Stormwater Facilities Inspection and Maintenance Handbook

Stormwater FacilitieS Inspection and Maintenance Handbook

About

Table of Contents Whatcom County has numerous valuable aquatic natural resources that supply drinking water, and economic and recreational opportunities for the citizens of Whatcom County. Protecting the County’s drinking water supplies, preserving and restoring aquatic habitat for threatened About ...... 1 and endangered aquatic life, and protecting public infrastructure Introduction and private property are the primary factors behind the creation and What is stormwater? ...... 2 implementation of this National Pollution Discharge Elimination System Why is stormwater a concern? ...... 3 (NPDES) Phase II Stormwater Management Program. Low-impact Development (LID) The purpose of this handbook, part of the NPDES stormwater program, Water infiltration on your property...... 4 is to provide home owners’ associations and other owners of private Slow it down, spread it out, soak it in...... 5 community stormwater systems with information on how to inspect and Stormwater Systems maintain their stormwater facilities. Included are an introduction to Why inspect and maintain stormwater systems?...... 6 stormwater management concerns, descriptions of typical stormwater Understanding stormwater systems ...... 7 facilities, and general guidelines for inspecting and maintaining a com- Guidelines for maintaining stormwater systems ...... 8 munity stormwater system. More about your stormwater system ...... 9 Maintaining Your System This handbook is a resource to help determine what maintenance ac- Best management practices (BMPs) ...... 10 tions are needed to ensure stormwater systems are functioning properly Type 1 catch basins...... 11 and when to seek professional help for maintenance or repairs. If your Type 2 catch basins...... 12 stormwater system has an engineer’s operation and maintenance plan Conveyances and bioswales ...... 13 (O&M plan), this handbook can provide general information to help you Stormwater ponds...... 17 understand your O&M plan, but it is not intended to replace any specific Stormwater pond components...... 18 recommendations made by your plan. Pond cell...... 21 Properly maintained stormwater systems save money, help protect wa- Pond structure ...... 22 ter quality, minimize potential liability, and reduce the risk of flood- Vegetation in and around the pond...... 24 ing. High or low water levels...... 27 Access and safety...... 28 Costs...... 29 References and Resources ...... 30 Glossary ...... 31 Inspection Schedule & Checklist...... 34 NPDES Area Map ...... 39

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About

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Introduction Introduction

What is stormwater? Why is stormwater a concern?

Stormwater is a concern for two reasons: faster run- clude oil, heavy metals, pesticides and excess nutri- off leads to flooding and pollution. In western Wash- ents (like nitrogen or phosphorus in fertilizer), all of ington, stormwater is a special concern due to our which can degrade water quality and harm or kill fish wet climate and rapid rate of urbanization. and aquatic wildlife. Stormwater is the largest source of pollution in Puget Sound. Faster runoff: Water runs off impervious surfaces much faster than in natural areas. This means that With the rapid increase in impervious surfaces and when it rains or snow melts, there are larger volumes development in Whatcom County, the potential for more stormwater and stormwater pollution increases Photo: RE Sources of water flowing faster in creeks and rivers. These increased volumes and faster flows often lead to ero- every day. To reduce the negative impacts that de- Stormwater systems are designed to help keep pollutants like sediment out of receiving waters sion that can damage stream banks, cause local velopment has on stormwater, the County requires flooding, undercut roads or buildings, and reduce most new developments to create stormwater treat- property values. ment systems. Stormwater is precipitation that runs off of captured by vegetation or able to pool in wet- any surface it can't seep into. Most stormwater lands, where it can slowly seep into the Pollution transport: Stormwater does not originate runs off surfaces such as roads, sidewalks, ground. Wetlands include swamps, marshes, from a single source like a discharge pipe, so it can highways, parking lots, and rooftops. bogs, and similar areas that are saturated with pick up pollution as it flows across impervious sur- water for most of the year. faces in residential or industrial areas. Activities such One solution? LID on site. As we expand our cities, roads, parking lots, your as home construction, outdoor machinery mainte- and industries, we create more impervious In many developed areas of Whatcom County, nance, driving, lawn fertilizing and car washing con- surfaces (surfaces that water cannot pene- the wetlands and native soils have been filled tribute pollutants to stormwater. These pollutants in- trate) thereby changing the way water moves or drained for previous development so that through the landscape. very little stormwater can be absorbed.

Before large areas of Whatcom County were How do stormwater ponds and wetlands compare? Stormwater developed, forests and open spaces absorbed Pond Wetland rainwater. In a natural landscape, water is Help prevent flooding and downstream property damage Stormwater treatment in an undeveloped landscape (left) and in a developed landscape Protect water quality via physical and chemical processes

Provide water storage

Maintena nce free

Have a stable water level

Provide high-quality wildlife habitat

Have diverse plant community and species diversity Photo: RE Sources Photo: RE Sources

A natural wetland A constructed detention pond

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Introduction Introduction

What is stormwater? Why is stormwater a concern?

Provide water storage

Maintena nce free

Have a stable water level

Provide high-quality wildlife habitat

Have diverse plant community and species diversity Photo: RE Sources Photo: RE Sources

A natural wetland A constructed detention pond

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as habitat, as Photo: Cypress Designs and replacing them with perme- amenity. permeable. Why? Because the tive trees and shrubs are adapted to our climate, re- able surfaces, you will allow for soil in most lawns is com- quire low maintenance, capture lots of water, and Install a rain barrel: A rain barrel even more water infiltration. - The Integrated pacted, and because grass help build soil structure better than lawns. Native collects and stores rainwater from Pond Photo left: a permeable driveway, your roof to use for things like water- roots are short. Short rooted plants often have berries and seeds, attracting birds removed lawn, pervious walk- plants in compacted soil do not and other wildlife. ing your garden. Water is diverted ways and pavement. from your roof's downspout, where it promote water infiltration, so a lot of water runs off When properly designed and constructed, rain gar- would normally flow to the ground or lawns. Photo: RE Sources dens drain rapidly with surface water present for only a stormwater collection system, into the rain barrel for later use. The roots of shrubs and trees can go deep into the 1-2 days. Mosquitoes take a minimum of about 4 soil, breaking up compacted layers, allowing more days (many types of mosquitoes take several days water to infiltrate deep into the ground. Water col- longer) to become adults after eggs are deposited in Install a French drain: A French drain is a trench in the lects on the surfaces of leaves and branches, allow- water. ground that collects water from your roof, and allows ing evaporation. The rain that makes it to the ground infiltration. French drains can take somewhat different through large plants is mostly ab- A typical rain garden (below) forms but generally consist of a trench with a perforated drain pipe surrounded by drain rock and filter fabric or sand. Photo: Drainage Masters

Install a rain garden: A rain garden is a planted depression that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, parking lots, and compacted

Photo: RE Sources lawn areas the opportunity to be absorbed.

Source: Anatomy of a rain garden, page 4 of Rain Garden Handbook for Western Washington

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Low-impact Development Low-impact Development Water infiltration on your Slow it down, spread it out, soak it in property Bioretention is an integrated stormwater management practice that uses plants, microbes, and soils to remove and re- Low-impact development (LID) is a way to manage tain pollutants from stormwater. All you have to do is slow it stormwater right on your property by encouraging down, spread it out, and let it soak in. Here are some great water to infiltrate, rather than diverting it. By decreas- ways to do it: ing the amount of compacted soil and impervious surfaces on your lot, you can encourage water to Photo: RE Sources Remove lawn, then install stay on your property instead of Seattle’s SEA Street, an example of an urban area native plants, pervious Stormwater is adding to stormwater run off. with multi-layered trees and shrubs walkways and pervious pavers: not wastewater, By replacing your lawn with deep The easiest way to promote it is a resource – sorbed by the plant roots. rooted plants, you will be promot- infiltration is by adding a variety as potential ing infiltration. Consider a green ground water, as of shrubs and trees on your Increasing the variety of deep rooted plants is one of roof for your garage or other unpolluted water, property. Grassy lawns are the best things people can do to reduce stormwater structures. By removing paved generally considered to be im- flows, and using native plants is a great choice. Na- walkways, patios, and driveways, as habitat, as Photo: Cypress Designs and replacing them with perme- amenity. permeable. Why? Because the tive trees and shrubs are adapted to our climate, re- able surfaces, you will allow for soil in most lawns is com- quire low maintenance, capture lots of water, and Install a rain barrel: A rain barrel even more water infiltration. - The Integrated pacted, and because grass help build soil structure better than lawns. Native collects and stores rainwater from Pond Photo left: a permeable driveway, your roof to use for things like water- roots are short. Short rooted plants often have berries and seeds, attracting birds removed lawn, pervious walk- plants in compacted soil do not and other wildlife. ing your garden. Water is diverted ways and pavement. from your roof's downspout, where it promote water infiltration, so a lot of water runs off When properly designed and constructed, rain gar- would normally flow to the ground or lawns. Photo: RE Sources dens drain rapidly with surface water present for only a stormwater collection system, into the rain barrel for later use. The roots of shrubs and trees can go deep into the 1-2 days. Mosquitoes take a minimum of about 4 soil, breaking up compacted layers, allowing more days (many types of mosquitoes take several days water to infiltrate deep into the ground. Water col- longer) to become adults after eggs are deposited in Install a French drain: A French drain is a trench in the lects on the surfaces of leaves and branches, allow- water. ground that collects water from your roof, and allows ing evaporation. The rain that makes it to the ground infiltration. French drains can take somewhat different through large plants is mostly ab- A typical rain garden (below) forms but generally consist of a trench with a perforated drain pipe surrounded by drain rock and filter fabric or sand. Photo: Drainage Masters

Install a rain garden: A rain garden is a planted depression that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, parking lots, and compacted

Photo: RE Sources lawn areas the opportunity to be absorbed.

Source: Anatomy of a rain garden, page 4 of Rain Garden Handbook for Western Washington

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Stormwater Systems Stormwater Systems

Why inspect and maintain stormwater systems? Understanding stormwater systems

Stormwater systems include a variety of Regardless of its complexity, most stormwater stormwater facilities that convey, slow, filter, systems will include conveyances like pipes There are many reasons to regularly inspect and maintain your stormwater system. If you or infiltrate (absorb) stormwater runoff. Storm- and ditches that move stormwater from one maintain your stormwater system, you will help protect downstream water quality and habi- water systems can be simple or complex. A place to the next; catch basins that regulate tat for wildlife and people to enjoy. In addition to keeping water clean, a well-maintained small residential development may have one or the speed that stormwater moves through the stormwater facility will help protect downstream properties from potential flood or erosion two ditches and a single stormwater pond. A system and help settle out trash and sediment; damage. A little bit of maintenance goes a long way—if you keep up with some simple large development may have a network of and ponds that help filter and reduce the rate tasks, you may avoid having to pay for expensive repairs in the future. ditches, buried pipes, catch basins and ponds. of flow of stormwater. By maintaining every facility in your stormwater system you will:

Save money—Identifying and correcting potential problems early will save As a property owner, you you money by reducing long-term maintenance costs. It’s much easier are required to follow the to prevent maintenance problems than it is to fix them once the dam- maintenance tasks and age is done. schedule specified in the A stormwater system is a series of connected operations and mainte- Protect water quality—Properly inspecting and maintaining your storm- stormwater facilities that convey, slow, filter, or nance (O & M) plan for water system is an important action you can take to keep water clean infiltrate (absorb) stormwater runoff from your your facility. Whatcom and safe in your watershed. Making sure pollutants such as sediment, property, then release that stormwater to surface County Code contains litter, oil, or animal waste stay out of your stormwater system will en- waters or other stormwater systems. requirements for mainte- sure the water leaving your system is as clean as possible. Remem- nance of private storm- ber, stormwater does not go to the sewage treatment plant. It flows to water facilities, and the the nearest stream or beach. federal Clean Water Act, How does water move through a Safe Drinking Water Act, Minimize potential liability—Local, State and Federal regulations require typical development’s stormwater and Endangered Species privately owned stormwater systems be properly maintained and pol- facilities? Act all require states to luted water and sediments removed during cleaning be disposed of manage stormwater run- properly. Property owners could be liable for polluted discharge from As an example (at left), this stormwater off to protect water quality stormwater systems. system captures stormwater at street in rivers and streams. level in Type 1 catch basins and pipes it Reduce flooding and erosion—A properly functioning stormwater sys- to the two detention ponds at center of tem is also less likely to fail and cause erosion or flooding during a big the photograph. The detention ponds storm. slow and control the flow of stormwater The wastewater from our homes—sinks, toilets, dishwashers and the like— into natural water bodies. This system goes to a sanitary sewer treatment facility or septic system before it’s released includes catch basins, pipes, detention into our waterways. Stormwater, however, travels through our local catch ba- ponds, and a biofiltration swale. sins, into our storm drain system and into Puget Sound itself. If our streets, rooftops and private stormwater facilities are dirty, then our local waters will be too. Photo of a Whatcom County subdivision. Stormwater If we all work to decrease litter, animal waste, oil waste and other pollutants, flows into catch basins and is transported in the di- and keep our stormwater facilities properly maintained, then we can help pro- rection of the flow arrows to the two ponds located in tect marine water quality as well as the freshwater tributaries and wetlands the middle of the development. (Source: Whatcom that private stormwater facilities often discharge to. County Public Works)

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Stormwater Systems Stormwater Systems

Why inspect and maintain stormwater systems? Understanding stormwater systems

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Stormwater Systems Stormwater Systems

Guidelines for maintaining stormwater systems More about your stormwater system

Properly main- Know where the water flows—Develop a good understanding of Depending on when your stormwater system was Operation and Maintenance (O&M) Plans built, you may have access to engineering docu- tained storm- your stormwater system by following stormwater runoff as it en- An operation and maintenance plan (O&M plan) is a water systems ters and flows through your community during a rainstorm. Be ments that should be used to help you properly inspect and maintain your stormwater system. technical manual written by an engineer containing save money, sure to note where the stormwater goes once it leaves your sys- specific directions on how to best maintain your tem. help protect As-built (record) drawings stormwater system. Only newer developments will water quality, have a complete stormwater system O&M plan. How- and reduce Stop pollution at its source—The easiest way to protect water An as-built drawing, or record drawing, is a technical ever, when one is available, it should be used as drawing that shows how your stormwater system was the risk of quality and save on cleaning costs is to keep pollutants from your primary reference on how to best inspect and built and documents any changes made to the origi- flooding. entering your stormwater system. maintain your stormwater system. This handbook nal system design during the construction process. may provide additional details and information about These drawings are usually signed and stamped by a Sweep—Sweeping driveways clean instead of using a hose conducting inspections, schedules, and maintenance professional engineer and are a great reference that or covering loose soil with a tarp keep sediment and tasks not found in your O&M plans or it may help you will help you determine the size and location of the other pollutants out of your stormwater system. better understand the recommendations made in components of your stormwater system. If you are your plan. Keep yard debris out of ditches—Grass clippings or part of a large housing development, you might have branches from pruning should be kept away from your a series of as-built drawings in different sizes or Contact the Whatcom County Public Works Storm- stormwater system. Yard debris can cause problems by scales. water Division if you need help locating copies of the documents for your stormwater system. adding pollutants like fertilizer or animal waste to stormwater or causing flooding by blocking culverts, ditches, or pipes.

Look for blockages—Watch for debris or litter blocking the flow of stormwater through your system and remove it as soon as possible before it becomes a problem.

Determine your level of responsibility—The ownership of stormwater systems varies between different housing developments in Whatcom County. The best way to determine what you are responsible for maintaining is to read the plat conditions for your development. Some homeowners’ associations may have these records available. If you need assistance finding your plat conditions, contact Whatcom County Public Works Stormwater Divi- sion.

Regularly inspect and maintain your stormwater system— Follow the guidelines presented in this handbook to ensure your stormwater system is functioning properly.

Your as-built drawing from county files will have many important details.

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Stormwater Systems Stormwater Systems

Guidelines for maintaining stormwater systems More about your stormwater system

Look for blockages—Watch for debris or litter blocking the flow of stormwater through your system and remove it as soon as possible before it becomes a problem.

Regularly inspect and maintain your stormwater system— Follow the guidelines presented in this handbook to ensure your stormwater system is functioning properly.

Your as-built drawing from county files will have many important details.

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Maintaining Your System Maintaining Your System

Best Management Practices (BMPs) Type 1 catch basins

Inspection Frequency: Exterior: Monthly (weekly when Proper maintenance of your stormwater facility be- Throughout the rest of this section, you will be able leaves are falling) & after storms, Interior: Annually

gins with the understanding of the term “best man- to read about each type of stormwater facility, see Photo: RE Sources agement practices,” or BMPs, for short. For stormwa- what it looks like, and understand the BMPs that will Stormwater from streets drains into small under- You will often see fabric filters placed in these catch ter systems, BMPs are ways to prevent or reduce the ensure it functions properly and lasts as long as pos- ground vaults called Type 1 catch basins. These basins near construction sites. These filters are amount of pollution travelling through or leaving the sible. See pages 35 and 36 for a checklist to use are installed in the center of a street or along the designed to keep out large debris but do not capture system. BMPs can also reduce stormwater facility when inspecting and maintaining your stormwater street curb or gutter. Type 1 catch basins are some- silt or other fine material. They should be changed maintenance costs. system. whenever they are torn and monitored in case they times called “storm drains.” become clogged. Filters should be removed after BMPs are separated into two categories: source con- Keeping records of inspections is very important. It A catch basin consists of a grate on the road surface construction is complete. trol and treatment BMPs. Source control BMPs pre- allows a homeowners association or community to with an underground vault beneath it. Stormwater vent pollution by controlling pollutants at their source. keep up with an inspection schedule, review data Reminder: Catch basins in private roads are the collects in the vault, allowing sediment to settle on Treatment BMPs are used to treat stormwater that is collected during past inspections, and estimate when owners’ responsibility; catch basins in county roads the bottom. Water from the catch basin flows through already polluted. Source control BMPs are always routine maintenance is needed. Inspection checklists are county responsibility. pipes to a variety of destinations: into a swale, a more effective than treatment BMPs because they and all records should be kept with the O & M plan stormwater pond, or directly into a river or stream. Type 1 and 2 catch basins are prevent pollution from entering the water, whereas and as-built drawings for your stormwater system. designed to catch debris and regulate treatment BMPs rely on cleaning up the water after it Check catch basin grates regularly as they can be- flow. They both can protect receiving has been polluted. Ongoing, regular maintenance activities are different from inspection. Regular, ongoing maintenance come clogged with litter or leaves. Remove trash, waters such as bays, streams, and If you can promote source control BMPs that keep should include activities like vegetation management debris, and sediment from the vicinity so it won’t en- wetlands. debris and sediment out of the stormwater facility, and/or mowing side slopes and pond shorelines; in- ter the basins. Remove the grate to check the accu- Type 1 catch basins are usually found you will reduce maintenance costs. To keep debris spections will find problems that need to be fixed. mulation of sediment in the vault. When sediment before a stormwater pond, protecting and sediment out of your stormwater facility, practice exceeds 60% of the vault depth or comes within 6” of the lowest pipe, the catch basin needs to be cleaned the inlet and pond from debris. good housekeeping (see box below). (Dept. of Ecology: Volume V, February 2005). Con- Type 2 catch basins are usually found tact a professional to clean the catch basin with a at the outlet of a stormwater pond, pro- vactor truck. During the dry season, sediment can be tecting downstream waters by trapping removed by hand with a bucket and shovel. Follow excess sediment before it leaves a recommendations in Appendix IV-G of the Dept. of pond. Good Housekeeping BMPs Ecology’s Stormwater Management Manual for Western Washington for disposal of the sediment.  Sweep and remove trash and sediments from the streets.  Sweep and remove sand from winter sanding operations when no longer needed. BMPs for Type 1 Catch Basins  Ensure that roofers sweep and remove grit from roads after completing Remove trash and sediment from a roofing job. Grate Replace if broken around grate  Rake and pick up leaves from lawns.  Cover soil piles from construction or landscaping efforts. Change if torn; monitor for block- Filter ages and remove or clean if re-  Place yard waste and compost out of the path of drainage ways. stricting flow into the basin

Remove sediment if it fills >60% of Inside Remove trash and debris if present the vault or is full to within 6” of the lowest pipe

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Maintaining Your System Maintaining Your System

Best Management Practices (BMPs) Type 1 catch basins

Remove sediment if it fills >60% of Inside Remove trash and debris if present the vault or is full to within 6” of the lowest pipe

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Maintaining Your System Maintaining Your System

Type 2 catch basins Conveyances & bioswales

Inspection Frequency: Exterior: Monthly Inspection Frequency: Quarterly and after storms & after storms, Interior: Annually All stormwater systems contain conveyance facilities that move stormwater from one location to another. DO NOT ENTER Type 2 CATCH BASINS! They Photo: RE Sources Conveyance facilities include bioswales, ditches, are confined spaces and can be dangerous! Control structure inside a Type 2 catch basin check dams, and buried pipes and culverts. Contact a trained professional for needed maintenance or repairs. A bioswale, or vegetated swale, is a grass lined Ecology’s Stormwater Management Manual for swale that is designed to improve water quality. It A Type 2 catch basin is a large concrete manhole Western Washington. filters surface water through the grass or selected structure that varies from 4’ to 8’ in diameter and up vegetation. A bioswale is a form of bioretention, and to 20’ deep. A Type 2 catch basin functions both to Once cleaned, look for cracks in basin walls or bot-

is similar to a rain garden. The difference between a Photo: RE Sources control flow from a detention pond and as a final de- toms. If catch basin covers are missing or only par- bioswale and a rain garden is that bioswales have a pository for sediments and pollutants before storm- tially in place, repair. If the basin contains a ladder, slight slope, allowing them to convey stormwater run- A bioswale planted with wetland plants water exits the pond. check ladder rungs for strong attachments and integ- off to another destination, such as a ditch, culvert, or rity. Look for presence of any pollutants (including Determine the location of these catch basins from rain garden. They are often used as an alternative to, trash, paint, auto fluids, grease and food waste). If your O & M plan or by getting out there and finding any vegetation is growing inside the catch basin, them. Gather a flashlight and the tools needed to re- remove it. move catch basin covers. For Type 2 catch basins, remove the cover using a manhole cover lifter. Use a Inside many Type 2 catch basins is a pipe called an long iron bar or rebar to check the depth of sediment. orifice or flow restrictor. It controls the flow and discharge of water from the catch basin and detention If trash, debris, or sediment exceeds one-third the pond. depth from the bottom of the basin to the bottom of the lowest pipe into or out of the basin, it should be When inspecting inside the Type 2 catch basins, removed by a vactor truck (Thurston County: Main- check the integrity of the orifice plate and overflow taining Catch Basins and Dept. of Ecology, Volume pipes. If any of these components are missing, bent, V, February 2005). As with sediment removed from or out of place, they should be replaced. If any trash, debris, sediment, or vegetation is blocking the plate,

Type 1 catch basins, special disposal requirements Photo: RE Sources may apply. Follow the recommendations for disposal remove it. of street wastes in Appendix IV-G of the Dept. of Photo: RE Sources A bioswale with perpendicular weirs A bioswale under construction BMPs for Type 2 Catch Basins velopments, roadsides, and parking lots. or an enhancement of, traditional stormwater piping. Remove trash and vegetation that Most bioswales look like a wide, vegetated ditch. Bioswales vary in size and shape, but most of the Grates or inlets Replace if broken may be obstructing Most of the time, they are vegetated with a variety of time, they are linear. In locations that have well grasses or other perennial plants. drained soils, bioswales can be built with ditch If sediment exceeds one third of Remove trash, vegetation, and de- blocks, or perpendicular weirs, such as in this photo. Inside the depth from the floor to the out- In some settings, bioswales are planted with wetland bris if present Weirs and blocks help slow down water flow, promot- let pipe, remove plants and shrubs. The bioswale in this photo is ing infiltration. Bioswales are usually seeded with a about 100 feet long. The water that doesn’t get ab- Check ladder rungs, orifice, and special seed mix that is capable of tolerating wet and Look for cracks in wall or bottom sorbed in this bioswale gets discharged into a road- Structure cleanout grates. Have repaired as dry conditions. Have repaired as necessary side ditch, and into a stream. Bioswales can be incor- necessary porated into lots of settings, such as homeowner de-

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Maintaining Your System Maintaining Your System

Type 2 catch basins Conveyances & bioswales

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Undercutting: When the top edge of a Even though many pipes are underground, it is impor- Maintaining Your System stream bank or ditch side extends further out Maintaining Your System tant to know approximately where they’re located, and than the underlying bank to regularly check that they’re not getting filled with sediment, rocks, or other material. Find pipe locations, Conveyances & bioswales Scouring: Stream bank or ditch side erosion Conveyances & bioswales ditches, check dams, and culverts by reading your O & (continued) caused by high-velocity water M plan or by walking your stormwater system, prefera- (continued) bly during a rain event. At the places where pipes and Slumping: Where a landform settles or Inspection Frequency: Quarterly and after storms conveyance systems are exposed, note accumulation slides, usually due to saturated soil of sediment or other blockages. Maintaining your bioswale If sediment or blockages are found, contact a storm- The single most important task is to maintain the water system or out to receiving waters. They may water professional who can flush the pipes with water plants - these protect the facility, and do all the work! be U-shaped, or trapezoidal with a flat bottom. during the dry season. It’s important to hire a profes- Regular inspection of bioswales should be conducted sional to do this, as flushing the system incorrectly Ditches are commonly lined with grass or rock. to identify signs of erosion, accumulation of trash and could overload a stormwater pond or transport pollu- Grass helps trap sediment, improving water quality, debris near pipes, and signs of excessive sedimentation to the receiving waters. tion. Some bioswales are designed with a mix of and should be maintained in the ditch. However, if plants, including small shrubs. Most bioswales are grass or other vegetation start to restrict water flow in Stormwater culverts can be plastic, concrete or metal. lined with grass or non-woody plants. If there are the ditch or cause drainage problems, it should be Look for dented, rusted, or broken edges of culverts, and for rocks that have been moved by strong flows of bare spots or erosion, repair these by applying an mowed or trimmed back. Grass taller than 9”, trees, water. If found, replace rocks in original location. appropriate seed mix. It is important to know what or shrubs may impede the flow of water. type of plants your bioswale was designed for so that Never dump yard waste in ditches. Look for and re- you can maintain the plants appropriately. Keep Photo: Whatcom County Public Works Photo: Whatcom County Public Works trees and deep rooted plants out of your bioswale. A check dam should stretch across the whole ditch Remember, grass likes sun – if your grass is shaded, your bioswale may not function correctly. tion, check for integrity of check dams, if they are present. Ditches Pipes and culverts Properly functioning ditches and pipes are critical to your facility, because without them, water would stay Most stormwater systems use pipes to convey water in place. underground, and culverts to route water under roads Photo: RE Sources and driveways. Pipes are also used to connect catch Ditches let water move between parts of the storm- basins turn corners and route stormwater into other

conveyance systems. Photo: RE Sources Too many trees as above will slow down and block water flow Time to remove sediment

move trash, debris, yard waste, and accumulated If there is evident sediment build-up on the bottom of sediment. Maintain the ditch so that the ditch profile the culvert, it is probably time to remove sediment. matches the original design. Keep trees, and tree roots, away from culverts and pipes. Willow roots are especially bad because they At places where ditches or streams drop in elevation, can completely block the flow of water. If roots are evi- there will usually be one or a series of small rock dent, remove them using a mechanical auger with a berms called check dams installed across the ditch rotating head that can cut roots inside a pipe; profes- to help slow down the velocity of the water, prevent- sionals are available for these services. ing erosion.

Photo: RE Sources Reminder: Conveyances along private roads are the Locate ditches by walking your stormwater system Photo: Whatcom County Public Works owners’ responsibility; conveyances along county A well-maintained ditch with new vegetation lay- and/or reading your O & M plan. As you walk along roads are county responsibility. ered on the bottom your ditch, look for undercutting, scouring, and A pipe entering a catch basin slumping. At the places where ditches lose eleva-

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conveyance systems. Photo: RE Sources Too many trees as above will slow down and block water flow Time to remove sediment move trash, debris, yard waste, and accumulated If there is evident sediment build-up on the bottom of sediment. Maintain the ditch so that the ditch profile the culvert, it is probably time to remove sediment. matches the original design. Keep trees, and tree roots, away from culverts and pipes. Willow roots are especially bad because they At places where ditches or streams drop in elevation, can completely block the flow of water. If roots are evi- there will usually be one or a series of small rock dent, remove them using a mechanical auger with a berms called check dams installed across the ditch rotating head that can cut roots inside a pipe; profes- to help slow down the velocity of the water, prevent- sionals are available for these services. ing erosion.

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Maintaining Your System Maintaining Your System

Conveyances & bioswales Stormwater ponds (continued) Stormwater ponds are engineered systems that development, the amount of impervious surfaces, the BMPs for Conveyances (bioswales, ditches, pipes and culverts) mimic the natural process in wetland systems. soil type, the average rainfall rate, the topography, Stormwater ponds create a place for water to collect and other considerations. All conveyances Remove trash, yard debris, and excess Remove sediment if it impedes water and for sediments and other contaminants to settle vegetation flow before flowing to a natural watercourse. The primary reason to maintain your stormwater pond is to make sure that its storage capacity is Like in a wetland, some stormwater pollutants can maintained and it’s not getting filled in with sediment. Vegetation: bare patches should not ex- If vegetation growth is sparse, determine also be “treated” in stormwater ponds. Pollutants We will talk more about sediment in the following ceed 10% of swale bottom. Don’t allow why, and replant such as sediment and debris settle to the bottom of sections. excessive shading. Re-seed bare areas, the pond and can be removed at a later time. Other and increase amount of sunlight reaching pollution such as excess nutrients are taken up by a swale, if necessary variety of plants and microorganisms. Other contami- Check inlets and outlets for debris Remove debris that causes clogging or nants bind with soil particles through a process blockage called sorption.

level from side to side, and should drain Dry ponds are designed to hold water temporarily freely towards outlet after a storm, releasing the water slowly then drying out between storm events (EPA Stormwater Menu of If standing water remains in between Check for standing water BMPs). storms, remove sediment or blockages, or other drainage problems Water storage capacity is the amount of water your Photo: RE Sources Repair undercutting, scouring, and See definition in sidebar stormwater pond is designed to contain, and it’s the slumping most important design aspect of your stormwater system. An engineer designed your pond to have a A one stage constructed stormwater pond Ditches Inspect vegetation, don’t allow vegetation Check for integrity of grass, check dams, specific storage capacity based on the area of your to impede water flow inlets, and outlets. Remove shrubs and trees. Inspect for accumulation of sediment Inspect for accumulation of sediment If sediment exceeds 20% of diameter, clean pipes and culverts

Inspect for vegetation overgrowth Remove vegetation if it reduces the free Pipes and culverts movement of water

Inspect for damaged joints, dents, or rust Repair accordingly. Any dent that de- creases the pipe’s cross section by more than 20% should be repaired.

Check formation of dams and replace Check dams

rocks if necessary Photo: RE Sources

A two stage constructed stormwater pond with berm

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Maintaining Your System Maintaining Your System

Bioswales There are two types of stormwater ponds. Wet Check for accumulation of sediment. If sediment exceeds 2” beyond design ponds are designed to have a permanent pool of depth, remove. Swale bottom should be water, or at least a pool throughout the wet season. level from side to side, and should drain Dry ponds are designed to hold water temporarily freely towards outlet after a storm, releasing the water slowly then drying out between storm events (EPA Stormwater Menu of If standing water remains in between Check for standing water BMPs). storms, remove sediment or blockages, or other drainage problems Water storage capacity is the amount of water your Photo: RE Sources Repair undercutting, scouring, and See definition in sidebar stormwater pond is designed to contain, and it’s the slumping most important design aspect of your stormwater system. An engineer designed your pond to have a A one stage constructed stormwater pond Ditches Inspect vegetation, don’t allow vegetation Check for integrity of grass, check dams, specific storage capacity based on the area of your to impede water flow inlets, and outlets. Remove shrubs and trees. Inspect for accumulation of sediment Inspect for accumulation of sediment If sediment exceeds 20% of diameter, clean pipes and culverts

Inspect for vegetation overgrowth Remove vegetation if it reduces the free Pipes and culverts movement of water

Inspect for damaged joints, dents, or rust Repair accordingly. Any dent that de- creases the pipe’s cross section by more than 20% should be repaired.

Check formation of dams and replace Check dams rocks if necessary Photo: RE Sources

A two stage constructed stormwater pond with berm

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Maintaining Your System Maintaining Your System

Stormwater pond components Stormwater pond components

celled (two-stage) ponds, sediment in the stormwater Photo: RE Sources The spillway is a low area, constructed with rock or runoff will usually settle in the first cell. Vegetation and obstructions should be concrete, in a low area of the pond wall that allows Maintaining inlets and outlets removed from clogged inlets Stormwater ponds always have an inlet, outlet, and for “spillover” if the water level gets too high in the Find your inlets and outlets by walking around the spillway. The inlet is the point where stormwater en- pond. Without this safety feature, the pond walls pond. Remove all trash and vegetation that is blocking ters the pond. Inlets are often covered with a debris could be damaged if the water level gets too high. the inlet or outlet. If there is evidence of erosion or barrier (trash rack). The outlet is the structure scour around either the inlet or outlet, determine and remedy its cause. If rip-rap is present below the outlets, check to see that all rocks are in place.

Check that there is no evidence of sediment reaching the receiving waters. If there is, determine its cause by a thorough inspection and correct the problem.

Debris barrier (trash rack) Photo: RE Sources Beneath the outlet pipe is a pad of large Annually Inspection Frequency: rock, an energy dissipater, that slows fast-moving water. There may also be a dissipater below the inlet to your pond. A debris barrier (or trash rack) is a metal rack located at the entrance to a pipe or culvert or on an outlet control structure. These prevent trash, wood, and other debris from entering pipes, stormwater ponds, or outlet structures. If your facility does not have a trash rack located on its inlet or outlet pipe, you should consider installing one to prevent plug- ging.

If trash or debris is blocking more than 20% of the openings in the barrier, remove (Dept. of Ecology: Volume V, February 2005, and Pierce County Storm- water Maintenance Manual). If bars are missing, bent, or excessively rusty, replace them. If the barrier Photo: RE Sources is not firmly attached, repair it. A trash rack or debris barrier should be cleared of vegetation, trash, and other debris

Example of a constructed stormwater pond (Source: Pierce County Stormwater Manual)

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Stormwater pond components Stormwater pond components

Most older stormwater ponds contain a single ba- through which water exits the pond, allowing for con- (continued) sin, often called a cell. Newer ponds may contain trolled release of water from the pond into another two cells separated by a low berm. In most cases, water course, usually a ditch or a stream. A Type 2 Inlets and outlets the berm forces water to slow down, causing parti- catch basin is often present as part of the outlet cles of sediment to settle out in the first cell. In two- structure. Inspection Frequency: Quarterly and after storms celled (two-stage) ponds, sediment in the stormwater Photo: RE Sources The spillway is a low area, constructed with rock or runoff will usually settle in the first cell. Vegetation and obstructions should be concrete, in a low area of the pond wall that allows Maintaining inlets and outlets removed from clogged inlets Stormwater ponds always have an inlet, outlet, and for “spillover” if the water level gets too high in the Find your inlets and outlets by walking around the spillway. The inlet is the point where stormwater en- pond. Without this safety feature, the pond walls pond. Remove all trash and vegetation that is blocking ters the pond. Inlets are often covered with a debris could be damaged if the water level gets too high. the inlet or outlet. If there is evidence of erosion or barrier (trash rack). The outlet is the structure scour around either the inlet or outlet, determine and remedy its cause. If rip-rap is present below the outlets, check to see that all rocks are in place.

Check that there is no evidence of sediment reaching the receiving waters. If there is, determine its cause by a thorough inspection and correct the problem.

Example of a constructed stormwater pond (Source: Pierce County Stormwater Manual)

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Stormwater pond components Pond cell

(continued) Inspection Frequency: Monthly

Spillway The pond cell is the one- or two-part basin that re- tains water while trapping sediment. In the pond it- Inspection Frequency: Annually self, you can inspect the water in the wet season for Photo: RE Sources trash and debris, oil sheen, excess vegetation (see Water only passes over the spillway when pages 24-26) and algae. Photo: RE Sources While walking around the perimeter of the pond, look the pond fills up. Well-trimmed vegetation makes a detention for the lowest area – this is the spillway. Carefully General pond maintenance check this area and all berms over 4’ in height. If any Below the spillway, there is often an energy dissi- pond’s outlet and fencing clearly visible. trees or shrubs are growing here, remove them. If pater consisting of layers of rock that the exiting wa- Any time you see trash and debris, it should be only one layer of rock exists above native soil in any ter falls on. If only one layer of rock exists above na- removed because it can clog pipes in the outlet con- portion of the spillway, or if any native soil is ex- tive soil, or if any native soil is exposed, add more trol structure, but at a minimum check and remove Many ponds become stagnant during the summer posed, add more rocks and restore the area to de- rocks to the area. If there is evidence of erosion near trash monthly and after storm events. months, allowing a layer of algae to grow. Algal sign standards (Dept. of Ecology: Volume V, Febru- the rock pad, repair it. mats interfere with dissolved oxygen content in the If you observe an , it should be removed ary 2005). oil sheen water and pose a threat to downstream water re- by use of oil-absorbent pads or a professional with a sources. If algal mats develop over 10% of the water Check for piping and erosion. If there is any discern- vactor truck. Locate the source of the oil and correct Piping is an engineering term used for surface, they should be removed (King County able water flow through the pond berm, consult a civil it. Special disposal requirements may apply. water that moves through a channel or Drainage Maintenance Standards). A rake can be or geotechnical engineer (Dept. of Ecology: Volume narrow hole. used to remove the algae, which can be left to dry V, February 2005). on the pond slope in the summer season.

BMPs for Components of a Stormwater Pond

Remove vegetation and debris that Fix the cause of any erosion or Inlets and outlets impede water flow scouring

Look for sediment below outlet; if

found, note and correct Remove vegetation and debris that Photo: mulsanne @ flickr.com Debris barrier Photo: WA Dept. of Ecology impede water flow Use a rake to remove an algal mat from a Add rock to energy dissipater if If there is an oil sheen, the oil should be removed Energy dissipater stagnant pond. only one layer or holes immediately.

Check integrity of rock blankets Remove trees, shrubs, and vegeta- Spillway Replace rock as necessary tion over 4” If piping or erosion visible in berm, consult a civil or geotechnical engineer

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Stormwater pond components Pond cell

(continued) Inspection Frequency: Monthly

BMPs for Components of a Stormwater Pond

Remove vegetation and debris that Fix the cause of any erosion or Inlets and outlets impede water flow scouring

Look for sediment below outlet; if found, note and correct Remove vegetation and debris that Photo: mulsanne @ flickr.com Debris barrier Photo: WA Dept. of Ecology impede water flow Use a rake to remove an algal mat from a Add rock to energy dissipater if If there is an oil sheen, the oil should be removed Energy dissipater stagnant pond. only one layer or holes immediately.

Check integrity of rock blankets Remove trees, shrubs, and vegeta- Spillway Replace rock as necessary tion over 4” If piping or erosion visible in berm, consult a civil or geotechnical engineer

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Maintaining Your System Maintaining Your System

Pond structure

Inspection Frequency: Walls & side slopes: BMPs for the Pond Structure Quarterly, Bottom: Annually, Sediment removal: Annually in a two-stage system, or as needed Check for slumping or sloughing; if Check for and fix the cause of any Pond walls over 4” of slump, consult with an erosion or scouring Pond walls & side slopes engineer

Walk the perimeter of your pond quarterly. Look for Pond bottom (during dry If liner is visible, check for holes; anything out-of-the-ordinary including erosion, animal season) repair or replace burrows and settling. If you see animal burrows, take immediate action—hire a professional who can remove rodents without impacting water quality. If any Check sediment depth, especially Photo: RE Sources part of the pond has settled more than 4 inches it can near inlet; have removed if neces- Settlement and sloughing of a pond side slope be an indication of more severe problems with the sary berm or outlet (Dept. of Ecology: Volume V, February 2005). A licensed geotechnical engineer should be Additionally, if accumulated sediment is higher than Clean any oil sheen from water consulted to determine the cause of the settlement. the bottom of the outlet pipe, sediment must be re- Pond surface with oil absorbent pads or vactor moved to ensure that it does not contaminate down- truck Bottom of the pond stream water bodies. During the dry season, inspect the bottom of the pond for sediment buildup and liner integrity, if applicable. If Some newer ponds may have a two-stage pond system. In these types of ponds, sediment should be re- you have a liner (check your O&M manual) it should not be visible or have holes in it. If it is visible you may moved from the first cell (basin) on a regular basis. want to ask a stormwater professional if there is an This will prolong the life of the main pond, and if this is operational reason for this. If the liner has holes, it will done with regularity, the rest of the pond may never need to be repaired or replaced. need to be excavated. When your stormwater pond requires cleaning, con- Although some ponds may never need to have sedi- tact a professional cleaning service. Make sure the ment removed, most will. To determine whether it’s time to remove sediment, check to see how deep the professional follows the recommendations for management of street wastes from Appendix IV-G of the sediment is and the condition of the bottom of the Photo: WA Dept. of Ecology Photo: RE Sources pond. Has sediment built up near the inlet? Is the Washington State Department of Ecology’s 2005 bottom of the pond flat? Is the entire bottom of the Stormwater Management Manual for Western Wash- pond vegetated? Some ponds will have grass on the ington. You should request that the cleaning profes- Settling, sloughing, and erosion can be signs of serious bottom, and some won’t. sional you hire state that sediments removed from Dry pond bottom, with fencing, walls, inlet and your pond will be properly handled in your contract. problems that lead to failure of the pond wall control structure visible Sediment accumulation in the pond bottom that exceeds the depth of the designed sediment zone (usually 1’ or 10% of pond's capacity) should be removed (City of Portland: Operation and Maintenance for Private Property Owners and Dept of Ecology: Volume V, February 2005). Sediment markers placed in the facility can help you identify sediment depths.

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Pond structure

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Maintaining Your System Maintaining Your System

important action that will improve performance and Photo: RE Sources appearance of your facility. Not entirely grown in, but in need of vegetation management In order to identify vegetation maintenance needs, it is helpful to have a copy of your as-built drawing or

a landscape plan (which is often part of the O & M Photo: RE Sources stormwater pond, you will need to remove them by plan). When your pond was installed, specific kinds Good vegetation management makes potential mowing the pond bottom several times during the dry of plants were planted to function in certain areas. problems visible, and other maintenance easier season. If you can’t mow them, the seedlings will The plants in most stormwater facilities are a mix- need to be removed using another method (brush ture of native and non-native plants. Some of these frastructure. Trees and shrubs with extensive root cutting or hand-pulling). plants are adapted to live in saturated soils, and systems can destabilize side slopes and cause

some are adapted to live in upland soils. Photo: RE Sources seepage through pond walls. If tree shade causes Vegetation on the sides of your pond bare areas and erosion, consider removing the tree. A couple of carefully placed native trees or shrubs A pond that is 100% cattails will need management Native and non-native grasses are the most com- are okay if they are in the right places (away from mon vegetation used in stormwater pond construc- the flow paths, and inlet/outlet structures). tion. The root system of grasses holds the surface soil in place and protects slopes from wind and ero- Vegetation on the bottom of your pond A proliferation of cattails usually indicates that the sion. The right kind of vegetation on the pond side- In the fall, winter, and spring, your pond will proba- pond has too much sediment, since cattails cannot walls will protect the integrity of the pond. bly contain lots of water. You may or may not be grow in deep water. When your pond is filled with cattails, it is time to remove sediment. Grass should be mowed during the dry season to able to see the bottom of the pond to determine keep it 4” to 9” tall (City of Portland: Operation and what kind of plants are growing there. Check vege- Cattails are also a problem because they can domi- Maintenance for Private Property Owners). Grass tation on the bottom of the pond during the dry sea- nate shallow stormwater ponds, wetlands, and that is at least 4” tall captures more pollutants and is son. Bare areas on the pond bottom are okay; bare swales. Cattails out-compete other native emergent hardier. Grass that is over 10” tall is considered a areas on the sidewalls of the pond are not okay plants that otherwise establish more varied, mature nuisance because it hides potential problems such unless the pond has just been built. plant ecology. as volunteer tree seedlings and rodents. Grass clip- In the wet season, if your pond has no vegetation pings should always be removed from the pond If your pond is near a wooded area that contains al-

sticking up above the water (emergent vegetation), Photo: RE Sources area. If areas of the pond walls are bare, re-seed in ders or cottonwood trees, it may receive thousands the pond bottom does not require any vegetation the spring or summer (as soon as is possible). of tree seeds in the spring. Sometimes these seeds A pond entirely grown in with trees and other management. will sprout. Depending on the species of tree and the vegetation Trees are often planted for aesthetic, stabilization, If your pond has 25 to 50% emergent vegetation amount of time the pond bottom is inundated with and temperature control reasons. They have to be during the wet season, it may need to have sedi- water, the seeds will thrive. If seedlings cover your managed to prevent clogging of pipes and other in-

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Maintaining Your System Maintaining Your System

Vegetation in and around the pond ment removed. This is especially true if the emergent vegetation is in the middle (deepest part) of the pond. Inspection Frequency: Annually If no more sediment is being added to the pond through the conveyance systems (like from nearby Plants are an important water quality part of storm- development projects), vegetation management may water facilities—they do all of the actual work! not be needed. Plants absorb water and nutrients, and their roots When the pond is 50 to 100% covered with emergent improve the infiltration rates of soil while stabilizing vegetation during the wet season, it probably re- slopes and preventing erosion. Plants capture pollu- quires vegetation management. tion, provide habitat for birds and wildlife, and add aesthetic appeal to property. Proper maintenance of plants at your stormwater facility is the single most important action that will improve performance and Photo: RE Sources appearance of your facility. Not entirely grown in, but in need of vegetation management In order to identify vegetation maintenance needs, it is helpful to have a copy of your as-built drawing or a landscape plan (which is often part of the O & M Photo: RE Sources stormwater pond, you will need to remove them by plan). When your pond was installed, specific kinds Good vegetation management makes potential mowing the pond bottom several times during the dry of plants were planted to function in certain areas. problems visible, and other maintenance easier season. If you can’t mow them, the seedlings will The plants in most stormwater facilities are a mix- need to be removed using another method (brush ture of native and non-native plants. Some of these frastructure. Trees and shrubs with extensive root cutting or hand-pulling). plants are adapted to live in saturated soils, and systems can destabilize side slopes and cause

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Maintaining Your System Maintaining Your System

Vegetation in and around the pond (continued)

Inspection Frequency: Annually; Semi-annually during BMPs for Vegetation Management growing season for nuisance vegetation

Pond walls Mow grass 4-9” and remove clippings Reseed any bare areas Vegetation near the inlet, outlet, control structures, fences, and access ramps Check for emergent vegetation over It is very important to regularly check the vegetation Remove tree seedlings Pond surface and bottom more than half the area; if present, around inlets, outlets, controls structures, fences, and sediment removal will be necessary Remove algae if over 10% of surface ramps. Trees and shrubs should be cleared from these structures because they can block your view of the facil- Remove trees and shrubs that may ity, making inspections difficult, and their roots may shade and kill grass on sidewalls or Remove invasive and poisonous damage pond structures. Maintained grass is the only Around pond that might have problem roots near plants vegetation that should be allowed around these fea- tures. You don’t want to have vegetation blocking the pipes and structures access ramp in the event that you need to remove sediment or an outlet blockage during winter months! Photo: RE Sources Vegetation should be cleared from around this inlet

Nuisance vegetation High or low water levels

In the dry season, inspect the pond, sidewalls, and access areas for any poisonous plants or invasive weeds A common maintenance issue for stormwater ponds ures, resulting in downstream property and habitat such as purple loosestrife, knotweed, tansy ragwort, is abnormally high or low water levels. Most storm- damage. Himalayan blackberry, English ivy, Canada thistle, bull water ponds are designed to hold water at a stable Low water levels can be caused by leaks in the pond thistle, yellow flag iris, and reed canary grass, before it level, which will rise during and after a storm event. If walls or berms, in the spillway, or in the pond bottom. goes to seed. Invasive weeds are a problem because the pond is draining correctly, the water level will Leaks can be serious because they can lead to ero- they have the ability to out-compete the more desirable fluctuate, but should not stay high or low for long sion and major failures during storm events. To as- vegetation (grass). They spread quickly and often grow time periods. sess whether there are leaks and/or to correct them, taller than grass, making maintenance difficult. If the water level remains higher than average after a you should contact a stormwater professional. Whatcom County has an excellent web site to help you storm event, it is likely that the low orifice in the outlet Photo: RE Sources identify invasive species on your property: control structure is clogged or trash has blocked a Trim invasives like English Ivy off of fences and weir, trash rack, or other entrance to the control http://www.co.whatcom.wa.us/publicworks/weeds/weedlist.jsp structures structure. This is an undesirable situation, as the water storage volume in the pond is less, reducing the ability of the pond to attenuate flood flows. High wa- Proper maintenance of plants at your stormwater facility ter levels can lead to dike, berm, or pond wall fail- is the single most important action that will improve performance and appearance of your facility.

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Maintaining Your System Maintaining Your System

Vegetation in and around the pond (continued)

Inspection Frequency: Annually; Semi-annually during BMPs for Vegetation Management growing season for nuisance vegetation

Nuisance vegetation High or low water levels

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Maintaining Your System Costs

Access and safety The expenses associated with stormwater facility mended for both capital maintenance procedures maintenance depend on the size, design, and type of (e.g., sediment removal and major replanting costs) Inspection Frequency: Quarterly facility. Most of the short-term maintenance (mowing, and routine activities such as facility inspections, de- removing invasive plants, checking for trash, small bris removal, and vegetation management. For Stormwater ponds can be safety hazards to small erosion repairs, re-seeding, removing trees in un- homeowner associations, this could be a portion of children, especially if they play in or around the wanted areas) can be performed by neighborhood homeowner fees, or a specific assessment. ponds. Some ponds have very steep walls, in- residents or a landscaping company. It is a good idea to save an average of 5 to 10% per creasing the likelihood of falls. In most cases, it is Costs for mowing and weed control are usually cal- year of the facility's capital cost for annual routine wise to restrict access to ponds by installing and culated on a per-acre basis. You should expect these maintenance. A percentage of this amount should be maintaining fences and gates. Check the integrity costs to increase between three to five percent each saved for sediment removal. For example, if it is esti- of all fences, gates, and locks. Repair any fence

Photo: RE Sources year. When you have a grasp on the costs associ- mated that the facility will need sediment removal sections that are damaged. Make sure that gates ated with upkeep, you can establish a monthly or every five years, 20% of the cost should be put aside open and close freely. Lubricate locks when A well maintained rock access ramp with gate yearly dues payment to assess to each homeowner. each year. An additional 3 to 5% of the facility's capi- needed. and fence ensuring neighborhood safety tal cost per year should be put aside for eventual fa- Long-term maintenance costs typically involve re- cility replacement. Most of these facilities have a life Access road/ramps ping, dam and lodge removal, and other tech- placing structural components and removing sedi- expectancy of 25 to 50 years, although they could niques. Access ramps are rock-lined access routes (roads) ment from the facility. It is best to hire a team of pro- last much longer (City of Portland: Operation and fessionals to perform these tasks. Tasks that will that allow access for heavy machinery. These are Beavers and other rodents can be trapped using a Maintenance for Private Property Owners). likely require the services of a professional include constructed of asphalt, concrete, rock, or other ap- live trap, but the cost is often prohibitive. Lethal replacement of outlets, embankments, and removal Most routine maintenance is estimated to have an proved material. control may become necessary to control beaver of sediment. If a severe flood damages your facility, annual cost of $200 to $600 dollars per acre of facil- damage. If you need to have a beaver trapped, call Look for the rock access ramp near the fence gate. get assistance. ity (Pierce County Stormwater Maintenance Manual). your local Washington Department of Fish and It should have a covering of rock, allowing access These costs will vary depending on the types and Wildlife Office at (425) 775-1311 for information. for heavy equipment in case sediment needs to be If you don't already collect funds for maintaining your level of maintenance practices desired. If you have a facility, you will need to figure out how to finance your removed from the pond. No trees, shrubs, or per- Large numbers of ducks and geese are undesir- brand new facility, cost and intensity of maintenance ennial vegetation should be allowed to grow on the able in a stormwater pond because of increased maintenance needs. A maintenance fund is recom- activities may be higher during the first several years, ramp. If any of the rocks have been displaced, re- fecal coliform bacteria counts and nutrient loading. as vegetation becomes established. place them. Large numbers of waterfowl can also eat desirable Most important, educate the people who live in your grasses and plants. Small numbers of waterfowl Wildlife and insects community about the benefits and purpose of your are typically not a concern. Do not feed birds at- stormwater facility. Rodents usually damage ponds by burrowing or tracted to stormwater ponds. dam building. Burrowing may jeopardize embank- Mosquito populations sometime use stormwater ment stability for dams and berms. If you have a lot ponds as breeding habitat. Sometimes the public of tall vegetation at your facility, you may be attract- becomes very concerned that the source of local ing wildlife. mosquitoes is a nearby pond or wetland. Often, the Moles, muskrats, pocket gophers, nutria, rats, and problem may come from a combination of breeding beavers routinely cause destruction to embank- habitats. The proliferation of mosquitoes is typically ments and berms. Beaver dams reduce water stor- an indication of a maintenance problem, as mos- age in the pond and can lead to severe drainage quitoes usually lay eggs in still pools of water or on problems. The food source of many of these ro- mud or fallen leaves. Proper maintenance of your dents is aquatic plants—so they may be attracted pond should reduce mosquito presence. If insects to your stormwater facility if it has a healthy plant such as wasps and hornets are found, they should community. Management of rodents and beavers be destroyed or removed from the site. These will Photo: stevehdc/Steve @ flickr include maintaining a fence, removing trees, trap- interfere with regular maintenance activities. Beavers create their own detention ponds

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Maintaining Your System Costs

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References and Resources Glossary

Whatcom County Government Beaver deceiver: A constructed flow control device Channel: A long, narrow excavation or surface fea-

Whatcom County Public Works Stormwater Division that reduces beaver damming activities. It is a non- ture that conveys surface water and is open to the air. http://www.whatcomcounty.us/publicworks/water/index.jsp lethal beaver management technique. Same as a ditch.

Noxious and Invasive Weeds of Whatcom County Berm: A constructed barrier of compacted earth, Check dams: Small rock dams built across a ditch to http://www.co.whatcom.wa.us/publicworks/weeds/weedlist.jsp rock, or gravel. In a stormwater facility, a berm may slow water and allow for settling. serve as a vertical divider typically built up from the Whatcom County Development Standards Chapter 2 – Stormwater Management (2002) bottom. Conveyance system: Drainage facilities and fea- http://www.co.whatcom.wa.us/publicworks/engineering/documents/ch2stormwater.pdf tures that collect, contain, and provide for the flow of Bioretention: An integrated stormwater management surface and storm water from the highest points on Whatcom County Department of Health practice that uses plants, microbes, and soils to re- the land down to a receiving water. http://www.co.whatcom.wa.us/health/index.jsp move and retain pollutants from stormwater. Culvert: Pipe or concrete box structure which drains Bioswale: A long, gently sloped, vegetated ditch de- open channels, swales, or ditches under a roadway or Finding Stormwater System Contractors signed to filter pollutants from stormwater. Grass is embankment typically with no catch basins or man- Find stormwater systems maintenance contractors by searching local business listings or the internet. the most common vegetation, but wetland vegetation holes along its length. Search under: Erosion Control, Sewer Contractors, Storm Drain Cleaning, and Stormwater Management. can be used if the soil is saturated. CWA: Clean Water Act. The federal environmental BMP: Best Management Practice. Activities or prac- law that includes the management of stormwater. References & Resources Outside Whatcom County tices that prevent or reduce the release of pollutants into receiving waters. Debris barrier: A metal trash rack. Citizen’s Guide to Maintaining Stormwater US EPA National Pollutant Discharge Elimination http://www.co.pitt.nc.us/depts/planning/enviro/ System (NPDES) National Menu of Stormwater BMPs Buffer: A designated area adjacent to and a part of a Detention: Release of surface and storm water run- documents/citizenguide.pdf http://cfpub.epa.gov/npdes/stormwater/menuofbmps/ steep slope or landslide hazard area which protects off from the site at a slower rate than it is collected by index.cfm slope stability, attenuation of surface water flows, and the stormwater facility, the difference being held in Maintaining Catch Basins in Thurston County, WA landslide hazards reasonably necessary to minimize temporary storage. http://www.co.thurston.wa.us/wwm/Publications/ US EPA Stormwater Wet Pond and Wetland risk; or a designated area adjacent to or a part of a Detention facility: A facility that collects water from Water/Catchbasins_Drywells2.pdf Management Guidebook stream or wetland that is an integral part of the stream developed areas and releases it at a slower rate than http://www.epa.gov/npdes/pubs/pondmgmtguide.pdf or wetland ecosystem. Pierce County Stormwater Maintenance Manual for it enters the collection system. The excess of inflow Private Facilities: http://www.co.pierce.wa.us/pc/ Puget Sound Partnership LID manual: http:// Catch Basin, Type 1: An underground concrete wa- over outflow is temporarily stored in a pond or a vault services/home/environ/water/wq/prifacmanual.htm www.psp.wa.gov/downloads/LID/LID_manual2005.pdf ter receiving inlet, rectangular in shape and is typically released over a few hours or a few days. Puget Sound Partnership Resource Center Puget Sound Partnership LID website: http:// (approximately 3' x 2' x 4' deep) with a slotted iron grate on top to inlet water or a solid rectangular cover. http://www.psparchives.com/our_work/stormwater/ www.psparchives.com/our_work/stormwater/lid.htm Detention pond: A type of stormwater detention fa- Water may also enter/exit through culverts visible in stormwater_resources.htm cility. Protecting waterways starts in your own yard: the side walls of basin. Also referred to as Inlet. Stormwater Management Facilities – Operation and http://www.metrocouncil.org/directions/water/ Discharge: Runoff, excluding offsite flows, leaving A round concrete underground Maintenance for Private Property Owners, City of water2007/yardcare.htm Catch Basin, Type 2: the proposed development through overland flow, basin (4'-8' diameter; 6' or greater deep); may contain Portland, Oregon: http://www.portlandonline.com/bes/ built conveyance systems, or infiltration facilities. index.cfm?c=45464 Bioswale brochure: http://buildgreen.ufl.edu/ Flow Restrictor/Oil Pollution control device. These ba- Fact_sheet_Bioswales_Vegetated_Swales.pdf sins are also required when larger diameter culverts Ditch: A constructed channel with its top width less Washington State Department of Ecology website are used. Also referred to as a Manhole or Control than 10 feet at design flow. http://www.ecy.wa.gov/programs/wq/stormwater/ Biofilters: A manual by Oregon Dept of Environ- Manhole. index.html mental Quality: http://www.deq.state.or.us/wq/ Drainage: The collection, conveyance, containment, stormwater/docs/nwr/biofilters.pdf Catch basin insert: A device installed underneath a and/or discharge of surface and storm water runoff. 2005 Washington State Department of Ecology catch basin inlet to treat stormwater through filtration, Stormwater Management Manual for Western Wash- The Integrated Pond: Enhancing the design and settling, absorption, adsorption, or a combination of Drainage area or drainage basin: An area draining ington – Volume V – Runoff Treatment BMPs value of stormwater ponds: these mechanisms. There are a number of shapes, to a point of interest. http://www.ecy.wa.gov/biblio/0510033.html http://your.kingcounty.gov/dnrp/library/1998/kcr745/ sizes, and configurations of inserts available. intro.pdf Drainage facility: A constructed or engineered fea-

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References and Resources Glossary

Whatcom County Government Beaver deceiver: A constructed flow control device Channel: A long, narrow excavation or surface fea-

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Glossary (continued) Glossary (continued) ture that collects, conveys, stores or treats surface mantle as under natural conditions prior to develop- Rain garden: A planted depression that allows rain- streams, or ditches used to carry surface and storm and storm water runoff. Drainage facilities include but ment; and/or a hard surface area which causes water water from impervious surfaces to be absorbed. water from surrounding lands to streams, lakes, or are not limited to all constructed or engineered to run off the surface in greater quantities or at an in- Puget Sound. : Bodies of water or surface water streams, pipelines, channels, ditches, gutters, lakes, creased rate of flow from the flow present under natu- Receiving waters systems receiving water from upstream man-made or : Vegetation that grows un- wetlands, closed depressions, flow control or water ral conditions prior to development. Common impervi- Submerged vegetation natural systems. derwater, and does not emerge above the water level. quality treatment facilities, erosion and sedimentation ous surfaces include, but are not limited to, roof tops, control facilities, and other drainage structures and walkways, patios, driveways, parking lots or storage Recharge: The flow to groundwater from the infiltra- Structural BMP: Constructed facilities or measures appurtenances that provide for drainage. areas, concrete or asphalt paving, gravel roads, tion of surface and stormwater runoff. to help protect receiving water quality and control packed earthen materials, and oiled, macadam, or stormwater quantity. Examples include storage, vege- Dry season: May 1 to September 30. other surfaces. Retention: The process of collecting and holding sur- tation, infiltration, and filtration. face and storm water runoff with no surface outflow. Embankment: A structure of earth, gravel, or similar Impoundment: A natural or man-made containment : A rectangular underground inlet material raised to form a pond bank or foundation for Type 1 catch basin for surface water. Runoff: Water originating from rainfall and other pre- to the stormwater piping system, with a slotted iron a road. cipitation that ultimately flows into drainage facilities, grate on top. See catch basin, type 1. Low-impact Development (LID): Stormwater man- rivers, streams, springs, seeps, ponds, lakes, and Emergent vegetation: Vegetation in a stormwater agement methods that encourage water to infiltrate wetlands as well as shallow groundwater. : A round concrete underground pond or wetland that emerges above the water level. Type 2 catch basin into the ground, rather than being conveyed away. basin, 4’-8’ in diameter, 6’ deep or deeper. See catch Scour: Stream bank or ditch side erosion caused by EPA: Environmental Protection Agency. basin, type 2. Nonpoint source (NPS) pollution: NPS pollution high-velocity water. Energy dissipater: A rock pad constructed at inlets/ occurs when rainfall, snowmelt, or irrigation runs over Undercutting: When the top edge of a stream bank outlets to prevent erosion, or a constructed percola- land or through the ground, picks up pollutants, and Sewer system: The system of pipes and pump sta- or ditch side extends further out than the underlying tion trench to disperse discharge flows over a large deposits them into rivers, lakes, and coastal waters or tions that collect and transport wastewater from bank. area, or a catch basin used to slow fast flowing runoff. introduces them into ground water. homes and businesses to a wastewater treatment : A truck with a special tank and vacuum Catch basins may be a part of the dispersion trench. plant. Vactor truck Natural onsite drainage feature: A natural swale, attachment designed to remove sediment from storm- Where a landform settles or slides, usually Erosion: The detachment and transport of soil or channel, stream, closed depression, wetland, or lake. Slumping: water facilities like catch basins or pipes. rock fragments by water, wind, ice, etc. due to saturated soil. Nutrients: Nitrogen and phosphorus are considered Weir: A small dam in a river, stream or drainage Flow control facility: A drainage facility designed to nutrients in stormwater runoff and can accumulate in Stormwater: Water that runs off surfaces such as channel. mitigate the impacts of increased surface and storm stormwater ponds, leading to degraded conditions rooftops, paved streets, highways, and parking lots. It : A drainage facility water runoff generated by site development. such as low dissolved oxygen levels, algae blooms, can also come from hard grassy surfaces like lawns, Water quality treatment facility unsightly conditions, and odors. play fields, and from graveled roads and parking lots. designed to reduce pollutants once they are already Flow restrictor: A control device or a T section with contained in surface and storm water runoff. Water one or more orifices to control release rates. Outfall: A point where collected and concentrated Stormwater facilities: Facilities that control the dis- quality treatment facilities are the structural compo- surface and storm water runoff is discharged from a charge of stormwater and/or remove pollutants. nent of best management practices (BMPs); when French drain: A trench in the ground that collects wa- pipe system or culvert. These are most often built in conjunction with new used singly or in combination, WQ facilities reduce ter, and promotes infiltration into the ground. development but include regional systems. the potential for contamination of surface and/or Piping: An engineering term used for water that ground waters. Groundwater: Underground water usually found in moves through a channel or narrow hole. Stormwater system, residential: Residential storm- aquifers. Groundwater usually originates from infiltra- water systems typically serve all or part of a single Wet season: October 1 to April 30. Point discharge: The release of collected and/or tion. Wells tap the groundwater for water supply uses. development and are built on a tract dedicated to this concentrated surface and storm water runoff from a purpose. Wetland: An area inundated or saturated by ground Ground truthing: Ground truth refers to information pipe, culvert, or channel. or surface water at a frequency and duration sufficient that is collected "on location." Stormwater management: The application of site to support, and that under normal circumstances does Point source pollutant: Pollution issuing from a sin- design principles and construction techniques to pre- support, a prevalence of vegetation typically adapted Habitat: The specific area or environment in which a gle point (e.g., a pipe) discharge. vent sediments and other pollutants from entering sur- particular type of plant or animal lives and grows. for life in saturated soil conditions. Wetlands generally Rain barrel: A barrel installed to capture water from a face or ground water; source controls; and treatment include swamps, marshes, bogs, and similar areas. Impervious surface: A hard surface area which ei- roof. of runoff to reduce pollution. ther prevents or retards the entry of water into the soil Storm drain system: The system of gutters, pipes, -- 32 -- - 33 --

Stormwater System Inspection Checklist INSPECTOR’S NAME & DATE:

Inspection Schedule & Checklist NAME & ADDRESS OF FACILITY:

GENERAL OBSERVATIONS (IS WATER FLOWING?):

WEATHER:

Typical Inspection / Maintenance Schedule for Stormwater Pond Facilities Checked? Maintenance Maintenance Completed/ (Y/N) Needed? Observations & Remarks (Y/N) Activity Schedule/Frequency Type 1 catch basins Inspect pond area for oil sheens or trash Monthly Look for debris and sediment blocking catch basin grate. If found, remove. Inspect exterior of catch basins Monthly and after storm Inspect filter. Change if torn; clean if clogged; monitor for blockages. Inspect pond area, sidewalls, and shoreline for erosion, settlement, ro- Quarterly Look for sediment and trash in catch basin dent damage, and insects sump. Clean out if sediment fills 60% of the sump or comes within 6” of a pipe. Inspect fences, gates and locks Quarterly Look for damage or cracks to frame, grate, basin walls or bottom. If found, repair or Inspect bioswales for vegetation cover and bare areas Quarterly replace. Type 2 catch basins Inspect ditches, check dams, and all visible pipes and culverts for trash, Quarterly and after storm obstructions and other problems events Remove trash blocking grates or inlets; replace if broken. Quarterly and after storm Inspect inlets and outlets for trash, obstructions, and vegetation Remove lid and check for sediment accu- events mulation. Remove trash. Remove sediment if more than 1/3 full. Quarterly and after storm Inspect trash racks, debris barriers, and energy dissipaters Check integrity of ladder rungs, cleanout events gate, and orifice plate. If bent or ob- structed, take appropriate action. Inspect water levels in the pond After storm events Have cracks in wall or bottom repaired as necessary. Inspect pond area for undesirable or poisonous vegetation and noxious Semi-annually, during Conveyances (ditches, bioswales, culverts, and pipes) weeds growing season Check for undercutting, scouring, and Pond area sediment accumulation (pond bottom) Annually slumping. If found, repair or maintain. Remove all trash and loose sediment. Re- Inspect interior of catch basins for debris and sediment Annually move sediment if it will impede water flow or clog downstream structures. Inspect spillway for vegetation overgrowth and ease of heavy equipment Annually Maintain vegetation; mow or cut back if access impedes water movement or grass health. Repair check dams as necessary. Inspect inside type 2 catch basins, including flow restrictor/orifice plate Annually Remove any dumped yard waste. Inspect access ramps for ease of heavy equipment access Annually In ditches and swales, check for integrity of grass, check dams, inlets, and outlets. Remove shrubs and trees.

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Stormwater System Inspection Checklist INSPECTOR’S NAME & DATE:

Inspection Schedule & Checklist NAME & ADDRESS OF FACILITY:

GENERAL OBSERVATIONS (IS WATER FLOWING?):

WEATHER:

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Checked? Maintenance Maintenance Completed/ (Y/N) Needed? (Y/N) Observations & Remarks Components of the pond Inlets and outlets: remove vegetation and debris. Fix erosion and scouring. Fix cause of sediment found below outlet. Remove vegetation and debris from trash rack. Add rock to energy dissipater if missing. If necessary, repair rock on spillway. Remove trees, shrubs, and vegetation over 4”. If piping or erosion is visible, consult engineer. Pond Check for slumping or sloughing of walls. If over 4” of slumping, consult with an engineer. Fix any erosion or scouring. If leaks, piping, or soft spots are found, consult with an engineer. If liner visible on bottom, check for holes or replace. Clean any oil sheen from water with oil-absorbent pads or vactor truck. Check sediment depth near inlet. If more than one foot exists, or there is build up near inlet, the pond needs to be cleaned. Vegetation On the pond walls/side slopes, mow grass to 4 – 9”. Remove clippings. Reseed bare areas. On pond surface, emergent vegetation over 50% of the area indicates sediment removal needed. On pond bottom, remove tree seedlings. Around the pond, remove trees and shrubs that shade sidewall grass or that might have problem roots near pipes and structures. Remove invasive and poisonous plants. Remove algae if over 10% of surface. Access and Safety Check integrity of access ramp; ensure stable and clear for heavy equipment. Check integrity and operation of all fences, gates, and locks. Repair as needed for ease of access. Remove rodents and insects if evidence found.

Remove vegetation on fences. Photo: Whatcom County

Attach pictures, summary, sketches, and notes as appropriate.

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Remove vegetation on fences. Photo: Whatcom County

Attach pictures, summary, sketches, and notes as appropriate.

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For questions about stormwater systems, contact: Whatcom County Public Works Stormwater Division 322 N. Commercial Street, Ste. 301 Bellingham, Washington, 98225 Telephone: (360) 715-7450 Email: [email protected] Web: http://www.whatcomcounty.us/publicworks/water/index.jsp

This project has been funded in part by the Washington State Department of Ecology (DOE) under assistance agreement WS-96073401 to Whatcom County. The contents of this document do not necessarily reflect the views and policies of the Washington State DOE, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

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