2020.0110.PR0003 9339_Cruz_O & M Manual_3-6-20n
Larson & Associates
surveyors, engineers and planners
9027 Pacific Avenue, Suite 4
Tacoma, WA 98444
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OPERATION AND MAINTENANCE MANUAL
PROPONENT:
CRUZ DEVELOPMENTS, LLC
9935 COCHRANE AVE
YELM WA 98597
CONTACT: RYAN CRUZ
PHONE: (253) 318-5494
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PREPARED BY:
Larson & Associates
surveyors, engineers and planners
9027 Pacific Avenue, Suite 4
Tacoma, WA 98444
(253) 474-3404
March 6, 2020
SECTION 1 – PROPOSED PROJECT DESCRIPTION ................................................................... 1
SECTION 2 – MAINTENANCE IMPORTANCE AND INTENT .......................................................... 1-2
SECTION 3 – RESPONSIBLE PARTIES ................................................................................................... 2
SECTION 4 – FACILITIES REQUIRING MAINTENANCE .................................................................... 2
SECTION 5 – MAINTENANCE INSTRUCTIONS ...................................................................... 2-3
SECTION 6 - VEGETATION MAINTENANCE ........................................................................................ 3
SECTION 7 - POLLUTION SOURCE CONTROL MEASURES ........................................................... 3-4
SECTION 8 - ANNUAL COST OF MAINTENANCE ............................................................................... 4
APPENDIX A – STORM FACILITIES MAINTENANCE BMPS ......................................................... A-1
APPENDIX B – POLLUTION SOURCE CONTROL BMPS................................................................. B-1
SECTION 1 - PROPOSED PROJECT DESCRIPTION
The proposed Cruz Development project is located in the SE 1/4 of the NW 1/4 of Section 29,
Township 17 North, Range 2 East of the Willamette Meridian in Yelm, Washington. The address
is 17041 State Route (SR) 507, Yelm, WA 98597, and the parcel number is 64303200300. The
project consists of developing 8.76 acres of the 9.33-acre parcel into an automotive dealership with
the balance of the property dedicated to Washington State Dept. of Transportation (WSDOT) for
SR 507 right-of-way and to contain the existing single-family residence at the northwest corner of
the parcel. Property development will include a 12,000 square foot metal building, paved asphalt
parking, driveways and display area, graveled areas for vehicle storage, and the required
stormwater facilities, water and sewer utilities, and emergency vehicle access for the proposed
development. For regulating stormwater runoff, the City of Yelm has adopted Washington State
Dept. of Ecology’s 2012 Stormwater Management Manual for Western Washington
(SWMMWW) as amended in December 2014 and as amended by the City. In accordance with
Section 2.4, Volume I of the SWMMWW, this project must comply with all 9 Minimum
Requirements for stormwater management as more than 5,000 S.F. of new impervious surface will
be created by this project.
Stormwater runoff generated from pervious and impervious surface areas of the proposed building,
parking/driveway and outdoor display will be collected and conveyed to a biofiltration
swale/infiltration pond and bioretention cells for water quality treatment and flow control. All
created landscaped areas will receive compost amended topsoil in accordance with BMP T5.13,
Chapter V-5, Volume V of the SWMMWW.
SECTION 2 – MAINTENANCE IMPORATANCE AND INTENT
The importance of maintenance of the proper functioning of stormwater control facilities cannot
be over-emphasized. A substantial portion of failures (clogging of filters, resuspension of
sediments, loss of storage capacity, etc.) are due to inadequate maintenance. Stormwater BMP
maintenance is essential to ensure that BMPs function as intended throughout their full life cycle
The fundamentals goals of maintenance activities are to ensure the entire flow regime and
treatment train designed for this site continue to fully function. For this site these include:
•Maintain designed stormwater infiltration capacity
•Maintain ability of storm facility to attenuate flow rates
•Maintain ability of safely convey design stormwater flows
•Maintain ability to treat stormwater runoff quality
•Preserve soil and plant health, as well as stormwater flow contact with plant and soil
systems
•Clearly identify systems so they can be protected
•Keep maintenance costs low
1
•Prevent large-scale or expensive stormwater system failures
The intent of this section and manual is to pass on to the responsible party(s) all the information
critical to understand the design of the system, risks and considerations for proper use, suggestions
for maintenance frequencies, and cost so that realistic budgets can be established.
SECTION 3 – RESPONSIBLE PARTIES
The party responsible for maintenance and operation of all stormwater structures and BMPs
requiring maintenance for the proposed development is:
CRUZ DEVELOPMENTS, LLC
9935 COCHRANE AVE
YELM WA 98597
CONTACT: RYAN CRUZ
PHONE: (253) 318-5494
SECTION 4 – FACILITIES REQUIRING MAINTENANCE
There are three (3) primary stormwater BMPs for managing the project’s stormwater runoff: 1) an
infiltration pond for flow control of onsite runoff, 2) a biofiltration swale (a.k.a. bioswale) to
provide water quality treatment, and 3) bioretention cells in the landscaped areas that provide both
water quality treatment and flow control. A brief description of each storm drainage BMP or
facility is provided in the next section; maintenance items and checklists for each facility is
provided in Appendix A.
SECTION 5 – MAINTENANCE INSTRUCTIONS
The stormwater BMPs requiring maintenance are listed in Section 4 above and described in detail
below. Maintenance requirements for each BMP are provided in Appendix A.
1.INFILTRATION POND: Runoff from a significant portion of the impervious area onsite
including the building roof, driveways, parking and vehicle storage areas will be directed to an
infiltration pond at the west end of the property either through the upstream biofiltration swale
(a.k.a. bioswale) or piped from the commercial building roof downspouts. The pond is
designed to infiltrate the runoff into the highly permeable native soil under the pond. An
emergency overflow spillway located on the pond’s west berm is designed to release runoff in
the rare event the pond reaches capacity. A gravel access road at the sound end of the pond
will allow access to the pond bottom, side slopes and emergency overflow for maintenance.
Regular removal of the particulate pollutants, i.e. – sediment, and other debris and trash from
the pond is important to the proper function of the infiltration pond. Chain link fencing around
the pond perimeter with a gate at the access ramp will provide maintenance access control.
Typical maintenance items are provided in detail in Appendix A and include regular removal
2
of sediment, trash, debris, poisonous vegetation and noxious weeds, erosion of side slopes, and
repair of pipe inlet rip rap pads or the emergency overflow spillway.
2.BIOFILTRATION SWALE (A.K.A. BIOSWALE): Runoff from a portion of the asphalt
pavement and gravel impervious areas will be directed by grade and slope to a biofiltration
swale (bioswale) for water quality treatment before the runoff enters the infiltration pond.
Pollutants in the runoff settle out as the runoff passes through the bioswale’s vegetated cover.
Under the center of the bioswale is a 6-inch perforated underdrain pipe that runs the length of
the bioswale and is designed to minimize saturated conditions in the bioswale; the underdrain
pipe outlets at the infiltration pond. Typical maintenance items are listed in detail in Appendix
A and include periodic removal of accumulated sediment on the grass bottom, maintaining
proper vegetative coverage and removal of accumulated trash and debris.
3.BIORETENTION CELLS: Bioretention cells are located throughout the landscaped
areas of the property including the perimeter landscape, the parking area landscape islands,
and the landscaped area fronting SR 507. The bioretention cells are long, narrow depressions
designed to receive runoff from the adjacent pavement surfaces via sheet flow and provide
water quality treatment as the runoff passes through the compost/topsoil mix before infiltrating
into the highly permeable native soil underneath. Each bioretention cell includes plantings
which enhance the pollutant and runoff removal as well as providing a landscape function to
the property. Every bioretention cell will also have an overflow pipe that will route runoff that
exceeds the cells’ ponding depth directly to the native soil. Maintenance items are listed in
Appendix A and includes regular removal of trash, debris and sediment, checking for erosion
along the side slopes, and maintaining the plantings within the cell.
SECTION 6 – VEGETATION MAINTENANCE
The majority of the proposed landscaping will be provided in the landscape/screening buffers
along the perimeter of the project site. Compost amended soils conforming to BMP T5.13 will be
applied to all landscaped areas. Maintenance of landscape plantings are provided with the
approved landscape plans.
SECTION 7 – POLLUTION SOURCE CONTROL MEASURES
Pollution source control is the application of pollution prevention practices (BMPs) on a developed
site which reduces contamination of stormwater runoff at the source. In Volume IV of the
SWMMWW, Department of Ecology describes pollution source control as the application of
operational source control BMPs and structural source control BMPs. As a future commercial and
construction yard development applicable (i.e. – mandatory) operational source control BMPs
include:
•Formation of a pollution prevention team
•Good housekeeping practices
•Preventive maintenance procedures
•Spill prevention and cleanup
•Employee training
3
•Regular inspections
•Record Keeping
Detailed information of the following applicable structural source control BMPs are provided in
Appendix B:
•S411 – BMPs for Landscaping and Lawn/Vegetation Management
•S414 – BMPs for Maintenance and Repair of Vehicles and Equipment
•S417 – BMPs for Maintenance of Stormwater Drainage and Treatment Systems
•S421 – BMPs for Parking and Storage of Vehicles and Equipment
•S424 – BMPs for Roof/Building Drains at Manufacturing and Commercial Buildings
•S431 – BMPs for Washing and Steam Cleaning Vehicles/Equipment/Building Structures
SECTION 8 – ANNUAL COST OF MAINTENANCE
It is expected the party listed in Section 3 above will be responsible for maintaining all storm
drainage facilities and implementing pollution source control measures for all uses on the property.
The expected annual maintenance cost for the storm drainage facilities is estimated to be $2,000
to $3,000.
END OF REPORT
4
APPENDIX “A”
STORM FACILITIES
MAINTENANCE BMPs
A-1
Maintenance
Component Defect
Conditions When
Maintenance Is
Needed
Results Expected When
Maintenance Is Per-
formed
potential for erosion to
continue.
(Recommend a Goeth-
echnical engineer be
called in to inspect and
evaluate condition and
recommend repair of
condition.
Emergency Over-
flow/Spillway
Emergency Over-
flow/Spillway
Only one layer of rock
exists above native soil
in area five square feet
or larger, or any expos-
ure of native soil at the
top of out flow path of
spillway.
(Rip-rap on inside
slopes need not be
replaced.)
Rocks and pad depth are
restored to design stand-
ards.
Erosion See "Side Slopes of
Pond"
Table V-4.5.2(1) Maintenance Standards - Detention Ponds (continued)
Maintenance
Component Defect Conditions When Maintenance Is
Needed
Results Expec-
ted When
Maintenance
Is Performed
General
Trash & Debris See "Detention Ponds" (No. 1).
See "Detention
Ponds" (No. 1).
Poisonous/Noxious
Vegetation See "Detention Ponds" (No. 1).
See "Detention
Ponds" (No. 1).
Contaminants and
Pollution See "Detention Ponds" (No. 1).
See "Detention
Ponds" (No. 1).
Rodent Holes See "Detention Ponds" (No. 1).
See "Detention
Ponds" (No. 1)
Storage Area Sediment
Water ponding in infiltration pond
after rainfall ceases and appropriate
Sediment is
removed
Table V-4.5.2(2) Maintenance Standards - Infiltration
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 833A-2
Maintenance
Component Defect Conditions When Maintenance Is
Needed
Results Expec-
ted When
Maintenance
Is Performed
time allowed for infiltration. Treat-
ment basins should infiltrate Water
Quality Design Storm Volume within
48 hours, and empty within 24 hours
after cessation of most rain events.
(A percolation test pit or test of facility
indicates facility is only working at
90% of its designed capabilities. Test
every 2 to 5 years. If two inches or
more sediment is present, remove).
and/or facility is
cleaned so that
infiltration sys-
tem works
according to
design.
Filter Bags (if
applicable)
Filled with Sed-
iment and Debris
Sediment and debris fill bag more
than 1/2 full.
Filter bag is
replaced or sys-
tem is
redesigned.
Rock Filters
Sediment and
Debris
By visual inspection, little or no water
flows through filter during heavy rain
storms.
Gravel in rock
filter is
replaced.
Side Slopes
of Pond
Erosion See "Detention Ponds" (No. 1).
See "Detention
Ponds" (No. 1).
Emergency
Overflow
Spillway and
Berms over 4
feet in height.
Tree Growth See "Detention Ponds" (No. 1).
See "Detention
Ponds" (No. 1).
Piping See "Detention Ponds" (No. 1).
See "Detention
Ponds" (No. 1).
Emergency
Overflow
Spillway
Rock Missing See "Detention Ponds" (No. 1).
See "Detention
Ponds" (No. 1).
Erosion See "Detention Ponds" (No. 1).
See "Detention
Ponds" (No. 1).
Pre-settling
Ponds and
Vaults
Facility or sump
filled with Sediment
and/or debris
6" or designed sediment trap depth
of sediment.
Sediment is
removed.
Table V-4.5.2(2) Maintenance Standards - Infiltration (continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 834A-3
Maintenance
Component Defect Conditions When Maintenance is
Needed
Results
Expected
When Main-
tenance is
performed
Working frame have less than 1/2 inch of thread. proper tools.
Cover Difficult
to Remove
One maintenance person cannot remove lid
after applying normal lifting pressure.
(Intent is keep cover from sealing off access
to maintenance.)
Cover can be
removed by
one main-
tenance per-
son.
Ladder Ladder Rungs
Unsafe
Ladder is unsafe due to missing rungs, not
securely attached to basin wall, mis-
alignment, rust, cracks, or sharp edges.
Ladder meets
design stand-
ards and
allows main-
tenance per-
son safe
access.
Metal Grates
(If Applic-
able)
Grate opening
Unsafe Grate with opening wider than 7/8 inch.
Grate open-
ing meets
design stand-
ards.
Trash and
Debris
Trash and debris that is blocking more than
20% of grate surface inletting capacity.
Grate free of
trash and
debris.
Damaged or
Missing.
Grate missing or broken member(s) of the
grate.
Grate is in
place and
meets design
standards.
Table V-4.5.2(5) Maintenance Standards - Catch Basins (continued)
Maintenance
Com-
ponents
Defect Condition When Maintenance is
Needed
Results Expected
When Maintenance is
Performed
General Trash and
Debris
Trash or debris that is plugging
more than 20% of the openings in
the barrier.
Barrier cleared to design
flow capacity.
Metal Damaged/
Missing
Bars are bent out of shape more
than 3 inches.
Bars in place with no
bends more than 3/4
Table V-4.5.2(6) Maintenance Standards - Debris Barriers (e.g., Trash
Racks)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 840A-4
Maintenance
Com-
ponents
Defect Condition When Maintenance is
Needed
Results Expected
When Maintenance is
Performed
Bars.
Bars are missing or entire barrier
missing.
Bars are loose and rust is causing
50% deterioration to any part of bar-
rier.
inch.
Bars in place according
to design.
Barrier replaced or
repaired to design stand-
ards.
Inlet/Outlet
Pipe
Debris barrier missing or not
attached to pipe
Barrier firmly attached to
pipe
Table V-4.5.2(6) Maintenance Standards - Debris Barriers (e.g., Trash
Racks) (continued)
Maintenance
Components Defect Conditions When Maintenance is
Needed
Results Expec-
ted When Main-
tenance is
Performed
External:
Rock Pad
Missing or
Moved
Rock
Only one layer of rock exists above nat-
ive soil in area five square feet or lar-
ger, or any exposure of native soil.
Rock pad
replaced to
design stand-
ards.
Erosion Soil erosion in or adjacent to rock pad.
Rock pad
replaced to
design stand-
ards.
Dispersion Trench
Pipe
Plugged
with Sed-
iment
Accumulated sediment that exceeds
20% of the design depth.
Pipe cleaned/-
flushed so that
it matches
design.
Not Dis-
charging
Water Prop-
erly
Visual evidence of water discharging
at concentrated points along trench
(normal condition is a "sheet flow" of
water along trench). Intent is to prevent
erosion damage.
Trench
redesigned or
rebuilt to stand-
ards.
Perforations
Plugged.
Over 1/2 of perforations in pipe are
plugged with debris and sediment.
Perforated pipe
cleaned or
replaced.
Table V-4.5.2(7) Maintenance Standards - Energy Dissipaters
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 841A-5
Maintenance
Components Defect Conditions When Maintenance is
Needed
Results Expec-
ted When Main-
tenance is
Performed
Water
Flows Out
Top of "Dis-
tributor"
Catch
Basin.
Maintenance person observes or
receives credible report of water flow-
ing out during any storm less than the
design storm or its causing or appears
likely to cause damage.
Facility rebuilt
or redesigned
to standards.
Receiving
Area Over-
Saturated
Water in receiving area is causing or
has potential of causing landslide prob-
lems.
No danger of
landslides.
Internal:
Manhole/Chamber
Worn or
Damaged
Post,
Baffles,
Side of
Chamber
Structure dissipating flow deteriorates
to 1/2 of original size or any con-
centrated worn spot exceeding one
square foot which would make struc-
ture unsound.
Structure
replaced to
design stand-
ards.
Other
Defects See "Catch Basins" (No. 5).
See "Catch Bas-
ins" (No. 5).
Table V-4.5.2(7) Maintenance Standards - Energy Dissipaters
(continued)
Maintenance
Component
Defect or Prob-
lem
Condition When
Maintenance is
Needed
Recommended Maintenance to
Correct Problem
General
Sediment Accu-
mulation on
Grass
Sediment depth
exceeds 2
inches.
Remove sediment deposits on grass
treatment area of the bio-swale.
When finished, swale should be level
from side to side and drain freely
toward outlet. There should be no
areas of standing water once inflow
has ceased.
Standing Water
When water
stands in the
swale between
storms and does
not drain freely.
Any of the following may apply:
remove sediment or trash blockages,
improve grade from head to foot of
swale, remove clogged check dams,
add underdrains or convert to a wet
Table V-4.5.2(8) Maintenance Standards - Typical Biofiltration Swale
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 842A-6
Maintenance
Component
Defect or Prob-
lem
Condition When
Maintenance is
Needed
Recommended Maintenance to
Correct Problem
biofiltration swale.
Table V-4.5.2(8) Maintenance Standards - Typical Biofiltration Swale
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 843A-7
Maintenance
Component
Defect or Prob-
lem
Condition When
Maintenance is
Needed
Recommended Maintenance to
Correct Problem
Flow spreader
Flow spreader
uneven or
clogged so that
flows are not uni-
formly distributed
through entire
swale width.
Level the spreader and clean so that
flows are spread evenly over entire
swale width.
Constant Base-
flow
When small
quantities of
water continually
flow through the
swale, even
when it has been
dry for weeks,
and an eroded,
muddy channel
has formed in the
swale bottom.
Add a low-flow pea-gravel drain the
length of the swale or by-pass the
baseflow around the swale.
Poor Vegetation
Coverage
When grass is
sparse or bare or
eroded patches
occur in more
than 10% of the
swale bottom.
Determine why grass growth is poor
and correct that condition. Re-plant
with plugs of grass from the upper
slope: plant in the swale bottom at 8-
inch intervals. Or re-seed into
loosened, fertile soil.
Vegetation
When the grass
becomes excess-
ively tall (greater
than 10-inches);
when nuisance
weeds and other
vegetation starts
to take over.
Mow vegetation or remove nuisance
vegetation so that flow not impeded.
Grass should be mowed to a height
of 3 to 4 inches. Remove grass clip-
pings.
Excessive Shad-
ing
Grass growth is
poor because
sunlight does not
reach swale.
If possible, trim back over-hanging
limbs and remove brushy vegetation
on adjacent slopes.
Table V-4.5.2(8) Maintenance Standards - Typical Biofiltration Swale
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 844A-8
Maintenance
Component
Defect or Prob-
lem
Condition When
Maintenance is
Needed
Recommended Maintenance to
Correct Problem
Inlet/Outlet
Inlet/outlet areas
clogged with sed-
iment and/or
debris.
Remove material so that there is no
clogging or blockage in the inlet and
outlet area.
Trash and Debris
Accumulation
Trash and debris
accumulated in
the bio-swale.
Remove trash and debris from
bioswale.
Erosion/Scouring
Eroded or
scoured swale
bottom due to
flow chan-
nelization, or
higher flows.
For ruts or bare areas less than 12
inches wide, repair the damaged
area by filling with crushed gravel. If
bare areas are large, generally
greater than 12 inches wide, the
swale should be re-graded and re-
seeded. For smaller bare areas, over-
seed when bare spots are evident, or
take plugs of grass from the upper
slope and plant in the swale bottom
at 8-inch intervals.
Table V-4.5.2(8) Maintenance Standards - Typical Biofiltration Swale
(continued)
Maintenance
Component
Defect or Prob-
lem
Condition When
Maintenance is
Needed
Recommended Maintenance to
Correct Problem
General
Sediment Accu-
mulation
Sediment depth
exceeds 2-inches in
10% of the swale
treatment area.
Remove sediment deposits in
treatment area.
Water Depth
Water not retained to
a depth of about 4
inches during the wet
season.
Build up or repair outlet berm so
that water is retained in the wet
swale.
Wetland Veget-
ation
Vegetation becomes
sparse and does not
provide adequate fil-
tration, OR veget-
ation is crowded out
Determine cause of lack of vigor
of vegetation and correct.
Replant as needed. For excess-
ive cattail growth, cut cattail
shoots back and compost off-site.
Table V-4.5.2(9) Maintenance Standards - Wet Biofiltration Swale
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 845A-9
Maintenance
Component Defect
Conditions
When Main-
tenance is
Needed
Results Expected When Maintenance
is Performed
Erosion/scouring
Areas have
eroded or
scoured due
to flow chan-
nelization or
high flows.
For ruts or bare areas less than 12
inches wide, repair the damaged area by
filling with a 50/50 mixture of crushed
gravel and compost. The grass will
creep in over the rock in time. If bare
areas are large, generally greater than
12 inches wide, the vegetated filter strip
should be regraded and reseeded. For
smaller bare areas, overseed when bare
spots are evident.
Flow spreader
Flow spreader
is uneven or
clogged so
that flows are
not uniformly
distributed
over entire fil-
ter width.
Level the spreader and clean so that
flows are spread evenly over entire filter
width
Table V-4.5.2(20) Maintenance Standards - Compost Amended
Vegetated Filter Strip (CAVFS) (continued)
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
Facility Footprint
Earthen side
slopes and
berms
B, S
Erosion (gullies/
rills) greater
than 2 inches
deep around
inlets, outlet,
and alongside
slopes
l Eliminate cause of
erosion and stabilize
damaged area
(regrade, rock, veget-
ation, erosion control
matting)
l For deep channels
or cuts (over 3
inches in ponding
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 862A-10
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
depth), temporary
erosion control meas-
ures should be put in
place until per-
manent repairs can
be made.
l Properly designed,
constructed and
established facilities
with appropriate flow
velocities should not
have erosion prob-
lems except perhaps
in extreme events. If
erosion problems
persist, the following
should be reas-
sessed: (1) flow
volumes from con-
tributing areas and
bioretention facility
sizing; (2) flow velo-
cities and gradients
within the facility;
and (3) flow dis-
sipation and erosion
protection strategies
at the facility inlet.
A
Erosion of sides
causes slope to
become a haz-
ard
Take actions to eliminate
the hazard and stabilize
slopes
A, S
Settlement
greater than 3
Restore to design height
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 863A-11
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
inches (relative
to undisturbed
sections of
berm)
A, S
Downstream
face of berm
wet, seeps or
leaks evident
Plug any holes and com-
pact berm (may require
consultation with engin-
eer, particularly for larger
berms)
A
Any evidence of
rodent holes or
water piping in
berm
l Eradicate rodents
(see "Pest control")
l Fill holes and com-
pact (may require
consultation with
engineer, par-
ticularly for larger
berms)
Concrete side-
walls A
Cracks or failure
of concrete side-
walls
l Repair/ seal cracks
l Replace if repair is
insufficient
Rockery side-
walls A
Rockery side
walls are insec-
ure
Stabilize rockery side-
walls (may require con-
sultation with engineer,
particularly for walls 4 feet
or greater in height)
Facility area
All main-
tenance visits
(at least bian-
nually)
Trash and
debris present
Clean out trash and debris
Facility bottom
area A, S
Accumulated
sediment to
extent that infilt-
ration rate is
l Remove excess sed-
iment
l Replace any veget-
ation damaged or
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 864A-12
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
reduced (see
"Ponded water")
or surface stor-
age capacity sig-
nificantly
impacted
destroyed by sed-
iment accumulation
and removal
l Mulch newly planted
vegetation
l Identify and control
the sediment source
(if feasible)
l If accumulated sed-
iment is recurrent,
consider adding pre-
settlement or
installing berms to
create a forebay at
the inlet
During/after
fall leaf drop
Accumulated
leaves in facility
Remove leaves if there is
a risk to clogging outlet
structure or water flow is
impeded
Low per-
meability
check dams
and weirs
A, S
Sediment, veget-
ation, or debris
accumulated at
or blocking (or
having the
potential to
block) check
dam, flow con-
trol weir or ori-
fice
Clear the blockage
A, S
Erosion and/or
undercutting
present
Repair and take pre-
ventative measures to pre-
vent future erosion and/or
undercutting
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 865A-13
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
A
Grade board or
top of weir dam-
aged or not
level
Restore to level position
Ponded water B, S
Excessive pond-
ing water: Water
overflows during
storms smaller
than the design
event or ponded
water remains in
the basin 48
hours or longer
after the end of
a storm.
Determine cause and
resolve in the following
order:
1. Confirm leaf or
debris buildup in the
bottom of the facility
is not impeding infilt-
ration. If necessary,
remove leaf lit-
ter/debris.
2. Ensure that under-
drain (if present) is
not clogged. If neces-
sary, clear under-
drain.
3. Check for other
water inputs (e.g.,
groundwater, illicit
connections).
4. Verify that the facility
is sized appro-
priately for the con-
tributing area.
Confirm that the con-
tributing area has
not increased. If
steps #1-4 do not
solve the problem,
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 866A-14
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
the bioretention soil
is likely clogged by
sediment accu-
mulation at the sur-
face or has become
overly compacted.
Dig a small hole to
observe soil profile
and identify com-
paction depth or clog-
ging front to help
determine the soil
depth to be removed
or otherwise rehab-
ilitated (e.g., tilled).
Consultation with an
engineer is recom-
mended.
Bioretention
soil media
As needed
Bioretention soil
media pro-
tection is
needed when
performing main-
tenance requir-
ing entrance
into the facility
footprint
l Minimize all loading
in the facility foot-
print (foot traffic and
other loads) to the
degree feasible in
order to prevent com-
paction of biore-
tention soils.
l Never drive equip-
ment or apply heavy
loads in facility foot-
print.
l Because the risk of
compaction is higher
during saturated soil
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 867A-15
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
conditions, any type
of loading in the cell
(including foot traffic)
should be minimized
during wet con-
ditions. • Con-
sider measures to
distribute loading if
heavy foot traffic is
required or equip-
ment must be placed
in facility. As an
example, boards
may be placed
across soil to dis-
tribute loads and min-
imize compaction.
• If compaction
occurs, soil must be
loosened or oth-
erwise rehabilitated
to original design
state.
Inlets/Outlets/Pipes
Splash block
inlet A
Water is not
being directed
properly to the
facility and
away from the
inlet structure
Reconfigure/ repair blocks
to direct water to facility
and away from structure
Curb cut
inlet/outlet
M during the
wet season
and before
severe storm
Weekly during
fall leaf drop
Accumulated
leaves at curb
cuts
Clear leaves (particularly
important for key inlets
and low points along long,
linear facilities)
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 868A-16
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
is forecasted
Pipe inlet/out-
let
A Pipe is dam-
aged Repair/ replace
W Pipe is clogged Remove roots or debris
A, S
Sediment,
debris, trash, or
mulch reducing
capacity of
inlet/outlet
l Clear the blockage
l Identify the source of
the blockage and
take actions to pre-
vent future block-
ages
Weekly during
fall leaf drop
Accumulated
leaves at
inlets/outlets
Clear leaves (particularly
important for key inlets
and low points along long,
linear facilities)
A Maintain access
for inspections
l Clear vegetation
(transplant veget-
ation when possible)
within 1 foot of inlets
and outlets, maintain
access pathways
l Consultation with a
landscape architect
is recommended for
removal, transplant,
or substitution of
plants
Erosion con-
trol at inlet
A
Concentrated
flows are caus-
ing erosion
Maintain a cover of rock or
cobbles or other erosion
protection measure (e.g.,
matting) to protect the
ground where con-
centrated water enters the
facility (e.g., a pipe, curb
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 869A-17
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
cut or swale)
Trash rack
S
Trash or other
debris present
on trash rack
Remove/dispose
A Bar screen dam-
aged or missing
Repair/replace
Overflow A, S
Capacity
reduced by sed-
iment or debris
Remove sediment or
debris/dispose
Underdrain
pipe
Clean pipe
as needed
Clean orifice
at least bian-
nually (may
need more fre-
quent clean-
ing during wet
season)
l Plant
roots, sed-
iment or
debris
reducing
capacity of
underdrain
l Prolonged
surface
ponding
(see "Pon-
ded water"
l Jet clean or rotary
cut debris/roots from
underdrain(s)
l If underdrains are
equipped with a flow
restrictor (e.g., ori-
fice) to attenuate
flows, the orifice
must be cleaned reg-
ularly.
Vegetation
Facility bottom
area and
upland slope
vegetation
Fall and
Spring
Vegetation sur-
vival rate falls
below 75%
within first two
years of estab-
lishment (unless
project O&M
manual or
record drawing
stipulates more
l Determine cause of
poor vegetation
growth and correct
condition
l Replant as neces-
sary to obtain 75%
survival rate or
greater. Refer to ori-
ginal planting plan,
or approved jur-
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 870A-18
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
or less than
75% survival
rate).
isdictional species
list for appropriate
plant replacements
(See Appendix 3 -
Bioretention Plant
List, in the LID Tech-
nical Guidance
Manual for Puget
Sound).
l Confirm that plant
selection is appro-
priate for site grow-
ing conditions
l Consultation with a
landscape architect
is recommended for
removal, transplant,
or substitution of
plants
Vegetation
(general)As needed
Presence of dis-
eased plants
and plant mater-
ial
l Remove any dis-
eased plants or plant
parts and dispose of
in an approved loc-
ation (e.g., com-
mercial landfill) to
avoid risk of spread-
ing the disease to
other plants
l Disinfect gardening
tools after pruning to
prevent the spread
of disease
l See Pacific North-
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 871A-19
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
west Plant Disease
Management Hand-
book for information
on disease recog-
nition and for addi-
tional resources
l Replant as neces-
sary according to
recommendations
provided for "facility
bottom area and
upland slope veget-
ation".
Trees and
shrubs
All pruning
seasons (tim-
ing varies by
species)
Pruning as
needed
l Prune trees and
shrubs in a manner
appropriate for each
species. Pruning
should be performed
by landscape pro-
fessionals familiar
with proper pruning
techniques
l All pruning of mature
trees should be per-
formed by or under
the direct guidance
of an ISA certified
arborist
A
Large trees and
shrubs interfere
with operation of
the facility or
access for main-
tenance
l Prune trees and
shrubs using most
current ANSI A300
standards and ISA
BMPs.
l Remove trees and
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 872A-20
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
shrubs, if necessary.
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 873A-21
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
Fall and
Spring
Standing dead
vegetation is
present
l Remove standing
dead vegetation
l Replace dead veget-
ation within 30 days
of reported dead and
dying plants (as prac-
tical depending on
weather/planting sea-
son)
l If vegetation replace-
ment is not feasible
within 30 days, and
absence of veget-
ation may result in
erosion problems,
temporary erosion
control measures
should be put in
place immediately.
l Determine cause of
dead vegetation and
address issue, if pos-
sible
l If specific plants
have a high mortality
rate, assess the
cause and replace
with appropriate spe-
cies. Consultation
with a landscape
architect is recom-
mended.
Fall and
Planting l When working
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 874A-22
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
Spring beneath mature
trees
around and below
mature trees, follow
the most current
ANSI A300 stand-
ards and ISA BMPs
to the extent prac-
ticable (e.g., take
care to minimize any
damage to tree roots
and avoid com-
paction of soil).
l Planting of small
shrubs or ground-
covers beneath
mature trees may be
desirable in some
cases; such plant-
ings should use
mainly plants that
come as bulbs, bare
root or in 4-inch pots;
plants should be in
no larger than 1-gal-
lon containers.
Fall and
Spring
Presence of or
need for stakes
and guys (tree
growth, mat-
uration, and sup-
port needs)
l Verify location of
facility liners and
underdrain (if any)
prior to stake install-
ation in order to pre-
vent liner puncture
or pipe damage
l Monitor tree support
systems: Repair and
adjust as needed to
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 875A-23
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
provide support and
prevent damage to
tree.
l Remove tree sup-
ports (stakes, guys,
etc.) after one grow-
ing season or max-
imum of 1 year.
l Backfill stake holes
after removal.
Trees and
shrubs adja-
cent to vehicle
travel areas
(or areas
where vis-
ibility needs to
be main-
tained)
A
Vegetation
causes some
visibility (line of
sight) or driver
safety issues
l Maintain appropriate
height for sight clear-
ance
l When continued, reg-
ular pruning (more
than one time/ grow-
ing season) is
required to maintain
visual sight lines for
safety or clearance
along a walk or
drive, consider relo-
cating the plant to a
more appropriate loc-
ation.
l Remove or trans-
plant if continual
safety hazard
l Consultation with a
landscape architect
is recommended for
removal, transplant,
or substitution of
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 876A-24
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
plants
Flowering
plants A Dead or spent
flowers present
Remove spent flowers
(deadhead)
Perennials Fall Spent plants
Cut back dying or dead
and fallen foliage and
stems
Emergent
vegetation Spring
Vegetation com-
promises con-
veyance
Hand rake sedges and
rushes with a small rake
or fingers to remove dead
foliage before new growth
emerges in spring or
earlier only if the foliage is
blocking water flow
(sedges and rushes do not
respond well to pruning)
Ornamental
grasses (per-
ennial)
Winter and
Spring
Dead material
from previous
year's growing
cycle or dead
collapsed
foliage
l Leave dry foliage for
winter interest
l Hand rake with a
small rake or fingers
to remove dead
foliage back to
within several
inches from the soil
before new growth
emerges in spring or
earlier if the foliage
collapses and is
blocking water flow
Ornamental
grasses (ever-
green)
Fall and
Spring
Dead growth
present in
spring
l Hand rake with a
small rake or fingers
to remove dead
growth before new
growth emerges in
spring
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 877A-25
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
l Clean, rake, and
comb grasses when
they become too tall
l Cut back to ground
or thin every 2-3
years as needed
Noxious
weeds
M (March -
October, pre-
ceding seed
dispersal)
Listed noxious
vegetation is
present (refer to
current county
noxious weed
list)
l By law, class A & B
noxious weeds must
be removed,
bagged and dis-
posed as garbage
immediately
l Reasonable
attempts must be
made to remove and
dispose of class C
noxious weeds
l It is strongly encour-
aged that herbicides
and pesticides not
be used in order to
protect water quality;
use of herbicides
and pesticides may
be prohibited in
some jurisdictions
l Apply mulch after
weed removal (see
"Mulch" )
Weeds
M (March -
October, pre-
ceding seed
dispersal)
Weeds are
present
l Remove weeds with
their roots manually
with pincer-type
weeding tools, flame
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 878A-26
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
weeders, or hot
water weeders as
appropriate
l Follow IPM pro-
tocols for weed man-
agement (see
"Additional Main-
tenance Resources"
section for more
information on IPM
protocols)
Excessive
vegetation
Once in early
to mid- May
and once in
early- to mid-
September
Low-lying veget-
ation growing
beyond facility
edge onto side-
walks, paths, or
street edge
poses ped-
estrian safety
hazard or may
clog adjacent
permeable pave-
ment surfaces
due to asso-
ciated leaf litter,
mulch, and soil
l Edge or trim ground-
covers and shrubs at
facility edge
l Avoid mechanical
blade-type edger
and do not use
edger or trimmer
within 2 feet of tree
trunks
l While some clip-
pings can be left in
the facility to replen-
ish organic material
in the soil, excessive
leaf litter can cause
surface soil clogging
As needed
Excessive veget-
ation density
inhibits storm-
water flow bey-
ond design
ponding or
l Determine whether
pruning or other
routine maintenance
is adequate to main-
tain proper plant
density and aes-
thetics
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 879A-27
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
becomes a haz-
ard for ped-
estrian and
vehicular cir-
culation and
safety
l Determine if planting
type should be
replaced to avoid
ongoing main-
tenance issues (an
aggressive grower
under perfect grow-
ing conditions
should be trans-
planted to a location
where it will not
impact flow)
l Remove plants that
are weak, broken or
not true to form;
replace in-kind
l Thin grass or plants
impacting facility
function without leav-
ing visual holes or
bare soil areas
l Consultation with a
landscape architect
is recommended for
removal, transplant,
or substitution of
plants
As needed
Vegetation
blocking curb
cuts, causing
excessive sed-
iment buildup
and flow bypass
Remove vegetation and
sediment buildup
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 880A-28
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
Mulch
Mulch Following
weeding
Bare spots
(without mulch
cover) are
present or
mulch depth
less than 2
inches
l Supplement mulch
with hand tools to a
depth of 2 to 3
inches
l Replenish mulch per
O&M manual. Often
coarse compost is
used in the bottom of
the facility and arbor-
ist wood chips are
used on side slopes
and rim (above typ-
ical water levels)
l Keep all mulch away
from woody stems
Watering
Irrigation sys-
tem (if any)
Based on man-
ufacturer's
instructions
Irrigation system
present
Follow manufacturer's
instructions for O&M
A
Sprinklers or
drip irrigation
not dir-
ected/located to
properly water
plants
Redirect sprinklers or
move drip irrigation to
desired areas
Summer water-
ing (first year)
Once every 1-
2 weeks or as
needed during
prolonged dry
periods
Trees, shrubs
and ground-
covers in first
year of estab-
lishment period
l 10 to 15 gallons per
tree
l 3 to 5 gallons per
shrub
l 2 gallons water per
square foot for
groundcover areas
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 881A-29
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
l Water deeply, but
infrequently, so that
the top 6 to 12
inches of the root
zone is moist
l Use soaker hoses or
spot water with a
shower type wand
when irrigation sys-
tem is not present
o Pulse water to
enhance soil
absorption,
when feasible
o Pre-moisten
soil to break
surface tension
of dry or hydro-
phobic
soils/mulch, fol-
lowed by sev-
eral more
passes. With
this method ,
each pass
increases soil
absorption and
allows more
water to infilt-
rate prior to run-
off
l Add a tree bag or
slow-release water-
ing device (e.g.,
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 882A-30
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
bucket with a per-
forated bottom) for
watering newly
installed trees when
irrigation system is
not present
Summer water-
ing (second
and third
years)
Once every 2-
4 weeks or as
needed during
prolonged dry
periods
Trees, shrubs
and ground-
covers in
second or third
year of estab-
lishment period
l 10 to 15 gallons per
tree
l 3 to 5 gallons per
shrub
l 2 gallons water per
square foot for
groundcover areas
l Water deeply, but
infrequently, so that
the top 6 to 12
inches of the root
zone is moist
l Use soaker hoses or
spot water with a
shower type wand
when irrigation sys-
tem is not present
o Pulse water to
enhance soil
absorption,
when feasible
o Pre-moisten
soil to break
surface tension
of dry or hydro-
phobic
soils/mulch, fol-
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 883A-31
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
lowed by sev-
eral more
passes. With
this method ,
each pass
increases soil
absorption and
allows more
water to infilt-
rate prior to run-
off
Summer water-
ing (after
establishment)
As needed
Established
vegetation (after
3 years)
l Plants are typically
selected to be
drought tolerant and
not require regular
watering after estab-
lishment; however,
trees may take up to
5 years of watering
to become fully
established
l Identify trigger mech-
anisms for drought-
stress (e.g., leaf wilt,
leaf senescence,
etc.) of different spe-
cies and water imme-
diately after initial
signs of stress
appear
l Water during
drought conditions
or more often if
necessary to main-
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 884A-32
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
tain plant cover
Pest Control
Mosquitoes B, S
Standing water
remains for
more than 3
days after the
end of a storm
l Identify the cause of
the standing water
and take appropriate
actions to address
the problem (see
"Ponded water")
l To facilitate main-
tenance, manually
remove standing
water and direct to
the storm drainage
system (if runoff is
from non pollution-
generating surfaces)
or sanitary sewer
system (if runoff is
from pollution-gen-
erating surfaces)
after getting
approval from san-
itary sewer authority.
l Use of pesticides or
Bacillus thuring-
iensis israelensis
(Bti) may be con-
sidered only as a
temporary measure
while addressing the
standing water
cause. If overflow to
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 885A-33
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
a surface water will
occur within 2 weeks
after pesticide use,
apply for coverage
under the Aquatic
Mosquito Control
NPDES General Per-
mit.
Nuisance
animals As needed
Nuisance anim-
als causing
erosion, dam-
aging plants, or
depositing large
volumes of
feces
l Reduce site con-
ditions that attract
nuisance species
where possible (e.g.,
plant shrubs and tall
grasses to reduce
open areas for
geese, etc.)
l Place predator
decoys
l Follow IPM pro-
tocols for specific
nuisance animal
issues (see "Addi-
tional Maintenance
Resources" section
for more information
on IPM protocols)
l Remove pet waste
regularly
l For public and right-
of-way sites con-
sider adding
garbage cans with
dog bags for picking
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 886A-34
Maintenance
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed (Stand-
ards)
Action Needed (Pro-
cedures)
Inspection Routine Main-
tenance
up pet waste.
Insect pests
Every site
visit asso-
ciated with
vegetation
management
Signs of pests,
such as wilting
leaves, chewed
leaves and bark,
spotting or
other indicators
l Reduce hiding
places for pests by
removing diseased
and dead plants
l For infestations, fol-
low IPM protocols
(see "Additional
Maintenance
Resources" section
for more information
on IPM protocols)
Note that the inspection and routine maintenance frequencies listed above are recom-
mended by Ecology. They do not supersede or replace the municipal stormwater permit
requirements for inspection frequency required of municipal stormwater permittees for
"stormwater treatment and flow control BMPs/facilities".
a Frequency: A = Annually; B = Biannually (twice per year); M = Monthly; W = At least
one visit should occur during the wet season (for debris/clog related maintenance, this
inspection/maintenance visit should occur in the early fall, after deciduous trees have
lost their leaves); S = Perform inspections after major storm events (24-hour storm event
with a 10-year or greater recurrence interval).
IPM - Integrated Pest Management
ISA - International Society of Arboriculture
Table V-4.5.2(21) Maintenance Standards - Bioretention Facilities
(continued)
Component
Recommended Fre-
quency a
Condition
when Main-
tenance is
Needed
(Standards)
Action Needed (Procedures)
Inspection Routine
Maintenance
Surface/Wearing Course
Permeable A, S
Runoff from l Clean deposited soil or
Table V-4.5.2(22) Maintenance Standards - Permeable Pavement
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 887A-35
APPENDIX “B”
STRUCTURAL SOURCE CONTROL BMPs FOR
CONSTRUCTION AND COMMERCIAL USES
B-1
S411 BMPs for Landscaping and Lawn/ Vegetation
Management
Description of Pollutant Sources:Landscaping can include grading, soil transfer,
vegetation removal, pesticide and fertilizer applications, and watering. Stormwater con-
taminants include toxic organic compounds, heavy metals, oils, total suspended solids,
coliform bacteria, fertilizers, and pesticides.
Lawn and vegetation management can include control of objectionable weeds, insects,
mold, bacteria, and other pests with pesticides. Examples include weed control on golf
course lawns, access roads, and utility corridors and during landscaping; sap stain and
insect control on lumber and logs; rooftop moss removal; killing nuisance rodents; fun-
gicide application to patio decks, and residential lawn/plant care. It is possible to release
toxic pesticides such as pentachlorophenol, carbamates, and organometallics to the
environment by leaching and dripping from treated parts, container leaks, product mis-
use, and outside storage of pesticide contaminated materials and equipment. Poor man-
agement of the vegetation and poor application of pesticides or fertilizers can cause
appreciable stormwater contamination.
Pollutant Control Approach:Control of fertilizer and pesticide applications, soil
erosion, and site debris to prevent contamination of stormwater.
Develop and implement an Integrated Pest Management Plan (IPM) and use pesticides
only as a last resort. Carefully apply pesticides/ herbicides, in accordance with label
instructions. Maintain appropriate vegetation, with proper fertilizer application where
practicable, to control erosion and the discharge of stormwater pollutants. Where prac-
ticable grow plant species appropriate for the site, or adjust the soil properties of the sub-
ject site to grow desired plant species.
Applicable Operational BMPs for Landscaping:
l Install engineered soil/landscape systems to improve the infiltration and regulation
of stormwater in landscaped areas.
l Do not dispose of collected vegetation into waterways or storm sewer systems.
Recommended Additional Operational BMPs for Landscaping:
l Conduct mulch-mowing whenever practicable
l Dispose of grass clippings, leaves, sticks, or other collected vegetation, by com-
posting, if feasible.
l Use mulch or other erosion control measures on soils exposed for more than one
week during the dry season or two days during the rainy season.
l Store and maintain appropriate oil and chemical spill cleanup materials in readily
B-2
accessible locations when using oil or other chemicals. Ensure that employees are
familiar with proper spill cleanup procedures.
l Till fertilizers into the soil rather than dumping or broadcasting onto the surface.
Determine the proper fertilizer application rate for the types of soil and vegetation
encountered.
l Till a topsoil mix or composted organic material into the soil to create a well-mixed
transition layer that encourages deeper root systems and drought-resistant plants.
l Use manual and/or mechanical methods of vegetation removal rather than apply-
ing herbicides, where practical.
Applicable Operational BMPs for the Use of Pesticides:
l Develop and implement an IPM (See section on IPM in Applicable Operational
BMPs for Vegetation Management) and use pesticides only as a last resort.
l Implement a pesticide-use plan and include at a minimum: a list of selected pesti-
cides and their specific uses; brands, formulations, application methods and quant-
ities to be used; equipment use and maintenance procedures; safety, storage, and
disposal methods; and monitoring, record keeping, and public notice procedures.
All procedures shall conform to the requirements of Chapter 17.21 RCW and
Chapter 16-228 WAC (Appendix IV-D:Regulatory Requirements That Impact
Stormwater Programs (p.723)R.7).
l Choose the least toxic pesticide available that is capable of reducing the infest-
ation to acceptable levels. The pesticide should readily degrade in the envir-
onment and/or have properties that strongly bind it to the soil. Conduct any pest
control activity at the life stage when the pest is most vulnerable. For example, if it
is necessary to use a Bacillus thuringiens application to control tent caterpillars,
apply it to the material before the caterpillars cocoon or it will be ineffective. Any
method used should be site-specific and not used wholesale over a wide area.
l Apply the pesticide according to label directions. Do not apply pesticides in quant-
ities that exceed manufacturer’s instructions.
l Mix the pesticides and clean the application equipment in an area where acci-
dental spills will not enter surface or ground waters, and will not contaminate the
soil.
l Store pesticides in enclosed areas or in covered impervious containment. Do not
discharge pesticide contaminated stormwater or spills/leaks of pesticides to storm
sewers. Do not hose down the paved areas to a storm sewer or conveyance ditch.
Store and maintain appropriate spill cleanup materials in a location known to all
near the storage area.
l Clean up any spilled pesticides. Keep pesticide contaminated waste materials in
B-3
designated covered and contained areas.
l The pesticide application equipment must be capable of immediate shutoff in the
event of an emergency.
l Spraying pesticides within 100 feet of open waters including wetlands, ponds, and
rivers, streams, creeks, sloughs and any drainage ditch or channel that leads to
open water may have additional regulatory requirements beyond just following the
pesticide product label. Additional requirements may include:
o Obtaining a discharge permit from Ecology.
o Obtaining a permit from the local jurisdiction.
o Using an aquatic labeled pesticide.
l Flag all sensitive areas including wells, creeks, and wetlands prior to spraying.
l Post notices and delineate the spray area prior to the application, as required by
the local jurisdiction or by Ecology.
l Conduct spray applications during weather conditions as specified in the label dir-
ection and applicable local and state regulations. Do not apply during rain or imme-
diately before expected rain.
Recommended Additional Operational BMPs for the use of pesticides:
l Consider alternatives to the use of pesticides such as covering or harvesting
weeds, substitute vegetative growth, and manual weed control/moss removal.
l Consider the use of soil amendments, such as compost, that are known to control
some common diseases in plants, such as Pythium root rot, ashy stem blight, and
parasitic nematodes. The following are three possible mechanisms for disease con-
trol by compost addition (USEPA Publication 530-F-9-044):
1. Successful competition for nutrients by antibiotic production;
2. Successful predation against pathogens by beneficial microorganism; and
3. Activation of disease-resistant genes in plants by composts.
Installing an amended soil/landscape system can preserve both the plant system
and the soil system more effectively. This type of approach provides a soil/-
landscape system with adequate depth, permeability, and organic matter to sustain
itself and continue working as an effective stormwater infiltration system and a sus-
tainable nutrient cycle.
l Once a pesticide is applied, evaluate its effectiveness for possible improvement.
Records should be kept showing the effectiveness of the pesticides considered.
l Develop an annual evaluation procedure including a review of the effectiveness of
B-4
pesticide applications, impact on buffers and sensitive areas (including potable
wells), public concerns, and recent toxicological information on pesticides used/-
proposed for use. If individual or public potable wells are located in the proximity of
commercial pesticide applications, contact the regional Ecology hydrogeologist to
determine if additional pesticide application control measures are necessary.
l Rinseate from equipment cleaning and/or triple-rinsing of pesticide containers
should be used as product or recycled into product.
For more information, contact the Washington State University (WSU) Extension Home-
Assist Program, (253) 445-4556, or Bio-Integral Resource Center (BIRC), P.O. Box
7414, Berkeley, CA.94707, or EPA to obtain a publication entitled “Suspended,
Canceled, and Restricted Pesticides” which lists all restricted pesticides and the specific
uses that are allowed.
Applicable Operational BMPs for Vegetation Management:
l Use at least an eight-inch "topsoil" layer with at least 8 percent organic matter to
provide a sufficient vegetation-growing medium. Amending existing landscapes
and turf systems by increasing the percent organic matter and depth of topsoil can
substantially improve the permeability of the soil, the disease and drought res-
istance of the vegetation, and reduce fertilizer demand. This reduces the demand
for fertilizers, herbicides, and pesticides. Organic matter is the least water-soluble
form of nutrients that can be added to the soil. Composted organic matter generally
releases only between 2 and 10 percent of its total nitrogen annually, and this
release corresponds closely to the plant growth cycle. Return natural plant debris
and mulch to the soil, to continue recycling nutrients indefinitely.
l Select the appropriate turfgrass mixture for the climate and soil type. Certain tall fes-
cues and rye grasses resist insect attack because the symbiotic endophytic fungi
found naturally in their tissues repel or kill common leaf and stem-eating lawn
insects. However, they do not, repel root-feeding lawn pests such as Crane Fly lar-
vae, and are toxic to ruminants such as cattle and sheep. The fungus causes no
known adverse effects to the host plant or to humans. Endophytic grasses are com-
mercially available; use them in areas such as parks or golf courses where grazing
does not occur. Local agricultural or gardening resources such as Washington
State University Extension office can offer advice on which types of grass are best
suited to the area and soil type.
l Use the following seeding and planting BMPs, or equivalent BMPs to obtain inform-
ation on grass mixtures, temporary and permanent seeding procedures, main-
tenance of a recently planted area, and fertilizer application rates:BMP C120:
Temporary and Permanent Seeding (p.278),BMP C121:Mulching (p.284),BMP
C123:Plastic Covering (p.294), and BMP C124:Sodding (p.296).
l Adjusting the soil properties of the subject site can assist in selection of desired
B-5
plant species. For example, design a constructed wetland to resist the invasion of
reed canary grass by layering specific strata of organic matters (e.g., composted
forest product residuals) and creating a mildly acidic pH and carbon-rich soil
medium. Consult a soil restoration specialist for site-specific conditions.
l Aerate lawns regularly in areas of heavy use where the soil tends to become com-
pacted. Conduct aeration while the grasses in the lawn are growing most vig-
orously. Remove layers of thatch greater than ¾-inch deep.
l Mowing is a stress-creating activity for turfgrass. Grass decreases its productivity
when mown too short and there is less growth of roots and rhizomes. The turf
becomes less tolerant of environmental stresses, more disease prone and more
reliant on outside means such as pesticides, fertilizers, and irrigation to remain
healthy. Set the mowing height at the highest acceptable level and mow at times
and intervals designed to minimize stress on the turf. Generally mowing only 1/3 of
the grass blade height will prevent stressing the turf.
Irrigation:
l The depth from which a plant normally extracts water depends on the rooting depth
of the plant. Appropriately irrigated lawn grasses normally root in the top 6 to 12
inches of soil; lawns irrigated on a daily basis often root only in the top 1 inch of
soil. Improper irrigation can encourage pest problems, leach nutrients, and make a
lawn completely dependent on artificial watering. The amount of water applied
depends on the normal rooting depth of the turfgrass species used, the available
water holding capacity of the soil, and the efficiency of the irrigation system. Con-
sult with the local water utility, Conservation District, or Cooperative Extension
office to help determine optimum irrigation practices.
Fertilizer Management:
l Turfgrass is most responsive to nitrogen fertilization, followed by potassium and
phosphorus. Fertilization needs vary by site depending on plant, soil, and climatic
conditions. Evaluation of soil nutrient levels through regular testing ensures the
best possible efficiency and economy of fertilization. For details on soils testing,
contact the local Conservation District, a soils testing professional, or a Wash-
ington State University Extension office.
l Apply fertilizers in amounts appropriate for the target vegetation and at the time of
year that minimizes losses to surface and ground waters. Do not fertilize when the
soil is dry. Alternatively, do not apply fertilizers within three days prior to predicted
rainfall. The longer the period between fertilizer application and either rainfall or
irrigation, the less fertilizer runoff occurs.
l Use slow release fertilizers such as methylene urea, IDBU, or resin coated fer-
tilizers when appropriate, generally in the spring. Use of slow release fertilizers is
especially important in areas with sandy or gravelly soils.
B-6
l Time the fertilizer application to periods of maximum plant uptake. Ecology gen-
erally recommends application in the fall and spring, although Washington State
University turf specialists recommend four fertilizer applications per year.
l Properly trained persons should apply all fertilizers. Apply no fertilizer at com-
mercial and industrial facilities, to grass swales, filter strips, or buffer areas that
drain to sensitive water bodies unless approved by the local jurisdiction.
Integrated Pest Management
An IPM program might consist of the following steps:
Step 1: Correctly identify problem pests and understand their life cycle
Step 2: Establish tolerance thresholds for pests.
Step 3: Monitor to detect and prevent pest problems.
Step 4: Modify the maintenance program to promote healthy plants and discourage
pests.
Step 5: Use cultural, physical, mechanical or biological controls first if pests exceed the
tolerance thresholds.
Step 6: Evaluate and record the effectiveness of the control and modify maintenance
practices to support lawn or landscape recovery and prevent recurrence.
For an elaboration of these steps, refer to Appendix IV-F: Example of an Integrated Pest
Management Program (p.739).
S412 BMPs for Loading and Unloading Areas for Liquid or
Solid Material
Description of Pollutant Sources: Operators typically conduct loading/unloading of
liquid and solid materials at industrial and commercial facilities at shipping and receiv-
ing, outside storage, fueling areas, etc. Materials transferred can include products, raw
materials, intermediate products, waste materials, fuels, scrap metals, etc. Leaks and
spills of fuels, oils, powders, organics, heavy metals, salts, acids, alkalis, etc. during
transfer may cause stormwater contamination. Spills from hydraulic line breaks are a
common problem at loading docks.
Pollutant Control Approach: Cover and contain the loading/unloading area where
necessary to prevent run-on of stormwater and runoff of contaminated stormwater.
B-7
Ecology’s Baseline General Permit Requirements:
Industries with log yards are required to obtain coverage under the Industrial Stormwater
General Permit for discharges of stormwater associated with industrial activities. The per-
mit requires preparation and on-site retention of an Industrial Stormwater Pollution Pre-
vention Plan (SWPPP). Required and recommended operational, structural source
control, and treatment BMPs are presented in detail in Ecology’s Guidance Document:
Industrial Stormwater General Permit Implementation Manual for Log Yards,Publication
#04-10-031. Ecology recommends that all log yard facilities obtain a copy of this doc-
ument.
S414 BMPs for Maintenance and Repair of Vehicles and
Equipment
Description of Pollutant Sources:Pollutant sources include parts/vehicle cleaning,
spills/leaks of fuel and other liquids, replacement of liquids, outdoor storage of bat-
teries/liquids/parts, and vehicle parking.
Pollutant Control Approach:Control of leaks and spills of fluids using good house-
keeping and cover and containment BMPs.
Applicable Operational BMPs:
l Inspect all incoming vehicles, parts, and equipment stored temporarily outside for
leaks.
l Use drip pans or containers under parts or vehicles that drip or that are likely to
drip liquids, such as during dismantling of liquid containing parts or removal or
transfer of liquids.
l Remove batteries and liquids from vehicles and equipment in designated areas
designed to prevent stormwater contamination. Store cracked batteries in a
covered non-leaking secondary containment system.
l Remove liquids from vehicles retired for scrap.
l Empty oil and fuel filters before disposal. Provide for proper disposal of waste oil
and fuel.
l Do not pour/convey washwater, liquid waste, or other pollutants into storm drains
or to surface water. Check with the local sanitary sewer authority for approval to
convey water to a sanitary sewer.
l Do not connect maintenance and repair shop floor drains to storm drains or to sur-
face water.
l To allow for snowmelt during the winter, install a drainage trench with a sump for
B-8
particulate collection. Use the drainage trench for draining the snowmelt only and
not for discharging any vehicular or shop pollutants.
Applicable Structural Source Control BMPs:
l Conduct all maintenance and repair of vehicles and equipment in a building, or
other covered impervious containment area that is sloped to prevent run-on of
uncontaminated stormwater and runoff of contaminated water.
l Operators may conduct maintenance of refrigeration engines in refrigerated trailers
in the parking area. Exercise due caution to avoid the release of engine or refri-
geration fluids to storm drains or surface water.
l Park large mobile equipment, such as log stackers, in a designated contained
area.
Additional applicable BMPs:
l S409 BMPs for Fueling At Dedicated Stations (p.629)
l S410 BMPs for Illicit Connections to Storm Drains (p.633)
l S412 BMPs for Loading and Unloading Areas for Liquid or Solid Material (p.639)
l S426 BMPs for Spills of Oil and Hazardous Substances (p.666)
l S427 BMPs for Storage of Liquid,Food Waste,or Dangerous Waste Containers
(p.667)
l S428 BMPs for Storage of Liquids in Permanent Aboveground Tanks (p.676)
l S429 BMPs for Storage or Transfer (Outside)of Solid Raw Materials,Byproducts,
or Finished Products (p.679)
l S431 BMPs for Washing and Steam Cleaning Vehicles/Equipment/Building Struc-
tures (p.686)
Applicable Treatment BMPs:Convey contaminated stormwater runoff from vehicle sta-
ging and maintenance areas to a sanitary sewer, if allowed by the local sewer authority,
or to an API or CP oil and water separator followed by a basic treatment BMP (See
Volume V (p.765)), applicable filter, or other equivalent oil treatment system.
Note this applicable treatment BMP for contaminated stormwater.
Recommended Additional Operational BMPs:
l Store damaged vehicles inside a building or other covered containment, until suc-
cessfully removing all liquids.
l Clean parts with aqueous detergent based solutions or non-chlorinated solvents
such as kerosene or high flash mineral spirits, and/or use wire brushing or sand
B-9
blasting whenever practicable. Avoid using toxic liquid cleaners such as methyl-
ene chloride, 1,1,1-trichloroethane, trichloroethylene or similar chlorinated
solvents. Choose cleaning agents that can be recycled.
l Inspect all BMPs regularly, particularly after a significant storm. Identify and correct
deficiencies to ensure that the BMPs are functioning as intended.
l Avoid hosing down work areas. Use dry methods for cleaning leaked fluids.
l Recycle greases, used oil, oil filters, antifreeze, cleaning solutions, automotive bat-
teries, hydraulic fluids, transmission fluids, and engine oils (see Appendix IV-C:
Recycling/Disposal of Vehicle Fluids/Other Wastes*(p.721)).
l Do not mix dissimilar or incompatible waste liquids stored for recycling.
S415 BMPs for Maintenance of Public and Private Utility
Corridors and Facilities
Description of Pollutant Sources:Passageways and equipment at petroleum product,
natural gas, and water pipelines, and electrical power transmission corridors and rights-
of-way can be sources of pollutants such as herbicides used for vegetation man-
agement, and eroded soil particles from unpaved access roads. At pump stations, waste
materials generated during maintenance activities may be temporarily stored outside.
Additional potential pollutant sources include the leaching of preservatives from wood
utility poles, PCBs in older transformers, water removed from underground transformer
vaults, and leaks/spills from petroleum pipelines. The following are potential pollutants:
oil and grease, TSS, BOD, organics, PCBs, pesticides, and heavy metals.
Pollutant Control Approach:Control of fertilizer and pesticide applications, soil
erosion, and site debris that can contaminate stormwater.
Applicable Operational BMPs:
l Implement S411 BMPs for Landscaping and Lawn/Vegetation Management
(p.634)and R.7 in Appendix IV-D:Regulatory Requirements That Impact Storm-
water Programs (p.723)on Pesticide Regulations.
l When removing water or sediments from electric transformer vaults, determine the
presence of contaminants before disposing of the water and sediments. This
includes inspecting for the presence of oil or sheen, and determining from records
or testing if the transformers contain PCBs. If records or tests indicate that the sed-
iments or water are contaminated above applicable levels, manage these media in
accordance with applicable federal and state regulations, including the federal
PCB rules (40 CFR 761) and the state MTCA cleanup regulations (Chapter 173-
340 WAC). Water removed from the vaults can be discharged in accordance with
the federal 40 CFR 761.79, and state regulations (Chapter 173-201A WAC and
B-10
health department for disposal options.
l Examine culverts on a regular basis for scour or sedimentation at the inlet and out-
let, and repair as necessary. Give priority to those culverts conveying perennial
and/or salmon-bearing streams and culverts near streams in areas of high sed-
iment load, such as those near subdivisions during construction.
Recommended Treatment BMPs:
Install biofiltration swales and filter strips – (See Chapter V-9 -Biofiltration Treatment
Facilities (p.1029)) to treat roadside runoff wherever practicable and use engineered top-
soils wherever necessary to maintain adequate vegetation. These systems can improve
infiltration and stormwater pollutant control upstream of roadside ditches.
S417 BMPs for Maintenance of Stormwater Drainage and
Treatment Systems
Description of Pollutant Sources:Facilities include roadside catch basins on arterials
and within residential areas, conveyance systems, detention facilities such as ponds
and vaults, oil/water separators, biofilters, settling basins, infiltration systems, and all
other types of stormwater treatment systems presented in Volume V (p.765). Oil and
grease, hydrocarbons, debris, heavy metals, sediments and contaminated water are
found in catch basins, oil and water separators, settling basins, etc.
Pollutant Control Approach:Provide maintenance and cleaning of debris, sediments,
and oil from stormwater collection, conveyance, and treatment systems to obtain proper
operation.
Applicable Operational BMPs:
Maintain stormwater treatment facilities per the operations and maintenance (O&M) pro-
cedures presented in V-4.6 Maintenance Standards for Drainage Facilities (p.829)in
addition to the following BMPs:
l Inspect and clean treatment BMPs, conveyance systems, and catch basins as
needed, and determine necessary O&M improvements.
l Promptly repair any deterioration threatening the structural integrity of stormwater
facilities. These include replacement of clean-out gates, catch basin lids, and rock
in emergency spillways.
l Ensure adequacy of storm sewer capacities and prevent heavy sediment dis-
charges to the sewer system.
l Regularly remove debris and sludge from BMPs used for peak-rate control, treat-
ment, etc. and discharge to a sanitary sewer if approved by the sewer authority, or
truck to an appropriate local or state government approved disposal site.
B-11
l Clean catch basins when the depth of deposits reaches 60 percent of the sump
depth as measured from the bottom of basin to the invert of the lowest pipe into or
out of the basin. However, in no case should there be less than six inches clear-
ance from the debris surface to the invert of the lowest pipe. Some catch basins (for
example, WSDOT Type 1L basins) may have as little as 12 inches sediment stor-
age below the invert. These catch basins need frequent inspection and cleaning to
prevent scouring. Where these catch basins are part of a stormwater collection and
treatment system, the system owner/operator may choose to concentrate main-
tenance efforts on downstream control devices as part of a systems approach.
l Clean woody debris in a catch basin as frequently as needed to ensure proper
operation of the catchbasin.
l Post warning signs; “Dump No Waste - Drains to Ground Water,” “Streams,”
“Lakes,” or emboss on or adjacent to all storm drain inlets where possible.
l Disposal of sediments and liquids from the catch basins must comply with
Appendix IV-G:Recommendations for Management of Street Wastes (p.743).
Additional Applicable BMPs:Select additional applicable BMPs from this chapter
depending on the pollutant sources and activities conducted at the facility. Those BMPs
include:
l S425 BMPs for Soil Erosion and Sediment Control at Industrial Sites (p.665)
l S427 BMPs for Storage of Liquid,Food Waste,or Dangerous Waste Containers
(p.667)
l S426 BMPs for Spills of Oil and Hazardous Substances (p.666)
l S410 BMPs for Illicit Connections to Storm Drains (p.633)
l S430 BMPs for Urban Streets (p.684)
S418 BMPs for Manufacturing Activities - Outside
Description of Pollutant Sources:Manufacturing pollutant sources include outside pro-
cess areas, stack emissions, and areas where manufacturing activity has taken place in
the past and significant exposed pollutant materials remain.
Pollution Control Approach:Cover and contain outside manufacturing and prevent
stormwater run-on and contamination, where feasible.
Applicable Operational BMP:
l Sweep paved areas regularly, as needed, to prevent contamination of stormwater.
l Alter the activity by eliminating or minimizing the contamination of stormwater.
B-12
S421 BMPs for Parking and Storage of Vehicles and
Equipment
Description of Pollutant Sources:Public and commercial parking lots such as retail
store, fleet vehicle (including rent-a-car lots and car dealerships), equipment sale and
rental parking lots, and parking lot driveways, can be sources of toxic hydrocarbons and
other organic compounds, including oils and greases, metals, and suspended solids.
Pollutant Control Approach:If the parking lot is a high-use site as defined below,
provide appropriate oil removal equipment for the contaminated stormwater runoff.
Applicable Operational BMPs:
l If washing a parking lot, discharge the washwater to a sanitary sewer, if allowed by
the local sewer authority, or other approved wastewater treatment system, or col-
lect washwater for off-site disposal.
l Do not hose down the area to a storm sewer or receiving water. Vacuum sweep
parking lots, storage areas, and driveways regularly to collect dirt, waste, and
debris.
Applicable Treatment BMPs:An oil removal system such as an API or CP oil and
water separator, catch basin filter, or equivalent BMP, approved by the local jurisdiction,
is necessary for parking lots meeting the threshold vehicle traffic intensity level of a high-
use site.
Vehicle High-Use Sites
Establishments subject to vehicle high-use intensity are significant sources of oil con-
tamination of stormwater. Examples of potential high use areas include customer park-
ing lots at fast food stores, grocery stores, taverns, restaurants, large shopping malls,
discount warehouse stores, quick-lube shops, and banks. If the PGIS for a high-use site
exceeds 5,000 square feet in a threshold discharge area, an oil control BMP from the Oil
Control Menu (in Volume V (p.765)) is necessary. A high-use site at a commercial or
industrial establishment has one of the following characteristics: (Gaus/King County,
1994)
l Is subject to an expected average daily vehicle traffic (ADT) count equal to or
greater than 100 vehicles per 1,000 square feet of gross building area: or
l Is subject to storage of a fleet of 25 or more diesel vehicles that are over 10 tons
gross weight (trucks, buses, trains, heavy equipment, etc.).
S422 BMPs for Railroad Yards
Description of Pollutant Sources:Pollutant sources can include:
B-13
Potential sources of pollutants include paper, plastic, metal scrap debris, engines, trans-
missions, radiators, batteries, and other materials contaminated or that contain fluids.
Other pollutant sources include leachate from metal components, contaminated soil, and
the erosion of soil. Activities that can generate pollutants include the transfer, dis-
mantling, and crushing of vehicles and scrap metal; the transfer and removal of fluids;
maintenance and cleaning of vehicles, parts, and equipment; and storage of fluids, parts
for resale, solid wastes, scrap parts, and materials, equipment and vehicles that contain
fluids; generally in uncovered areas.
Potential pollutants typically found at vehicle recycle and scrap yards include oil and
grease, ethylene and propylene glycol, PCBs, total suspended solids, BOD, heavy
metals, and acidic pH.
Applicable Best Management Practices:
For facilities subject to Ecology’s Industrial Stormwater General Permit refer to BMP
Guidance Document #94-146, Vehicle Recyclers: A Guide for Implementing the Indus-
trial Stormwater General National Pollutant Discharge Elimination System (NPDES) Per-
mit Requirements, Ecology, March
2011,website:https://fortress.wa.gov/ecy/publications/summarypages/94146.html. Apply
the BMPs in that guidance document to scrap material recycling facilities depending on
the pollutant sources existing at those facilities.
S424 BMPs for Roof/ Building Drains at Manufacturing and
Commercial Buildings
Description of Pollutant Sources: Stormwater runoff from roofs and sides of man-
ufacturing and commercial buildings can be sources of pollutants caused by leaching of
roofing materials, building vents, and other air emission sources. Research has iden-
tified vapors and entrained liquid and solid droplets/particles as potential pollutants in
roof/building runoff. Metals, solvents, acidic/alkaline pH, BOD, and organics, are some of
the pollutant constituents identified.
Ecology has performed a study on zinc in industrial stormwater. The study is presented
in Ecology Publication 08-10-025 Suggested Practices to reduce Zinc Concentrations in
Industrial Stormwater Discharges, website: https://-
fortress.wa.gov/ecy/publications/summarypages/0810025.html. The user should refer to
this document for more details on addressing zinc in stormwater.
Pollutant Control Approach: Evaluate the potential sources of stormwater pollutants
and apply source control BMPs where feasible.
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Applicable Operational Source Control BMPs:
l If leachates and/or emissions from buildings are suspected sources of stormwater
pollutants, then sample and analyze the stormwater draining from the building.
l Sweep the area routinely to remove any zinc residuals.
l If a roof/building stormwater pollutant source is identified, implement appropriate
source control measures such as air pollution control equipment, selection of mater-
ials, operational changes, material recycle, process changes, etc.
Applicable Structural Source Control BMPs:
l Paint/coat the galvanized surfaces as described in Ecology Publication #08-10-
025.
Applicable Treatment BMPs:
Treat runoff from roofs to the appropriate level. The facility may use enhanced treatment
BMPs as described in Volume V (p.765). Some facilities regulated by the Industrial
Stormwater General Permit, or local jurisdiction, may have requirements than cannot be
achieved with enhanced treatment BMPs. In these cases, additional treatment measures
may be required. A treatment method for meeting stringent requirements such as
Chitosan-Enhanced Sand Filtration may be appropriate.
S425 BMPs for Soil Erosion and Sediment Control at
Industrial Sites
Description of Pollutant Sources:Industrial activities on soil areas; exposed and dis-
turbed soils; steep grading; etc. can be sources of sediments that can contaminate storm-
water runoff.
Pollutant Control Approach:Limit the exposure of erodible soil, stabilize, or cover erod-
ible soil where necessary to prevent erosion, and/or provide treatment for stormwater
contaminated with TSS caused by eroded soil.
Applicable BMPs:
Cover Practice Options:
l Vegetative cover such as grass, trees, shrubs, on erodible soil areas.
l Covering with mats such as clear plastic, jute, synthetic fiber.
l Preservation of natural vegetation including grass, trees, shrubs, and vines.
Structural Practice Options:
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erland, 1998). This assumes pavements under good condition and the most favor-
able accumulation conditions.
l Conduct vacuum sweeping at optimal frequencies. Optimal frequencies are those
scheduled sweeping intervals that produce the most cost-effective annual reduc-
tion of pollutants normally found in stormwater and can vary depending on land
use, traffic volume and rainfall patterns.
l Train operators in those factors that result in optimal pollutant removal. These
factors include sweeper speed, brush adjustment and rotation rate, sweeping pat-
tern, maneuvering around parked vehicles, and interim storage and disposal meth-
ods.
l Consider the use of periodic parking restrictions in low to medium density single-
family residential areas to ensure the sweeper’s ability to sweep along the curb.
l Establish programs for prompt vacuum sweeping, removal, and disposal of debris
from special events that will generate higher than normal loadings.
l Disposal of street sweeping solids must comply with Appendix IV-G:Recom-
mendations for Management of Street Wastes (p.743).
l Inform citizens about eliminating yard debris, oil and other wastes in street gutters
to reduce street pollutant sources.
S431 BMPs for Washing and Steam Cleaning Vehicles/
Equipment/ Building Structures
Description of Pollutant Sources: Pollutant sources include the commercial cleaning
of vehicles, aircraft, vessels, and other transportation, restaurant kitchens, carpets, and
industrial equipment, and large buildings with low- or high-pressure water or steam. This
includes “charity” car washes at gas stations and commercial parking lots. The cleaning
can include hand washing, scrubbing, sanding, etc. Washwater from cleaning activities
can contain oil and grease, suspended solids, heavy metals, soluble organics, soaps,
and detergents that can contaminate stormwater.
Pollutant Control Approach: The preferred approach is to cover and/or contain the
cleaning activity, or conduct the activity inside a building, to separate the uncon-
taminated stormwater from the washwater sources. Convey washwater to a sanitary
sewer after approval by the local sewer authority. Provide temporary storage before
proper disposal, or recycling. Under this preferred approach, no discharge to the ground,
to a storm drain, or to surface water should occur.
The Industrial Stormwater General Permit prohibits the discharge of process wastewater
(e.g., vehicle washing wastewater) to ground water or surface water. Stormwater that
commingles with process wastewater is considered process wastewater.
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Facilities not covered under the Industrial Stormwater General Permit that are unable to
follow one of the preferred approaches listed above may discharge washwater to the
ground only after proper treatment in accordance with Ecology guidance WQ-95-056,
Vehicle and Equipment Washwater Discharges/Best Management Practices Manual,
November 2012 or most recent update.
The quality of any discharge to the ground after proper treatment must comply with Eco-
logy’s Ground Water Quality Standards,Chapter 173-200 WAC.
Facilities not covered under the Industrial Stormwater General Permit that are unable to
comply with one of the preferred approaches and want to discharge to storm sewer, must
meet their local stormwater requirements. Local authorities may require treatment prior to
discharge.
Contact the local Ecology Regional Office to discuss permitting options for discharge of
washwater to surface water or to a storm drain after on-site treatment.
Applicable Structural Source Control BMPs:Conduct vehicle/ equipment washing in
one of the following locations:
l At a commercial washing facility in which the washing occurs in an enclosure and
drains to the sanitary sewer, or
l In a building constructed specifically for washing of vehicles and equipment, which
drains to a sanitary sewer.
Conduct outside washing operation in a designated wash area with the following fea-
tures:
l In a paved area, construct a spill containment pad to prevent the run-on of storm-
water from adjacent areas. Slope the spill containment area to collect washwater in
a containment pad drain system with perimeter drains, trench drains or catchment
drains. Size the containment pad to extend out a minimum of four feet on all sides
of the washed vehicles and/or equipment.
l Convey the washwater to a sump (like a grit separator) and then to a sanitary
sewer (if allowed by the local Sewer Authority), or other appropriate wastewater
treatment or recycle system. The containment sump must have a positive control
outlet valve for spill control with live containment volume, and oil/water separation.
Size the minimum live storage volume to contain the maximum expected daily
washwater flow plus the sludge storage volume below the outlet pipe. Shut the out-
let valve during the washing cycle to collect the washwater in the sump. The valve
should remain shut for at least two hours following the washing operation to allow
the oil and solids to separate before discharge to a sanitary sewer.
l Close the inlet valve in the discharge pipe when washing is not occurring, thereby
preventing the entry of uncontaminated stormwater into the pretreatment/ treatment
system. The stormwater can then drain into the conveyance/discharge system
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outside of the wash pad (essentially bypassing the sanitary sewer or recycle sys-
tem). Post signs to inform people of the operation and purpose of the valve. Clean
the concrete pad thoroughly until there is no foam or visible sheen in the wash-
water prior to closing the inlet valve and allowing uncontaminated stormwater to
overflow and drain off the pad.
Note that the purpose of the valve is to convey only washwater and contaminated
stormwater to a treatment system.
l Collect the washwater from building structures and convey it to appropriate treat-
ment such as a sanitary sewer system if it contains oils, soaps, or detergents. If the
washwater does not contain oils, soaps, or detergents (in this case only a low pres-
sure, clean, cold water rinse is allowed) then it could drain to soils that have suf-
ficient natural attenuation capacity for dust and sediment.
Recommended Additional BMPs:
l Mark the wash area at gas stations, multi-family residences and any other busi-
ness where non-employees wash vehicles.
l Operators may use a manually operated positive control valve for uncovered wash
pads, but a pneumatic or electric valve system is preferable. The valve may be on
a timer circuit and opened upon completion of a wash cycle. After draining the
sump or separator, the timer would then close the valve.
l Use phosphate-free biodegradable detergents when practicable.
l Consider recycling the washwater.
Operators may use soluble/emulsifiable detergents in the wash medium and should use
it with care and the appropriate treatment. Carefully consider the selection of soaps and
detergents and treatment BMPs. Oil/water separators are ineffective in removing emul-
sified or water soluble detergents. Another treatment appropriate for emulsified and
water soluble detergents may be required.
Exceptions
l At gas stations (for charity car washes) or commercial parking lots, where it is not
possible to discharge the washwater to a sanitary sewer, a temporary plug or a tem-
porary sump pump can be used at the storm drain to collect the washwater for off-
site disposal such as to a nearby sanitary sewer.
l New and used car dealerships may wash vehicles in the parking stalls as long as
employees use a temporary plug system to collect the washwater for disposal as
stated above, or an approved treatment system for the washwater is in place.
At industrial sites, contact Ecology for NPDES Permit requirements even when not using
soaps, detergents, and/or other chemical cleaners in washing trucks.
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