Prelim Drainage and Erosion ControlGolden Dragon
Preliminary
Drainage and Erosion
Control Report
Prepared for: South Bay Homes
115 McCormick Street NE
Olympia, WA 98506
(360} 943-1362
September 10, 2004
Prepared by: David W. Spitler
Reviewed by: Steven D. Hatton, PE
HATTON GODAT PANTIER
1840 Barnes Blvd SW
Tumwater, WA 98512
(360) 943-1599
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Project No: 04-014
Project Name: GOLDEN DRAGON
E:lofficelJOBS12004104-0141Drainage Report.doc
TABLE OF CONTENTS
I. THURSTON REGION FACILITY SUMMARY FORM .............................................................3
II. DRAINAGE REPORT ...............................................................................................................7
Section 1 -Project Description .................................................................................... ..7
Section 2 -Existing Conditions .................................................................................... ..7
Section 3 -Soils Report ............................................................................................... ..8
Section 4 -Wells and Septic Systems ......................................................................... ..8
Section 5 -Fuel Tanks ................................................................................................ ..8
Section 6 -Analysis of 100-Year Flood ....................................................................... ..8
Section 7 -Aesthetic Considerations .......................................................................... ..8
Section 8 -Facility Sizing and Downstream Analysis ................................................. ..9
Section 9 -Covenants, Dedications, and Easements ................................................. 13
Section 10 -Articles of Incorporation .......................................................................... 13
III. EROSION CONTROL PLAN ................................................................................................. 14
Section 1 -Construction Sequence ............................................................................. 14
Section 2 -Trapping Sediment .................................................................................... 14
Section 3 -Site Restoration ......................................................................................... 15
Section 4 - Geotechnical Analysis ............................................................................... 15
Section 5 -Inspection Sequence ................................................................................. 15
Section 6 -Control of Pollutants other than Sediments .............................................. 15
IV. STORMWATER MAINTENANCE PLAN .............................................................................. 16
Appendix A -Site Plan
Appendix B -Soils Information
Appendix C -Calculations
I. THURSTON REGION FACILITY SUMMARY FORM
Complete one for each facility (detention/retention, coalescing plate filter, etc.) on the project site. Attach
8'/z " by 11" sketch showing location of facility.
Proponent's facility name or identifier (e.g., Pond A): Infitration Pond
Name of road or street to access facility: Yelm Avenue
Hearings Examiner case number:
Development Review Project No. /Bldg. Permit No.:
Parcel Number(s):
21724130700
To Be Completed By Utility Staff:
Utility facility number:
Parcel number status, (num, 1 ch) ............................
0-Known; 1-Public; 2-Unknown; 3-Unassigned
Basin and sub-basin, (num, 6ch) ..............................
(2ch-Basin; 2ch-Sub-basin; 2ch-Future
Responsible jurisdiction, (alpha, 1ch) .......................
O-Olympia; C-County; T-Tumwater; L-Lacey
Part 1 -Project Name and Proponent
Project name:
Project owner:
Project contact:
Address:
Phone:
Project proponent (if different):
Address:
Phone:
Project engineer:
Firm:
Phone number:
Golden Dragon
Paul and Kathy Huynh
Same
3817 Pacific Avenue
Lacey, WA 98503
South Bay Homes
115 McCormick Street NE, Olympia, WA 98506
(360) 943-1362
Steven D. Hatton, PE
HATTON GODAT PANTIER
(360) 943-1599
(~(~~DE~~ DR~GC?N 09-10-04 P~\G~ 3
Part 2 -Project Location
Section
Township
Range ....
24
17N
1E
Names and addresses of adjacent property owners:
Part 3 -Type of Permit Application
Type of permit (e.g., commercial building):
Other permits (~):
^ DOF /W HPA
^ COE Wetlands
^ FEMA
^ Shoreline Management
^ Encroachment
® Other Building
^ COE 404
^ DOE Dam Safety
^ Floodplain
^ Rockery/Retaining Wall
® Grading
Other agencies (Federal, State, Local, etc.) that have or will review this Drainage and Erosion Control
Plan: NONE
Part 4 -Proposed Project Description
What stream basin is the project in (e.g., Percival, Woodland, etc.)?
Zoning :......................... Commercial C-1
On-site:
Residential Subdivision:
Number of lots ..........................................................
Lot size (average, acres) ..........................................
Building PermitlCommercial Plat:
Building(s) (footprint, acres) .....................................
Concrete paving (acres) ...........................................
Gravel surface (acres) ..............................................
Lattice block paving (acres) ......................................
Public roads-including gravel shoulder (acres) ........
Private roads-including gravel shoulder (acres) .......
On-site impervious surface total (acres) ....................
Part 5 -Pre-developed Proiect Site Characteristics:
Stream through site (y/n) ......................................NO
Name ............................................ NIA
DNR Type ..................................... NIA
Yelm
0.07
0.26
0.33
Type of feature this facility discharges to (i.e., lake, stream, intermittent stream, pothole, roadside ditch,
sheetflow to adjacent property, etc.):
TYPE OF DISCHARGE -Infiltration
Swales (y/n) ............................................................. N
Steep slopes-steeper than 10% (y/n) ...................... N
Erosion hazard (y/n) ................................................ N
100-year floodplain (y/n) .......................................... N
Wetlands (y/n) .......................................................... N
Seeps/springs (y/n) .................................................. N
High groundwater table (y/n) ................................... N
Other ...................................................................... N
G01..DEi~ C)(~~,(~C?iV 0~'-10-04 Pr"~GE 5
Part 6 -Facility Description
Total area tributary to facility including off-site (acres) .
Total on-site area tributary to facility (acres) ................
Design impervious area tributary to facility (acres).......
Design landscaped area tributary to facility (acres)......
Design total tributary area to facility (acres) .................
Enter "1"for type of facility:
Wet pond detention .................................................
Wet pond water surface area (acres) .....................
Dry pond detention .................................................
Underground detention ...........................................
Infiltration pond .......................................................
Drywell infiltration ....................................................
Coalescing plate separator .....................................
Centrifuge separator ...............................................
Other Description ..................................................
0.56
0.56
0.33
0.23
0.53
1
Outlet type (enter "1" for each type present):
Filter ......................
Oil/water separator
1
Single orifice ...........................................................
Multiple orifices .......................................................
Weir .........................................................................
Spillway ...................................................................
Pump(s) ..................................................................
Other Description ..................................................
Part 7 -Release to Groundwater
Design percolation rate to groundwater (if applicable)
Part 8 -Release to Surface Water (if applicable)
Thurston County MSL Percent Design
15 inches per hour
Discharge To Surface
Elevation (ft.) Full Volume (cu. ft.) Water cfs)
0 0.00 0.00
25
50
100
CC0I.DEP7 Dfid~,taC?IL~ t~9-90-UA f~~\G~ 6
11. DRAINAGE REPORT
Section 1 -Project Description
This proposal seeks approval to construct a 2,999 s.f. restaurant building with associated parking and
drive facilities on 1.62 acres. The site is located south of the intersection of Yelm Avenue (SR 507) and
Killion Road, parcel number 21724130700. The site is zoned commercial (C-1 ), which allows the use.
The project consists of onsite parking, drive, and a building with improvements to Yelm Avenue.
Stormwater improvements will be provided onsite for the project. City water and sewer service is
available at the site and are proposed to service the site. The project will require site plan approval,
grading and building permits.
Stormwater Best Management Practices will be provided for the project, including water quality, to treat
run-off via a bio-filtration swale. This facility will treat the 6-month event. Stormwater quantity runoff
impacts are mitigated by an on-site infiltration pond. The building runoff will be infiltrated in the infiltration
pond or in a drywell. These facilities will be designed to infiltrate the 100-year event. Appendix A
contains a reduced copy of the grading and drainage control. Approximately 1.06 acres of the site will
remain in an undeveloped condition. The undeveloped portion of the site will not drain to the proposed
storm facilities.
Desrrintion I Impervious Area (acl Total Area (ac)
Landscaping Area
Parking Lot and sidewalks
Roof Area
Sub-total (area draining to pond)
0.23
0.26 0.26
0.07 0.07
0.33 (59%) 0.56
Area to remain in natural 1.06
condition not drainin to and
Site total 0.33 1.62
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Section 2 -Existing Conditions
There is no significant offsite drainage tributary to the site. The undeveloped right-of-way located
northwest of the site is lower than the site and the parcel to the southwest, appears to be slightly lower
and drains to the South. Yelm Highway appears to drain to the southeast along the edge of pavement.
The site generally drains to the southwest at a maximum grade of 5%.
The site is located within an aquifer recharge area. There are no known creeks, lakes, ponds, wetlands,
gullies, steep slopes, spring, or other environmentally sensitive area on site or immediately down gradient
of the property.
Section 3 -Soils Report
The Thurston County Soil Survey identifies the soil on site as Spanaway Gravely Sandy Loam. This soil
group typically has a very gravelly sand approximately 20 inches below the surface. Based on the soil
description and the typical very fast infiltration rates; a design infiltration rate of 15 in/hr was selected for
the design. Copies of the soils survey and soil description are included in Appendix B.
Section 4 -Wells and Septic Systems
Records at Thurston County and the Department of Ecology were searched in order to locate wells and
septic systems that may be located within the setback distances from the stormwater pond or ponds. In
addition, the Project Engineer, or someone under his direct supervision, has visited the site to verify the
presence or absence of wells and septic systems as best can be done visually without trespassing onto
other properties. All wells and septic systems found to be located within the setback distances from the
stormwater pond or ponds have been shown on the plans.
Section 5 -Fuel Tanks
Records at Thurston County and the Department of Ecology were searched in order to locate the
presence of above and below ground fuel storage tanks that may be located within the setback distances
from the stormwater pond or ponds. In addition, the Project Engineer, or someone under his direct
supervision, has visited the site to verify the presence or absence of fuel tanks as best can be done
visually without trespassing onto other properties. All fuel tanks found to be located within the setback
distances from the stormwater pond or ponds have been shown on the plans.
Section 6-Analysis of 100-Year Flood
The Federal Emergency Management Agency prepares maps for all areas within Thurston County,
including the incorporated cities therein. Panel # 50310-0001 A depicts the areas, if any, subjected to
flooding in the vicinity of this proposal. By inspection of this map, this proposal appears to be located in
Zone X, an area determined to be outside the 500-year flood plain.
Section 7 -Aesthetic Considerations
All stormwater facilities will be hydroseeded upon completion. In addition, the water quality wet pond will
be planted with a variety of wetland species both in the permanent pool and along the fringes of the
permanent water surface. Additional landscaping shall also be provided throughout the project in
conformance with the approved landscaping and tree restoration plan, as applicable, and as otherwise
required by the approving authority.
GCJL(7EN DFtA a4iv OS-10-04 {'ACHE F3
Section 8 -Facility Sizing and Downstream Analysis
This project has been designed per the requirements of the Stormwater Management Manual for the
Puget Sound Basin published in 1992 that has been developed by the Washington State Department of
Ecology. The stormwater conveyance system and drainage control features have been analyzed using
the HYDRA computer modeling software that utilizes the SCS SBUH method. A copy of the HYDRA
model is located in Appendix C.
Retention Pond Sizing
The retention pond has been sized to infiltrate the volume of a 100-year, 24-hour storm event.
The pond infiltration rate is as follows:
Design infiltration rate = 15 inches per hour.
The pond bottom area is 10 x 20 = 200 square feet.
Qouc = 15 in x 1 ft x _1 hr x 200 sq. ft.
1 hr 12 in 3,600 sec
Qo~t = 0.07 cfs
Stage/discharge relation of the retention pond can be found in Appendix C.
The HYDRA model indicates that the peak storage volume required is 1,476 cubic feet fora 100-year, 24-
hourstorm event. This volume is achieved at a Design Water Level (DWL) of 343. The total available
storage volume in the pond is 3,793, cubic feet at a DWL of 344.0. The design provides a factor of safety
of 8.6 for the infiltration pond volume. Additional stormwater storage volume is available above the top of
the pond. The building pad is at elevation 351, approximately 7 feet above the top of the pond. Overflow
spillway or downstream analyses are not practical for this pond due to the large safety factors.
Bio-Filtration Swale Sizing
Design based on Appendix A 111-6.1 of the DOE -Stormwater Management Manual for the Puget Sound
Basin.
Preliminary Steps (P)
Step #
P-1) Estimate the runoff flow rate (Q) for the 6-month frequency, 24-hour duration storm, according to
methods outlined in Chapter III-1.
The Hydra analysis estimated the 6-month and 100-year 24-hour flow rate to be 0.10
P-2) Bio-filtration Swales should be designed to have slopes between 2 and 4%. Refer to Manual if
stepper or flatter slopes are required. Select a slope based on preliminary layout.
The swales will be designed to have 2% slopes.
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P-3) Select a vegetation cover suitable for the site. Refer to table III-6.1 to select grass.
The swales will be a drought tolerant western wheatgrass mixture.
Design Steps (D)
Step #
D-1) Establish the height of vegetation during the winter and the design depth of flow. The design
depth should be at least 2-inches less than the winter vegetation height.
The area will likely be mowed on a regular basis. Therefore, set the winter grass height
at least 6-inches and the flow depth to 2 inches.
D-2) Select a value of Manning's n from Table III-2.8 of the Manual.
Use n = 0.07; for dense grass up to 6-inches high.
D-3) Select the swale shape.
Use a trapezoidal shape.
D-4) Use Manning's equation and first approximations relating hydraulic radius and dimensions for the
selected shape to obtain a working value of abio-filter width dimension:
For a trapezoidal section.
b = Qn/(1.486 * y^1.667 " s^0.5) - zy
Note due to the small flows the -zy has been deleted to give positive widths. For all
swales y = 4 inches, s = 0.02, n = 0.07, and z =3. b= 0.39 ft
Use 0.5 feet for the swale, to make construction easier.
D-5) Calculate the area of the cross section.
Area = by +zy^2 = 0.5*0.33 +3"0.33^2 = 0.49 SF
D-6) Compute the flow Velocity at design flow. This Velocity should be less than 1.5 ft/sec
V = Q/A = 0.10 cfs/0.49 SF = 0.20 ft/s
Velocity is less than 1.5 ft/s; design meets criteria
Stability Check Steps (SC)
SC-1) Unless runoff from events larger than the 6-month, 24-hour storm will bypass the bio-filter,
perform the stability check for the 100-year, 24 hour storm. Estimate Q for the 100-year event.
Q100 = 0.45 cfs
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SC-2) Estimate the vegetation coverage ("good" or "fair") and height on the first occasion that the bio-
filterwill receive flow, or whenever the coverage and height will be least.
The area will not be irrigated, therefore assume fair coverage.
SC-3) Estimate the degree of retardance form Table III-6.2 of the Manual.
D -Low.
SC-4) Establish the maximum permissible velocity for erosion prevention (Vmax) from Table III-6.3.
4 ft/sec for western wheatgrass.
SC-5) Select a trail Manning's n.
n = 0.041
SC-6) Refer to figure III-6.6 to obtain a first approximation for VR.
VR = 2.8
SC-7) Compute hydraulic radius, using the Vmax from step SC-4
R = VR/Vmax = 0.75/4 = 0.70
SC-8) Use Manning's equation to solve for the actual VR:
VR = 1.486/n R1.667 s0.5
_ (1.486/0.042) 0.701.667 0.020.5
= 2.8
SC-9) Compare the actual VR from step SC-8 and the first approximation from step SC-6. If they do not
agree within 5 percent, repeat steps SC-5 to SC-9 until acceptable agreement is reached.
2.8 = 2.8, proceed to stem SC-10
SC-10) Compute the actual V for the final design conditions; Check to be sure V < Vmax from step SC-4:
V=VR/V=2.8/0.70=4.0
SC-11) Compute the required A for Stability.
A=Q/V=0.45cfs/4.Of/s=0.11 sf
SC-12) Compare the Area computed in step SC-11 of the stability analysis, with the Area from the bio-
filtration capacity analysis (step D-5). If less area is required for stability than is provided for
capacity, the capacity design is acceptable. If not, use A from step SC-11 of the figure III-6.5 and
recalculate channel dimensions.
Use y from step D-1.
\.:Y l,_~L~~L.i `i t.~i \J'1 ~~.J~d~ .. UJ~'~O'V'~t (~~1,7~ ~~
Step D-5 required an Area of 0.49 sf, which is larger than the areas calculated in Step SC-11. Use the
dimensions developed in the design steps.
z=3
y = 0.33 ft
b = 0.50 ft
Area = 0.49 sf
T=b+2yz=2.48
SC-13) Calculate the depth of flow at the stability; y = (T-b)/2z for trapezoids.
y = (2.48-0.5)/(2*3) = 0.33
SC-14) Compare the depth form step SC-13 to the depth used in the bio-filtration capacity design (step
D-1 ). Use the larger and add 1-foot freeboard to obtain total required depth (yt).
The depth is the same. Remember the base was increase to 0.5 for all swales in step D-
4. The actual flow depths will not be the same for the treatment and 100-year events.
Set yt equal to 1 + 0.33 = 1.33 ft
SC-15) Recalculate the hydraulic radius; R = (byt + zyt2) / (b + 2yt(z2 + 1)0.5
R = [(0.5*1.33) + (3*1.332)] / [0.5 + (2*1.33''(32 + 1)0.5)
= 5.97 / 8.91
= 0.67
SC-16) Make a final check for capacity based on the stability based on the stability check design storm
and maximum vegetation height and cover, using the Manning's Equation. Use a Manning's n =
0.1, A = byt + zyt2 using b from step D-4a or D-15 or SC-12, as appropriate.
Q = (1.486/0.1) (0.49) (0.67)0.667 (0.02)0.5
= 0.78 cfs
This is greater than the 100-year flow rate.
Completion Steps (COQ
CO-1) If the bio-filter is a swale, lay out the swale to obtain the maximum possible length. If a shorter
than 200-foot swale must be used, increase A by an amount proportional to the reduction in the
length below 200 feet.
Due to limited area, the length must be reduced to 100-feet.
Revise the Area = (200/100) * 0.49 = 0.98 sf
Calculate the revised swale dimensions.
_ [0.98-(3*0.332)] / 0.33
= 1.97 ft
For construction reasons, the swales will be constructed with a 4-foot wide base.
GOLf3EFv C?f~~,~4N 09-1C~-0~ r'~aG~ 12
CO-2) If the swale longitudinal slope is greater than 4 percent, design log or rock check dams
approximately every 50 feet.
The slopes are all less than 4 percent.
Section 9 -Covenants, Dedications, and Easements
All stormwater facilities located on private property shall be owned, operated, and maintained by the
property owners, their heirs, successors, and assigns. The property owners shall enter into an
agreement with the governing body, a copy of which is included in Part V of this report. The agreement
requires maintenance of the stormwater facilities in accordance with the maintenance plan provided and
shall grant easement for access to the governing body to inspect the stormwater facilities. The
agreement also makes provisions for the governing body to make repairs, after due notice is given to the
owners, if repairs are necessary to ensure proper performance of the stormwater system and if the
owners fail to make the necessary repairs. The cost of said repairs shall be borne by the property
owners, their heirs, successors, and assigns.
Section 10 -Articles of Incorporation
Not applicable.
--
GOLf~EN [~Rfi,GC)P: 09-1~7-04 PACaia 1,~
III. EROSION CONTROL PLAN
Section 1 -Construction Sequence
Prior to commencing any grading or filling upon the site, all erosion control measures, including
installation of a stabilized construction entrance, shall be installed in accordance with this plan and the
details shown on the drawings. More specifically, the following construction sequence shall be observed:
1. Construction on this site shall be conducted substantially in accordance with the construction
sequence described on the plans and in this erosion control plan. Deviations from this
sequence shall be submitted to the project engineer and permitting jurisdiction. Deviations
must be approved prior to any site disturbing activity not contained within these plans.
2. For each phase of the development of this site, the following general sequence shall be
observed:
a. Install perimeter filter fabric fence as shown.
b. Install inlet protection for existing inlets in the vicinity of areas to be disturbed.
c. Call for inspection by the project engineer.
d. Construct temporary sedimentation trap(s) and outlet(s).
e. Perform grading directing site runoff towards the sediment trap prior to discharge
from the site.
f. Install temporary piping, as required, to direct runoff towards the sediment trap.
3. Once the site is disturbed, continue operations diligently toward completion.
4. Monitor all erosion control facilities, and repair, modify, or enhance as directed or as required.
Section 2 -Trapping Sediment
Protection of off-site properties against sedimentation is an absolute necessity. Additional measures may
be required to provide full protection of downstream areas. Additional measures may include, but are not
limited to, use of sediment bags in existing catch basins, increased filters within sediment ponds such as
hay bales, introduction of coagulants to the sediment ponds, and other such measures. Continuous
monitoring of the erosion control systems, depending upon site and weather conditions, shall be ongoing
throughout project development.
Vehicle tracking of mud off-site shall be avoided. Installation of a stabilized construction entrance shall be
installed at the start of construction at the exit point to be used by equipment. This entrance is a
minimum requirement and may be supplemented if tracking of mud onto public rights-of-way becomes
excessive. Washing down roads daily to remove excessive mud may be required. Wash water shall be
directed to the temporary sediment traps installed on-site and shall not be allowed to discharge
downstream without treatment.
GtaLDEN C)~t~G4fV O~J-1U-C}4 P~G~ 14
Section 3 -Site Restoration
Disturbed areas on and off-site shall be hydroseeded or otherwise landscaped or stabilized upon project
completion to provide permanent erosion control where required. Erosion control measures shall remain
in place until final site stabilization is imminent (e.g., paving scheduled with a favorable weather forecast).
Section 4 - Geotechnical Analysis
Existing slopes in the area of the stormwater ponds are at a maximum of 3%. The temporary sediment
ponds will be excavated into the native soil. No embankment is required.
Section 5 -Inspection Sequence
The Project Engineer, or someone under his direct supervision, and the permit authority shall inspect the
temporary erosion control facilities (construction entrance, sediment traps, and erosion control barriers)
prior to commencement of construction. During and following construction, the Engineer shall inspect the
construction of the permanent stormwater facilities and report to the permit authority his findings as to
performance and operability of the completed system.
Section 6 -Control of Pollutants other than Sediments
A centralized equipment marshalling area and containment area is to be provided on-site for equipment
maintenance and storage of any equipment service materials. An area on-site will be selected as a
temporary debris and stockpile area for materials that will be removed from the site. Erosion control
containment and berming of this area will be provided for pollutant containment and sheeting provided for
coverage or lining if applicable.
GCaLC)Eiti DFiAGOt~ 09-10-04 PAGc '!5
IV. STORMWATER MAINTENANCE PLAN
Golden Dragon
September 10, 2004
GC7L[}E~i Df2AGrJN (?5-10-04 WAGE 16
TABLE OF CONTENTS
I. STORMWATER FACILITY MAINTENANCE GUIDE ........................................................................ 18
INTRODUCTION ............................................................................................................................ 18
What is Stormwater Runoff? ..................................................................................................... 18
What is a Storm Drain System and how does it Work? ............................................................ 18
What does Stormwater Runoff have to do with Water Quality? ................................................ 18
Your Stormwater Facility ........................................................................................................... 18
Who is Responsible for Maintaining Stormwater Facilities? ..................................................... 18
How to Use the Stormwater Facility Maintenance Guide .......................................................... 19
Included in This Guide .............................................................................................................. 19
A Regional Approach to Stormwater Management ................................................................... 19
YOUR STORMWATER FACILITIES .............................................................................................. 19
FACILITY KEY ................................................................................................................................ 19
SITE PLAN ..................................................................................................................................... 20
QUICK LIST .................................................................................................................................... 21
MAINTENANCE CHECKLISTS ...................................................................................................... 22
Ponds ........................................................................................................................................ 23
Catch Basins, Manholes, and Inlets .......................................................................................... 24
Conveyance Pipes, Ditches, and Swales ................................................................................. 25
Grounds and Landscaping ........................................................................................................ 26
RESOURCE LISTING .................................................................................................................... 27
II. POLLUTION SOURCE CONTROL PROGRAM ................................................................................ 29
What Are Pollution Source Controls And Why Are They Needed? .......................................... 29
Materials Used And Wastes Generated .................................................................................... 29
Required Actions ....................................................................................................................... 29
II. STORMWATER FACILITY MAINTENANCE GUIDE
INTRODUCTION
What is Stormwater Runoff?
When urban and suburban development covers the land with buildings, streets and parking lots, much of
the native topsoil, duff, trees, shrubs and grass are replaced by asphalt and concrete. Rainfall that would
have soaked directly into the ground instead stays on the surface as stormwater runoff making its way
into storm drains (including man-made pipes, ditches, or swale networks), stormwater ponds, surface and
groundwater, and eventually to Puget Sound.
What is a Storm Drain System and how does it Work?
The storm drain system for most developments includes measures to carry, store, cleanse, and release
the stormwater. Components work together to reduce the impacts of development on the environment.
Impacts can include flooding which results in property damage and blocked emergency routes, erosion
which can cause damage to salmon spawning habitat, and pollution which harms fish and/or drinking
water supplies.
The storm drain system provides a safe method to carry stormwater to the treatment and storage area.
Swales and ponds filter pollutants from the stormwater by physically settling out particles, chemically
binding pollutants to pond sediments, and biologically converting pollutants to less harmful compounds.
Ponds also store treated water, releasing it gradually to a nearby stream or to groundwater.
What does Stormwater Runoff have to do with Water Quality?
Stormwater runoff must be treated because it carries litter, oil, gasoline, fertilizers, pesticides, pet wastes,
sediments, and anything else that can float, dissolve or be swept along by moving water. Left untreated,
polluted stormwater can reach nearby waterways where it can harm and even kill aquatic life. It can also
pollute groundwater to the extent that it requires treatment before it is suitable for drinking. Nationally,
stormwater is recognized as a major threat to water quality. Remember to keep everything out of
stormwater systems except the rainwater they are designed to collect.
Your Stormwater Facility
Different types of ponds are designed for different purposes. For example, wet ponds primarily provide
treatment of stormwater. Dry ponds or infiltration ponds are designed to provide storage for stormwater
and allow for its gradual release downstream or into the ground.
Who is Responsible for Maintaining Stormwater Facilities?
All stormwater facilities require maintenance. Regular maintenance ensures proper functioning and
preserves visual appeal. This Stormwater Facility Maintenance Guide was designed to explain how
stormwater facilities work and provide user-friendly, straightforward guidance on facility maintenance.
You are responsible for regularly maintaining privately owned ponds, catch basins, pipes and other
drainage facilities on your property. Stormwater facilities located in public rights-of-way are maintained by
local governments.
How to Use the Stormwater Facility Maintenance Guide
This Maintenance Guide includes a Site Plan specific to your development and a Facility Key that
identifies the private stormwater facilities you are responsible for maintaining. A "Quick List" of
maintenance activities has also been included to help you identify the more routine needs of your facility.
Included in This Guide
^ Comprehensive Maintenance Checklists that provide specific details on required maintenance
^ Pollution Prevention Tips that list ways to protect water quality and keep storm drain systems
functioning smoothly
^ Resources to provide more information and technical assistance
A Regional Approach to Stormwater Management
The Cities of Lacey, Olympia and Tumwater together with Thurston County are taking steps to educate
and involve area residents in water quality issues and stormwater management. Stormwater runoff is a
widespread cause of water quality impairment and stream degradation. The jurisdictions are working
together with residents, businesses, community groups and schools to address this problem. This guide
focuses on providing information on ways that you can reduce stormwater impacts through pollution
prevention and proper facility maintenance.
YOUR STORMWATER FACILITIES
This section consists of two parts that are to be used together: the Facility Key and the Site Plan.
Review the site plan and identify the numbers denoting a feature of the system. Then check the facility
key for the feature type and checklist name.
FACILITY KEY
The stormwater facility in your neighborhood is comprised of the following elements:
Type of Feature & Checklist Name Location on Site Plan
Ponds 2
Catch Basins, Manholes, and Inlets 3
Conveyance Pipes, Ditches, and Swales 6
Grounds and Landscaping 7
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GOLDEN DRAGON
PRELIM/NARY SITE PLAN
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REVISIONS: DATE:
PA N T I E R DESIGNED BY: SDH
HATTON F-.~~ ~ ~:_ "„ x ~ sr
v ~ Sr~rfC~`~ DRAWN BY.• MM
ENGINEERS AND SURVEYORS uAmi o~ Q. Z CHECKED BY.~ SDH
1840 BARNES BOULEVARD S W = ~ `~ a i~ O
TUMWATER, WA 98512 N ~a ,~+ GATE oH2oa
TEL: 360.943.1599 FAX: 360.357.6299 i ~ 'pt'~~ SCALE: H t~m•
hattonpantfBr.com ~' ~ NO~'y Y
APPENDIX B -Soil Information
158
Spanaway Series
The Spanaway series consists of very deep,
somewhat excessively drained soils on terraces. These
soils formed in glacial outwash and volcanic ash. Slope
is 0 to 15 percent. Elevation is 100 to 400 feet. The
average annual precipitation is 40 to 55 inches, the
average annual air temperature is about 51 degrees F,
and the average frost-free season is 150 to 200 days.
These soils are sandy-skeletal, mixed, mesic Andic
Xerumbrepts.
Typical pedon of Spanaway gravelly sandy loam, 0 to
3 percent slopes. 4 miles southeast of Lacey; about 250
feet west and 400 feet south of the northeast corner of
sec. 25, T. 36 N., R. 1 W.
A-0 to 15 inches; black (10YR 2/1) gravelly sandy
loam, very dark grayish brown (10YR 3/2) dry; weak
fine granular structure; loose, very friable, nonsticky
and nonplastic; many fine, medium, and coarse
roots; 25 percent pebbles; strongly acid; clear
smooth boundary.
Bw-15 to 20 inches; dark yellowish brown (10YR 3/4)
very gravelly sandy loam, light olive brown (2.5Y
5/4) dry; weak fine subangular blocky structure;
loose, very friable, nonsticky and nonplastic; many
fine, medium, and coarse roots; 55 percent pebbles;
medium acid; clear smooth boundary.
C-20 to 60 inches; dark yellowish brown (10YR 4/4)
extremely gravelly sand, yellowish brown (10YR
5/4) dry; single grained; loose; few fine roots; 80
percent pebbles, 10 percent cobbles; slightly acid.
The thickness of the solum ranges from 15 to 25
inches. The content of coarse fragments in the control
section ranges from 50 to 85 percent. The weighted
average texture of this section is very gravelly sand or
extremely gravelly sand. The umbric epipedon is 10 to
20 inches thick.
The A horizon has hue of 10YR or 7.5YR, value of 3
or 4 when dry, and chroma of 1 or 2 when moist or dry
It is medium acid or strongly acid. The Bw horizon has
value of 4 or 5 when dry and 3 or 4 when moist. It is
very gravelly sandy loam, very gravelly loam, or
extremely gravelly sandy loam. The C horizon has hue
of 10YR or 2.5Y, value of 5 or 6 when dry and 4 or 5
when moist, and chroma of 3 or 4 when dry or moist. It
is extremely gravelly sand or extremely gravelly loamy
sand and is slightly acid or neutral.
Sultan Series
The Sultan series consists of very deep, moderately
Soil Survey
well drained soils on flood plains. These soils formed in
alluvium. Slope is 0 to 3 percent. Elevation is 20 to 75
feet. The average annual precipitation is 40 to 50
inches, the average annual air temperature is about 50
degrees F, and the average frost-free season is 150 to
200 days.
These soils are fine-silty, mixed, nonacid, mesic
Aquic Xerofluvents.
Typical pedon of Sultan silt loam, 7 miles east of
Lacey; about 1,000 feet east and 1,975 feet north of the
southwest corner of sec. 16, T. 18 N., R. 1 E.
Ap-0 to 7 inches; dark yellowish brown (10YR 3/4) silt
loam, brown (10YR 5/3) dry; moderate fine and
medium granular structure; slightly hard, very
friable, slightly sticky and slightly plastic; many fine,
medium, and coarse roots; many very fine and fine
tubular pores; slightly acid; abrupt smooth
boundary.
BA-7 to 20 inches; dark yellowish brown (10YR 4/4)
silt loam, brown (10YR 5/3) dry; moderate fine and
medium subangular blocky structure; slightly hard,
very friable, slightly sticky and slightly plastic; many
very fine, fine, and medium roots; many very fine
and fine tubular pores; slightly acid; clear wavy
boundary.
Bwi-20 to 25 inches; dark brown (10YR 3/3) silt loam,
grayish brown (2.5Y 5/2) dry; common fine
prominent red (2.5YR 5/8) mottles; moderate fine
and medium subangular blocky structure; slightly
hard, very friable, slightly sticky and slightly plastic;
common fine and medium roots; common very fine
and fine tubular pores; slightly acid; gradual wavy
boundary.
Bw2-25 to 45 inches; dark brown (10YR 4/3) silt loam,
light brownish gray (10YR 6/2) dry; common
medium prominent red (2.5YR 5/8) mottles;
moderate medium and coarse subangular blocky
structure; slightly hard, very friable, slightly sticky
and slightly plastic; few very fine and fine roots; few
very fine and fine tubular pores; slightly acid;
gradual wavy boundary.
C-45 to 60 inches; grayish brown (10YR 5/2) silt loam,
light gray (10YR 7/2) dry; common medium
prominent dark brown (7.5YR 4/4) mottles; massive;
slightly hard, very friable, slightly sticky and slightly
plastic; slightly acid.
The soils are slightly acid or neutral in the control
section and range from slightly acid to strongly acid
below a depth of 40 inches. Mottles that have chroma
of 3 or more are at a depth of more than 20 inches.
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APPENDIX C -Calculations
HGPA # 01-098
09/14/2004
Trapezoidal Sasin
Length
side slope 1
side slope 2
Top of Pond
Base elevation
Infiltration Rate
Flow out of base
Step
20 ft Width 10 ft
3 side slope 1 3
3 side slope 2 3
4
340.00 ft
15.00 ii~/hr
0.07 cfs
0.5
Elevation Volume
340.00 0
340.50 124
341.00 301
341.50 541
342.00 853
342.50 1,244
343.00 1,725
343.50 2,304
344.00 2,991
344.50 3,793
345.00 4,721
100-yr 24-1u' volume 1,476 CF
Status of DEFAULTS at start of run. ( * May be reset by SET)
Command file C:\HYDRA\CMD\04-014T.CMD
Input units are read as USA
* Output sent to display Brief
* Output sent to printer Brief
* Output sent to file Detailed
Paper width in inches 8.000
String to reset printer 27 51 36 18
String to set printer to compressed 17 15
String to set printer to 8 lines/inch 8 27 51 27
Name of printer Epson, FX series
Print heading at top of page False
Number of steps in hydrograph 144
Step length in minutes 10
Significant flow in hydrograph 0.010
* Maximum plot value Selected by HYDRA
Type of hydrographic plot Compact
Sanitary flow by Peaking Factor
Delay to start of actual storm 0.00
Rational Method computations Off
SCS computations Santa Barbara
Continuous simulation computations Off
* Maximum d/D for pipe design/analysis 0.900
* Match point position on pipe 0.00 or Invert
* Number of allowable diam drops 999
* Mimimum drop thru manhole 0.000
Routing technique Quick
~* Calculate sanitary flows True
* Calculate infiltration flows True
* Calculate storm flows True
* Calculate mist flows True
1: JOB Golden Dragon 100-year
2: REM Size the swale for stormwater treatment
3:
4:
5: TOT 4.00 sets the total rainfail
6: REM 6-month 1.33 in
7: REM 100-year 4.00 in
8:
9: FIL doe.inc "calls the doe unit hydrograph
------START OF SUB-FILE------
1: HYE 10 0.00 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.0
40+
2: 0.050 0.050 0.050 0.050 0.050 0.050 0.060 0.060 0.060 0.060 0.060
0.060+
3: 0.070 0.070 0.070 0.070 0.070 0.070 0.082 0.082 0.082 0.082 0.082
0.082+
4: 0.095 0.095 0.095 0.095 0.095 0.095 0.134 0.134 0.134 0.180 0.180
0.340+
5: 0.540 0.270 0.180 0.134 0.134 0.134 0.088 0.088 0.088 0.088 0.088
0.088+
6: 0.088 0.088 0.088 0.088 0.088 0.088 0.072 0.072 0.072 0.072 0.072
0.072+
7: 0.072 0.072 0.072 0.072 0.072 0.072 0.057 0.057 0.057 0.057 0.057
0.057+
8: 0.057 0.057 0.057 0.057 0.057 0.057 0.050 0.050 0.050 0.050 0.050
0.050+
9: 0.050 0.050 0.050 0.050 0.050 0.050 0.040 0.040 0.040 0.040 0.040
0.040+
10: 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040
0.040+
11: 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040
0.040+
12: 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040
0.040+
13: 0.040 0.040
------ END OF SUB-FILE ------
10.
11: PDA 0.012 8 1 2 2 0.005 ~ sets default pipe values
12: NEW Parking lot and landscaping area
13: SCS 0.49 0.53 98 80 2
14: PIP 1 347 347 "dummy pipe to print flow rate in Swale
NOTE: No flow to inlet.
15: HOL parking
16:
17: NEW Roof Area
18: SCS 0.07 1.00 98 90 2
19: PIP 100 347 347
NOTE: No flow to inlet.
20: REC parking
21: RES -1 0/.07 100000/.07
22:
23: END
------ S U M M A R Y O F A N A L Y S I S------
Run number on command file 15
Number of links 3
Number of hydrographs 39
Total sanitary population 0
Total sanitary area 0.00 Acres
Total storm area 0.56 Acres
Number of pumps 0
Number of reservoirs 1
Number of diversion structures 0
Number of inlets 0
Length of new pipe 101.00 Feet
Length of existing pipe 0.00 Feet
Length of channel 0.00 Feet
Length of gutter 0.00 Feet
Length of transport units 0.00 Feet
Length of pressure pipe 0.00 Feet
HGA, Consulting Engineers HYDRA Version 4.59
Olympia, Washington Page 1
---------------------------------------- -
C:\HYDRA\CMD\04-014T.CMD 17:40 14-Sep-104
Golden Dragon 100-year
*** Parking lot and landscaping
Invert
Link Long Diam Up/Dn Slope
1 1 8 344.28 0.0050
344.27
Lateral length=
~ area
Depth Min
Up/Dn Cover
2.72 2.00
2.73
1 Up
Pipe Design
San Sto Vel Design Estimated
Inf Mis d/D CFS Cost
0.0 0.5 2.24 0.45 0
0.0 0.0 0.55
----------------------
stream length= 1
*** Roof Area Pipe Design
Invert Depth Min San Sto Vel Design Estimated
Link Long Diam Up/Dn Slope Up/Dn Cover Inf Mis d/D CFS Cost
2 100 8 344.28 0.0050 2.72 2.00 0.0 0.1 1.40 0.08 0
343.78 3.22 0.0 0.0 0.24
*** Roof Area Reservoir
Invert -------------- Maximum Flow Values -----------------
Link Up/Dn San Inf Sto Mis Design Cost
3 343.78 Discharge 0.00 0.00 0.07 0.00 0. ~ 0
342.78 Stored 0 0 1476 0 1476
Incoming 0.00 0.00 0.53 0.00
Lateral length= 100 Upstream length= 10
Status of DEFAULTS at start of run. ( * May be reset by SET)
Command file C:\HYDRA\CMD\04-014T.CMD
Input units are read as USA
* Output sent to display Brief
* Output sent to printer Brief
* Output sent to file Detailed
Paper width in inches 8.000
String to reset printer 27 51 36 18
String to set printer to compressed 17 15
String to set printer to 8 lines/inch 8 27 51 27
Name of printer Epson, FX series
Print heading at top of page False
Number of steps in hydrograph 144
Step length in minutes 10
Significant flow in hydrograph 0.010
* Maximum plot value Selected by HYDRA
Type of hydrographic plot Compact
Sanitary flow by Peaking Factor
Delay to start of actual storm 0.00
Rational Method computations Off
SCS computations Santa Barbara
Continuous simulation computations Off
* Maximum d/D for pipe design/analysis 0.900
* Match point position on pipe 0.00 or Invert
* Number of allowable diam drops 999
* Mimimum drop thru manhole 0.000
Routing technique Quick
'* Calculate sanitary flows True
* Calculate infiltration flows True
* Calculate storm flows True
* Calculate misc flows True
1: JOB Golden Dragon 6-Month
2: REM Size the swale for stormwater treatment
3:
4:
5: TOT 1.33 "' sets the total rainfail
6: REM 6-month 1.33 in
7: REM 100-year 4.00 in
8:
9: FIL doe.inc "'calls the doe unit hydrograph
------START OF SUB-FILE------
1: HYE 10 0.00 -0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.0
40+
2: 0.050 0.050 0.050 0.050 0.050 0.050 0.060 0.060 0.060 0.060 0.060
0.060+
3: 0.070 0.070 0.070 0.070 0.070 0.070 0.082 0.082 0.082 0.082 0.082
0.082+
4: 0.095 0.095 0.095 0.095 0.095 0.095 0.134 0.134 0.134 0.180 0.180
0.340+
5: 0.540 0.270 0.180 0.134 0.134 0.134 0.088 0.088 0.088 0.088 0.088
0.088+
6: 0.088 0.088 0.088 0.088 0.088 0.088 0.072 0.072 0.072 0.072 0.072
0.072+
7: 0.072 0.072 0.072 0.072 0.072 0.072 0.057 0.057 0.057 0.057 0.057
0.057+
8: 0.057 0.057 0.057 0.057 0.057 0.057 O.D50 0.050 0.050 0.050 0.050
0.050+
9: 0.050 0.050 0.050 0.050 0.050 0.050 0.040 0.040 0.040 0.040 0.040
0.040+
10: 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040
0.040+
11: 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040
0.040+
12: 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040
0.040+
13: 0.040 0.040
------ END OF SUB-FILE ------
10.
11: PDA 0.012 8 1 2 2 0.005 ~ sets default pipe values
12: NEW Parking lot and landscaping area
13: SCS 0.49 0.53 98 80 2
14: PIP 1 347 347 "dummy pipe to print flow rate in swale
NOTE: No flow to inlet.
15: HOL parking
16.
17: NEW Roof Area
18: SCS 0.07 1.00 98 90 2
19: PIP 100 347 347
NOTE: No flow to inlet.
20: REC parking
21: RES -1 0/.07 100000/.07
22:
23: END
------ S U M M A R Y O F A N A L Y S I S------
Run number on command file 16
Number of links 3
Number of hydrographs 39
Total sanitary population 0
Total sanitary area 0.00 Acres
Total storm area 0.56 Acres
Number of pumps 0
Number of reservoirs 1
Number of diversion structures 0
Number of inlets 0
Length of new pipe 101.00 Feet
Length of existing pipe 0.00 Feet
Length of channel 0.00 Feet
Length of gutter 0.00 Feet
Length of transport units 0.00 Feet
Length of pressure pipe 0.00 Feet
HGA, Consulting Engineers HYDRA Version 4.59
Olympia, Washington Page 1
___________________
C:\HYDRA\CMD\04-414T CMD 17:43 14-Sep-104
Golden Dragon 6-Month
*** Parking lot and landscaping area
Pipe Design
Invert Depth Min San Sto Vel Design Estimated
Link Long Diam Up/Dn Slope Up/Dn Cover Inf Mis d/D CFS Cost
1 1 8 344.28 0.0050 2.72 2.00 0.0 0.1 1.44 0.10 0
---- 344.27
--------
------ 2.73
-------
------- 0.0
----- 0.0
------ 0.25
---- ----
Late ral length= 1 Upstream length= 1
*** Roof Area ~o~ Pipe Design
Invert Depth Min San Sto Vel Design Estimated
Link Long Diam Up/Dn Slope Up/Dn Cover Inf Mis d/D CFS Cost
2 100 8 344.28 0.0050 2.72 2.00 0.0 0.0 1.03 0.03 0
343.78 3.22 0.0 0.0 0.14
*** Roof Area
Reservoir
Invert -------------- Maximum Flow Values ------------ -----
Link Up/Dn San Inf Sto Mis Design Cost
3 343.78 Discharge 0.00 0.00 0.07 0.00 0.07 0
342.78 Stored 0 0 44 0 44
Incoming 0.00 0.00 0.12 0.00
---- 0.12
---
----------------
Lateral length= --------
100 ---------------------
Upstream length= 101
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QUICK LIST
The following is an abbreviated checklist of the most common types of maintenance required. Please go
over this checklist after heavy rains. The list represents minimum maintenance to be performed and
should be completed in conjunction with the other checklists for an effective maintenance program.
^ Inspect catch basin grates to see that they are not clogged or broken. Remove twigs, leaves, or
other blockages. Contact the local jurisdiction to replace the grate if it is broken.
^ Inspect inlet and outlet pipes for blockages. Clear all blockages.
^ Inspect filter strip, swale and pond walls for erosion or caved in areas.
^ Inspect riprap (rocks) at the inlets and outlets of culverts and other pipes. If they are silted in or
eroded away, replace them.
MAINTENANCE CHECKLISTS
The Maintenance Checklists in this packet are for your use when inspecting the stormwater facilities on
your property. This packet has been customized so that only the checklists for your facilities are included.
If you feel you are missing a checklist, or you have additional facilities not identified or addressed in this
packet, please contact your local jurisdiction.
The checklists are in tabular format for ease of use. Each describes the area to inspect, inspection
frequency, what to look for, and what action to take. A log sheet is included toward the end of the chapter
to help you track maintenance of your storm drainage system.
Although it is not intended for the maintenance survey to involve anything too difficult or strenuous, there
are a few tools that will make the job easier and safer including:
^ A flashlight.
^ Along pole or broom handle.
^ Some kind of pry bar or lifting tool for pulling manhole and grate covers.
^ Gloves.
A resource list is included in the next chapter. Here you will find the phone numbers of the agencies
referred to in the tables, as well as the contractors and consultants who designed and constructed your
facilities.
SAFETY WARNING: In keeping with OSHA regulations, you should never stick your head or any part of
your body into a manhole or other type of confined space. When looking into a manhole or catch basin,
stand above it and use the flashlight to help you see. Use a long pole or broom handle to check sediment
depths in confined spaces. NO PART OF YOUR BODY SHOULD BREAK THE PLANE OF THE OPEN
HOLE.
Ponds
There are essentially three kinds of ponds: treatment ponds, infiltration ponds, and detention ponds.
Although each pond has unique maintenance requirements, there are also many things they have in
common. Your facility is an infiltration pond.
INSPECTION FREQUENCY LOOK FOR ACTION
AREA
Entire Pond Quarterly Yard waste such as grass clippings Remove trash and debris and dispose of properly.
and branches in basin; presence of
glass, plastic, metal, foam, or
coated paper.
Entire Pond Quarterly Vegetation that may constitute a Remove invasive or noxious vegetation. Do not
public hazard, e.g., tansy ragwort, spray chemicals on vegetation without obtaining
poison oak, stinging nettles, guidance from WSU Cooperative Extension and
devilsclub. a royal from Cit or Count .
Entire Pond Quarterly Presence of chemicals such as First, attempt to locate source of pollution; then call
natural gas, oil, and gasoline, Moderate Risk Waste program at Thurston County
noxious odor, or sludge. Environmental Health to report the hazard.
Entire Pond Quarterly Sparse, weedy, or overgrown grass Grassy ponds: selectively thatch, aerate, and re-
in grassy (dry/infiltration) ponds; seed ponds. Grass should be kept less than 8
presence of invasive species or inches high. Wet ponds: hand-plant nursery-
sparse growth of plants in wet grown wetland plants in bare areas. Contact WSU
ponds. Cooperative Extension for guidance on invasive
species. Pond bottoms should have uniform dense
coverage of desired plant species.
Entire Pond Quarterly Evidence of rodent holes if facility Destroy rodents and repair dam or berm. Contact
is a dam or berm. Water should Thurston County Health Department for guidance.
not flow through rodent holes.
Entire Pond Quarterly Nuisance insects such as wasps, Destroy or remove insects. Contact WSU
hornets or mosquitoes that may Cooperative Extension for guidance.
interfere with maintenance
Entire Pond Annually Confirmation that trees are not Prune tree limbs to allow for maintenance. Some
interfering with maintenance (i.e., trees may be cut.
mowing, silt removal, or access.)
Inlet Annually Confirmation that the riprap under Replace rocks and/or remove sediment.
the inlet pipe is intact and that no
native soil is exposed. Also, look
for accumulations of sediment
greater than half the height of the
rocks.
Outlet Quarterly Afree-flowing overflow that is clear Replace riprap if missing. Remove trash or debris
of debris. and dispose of properly.
Side Slopes Annually Signs of erosion around inlets and Attempt to determine the cause of erosion and
outlets. Inspect berms for signs of repair it. Stabilize slopes by reinforcing with rock,
sliding or settling. Take action if planting grass, or compacting soil. Contact WSU
eroded damage is over 2 inches Cooperative Extension for guidance on slope
deep and where there is potential reinforcement.
for continued erosion.
Storage Area Annually Sediment build-up on pond bottom. Remove the sediment and re-seed the pond if
A buried or partially buried outlet necessary to improve infiltration and control
structure or very slow infiltration erosion.
rate may indicate significant
sediment deposits.
Dikes Annually Significant settling of any part of Build dike back to the original elevation.
dike.
Emergency Annually Intact riprap protective area. Repair Replace rocks so all native soil is covered.
Overflow/ Spillwa if an native soil is ex osed.
Trench Drain Quarterly Confirmation that the grate is clear Remove debris from grate, clean drain.
of debris and that the drain is not
plugged.
Catch Basins, Manholes, and Inlets
These structures are typically located in the streets and public rights-of-way. Local jurisdictions are
responsible for routine maintenance of the pipes and catch basins in rights-of-way, while you are
responsible for keeping the grates clear of debris in all areas as well as pipes and catch basins in private
areas.
INSPECTION FREQUENCY LOOK FOR ACTION
AREA
Catch basin During and after Accumulation of trash or debris in front of Remove blocking trash or debris with a
opening major storms catch basin opening that prevents water from rake and clean off the grate.
flowing in
Catch basin Quarterly Sediment or debris in the basin. No more Remove debris from catch basin.
than half the depth from the bottom of the
pipe to the bottom of the basin should be
allowed to accumulate. Use a long stick or
broom handle to poke into sediment and
determine depth.
Inlet and outlet Quarterly Trash or debris in the pipes that has Remove trash or debris from inlet and
pipes exceeded 1/5 of their height. Ensure there outlet pipes.
are not tree roots or other vegetation
growing in the pi es.
Inlet and outlet Annually Cracks wider than '/z inch and longer than Repair cracks or replace the joints.
pipe joints 12-inches at the joint of any inlet or outlet
pipe. Also check for evidence of sediment
entering the catch basin throu h cracks.
Grate Quarterly Cracks longer than 2 inches or multiple Replace grate if necessary.
cracks.
Frame Quarterly Confirmation that the frame is sitting flush on Repair or replace the frame so it is flush
top of the concrete structure (slab). A with the slab.
separation of more than'/< inch between the
frame and the slab should be corrected.
Catch basin Annually Cracks wider than '/2 inch and longer than 3 Replace or repair the basin. Contact a
feet. Also check for any evidence of professional engineer for evaluation.
sediment entering the catch basin through
cracks. Determine whether or not the
structure is sound.
Catch basin Quarterly Chemicals such as natural gas, oil, and Clean out catch basin. Contact your
gasoline have may have entered the catch local jurisdiction or Thurston County
basin. Check for noxious odor or oily sludge. Environmental Health if you detect a
color, odor, or oil slud e.
Oil /water Quarterly Significant sludge, oil, grease, or scum layer Remove the catch basin lid and skim off
separator covering all or most of the water surface. oil layer. Pour oil into a disposable
(downturned container, seal container, wrap securely
elbow or "T" in in newspaper, and place in trash. Water
catch basin) surface should be clear of oil la er.
Pipe elbow Quarterly Damage to top or bottom of pipe; determine If pipe is broken, replace pipe in
whether pipe is plumb. accordance with approved plans on file
with your local jurisdiction.
Conveyance Pipes, Ditches, and Swales
INSPECTION FREQUENCY LOOK FOR ACTION
AREA
Pipes Annually Confirmation that accumulated Clean pipes of all sediment
sediment has not exceeded 20% of and debris. Remove all
the diameter of the pipe and that vegetation so that water
vegetation has not reduced free flows freely through pipes.
movement of water through pipes. Repair or replace pipe as
Ensure that the protective coating is necessary.
not damaged and rusted. Dents
should not significantly impede flow.
Pipe should not have major cracks or
tears allowin water to leak out.
Open ditches Quarterly Yard waste or litter in the ditch. Remove trash and debris
and dis ose of ro erl .
Open ditches Annually Confirmation that accumulated Clean ditch of all sediment
sediment has not exceeded 20% of and debris.
the de th of the ditch.
Open ditches Annually Vegetation (e.g., weedy shrubs or Clear blocking vegetation so
& Swales saplings) that reduces the free that water flows freely
movement of water through ditches or through ditches. Grassy
swales. vegetation should be left
alone.
Open ditches Quarterly Signs of erosion. Inspect slopes for Eliminate causes of erosion.
& Swales signs of sloughing or settling. Action Stabilize slopes by using
is needed where eroded damage is appropriate erosion control
over 2 inches deep and where measures (e.g., reinforce
potential for continued erosion exists. with rock, plant grass,
com act soil.
Open ditches Annually Adequate rock placement in splash Replace rocks to design
& Swales pad, check dam or lining. Native soil standard.
should not be visible.
Swales Quarterly Adequate grass coverage. Take Aerate soils, reseed and
action if coverage is sparse and mulch bare areas. Keep
weedy, or areas are overgrown with grass less than 8 inches
woody vegetation. high. Remove woody
growth, regrade, and reseed
as necessar .
Swales Quarterly Confirmation that swale has not been If possible, speak with
filled in or blocked by structures, homeowner and request
shrubbery, etc. that the swale area be
restored.
Swales Annually Standing water in swale or very slow A survey may be needed to
flow velocity. Stagnation. verify grades. Grades
should be between 1-5%.
Grounds and Landscaping
INSPECTION
AREA FREQUENCY LOOK FOR ACTION
Landscaped Quarterly Uncontrolled weed growth in If possible, pull weeds by hand
Areas landscaped areas. to avoid using chemical weed
controls.
Landscaped Quarterly Presence of poison ivy or other Remove poisonous vegetation
Areas oisonous ve etation or insect nests. or insect nests.
Landscaped Quarterly Yard waste or litter Remove and dispose of
Areas ro erl .
Landscaped Quarterly Noticeably visible rills in landscaped Identify the causes of erosion
Areas areas. and take steps to slow down or
disperse the water. Fill in
contour; seed area.
Trees and Annually Split, broken or otherwise damaged Trim trees and shrubs to
shrubs tree parts and shrubs restore shape. Replace
severely damaged trees and
shrubs.
Trees and Annually Blown down or knocked over trees or Replant trees or shrubs,
shrubs shrubs inspecting for injury to stem or
roots. Replace if severely
dama ed.
Trees and Annually Exposed roots, inadequate support, Place stakes and rubber-
Shrubs severe leaning coated ties around young
trees/shrubs for support.
RESOURCE LISTING
If you suspect a problem exists, please contact your local jurisdiction at one of the numbers below and
ask for Technical Assistance.
Contact Numbers:
Yelm Public Works (360) 458-3244
WSU Cooperative Extension (360) 786-5445
Engineer's Information:
HATTON GODAT PANTIER
1840 Barnes Blvd SW
Tumwater, WA 98512
(360) 943-1599
LOG SHEET
Use log sheets to track maintenance checks and what items, if any, are repaired or altered. The
completed sheets will serve as a record of maintenance activity and will provide valuable information
about how your facilities are operating. Log sheets should be kept in a dry, readily accessible place.
INSPECTION DATE:
PERFORMED BY:
PHONE NUMBER: ADDRESS:
POSITION ON HOA: CITY, ST, ZIP:
• •: • ~~ •
~ e ~ • •
III. POLLUTION SOURCE CONTROL PROGRAM
What Are Pollution Source Controls And Why Are They Needed?
Pollution source controls are actions taken by a person or business to reduce the amount of pollution
reaching surface and ground waters. Controls, also called "best management practices" (BMPs) include:
^ Altering the activity (e.g., substitute non-toxic products, recycle used oil, route floor drains to
sanitary sewer rather than storm sewer).
^ Enclosing or covering the activity (e.g., building a roof).
^ Segregating the activity (e.g., diverting runoff away from an area that is contaminated).
^ Routing runoff from the activity to a treatment alternative (e.g., a wastewater treatment facility,
sanitary sewer, or stormwater treatment area).
Pollution source controls are needed because of the contamination found in runoff from commercial areas
and the effect of this contamination on aquatic life and human health. Research on urban runoff in the
Puget Sound area and elsewhere has found oil and grease, nutrients, organic substances, toxic metals,
bacteria, viruses, and sediments at unacceptable levels. Effects of contaminated runoff include closure of
shellfish harvesting areas and swimming areas, mortality of young fish and other aquatic organisms,
tumors on fish, and impairment of fish reproduction.
Materials Used And Wastes Generated
Of particular concern are drives and parking areas. Because of heavy vehicle usage, the concentration of
oil and grease in stormwater may exceed the Ecology guidelines of 10 mg/1. Although there are no local
data to confirm this view, limited research in the San Francisco Bay area found the mean concentration of
oil and grease in stormwater to exceed 10 mg/1.
Required Actions
The following actions shall be taken to ensure that pollution generated on site shall be minimized:
1. Warning signs (e.g., "Dump No Waste -Drains to Stream") shall be painted or embossed on
or adjacent to all storm drain inlets. They shall be repainted as needed. Materials needed to
undertake this task can be purchased or may be available from the Public Involvement
Coordinator for the Department of Public Works.
2. Sediment removed from basins, ponds, and swales shall be disposed of in a proper manner.
Contact the local governing jurisdiction for inspection prior to completing this task.
3. No activities shall be conducted on site that are likely to result in short-term, highly
concentrated discharge of pollution to the stormwater system. Such activities may include,
but are not limited to, heavy vehicle maintenance, and cleaning of equipment used in the
periodic maintenance of buildings and paved surfaces.
4. Use of pesticides and fertilizers shall be minimized.
5. Do not dump paint, solvents, oils, or other such substances, including landscape waste, into
storm drains or ponds.
APPENDIX A -Site Plan