underdrain orifice plate installed at outlet structure
N/A
Underdrain integrity tested after backfilling using TV
and/or water test
N/A
Aggregate
Base coarse (e.g. #2/4) has 90% fractured faces
N/A
Bedding coarse. e. . #89 is thoroughly washed
N/A
Subbase materials are installed and compacted according
to manufacturerspecifications
N/A
Protection During Construction
12/12/2014 Revision — Page 1 of 2
PICP area is protected from construction site sediment, N/A
including runoff from the upstream catchment and
construction eauinment traffic.
Close Out
Upstream catchment is stabilized prior to diverting runoff N/A
into PICP system
Fo` rt Collins
12/12/2014 Revision — Page 2 of 2
Fort Collins }
Construction Inspection Checklist for Bioretention Cells
Item/Activity
Yes
I No
I N/A
I Documentation/Submittal Requirements
Excavation
Heavy equipment did not travel over bioretention cell
during excavation
N/A
Unable to verify. Did not observe construction
activities.
Bottom of cell was "ripped" after excavation
N/A
Unable to verify. Did not observe construction
activities.
Bottom of cell is flat and level
N/A
Unable to verify. Did not observe construction
activities.
Excavated area is protected/surrounded by
sediment/runoff control BMPs during construction
N/A
Unable to verify. Did not observe construction
activities.
Inlet
Inlet invert elevation is at least 3 inches above.
containment wall/berm
N/A
I
Unable to verify. Did not observe construction
activities.
-Upstream catchment drains to inlet
Yes
Foreba
Forebay is installed according to design s ecifications
N/A
No forebay included within design.
Forebay has flat, concrete bottom
N/A
No forebay included within design.
Outlet Structure/Overflow
Outlet structure/overflow elevation is confirmed
Yes
I
1
1 1.44' from pond bottom to overflow.
Impermeable
Liner
Impermeable liner meets design specifications
N/A
Unable to verify. Did not.observe construction
activities.
Impermeable liner attached to concrete perimeter wall
N/A
Unable to verify. Did not observe construction
activities.
Impermeable liner is not exposed
N/A
Unable to verify. Did not observe construction
activities.
Underdrain System
Underdrain pipe is per design specifications
N/A
Unable to verify. Did not observe construction
activities. -
At least one cleanout is provided per underdrain lateral
N/A
Unable to verify. Did not observe construction
activities.
12/12/2014 Revision — Page I of 2
Fort Collins
Cleanout pipe is not perforated
N/A
Unable to verify. Did not observe construction
activities.
Cleanouts covers are installed and watertight
N/A
Unable to verify. Did not observe construction
activities.
Underdrain is NOT wrapped in geotextile fabric
N/A
Unable to verify. Did not observe construction
activities.
Underdrain orifice plate installed at outlet structure
N/A
Unable to verify. Did not observe construction
activities.
Underdrain integrity tested after backfilling using TV
N/A
Unable to verify. Did not observe construction
and/or water test
activities.
Filter Media
Filter media composition is per design specifications
N/A
Unable to verify. Did not observe construction
activities.
Filter media was "machine mixed" by supplier prior to
N/A
Unable to verify. Did not observe construction
activities.
-delivery
Filter media installed flat and level
N/A
Unable to verify. Did not observe construction
activities.
Other Structural Com onents
Containment wall/berm is continuous and level
N/A
Unable to verify. Did not observe construction
activities.
Landscaping
Final landscaping does NOT include sod
N/A
Unable to verify. Did not observe construction
activities.
Final landscaping (wood/rock mulch) is flat and level
N/A
Unable to verify. Did not observe construction
activities.
Vegetation is planted according to landscape design
N/A
Unable to verify. Did not observe construction
activities.
-specifications
Verify that weed barrier is not installed
N/A
Unable to verify. Did not observe construction
activities.
Temporary irrigation installed
N/A
Unable to verify. Did not observe construction
activities.
Close Out
12/12/2014 Revision — Page 2 of 2
F- rt ColUns
Upstream catchment stabilized prior to diverting runoff
N/A
Unable to verify. Did not observe construction
into bioretention cell
activities.
12/12/2014 Revision — Page 3 of 2
Attachment 2
No Text
NORTHERN
ENGINEERING
Detention Pond Stage Storage Curve
Project Number:
Project Location:
Calculations By:
Pond No.:
685-002
Fort Collins, Colorado
F. Wegert
Detenion Pond
Project: Block One
Date: 12/2/2015
Pond Outlet and Volume Data
Outlet Elevation:
Grate Elevation:
Crest of Pond Elev.:
4951.20
4952.22
4952.82
Design Volume:
Elev at Design Volume:
Elev at Spillway:
0.012 acre ft
4952.45
4952.67
E isting Pond Stage Storage Curve
Contour
Contour
Surface Area
ft'
Depth
Incremental Volume
Cummalitive
Volume
Maximum
Elevation
Minimum
Elevation
sq. ft.
acre ft
sq. ft.
acre ft
4950.8
N/A
0.0
0
0.0
0.000
0.0
0.000
4951.0
4950.8
15.4
0.2
1.5
0.000
1.5
0.000
4951.2
4951.0
41.1
0.2
5.6
0.000
7.2
0.000
4951.4
4951.2
74.0
0.2
11.5
0.000
18.7
0.000
4951.6
4951.4
131.9
0.2
20.6
0.000
39.3
0.001
4951.8
4951.E
311.0
0.2
44.3
0.001
83.6
0.002
4952.0
4951.8
532.31
0.21
84.31
0.002
167.9
0.004
4952.2
4952.0
741.21
0.21
127.31
0.003
295.2
0.007
4952.4
4952.2
944.E
0.2
168.E
0.004
463.8
0.011
4952.6
4952.4
1,200.1
0.2
214.5
0.005
678.3
0.01E
D: I Projects 1685-0021 Drainagel Detention 1
12/2/2015 3:17 PM 685-002 AB Pond Stage Storage.xlsxIPond
Attachment 3