HomeMy WebLinkAboutDrainage Reports - 06/21/2019 (2)
DRAINAGE MEMORANDUM
TEACHING TREE
424 PINE STREET
FORT COLLINS, CO
PEC PROJECT NO. 180847
JUNE 2018
PREPARED BY
PROFESSIONAL ENGINEERING CONSULTANTS PA
420 Linden Street, Suite 110 Fort Collins, CO 80524 970-232-9558 www.pec1.com
June 2019 Project No. 180847
DRAINAGE MEMORANDUM
TEACHING TREE
June 18, 2019
Stormwater Utilities
City of Fort Collins
P.O. Box 580
Fort Collins, CO 80522
RE: Teaching Tree – 424 Pine Street
This project consists of interior and exterior renovations to the Teaching Tree building (formerly
United Way of Larimer County) located at 424 Pine Street in Fort Collins, Colorado. The proposed exterior
improvements include the addition of two playground areas, landscaping, and additional sidewalk paving.
The site is located within the Northside Aztlan Community Center development and is owned by
the City of Fort Collins. With the departure of United Way, Teaching Tree is interested in further
developing the property to meet their growing needs. Evaluation of the primary site and landscape plans
show an increase in impervious area due to the proposed exterior alterations at the site. The site sits
within close proximity to the Cache La Poudre River where storm drainage from the existing parking lot
and building site is currently discharged via earthen channel swale directly to the river. This drainage swale
is also utilized by the Aztlan Community Center site.
This memorandum includes discussion and analysis of the proposed stormwater management
systems to be applied at this site to reduce runoff, improve water quality, and comply with the
requirements of the City of Fort Collins Stormwater Criteria Manual. Please do not hesitate to contact me
with any questions or information request regarding our project.
Sincerely,
Scott Turnbull, P.E.
Professional Engineering Consultants, P.A.
06/18/2019
June 2019 Project No. 180847
DRAINAGE MEMORANDUM
TEACHING TREE
TABLE OF CONTENTS
1. Location and Project Description .......................................................................................................... 1
1.1 Project Location ............................................................................................................................ 1
1.2 Proposed Development ................................................................................................................ 1
2. Drainage Basins and Sub-Basins ........................................................................................................... 1
2.1 Major Basins .................................................................................................................................. 1
2.2 Existing Sub-Basins ........................................................................................................................ 2
3. Stormwater Evaluation and Management ............................................................................................ 2
3.1 Existing Conditions ........................................................................................................................ 2
3.2 Proposed Conditions ..................................................................................................................... 2
3.3 General Concept ........................................................................................................................... 3
4. Erosion and Sediment Control .............................................................................................................. 4
5. Conclusion ............................................................................................................................................. 5
6. References ............................................................................................................................................ 5
LIST OF TABLES
Table 1: Existing Weighted Runoff Coefficient ............................................................................................. 2
Table 2: Proposed Weighted Runoff Coefficient .......................................................................................... 3
Table 3: Existing and Proposed Peak Runoff ................................................................................................. 3
ATTACHMENTS
Attachment A – Grading and Drainage Plan
Attachment B – Vegetated Buffer Fact Sheet
Attachment C – Bioretention Fact Sheet
Attachment D – Underdrain WQCV Worksheet
Attachment E – FEMA FIRM Map
Attachment F – NRCS Soils Report
Attachment G – Standard Operating Procedure (SOP)
June 2019 PEC Project No. 180847 1
DRAINAGE MEMORANDUM
TEACHING TREE
1. LOCATION AND PROJECT DESCRIPTION
1.1 Project Location
The existing building at 424 Pine St. is located on 1.95-acre Lot 3, Northside Aztlan Community
Center. This lot is situated near the Legacy Senior Center and Willow Street Condos to the
south and the Poudre River to the north. The existing conditions at the site include the existing
building, parking facilities, driveways, playgrounds, and underground utilities. Current
stormwater runoff from the building site is by means of sheet flow away from the building to
the existing drainage swale and subsurface rain leaders which also discharge to the swale. The
existing parking lot drains to this swale by a curb cut on the north end of the lot. This swale
also collects runoff from several surrounding properties and discharges to the Poudre River.
1.2 Proposed Development
The proposed improvements to the site will consist of additional playground areas,
landscaping, and pedestrian sidewalks. Due to these improvements, the net change in
impervious area is approximately 1,360 SF. This represents approximately 2.5% increase in
impervious area than the existing site. The project site is known to have soil and groundwater
contamination. Proposed development will attempt to limit excavation and earthmoving
activities as much as possible. Playground areas will consist of pervious materials with
underdrain systems as a stormwater treatment technique acting as a modified rain garden
before discharging to the existing swale.
The increased stormwater runoff from the site shall be treated by permanent low impact
development techniques to promote infiltration. The increase in impervious area compared
to existing is minimal (2.5%) and additional management techniques will be applied. On-site
filtration will be provided by means of the wood mulch surface with underdrains within play
areas (effetely creating a rain garden concept). Runoff from the new sidewalk on the
northeast site of the building will be treated with a vegetated buffer before entering the
swale. These approaches will limit earthwork in the contaminated soils compared to
construction of new detention facilities. Existing drainage patterns on the site will be
maintained. A Grading and Drainage Plan is included in Appendix A.
2. DRAINAGE BASINS AND SUB-BASINS
2.1 Major Basins
The project site is located within the Cache La Poudre basin which is a tributary to the South
Platte River per maps produced by the City of Fort Collins1. Runoff from the project site is
1 https://www.fcgov.com/utilities/what-we-do/stormwater/drainage-basins/
June 2019 PEC Project No. 180847 2
DRAINAGE MEMORANDUM
TEACHING TREE
directed to the existing swale and green space to the north of the project site. The project
area is located outside of floodplain designated by FEMA map 08069C0979H (see Appendix
B).
2.2 Existing Sub-Basins
Historical drainage for the existing site is generally from west to east towards the Cache La
Poudre River. The soils on this property consist of Paoli fine sandy loam which is classified by
NRCS as hydraulic group ‘A’ soils (see soil report in Appendix C). These soils consist primarily
of well drained sands having high infiltration rates and low runoff potential.
3. STORMWATER EVALUATION AND MANAGEMENT
3.1 Existing Conditions
The project site currently includes a building and exterior site improvements. Based upon
these existing conditions, the weighted runoff coefficient for the rational method is shown in
Table 1. Areas are estimated from aerial photography of the site.
Table 1: Existing Weighted Runoff Coefficient
Surface Type Area (SF) Runoff Coefficient
2 and 10-yr 100-yr
Pavement 39,000 0.95 1.00
Roof 15,000 0.95 1.00
Turf 2-7% Slope,
Sandy Soil 38,000 0.15 0.20
Total
Area2 92,000 Weighted = 0.62 Weighted = 0.67
3.2 Proposed Conditions
The proposed site conditions are shown in Table 2. The proposed improvements which impact
stormwater runoff consist primarily of impervious sidewalk paving. Accounting for an
additional 1,360 SF of pavement, the weighted runoff coefficient is shown in Table 2.
2 Total area includes additional land outside of the current property line for development of playground areas.
June 2019 PEC Project No. 180847 3
DRAINAGE MEMORANDUM
TEACHING TREE
Table 2: Proposed Weighted Runoff Coefficient
Surface Type Area (SF) Runoff Coefficient
2 and 10-yr 100-yr
Pavement 40,360 0.95 1.00
Roof 15,000 0.95 1.00
Turf 2-7% Slope,
Sandy Soil 36,640 0.15 0.20
Total
Area2 92,000 Weighted = 0.63 Weighted = 0.68
Based upon these site conditions, the peak stormwater discharge is computed using the
Rational Method for a time of concentration of 5 minutes reflecting the small size of the site.
The peak discharges from the site are shown in Table 3.
Table 3: Existing and Proposed Peak Runoff
Storm Event Rainfall
(in/hr)
Existing
(cfs)
Proposed
(cfs)
Increased
Discharge (cfs)
Increase
Discharge (%)
2-year 2.85 3.73 3.80 0.07 1.9%
10-year 4.87 6.37 6.49 0.12 1.9%
100-year 9.95 14.07 14.32 0.25 1.8%
3.3 General Concept
The proposed exterior improvements to the existing building will maintain existing drainage
patterns on the site. Stormwater runoff will continue to be directed towards the existing
drainage swale. The additional 0.25 CFS of peak runoff of the 100-year storm event will be
treated by existing drainage infrastructure and additional storm water treatment techniques
applied on the project site to improve water quality. These treatment techniques include:
1) Utilization of the existing pervious areas and drainage swales to infiltrate stormwater
prior to discharge to the Cache La Poudre.
2) Construct a vegetated buffer area between the new proposed sidewalks/ play areas
and the existing swale along the north perimeter of the site designed in accordance
with City of Fort Collins criteria. Runoff from the proposed 5’ wide sidewalk will sheet
flow across a 14’-wide (minimum) grass area at less than 10% slope to slow and
infiltrate water. The site soils are hydraulic group A and have high infiltration and
low runoff potential.
3) Installation of engineered wood fibers (EWF) mulch playground surfaces within the
play areas to promote infiltration of runoff and exceeding the size required for Water
Quality Capture Volume (WQCV) per Urban Drainage and Flood Control District
(UDFCD) criteria. The engineered wood mulch will be 12” minimum depth, free of
bark, leaves, twigs, and other foreign or toxic material, and of material meeting
June 2019 PEC Project No. 180847 4
DRAINAGE MEMORANDUM
TEACHING TREE
ASTM F2075. The playground areas will be drained via perforated underdrain pipe
to the existing swale north of the project site. See cross section in Figure 1 provided
by the project landscape plans.
Figure 1 – Play Area “Rain Garden” Cross Section
The underdrain pipe will be backfilled with gravel aggregate and separated from
contaminated soils by an impervious liner meeting UDFCD criteria for bioretention
areas. These playground areas will function similarly to rain gardens (see Attachment
C for calculation worksheet) and reduce the release rate of stormwater runoff than
if it flowed directly to the pipe outfall. Overflow of these locations will be to existing
drainages matching current drainage patterns of the site.
4) Due to removal of sidewalk pavement for the playground on the south side of the
building, near the main entrance, runoff rates and volume will decrease at this
location.
4. EROSION AND SEDIMENT CONTROL
The contractor will install the following temporary measures to mitigate erosion and sediment
transport from the site during construction activities:
· Silt Fence – A silt fence will be installed around the parameter of the disturbed
site to prevent sediment runoff towards the Poudre River. Silt Fence ditch
checks will also be provided to capture sediment transport in the swale.
· Curb/Flume Protection – Drain protection will installed at the inlets to the
curbs/flumes discharging from the site to capture any sediment runoff after
the flumes and paving have been installed.
June 2019 PEC Project No. 180847 5
DRAINAGE MEMORANDUM
TEACHING TREE
· Erosion Control Mats – Mats will be installed at locations were site runoff will
be discharged into the existing drainage ditch for temporary bank protection
during construction.
· Construction Entrance – A gravel entrance or equivalent vehicle tracking pad
will be constructed/installed to reduce the amount of sediment tracked by
vehicles leaving the site onto public roadways.
All erosion and sediment control measures will comply with City of Fort Collins requirements.
5. CONCLUSION
Analysis was conducted to determine proposed conditions runoff in comparison to existing
conditions at the project site. The net runoff increase from the proposed site improvements is
relatively small compared to existing conditions and stormwater management techniques will be
implemented to infiltrate and filter additional stormwater runoff prior to discharge to the existing
drainage swale leading to the Cache La Poudre River. No additional detention facilities are to be
provided in an effort to limit earthwork in contaminated soils. Erosion control measures will be
utilized within the site to minimize sediment transport off-site during construction activities.
6. REFERENCES
Fort Collins Stormwater Criteria Manual, City of Fort Collins. Adopted January 2019.
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District (UDFCD), Revised
August 2018.
Natural Resources Conservation Service (NRCS), USDA Web Soil Survey. Accessed 12/19/2018.
ATTACHMENT A
Grading and Drainage Plan
Teaching Tree Remodel & Expansion424 Pine StreetFort Collins, CO 80527180847-000
SMT
04/04/2019
Job Number:
Drawn By:
Project Issue Date:
970 | 672 | 6570
Fort Collins, CO 80525
100% CONSTRUCTION DOCUMENTSRevision Schedule
#Date Desc.
Current Sheet Issue Date:06/10/2019
PROFESSIONAL ENGINEERING CONSULTANTS, P.A.970-232-9558 www.pec1.com420 LINDEN ST, SUITE 110 FORT COLLINS, CO 80524C3.0
GRADING PLAN
U:\FTCollins\2018\180847\000\Muni\Drawings\180847-000-C3.0-GRADING PLAN.dwg6/18/2019 11:12:22 AM
1
2
3
4
6
5
7
9
8
11
10
13
12
14
15
17
16
19
18
23
20
22
21
UNDERDRAIN PIPE KEYNOTES
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
21
20
22
23 Teaching Tree Remodel & Expansion424 Pine StreetFort Collins, CO 80527180847-000
SMT
04/04/2019
Job Number:
Drawn By:
Project Issue Date:
970 | 672 | 6570
Fort Collins, CO 80525
100% CONSTRUCTION DOCUMENTSRevision Schedule
#Date Desc.
Current Sheet Issue Date:06/10/2019
PROFESSIONAL ENGINEERING CONSULTANTS, P.A.970-232-9558 www.pec1.com420 LINDEN ST, SUITE 110 FORT COLLINS, CO 80524C3.1
DRAINAGE PLAN
U:\FTCollins\2018\180847\000\Muni\Drawings\180847-000-C3.1-DRAINAGE PLAN.dwg6/18/2019 11:12:41 AM
ATTACHMENT B
Vegetated Buffer Fact Sheet
3.14
Vegetated Buffer
The vegetated buffer cleans stormwater runoff by catching sediment and
debris between the stalks and leaves of dense vegetation. It is often used to
reduce directly connected impervious areas, allow water to infiltrate and provide
pretreatment for other BMPs.
COST AND BENEFIT CONSIDERATIONS
MAINTENANCE CONSIDERATIONS
• Reduces directly connected impervious areas.
• May be used to meet landscape requirements.
• Low construction cost.
• Flexible space for recreation and snow storage.
• Vegetated buffers require gently sloping sites,
2% minimum to 10% maximum.
• Applicable to sites with large open spaces.
• Uses existing areas, which reduces land
consumption.
• Dense cover is required to maintain the
function of this BMP. Ensure at least 80%
vegetated cover.
• Protect vegetated buffers from compaction.
Prevent cars from driving onto the buffer.
Amend soils that become compacted.
• Provide wheel stops or similar barrier adjacent
to parking and drives.
• Trim and maintain vegetation along edges
where impervious area flows to buffer.
• Monitor for invasive species and remove as
needed.
• Remove accumulated sediment in level
spreader to maintain dispersed flow.
Section Three: LID BMP Fact Sheet 3.15City of Fort Collins | LID Implementation Manual• Plan and delineate buffer areas prior to
site disturbance to protect subgrade from
construction related compaction.
• Protect finished BMPs from construction
sediment including landscape installation.
During establishment protect BMPs from
washout.
• Construct level spreaders parallel to site
contours.
• Plants will require establishment irrigation
during and for a time following construction.
Precedent Projects
• Bucking Horse Apartments
DESIGN CONSIDERATIONS
CONSTRUCTION CONSIDERATIONS
• Level spreaders are required for concentrated
flow applications and recommended for
sheet flow applications.
• Select vegetation with uniform cover
characteristics. Avoid bunch type vegetation
that can result in concentrated flow between
plants.
• Where feasible provide a 2-3” drop between
the top of the vegetated buffer and the
contributing impervious area. This drop
prevents vegetation from growing against the
impervious area and concentrating flow.
• Confirm vegetated flow path is not within
footprint of future development.
• Permaculture techniques such as keyline
design may be used to increase infiltration.
• BMP is not applicable to rights-of-way.
Notes and References
• UDFCD Treatment BMP Fact Sheet T-01
• Grass Buffer Seed Mix Specification (Appendix D)
* This is a graphic representation. For more technical
guidance, refer to the construction detail.
ATTACHMENT C
Bioretention Fact Sheet
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-1
Urban Storm Drainage Criteria Manual Volume 3
Terminology
The term bioretention refers to the
treatment process although it is also
frequently used to describe a BMP
that provides biological uptake and
retention of the pollutants found in
stormwater runoff. This BMP is
sometimes referred to as a porous
landscape detention (PLD) area or
rain garden.
Photograph B-1. This recently constructed rain garden provides
bioretention of pollutants, as well as an attractive amenity for a
residential building. Treatment should improve as vegetation matures.
Description
A BMP that utilizes bioretention is an
engineered, depressed landscape area
designed to capture and filter or infiltrate the
water quality capture volume (WQCV).
BMPs that utilize bioretention are frequently
referred to as rain gardens or porous
landscape detention areas (PLDs). The term
PLD is common in the UDFCD region as this
manual first published the BMP by this name
in 1999. In an effort to be consistent with
terms most prevalent in the stormwater
industry, this document generally refers to the
treatment process as bioretention and to the
BMP as a rain garden.
The design of a rain garden may provide
detention for events exceeding that of the WQCV. There are
generally two ways to achieve this. The design can provide the
flood control volume above the WQCV or the design can provide
and slowly release the flood control volume in an area
downstream of one or more rain gardens. See the Storage chapter
in Volume 2 of the USDCM for more information.
This infiltrating BMP requires consultation with a geotechnical
engineer when proposed adjacent to a structure. A geotechnical
engineer can assist with evaluating the suitability of soils,
identifying potential impacts, and establishing minimum distances
between the BMP and structures.
Bioretention
(Rain Garden)
Functions
LID/Volume Red. Yes
WQCV Capture Yes
WQCV+Flood Control Yes
Fact Sheet Includes
EURV Guidance No
Typical Effectiveness for Targeted
Pollutants3
Sediment/Solids Very Good1
Nutrients Moderate
Total Metals Good
Bacteria Moderate
Other Considerations
Life-cycle Costs4 Moderate
1 Not recommended for watersheds with
high sediment yields (unless pretreatment is
provided).
3 Based primarily on data from the
International Stormwater BMP Database
(www.bmpdatabase.org).
4 Based primarily on BMP-REALCOST
available at www.udfcd.org. Analysis
based on a single installation (not based on
the maximum recommended watershed
tributary to each BMP).
T-3 Bioretention
B-2 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
Site Selection
This BMP allows WQCV treatment within one or more areas
designated for landscape (see design step 7 for suggusted
vegetation). In this way, it is an excellent alternative to
extended detention basins for small sites. A typical rain
garden serves a tributary area of one impervious acre or less,
although they can be designed for larger tributary areas.
Multiple installations can be used within larger sites. Rain
gardens should not be used when a baseflow is anticipated.
They are typically small and installed in locations such as:
Parking lot islands
Street medians
Landscape areas between the road and a detached walk
Planter boxes that collect roof drains
Bioretention requires a stable watershed. Retrofit
applications are typically successful for this reason. When
the watershed includes phased construction, sparsely
vegetated areas, or steep slopes in sandy soils, consider
another BMP or provide pretreatment before runoff from
these areas reaches the rain garden.
The surface of the rain garden should be flat. For this
reason, rain gardens can be more difficult to incorporate into
steeply sloping terrain; however, terraced applications of
these facilities have been successful in other parts of the
country.
When bioretention (and other BMPs used for infiltration) are
located adjacent to buildings or pavement areas, protective measures should be implemented to avoid
adverse impacts to these structures. Oversaturated subgrade soil underlying a structure can cause the
structure to settle or result in moisture-related problems. Wetting of expansive soils or bedrock can cause
swelling, resulting in structural movements. A geotechnical engineer should evaluate the potential impact
of the BMP on adjacent structures based on an evaluation of the subgrade soil, groundwater, and bedrock
conditions at the site. Additional minimum requirements include:
In locations where subgrade soils do not allow infiltration and/or where infiltration could adversely
impact adjacent structures, include a drainage layer (with underdrain) under the growing medium.
In locations where potentially expansive soils or bedrock exist, placement of a rain garden adjacent to
structures and pavement should only be considered if the BMP includes a drainage layer (with
underdrain) and an impermeable geomembrane liner designed to restrict seepage.
Benefits
Bioretention uses multiple
treatment processes to remove
pollutants, including
sedimentation, filtering,
adsorption, evapotranspiration,
and biological uptake of
constituents.
Stormwater treatment occurs
within attractive landscaped areas.
There is a potential reduction of
irrigation requirements by taking
advantage of site runoff.
Limitations
Additional design and
construction steps are required for
placement of any ponding or
infiltration area near or upgradient
from a building foundation and/or
when expansive (low to high
swell) soils exist. This is
discussed in the design procedure
section.
In developing or otherwise erosive
watersheds, high sediment loads
can clog the facility.
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-3
Urban Storm Drainage Criteria Manual Volume 3
Designing for Maintenance
Recommended maintenance practices for all BMPs are in Chapter
6 of this manual. During design, consider the following to ensure
ease of maintenance over the long-term:
Do not put a filter sock on the underdrain. This is not
necessary and can cause the underdrain to clog.
The best surface cover for a rain garden is full vegetation. Use
rock mulch sparingly within the rain garden because rock
mulch limits infiltration and is more difficult to maintain.
Wood mulch handles sediment build-up better than rock
mulch; however, wood mulch floats and may clog the
overflow depending on the configuration of the outlet or settle
unevenly. Some municipalities may not allow wood mulch for
this reason.
Consider all potential maintenance requirements such as mowing (if applicable) and replacement of
the growing medium. Consider the method and equipment for each task required. For example, in a
large rain garden where the use of hand tools is not feasible, does the shape and configuration of the
rain garden allow for removal of the growing medium using a backhoe?
Provide pre-treatment when it will reduce the extent and frequency of maintenance necessary to
maintain function over the life of the BMP. For example, if the tributary is larger than one acre,
prone to debris or the use of sand for ice control, consider a small forebay.
Make the rain garden as shallow as possible. Increasing the depth unnecessarily can create erosive
side slopes and complicate maintenance. Shallow rain gardens are also more attractive.
Design and adjust the irrigation system (temporary or permanent) to provide appropriate water for the
establishment and maintenance of selected vegetation.
Design Procedure and Criteria
1. Subsurface Exploration and Determination of a No-Infiltration, Partial Infiltration, or Full
Infiltration Section: Infiltration BMPs can have three basic types of sections. The appropriate
section will depend on land use and activities, proximity to adjacent structures and soil
characteristics. Sections of each installation type are shown in Figure B-1.
No-Infiltration Section: This section includes an underdrain and an impermeable liner that
prevents infiltration of stormwater into the subgrade soils. Consider using this section when any
of the following conditions exist:
o The site is a stormwater hotspot and infiltration could result in contamination of
groundwater.
o The site is located over contaminated soils and infiltration could mobilize these
contaminants.
o The facility is located over potentially expansive soils or bedrock that could swell due to
infiltration and potentially damage adjacent structures (e.g., building foundation or
pavement).
Partial Infiltration Section: This section does not include an impermeable liner, and allows
some infiltration. Stormwater that does not infiltrate is collected and removed by an underdrain
Is Pretreatment Needed?
Designing the inflow gutter to
the rain garden at a minimal
slope of 0.5% can facilitate
sediment and debris deposition
prior to flows entering the BMP.
Be aware, this will reduce
maintenance of the BMP, but
may require more frequent
sweeping of the gutter to ensure
that the sediment does not
impede flow into the rain
garden.
T-3 Bioretention
B-4 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
system.
Full Infiltration Section: This section is designed to infiltrate the water stored in the basin
into the subgrade below. UDFCD recommends a minimum infiltration rate of 2 times the rate
needed to drain the WQCV over 12 hours. A conservative design could utilize the partial
infiltration section with the addition of a valve at the underdrain outlet. In the event that
infiltration does not remain adequate following construction, the valve could be opened and
allow this section to operate as a partial infiltration section.
A geotechnical engineer should scope and perform a subsurface study. Typical geotechnical
investigation needed to select and design the section includes:
Prior to exploration review geologic and geotechnical information to assess near-surface soil,
bedrock and groundwater conditions that may be encountered and anticipated ranges of
infiltration rate for those materials. For example, if the facility is located adjacent to a structure
and the site is located in a general area of known shallow, potentially expansive bedrock, a no-
infiltration section will likely be required. It is also possible that this BMP may be infeasible,
even with a liner, if there is a significant potential for damage to the adjacent structures (e.g.,
areas of dipping bedrock).
Drill exploratory borings or exploratory pits to characterize subsurface conditions beneath the
subgrade and develop requirements for subgrade preparation. Drill at least one boring or pit for
every 40,000 ft2, and at least two borings or pits for sites between 10,000 ft2 and 40,000 ft2.
The boring or pit should extend at least 5 feet below the bottom of the base, and at least 20 feet
in areas where there is a potential of encountering potentially expansive soils or bedrock. More
borings or pits at various depths may be required by the geotechnical engineer in areas where
soil types may change, in low-lying areas where subsurface drainage may collect, or where the
water table is likely within 8 feet below the planned bottom of the base or top of subgrade.
Installation of temporary monitoring wells in selected borings or pits for monitoring
groundwater levels over time should be considered where shallow groundwater is encountered.
Perform laboratory tests on samples obtained from the borings or pits to initially characterize
the subgrade, evaluate the possible section type, and to assess subgrade conditions for
supporting traffic loads. Consider the following tests: moisture content (ASTM D 2216); dry
density (ASTM D 2936); Atterberg limits (ASTM D 4318); gradation (ASTM D 6913); swell-
consolidation (ASTM D 4546); subgrade support testing (R-value, CBR or unconfined
compressive strength); and hydraulic conductivity. A geotechnical engineer should determine
the appropriate test method based on the soil type.
For sites where a full infiltration section may be feasible, perform on-site infiltration tests using
a double-ring infiltrometer (ASTM D 3385). Perform at least one test for every 160,000 ft2 and
at least two tests for sites between 40,000 ft2 and 160,000 ft2. The tests should be located near
completed borings or pits so the test results and subsurface conditions encountered in the
borings can be compared, and at least one test should be located near the boring or pit showing
the most unfavorable infiltration condition. The test should be performed at the planned top of
subgrade underlying the growing media.
Be aware that actual infiltration rates are highly variable dependent on soil type, density and
moisture content and degree of compaction as well as other environmental and construction
influences. Actual rates can differ an order of magnitude or more from those indicated by
infiltration or permeability testing. Select the type of section based on careful assessment of the
subsurface exploration and testing data.
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-5
Urban Storm Drainage Criteria Manual Volume 3
The following steps outline the design procedure and criteria, with Figure B-1 providing a corresponding
cross-section.
2. Basin Storage Volume: Provide a storage volume based on a 12-hour drain time.
Find the required WQCV (watershed inches of runoff). Using the imperviousness of the tributary
area (or effective imperviousness where LID elements are used upstream), use Figure 3-2 located
in Chapter 3 of this manual to determine the WQCV based on a 12-hour drain time.
Calculate the design volume as follows: 𝑉 = �WQCV12�𝐴 Equation B-1
Where:
V= design volume (ft3)
A = area of watershed tributary to the rain garden (ft2)
3. Basin Geometry: UDFCD recommends a maximum WQCV ponding depth of 12 inches to
maintain vegetation properly. Provide an inlet or other means of overflow at this elevation.
Depending on the type of vegetation planted, a greater depth may be utilized to detain larger
(more infrequent) events. The bottom surface of the rain garden, also referred to here as the filter
area, should be flat. Sediment will reside on the filter area of the rain garden; therefore, if the
filter area is too small, it may clog prematurely. If the filter area is not flat, the lowest area of the
filter is more likely to clog as it will have a higher sediment loading. Increasing the filter area
will reduce clogging and decrease the frequency of maintenance. Equation B-2 provides a
minimum filter area allowing for some of the volume to be stored beyond the area of the filter
(i.e., above the sideslopes of the rain garden).
Note that the total surcharge volume provided by the design must also equal or exceed the design
volume. Where needed to meet the the required volume, also consider the porosity of the media at 14
percent. Use vertical walls or slope the sides of the basin to achieve the required volume. Sideslopes
should be no steeper than 4:1 (horizontal:vertical).
AIAF02.0=
Equation B-2
Where:
AF= minimum (flat) filter area (ft2)
A = area tributary to the rain garden (ft2)
I = imperviousness of area tributary to the rain garden (percent expressed as a decimal)
T-3 Bioretention
B-6 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
4. Growing Medium: Provide a minimum of 18 inches of growing medium to enable
establishment of the roots of the vegetation (see Figure B-1). A previous version of this manual
specified a mixture consisting of 85% coarse sand and a 15% compost/shredded paper mixture
(by volume). Based on field monitoring of this medium, compost was removed to reduce export
of nutrients and fines and silts were added to both benefit the vegetation and increase capture of
metals in stormwater.
Table B-1 specifies the growing media as well as other materials discussed in this Fact Sheet.
Growing media is engineered media that requires a high level of quality control and must almost
always be imported. Obtaining a particle size distribution and nutrient analysis is the only way to
ensure that the media is acceptable. UDFCD has identified placement of media not meeting the
specification as the most frequent cause of failure. Sample the media after delivery and prior to
placement or obtain a sample from the supplier in advance of delivery and placement and have this
analyzed prior to delivery.
Other Rain Garden Growing Medium Amendments
The specified growing medium was designed for filtration ability, clogging characteristics, and
vegetative health. It is important to preserve the function provided by the rain garden growing
medium when considering additional materials for incorporation into the growing medium or into the
standard section shown in Figure B-1. When desired, amendments may be included to improve water
quality or to benefit vegetative health as long as they do not add nutrients, pollutants, or modify the
infiltration rate. For example, a number of products, including steel wool, capture and retain
dissolved phosphorus (Erickson 2009). When phosphorus is a target pollutant, proprietary materials
with similar characteristics may be considered. Do not include amendments such as top soil, sandy
loam, and compost.
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-7
Urban Storm Drainage Criteria Manual Volume 3
Table B-1. Material specification for bioretention/rain garden facilities
T-3 Bioretention
B-8 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
5. Underdrain System: When using an underdrain system, provide a control orifice sized to drain
the design volume in 12 hours or more (see Equation B-3). Use a minimum orifice size of 3/8
inch to avoid clogging. This will provide detention and slow release of the WQCV, providing
water quality benefits and reducing impacts to downstream channels. Space underdrain pipes a
maximum of 20 feet on center. Provide cleanouts to enable maintenance of the underdrain.
Cleanouts can also be used to conduct an inspection (by camera) of the underdrain system to
ensure that the pipe was not crushed or disconnected during construction.
Calculate the diameter of the orifice for a 12-hour drain time using Equation B-3 (Use a minimum orifice
size of 3/8 inch to avoid clogging.):
𝐷12 hour drain time =�𝑉1414 𝑦0.41 Equation B-3
Where:
D = orifice diameter (in)
y = distance from the lowest elevation of the storage volume
(i.e., surface of the filter) to the center of the orifice (ft)
V = volume (WQCV or the portion of the WQCV in the rain garden)
to drain in 12 hours (ft3)
In previous versions of this manual, UDFCD recommended that the underdrain be placed in an
aggregate layer and that a geotextile (separator fabric) be placed between this aggregate and the
growing medium. This version of the manual replaces that section with materials that, when used
together, eliminate the need for a separator fabric.
The underdrain system should be placed within an 6-inch-thick section of CDOT Class B or Class C
filter material meeting the gradation in Table B-1. Use slotted pipe that meets the slot dimensions
provided in Table B-3.
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-9
Urban Storm Drainage Criteria Manual Volume 3
6. Impermeable Geomembrane
Liner and Geotextile
Separator Fabric: For no-
infiltration sections, install a
30 mil (minimum) PVC
geomembrane liner, per Table
B-1, on the bottom and sides of
the basin, extending up at least
to the top of the underdrain
layer. Provide at least 9 inches
(12 inches if possible) of cover
over the membrane where it is
attached to the wall to protect
the membrane from UV
deterioration. The
geomembrane should be field-
seamed using a dual track
welder, which allows for non-
destructive testing of almost
all field seams. A small
amount of single track is
allowed in limited areas to
seam around pipe perforations,
to patch seams removed for
destructive seam testing, and
for limited repairs. The liner
should be installed with slack
to prevent tearing due to
backfill, compaction, and
settling. Place CDOT Class B
geotextile separator fabric
above the geomembrane to
protect it from being punctured
during the placement of the
filter material above the liner.
If the subgrade contains angular
rocks or other material that
could puncture the
geomembrane, smooth-roll the
surface to create a suitable
surface. If smooth-rolling the
surface does not provide a
suitable surface, also place the separator fabric between the geomembrane and the underlying
subgrade. This should only be done when necessary because fabric placed under the
geomembrane can increase seepage losses through pinholes or other geomembrane defects.
Connect the geomembrane to perimeter concrete walls around the basin perimeter, creating a
watertight seal between the geomembrane and the walls using a continuous batten bar and anchor
connection (see Figure B-3). Where the need for the impermeable membrane is not as critical,
the membrane can be attached with a nitrile-based vinyl adhesive. Use watertight PVC boots for
underdrain pipe penetrations through the liner (see Figure B-2) or the technique shown in photo
B-3.
Photograph B-2. The impermeable membrane in this photo has ripped
from the bolts due to placement of the media without enough slack in the
membrane.
Photograph B-3. Ensure a water-tight connection where the underdrain
penetrated the liner. The heat-welded “boot” shown here is an alternative to
the clamped detail shown in Figure B-2.
T-3 Bioretention
B-10 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
Table B-2. Physical requirements for separator fabric1
1 Strength values are in the weaker principle direction
2 As measured in accordance with ASTM D 4632
7. Inlet and Outlet Control: In order to provide the proper drain time, the bioretention area can be
restricted at the underdrain outlet with an orifice plate or can be designed without an underdrain
(provided the subgrade meets the
requirements above). Equation B-3 is
a simplified equation for sizing an
orifice plate for a 12-hour drain time.
UD-BMP or UD-Detention, available
at www.udfcd.org, also perform this
calculation.
How flow enters and exits the BMP is
a function of the overall drainage
concept for the site. Curb cuts can be
designed to both allow stormwater into
the rain garden as well as to provide
release of stormwater in excess of the
WQCV. Roadside rain gardens
located on a steep site might pool and
overflow into downstream cells with a
single curb cut, level spreader, or outlet
structure located at the most
downstream cell. When selecting the
Elongation < 50%2 Elongation > 50%2
Grab Strength, N (lbs.)800 (180)510 (115)ASTM D 4632
Puncture Resistance, N (lbs.)310 (70)180 (40)ASTM D 4833
Trapezoidal Tear Strength, N (lbs.)310 (70)180 (40)ASTM D 4533
Apparent Opening Size, mm (US
Sieve Size)ASTM D 4751
Permittivity, sec-1 ASTM D 4491
Permeability, cm/sec ASTM D 4491
Ultraviolet Degradation at 500 hours ASTM D 4355
k fabric > k soil for all classes
50% strength retained for all classes
Property Class B Test Method
AOS < 0.3mm (US Sieve Size No. 50)
0.02 default value, must also be greater than
that of soil
Photograph B-4. The curb cut shown allows flows to enter this
rain garden while excess flows bypass the facility.
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-11
Urban Storm Drainage Criteria Manual Volume 3
Designing for Flood Protection
Provide the WQCV in rain gardens that direct excess flow into to a landscaped basin designed for
flood control or design a single basin to provide water quality and flood control. See the Storage
chapter in Volume 2 of the USDCM for more information. UD-Detention, available at
www.udfcd.org, will facilitate design either alternative.
type and location of the outlet structure, ensure runoff will not short-circuit the rain garden. This
is a frequent problem when using a curb inlet located outside the rain garden for overflow.
For rain gardens with concentrated points of inflow, provide a forebay and energy dissipation. A
depressed concrete slab works best for a forebay. It helps maintain a vertical drop at the inlet and
allows for easily removal of sediment using a square shovel. Where rock is used for energy
dissipation, provide separator fabric between the rock and growing medium to minimize
subsidence.
8. Vegetation: UDFCD recommends that the filter area be vegetated with drought tolerant species
that thrive in sandy soils. Table B-3 provides a suggested seed mix for sites that will not need to
be irrigated after the grass has been established.
Mix seed well and broadcast, followed by hand raking to cover seed and then mulched.
Hydromulching can be effective for large areas. Do not place seed when standing water or snow
is present or if the ground is frozen. Weed control is critical in the first two to three years,
especially when starting with seed.
When using sod, specify sand–grown sod. Do not use conventional sod. Conventional sod is
grown in clay soil that will seal the filter area, greatly reducing overall function of the BMP.
When using an impermeable liner, select plants with diffuse (or fibrous) root systems, not
taproots. Taproots can damage the liner and/or underdrain pipe. Avoid trees and large shrubs
that may interfere with restorative maintenance. Plant these outside of the area of growing
medium. Use a cutoff wall to ensure that roots do not grow into the underdrain or place trees and
shrubs a conservative distance from the underdrain.
9. Irrigation: Provide spray irrigation at or above the WQCV elevation or place temporary
irrigation on top of the rain garden surface. Do not place sprinkler heads on the flat surface.
Remove temporary irrigation when vegetation is established. If left in place this will become
buried over time and will be damaged during maintenance operations.
Adjust irrigation schedules during the growing season to provide the minimum water necessary to
maintain plant health and to maintain the available pore space for infiltration.
T-3 Bioretention
B-12 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
Table B-3. Native seed mix for rain gardens
1 Wildflower seed (optional) for a more diverse and natural look.
2 PLS = Pure Live Seed.
Common Name Scientific Name Variety PLS2
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
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-13
Urban Storm Drainage Criteria Manual Volume 3
Reflective Design
A reflective design borrows the
characteristics, shapes, colors,
materials, sizes and textures of
the built surroundings. The result
is a design that fits seamlessly
and unobtrusively in its
environment.
Aesthetic Design
In addition to effective stormwater quality treatment, rain gardens can be attractively incorporated into a
site within one or several landscape areas. Aesthetically designed rain gardens will typically either reflect
the character of their surroundings or become distinct features within their surroundings. Guidelines for
each approach are provided below.
Reflecting the Surrounding
Determine design characteristics of the surrounding. This becomes the context for the drainage
improvement. Use these characteristics in the structure.
Create a shape or shapes that "fix" the forms surrounding the improvement. Make the improvement
part of the existing surrounding.
The use of material is essential in making any new
improvement an integral part of the whole. Select materials
that are as similar as possible to the surrounding
architectural/engineering materials. Select materials from the
same source if possible. Apply materials in the same
quantity, manner, and method as original material.
Size is an important feature in seamlessly blending the
addition into its context. If possible, the overall size of the
improvement should look very similar to the overall sizes of
other similar objects in the improvement area.
The use of the word texture in terms of the structure applies predominantly to the selection of plant
material. The materials used should as closely as possible, blend with the size and texture of other
plant material used in the surrounding. The plants may or may not be the same, but should create a
similar feel, either individually or as a mass.
Creating a Distinct Feature
Designing the rain garden as a distinct feature is limited only by budget, functionality, and client
preference. There is far more latitude in designing a rain garden that serves as a distinct feature. If this is
the intent, the main consideration beyond functionality is that the improvement create an attractive
addition to its surroundings. The use of form, materials, color, and so forth focuses on the improvement
itself and does not necessarily reflect the surroundings, depending on the choice of the client or designer.
T-3 Bioretention
B-14 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
Figure B-1 – Typical rain garden plan and sections
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-15
Urban Storm Drainage Criteria Manual Volume 3
T-3 Bioretention
B-16 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-17
Urban Storm Drainage Criteria Manual Volume 3
T-3 Bioretention
B-18 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
Figure B-2. Geomembrane Liner/Underdrain Penetration Detail
Figure B-3. Geomembrane Liner/Concrete Connection Detail
Bioretention T-3
November 2015 Urban Drainage and Flood Control District B-19
Urban Storm Drainage Criteria Manual Volume 3
Photograph B-3. Inadequate construction staking may have
contributed to flows bypassing this rain garden.
Photograph B-4. Runoff passed the upradient rain garden, shown in
Photo B-3, and flooded this downstream rain garden.
Construction Considerations
Proper construction of rain gardens involves careful attention to material specifications, final grades, and
construction details. For a successful project, implement the following practices:
Protect area from excessive sediment
loading during construction. This is the
most common cause of clogging of rain
gardens. The portion of the site draining
to the rain garden must be stabilized
before allowing flow into the rain
garden. This includes completion of
paving operations.
Avoid over compaction of the area to
preserve infiltration rates (for partial and
full infiltration sections).
Provide construction observation to
ensure compliance with design
specifications. Improper installation,
particularly related to facility dimensions
and elevations and underdrain elevations,
is a common problem with rain gardens.
When using an impermeable liner, ensure
enough slack in the liner to allow for
backfill, compaction, and settling without
tearing the liner.
Provide necessary quality assurance and
quality control (QA/QC) when
constructing an impermeable
geomembrane liner system, including but
not limited to fabrication testing,
destructive and non-destructive testing of
field seams, observation of geomembrane
material for tears or other defects, and air
lace testing for leaks in all field seams and
penetrations. QA/QC should be overseen
by a professional engineer. Consider
requiring field reports or other
documentation from the engineer.
Provide adequate construction staking to
ensure that the site properly drains into the
facility, particularly with respect to surface drainage away from adjacent buildings. Photo B-3 and
Photo B-4 illustrate a construction error for an otherwise correctly designed series of rain gardens.
T-3 Bioretention
B-20 Urban Drainage and Flood Control District November 2015
Urban Storm Drainage Criteria Manual Volume 3
References
Erickson, Andy. 2009. Field Applications of Enhanced Sand Filtration. University of Minnesota
Stormwater Management Practice Assessment Project Update. http://wrc.umn.edu.
Hunt, William F., Davis, Allen P., Traver, Robert. G. 2012. “Meeting Hydrologic and Water Quality
Goals through Targeted Bioretention Design” Journal of Environmental Engineering. (2012)
138:698-707. Print.
ATTACHMENT D
Underdrain Design Worksheet
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =100.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 1.000
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.40 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 3,180 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =106 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =64 sq ft
D) Actual Flat Surface Area AActual =1780 sq ft
E) Area at Design Depth (Top Surface Area)ATop =1780 sq ft
F) Rain Garden Total Volume VT=1,780 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
Engineered wood mulch playground surface (12" min depth).
No vegetation will be planted in filter media.
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =cu ft
iii) Orifice Diameter, 3/8" Minimum DO = in
Design Procedure Form: Rain Garden (RG)
S Turnbull
PEC
May 14, 2019
Teaching Tree
424 Pine St Fort Collins CO
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07.xlsm, RG 5/14/2019, 10:46 AM
Orifice restriction not
provided per City
recommendation.
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B
GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW
THE LINER IF THE SUBGRADE IS ANGULAR
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
S Turnbull
PEC
May 14, 2019
Teaching Tree
424 Pine St Fort Collins CO
Rain garden concept applied to wood mulch playground areas. No outlet orrifice restriction to be provided per City direction. Impervious liner to be provided
in order to separate contaminated soils and groundwater from the underdrain systems.
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.07.xlsm, RG 5/14/2019, 10:46 AM
No vegetation.
ATTACHMENT E
FEMA FIRM Map
TEACHING TREE
SITE
ATTACHMENT F
NRCS Soils Report
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Larimer County
Area, ColoradoNatural
Resources
Conservation
Service
December 19, 2018
Preface
Soil surveys contain information that affects land use planning in survey areas.
They highlight soil limitations that affect various land uses and provide information
about the properties of the soils in the survey areas. Soil surveys are designed for
many different users, including farmers, ranchers, foresters, agronomists, urban
planners, community officials, engineers, developers, builders, and home buyers.
Also, conservationists, teachers, students, and specialists in recreation, waste
disposal, and pollution control can use the surveys to help them understand,
protect, or enhance the environment.
Various land use regulations of Federal, State, and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil
properties that are used in making various land use or land treatment decisions.
The information is intended to help the land users identify and reduce the effects of
soil limitations on various land uses. The landowner or user is responsible for
identifying and complying with existing laws and regulations.
Although soil survey information can be used for general farm, local, and wider area
planning, onsite investigation is needed to supplement this information in some
cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/
portal/nrcs/main/soils/health/) and certain conservation and engineering
applications. For more detailed information, contact your local USDA Service Center
(https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil
Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?
cid=nrcs142p2_053951).
Great differences in soil properties can occur within short distances. Some soils are
seasonally wet or subject to flooding. Some are too unstable to be used as a
foundation for buildings or roads. Clayey or wet soils are poorly suited to use as
septic tank absorption fields. A high water table makes a soil poorly suited to
basements or underground installations.
The National Cooperative Soil Survey is a joint effort of the United States
Department of Agriculture and other Federal agencies, State agencies including the
Agricultural Experiment Stations, and local agencies. The Natural Resources
Conservation Service (NRCS) has leadership for the Federal part of the National
Cooperative Soil Survey.
Information about soils is updated periodically. Updated information is available
through the NRCS Web Soil Survey, the site for official soil survey information.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its
programs and activities on the basis of race, color, national origin, age, disability,
and where applicable, sex, marital status, familial status, parental status, religion,
sexual orientation, genetic information, political beliefs, reprisal, or because all or a
part of an individual's income is derived from any public assistance program. (Not
all prohibited bases apply to all programs.) Persons with disabilities who require
2
alternative means for communication of program information (Braille, large print,
audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice
and TDD). To file a complaint of discrimination, write to USDA, Director, Office of
Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or
call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity
provider and employer.
3
Contents
Preface....................................................................................................................2
How Soil Surveys Are Made..................................................................................5
Soil Map..................................................................................................................8
Soil Map................................................................................................................9
Legend................................................................................................................10
Map Unit Legend................................................................................................11
Map Unit Descriptions.........................................................................................11
Larimer County Area, Colorado......................................................................13
81—Paoli fine sandy loam, 0 to 1 percent slopes.......................................13
References............................................................................................................15
4
How Soil Surveys Are Made
Soil surveys are made to provide information about the soils and miscellaneous
areas in a specific area. They include a description of the soils and miscellaneous
areas and their location on the landscape and tables that show soil properties and
limitations affecting various uses. Soil scientists observed the steepness, length,
and shape of the slopes; the general pattern of drainage; the kinds of crops and
native plants; and the kinds of bedrock. They observed and described many soil
profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The
profile extends from the surface down into the unconsolidated material in which the
soil formed or from the surface down to bedrock. The unconsolidated material is
devoid of roots and other living organisms and has not been changed by other
biological activity.
Currently, soils are mapped according to the boundaries of major land resource
areas (MLRAs). MLRAs are geographically associated land resource units that
share common characteristics related to physiography, geology, climate, water
resources, soils, biological resources, and land uses (USDA, 2006). Soil survey
areas typically consist of parts of one or more MLRA.
The soils and miscellaneous areas in a survey area occur in an orderly pattern that
is related to the geology, landforms, relief, climate, and natural vegetation of the
area. Each kind of soil and miscellaneous area is associated with a particular kind
of landform or with a segment of the landform. By observing the soils and
miscellaneous areas in the survey area and relating their position to specific
segments of the landform, a soil scientist develops a concept, or model, of how they
were formed. Thus, during mapping, this model enables the soil scientist to predict
with a considerable degree of accuracy the kind of soil or miscellaneous area at a
specific location on the landscape.
Commonly, individual soils on the landscape merge into one another as their
characteristics gradually change. To construct an accurate soil map, however, soil
scientists must determine the boundaries between the soils. They can observe only
a limited number of soil profiles. Nevertheless, these observations, supplemented
by an understanding of the soil-vegetation-landscape relationship, are sufficient to
verify predictions of the kinds of soil in an area and to determine the boundaries.
Soil scientists recorded the characteristics of the soil profiles that they studied. They
noted soil color, texture, size and shape of soil aggregates, kind and amount of rock
fragments, distribution of plant roots, reaction, and other features that enable them
to identify soils. After describing the soils in the survey area and determining their
properties, the soil scientists assigned the soils to taxonomic classes (units).
Taxonomic classes are concepts. Each taxonomic class has a set of soil
characteristics with precisely defined limits. The classes are used as a basis for
comparison to classify soils systematically. Soil taxonomy, the system of taxonomic
classification used in the United States, is based mainly on the kind and character
of soil properties and the arrangement of horizons within the profile. After the soil
5
scientists classified and named the soils in the survey area, they compared the
individual soils with similar soils in the same taxonomic class in other areas so that
they could confirm data and assemble additional data based on experience and
research.
The objective of soil mapping is not to delineate pure map unit components; the
objective is to separate the landscape into landforms or landform segments that
have similar use and management requirements. Each map unit is defined by a
unique combination of soil components and/or miscellaneous areas in predictable
proportions. Some components may be highly contrasting to the other components
of the map unit. The presence of minor components in a map unit in no way
diminishes the usefulness or accuracy of the data. The delineation of such
landforms and landform segments on the map provides sufficient information for the
development of resource plans. If intensive use of small areas is planned, onsite
investigation is needed to define and locate the soils and miscellaneous areas.
Soil scientists make many field observations in the process of producing a soil map.
The frequency of observation is dependent upon several factors, including scale of
mapping, intensity of mapping, design of map units, complexity of the landscape,
and experience of the soil scientist. Observations are made to test and refine the
soil-landscape model and predictions and to verify the classification of the soils at
specific locations. Once the soil-landscape model is refined, a significantly smaller
number of measurements of individual soil properties are made and recorded.
These measurements may include field measurements, such as those for color,
depth to bedrock, and texture, and laboratory measurements, such as those for
content of sand, silt, clay, salt, and other components. Properties of each soil
typically vary from one point to another across the landscape.
Observations for map unit components are aggregated to develop ranges of
characteristics for the components. The aggregated values are presented. Direct
measurements do not exist for every property presented for every map unit
component. Values for some properties are estimated from combinations of other
properties.
While a soil survey is in progress, samples of some of the soils in the area generally
are collected for laboratory analyses and for engineering tests. Soil scientists
interpret the data from these analyses and tests as well as the field-observed
characteristics and the soil properties to determine the expected behavior of the
soils under different uses. Interpretations for all of the soils are field tested through
observation of the soils in different uses and under different levels of management.
Some interpretations are modified to fit local conditions, and some new
interpretations are developed to meet local needs. Data are assembled from other
sources, such as research information, production records, and field experience of
specialists. For example, data on crop yields under defined levels of management
are assembled from farm records and from field or plot experiments on the same
kinds of soil.
Predictions about soil behavior are based not only on soil properties but also on
such variables as climate and biological activity. Soil conditions are predictable over
long periods of time, but they are not predictable from year to year. For example,
soil scientists can predict with a fairly high degree of accuracy that a given soil will
have a high water table within certain depths in most years, but they cannot predict
that a high water table will always be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of soil in the
survey area, they drew the boundaries of these bodies on aerial photographs and
Custom Soil Resource Report
6
identified each as a specific map unit. Aerial photographs show trees, buildings,
fields, roads, and rivers, all of which help in locating boundaries accurately.
Custom Soil Resource Report
7
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of
soil map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map, and a description of each soil map unit.
8
9
Custom Soil Resource Report
Soil Map
449343044934504493470449349044935104493530449343044934504493470449349044935104493530493700 493720 493740 493760 493780 493800 493820 493840 493860 493880
493700 493720 493740 493760 493780 493800 493820 493840 493860 493880
40° 35' 33'' N 105° 4' 28'' W40° 35' 33'' N105° 4' 19'' W40° 35' 29'' N
105° 4' 28'' W40° 35' 29'' N
105° 4' 19'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 40 80 160 240
Feet
0 10 20 40 60
Meters
Map Scale: 1:890 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 13, Sep 10, 2018
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Sep 20, 2015—Oct
21, 2017
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Custom Soil Resource Report
10
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
81 Paoli fine sandy loam, 0 to 1
percent slopes
2.4 100.0%
Totals for Area of Interest 2.4 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area. The map unit descriptions, along
with the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the
landscape, however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena. Thus, the range of some
observed properties may extend beyond the limits defined for a taxonomic class.
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes. Consequently, every map unit is made
up of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used. Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps. If included in the database for a
given area, the contrasting minor components are identified in the map unit
descriptions along with some characteristics of each. A few areas of minor
components may not have been observed, and consequently they are not
mentioned in the descriptions, especially where the pattern was so complex that it
was impractical to make enough observations to identify all the soils and
miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the
usefulness or accuracy of the data. The objective of mapping is not to delineate
pure taxonomic classes but rather to separate the landscape into landforms or
landform segments that have similar use and management requirements. The
delineation of such segments on the map provides sufficient information for the
development of resource plans. If intensive use of small areas is planned, however,
onsite investigation is needed to define and locate the soils and miscellaneous
areas.
Custom Soil Resource Report
11
An identifying symbol precedes the map unit name in the map unit descriptions.
Each description includes general facts about the unit and gives important soil
properties and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major
horizons that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness,
salinity, degree of erosion, and other characteristics that affect their use. On the
basis of such differences, a soil series is divided into soil phases. Most of the areas
shown on the detailed soil maps are phases of soil series. The name of a soil phase
commonly indicates a feature that affects use or management. For example, Alpha
silt loam, 0 to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps.
The pattern and proportion of the soils or miscellaneous areas are somewhat similar
in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present
or anticipated uses of the map units in the survey area, it was not considered
practical or necessary to map the soils or miscellaneous areas separately. The
pattern and relative proportion of the soils or miscellaneous areas are somewhat
similar. Alpha-Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas
that could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion
of the soils or miscellaneous areas in a mapped area are not uniform. An area can
be made up of only one of the major soils or miscellaneous areas, or it can be made
up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil
material and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
12
Larimer County Area, Colorado
81—Paoli fine sandy loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: jpxx
Elevation: 4,800 to 5,600 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Paoli and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Paoli
Setting
Landform: Stream terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium
Typical profile
H1 - 0 to 30 inches: fine sandy loam
H2 - 30 to 60 inches: fine sandy loam, sandy loam, loamy sand
H2 - 30 to 60 inches:
H2 - 30 to 60 inches:
Properties and qualities
Slope: 0 to 1 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Very low
Capacity of the most limiting layer to transmit water (Ksat): High (2.00 to 6.00
in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 15 percent
Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)
Available water storage in profile: Very high (about 16.5 inches)
Interpretive groups
Land capability classification (irrigated): 1
Land capability classification (nonirrigated): 3c
Hydrologic Soil Group: A
Ecological site: Overflow (R067BY036CO)
Hydric soil rating: No
Custom Soil Resource Report
13
Minor Components
Caruso
Percent of map unit: 6 percent
Hydric soil rating: No
Table mountain
Percent of map unit: 6 percent
Hydric soil rating: No
Fluvaquentic haplustolls
Percent of map unit: 3 percent
Landform: Terraces
Hydric soil rating: Yes
Custom Soil Resource Report
14
References
American Association of State Highway and Transportation Officials (AASHTO).
2004. Standard specifications for transportation materials and methods of sampling
and testing. 24th edition.
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes. ASTM Standard D2487-00.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife
Service FWS/OBS-79/31.
Federal Register. July 13, 1994. Changes in hydric soils of the United States.
Federal Register. September 18, 2002. Hydric soils of the United States.
Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric
soils in the United States.
National Research Council. 1995. Wetlands: Characteristics and boundaries.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service.
U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/national/soils/?cid=nrcs142p2_054262
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for
making and interpreting soil surveys. 2nd edition. Natural Resources Conservation
Service, U.S. Department of Agriculture Handbook 436. http://
www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577
Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of
Agriculture, Natural Resources Conservation Service. http://
www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580
Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control, Wetlands
Section.
United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of
Engineers wetlands delineation manual. Waterways Experiment Station Technical
Report Y-87-1.
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/
home/?cid=nrcs142p2_053374
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/landuse/rangepasture/?cid=stelprdb1043084
15
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/soils/scientists/?cid=nrcs142p2_054242
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States,
the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook
296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?
cid=nrcs142p2_053624
United States Department of Agriculture, Soil Conservation Service. 1961. Land
capability classification. U.S. Department of Agriculture Handbook 210. http://
www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf
Custom Soil Resource Report
16
ATTACHMENT G
Standard Operating Procedure (SOP)
Playground Surfacing
Routine Maintenance Table (Summary from Chapter 6 of UDFCD)
Required
Action Maintenance Objective Frequency of Action
Debris and Litter
Removal
Remove debris and litter from the
infiltrating surface to minimize
clogging of the media.
Routine – Including just before annual storm
seasons (April and May), end of storm
seasons after leaves have fallen (October),
and following significant rainfall events.
Sediment
Removal and
Media
Replacement
Maintain adequate infiltration rates
to drain the playground surfacing
within 24 hours. Upon replacement of
EWF and/or clogging is observed.
Inspection of the geotextile fabric
and drainage gravel below the EWF
should be performed. If either item is
preventing proper infiltration, it
should be replaced per design
specifications.
Non-Routine – Maintenance activities to
restore infiltration capacity of playground
surfacing will vary with the degree and
nature of the clogging. The frequency of
media replacement will depend on site-
specific characteristics that have the
potential to clog the playground surfacing
and drainage gravel.
Replacement of
Engineered
Wood Fiber
(EWF)
Maintain a level play surface with
raking of existing EWF and add
additional EWF as necessary to
achieve a level surface and proper
depths. Where playground
equipment is less than 4 feet in
height, the minimum EWF depth
required is 8 inches after compaction.
Where playground equipment
exceeds 4 feet in height, the
minimum EWF depth required is 12
inches after compaction
Non-Routine -As needed and inspect EWF
conditions at least twice annually following
precipitation events.
Inspections
Determine if the playground
surfacing area is providing acceptable
infiltration, and outlet structures are
not obstructed. Check for erosion
and repair as necessary.
Routine – Inspect the infiltrating surface at
least twice annually following precipitation
events. Check for obvious problems during
routine maintenance visits, especially for
plugging of outlets and erosion.
Bioretention/Bioswale
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.
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.