Loading...
2020.0010 MU - O & M Manual Larson & Associates surveyors, engineers and planners 9027 Pacific Avenue, Suite 4 Tacoma, WA 98444 OPERATION AND MAINTENANCE MANUAL PROPONENT: CRUZ DEVELOPMENTS, LLC 9935 COCHRANE AVE YELM WA 98597 CONTACT: RYAN CRUZ PHONE: (253) 318-5494 PREPARED BY: Larson & Associates surveyors, engineers and planners 9027 Pacific Avenue, Suite 4 Tacoma, WA 98444 (253) 474-3404 March 6, 2020 Revised July 9, 2021 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. A vicinity map, parcel map and aerial of the project parcels are provided in Appendix A. The project consists of developing 5.86 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 the City of Yelm and WSDOT for future right-of-way. An existing single- family residence at the northwest corner of the parcel will be converted to a temporary office. Property development will include a 12,000 square foot metal building, paved asphalt parking, driveways, display area, and vehicle storage, and the required stormwater facilities, water and sewer utilities, and emergency vehicle access for the proposed development. A Notice of Decision for site plan approval with conditions was issued by the City on April 22, 2021. For regulating stormwater runoff the City of Yelm has adopted the latest version of the Washington State Dept. of Ecology’s Stormwater Management Manual for Western Washington (SWMMWW) dated July 2019 and as amended by the city. In accordance with Section 3.3, 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 disturbed pervious areas will receive compost amended topsoil in accordance with BMP T5.13, Chapter V-11, 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 1 •Clearly identify systems so they can be protected •Keep maintenance costs low •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 2 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 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 3 •Spill prevention and cleanup •Employee training •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 Appendix V-A: BMP Maintenance Tables Ecology intends the facility-specific maintenance standards contained in this section to be conditions for determining if maintenance actions are required as identified through inspection. Recognizing that Permittees have limited main- tenance funds and time, Ecology does not require that a Permittee perform all these maintenance activities on all their stormwater BMPs. We leave the determination of importance of each maintenance activity and its priority within  the stormwater program to the Permittee. We do expect, however, that sufficient maintenance will occur to ensure that the BMPs continue to operate as designed to protect ground and surface waters. Ecology doesn’t intend that these measures identify the facility's required condition at all times between inspections. In other words, exceedance of these conditions at any time between inspections and/or maintenance does not auto- matically constitute a violation of these standards. However, based upon inspection observations, the Permittee shall adjust inspection and maintenance schedules to minimize the length of time that a facility is in a condition that  requires a maintenance action. Maintenance Com- ponent Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed General Trash & Debris  Any trash and debris which exceed 1 cubic feet per 1,000 square feet. In general, there  should be no visual evidence of dumping.  If less than threshold all trash and debris will be removed as part of next scheduled main- tenance. Trash and debris cleared from site  Poisonous Veget- ation and noxious  weeds    Any poisonous or nuisance vegetation which may constitute a hazard to maintenance per- sonnel or the public. Any evidence of noxious weeds as defined by State or local regulations. (Apply requirements of adopted IPM policies for the use of herbicides). No danger of poisonous vegetation where maintenance personnel or the public might normally be. (Coordin- ate with local health department) Complete eradication of noxious weeds may not be possible. Compliance with State or local eradication  policies required Contaminants and  Pollution  Any evidence of oil, gasoline, contaminants or other pollutants (Coordinate removal/cleanup with local water quality response agency). No contaminants or pollutants present. Rodent Holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water  piping through dam or berm via rodent holes. Rodents destroyed and dam or berm repaired. (Coordinate with local health department; coordinate with  Ecology Dam Safety Office if pond exceeds 10 acre-feet.)  Beaver Dams Dam results in change or function of the facility. Facility is returned to design function. (Coordinate trapping of beavers and removal of dams with appropriate permitting agencies) Insects When insects such as wasps and hornets interfere with maintenance activities.  Insects destroyed or removed from site. Apply insecticides in compliance with adopted IPM policies Tree Growth and  Hazard Trees   Tree growth does not allow maintenance and inspection access or interferes with main- tenance activity (i.e., slope mowing, silt removal, vactoring, or equipment movements). If  trees are not interfering with access or maintenance, do not remove If dead, diseased, or dying trees are identified (Use a certified Arborist to determine health of tree or removal requirements) Trees do not hinder maintenance activities. Harvested trees should be recycled into mulch or other bene- ficial uses (e.g., alders for firewood).  Remove hazard Trees Side Slopes of Pond  Erosion   Eroded damage over 2 inches deep where cause of damage is still present or where there is  potential for continued erosion.  Any erosion observed on a compacted berm embankment. Slopes should be stabilized using appropriate erosion control measure(s); e.g.,rock reinforcement, planting  of grass, compaction. If erosion is occurring on compacted berms a licensed engineer in the state of Washington should be con- sulted to resolve source of erosion. Storage Area Sediment Accumulated sediment that exceeds 10% of the designed pond depth unless otherwise spe- cified or affects inletting or outletting condition of the facility. Sediment cleaned out to designed pond shape and depth; pond reseeded if necessary to control erosion.  Table V-A.1: Maintenance Standards - Detention Ponds 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1005 A-2 Maintenance Com- ponent Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed Liner (if Applic- able) Liner is visible and has more than three 1/4-inch holes in it. Liner repaired or replaced. Liner is fully covered.  Ponds Berms (Dikes)      Settlements  Any part of berm which has settled 4 inches lower than the design elevation  If settlement is apparent, measure berm to determine amount of settlement Settling can be an indication of more severe problems with the berm or outlet works. A  licensed engineer in the state of Washington should be consulted to determine the source of  the settlement. Dike is built back to the design elevation.  Piping   Discernable water flow through pond berm. Ongoing erosion with potential for erosion to con- tinue. (Recommend a Goethechnical engineer be called in to inspect and evaluate condition and  recommend repair of condition. Piping eliminated. Erosion potential resolved.  Emergency Overflow/  Spillway and Berms  over 4 feet in height     Tree Growth     Tree growth on emergency spillways creates blockage problems and may cause failure of the  berm due to uncontrolled overtopping. Tree growth on berms over 4 feet in height may lead to piping through the berm which could  lead to failure of the berm. Trees should be removed. If root system is small (base less than 4 inches) the root system may be left in  place. Otherwise the roots should be removed and the berm restored. A licensed engineer in the state of  Washington should be consulted for proper berm/spillway restoration.  Piping   Discernable water flow through pond berm. Ongoing erosion with potential for erosion to con- tinue. (Recommend a Geotechnical engineer be called in to inspect and evaluate condition and  recommend repair of condition. Piping eliminated. Erosion potential resolved.  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 standards.  Erosion See "Side Slopes of Pond"  Table V-A.1: Maintenance Standards - Detention Ponds (continued) Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Per- formed General Trash & Debris See Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- tion Ponds  Poisonous/Noxious  Vegetation See Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- tion Ponds Contaminants and  Pol- lution See  Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- tion Ponds Rodent Holes See Table V-A.1: Maintenance Standards - Detention Ponds See  Table V-A.1: Maintenance Standards - Deten- tion Ponds Storage Area Sediment Water ponding in  infiltration pond after rainfall ceases and appropriate time allowed for  infiltration. Treatment basins should infiltrate  Water Quality Design Storm  Volume within 48 hours, and empty within 24 hours after cessation of most  rain events. Sediment is  removed and/or facility is cleaned so  that infiltration system works  according to design. Table V-A.2: Maintenance Standards - Infiltration 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1006 A-3 Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Per- formed (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).  Filter Bags (if  applicable)Filled with  Sediment and  Debris Sediment and  debris fill bag more than 1/2 full.Filter bag is  replaced or system 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 Table V-A.1: Maintenance Standards - Detention Ponds See  Table V-A.1: Maintenance Standards - Deten- tion Ponds Emergency Overflow  Spillway  and Berms over 4 feet in height. Tree Growth See  Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- tion Ponds Piping See Table V-A.1: Maintenance Standards - Detention Ponds See  Table V-A.1: Maintenance Standards - Deten- tion Ponds Emergency Overflow  Spillway Rock Missing See  Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- tion Ponds Erosion See  Table V-A.1: Maintenance Standards - Detention Ponds See Table V-A.1: Maintenance Standards - Deten- tion Ponds 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-A.2: Maintenance Standards - Infiltration (continued) Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Maintenance is Per- formed Storage Area Plugged Air Vents One-half of the  cross section of a vent is blocked at any point or the vent is damaged. Vents open and  functioning. Debris and  Sediment Accumulated  sediment depth exceeds 10% of the diameter of the storage area for 1/2 length  of storage vault or any point  depth exceeds 15% of diameter.  (Example: 72-inch  storage tank would require cleaning when sediment reaches depth of 7 inches  for more than 1/2 length of  tank.) All sediment and  debris removed from storage  area. Joints Between  Tank/Pipe Section Any openings or  voids allowing material to be transported into facility. (Will require  engineering analysis to determine structural stability). All joint between  tank/pipe sections are sealed. Tank Pipe Bent Out  of Shape Any part of  tank/pipe is bent out of shape more than 10% of its design shape. (Review  required by engineer to determine  structural stability).Tank/pipe repaired  or replaced to design. Vault Structure  Includes Cracks in Wall, Bottom,  Damage to Frame and/or Top Slab Cracks wider than  1/2-inch and any evidence of soil particles entering the structure through  the cracks, or main- tenance/inspection personnel determines that the vault is  not structurally sound. Cracks wider than  1/2-inch at the joint of any inlet/outlet pipe or any evidence of soil  particles entering the vault through the  walls. Vault replaced or  repaired to design spe- cifications and is structurally sound. No cracks more  than 1/4-inch wide at the joint of  the inlet/outlet pipe. Table V-A.3: Maintenance Standards - Closed Detention Systems (Tanks/Vaults) 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1007 A-4 Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Maintenance is per- formed General Trash & Debris  Trash or debris  which is located immediately in front of the catch basin opening or is  blocking inletting capacity of the basin by more than 10%. Trash or debris  (in the basin) that exceeds 60 percent of the sump depth as measured from the  bottom of basin to invert of the lowest pipe into or out of the  basin, but in  no case less than a minimum of six inches clearance from the debris surface  to the invert of the lowest pipe. Trash or debris in  any inlet or outlet pipe blocking more than 1/3 of its height. Dead animals or  vegetation that could generate odors that could cause complaints or dangerous  gases (e.g., methane). No Trash or debris  located immediately in front of  catch basin or on grate opening. No trash or debris  in the catch basin. Inlet and outlet  pipes free of trash or debris. No dead animals or  vegetation present within the  catch basin. Sediment Sediment (in the  basin) that exceeds 60 percent of the sump depth as measured from the bottom  of basin to invert of the lowest pipe into or out of the  basin, but in no  case less than a minimum of 6 inches clearance from the sediment surface to  the invert of the lowest pipe.No sediment in the  catch basin Structure Damage  to  Frame and/or Top Slab Top slab has holes  larger than 2 square inches or cracks wider than 1/4 inch. (Intent is to make  sure no material is running into basin). Frame not sitting  flush on top slab, i.e., separation of more than 3/4 inch of the frame from  the top slab. Frame not securely attached Top slab is free  of holes and cracks. Frame is sitting  flush on the riser rings or top slab  and firmly attached. Fractures or  Cracks in  Basin Walls/ Bottom Maintenance person judges that structure is  unsound. Grout fillet has  separated or cracked wider than 1/2 inch and longer than 1 foot at the joint  of any inlet/outlet pipe or any evidence of soil particles entering  catch  basin through cracks. Basin replaced or  repaired to design standards. Pipe is regrouted  and secure at basin wall. Settlement/  Mis- alignment If failure of  basin has created a safety, function, or design problem. Basin replaced or  repaired to design standards. Vegetation Vegetation growing  across and blocking more than 10% of the basin opening. Vegetation growing  in inlet/outlet pipe joints that is more than six inches tall and less than  six inches apart. No vegetation  blocking opening to basin. No vegetation or  root growth present. Contamination and  Pol- lution See Table V-A.1: Maintenance Standards - Detention Ponds No pollution  present. Catch Basin  Cover Cover Not in Place Cover is missing  or only partially in place. Any open catch basin requires maintenance.Cover/grate is in place, meets design standards,  and is secured Locking Mechanism  Not Working Mechanism cannot be  opened by one maintenance person with proper tools. Bolts into frame have  less than 1/2 inch of thread.Mechanism opens  with 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 maintenance per- son. Ladder Ladder Rungs  Unsafe Ladder is unsafe  due to missing rungs, not securely attached to basin wall, misalignment,  rust, cracks, or sharp edges.Ladder meets  design standards and allows main- tenance person safe access. Metal Grates  (If Applicable) Grate opening  Unsafe Grate with opening  wider than 7/8 inch.Grate opening  meets design standards. 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, meets the design standards, and  is installed and aligned with the flow path. Table V-A.5: Maintenance Standards - Catch Basins 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1009 A-5 Maintenance Components 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. Bars are bent out  of shape more than 3 inches. Bars are missing  or entire barrier missing. Bars are loose and  rust is causing 50% deterioration to any part of barrier. Bars in place with  no bends more than 3/4 inch. Bars in place  according to design. Barrier replaced  or repaired to design standards. Inlet/Outlet Pipe Debris barrier  missing or not attached to pipe Barrier firmly  attached to pipe Table V-A.6: Maintenance Standards - Debris Barriers (e.g., Trash Racks) Maintenance Com- ponents Defect Conditions When Maintenance is Needed Results Expected When Maintenance is Performed External: Rock Pad Missing or Moved  Rock Only one layer of  rock exists above native soil in area five square feet or larger, or any  exposure of native soil.Rock pad replaced  to design standards. Erosion Soil erosion in or  adjacent to rock pad.Rock pad replaced  to design standards. Dispersion Trench Pipe Plugged with  Sediment Accumulated  sediment that exceeds 20% of the design depth. Pipe  cleaned/flushed so that it matches  design. Not Discharging  Water Properly 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 standards. Perforations  Plugged.Over 1/2 of  perforations in pipe are plugged with debris and sediment.Perforated pipe  cleaned or replaced. Water Flows Out Top of "Distributor"  Catch Basin. Maintenance person  observes or receives credible report of water flowing 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 problems.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 concentrated  worn spot exceeding one square foot which would  make structure unsound.Structure replaced  to design standards. Other Defects See Table V-A.5: Maintenance Standards - Catch Basins See Table V-A.5: Maintenance Standards -  Catch Basins Table V-A.7: Maintenance Standards - Energy Dissipators 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 biofiltration swale. Flow spreader Flow spreader  uneven or clogged so that flows are not uniformly  distributed through entire  swale width.Level the spreader  and clean so that flows are spread evenly over entire swale width. Table V-A.8: Maintenance Standards - Typical Biofiltration Swale 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1010 A-6 Maintenance Component Defect or Prob- lem Condition When Maintenance is Needed Recommended Maintenance to Correct Problem 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 chan- nel 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 excessively 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. Inlet/Outlet Inlet/outlet areas  clogged with sediment 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 channelization, 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,  overseed 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-A.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 filtration, OR veget- ation is crowded out  by very dense clumps of cattail, which do not allow water to  flow through the  clumps. Determine cause of  lack of vigor of vegetation and correct. Replant as needed. For excessive  cattail growth, cut cattail shoots  back and compost off-site. Note: normally wetland vegetation does not need  to be harvested unless die-back is causing oxygen  depletion in downstream  waters.  Inlet/Outlet Inlet/outlet area  clogged with sediment and/or debris.Remove clogging or  blockage in the inlet and outlet areas. Trash and Debris   Accumulation See Table V-A.1: Maintenance Standards - Detention Ponds Remove trash and  debris from wet swale. Erosion/Scouring Swale has eroded  or scoured due to flow channelization, or higher flows. Check design flows  to assure swale is large enough to handle flows. By-pass excess flows or  enlarge swale. Replant eroded  areas with fibrous-rooted plants such as Juncus  effusus (soft rush) in wet areas or snowberry (Symphoricarpos albus) in dryer   areas. Table V-A.9: Maintenance Standards - Wet Biofiltration Swale 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1011 A-7 Maintenance Com- ponent Recommended Frequency a Condition when Maintenance is Needed (Stand- ards)Action Needed (Procedures) 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,  vegetation, erosion control matting) l For deep channels or cuts (over 3  inches in ponding depth), temporary erosion control measures should be put in  place until permanent 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 reassessed: (1) flow volumes from  contributing areas and bioretention facility sizing; (2) flow velocities and  gradients within the facility; and (3)flow dissipation and erosion  protection strategies at the facility inlet. A Erosion of sides causes slope to become a hazard Take actions to eliminate the hazard and stabilize slopes A, S Settlement greater than 3 inches (relative to undis- turbed  sections of berm)Restore to design height A, S Downstream face of berm wet, seeps or leaks evid- ent Plug any holes and compact berm (may require consultation with  engineer, 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 compact (may  require consultation with engineer, particularly for larger berms) Concrete sidewalls A Cracks or failure of concrete sidewalls l Repair/ seal cracks l Replace if repair is insufficient Rockery sidewalls A Rockery side walls are insecure Stabilize rockery sidewalls (may require consultation with  engineer, particularly for walls 4 feet or greater in height) Facility area All maintenance vis- its (at least bian- nually) Trash and debris present Clean out trash and debris Facility bottom area A, S Accumulated sediment to extent that infiltration rate  is  reduced (see "Ponded water") or surface storage  capacity significantly  impacted l Remove excess sediment l Replace any vegetation damaged or  destroyed by sediment accumulation and removal l Mulch newly planted  vegetation l Identify and control the sediment  source (if feasible) l If accumulated sediment is  recurrent, consider adding presettlement 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 permeability  check dams  and weirs A, S Sediment, vegetation, or debris accumulated at or  blocking (or  having the potential to block) check dam,  flow control weir or orifice Clear the blockage A, S Erosion and/or undercutting present Repair and take preventative measures to prevent future erosion  and/or undercutting A Grade board or top of weir damaged or not level Restore to level position Table V-A.21: Maintenance Standards - Bioretention Facilities 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1019 A-8 Maintenance Com- ponent Recommended Frequency a Condition when Maintenance is Needed (Stand- ards)Action Needed (Procedures) Inspection Routine Main- tenance Ponded water B, S Excessive ponding 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 infiltration. If necessary, remove  leaf lit- ter/debris. 2.Ensure that underdrain (if  present) is not clogged. If necessary, clear underdrain. 3.Check for other water inputs  (e.g., groundwater, illicit connections). 4.Verify that the facility is sized  appropriately for the contributing area. Confirm that the contributing area  has not increased.     If steps #1-4 do not solve the problem, the bioretention soil is likely  clogged by sediment accumulation at the surface or has become overly  compacted. Dig a small hole to observe soil profile and identify compaction  depth or clogging front to help determine the soil depth to be removed or  otherwise rehabilitated (e.g., tilled). Consultation with an engineer is  recommended. Bioretention soil mix As needed Bioretention soil mix protection is needed when per- forming  maintenance requiring entrance into the facil- ity footprint l Minimize all loading in the facility  footprint (foot traffic and other loads) to the degree feasible in order to  prevent com- paction of bioretention soils. l Never drive equipment or apply  heavy loads in facility footprint. l Because the risk of compaction is  higher during saturated soil conditions, any type of loading in the cell  (including foot traffic) should be minimized during wet conditions.  l Consider measures to distribute loading if heavy foot traffic is required  or equipment must be placed in facility. As an example, boards may be placed  across soil to distribute loads and minimize compaction. l If compaction occurs, soil must be loosened or otherwise 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 is fore- casted Weekly during fall  leaf drop Accumulated leaves at curb cuts Clear leaves (particularly important for key inlets and low  points along long, linear facilities) Pipe inlet/outlet A Pipe is damaged 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 prevent future blockages 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 vegetation  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 Table V-A.21: Maintenance Standards - Bioretention Facilities (continued) 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1020 A-9 Maintenance Com- ponent Recommended Frequency a Condition when Maintenance is Needed (Stand- ards)Action Needed (Procedures) Inspection Routine Main- tenance Erosion control at inlet A Concentrated flows are causing 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 cut or swale) Trash rack S Trash or other debris present on trash rack Remove/dispose A Bar screen damaged or missing Repair/replace Overflow A, S Capacity reduced by sediment or debris Remove sediment or debris/dispose Underdrain pipe Clean pipe as  needed Clean orifice at  least biannually  (may need more fre- quent  cleaning     dur- ing wet season) l Plant roots, sediment or debris reducing  capa- city of underdrain l Prolonged surface ponding (see "Ponded water" l Jet clean or rotary cut debris/roots from  underdrain(s) l If underdrains are equipped with a  flow restrictor (e.g., orifice) to attenuate flows, the orifice must be cleaned  regularly. Vegetation Facility bottom area  and upland slope  veget- ation Fall and Spring Vegetation survival rate falls below 75% within first  two years  of establishment (unless project O&M  manual or record drawing stipulates  more or less than  75% survival rate). l Determine cause of poor vegetation growth  and correct condition l Replant as necessary to obtain 75%  survival rate or greater. Refer to original planting plan, or approved  jurisdictional species list for appropriate plant replacements (See Appendix  3 - Bioretention Plant List, in the LID Technical Guid- ance Manual for Puget Sound, (Hinman and Wulkan, 2012)). l Confirm that plant selection is  appropriate for site growing conditions l Consultation with a landscape  architect is recommended for removal, transplant, or substitution of plants Vegetation (general)As needed Presence of diseased plants and plant material l Remove any diseased plants or plant parts  and dispose of in an approved location (e.g., commercial landfill) to avoid risk of spreading the disease to other plants l Disinfect gardening tools after  pruning to prevent the spread of disease l See the Pacific Northwest Plant Disease Management Handbook (Pscheidt and Ocamb, 2016) for information on dis- ease recognition and for  additional resources l Replant as necessary according to  recommendations provided for "facility bottom area and upland slope  vegetation". Trees and  shrubs All pruning seasons      (timing 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 performed 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 maintenance l Prune trees and shrubs using most current  ANSI A300 standards and ISA BMPs. l Remove trees and shrubs, if  necessary. Fall and Spring Standing dead vegetation is present l Remove standing dead vegetation l Replace dead vegetation within 30  days of reported dead and dying plants (as practical depending on  weather/planting season) l If vegetation replacement is not  feasible within 30 days, and absence of vegetation 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 possible Table V-A.21: Maintenance Standards - Bioretention Facilities (continued) 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1021 A-10 Maintenance Com- ponent Recommended Frequency a Condition when Maintenance is Needed (Stand- ards)Action Needed (Procedures) Inspection Routine Main- tenance l If specific plants have a high  mortality rate, assess the cause and replace with appropriate species.  Consultation with a landscape architect is recommended. Fall and Spring Planting beneath mature trees l When working around and below mature trees,  follow the most current ANSI A300 standards and ISA BMPs to the extent  practicable (e.g., take care to minimize any damage to tree roots and avoid  compaction of soil). l Planting of small shrubs or  groundcovers beneath mature trees may be desirable in some cases; such  plantings should use mainly plants that come as bulbs, bare root or in 4-inch  pots; plants should be in no larger than 1-gallon con- tainers. Fall and Spring Presence of or need for stakes and guys (tree growth,   maturation, and support needs) l Verify location of facility liners and  underdrain (if any) prior to stake installation in order to prevent liner  puncture or pipe damage l Monitor tree support systems:  Repair and adjust as needed to provide support and prevent damage to  tree. l Remove tree supports (stakes,  guys, etc.) after one growing season or maximum of 1 year. l Backfill stake holes after  removal. Trees and shrubs adja- cent to vehicle travel  areas (or areas where   visibility needs to be  maintained) A Vegetation causes some visibility (line of sight) or  driver  safety issues l Maintain appropriate height for sight  clearance l When continued, regular pruning  (more than one time/ growing season) is required to maintain visual sight  lines for safety or clearance along a walk or drive, consider relocating the  plant to a more appropriate location. l Remove or transplant if continual  safety hazard l Consultation with a landscape  architect is recommended for removal, transplant, or substitution of 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 compromises conveyance 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  (perennial)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  (evergreen)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 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,  preceding seed dis- persal) 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 disposed as garbage immediately l Reasonable attempts must be made  to remove and dispose of class C noxious weeds l It is strongly encouraged 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, Weeds are present l Remove weeds with their roots manually with  pincer-type weeding tools, flame weeders, or hot water weeders as Table V-A.21: Maintenance Standards - Bioretention Facilities (continued) 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1022 A-11 Maintenance Com- ponent Recommended Frequency a Condition when Maintenance is Needed (Stand- ards)Action Needed (Procedures) Inspection Routine Main- tenance preceding seed dis- persal) appropriate l Follow IPM protocols for weed management (see "Additional Maintenance 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 vegetation growing beyond facility edge  onto  sidewalks, paths, or street edge poses ped- estrian safety hazard or may clog  adjacent permeable pavement surfaces due to associated leaf litter,  mulch,  and soil  l Edge or trim groundcovers 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 clippings can be left in the facility to replenish organic material in the soil, excessive leaf litter can cause surface soil clogging As needed Excessive vegetation density inhibits stormwater  flow beyond design ponding or becomes a hazard for  pedestrian and vehicular circulation and safety l Determine whether pruning or other routine maintenance is adequate to maintain proper plant density and aesthetics l Determine if planting type should be replaced to avoid ongoing maintenance issues (an aggressive grower under per- fect growing conditions should be transplanted 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 leaving 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  sediment  buildup and flow bypass Remove vegetation and sediment buildup 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 arborist  wood chips are used on side slopes and rim (above typical water levels) l Keep all mulch away from woody  stems Watering Irrigation system (if  any) Based on man- ufacturer's instruc- tions Irrigation system present Follow manufacturer's instructions for  O&M A Sprinklers or drip irrigation not directed/located to  properly  water plants Redirect sprinklers or move drip irrigation  to desired areas Summer watering     (first  year) Once every 1-2  weeks or as needed  during prolonged  dry periods Trees, shrubs and groundcovers 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 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 system is not present o Pulse water to enhance soil absorption, when feasible Table V-A.21: Maintenance Standards - Bioretention Facilities (continued) 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1023 A-12 Maintenance Com- ponent Recommended Frequency a Condition when Maintenance is Needed (Stand- ards)Action Needed (Procedures) Inspection Routine Main- tenance o Pre-moisten soil to break surface tension of dry or hydrophobic  soils/mulch, followed by several more passes. With this method , each pass  increases soil absorption and allows more water to infiltrate prior to  runoff l Add a tree bag or slow-release  watering device (e.g., bucket with a perforated bottom) for watering newly  installed trees when irrigation system is not present Summer watering  (second and third  years) Once every 2-4  weeks or as needed  during prolonged  dry periods Trees, shrubs and groundcovers in second or third  year of  establishment 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 system is not present o Pulse water to enhance soil  absorption, when feasible o Pre-moisten soil to break surface  tension of dry or hydrophobic soils/mulch, followed by several more passes. With this method , each pass increases soil absorption and allows more water  to infiltrate prior to runoff Summer watering      (after establishment)As needed Established vegetation (after 3 years) l Plants are typically selected to be drought  tolerant and not require regular watering after establishment; however, trees  may take up to 5 years of watering to become fully established l Identify trigger mechanisms for  drought-stress (e.g., leaf wilt, leaf senescence, etc.) of different species  and water immediately after initial signs of stress appear l Water during drought conditions or  more often if necessary to maintain 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 maintenance,  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-generating surfaces) after get- ting approval from  sanitary sewer authority. l Use of pesticides or Bacillus thuringiensis israelensis   (Bti) may be considered only as a temporary measure while addressing the  standing water cause. If overflow to a surface water will occur within 2  weeks after pesticide use, apply for coverage under the Aquatic Mosquito  Control NPDES General Permit. Nuisance animals As needed Nuisance animals causing erosion, damaging plants,  or  depositing large volumes of feces l Reduce site conditions 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 protocols for specific nuisance animal issues (see "Additional Maintenance Resources" section for more information on IPM protocols) l Remove pet waste regularly l For public and right-of-way sites  consider adding garbage cans with dog bags for picking up pet waste. Insect pests Every site visit  associated with  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, follow IPM protocols (see "Additional Maintenance Resources"  section for more information on IPM Table V-A.21: Maintenance Standards - Bioretention Facilities (continued) 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1024 A-13 Maintenance Com- ponent Recommended Frequency a Condition when Maintenance is Needed (Stand- ards)Action Needed (Procedures) Inspection Routine Main- tenance vegetation man- agement protocols) Note that the inspection and routine maintenance frequencies listed above are recommended by Ecology. They do not supersede or replace the municipal stormwater permit requirements for inspection frequency required of municipal stormwater per- mittees 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-A.21: Maintenance Standards - Bioretention Facilities (continued) Component Recommended Frequency a Condition when Maintenance is Needed (Standards)Action Needed (Procedures) Inspection Routine Maintenance Surface/Wearing Course Permeable     Pave- ments, all A, S Runoff from adjacent pervious areas deposits  soil, mulch or  sediment on paving l Clean deposited soil or other materials  from permeable pavement or other adjacent surfacing l Check if surface elevation of  planted area is too high, or slopes towards pavement, and can be regraded  (prior to regrading, protect permeable pavement by covering with temporary  plastic and secure covering in place) l Mulch and/or plant all exposed  soils that may erode to pavement surface Porous asphalt or per- vious  concrete A or B None  (routine maintenance) Clean  surface debris from pavement surface using one or a combination of the  following methods:  l Remove sediment, debris, trash,  vegetation, and other debris deposited onto pavement (rakes and leaf blowers can  be used for removing leaves) l Vacuum/sweep permeable paving installation using: o Walk-behind vacuum (sidewalks) o High efficiency regenerative air or vacuum sweeper (roadways, parking lots) o ShopVac or brush brooms (small areas) l Hand held pressure washer or  power washer with rotating brushes     Follow equipment manufacturer guidelines for when equipment is most  effective for cleaning permeable pavement. Dry weather is more effective for some equipment. Ab Surface is clogged:     Ponding on surface or water  flows off the permeable pavement surface dur- ing  a rain event (does not infiltrate) l Review the overall performance of the  facility (note that small clogged areas may not reduce overall per- formance of  facility) l Test the surface infiltration  rate using ASTM C1701 as a corrective maintenance indicator. Perform one test per installation, up to 2,500 square feet. Perform an additional test for  each additional 2,500 square feet up to 15,000 square feet total. Above  15,000 square feet, add one test for every 10,000 square feet. l If the results indicate an  infiltration rate of 10 inches per hour or less, then perform corrective  maintenance to restore permeability. To clean clogged pavement surfaces, use  one or combination of the following  methods: Table V-A.22: Maintenance Standards - Permeable Pavement 2019 Stormwater Management Manual for Western Washington Volume V -Appendix A -Page 1025 A-14 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. B-14 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: B-15 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. B-16 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 B-17 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. B-18