Stormwater Facility

Maintenance Manual BG02.02

March 2019

Public Works Department Engineering Division 109 SW 1st Street, Suite #122 Battle Ground, WA 98604

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Table of Contents

INTRODUCTION ...... 1 CATCH BASIN ...... 7 MANHOLE ...... 13 DETENTION TANKS AND VAULTS ...... 15 CONTROL STRUCTURE/FLOW RESTRICTOR ...... 17 TRASH SCREEN ...... 19 ENERGY DISSIPATER ...... 21 BIOFILTRATION SWALE ...... 23 WET BIOFILTRATION SWALE ...... 25 STORMWATER TREATMENT WETLAND ...... 27 FILTER STRIP ...... 29 WETPOND ...... 31 SAND FILTER ...... 35 STORMWATER MEDIA FILTER ...... 37 OIL/WATER SEPARATOR ...... 39 VORTEX SEDIMENTATION VAULT ...... 41 BIOSWALE SEDIMENTATION TRAP ...... 43 FIELD/AREA INLET...... 45 ACCESS ROAD AND EASEMENT ...... 47 FENCE, GATE, AND/OR WATER QUALITY SIGN ...... 49 CONVEYANCE STORMWATER PIPE ...... 51 CONVEYANCE DITCH...... 53 STORMWATER FACILITY DISCHARGE POINTS ...... 55 TREE BOX FILTERS ...... 57 VEGETATION MANAGEMENT ...... 59 LOW IMPACT DEVELOPMENT (LID) BMPS ...... 61 BIORETENTION FACILITIES ...... 63 RAIN GARDENS ...... 73 DOWNSPOUT, SHEET FLOW, AND CONCENTRATED DISPERSION SYSTEMS ...... 77 COMPOST-AMENDED SOILS ...... 81 PERMEABLE PAVEMENT ...... 85 PERFORATED STUB-OUT CONNECTION ...... 91

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Introduction

Background

Nearly all development, whether residential, commercial or industrial, has some form of stormwater drainage facilities. These stormwater facilities drain to the City of Battle Ground storm sewer system and then to our local waterways. Newer developments include structures such as grassy treatment swales, ponds, oil/water separators, and other structures to control or treat stormwater.

Requirements from the Washington State Department of Ecology and the Clean Water Act require the City to comply with rules to protect our water resources by ensuring that storm drainage facilities are properly operated and maintained. This manual describes the steps you can take to assure that your storm facilities meet water quality requirements.

Purpose

This manual is intended to cover most public and private stormwater facility operation and maintenance requirements under Battle Ground Municipal Code 18.250, the City’s NPDES Phase II permit, and the Stormwater Management Manual for Western Washington: Volume II (Washington Department of Ecology, December 2014).

Drainage systems are often in or near areas that are also wildlife habitat. This manual helps make sure that storm facility owners perform their maintenance in a way that conforms to regulations protecting wildlife.

Why Maintain Storm Facilities?

In addition to keeping the site from flooding, properly maintained storm facilities can help protect streams, lakes, wetlands, and groundwater. Proper maintenance helps assure that storm facilities operate as they were designed and that they are cleaned of the pollutants that they trap.

Method for Creating this Manual

This manual draws on other maintenance manuals including the Clark County Stormwater Facilities Maintenance Manual (January 2009), Stormwater Management Manual for Western Washington and the Pierce County Stormwater Maintenance Manual for Private Facilities (2005).

The Low Impact Development portion of this manual draws on the Guidance Document – Western Washington Low Impact Development (LID) Operation and Maintenance (O&M) prepared for the Washington State Department of Ecology Water Quality

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Program by Herrera Environmental Consultants, Inc. and Washington Stormwater Center (May 2013).

Emergent Treatment Technologies

Volume V, Chapter 12 of the Western Washington Manual addresses emerging treatment technologies. Since emerging technologies are rapidly evolving and it is not practical to update the manual every time a new device comes out, the Technology Assessment Protocol - Ecology (TAPE) was created as guidance for evaluating emerging stormwater treatment technologies. The TAPE can be found online at https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater- permittee-guidance-resources/Emerging-stormwater-treatment-technologies.

Ecology assigns a General Use Level Designation (GULD) on emergent technologies that may be used. Maintenance standards in GULD approvals for emergent technologies not found in this Maintenance Manual are adopted by reference and can be found at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/technologies.html.

Spill Reporting

The City of Battle Ground Municipal Code requires all spills to the storm sewer system or areas that drain to the storm sewer system to be reported.

In the event of a release of hazardous materials, the City of Battle Ground Department of Public Works and emergency response agencies shall be notified IMMEDIATELY of the occurrence via emergency dispatch services (911).

In the event of a release of non-hazardous materials, the City of Battle Ground Department of Public Works shall be notified in person at 109 SW 1st St or by phone at (360) 342-5070 or facsimile at (360) 342-5057 no later than the next business day. Notifications in person or by phone shall be confirmed by written notice addressed and mailed to the Department within three business days of the phone notice.

Spills shall also be reported to the Washington State Department of Ecology South West Regional office at (360) 407-6300.

If the discharge of materials emanated from a commercial or industrial establishment, the owner or operator of the establishment is required to retain an on-site written record of the discharge and the actions taken to prevent its recurrence. These records must be retained for at least three years.

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Detention Pond

A stormwater detention pond is an open basin built by excavating, or by constructing above- ground berms or embankments. The detention pond temporarily stores stormwater runoff during rain events and slowly releases it through a control structure. Detention pond styles can vary greatly from well-manicured to natural appearing. Generally, native vegetation is preferred for reduced maintenance and enhanced wildlife habitat. Some facilities are designed to appear as natural water bodies or are in park-like areas.

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Detention Pond – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Trash and Any trash and debris which exceed five cubic Remove trash and debris. General Debris feet per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping.

Poisonous Any poisonous or nuisance vegetation which Remove poisonous or nuisance vegetation. Vegetation may constitute a hazard. Remove noxious weeds. Comply with State or and Noxious local eradication policies. Weeds Evidence of noxious weeds as defined by State or local regulations. Contaminants Any evidence of oil, gasoline, contaminants or No evidence contaminants or pollutants and Pollution other pollutants beyond typical levels. present.

For major spills coordinate removal/cleanup with the Department of Ecology at (360) 407-6300. Rodent Holes Any evidence of rodent holes on berm, or any Rodents eliminated and berm repaired. evidence of water piping through berm via (Coordinate with Ecology Dam Safety Office if rodent holes. pond exceeds 10 acre-feet.)

Beaver Dams Dam results in impairment of facility function. Eliminate beavers. Return facility to design condition. (Coordinate trapping of beavers and removal of dams with appropriate permitting agencies.)

Insects Insects such as wasps and hornets create Insects destroyed or removed from site. problems or pose danger. Apply insecticides in compliance with state and federal requirements. Tree Growth Tree growth does not allow maintenance access Remove or trim problem trees. and Hazard or interferes with maintenance activity. Trees Hazard trees such as dead, diseased, or dying Remove hazard Trees. trees are identified.

Erosion Eroded damage over two inches deep. Stabilize slopes using appropriate permanent Side erosion control measures. Slopes of Any erosion observed on a compacted berm If erosion is occurring on compacted berms a Pond embankment. licensed Civil Engineer should be consulted to resolve source of erosion. Grass/ Grass exceeds 12 inches in height or vegetation Mow grass or trim vegetation. Vegetation growth becomes excessive.

Poor vegetation coverage. If bare areas are large (generally greater than 12 inches wide) prepare soil and reseed. For smaller bare areas, over seed or plant plugs of grass at eight inch intervals.

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Detention Pond (Continued) Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Sediment Accumulated sediment that exceeds 10% of the Remove sediment to restore designed pond Storage designed pond depth unless otherwise specified shape and depth; reseed pond if necessary to Area or affects inlet or outlet of the facility. control erosion.

Liner (If Liner is visible and has more than three 1/4 inch Repair or replace liner. Fully cover liner. Applicable) holes in it. Settlement Any part of berm which has settled four inches Repair berm to the design elevation. Pond lower than the design elevation. Berms Settling can be an indication of more severe (Dikes) problems with the berm or outlet works. A licensed Civil Engineer should be consulted to determine the source of the settlement.

Soil Piping Discernable water flow through pond berm. Repair soil piping damage and repair berm to Ongoing erosion with potential for erosion to eliminate soil piping condition. continue.

(It is recommended that a Civil engineer is consulted to inspect and evaluate condition of the berm and recommend repair procedure.) Tree Tree growth on emergency spillways creates Remove Trees. If root system is small (base Growth blockage problems and may cause failure of the less than four inches) the root system may be berm due to uncontrolled overtopping. left in place. Otherwise the roots should be removed and the berm restored. A licensed Civil Tree growth on berms over four feet in height may Engineer should be consulted for proper lead to piping through the berm which could lead berm/spillway restoration. to failure of the berm. Rock Only one layer of rock exists above native soil in Restore rocks and pad depth to design Emergency Missing area five square feet or larger, or any exposure of standards. Overflow/ native soil at the top of out-flow path of spillway. Spillway Erosion Eroded damage over two inches deep. Stabilize slopes using appropriate permanent erosion control measures. Any erosion observed on a compacted berm If erosion is occurring on compacted berms a embankment. licensed Civil Engineer should be consulted to resolve source of erosion.

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Catch Basin

A catch basin is an underground concrete structure to collect stormwater runoff and route it through underground pipes. Catch basins are sometimes used as a junction in a pipe system and in some cases may have a solid lid.

Catch basins typically provide a sump below the outlet pipe to allow sediment and debris to settle out of the stormwater runoff. Some catch basins are also fitted with a spill control device such as an inverted elbow on the outlet pipe to contain large quantities of grease or oils. The most common tool for cleaning catch basins is a vactor truck which is used to remove sediment and debris from the sump.

Catch Basins are enclosed spaces where harmful chemicals and vapors can accumulate. Therefore, the inspection and maintenance of these facilities should be conducted by an individual trained and certified to work in hazardous confined spaces.

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Catch Basins – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Trash and Trash or debris which is located immediately in Remove trash or debris. General Debris front of the catch basin opening or is blocking inletting capacity of the basin.

Trash or debris has accumulated to within six Remove trash or debris. inches of the invert of the lowest pipe.

Trash or debris in any inlet or outlet pipe blocking Remove trash or debris. more than 1/3 of its height. Dead animals or vegetation that could generate Remove dead animals or vegetation. odors that could cause complaints or dangerous gases (e.g., methane). Sediment Sediment has accumulated to within six inches of Remove sediment from catch basin. the invert of the lowest pipe or to within 4 inches of the spill control device. Structure Top slab has holes larger than two square inches Repair or replace top slab. Damage to or cracks wider than 1/4 inch. Frame and/or Top Slab Frame not sitting flush on top slab. Repair or replace frame.

Separation of more than 3/4 inch of the frame from the top slab. Frame not securely attached. Fractures or Structure is unsound. Repair or replace basin. Cracks in Grout has separated or cracked wider than 1/2 Re-grout and secure pipe at basin wall. Basin Walls/ inch and longer than one foot at the joint of any Bottom inlet/outlet pipe or any evidence of soil particles or ground water entering catch basin through cracks. Settlement/ Basin has settled or become misaligned creating Repair or replace basin. Misalignment a safety, function, or design problem. Vegetation Vegetation growing across and blocking the basin Remove vegetation. opening.

Contaminants Any evidence of oil, gasoline, contaminants or No evidence contaminants or pollutants present. and Pollution other pollutants beyond typical levels.

For major spills coordinate removal/cleanup with the Department of Ecology at (360) 407-6300. Spill Control Spill control device missing or damaged. Repair or replace spill control device to design Device specifications.

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Catch Basins (Continued) Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Cover No cover present on structure. Replace cover. Catch Missing Basin Cover Locking Mechanism cannot be opened by one Repair mechanism so that it operates correctly. Mechanism maintenance person with proper tools. Bolts into Not frame have less than 1/2 inch of thread. Working Cover One maintenance person cannot remove lid after Repair cover. Difficult to applying normal lifting pressure. Remove Grate Grate missing or has opening wider than 7/8 inch. Repair or replace grate to design standards. Metal Damaged Grates or Missing

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Manhole

A manhole is an underground structure to allow access to conveyance pipes for maintenance and inspection purposes. Manholes are used in storm sewer main lines at any change in direction, slope, pipe material or pipe size.

Storm manholes typically provide a storage volume (sump) below the inlet and outlet pipes to allow sediment and debris to settle out of the stormwater runoff. Some manholes are also fitted with stormwater flow control structures such as orifices or weirs.

Manholes are enclosed spaces where harmful chemicals and vapors can accumulate. Therefore, the inspection and maintenance of these facilities should be conducted by an individual trained and certified to work in hazardous confined spaces.

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Manhole – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Trash and Trash or debris in any inlet or outlet pipe Remove trash or debris. General Debris blocking more than 1/3 of its height. Trash or debris has accumulated to within six Remove trash or debris. inches of the invert of the lowest pipe. Sediment Sediment has accumulated to within six inches Remove sediment. of the invert of the lowest pipe. Structure Top slab has holes larger than two square Repair or replace top slab. Damage to inches or cracks wider than 1/4 inch. Frame and/or Top Slab Frame not sitting flush on top slab. Repair or replace frame.

Separation of more than 3/4 inch of the frame from the top slab. Frame not securely attached. Fractures or Structure is unsound. Repair or replace manhole. Cracks in Grout has separated or cracked wider than 1/2 Re-grout and secure pipe at manhole wall. Structure inch and longer than one foot at the joint of any Walls/ Bottom inlet/outlet pipe or any evidence of soil particles or ground water entering manhole through cracks. Settlement/ Manhole has settled or become misaligned Repair or replace manhole. Misalignment creating a safety, function, or design problem. Cover Not in Cover is missing or only partially in place. Any Replace cover. Cover Place open manhole requires maintenance.

Locking Mechanism cannot be opened by one Repair or replace locking mechanism or lid. Mechanism maintenance person with proper tools. Bolts Not Working into frame have less than 1/2 inch of thread (may not apply to self-locking lids). Cover Difficult One maintenance person cannot remove lid Repair cover. to Remove after applying normal lifting pressure. Intent is to keep cover from sealing off access to maintenance. Ladder Rungs Ladder is corroded or deteriorated, has sharp Repair or replace ladder to design Ladder Unsafe edges, is not securely attached to structure specifications. wall, missing rungs, cracked, or misaligned. Control Structure/ See Control Structure/Flow Restrictor requirements. Flow Restrictor

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Detention Tanks and Vaults

A closed detention system functions similarly to a detention pond but with the storage volume provided by an underground structure. The structure is typically constructed of large diameter pipe, plastic chamber structure or a concrete vault. These systems are typically utilized for sites that do not have space available for an above-ground system and are more commonly associated with commercial sites.

Underground detention systems are enclosed spaces where harmful chemicals and vapors can accumulate. Therefore, the inspection and maintenance of these facilities should be conducted by an individual trained and certified to work in hazardous confined spaces.

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Detention Tanks and Vaults – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Plugged More than 1/2 of the cross section of a vent is Unplug or repair vent. Detention Air Vents blocked at any point or the vent is damaged. Tank Debris and Accumulated sediment depth exceeds 10% of the Remove all sediment and debris from storage Sediment height of the storage area for 1/2 length of storage area. vault or any point depth exceeds 15% of diameter.

(Example: 72 inch diameter storage tank would require cleaning when sediment reaches depth of seven inches for more than 1/2 length of tank.)

Joints Any openings or voids allowing soil or ground Repair all joints between tank/pipe sections. Between water to enter facility. Tank/Pipe Section Tank/Pipe Any part of tank/pipe is bent out of shape more Repair or replace tank/pipe to design Bent Out of than 10% of its design shape. (Review required by specifications. Shape engineer to determine structural stability).

Damage to Cracks wider than 1/2 inch and any evidence of Replace or repair vault to design specifications. Vault soil particles or ground water entering the structure Vault is structurally sound. Structure through the cracks. Vault is not structurally sound.

Cover No cover present on structure. Replace cover. Cover Missing Locking Mechanism cannot be opened by one Repair mechanism so that it operates correctly. Mechanism maintenance person with proper tools. Bolts into Not frame have less than 1/2 inch of thread. Working Cover One maintenance person cannot remove lid after Repair cover. Difficult to applying normal lifting pressure. Remove Ladder Ladder is corroded or deteriorated, has sharp Repair or replace ladder to design Rungs edges, is not securely attached to structure wall, specifications. Unsafe missing rungs, cracked, or misaligned.

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Control Structure/Flow Restrictor

Flow control structures, also known as flow restrictors, direct or restrict flow in to or out of facility components. The flow is regulated by a combination of orifices and/or weirs. Lack of maintenance of the control structure can result in the plugging of an orifice or weir. If these flow controls are damaged, plugged, bypassed, or not working properly, the facility could overtop or release water too quickly potentially damaging streams, habitat, and property.

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Control Structure/Flow Restrictor – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Trash, Material has accumulated to within one foot of Remove all sediment and debris. General Debris and below orifice plate or weir. Sediment Structural Flow control structure is not securely attached Repair structure support. Damage to manhole wall. Structure is not in upright position. Repair structure to correct position.

Connections to outlet pipe are not watertight. Repair connections to outlet pipe to water tight; structure repaired or replaced and works as designed. Damage to flow control structure. Repair or replace flow control structure.

Damaged or Cleanout gate is not watertight or is missing. Repair or replace gate to design specifications. Cleanout Missing Gate Gate cannot be moved up and down by one Repair gate. maintenance person. Chain/rod leading to gate is missing or Repair or replace chain or rod. damaged. Plate Control device is not working properly due to Repair or replace plate to design specifications. Orifice or Damaged or missing, out of place, or bent plate. Weir Plate Missing Obstructions Any trash, debris, sediment, or vegetation Remove all sediment and/or debris. blocking the plate. Overflow Obstructions Any trash or debris blocking (or having the Remove all trash and debris. Pipe potential of blocking) the overflow pipe.

Manhole See Manhole requirements

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Trash Screen

A trash screen is a grate over the open end of a culvert or stormwater conveyance pipe. Their function is to prevent debris and unauthorized access into the storm conveyance pipe. Trash screens are required on open pipe ends that exceed 15 inches in diameter. Only qualified personnel should attempt to maintain or remove debris from the barrier when water is flowing through the conveyance pipe.

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Trash Screen – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature Trash and Trash or debris that is plugging more than 20% Clear trash or debris to restore design flow General Debris of the openings. capacity.

Damaged/ Bars are bent out of shape more than three Repair or replace bars. Missing inches. Bars. Bars are missing. Repair or replace bars. Bars are loose. Repair or replace bars.

Missing Trash screen missing or not attached to pipe. Repair or replace trash screen. Trash Screen Lock Lock is not present or does not operate Repair or replace lock. Lock and Missing or correctly. Hinges Damaged Cover One maintenance person cannot open trash Repair hinges. Difficult to screen barrier using hinges after applying Open normal lifting pressure.

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Energy Dissipater

An energy dissipater is installed at the outlet of a closed pipe system to prevent erosion. Energy dissipaters can be made from rip rap or concrete. Rip rap energy dissipaters are constructed of three to eight inch diameter rocks and are lined with filter fabric. The rip rap pad should extend past the end of the pipe a minimum of six times the diameter of the pipe.

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Energy Dissipaters – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Missing or Only one layer of rock exists above native soil Replace rip rap to design standards. Rip Rap Moved in area five square feet or larger, or any Rock exposure of native soil.

Erosion Soil erosion in or adjacent to rip rap. Replace rip rap to design standards. Repair erosion and permanently stabilize area around pad. Structural Slab has holes larger than two square inches Repair or replace pad. Concrete Damage to or cracks wider than 1/4 inch. Pad Pad Erosion Soil erosion adjacent to concrete pad. Repair erosion and permanently stabilize area around pad.

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Biofiltration Swale

A biofiltration swale uses grass or other dense vegetation to filter sediment and pollutants out of stormwater. They often look like flat-bottomed channels with grass or landscaping in them. Biofiltration uses vegetation in conjunction with slow and shallow-depth flow for runoff treatment. As runoff passes through the vegetation, pollutants are removed through the combined effects of filtration, infiltration, and settling. These effects are aided by the reduction of the velocity of stormwater as it passes through the swale.

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Biofiltration Swale – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Sediment Sediment inhibits grass growth in greater Remove sediment deposits on grass treatment General Accumulation than 10% of the swale. area of the bio-swale. When finished, swale on Grass should be level from side to side and drain freely Sediment is blocking entry and distribution of toward outlet. There should be no areas of water in swale. standing water once inflow has ceased. Re- vegetate if necessary. Standing Standing water in the swale between storms Repair cause of poor drainage. This may include, Water due to swale not draining freely. but is not limited to the following activities: remove sediment or trash blockages, improve grade from head to foot of swale, remove clogged check dams, add under-drains or convert to a wet biofiltration swale. Flow spreader Flow spreader uneven or clogged so that Level the spreader and/or clean so that flows are flows are not uniformly distributed through spread evenly over entire swale width. entire swale width. Constant Small quantities of water continually flow Eliminate source of baseflow. If not possible add Baseflow through the swale, even when it has been a low-flow pea-gravel drain the length of the dry for weeks, and an eroded, muddy swale. channel has formed in the swale bottom.

Poor Grass is sparse or bare or eroded patches Determine why grass growth is poor and correct Vegetation occur in more than 10% of the swale bottom. that condition. Replant with plugs of grass from Coverage the upper slope or reseed. Vegetation Grass is excessively tall (greater than six Mow vegetation and/or remove nuisance and Grass inches). vegetation so that flow is not impeded. Grass should be mowed to a height of three to four Nuisance weeds and other vegetation start inches. to take over swale. Excessive Grass growth is poor because sunlight does If possible, trim back over-hanging limbs and Shading not reach swale. remove brushy vegetation on adjacent slopes.

Tree Growth Trees are present in swale. Remove trees.

Inlet/Outlet Inlet/outlet areas clogged with sediment Remove material so that there is no clogging or and/or debris. blockage in the inlet and outlet area. Trash and Any trash and debris which exceed five cubic Remove trash and debris from bioswale. Debris feet per 1,000 square feet (this is about Accumulation equal to the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping. Erosion/ Eroded or scoured swale bottom due to flow If bare areas are large (generally greater than 12 Scouring channelization, or higher than design flows. inches wide) the swale should be re-graded and reseeded. For smaller bare areas, over seed or plant plugs of grass in the swale at eight inch intervals.

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Wet Biofiltration Swale

A wet biofiltration swale is a variation of a basic biofiltration swale for use where there is minimal slope, groundwater tables are high, or a continuous low base flow is likely to result in wet soil conditions for long periods of time. Where constant moist conditions are present vegetation specifically adapted to wet soil conditions are required.

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Wet Biofiltration Swale – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Sediment Sediment inhibits plant growth in greater Remove sediment deposits in treatment area. General Accumulation than 10% of the swale. When finished, swale should be level from side to side and drain freely toward outlet. Re- Sediment is blocking entry and distribution vegetate if necessary. of water in swale. Wetland Wetland vegetation becomes sparse and Determine cause of lack of vigor of wetland Vegetation does not provide adequate filtration. vegetation and correct. Wetland vegetation is crowded out by Remove weeds. Replant wetland vegetation as weeds. needed. Cattail Dense clumps of cattail, which does not Remove and control cattails. Cat tails may be Growth allow water to pass. controlled by cutting or pulling cattail shoots below water level, or by other methods. Compost cattail debris off-site. Inlet/Outlet Inlet/outlet area clogged with sediment Remove clogging or blockage in the inlet and and/or debris. outlet areas.

Trash and Any trash and debris which exceed five Remove trash and debris from wet swale. Debris cubic feet per 1,000 square feet (this is Accumulation about equal to the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping. Erosion/ Swale has eroded or scoured due to flow Check design flows to assure swale is large Scouring channelization, or high flows. enough to handle flows. Replant eroded areas with fibrous-rooted plants such as Juncus effusus (soft rush) in wet areas or snowberry (Symphoricarpos albus) in dryer areas.

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Stormwater Treatment Wetland

A stormwater treatment wetland is a shallow man-made pond that is designed to treat stormwater through the biological processes associated with emergent aquatic plants. These facilities use dense wetland vegetation and settling to filter sediment and pollutants out of stormwater.

Stormwater treatment wetlands are used to capture pollutants in a managed environment so that they will not reach natural wetlands and other ecologically important habitats. Vegetation must occasionally be maintained and sediment removed from the treatment wetland.

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Stormwater Treatment Wetland – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Sediment Sediment accumulation exceeds design Remove sediment deposits. General Accumulation standards in pre-settling cell.

Sediment accumulation in wetland cell. Water Depth Water not retained during the wet season. Repair outlet so that water is retained in the treatment wetland.

Wetland Wetland vegetation becomes sparse and does Determine cause of lack of vigor of wetland Vegetation not provide adequate filtration. vegetation and correct. Replant as needed.

Nuisance plant species becomes abundant. Remove nuisance plant species and replace with appropriate species.

Cattail Dense clumps of cattail, which does not allow Remove and control cattails. Cat tails may be Growth water to pass. controlled by cutting or pulling cattail shoots below water level, or by other methods. Compost cattail debris off-site.

Trash and Any trash and debris which exceed five cubic Remove trash and debris from wetland area. Debris feet per 1,000 square feet (this is about equal Accumulation to the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping.

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Filter Strip

A filter strip is a linear strip of grass that removes sediment and pollutants from stormwater. Stormwater is treated as it runs across the filter. Usually, filter strips are placed along the edge of linear paved areas such as parking lots and roads. Where filter strips are installed, road shoulders or parking lot edges must be graded to maintain level flow off of the paved surface.

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Filter Strip – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Sediment Sediment inhibits grass growth in greater Remove sediment deposits, re-level so slope is General Accumulation than 10% of the filter strip. even and flows pass evenly through strip. on Grass Sediment is blocking entry and distribution of water in the filter strip. Vegetation When the grass becomes excessively tall Mow grass, control nuisance vegetation, such (greater than 10 inches); when nuisance that flow not impeded. Grass should be mowed weeds and other vegetation start to take to a height between 3-4 inches. over.

Trash and Any trash and debris which exceed five Remove trash and debris from filter strip. Debris cubic feet per 1,000 square feet (this is Accumulation about equal to the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping. Erosion/ Eroded or scoured areas due to flow If bare areas are large (generally greater than 12 Scouring channelization, or higher flows. inches wide) the filter strip should be re-graded and reseeded. For smaller bare areas, over seed or plant plugs of grass at eight inch intervals.

Flow Flow spreader uneven or clogged so that Level the spreader and clean so that flows are spreader flows are not uniformly distributed through spread evenly over the entire filter strip width. the entire filter strip width.

COBG Stormwater Facility Maintenance Manual Page 30 March 2019

Wetpond

A wetpond is an open basin that retains a permanent pool of water year round or in some cases only during the wet season. The volume of the wetpond allows sediment and other pollutants to settle out of the runoff. Wetland vegetation is typically planted within the wetpond to provide additional treatment through nutrient (i.e. nitrogen) removal. Detention quantity control can be provided with additional temporary storage volume above the permanent pool elevation.

Internal Berm

COBG Stormwater Facility Maintenance Manual Page 31 March 2019

Wetponds – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Trash and Any trash and debris which exceed five Remove trash and debris. General Debris cubic feet per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping. Poisonous Any poisonous or nuisance vegetation which Remove poisonous or nuisance vegetation. Vegetation may constitute a hazard. and Noxious Remove noxious weeds. Comply with State or Weeds Evidence of noxious weeds as defined by local eradication policies. State or local regulations. Tree Growth Tree growth does not allow maintenance Remove or trim problem trees. and Hazard access or interferes with maintenance Trees activity. Remove hazard Trees. Hazard trees such as dead, diseased, or dying trees are identified. Contaminants Any evidence of oil, gasoline, contaminants No evidence contaminants or pollutants present. and Pollution or other pollutants beyond typical levels. If chronic oil sheen persists, plant wetland plants such as Juncus effusus (soft rush) which can For major spills coordinate removal/cleanup uptake small concentrations of oil. with the Department of Ecology at (360) 407-6300. Erosion Eroded damage over two inches deep. Stabilize slopes using appropriate permanent erosion control measures.

Any erosion observed on a compacted berm If erosion is occurring on compacted berms a embankment. licensed Civil Engineer should be consulted to resolve source of erosion. Side Grass/ Grass exceeds 12 inches in height or Mow grass or trim vegetation. Slopes of Vegetation vegetation growth becomes excessive. Pond Poor vegetation coverage. If bare areas are large (generally greater than 12 inches wide) prepare soil and reseed. For smaller bare areas, over seed or plant plugs of grass at eight inch intervals. Rock Missing Only one layer of rock exists above native Restore rocks and pad depth to design standards. Emergency soil in area five square feet or larger, or any Overflow/ exposure of native soil at the top of out-flow Spillway path of spillway.

Water level First cell does not hold water. Repair the first cell to maintain design depth of Storage water. Area Sediment Sediment depth exceeds1.5 feet in first cell. Remove sediment from pond bottom. Sediment Accumulation should be tested for toxicants and disposed of in in Pond accordance with health department requirements. Bottom Liner (If Liner is visible and has more than three 1/4 Repair or replace liner. Fully cover liner. Applicable) inch holes in it.

COBG Stormwater Facility Maintenance Manual Page 32 March 2019

Wetpond (Continued) Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Settlement Any part of berm which has settled four Repair berm to the design elevation. Pond inches lower than the design elevation. Berms Settling can be an indication of more severe (Dikes) problems with the berm or outlet works. A licensed Civil Engineer should be consulted to determine the source of the settlement.

Internal Berm Berm is not level. Water flows over berm Level berm surface is so that water flows evenly unevenly. over entire length of berm.

Tree Growth Tree growth on emergency spillways creates Remove Trees. If root system is small (base less blockage problems and may cause failure of than four inches) the root system may be left in the berm due to uncontrolled overtopping. place. Otherwise the roots should be removed and the berm restored. A licensed Civil Engineer Tree growth on berms over four feet in height should be consulted for proper berm/spillway may lead to piping through the berm which restoration. could lead to failure of the berm. Soil Piping Discernable water flow through pond berm. Repair soil piping damage and repair berm to Ongoing erosion with potential for erosion to eliminate soil piping condition. continue.

(It is recommended that a Civil engineer is consulted to inspect and evaluate condition of the berm and recommend repair procedure.)

COBG Stormwater Facility Maintenance Manual Page 33 March 2019

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COBG Stormwater Facility Maintenance Manual Page 34 March 2019

Sand Filter

A sand filter functions by filtering stormwater through a sand bed. A typical sand filtration system consists of a pretreatment system for removing larger sediment and debris from the runoff, a flow spreader, a sand bed, and an underdrain piping. The sand filter bed typically includes a woven (geotextile) fabric between the sand bed and the underdrain system. Sand filters may be located above ground, or in a subsurface vault.

COBG Stormwater Facility Maintenance Manual Page 35 March 2019

Sand Filter – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Sediment Sediment depth exceeding 1/2 inch Remove sediment from stand filter bed. General Accumulation accumulated on sand filter bed. Sediment should be tested for toxicants and on Sand disposed of in accordance with health department requirements. Trash and Trash and debris accumulated on sand filter Remove trash and debris from sand filter bed. Debris bed. Sand Filter Drawdown of water through the sand filter Remove and replace top several inches of sand. Plugged media takes longer than 24-hours, and/or May require replacement of entire sand filter flow through the overflow pipes occurs depth depending on extent of plugging frequently. Short Flows are concentrated over one section of Repair cause of short circuiting. Repair any Circuiting the sand filter rather than dispersed. damage to sand filter bed. Damaged Any part of the piping that is crushed or Repair or replace pipe. Pipes deformed more than 20% or any other failure to the piping. Above Flow Spreader Flow spreader uneven or clogged so that Level and/or clean the spreader and so that Ground flows are not uniformly distributed across flows are spread evenly over the entire sand Sand sand filter. filter. Filter Erosion Erosion damage over two inches deep. Stabilize slopes using proper erosion control Damage to measures. Slopes Prolonged Sand is saturated for prolonged periods of Limit low, continuous flows to a small portion of Flows time (several weeks) and does not dry out the facility by using a low wooden divider or between storms due to continuous base flow slightly depressed sand surface. or prolonged flows from detention facilities. Sediment/ Clean-outs are full or partially plugged with Remove sediment from clean-outs. Debris in sediment and/or debris. Clean-Outs Below Sediment Sediment accumulation in pre-settling cell of Remove sediment deposits. Sediment should be Ground Accumulation vault bottom exceeds the maximum allowable tested for toxicants and disposed of in Sand in Pre-Settling design depth. accordance with health department Filter Cell requirements. Access Cover Maintenance person cannot remove cover Repair or Replace cover. Damaged/Not using normal lifting pressure. Working Ventilation Ventilation area blocked or plugged. Clear vent. Baffles/Internal Baffles or walls corroding, cracking, warping Repair or replace baffles to design specifications. Walls and/or showing signs of failure. Access Ladder Ladder is corroded or deteriorated, has sharp Replace or repair ladder to design specifications. Damaged edges, is not securely attached to structure wall, missing rungs, cracked, or misaligned. Damage to Cracks wider than 1/2 inch and any evidence Replace or repair vault to design specifications Vault Structure of soil particles or ground water entering the Vault is structurally sound. structure through the cracks. Vault is not structurally sound. Joints Any openings or voids allowing soil to enter Repair all joints between tank/pipe sections. Between Vault facility. and Pipes

COBG Stormwater Facility Maintenance Manual Page 36 March 2019

Stormwater Media Filter

A stormwater media filter is a passive, flow-through, stormwater filtration system. The system is comprised of one or more vaults that house replaceable, media-filled filter cartridges. A stormwater media filter works by passing stormwater through the filtering medium, which traps particulates and/or adsorb pollutants such as dissolved metals and hydrocarbons. Once filtered through the media, the treated stormwater is directed to a collection pipe or discharged into an open channel drainage way.

The filter media can be housed in cartridge filters enclosed in concrete vaults or catch basin-like structures. Various types of filter media are available.

Stormwater media filter units are proprietary manufactured systems. See manufacturer's publications for additional maintenance information.

COBG Stormwater Facility Maintenance Manual Page 37 March 2019

Stormwater Media Filter – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Sediment Sediment has accumulated to within six Remove sediment. Fore bay Accumulation inches of the invert of the lowest pipe. Sediment Sediment depth exceeds 1/4 inch on top of Remove sediment. Look for other indicators of Filter Accumulation filter cartridges. clogged cartridges or overflow. Vault on Top of Filter Cartridges. Sediment Sediment depth exceeds four inches on the Remove sediment from vault. Look for other Accumulation vault floor. indicators of clogged cartridges or overflow. in Vault Trash and Excessive trash and debris accumulation in Remove trash and debris. Debris vault. Accumulation Access Cover Maintenance person cannot remove cover Repair or Replace cover. Damaged/Not using normal lifting pressure. Working Vault Structure Structure is unsound. Repair or replace vault. Damage Cracks wider than 1/2 inch at the joint of any Repair cracks. inlet/outlet pipe or evidence of soil particles or ground water entering through the cracks. Baffles Baffles corroding, cracking, warping and/or Repair or replace baffles to design specifications. showing signs of failure.

Access Ladder Ladder is corroded or deteriorated, has Repair or replace ladder to design specifications. Damaged sharp edges, is not securely attached to structure wall, missing rungs, cracked, or misaligned. Media Pore space between media granules is Media cartridges replaced. Media absent. Cartridge Short Flows do not properly enter filter cartridges. Replace filter cartridges. Circuiting Filter Filter cartages remain submerged and flow Replace filter cartridges. cartridges bypasses cartages during average rainfall Submerged. event.

COBG Stormwater Facility Maintenance Manual Page 38 March 2019

Oil/Water Separator

An oil/water separator is an underground vault that treats stormwater by mechanically separating oil from water. The oil rises to the surface and floats on the water and sediment settles to the bottom. Oil/water separators are most commonly used as the first pre-treatment facility in a series of stormwater management facilities.

COBG Stormwater Facility Maintenance Manual Page 39 March 2019

Oil/Water Separator – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Monitoring Discharge water shows obvious signs of poor Determine cause of separator failure and repair. General water quality (i.e. obvious oil or other contaminants present).

Sediment Sediment in bottom of vault exceeds six Remove sediment from separator. Sediment Accumulation inches in depth. should be tested for toxicants and disposed of in accordance with health department requirements. Trash and Trash and debris accumulation in vault, or Remove trash and debris from vault and/or Debris pipe inlet/outlet, floatables and non- inlet/outlet piping. Accumulation floatables. Oil Oil accumulations that exceed one inch on Remove oil from vault. Dispose in accordance Accumulation the surface of the water. with state and local rules and regulations.

Damaged Inlet or outlet piping damaged or broken and Repair or replace pipe. Pipes in need of repair. Access Cover Maintenance person cannot remove cover Repair or replace cover. Damaged/Not using normal lifting pressure. Working Vault Top slab has holes larger than two square Repair or replace vault top. Structure inches or cracks wider than 1/4 inch. Damage Frame not sitting flush on top slab. Repair or replace top and/or frame. Separation of more than 3/4 inch of the frame from the top slab. Frame not securely attached. Structure is unsound. Repair or replace vault.

Grout has separated or cracked wider than Re-grout pipe and secure at basin wall. 1/2 inch and longer than one foot at the joint of any inlet/outlet pipe or any evidence of soil particles or ground water entering oil/water separator through cracks. Cracks wider than 1/2 inch at the joint of any Repair cracks. inlet/outlet pipe or evidence of soil particles or ground water entering through the cracks.

Baffles Baffles corroding, cracking, warping and/or Repair or replace baffles to design specifications. showing signs of failure. Access Ladder is corroded or deteriorated, has sharp Repair or replace ladder to design specifications. Ladder edges, is not securely attached to structure Damaged wall, missing rungs, cracked, or misaligned.

COBG Stormwater Facility Maintenance Manual Page 40 March 2019

Vortex Sedimentation Vault

A vortex sedimentation vault consists of a cylindrical vessel where the inlet flow spirals around the perimeter in a vortex-type action causing the heavier particles to settle out of the stormwater. It uses a vortex-enhanced settling mechanism (swirl-concentration) to capture settleable solids, floatables, and oil and grease. Vortex sedimentation vaults are most commonly used as the first pre-treatment facility in a series of stormwater management facilities.

Vortex sedimentation vaults are proprietary manufactured systems. See manufacturer's publications for additional maintenance information.

COBG Stormwater Facility Maintenance Manual Page 41 March 2019

Vortex Sedimentation Vault – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Sediment, Sediment, trash and debris accumulations fill Remove sediment. General Trash and more than 80% of the sump. Debris Accumulation Floatable Floatable trash accumulation that exceeds Remove floatable trash. Trash eight inches at the water surface. Accumulation Oil Oil accumulation that exceeds 1/2 inch at the Remove oil from vault. Dispose in accordance Accumulation water surface. with state and local rules and regulations.

Damaged Inlet or outlet piping damaged or broken and Pipe repaired and or replaced. Pipes in need of repair. Baffles Baffles corroding, cracking, warping and/or Repair or replace baffles to design specifications. showing signs of failure. Vault Structure is unsound. Repair or replace vault. Structure Damage Cracks wider than 1/2 inch at the joint of any Repair cracks. inlet/outlet pipe or evidence of soil particles or ground water entering through the cracks.

Access Ladder is corroded or deteriorated, has Repair or replace ladder to design specifications. Ladder sharp edges, is not securely attached to Damaged structure wall, missing rungs, cracked, or misaligned.

COBG Stormwater Facility Maintenance Manual Page 42 March 2019

Bioswale Sedimentation Trap

A bioswale sedimentation trap is a concrete structure typically fitted with a slotted grate or multiple slotted grates to act as debris barriers. The concrete structure provides a storage volume (sump) below the outlet pipe to allow sediment and debris to settle out of the stormwater runoff.

COBG Stormwater Facility Maintenance Manual Page 43 March 2019

Bioswale Sedimentation Trap – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature Trash and Trash or debris which is located immediately in Remove trash and debris. General Debris front of the sediment trap opening or is blocking inletting capacity of the basin.

Dead animals or vegetation that could Remove dead animals or vegetation. generate odors that could cause complaints or dangerous gases (e.g., methane). Sediment Sediment (in the trap) that exceeds 2.5 inches. Remove sediment from trap.

Fractures or Structure is unsound. Repair or replace sediment trap to design Cracks in standards. Basin Walls/ Bottom Grout has separated or cracked wider than 1/2 Re-grout pipe and secure to wall of trap. inch and longer than one foot at the joint of any inlet/outlet pipe. Settlement/ Sediment trap has settled or become Repair or replace sediment trap. Misalignment misaligned creating a safety, function, or design problem. Vegetation Vegetation growing across and blocking more Remove vegetation. than 10% of the basin opening.

Contaminants Any evidence of oil, gasoline, sewage or other No evidence of contaminants or pollutants and Pollution pollutants beyond typical levels. present.

For major spills coordinate removal/cleanup with the Department of Ecology at (360) 407- 6300. Trash and Trash and debris that is blocking more than Remove trash and debris. Debris Debris 20% of grate surface inletting capacity. barrier Damaged or Grate missing or damaged. Repair or replace grate to design specifications. Missing.

COBG Stormwater Facility Maintenance Manual Page 44 March 2019

Field/Area Inlet

A field/area inlet is a concrete, plastic or steel structure fitted with a slotted grate to collect stormwater runoff and route it through underground pipes.

Field/area inlets typically provide a storage volume (sump) below the outlet pipe to allow sediment and debris to settle out of the stormwater runoff. Typically field/area inlets are fitted with a spill control device (inverted elbow on outlet pipe) intended to contain large quantities of grease or oils.

The most common tool for cleaning a field/area inlet is a vactor truck which is used to remove sediment and debris from the sump. A field/area inlet may be an enclosed space where harmful chemicals and vapors can accumulate. Therefore, if the inspection and maintenance requires entering a confined space, it should be conducted by an individual trained and certified to work in hazardous confined spaces.

COBG Stormwater Facility Maintenance Manual Page 45 March 2019

Field/Area Inlet – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Problem Feature

Trash and Trash or debris blocking capacity of the field inlet. Remove trash and debris. General Debris Dead animals or vegetation that could generate Remove dead animals or vegetation. odors that could cause complaints or dangerous gases (e.g., methane). Sediment Sediment has accumulated to within six inches of Remove sediment. the invert of the lowest pipe or to within 4 inches of the spill control device. Structure Top slab has holes larger than two square inches Repair or replace top slab. Damage to or cracks wider than 1/4 inch. Frame and/or Top Slab (Intent is to make sure no material is running into basin). Frame not sitting flush on top slab, i.e., Repair or replace top frame. separation of more than 3/4 inch of the frame from the top slab. Frame not securely attached.

Fractures or Structure is unsound. Repair or replace inlet. Cracks in Basin Walls/ Grout has separated or cracked wider than 1/2 Re-grout pipe and secure at inlet wall. Bottom inch and longer than one foot at the joint of any inlet/outlet pipe or any evidence of soil particles or ground water entering field inlet through cracks. Settlement/ Field inlet has settled or become misaligned Repair or replace inlet. Misalignment creating a safety, function, or design problem. Vegetation Vegetation growing across and blocking more Remove vegetation. than 10% of the inlet opening. Contaminants Any evidence of oil, gasoline, sewage or other No evidence of contaminants or pollutants and Pollution pollutants beyond typical levels. present.

For major spills coordinate removal/cleanup with the Department of Ecology at (360) 407-6300. Spill Control Spill control device missing or damaged. Repair or replace spill control device to design Device specifications.

Grate Not in Cover is missing or only partially in place or Repair or replace grate. Metal Place missing. Grates Grate Grate with opening wider than 7/8 inch. Repair or replace grate. opening Unsafe Damaged or Grate missing or broken member(s) of the grate. Repair or replace grate. Missing.

COBG Stormwater Facility Maintenance Manual Page 46 March 2019

Access Road and Easement

Many stormwater facilities have access roads to bring in heavy equipment for facility maintenance. These roads should be maintained for inspection access and ease of equipment access.

All facilities should allow access for the inspection process.

The easement area should be adequately landscaped or otherwise stabilized. Bare soil areas will generate higher levels of stormwater runoff and increase erosion and sedimentation in stormwater facilities.

COBG Stormwater Facility Maintenance Manual Page 47 March 2019

Access Road/Easement – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Erosion Soils are bare or eroded. Seed or use other stabilization BMP. General Road Condition of road surface limits access. Repair road. Surface Erosion of Noticeable rills are seen in landscaped areas. Identify causes of erosion and steps taken to Ground slow down/spread out the water. Fill, contour, Surface and seed eroded areas. If needed, re-grade affected areas.

Trash & Any trash and debris which exceed five cubic Remove trash and debris. Debris / feet per 1,000 square feet (this is about equal to Litter the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping. Poisonous Any poisonous or nuisance vegetation which No danger of poisonous vegetation. Vegetation may constitute a hazard to maintenance and Noxious personnel or the public. Weeds Evidence of noxious weeds as defined by State Remove noxious weeds. Comply with State or or local regulations. local eradication policies.

Tree Growth Tree growth does not allow maintenance Remove trees that hinder maintenance activities. and Hazard access or interferes with maintenance activity Trees (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. Remove hazard trees. Weeds Weeds growing in more than 20% of the Remove weeds. (Non- landscaped area (trees and shrubs only). poisonous)

COBG Stormwater Facility Maintenance Manual Page 48 March 2019

Fence, Gate, and/or Water Quality Sign

Stormwater facilities such as detention ponds or treatment wetlands often have fences to protect them from damage. Most facilities are also required to have informational signs identifying the area as a stormwater facility.

COBG Stormwater Facility Maintenance Manual Page 49 March 2019

Fence, Gate and/or Water Quality Sign – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Gate or Openings in fence, missing gate, or openings Repair fence or gate. General Fence Allows beneath fence. Unauthorized Entry Locking Locking mechanism cannot be opened by one Repair or replace locking mechanism. Mechanism maintenance person with proper tools.

Lock is not present or does not operate Repair or replace lock. correctly. Damaged Posts out of plumb. Plumb posts. Parts Erosion Erosion has resulted in an opening under a Replace soil under fence so that no opening fence that allows entry by people or pets. exceeds four inches in height. Eliminate source or erosion. Water Water quality sign is not properly attached. Reattach water quality sign. Quality Sign Water quality sign is missing or 20% of the Replace sign. surface is unreadable.

COBG Stormwater Facility Maintenance Manual Page 50 March 2019

Conveyance Stormwater Pipe

Stormwater pipes must be cleaned to remove sediment or blockages when problems are identified. Stormwater pipes must be clear of obstructions and breaks to prevent localized flooding.

COBG Stormwater Facility Maintenance Manual Page 51 March 2019

Conveyance Storm Pipe – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Obstructions, Obstruction exists in pipe, reducing flow Use mechanical methods to remove obstruction. General Including capacity. Do not put root-dissolving chemicals in storm Roots sewer pipes. If necessary, remove the vegetation over the line.

Pipe Dented Inlet/outlet piping damaged or broken and in Repair or replace pipe. or Broken need of repair.

Pipe Rusted Any part of the piping that is crushed or Repair or replace pipe. or deformed excessively or any other failure to Deteriorated the piping. Sediment & Sediment depth is greater than 15% of pipe Clean pipe. Evaluate source of sediment Debris diameter. upstream of the pipe and stabilize if possible.

Trash screen Open ended stormwater pipes greater than 15 Install trash screen. Missing inches need a trash screen.

Contaminants Any evidence of oil, gasoline, sewage or other No evidence of contaminants or pollutants and Pollution pollutants beyond typical levels. present.

For major spills coordinate removal/cleanup with the Department of Ecology at (360) 407- 6300.

COBG Stormwater Facility Maintenance Manual Page 52 March 2019

Conveyance Ditch

Conveyance ditches must be occasionally maintained to allow them to continue to operate as they were designed to. Ditches must be kept clear of obstructions and excessive sediment and vegetation to prevent localized flooding.

COBG Stormwater Facility Maintenance Manual Page 53 March 2019

Conveyance Ditch – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Sediment Sediment depth exceeds six inches. Remove sediment deposits. When finished, ditch General Accumulation should be level from side to side and drain freely in intended direction. There should be no areas of standing water once inflow has ceased. Standing Excessive standing water in the ditch If possible repair cause of poor drainage. This Water between storms due to ditch not draining may include, but is not limited to the following freely. activities: remove sediment or trash blockages, improve grade of ditch. Eroded or When grass is sparse or bare or eroded Determine why grass growth is poor and correct Unstable Side patches occur in more than 20% of the ditch. that condition. Replant with plugs of grass at Slopes eight inch intervals or reseed. If cause is excessive moisture replace grass with wetland plantings. Vegetation Grass is excessively tall (greater than 15 Mow vegetation and/or remove nuisance inches). vegetation so that flow not impeded. Grass Nuisance weeds and other vegetation start to should be mowed to a height of three to four take over ditch. inches. Inlet/Outlet Inlet/outlet areas clogged with sediment Remove material so that there is no clogging or pipes or and/or debris. blockage in the inlet and outlet area. culverts Trash and Any trash and debris which exceed five cubic Remove trash and debris from ditch. Debris feet per 1,000 square feet (this is about equal Accumulation to the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping. Erosion/ Eroded or scoured ditch bottom. Permanently stabilize ditch bottom. Scouring

COBG Stormwater Facility Maintenance Manual Page 54 March 2019

Stormwater Facility Discharge Points

Stormwater facility discharge points convey stormwater from the stormwater facility into drainage trenches and receiving waters or other drainage areas. Stormwater facility discharge points need to be assessed to make sure stormwater is not causing any negative impacts to these drainage areas.

COBG Stormwater Facility Maintenance Manual Page 55 March 2019

Facility Discharge Point – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Obvious Any evidence of oil, gasoline, sewage or other Effluent discharge from facility should be clear. Monitoring Signs of Poor pollutants. Water Quality Identify and remove source or report to City of Battle Ground Illicit Discharge Program. Off Site Erosion or scouring in ditch or stream banks Stabilize ditch or stream banks. Assessment due to flow channelization, or higher flows. Report to City of Battle Ground for Engineer Evaluation.

Missing or Only one layer of rock exists above native soil Rock pad replaced to design standards. General Moved Rock in area five square feet or larger, or any exposure of native soil.

Erosion Soil erosion in or adjacent to discharge point. Repair erosion and permanently stabilize area.

Obstructions, Obstruction exists in pipe, reducing flow Use mechanical methods to remove obstruction. Including capacity. Roots Do not put root-dissolving chemicals in storm sewer pipes. If necessary, remove the vegetation over the line. Pipe Rusted Any part of the piping that is crushed or Pipe repaired or replaced. or deformed excessively as determined by an Deteriorated inspector or any other failure to the piping.

Contaminants Any evidence of oil, gasoline, sewage or other No contaminants or pollutants present. and Pollution pollutants beyond typical levels.

For major spills coordinate removal/cleanup with the Department of Ecology at (360) 407- 6300. Internal (If Applicable)

Energy Dissipater See Energy Dissipater Requirements

COBG Stormwater Facility Maintenance Manual Page 56 March 2019

Tree Box Filters

Tree Box Filters are stormwater treatment systems that use biofiltration media to remove pollutants from stormwater.

COBG Stormwater Facility Maintenance Manual Page 57 March 2019

Tree Box Filters – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Tree Box Clogged Standing Water  Replace mulch Filter and mulch Surrounding Area Cracks in Damage to box structure  Repair vault if cracks are wider than ½ inch structure or evidence of soil entering through cracks Damaged Damage to grate  Replace grate grate Clogged Bypass clogged  bypass Tree Grate Broken or Broken or damaged grates or erosion control  Remove and clean tree grates and erosion and Erosion damaged stones control stones Control grates or Stones erosion control stones Debris, trash Silt/clay in Silt/clay in media  Remove media to depth of silt/clay and and mulch media replace with new media Trash in box Trash in box structure  Remove trash structure Leaves in box Leaves in box structure  Remove leaves structure Every 6 Every 6 months  Replenish media as needed months  Replace mulch with double shredded mulch evenly across the entire unit to a depth of 3”.  Ensure correct positioning of erosion control stones  Replace grates Facility Area Refuse Excessive refuse around tree box planter  Remove all refuse and dispose of around Tree appropriately Box Filter

Inlet Excessive Accumulated sediments or trash impair free  Sediments or trash should be removed Sediment or flow of water into tree box filter  Inlet should be free of obstructions allowing Trash free distributed flow of water into the tree box Accumulation filter

Mulch Cover Trash and Excessive trash and/or debris accumulation  Trash and debris should be removed and floatable mulch cover raked level. Ensure bark debris nugget much is not used accumulation  Minimal trash or other debris on mulch Ponding of Ponding in tree box planter could indicate  Replace mulch water on clogging due to excessive fine sediment  Stormwater should drain freely and evenly mulch cover accumulation or spill of petroleum oils through mulch cover Vegetation Plants not Soil/mulch too wet, evidence of spill,  Plants should be healthy and pest free growing or in Incorrect plant selection, pest infestation,  Contact manufacturer for advice poor condition vandalism of plants. Plant growth Plants should be appropriate to the species  Trim/prune plants in accordance with typical excessive and location landscaping and safety needs Structure Structure has Cracks wider than ½ inch or evidence of soil  Repair cracks or damage to vault visible cracks particles entering the structure through the cracks

COBG Stormwater Facility Maintenance Manual Page 58 March 2019

Vegetation Management

Use Only Appropriate Plants

Use native species of plants where ever possible to reduce maintenance, watering requirements, and pesticide usage.

Generally, vegetation should be maintained to blend into surrounding areas. Stormwater facilities can provide habitat for aquatic life and birds. Promoting natural vegetation where feasible improves habitat. With careful design stormwater facilities can blend into and complement the site’s landscaping.

Practices

Successful vegetation management will focus on establishing and maintaining healthy low- maintenance native plantings and sustaining the design function of vegetated filters such as biofiltration swales. This includes controlling invasive plants where feasible, and planting cover on bare soils.

In some cases, the original plantings may not be appropriate for the actual condition at a facility. One example is a frequently flooded swale that cannot support normal turf. In cases such as this, replace turf with appropriate wetland plants if the underlying drainage problem cannot be fixed.

Limit mulch use to covering bare soil while establishing plantings. Consider the use of soil amendments such as compost before using fertilizer. The use of pesticides and, in most cases fertilizer, is not compatible with the task of pollutant removal or the direct connection of stormwater facilities to streams and groundwater. Chemical use should be avoided within 25 feet of any area that holds or conveys surface water or stormwater. This includes the base of a biofiltration swale.

COBG Stormwater Facility Maintenance Manual Page 59 March 2019

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COBG Stormwater Facility Maintenance Manual Page 60 March 2019

Low Impact Development (LID) BMPs

LID best management practices are distributed stormwater management practices that model the pre-disturbance hydrologic processes of infiltration, filtration, storage, evaporation and transpiration. LID BMPs include bioretention, rain gardens, permeable pavements, roof downspout controls, dispersion, soil quality and depth and vegetated roofs.

COBG Stormwater Facility Maintenance Manual Page 61 March 2019

Low Impact Development BMPs – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

General Spill None.  All sites must implement BMPs to prevent Prevention hazardous or solid wastes or excessive oil and sediment from contaminating stormwater. Spill Cleanup Release of pollutants.  Call your local or regional hotline number to report any spills or other illicit discharges.  Clean up spills as soon as possible to prevent contamination of stormwater.  Restore BMP facility design and function per the record drawings. Pests Pest of concern is present and impacting BMP  Pesticide use should be generally facility function. discouraged, even conditionally prohibited in some cases.  Pesticides include the following: herbicides, fungicides, insecticides, rodenticides, and pediculicides.  If pesticide use is planned in or near LID BMPs, make sure to check the following current regulations: 1) Federal- Environmental Protection Agency (EPA) Federal Insecticide and Rodenticide Act. 2) State- Ecology, Washington State Department of Agriculture, Washington State Department of Fish and Wildlife, Natural Resources Conservation Services. 3) Local city or county ordinances/codes, and/or applicable Integrated Pest Management (IPM) plan.  For the protection of health and safety, check the following: 1) Washington State Department of Labor & Industries. 2) Washington State Department of Health (local branch if applicable).

COBG Stormwater Facility Maintenance Manual Page 62 March 2019

Bioretention Facilities

Bioretention facilities are engineered facilities that store and treat stormwater by filtering it through a specified soil profile. Water that enters the facility ponds in an earthen depression or other basin (e.g., concrete planter) before it infiltrates into the underlying bioretention soil. Stormwater that exceeds the storage capacity overflows to an adjacent drainage system. Treated water is either infiltrated into the underlying native soil or collected by an underdrain and discharged. Bioretention facilities are considered Stormwater Treatment and Flow Control BMPs/Facilities when used to help meet Minimum Requirements #6 (treatment) and #7 (flow control), or both.

COBG Stormwater Facility Maintenance Manual Page 63 March 2019

Bioretention Facilities – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Earthen Side Erosion Erosion (gullies/rills) greater than 2 inches  Eliminate cause of erosion and stabilize Slopes and deep around inlets, outlets, and alongside damaged area (regrade, rock, vegetation, Berms slopes. erosion control matting).  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.  Properly designed, constructed and established facilities with appropriate flow velocities should not have erosion problems 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. 3) Flow dissipation and erosion strategies at the facility inlet. Erosion Erosion of sides causes slope to become a  Take actions to eliminate the hazard and hazard. stabilize the slopes. Settlement Settlement greater than 3 inches (relative to  Restore to design height. undisturbed section of berm) Piping Downstream face of berm wet, seeps or  Plug any holes and compact berm (may leaks evident. require consultation with engineer, particularly on larger berms). Rodents Any evidence of rodent holes or water piping  Eradicate rodents (see “Pest Control”). in berm.  Fill holes and compact (may require consultation with engineer, particularly on larger berms). Concrete Cracks or Cracks or failure of concrete sidewalls.  Repair/seal cracks Sidewalls failure of  Replace if repair is insufficient concrete sidewalls Rockery Insecure Rockery side walls are insecure.  Stabilize rockery sidewalls (may require Sidewalls sidewalls consultation with engineer, particularly for walls 4 feet or greater in height). Facility Area Trash/Debris Trash and debris present.  Clean out trash and debris.

Facility Sediment Accumulated sediment to extent that  Remove excess sediment. bottom area infiltration rate is reduced (see “Ponded  Replace any vegetation damaged or Water”) or surface storage capacity destroyed by sediment accumulation and significantly impacted. removal.  Mulch newly planted vegetation.  Identify and control the sediment source.  If accumulated sediment is recurrent, consider adding presettlement or installing berms to create a forebay at the inlet. Leaves Accumulated leaves in facility.  Remove leaves if there is a risk of clogging outlet structure or water flow is impeded.

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Bioretention Facilities – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Low Sediment, Sediment, vegetation, or debris accumulated  Clear blockage. Permeability Vegetation or at or blocking (or having the potential to Check Dams Debris block) check dam, flow control weir or orifice. and Weirs Erosion Erosion and/or undercutting present.  Repair and take preventative measures to prevent future erosion and/or undercutting. Weir Grade board or top of weir damaged or not  Restore to level position. Damaged level. Ponded Ponded Water Excessive ponding water: Water overflows Determine cause and resolve in the following Water during storms smaller than the design event order: or ponded water remains in the basin 48 1) Confirm leaf or debris buildup in the facility is hours after the end of a storm. not impeding infiltration, remove leaf litter/debris. 2) Ensure the 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 Compacted Bioretention soil media protection is needed  Minimize all loading in the facility footprint Soil Media Soil Media when performing maintenance requiring (foot traffic and other loads) to the degree entrance into the facility footprint. feasible in order to prevent compaction of bioretention soils.  Never drive equipment or apply heavy loads in facility footprint.  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.  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.  If compaction occurs, soil must be loosened or otherwise rehabilitated to original design state. Splash Damaged Water is not being directed properly to the  Reconfigure/repair blocks to direct water to Block Inlet Splash Blocks facility and away from the inlet structure. facility and away from structure. Curb Cut Leaf Clogging Accumulated leaves at curb cuts.  Clear leaves (particularly important for key Inlet/Outlet inlets and low points along long, linear facilities).

COBG Stormwater Facility Maintenance Manual Page 65 March 2019

Bioretention Facilities – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Pipe Damaged Pipe is damaged.  Repair/replace. Inlet/Outlet Pipe

Clogged Pipe Pipe is clogged.  Remove roots or debris.

Reduced Sediment, debris, trash, or mulch reducing  Clear blockage Capacity capacity of inlet/outlet.  Identify source of the blockage and take actions to prevent future blockages. Accumulated Accumulated leaves at inlets/outlets.  Clear leaves (particularly important for key Leaves inlets and low points along long, linear facilities.) Inaccessible Maintain access for inspection.  Clear vegetation (transplant vegetation when Facility possible) 1 foot from inlets and outlets, maintain access pathways.  Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants. Erosion Erosion at Concentrated flows are causing erosion.  Maintain a cover of rock or cobbles or other Control at Inlet erosion protection measure (e.g., matting) to Inlet protect the ground where concentrated water enters the facility (e.g., a pipe, curb cut or swale) Trash Rack Trash/Debris Trash or other debris present on trash rack.  Remove and dispose of trash/debris.

Damaged Bar screen damaged or missing.  Repair or replace bar screen. screen Overflow Sediment/ Capacity reduced by sediment or debris.  Remove sediment or debris and dispose. Debris Underdrain Clogging Plant roots, sediment or debris reducing  Jet clean or rotary cut debris/roots from Pipe capacity of underdrain. underdrain(s). Prolonged surface ponding (see “Ponded  If underdrains are equipped with a flow Water”). restrictor (e.g., orifice) to attenuate flows, the orifice must be cleaned regularly. Facility Poor Vegetation survival rate falls below 75%  Determine cause of poor vegetation growth Bottom Area Vegetation within first two years of establishment and correct condition. and Upland Growth (unless project O&M manual or record  Replant as necessary to obtain 75% survival Slope drawing stipulates more or less than 75% rate or greater. Refer to original planting Vegetation survival rate). plan, or approved jurisdictional species list for appropriate plant replacements. (See Appendix 3 – Bioretention Plant List, in the LID Technical Guidance Manual for Puget Sound).  Confirm that plant selection is appropriate for site growing conditions.  Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants.

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Bioretention Facilities – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Vegetation Diseased Presence of diseased plants and plant  Remove any diseased plants or plant parts (General) Plants material. and dispose of in an approved location (e.g., commercial landfill) to avoid risk of spreading the disease to other plants.  Disinfect gardening tools after pruning to prevent the spread of disease.  See Pacific Northwest Plant Disease Management Handbook for information on disease recognition and for additional resources.  Replant as necessary according to recommendations provided for “facility bottom area and upland slope vegetation”. Trees and Pruning Pruning as needed.  Prune trees and shrubs in a manner Shrubs Needed appropriate for each species. Pruning should be performed by landscape professionals familiar with proper pruning techniques.  All pruning of mature trees should be performed by or under direct guidance of an ISA certified arborist. Overgrown Large trees and shrubs interfere with  Prune trees and shrubs using most current Trees and operation of the facility or access for ANSI A300 standards and ISA BMPs. Shrubs maintenance.  Remove trees and shrubs, if necessary. Dead Standing dead vegetation is present.  Remove standing dead vegetation. Vegetation  Replace dead vegetation within 30 days of reported dead and dying plants (as practical depending on weather/planting season).  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.  Determine cause of dead vegetation and address issue, if possible.  If specific plants have a high mortality rate, assess the cause and replace with appropriate species. Consultation with a landscape architect is recommended. Planting Planting beneath mature trees.  When working around and below mature beneath trees, follow the most current ANSI A300 mature trees standards and ISA BMPs to the extent practicable (e.g., take care to minimize any damage to tree roots and avoid compaction of soil).  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 no larger than 1-gallon containers.

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Bioretention Facilities – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Trees and Need for Tree Presence of or need for stakes and guys  Verify location of facility liners and underdrain Shrubs Support. (tree growth, maturation, and support needs) (if any) prior to stake installation in order to prevent liner puncture or pipe damage.  Monitor tree support systems: Repair and adjust as needed to provide support and prevent damage to tree.  Remove tree supports (stake, guys, etc.) after one growing season or maximum of 1 year.  Backfill stake holes after removal. Trees and Reduced Vegetation causes some visibility (line of  Maintain appropriate height for sight Shrubs – Visibility sight) or driver safety issues. clearance. Visibility  When continued, regular pruning (more than Needs 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.  Remove or transplant if continual safety hazard.  Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants. Flowering Dead Flowers Dead or spent flowers present.  Remove spent flowers (deadhead). Plants Perennials Spent Plants Spent plants.  Cut back dying or dead and fallen foliage and stems. Emergent Compromised Vegetation compromises conveyance.  Hand rake sedges and rushes with a small Vegetation Conveyance 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 Dead Plant Dead material from previous year’s growing  Leave dry foliage for winter interest. grasses Material cycle or dead collapsed foliage.  Hand rake with a small rake or fingers to (perennial) 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 Dead Growth Dead growth present in spring.  Hand rake with a small rake or fingers to Grasses remove dead growth before new growth (Evergreen) emerges in spring.  Clean, rake, and comb grasses when they become too tall  Cut back to ground or thin every 2-3 years as needed

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Bioretention Facilities – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Noxious Noxious Listed noxious vegetation is present (refer to  By law, class A & B noxious weeds must be Weeds Weeds current Clark County Noxious Weed List) removed, bagged and disposed as garbage immediately  Reasonable attempts must be made to remove and dispose of class C noxious weeds  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  Apply mulch after weed removal (see “Mulch”) Weeds Weeds are Weeds are present  Remove weeds with their roots manually with present pincer-type weeding tools, flame weeders, or hot water weeders as appropriate  Follow IPM protocols for weed management Excessive Low-lying Low-lying vegetation growing beyond facility  Edge or trim groundcovers and shrubs at Vegetation vegetation edge edge of facility growing  Some clippings can be left to replenish beyond facility organic material in the soil. Excessive leaf edge litter may cause clogging. Vegetation Excessive vegetation density inhibits  Determine whether pruning or other routine inhibiting flow stormwater flow beyond design ponding or maintenance is adequate to maintain proper becomes a hazard for pedestrian and plant density and aesthetics vehicular circulation and safety  Determine if planting type should be replaced to avoid ongoing maintenance issues (an aggressive grower under perfect growing conditions should be transplanted to a location where it will not impact flow)  Remove plants that are weak, broken or not true to form; replace in-kind  Thin grass or plants impacting facility function without leaving visual holes or bare soil areas  Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants Vegetation Vegetation blocking curb cuts, causing  Remove vegetation and sediment buildup blocking flow excessive sediment buildup and flow bypass Mulch Bare Spots Bare spots (without mulch cover) are present  Supplement mulch with hand tools to a depth or mulch depth less than 2 inches of 2 to 3 inches  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)  Keep all mulch away from woody stems Irrigation Irrigation Irrigation system present  Follow manufacturer’s instructions for O&M System System (if any) Irrigation Sprinklers or drip irrigation not  Redirect sprinklers or move drip irrigation to System not directed/located to properly water plants desired areas watering properly

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Bioretention Facilities – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Summer First year Trees, shrubs and groundcovers in first year  10 to 15 gallons per tree. Watering establishment of establishment period  3 to 5 gallons per shrub. (first year) Plants  2 gallons water per square foot for groundcover areas.  Water deeply, but infrequently, so that the top 6 to 12 inches of the root zone is moist.  Use soaker hoses or spot water with shower type wand when irrigation system is not present (pulse water to enhance soil absorption, when feasible; 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.  Add a tree bag or slow-release watering device (e.g., bucket with perforated bottom) for watering newly installed trees when irrigation system is not present.

Summer Second-third Trees, shrubs and groundcovers in second  10 to 15 gallons per tree. Watering year or third year of establishment period  3 to 5 gallons per shrub. (second and establishment  2 gallons water per square foot for third years) Plants groundcover areas.  Water deeply, but infrequently, so that the top 6 to 12 inches of the root zone is moist.  Use soaker hoses or spot water with shower type wand when irrigation system is not present (pulse water to enhance soil absorption, when feasible; 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 Drought Established vegetation (after 3 years)  Plants are typically selected to be drought Watering tolerant and not require regular watering after (after establishment; however, trees may take up to establish- 5 years of watering to become fully ment) established.  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.  Water during drought conditions or more often if necessary to maintain plant cover.

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Bioretention Facilities – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Mosquitoes Mosquitoes Standing water remains for more than 3  Identify the cause of the standing water and days after the end of a storm take appropriate actions to address the problem (see “Ponded Water”).  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 getting approval from sanitary sewer authority.  Do not use pesticides or Bacillus thuringiensis israelensis (Bti). Nuisance Nuisance Nuisance animals causing erosion,  Reduce site conditions that attract nuisance Animals animals damaging plants, or depositing large species where possible (e.g., plant shrubs volumes of feces and tall grasses to reduce open areas for geese, etc.)  Place predator decoys.  Follow IPM protocols for specific nuisance animal issues.  Remove pet waste regularly.  For public and right-of-way sites consider adding garbage cans with dog bags for picking up pet waste. Insect Pests Insect pests Signs of pests, such as wilting leaves,  Reduce hiding places for pests by removing chewed leaves and bark, spotting or other diseased and dead plants. indicators  For infestations, follow IPM protocols.

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Rain Gardens

Rain gardens are non-engineered, shallow, landscaped depressions with compost-amended soils and adapted plants. The depression temporarily stores storm water runoff from adjacent areas. Some or all of the influent stormwater passes through the amended soil profile and into the underlying native soil. Stormwater that exceeds the storage capacity is designed to overflow to an adjacent drainage system.

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Rain Gardens – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Earthen Side Erosion Persistent soil erosion on slopes.  If erosion persists, water may be flowing into Slopes the garden too rapidly. In this case, the slope of the pipe or swale directing water to the garden, or the amount of water may need to be reduced (see “Erosion control at inlet”). Rockery Unstable Rockery side walls are insecure.  Stabilize rockery sidewalls (may require Sidewalls Sidewalls consultation with engineer, particularly for walls 4 feet or greater in height). Rain Garden Trash and Trash and debris present.  Cleanout trash and debris. Footprint Debris Rain Garden Sediment Visible sediment deposition in the rain garden  Remove sediment accumulation. Bottom Area that reduces drawdown time of water in the  If sediment is deposited from water entering rain garden. the rain garden, determine the source and stabilize the area. Leaves Accumulated leaves in rain garden (may  Remove leaves. reduce infiltration capacity of rain garden or clog overflow). Ponded Ponded Excessive ponding water: Ponded water Confirm leaf, debris or sediment buildup in the Water Water remains in the basin more than 3 days after bottom of the rain garden is not impeding the end of a storm. infiltration. If necessary, remove leaf litter/debris/sediment. If this does not solve the problem, consultation with a professional with rain garden expertise is recommended to evaluate the following:  Check for other water inputs (e.g., groundwater, illicit connections).  Verify that the facility is sized appropriately for the contributing area. Confirm that the contributing area has not increased.  Determine if the soil is clogged by sediment accumulation at the surface or if the soil has become overly compacted. Splash Improper Water is not being directed properly to the  Reconfigure / repair blocks to direct water to Block Inlet Water rain garden and away from the building. the rain garden and away from the building. Direction Pipe Inlet / Blocked Pipe capacity is reduced by sediment or  Clear pipes of sediment and debris. Outlet pipes debris (can cause backups and flooding). Damaged Damaged or cracked pipes.  Repair / seal cracks. Pipes  Replace when repair is insufficient. Erosion Missing Rock or cobble is removed or missing and  Maintain a cover of rock or cobbles to protect Control at Erosion concentrated flows are contacting soil. the ground where concentrated water flows Inlet Control into the rain garden from a pipe or swale. Vegetation Dead or Dying, dead or unhealthy plants.  Maintain a healthy cover of plants. Dying Plants  Remove any diseased plants or plant parts and dispose of in commercial landfill to avoid risk of spreading the disease to other plants.  Disinfect gardening tools after pruning to prevent the spread of disease.  Re-stake trees if they need more support, but plan to remove stakes and ties after the first year.  Cars can damage roots – protect root areas of trees and plants from vehicle traffic. COBG Stormwater Facility Maintenance Manual Page 74 March 2019

Rain Gardens – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Vegetation Overgrown Vegetation inhibits sight distances and  Keep sidewalks and sight distances on Continued Vegetation sidewalks. roadways clear. Dead Broken, dead, or sucker vegetation is  Remove broken or dead branches and Vegetation present. suckers. Overgrown Vegetation is crowding inlets and outlets.  Keep water inlets and outlets in the rain Vegetation garden clear of vegetation. Nutrient  Yellowing: possible Nitrogen (N)  Test soil to identify specific nutrient Deficiencies deficiency. deficiencies.  Poor growth: possible Phosphorous (P)  Consult with a professional knowledgeable in deficiency. the area of natural amendments or refer to  Poor flowering, spotting or curled leaves, or Natural Lawn and Garden Care resources weak roots or stems: possible Potassium and avoid synthetic fertilizers. (K) deficiency.  Consider selecting different plants for soil conditions. Weeds Problem weeds are present.  Remove weeds by hand, especially in spring when the soil is moist and the weeds are small  Dig or pull weeds out by the roots before they go to seed  Apply mulch after weeding (see “Mulch”) Mulch Bare Spots Bare spots (without mulch cover) are present  Supplement mulch with hand tools to a depth or mulch depth less than 2 inches. of 2 to 3 inches.  Use coarse compost in the bottom of the rain garden and arborist wood chips on side slopes and rim (above typical water levels).  Keep all mulch from being in contact with woody stems. Summer Lack of Trees, shrubs and groundcovers in first year  Water once every 1-2 weeks or as needed Watering Water of establishment period. during prolonged dry periods (First Year)  10 to 15 gallons per tree.  3 to 5 gallons per shrub.  2 gallons water per square foot for groundcover areas.  Water deeply, but infrequently, so that the top 6 to 12 inches of the root zone is moist.  Use soaker hoses or spot water with a shower type wand when irrigation system is not present.  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 Lack of Trees, shrubs and groundcovers in second or  Water once every 2-4 weeks or as needed Watering Water third year of establishment period. during prolonged dry periods (Second and  10 to 15 gallons per tree. Third Years)  3 to 5 gallons per shrub.  2 gallons water per square foot for groundcover areas.  Water deeply, but infrequently, so that the top 6 to 12 inches of the root zone is moist.  Use soaker hoses or spot water with a shower type wand when irrigation system is not present.

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Rain Gardens – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Summer Lack of Established vegetation (after 3 years).  Water during drought conditions or more Watering Water often if necessary to maintain plant cover. (After  Identify trigger mechanisms for drought- Establish- stress (e.g., leaf wilt, leaf senescence, etc.) of ment) different rain garden species and water immediately after initial signs of stress appear. Mosquitoes Mosquitoes Standing water remains for more than 3 days  Identify the cause of the standing water and after the end of a storm. take appropriate actions to address the problem (see “Ponded Water”).  Do not use pesticides or Bacillus thuringiensis israelensis (Bti).

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Downspout, Sheet Flow, and Concentrated Dispersion Systems

Dispersion attenuates peak flows by slowing the runoff entering into the conveyance system, allowing some infiltration, and providing some water quality benefits. The following three types of dispersion systems are covered in this section:

 Downspout dispersion systems: Splash blocks or gravel-filled trenches, which serve to spread roof runoff over vegetated pervious areas.

 Sheet flow dispersion systems: Sheet flow dispersion is the simplest method of runoff control. This BMP can be used for any impervious or pervious surface that is graded to avoid concentrating flows. Because flows are already dispersed as they leave the surface, they need only traverse a narrow band of adjacent vegetation for effective attenuation and treatment.

 Concentrated dispersion systems: Dispersion of concentrated flows from driveways or other pavement through a vegetated pervious area.

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Downspout, Sheet Flow, and Concentrated Dispersion Systems – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Splash Block Water being Water is being directed toward building  Reconfigure/repair blocks to direct water (Downspout directed structure. away from building structure. Dispersion) towards building Erosion Water disrupts soil media.  Reconfigure/repair blocks.

Transition Erosion Adjacent soil erosion; uneven surface  Repair/replace transition zone to meet design Zone creating concentrated flow discharge; or criteria and eliminate concentrated flows. (Sheet Flow less than 2 foot of width. Dispersion) Dispersion Concentrated Visual evidence of water discharging at  Remove debris from trench surface, if Trench Flows concentrated points along trench (normal necessary. (Downspout condition is a “sheet flow” from edge of  Realign notched grade board or other Dispersion) trench; intent is to prevent erosion damage). distributor type, if possible.  Rebuild trench to standards, if necessary. Surface of Trash,  Fall and spring.  Remove/dispose in accordance with local Trench Debris,  Accumulated trash, debris, or sediment on solid waste requirements. (Downspout Sediment drain rock surface impedes sheet flow Dispersion) from facility. Vegetation, Vegetation/moss present on drain rock  Maintain open, freely draining rock surface. Moss surface impedes sheet flow from facility.

Pipes(s) to Trash, Accumulation of trash, debris, or sediment in  Remove/dispose. Trench Debris, roof drains, gutters, driveway drains, area (Downspout Sediment drains, etc. Dispersion) Plugged Pipe Pipe from sump to trench or drywell has  Clear sediment from inlet/outlet pipe screen accumulated sediment or is plugged. and inlet/outlet pipe.

Damaged Cracked, collapsed, broken, or misaligned  Repair/seal cracks. Pipe drain pipes.  Replace when repair is insufficient.

Sump Sediment Sediment in sump.  Remove/dispose in accordance with local (Downspout solid waste requirements. Dispersion)  Clear sediment from inlet/outlet pipe screen and or inlet/outlet pipe. Access Lid Cannot Cannot be easily opened.  Repair/replace. easily open Lid Buried Lid Buried.  Refer to record drawings for design intent. If the access lid was designed to be exposed, expose and restore to surface grade.

Missing Lid Cover missing.  Replace.

Rock Pad Missing Rock Only one layer of rock exists above native  Repair/replace rock pad to meet design (Concentrated soil in area 6 square feet or larger, or any standards. Flow exposure of native soil.  Enlarge pad size or add additional courses of Dispersion) rock, if necessary. Erosion Soil erosion in or adjacent to rock pad.  Repair/replace rock pad to meet design standards.

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Downspout, Sheet Flow, and Concentrated Dispersion Systems – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Dispersal Erosion Erosion (gullies/rills) greater than 2 inches  Eliminate cause of erosion and stabilize Area deep in dispersal area. damaged area (regrade, rock, revegetate). (General) Sediment or Accumulated sediment or debris to extent  Remove excess sediment or debris. Debris that blocks or channelizes flow path.  Identify and control the sediment source (if feasible). Ponded Water Standing Standing surface water in dispersion area  Identify the cause of the standing water (e.g., (Dispersal Water remains for more than 3 days after the end grade depressions, compacted soil) and take Area) of a storm event. appropriate actions to address the problem (e.g., regrade to eliminate depressions or aerate/amend soils). Plant Lack of Dispersal area vegetation in establishment  Water weekly during periods of no rain to Establishment Water period (1-2 year, or additional 3rd year ensure plant establishment. (Dispersal during extreme dry weather). Area) Vegetation Erosion Poor vegetation cover such that erosion is  Ensure proper care (e.g., watering). (Dispersal occurring.  Assess for nutrient deficiencies. Area)  Replant as needed with appropriate plant species for the soil and moisture conditions.  Consider amending soils to promote plant health. Overgrown Vegetation inhibits dispersed flow along flow  Trim, weed or replant to restore dispersed Vegetation path. flow path.

Sump Sediment Accumulated sediment in the sump.  Remove/dispose in accordance with local solid waste requirements.  Clear sediment from inlet/outlet pipe screen and/or pipe. Sump Access Lid cannot Cannot be easily opened.  Repair/replace. Lid be easily opened Buried Lid Buried.  Expose and restore to surface grade.

Missing Lid Cover missing.  Replace. General Pests Pest Signs of pest infestations (IPM protocol  Follow IPM protocols for weed and pest Infestation threshold(s) are exceeded). management.

Mosquitoes Mosquitoes Standing surface water in dispersion area  Identify the cause of the standing water and remains for more than 3 days after the end take appropriate actions to address the of a storm. problem (see “Ponded Water”).  Do not use pesticides or Bacillus thuringiensis israelensis (Bti). Rodents Rodents Rodent holes or mounds disturb dispersion  Fill and compact soil around the holes and flow paths. vegetate to restore flow path.

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Compost-amended Soils

Naturally occurring (undisturbed) soil and vegetation provide important stormwater functions including: water infiltration; nutrient, sediment, and pollutant adsorption; sediment and pollutant biofiltration; water interflow storage and transmission; and pollutant decomposition. Compaction from construction can reduce the soil’s natural ability to provide these functions. Establishing a minimum soil quality and depth in the post-development landscape can regain some of these stormwater functions, including increased treatment of pollutants and sediments that result from development and habitation, and minimizes the need for some landscaping chemicals. Sufficient organic matter can be attained through numerous amendments such as compost, composted woody material, biosolids, and forest product residuals.

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Compost-amended Soils – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Soil Media Vegetation in Vegetation not fully covering ground surface  Maintain 2 to 3 inches of mulch over bare (Maintain Poor Health or vegetation health is poor. areas in landscape beds. High  Add plants if sufficient space. Organic Soil  Re-seed bare turf areas until the vegetation Content) fully covers ground surface. Unhealthy Routine Maintenance.  Return leaf fall and shredded woody Vegetation materials from the landscape to the site when possible in order to replenish soil nutrients and structure. Unhealthy Routine Maintenance.  On turf areas, “grasscycle” (mulch-mow or Vegetation leave the clippings) to build turf health.

Pest, Weeds Routine Maintenance.  Avoiding use of pesticides (bug and weed killers), like “weed and feed”, which damage the soil. Unhealthy Routing Maintenance.  Where fertilization is needed (mainly turf and Vegetation annual flower beds), a moderate fertilization program should be used which relies on compost, natural fertilizers or slow-release synthetic balanced fertilizers.  Follow IPM protocols for fertilization procedures. Soil Media Compacted Soils become waterlogged, do not appear to  To remediate compaction, aerate soil, till to at (Maintain Soils be infiltrating. least 8-inch depth, or further amend soil with Infiltration) compost and re-till.  If areas are turf, aerate compacted areas and top-dress them with ¼ to ½ inch of compost to renovate them.  If drainage is still slow, consider investigating alternative causes (e.g., high wet season groundwater levels, low permeability soils).  Also consider site use and protection from compacting activities. Erosion / Erosion Areas of potential erosion are visible.  Identify and address cause of erosion (e.g., Scouring concentrated flow entering area, channelization of runoff) and stabilize damaged area (regrade, rock, vegetation, erosion control matting).  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. Grass / Unhealthy Less than 75% of planted vegetation is  Take appropriate maintenance actions (e.g., Vegetation Vegetation healthy with a generally good appearance. remove/replace plants).  If problem persists, evaluate if vegetation is appropriate for the location (e.g., exposure, soil, soil moisture).

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Compost-amended Soils – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected System Defect Results Feature

Noxious Noxious  Routine Maintenance (March –  By law, class A and B noxious weeds must Weeds Weeds September). be removed and disposed as garbage  Listed noxious vegetation is present (refer immediately. to current Clark County Noxious Weed  Reasonable attempts must be made to List). remove and dispose of class C noxious weeds.  Watch for and respond to new occurrences of especially aggressive weeds such as Himalayan blackberry, Japanese knotweed, morning glory, English ivy, and reed canary grass to avoid invasions.  It is strongly encouraged that herbicides not be used in order to protect water quality; use of herbicides and pesticides may be prohibited in some jurisdictions. Weeds Weeds  Routine Maintenance (March – October, as  Remove weeds with their roots manually with needed). pincer-type weeding tools, flame weeders, or  Weeds are present. hot water weeders as appropriate.  Follow IPM protocols for weed management.

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Permeable Pavement

Permeable pavement is a paving system which allows rainfall to percolate through the surface into the underlying soil or an aggregate bed, where stormwater is stored and infiltrated to underlying subgrade, or removed by an overflow drainage system. Permeable pavement facilities are considered Stormwater Treatment and Flow Control BMPs and can be used to meet Minimum Requirements #6 (treatment), #7 (flow control), or both. To satisfy Minimum Requirement #6, stormwater must be infiltrated into underlying soils that meet Ecology’s soil treatment requirements or filtered through an engineered treatment layer included in the pavement section.

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Permeable Pavement – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Permeable Deposits on Runoff from adjacent pervious areas deposits  Clean deposited soil or other materials from Pavements pavement soil, mulch or sediment on paving permeable pavement or other adjacent (All) surfacing  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)  Mulch and/or plant all exposed soils that may erode to pavement surface Porous Debris on None (Routine Maintenance) Clean surface debris from pavement surface Asphalt or pavement using one or a combination of the following Pervious methods: Concrete  Remove sediment, debris, trash, vegetation, and other debris deposited onto pavement (rakes and leaf blowers can be used for removing leaves)  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)  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. Surface is Surface is clogged:  Review the overall performance of the facility clogged Ponding on surface or water flows off the (note that small clogged areas may not reduce permeable pavement surface during a rain the overall performance of the facility) event (does not infiltrate)  Test the surface infiltration using ASTM C1701 as a corrective maintenance indicator. Perform one test per installation, but not less than 1 test per 2,500 square feet.  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 a combination of the following methods:  Combined pressure wash and vacuum system calibrated to not dislodge wearing course aggregate.  Hand held pressure washer or pressure washer with rotating brushes  Pure vacuum sweepers Note: If the annual/biannual routine maintenance standard to clean the pavement surface is conducted using equipment from the list above, corrective maintenance may not be needed.

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Permeable Pavement – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Porous Sediment Sediment present at the surface of the  Assess the overall performance of the Asphalt or present at the pavement pavement system during a rain event. If water Pervious surface of the runs off the pavement and/or there is ponding Concrete pavement then see above.  Determine source of sediment loading and evaluate whether or not the source can be reduced/eliminated. If the source cannot be addressed, consider increasing frequency of routine cleaning (e.g., twice per year instead of once per year). Moss growth Moss growth inhibits infiltration or poses slip  Sidewalks: Use a stiff broom to remove moss safety hazard in the summer when it is dry  Parking lots and roadways: Pressure wash, vacuum sweep, or use a combination of the two for cleaning moss from pavement surface. May require stiff broom or power brush in areas of heavy moss. Major cracks Major cracks or trip hazards and concrete  Fill potholes or small cracks with patching spalling and raveling mixes  Large cracks and settlement may require cutting and replacing the pavement section. Replace in-kind where feasible. Replacing porous asphalt with conventional asphalt is acceptable if it is a small percentage of the total facility area and does not impact the overall facility function.  Take appropriate precautions during pavement repair and replacement efforts to prevent clogging of adjacent porous materials Interlocking Routine Routine maintenance needed Clean pavement surface using one or a Concrete maintenance combination of the following methods: Paver Blocks needed  Remove sediment, debris, trash, vegetation, and and other debris deposited onto pavement Aggregate (rakes and leaf blowers can be used for Pavers removing leaves)  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) Note: Vacuum settings may have to be adjusted to prevent excess uptake of aggregate from paver openings or joints. Vacuum surface openings in dry weather to remove dry, encrusted sediment.

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Permeable Pavement – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Interlocking Surface is Surface is clogged:  Review the overall performance of the facility Concrete Clogged Ponding on surface or water flows off the (note that small clogged areas may not reduce Paver Blocks permeable pavement surface during a rain the overall performance of the facility) and event (does not infiltrate)  Test the surface infiltration rate using ASTM Aggregate C1701 as a corrective maintenance indicator. Pavers Perform one test per installation, but not less than one test per 2,500 square feet.  If the results indicate an infiltration rate of 10 inches per hour or less, then perform corrective maintenance to restore permeability.  Clogging is usually in the upper 2 to 3 centimeters of aggregate. Remove the upper layer of encrusted sediment, and fines and/or vegetation from openings and joints between the pavers by mechanical means and/or suction equipment (e.g., pure vacuum sweeper).  Replace aggregate in paver cells, joints, or openings per manufacturer’s recommendations. Sediment Sediment present at the surface of the  Assess the overall performance of the Present at the pavement pavement system during a rain event. If water Surface of the runs off the pavement and/or there is ponding, Pavement then see above.  Determine source of sediment loading and evaluate whether or not the source can be reduced/eliminated. If the source cannot be addressed, consider increasing frequency of routine cleaning (e.g., twice per year instead of once per year). Moss Growth Moss growth inhibits infiltration or poses slip  Sidewalks: Use a stiff broom to remove moss safety hazard in the summer when it is dry  Parking lots and roadways; Vacuum sweep or stiff broom/power brush for cleaning moss from pavement surface Missing or Paver block missing or damaged  Remove individual damaged paver blocks by Damaged hand and replace or repair per manufacturer’s Paver Block recommendations Loss of Loss of aggregate between paver blocks  Refill per manufacturer’s recommendations for Aggregate interlocking paver sections. between Paver Blocks Surface Settlement of surface  May require resetting Settlement Open-celled Sediment, Routine maintenance  Remove sediment, debris, trash, vegetation, Paving Grid Debris and other debris deposited onto pavement with Gravel (rakes and leaf blowers can be used for removing leaves)  Follow equipment manufacturer’s guidelines for cleaning surface. Clogged Aggregate is clogged:  Use vacuum truck to remove and replace top Aggregate Ponding on surface or water flows off the course aggregate permeable pavement surface during a rain  Replace aggregate in paving grid per event (does not infiltrate) manufacturer’s recommendations

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Permeable Pavement – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Open-celled Missing or Paving grid missing or damaged  Remove pins, pry up grid segments, and Paving Grid Damaged replace gravel with Gravel Paving Grid  Replace grid segments where three or more adjacent rings are broken or damaged  Follow manufacturer’s guidelines for repairing surface Surface Settlement of surface  May require resetting Settlement Loss of Loss of aggregate material in paving grid  Replenish aggregate material by spreading Aggregate gravel with a rake (gravel level should be maintained at the same level as the plastic rings or no more than ¼ inch above the top of rings). See manufacturer’s recommendations. Weeds Weeds present  Manually remove weeds  Presence of weeds may indicate that too many fines are present (refer to Action Needed under “Aggregate is Clogged” to address this issue) Poor Grass Poor grass coverage in paving grid  Restore growing medium, reseed or plant, Coverage aerate, and/or amend vegetated area as needed  Traffic loading may be inhibiting grass growth; reconsider traffic loading if feasible Excessive Routine maintenance  Use mulch mower to mow grass Grass Growth Lost Soil Routine maintenance  Sprinkle a thin layer of compost on top of grass surface (1/2” top dressing) and sweep it in  Do not use fertilizer Weeds Weeds present  Manually remove weeds  Mow, torch, or inoculate and replace with preferred vegetation Inlet/Outlet Damaged Pipe is damaged  Repair/replace Pipe Pipe Clogged Pipe Pipe is clogged  Remove roots or debris

Underdrain Clean Orifice Plant roots, sediment or debris reducing  Jet clean or rotary cut debris/roots from Pipe at least capacity of underdrain (may cause prolonged underdrain(s) biannually drawdown period)  If underdrains are equipped with a flow (may need restrictor (e.g., orifice) to attenuate flows, the more frequent orifice must be cleaned regularly cleaning during wet season) Raised Clean Orifice Plant roots, sediment or debris reducing  Jet clean or rotary cut debris/roots from Subsurface at least capacity of underdrain underdrain(s) Overflow biannually  If underdrains are equipped with a flow Pipe (may need restrictor (e.g., orifice) to attenuate flows, the more frequent orifice must be cleaned regularly cleaning during wet season)

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Permeable Pavement – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

Outlet Blocked Sediment, vegetation, or debris reducing  Clear the blockage Structure Outlet capacity of outlet structure  Identify the source of the blockage and take Structure actions to prevent future blockages Overflow Erosion Native soil is exposed or other signs of erosion  Repair erosion and stabilize surface damage are present at discharge point Observation Subsurface Water remains in the storage aggregate longer  If immediate cause of extended ponding is not Port Ponding than anticipated by design after the end of a identified, schedule investigation of subsurface storm materials or other potential causes of system failure. Adjacent Large Vegetation related fallout clogs or will  Sweep leaf litter and sediment to prevent Large Vegetation potentially clog voids surface clogging and ponding Shrubs or  Prevent large systems from damaging Trees subsurface structural components Large Once in May and once in September  Edging and trimming of planted areas to Vegetation Vegetation growing beyond facility edge onto control groundcovers and shrubs from sidewalk, paths and street edge overreaching the sidewalks, paths and street edge improves appearance and reduces clogging of permeable pavements by leaf litter, mulch and soil. Leaves, Leaf Litter In fall (October to December) after leaf drop  Use leaf blower or vacuum to blow or remove Needles, and (1-3 times, depending on canopy cover) leaves, evergreen needles, and debris (i.e., Organic Accumulation of organic debris and leaf litter flowers, blossoms) off of and away from Debris permeable pavement

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Perforated Stub-out Connection

A perforated stub-out connection is a length of perforated pipe within a gravel-filled trench that is placed between roof downspouts and a stub-out to the local drainage system. The figure below illustrates a perforated stub-out connection. These systems are intended to provide some infiltration during drier months. During the wet winter months, they may provide little or no flow control.

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Perforated Stub-out Connections – Recommended Maintenance Protocols Drainage Potential Conditions When Maintenance Is Needed Required Maintenance and Expected Results System Defect Feature

General Trash and Any trash and debris which exceed 1 cubic Trash and debris cleared from site. Debris foot per 1,000 square feet. In general, there should be no visual evidence of dumping. If less than threshold all trash and debris should be removed as part of next scheduled maintenance. Poisonous/ Any poisonous our nuisance vegetation which No danger of poisonous vegetation where Noxious may constitute a hazard to maintenance maintenance personnel or the public might Vegetation personnel or the public. normally be. (Coordinate with local health department). Any evidence of noxious weeds as defined by State or local regulations. Complete eradication of noxious weeds may not be possible. Compliance with State or local (Apply requirements of adopted IPM policies eradication polices required. for the use of herbicides). Contaminants Any evidence of oil, gasoline, contaminants or No contaminant or pollutants present. and Pollution other pollutants.

(Coordinate removal/cleanup with local water quality response agency. Rodent Holes Any evidence of rodent holes Holes filled.

Storage Area Sediment Water ponding in infiltration area after rainfall Sediment is removed and/or facility is cleaned so ceases and appropriate time allowed for that infiltration system works according to infiltration. design.

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