HomeMy WebLinkAboutDrainage Reports - 06/25/2020City of Fort Collins Approved Plans
Approved by:
Date:
Dan Mogen
06/25/2020
Existing
Conditions
Proposed
Conditions
PROJECT INFORMATION
PROJECT NAME:
PROJECT NO:
DESIGN BY:
REVIEWED BY:
JURISDICTION:
REPORT TYPE:
DATE:
C2 C5 C10 C100 % IMPERV
0.95 0.95 0.95 1.19 95%
0.95 0.95 0.95 1.19 95%
0.80 0.80 0.80 1.00 80%
0.50 0.50 0.50 0.63 50%
13.59 0.69 0.69 0.69 0.83 69.4%
AREA
(ACRES) C2 C5 C10 C100
0.57 0.95 0.95 0.95 1.19 95%
0.91 0.25 0.25 0.25 0.31 25%
1.48 0.52 0.52 0.52 0.65 52.0%
AREA
(ACRES) C2 C5 C10 C100
0.37 0.95 0.95 0.95 1.19 95%
0.41 0.95 0.95 0.95 1.19 95%
0.31 0.25 0.25 0.25 0.31 25%
1.09 0.75 0.75 0.75 0.94 75.1%
AREA
(ACRES) C2 C5 C10 C100
0.13 0.95 0.95 0.95 1.19 95%
0.17 0.95 0.95 0.95 1.19 95%
0.24 0.20 0.20 0.20 0.25 20%
0.54 0.62 0.62 0.62 0.77 61.7%
AREA
(ACRES) C2 C5 C10 C100
0.14 0.20 0.20 0.20 0.25 20%
0.22 0.95 0.95 0.95 1.19 95%
0.21 0.95 0.95 0.95 1.19 95%
0.57 0.77 0.77 0.77 0.96 76.6%
AREA
(ACRES) C2 C5 C10 C100
0.47 0.95 0.95 0.95 1.19 95%
0.17 0.20 0.20 0.20 0.25 20%
0.64 0.75 0.75 0.75 0.94 75.1%
AREA
(ACRES) C2 C5 C10 C100
0.32 0.95 0.95 0.95 1.19 95%
0.04 0.95 0.95 0.95 1.19 95%
0.17 0.25 0.25 0.25 0.31 25%
0.53 0.73 0.73 0.73 0.91 72.5%
AREA
(ACRES) C2 C5 C10 C100
Larimer County Jail Expansion
19.0222
KNF
JER
RECYCLED ASPHALT
1
ASPHALT/CONCRETE
GRAVEL
TOTAL SITE COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
Fort Collins
Drainage Report
02/04/20
JURISDICTIONAL STANDARD
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
ASPHALT/CONCRETE
ROOF
LANDSCAPE, CLAYEY, 2-7%
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
2
ROOF
ASPHALT/CONCRETE
LANDSCAPE, CLAYEY, 2-7%
3
ROOF
ASPHALT/CONCRETE
LANDSCAPE, CLAYEY, <2%
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
4
LANDSCAPE, CLAYEY, <2%
ASPHALT/CONCRETE
ROOF
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
5
ASPHALT/CONCRETE
LANDSCAPE, CLAYEY, <2%
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
6
ROOF
ASPHALT/CONCRETE
LANDSCAPE, CLAYEY, 2-7%
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
5/7/2020 6:55 PM
COMPOSITE_C-VALUES
G:\Thornbrough\19.0222-Larimer County Jail Expansion\ENG\DRAINAGE\Proposed Rational for Site Storm Infrastructure (Non-UDFCD).xlsm
0.33 0.95 0.95 0.95 1.19 95%
0.33 0.95 0.95 0.95 1.00 95.0%
AREA
(ACRES) C2 C5 C10 C100
0.08 0.95 0.95 0.95 1.19 95%
0.08 0.95 0.95 0.95 1.00 95.0%
AREA
(ACRES) C2 C5 C10 C100
0.15 0.95 0.95 0.95 1.19 95%
0.15 0.95 0.95 0.95 1.00 95.0%
AREA
(ACRES) C2 C5 C10 C100
0.15 0.95 0.95 0.95 1.19 95%
0.15 0.95 0.95 0.95 1.00 95.0%
AREA
(ACRES) C2 C5 C10 C100
0.24 0.95 0.95 0.95 1.19 95%
0.24 0.95 0.95 0.95 1.00 95.0%
AREA
(ACRES) C2 C5 C10 C100
0.24 0.95 0.95 0.95 1.19 95%
0.24 0.95 0.95 0.95 1.00 95.0%
AREA
(ACRES) C2 C5 C10 C100
0.06 0.95 0.95 0.95 1.19 95%
0.06 0.95 0.95 0.95 1.00 95.0%
AREA
(ACRES) C2 C5 C10 C100
0.42 0.95 0.95 0.95 1.19 95%
0.05 0.25 0.25 0.25 0.31 25%
0.47 0.88 0.88 0.88 1.00 87.6%
AREA
(ACRES) C2 C5 C10 C100
0.38 0.80 0.80 0.80 1.00 80%
0.19 0.95 0.95 0.95 1.19 95%
0.01 0.95 0.95 0.95 1.19 95%
1.01 0.25 0.25 0.25 0.31 25%
1.59 0.47 0.47 0.47 0.59 46.9%
15
RECYCLED ASPHALT
ASPHALT/CONCRETE
ROOF
LANDSCAPE, CLAYEY, 2-7%
SUB-BASIN COMPOSITE
7
ROOF
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
8
ROOF
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
9
ROOF
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
10
ROOF
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
PERCENT
IMPERVIOUSNESS
12
ROOF
SUB-BASIN COMPOSITE
11
ROOF
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
13
ROOF
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
14
ASPHALT/CONCRETE
LANDSCAPE, CLAYEY, 2-7%
PERCENT
IMPERVIOUSNESS
5/7/2020 6:55 PM
COMPOSITE_C-VALUES
G:\Thornbrough\19.0222-Larimer County Jail Expansion\ENG\DRAINAGE\Proposed Rational for Site Storm Infrastructure (Non-UDFCD).xlsm
AREA
(ACRES) C2 C5 C10 C100
0.59 0.25 0.25 0.25 0.31 25%
0.59 0.25 0.25 0.25 0.31 25.0%
AREA
(ACRES) C2 C5 C10 C100
0.12 0.25 0.25 0.25 0.31 25%
1.03 0.95 0.95 0.95 1.19 95%
0.04 0.20 0.20 0.20 0.25 20%
1.19 0.85 0.85 0.85 1.00 85.4%
AREA
(ACRES) C2 C5 C10 C100
0.40 0.20 0.20 0.20 0.25 20%
2.14 0.95 0.95 0.95 1.19 95%
2.54 0.83 0.83 0.83 1.00 83.2%
AREA
(ACRES) C2 C5 C10 C100
0.42 0.95 0.95 0.95 1.19 95%
0.05 0.50 0.50 0.50 0.63 50%
0.64 0.25 0.25 0.25 0.31 25%
1.11 0.53 0.53 0.53 0.66 52.6%
13.59 0.69 0.69 0.69 0.83 69.4%
TOTAL SITE COMPOSITE
PERCENT
IMPERVIOUSNESS
PERCENT
IMPERVIOUSNESS
19
ASPHALT/CONCRETE
GRAVEL
LANDSCAPE, CLAYEY, 2-7%
SUB-BASIN COMPOSITE
18
LANDSCAPE, CLAYEY, <2%
ASPHALT/CONCRETE
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS
17
LANDSCAPE, CLAYEY, 2-7%
ASPHALT/CONCRETE
LANDSCAPE, CLAYEY, <2%
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS
PERCENT
IMPERVIOUSNESS
16
LANDSCAPE, CLAYEY, 2-7%
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS
5/7/2020 6:55 PM
COMPOSITE_C-VALUES
G:\Thornbrough\19.0222-Larimer County Jail Expansion\ENG\DRAINAGE\Proposed Rational for Site Storm Infrastructure (Non-UDFCD).xlsm
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PROJECT:
JOB NO:01/19/00
DATE:02/04/20
DESIGN AREA %
Q2 Q100
POINT (ACRES) IMP. (CFS) (CFS)
1 1 1.48 52.0% 0.52 0.65 1.30 5.66
2 2 1.09 75.1% 0.75 0.94 1.55 6.79
3 3 0.54 61.7% 0.62 0.77 0.61 2.64
4 4 0.57 76.6% 0.77 0.96 1.21 5.28
5 5 0.64 75.1% 0.75 0.94 1.34 5.84
6 6 0.53 72.5% 0.73 0.91 0.89 3.85
7 7 0.33 95.0% 0.95 1.00 0.87 3.20
8 8 0.08 95.0% 0.95 1.00 0.21 0.78
9 9 0.15 95.0% 0.95 1.00 0.40 1.46
10 10 0.15 95.0% 0.95 1.00 0.40 1.46
11 11 0.24 95.0% 0.95 1.00 0.63 2.33
12 12 0.24 95.0% 0.95 1.00 0.63 2.33
13 13 0.06 95.0% 0.95 1.00 0.16 0.58
14 14 0.47 87.6% 0.88 1.00 1.15 4.56
15 15 1.59 46.9% 0.47 0.59 1.23 5.38
16 16 0.59 25.0% 0.25 0.31 0.30 1.29
17 17 1.19 85.4% 0.85 1.00 2.53 10.40
18 18 2.54 83.2% 0.83 1.00 5.21 21.88
19 19 1.11 52.6% 0.53 0.66 0.99 4.32
13.59 69.4% 0.69 0.83 21.61 90.01
Larimer County Jail Expansion
SITE COMPOSITE
BASIN
RUNOFF SUMMARY
C2 C100
RUNOFF_SUMMARY
5/7/2020 6:58 PM
G:\Thornbrough\19.0222-Larimer County Jail Expansion\ENG\DRAINAGE\Proposed Rational for Site Storm Infrastructure (Non-
UDFCD).xlsm
Capacity (cfs)
Capacity (cfs)
Bioretention T-3
November 2010 Urban Drainage and Flood Control District B-13
Urban Storm Drainage Criteria Manual Volume 3
Table B-6. Native Seed Mix for Rain Gardens
2
1 Wildflower seed (optional) for a more diverse and natural look.
2 PLS = Pure Live Seed.
Common Name Scientific Name Variety PLS
2
lbs per
Acre
Ounces
per
Acre
Sand bluestem Andropogon hallii Garden 3.5
Sideoats grama Bouteloua curtipendula Butte 3
Prairie sandreed Calamovilfa longifolia Goshen 3
Indian ricegrass Oryzopsis hymenoides Paloma 3
Switchgrass Panicum virgatum Blackwell 4
Western wheatgrass Pascopyrum smithii Ariba 3
Little bluestem Schizachyrium scoparium Patura 3
Alkali sacaton Sporobolus airoides 3
Sand dropseed Sporobolus cryptandrus 3
Pasture sage1 Artemisia frigida 2
Blue aster1 Aster laevis 4
Blanket flower1 Gaillardia aristata 8
Prairie coneflower1 Ratibida columnifera 4
Purple prairieclover1 Dalea (Petalostemum) purpurea 4
Sub-Totals: 27.5 22
Total lbs per acre: 28.9
APPENDIX K
City of Fort Collins Standard Operating Procedures
STANDARD OPERATING PROCEDURES (SOPs)
A. Purpose
In order for physical stormwater Best Management Practices (BMPs) to be effective, proper
maintenance is essential. Maintenance includes both routinely scheduled activities, as well as non-
routine repairs that may be required after large storms, or as a result of other unforeseen
problems. Standard Operating Procedures (SOPs) clearly identify BMP maintenance responsibility.
BMP maintenance is the responsibility of the entity owning the BMP.
Identifying who is responsible for maintenance of BMPs and ensuring that an adequate budget is
allocated for maintenance is critical to the long-term success of BMPs. For this project, the
privately owned BMPs shown in Section B below are to be maintained by the property owner or
property manager.
B. Site-Specific SOPs
The following stormwater facilities contained within this development are subject to SOP
requirements:
- Directly Connected Downspouts
- Perforated Subdrain
- Storm Drain Lines
- Dry Extended Detention
- Pre-Sedimentation Forebay
- Bioretention
- Vegetated and/or Cobble Swale
The location of said facilities can be found on the Larimer County Jail Utility Plans and Landscape
Plans. Required inspection and specific maintenance procedures and frequencies are outlined in
the following pages. General maintenance requirements and activities, as well as BMP-specific
constraints and considerations shall follow the guidelines outlined in Volume 3 of the Urban
Drainage and Flood Control District (UDFCD) Urban Storm Drainage Criteria Manual.
SOP Maintenance Summary Table
Stormwater Facility /
BMP
Ownership /
Responsibility UDFCD Maintenance Reference
Directly Connected
Downspouts Private
Perforated Subdrain Private
Storm Drain Lines Private Follow guidelines for
Dry Extended
Detention Private Follow guidelines for
Pre-Sedimentation
Forebay Private Follow guidelines for
Bioretention Private Follow guidelines for
Vegetated and/or
Cobble Swale Private
Follow guidelines for
. Take note of native
vegetation. Also follow recommendations on
Landscape Plans and Specifications.
Directly Connected Downspouts
Many of the downspouts connect directly to the storm drain system. The following SOP generally applies
to all direct downspout connections.
This SOP can more specifically apply to those which drain directly to the reservoir areas beneath the
Modular Block Pavers. At each of these connections, the downspout discharges to a perforated drain
basin. The drain basins discharge directly to the MBP reservoir. The drain basins are designed to prevent
debris and sediment from entering the MBP reservoir area. Debris and sediment compromise the
functionality and effectiveness of the system.
Routine Maintenance Table for Directly Connected Downspouts
Required
Action Maintenance Objective Frequency of Action
Inspections
Inspect the downspout and basin to
ensure the system functions as it
was designed. Repair or replace
damaged downspouts as needed.
Routine
Sediment,
Debris and Litter
removal
Remove debris and litter from the
basin. Remove sediment from the
sump.
Routine – just before annual storm seasons
(i.e., April/May); at the end of storm season
after leaves have fallen; and following
significant rainfall events.
Perforated Subdrain
The perforated subdrain system storm drain outfall at the bottom of the Low Impact Development (LID)
system is critical to the overall function of the system subbase. As such, special maintenance has been
identified to ensure these perforated drain systems perform as they were designed.
Perforated subdrains leading away from the LID system is designed to provide faster release of water
when accumulation occurs under the LID system. Outflow should be seen into downstream storm boxes. If
not seen it is recommended that the system is inspected using a video camera to verify no clogging has
occurred.
Perforated subdrains leading toward the LID system are designed to provide an opportunity for
infiltration. These subdrains may lead to a drywell where additional infiltration capacity is available to
reduce runoff per the stated LID goals adopted by the City.
Routine Maintenance Table
Required
Action Maintenance Objective Frequency of Action
Inspection
Use a video camera to inspect the
condition of the perforated drain
pipes. Cleanout pipes as needed. If
the integrity of the pipe is
compromised, then repair the
damaged section(s).
Every two to five years.
Inspection
Where accessible, expose inlet
and/or outlet of perforated pipe
and watch for water inflow and/or
outflow.
Minimum Annually
Storm Drain Lines Maintenance Plan
Storm drain lines are subject to sedimentation as well as tree roots clogging the flow path or altering the
pipe slope. Maintenance is important to ensure these storm drain systems perform as they were designed.
Routine Maintenance Table
Required
Action Maintenance Objective Frequency of Action
Inspection
Use a video camera to inspect the
condition of the storm drain pipes.
Cleanout pipes as needed. If the
integrity of the pipe is
compromised, then repair the
damaged section(s).
Every two to five years.
Dry Extended Detention Basin
Routine Maintenance Table (Summary from Chapter 6 of UDFCD)
Required
Action Maintenance Objective Frequency of Action
Lawn mowing
and Lawn care
Occasional mowing to limit unwanted
vegetation. Maintain irrigated turf
grass as 2 to 4 inches tall and non-
irrigated native turf grasses at 4 to 6
inches.
Routine – Depending on aesthetic
requirements.
Sediment,
Debris and Litter
removal
Remove sediment, debris and litter
from the entire pond to minimize
outlet clogging and improve
aesthetics.
Routine – Including just before annual storm
seasons (that is, April and May), end of
storm season after leaves have fallen, and
following significant rainfall events.
Major Pond
Sediment
removal
Remove accumulated sediment from
the bottom of the basin.
Non-routine – Performed when sediment
accumulation occupies 20 percent of the
WQCV. This may vary considerably.
Inspections required every 10 years, non-
routine maintenance performed at that time
if necessary. Typical is 10 – 20 years if no
construction activities take place in the
tributary watershed.
Inspections
Inspect basins to ensure that the
basin continues to function as initially
intended. Examine the outlet for
clogging, erosion, slumping,
excessive sedimentation levels,
overgrowth, embankment and
spillway integrity, and damage to any
structural element.
Routine – Annual inspection of hydraulic and
structural facilities. Also check for obvious
problems during routine maintenance visits,
especially for plugging of outlets.
Pre-Sedimentation Forebay
Routine Maintenance Table (Summary from Chapter 6 of UDFCD)
Required
Action Maintenance Objective Frequency of Action
Debris and Litter
removal
Remove debris and litter as needed.
Floating debris can clog the
overflow structure
Routine – Including just before annual storm
seasons (that is, April and May), end of storm
season after leaves have fallen, and following
significant rainfall events.
Forebay
Sediment
removal
Remove accumulated sediment
from the bottom of the basin
before it becomes a significant
source of pollutants for the
remainder of the pond. Inspect to
ensure that sediment does not
result in excessive algae growth or
mosquito production.
Non-routine – Performed when sediment
accumulation appears to result in excessive
algae growth or mosquito production. This
may vary considerably, but expect to do this
every approximately every 4 years, as
necessary per inspection if no construction
activities take place in the tributary watershed.
More often if they do.
Inspections
Inspect to ensure that the facility
continues to function as initially
intended. Examine the outlet for
clogging, erosion, slumping,
excessive sedimentation levels,
overgrowth, embankment integrity
and damage to any structural
element.
Routine – Annual inspection of hydraulic and
structural facilities. Also check for obvious
problems during routine maintenance visits,
especially for plugging of outlets. Note the
amount of sediment in the forebay and look
for debris at the outlet structure.
Bioretention
Routine Maintenance Table (Summary from Chapter 6 of UDFCD)
Required
Action Maintenance Objective Frequency of Action
Lawn mowing
and vegetative
care
Occasional mowing of grasses and
weed removal to limit unwanted
vegetation. Maintain irrigated turf
grass as 2 to 4 inches tall and non-
irrigated native turf grasses at 4 to 6
inches.
Routine – Depending on aesthetic
requirements, planting scheme and cover.
Weeds should be removed before they
flower.
Debris and litter
removal and
snow
stockpiling
Remove debris and litter from
bioretention area and upstream
concrete forebay to minimize
clogging of the sand media. Remove
debris and litter from the pond area
and outlet orifice plate to minimize
clogging. Remove debris and litter
from curb channel and sidewalk
chase outlets adjacent to pond if
applicable to minimize clogging.
Avoid stockpiling snow in the
bioretention area to minimize
clogging from sediment
accumulation.
Routine – Including just before annual storm
seasons and after snow season (April or
May), end of storm season after leaves have
fallen, and following significant rainfall
events.
Inspections
Inspect detention area to determine
if the sand media is allowing
acceptable infiltration. If standing
water persists for more than 24 hours
after storm runoff has ceased,
clogging should be further
investigated and remedied.
Routine – Biannual inspection of the
hydraulic performance.
Growing media
replacement
Restore infiltration capacity of
bioretention facilities.
Non-routine – Performed when clogging is
due to the migration of sediments deep into
the pore spaces of the media. The frequency
of replacement will depend on site-specific
pollutant loading characteristics.
Vegetated and/or Cobble Swales
Routine Maintenance Table (Summary from Table GS-1, Chapter 6 of UDFCD)
Required
Action Maintenance Objective Frequency of Action
Lawn mowing
and Lawn care
Maintain irrigated grass at 2 to 4
inches tall and non-irrigated native
grass at 6 to 8 inches tall. Collect
cuttings and dispose of them offsite
or use a mulching mower.
Routine – As needed.
Debris and Litter
removal
Keep the swale area clean for
aesthetic reasons, which also reduces
the potential for floatables being
flushed downstream.
Routine – As needed by inspection, but no
less than two times per year.
Sediment
removal
Remove accumulated sediment near
culverts and in channels to maintain
flow capacity. Replace the grass areas
damaged in the process.
Routine – As needed by inspection. Estimate
the need to remove sediment from 3 to 10
percent of total length per year, as
determined by annual inspection.
Inspections
Check the grass for uniformity of
cover, sediment accumulation in the
swale, and near culverts.
Routine – Annual inspection is suggested.