The Maintenance of Residential Stormwater … Maintenance of Residential Stormwater Management Areas 1 ... Trash rack Low flow channel ... The Maintenance of Residential Stormwater

Untied StatesDepartment ofAgricultural

NaturalResourcesConservationService

The Maintenance ofResidential StormwaterManagement Areas

Source of sketch: Montgomery County, Pennsylvania, October,

January 2000

The Maintenance of Residential Stormwater Management Areas I

A Product of the Mid-Atlantic Interdisciplinary Resource Team

Acknowledgements

Carl DuPoldt, USDA, NRCS, East Reg. Urban Cons. IRT, Hammonton, NJJulie Hawkins, USDA, NRCS, Mid-Atlantic IRT, Dover, DEMarianne Hardesty, USDA, NRCS, Newark, DEPete Marole, New Castle County Department of Special Services, DECathy Martin, Fisheries Biologist, Delaware Department of Natural Resourcesand Environmental Control, Division of Fish and WildlifeRichard Mickowski, New Castle Conservation District, Newark, DEDebi Weiker, New Castle Conservation District, Newark, DE

The United States Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, nationalorigin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to allprograms.) Persons with disabilities who require alternate means for communication of program information (Braille, large print, audiotape, etc.)should contact the USDA’s TARGET Center at (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326W, Whitten Building, 14th and Independence Avenue, SW,Washington, DC 20250-9410, or call (202) 720-5964 (voice or TDD). USDA is an equal opportunity employer.

Issued January 2000

II The Maintenance of Residential Stormwater Management Areas


The Maintenance of Residential Stormwater Management Areas 1


Mid-AtlanticInterdisciplinaryResource Team

The Maintenance ofResidential StormwaterManagement Areas

Introduction and Background

Prior to the implementation of stormwatercontrols, construction and development oftenresult in severe alterations in watershed drain-age patterns. These alterations have oftenresulted in downstream flooding on residentialand commercial properties, as well as low-lyingroad crossings. Uncontrolled stormwater volumeincreases streambank erosion and results inmajor detrimental changes in the physicalcharacteristics of receiving streams. Residentialand commercial land uses result in pollutedstormwater runoff, which can reach waterbodies unless control mechanisms are in place.This polluted runoff is also referred to asnonpoint source pollution. Federal, state, andlocal laws and regulations require stormwatermanagement and the control of nonpoint sourcepollution.

Homeowner’s associations and facility managerscan perform simple and routine maintenance,while more detailed complex maintenance andrepair would require contracting with knowl-edgeable consultants. The goals of an effectivemaintenance program should be to prolong theservice life of the stormwater facilities, minimizeexpensive repair costs and preclude adversedownstream impacts.

This guidance document has been prepared forhomeowner’s associations and residential andcommercial property managers to help themunderstand the basic maintenance needs forstormwater management areas.

Brief Description of Wet and Dry Ponds

Two of the most common types of best manage-ment practices that address stormwater manage-ment are dry ponds and wet ponds.

A dry pond is a permanent stormwater manage-ment facility that temporarily stores incomingstormwater. The pond typically is dry betweenstorm events. Dry ponds should incorporateextended detention of runoff from small rainfallevents. The primary purpose of dry ponds is toreduce and delay stormwater runoff peaks. Thebenefits are reduced potential for flooding anderosion in downstream areas. (See fig. 1.)

A wet pond is a stormwater management facility,which includes:• a permanent pool of water for enhancing water

quality and• additional capacity above the permanent pool

for detaining stormwater runoff.

Wet ponds fill with stormwater and release mostof it over a period of a few days. (See fig. 2.)

Maintenance Types

Routine and non-routine maintenance items areshown in the table 1. Routine maintenance in-cludes items that associations and property man-agers should perform. Non-routine maintenanceitems are those that associations and propertymanagers should have an awareness, but shouldbe handled by a professional with expertise in thisfield.

Homeowner’s associations should retain a copy ofthe design drawings and planting schemes for thestormwater management facilities. It should benoted that structural areas should be checked atleast annually and after major storm events.


2 The Maintenance of Residential Stormwater Management Areas

Top of berm

Vegetativebufferstrip

Shallowmarsh

Inflowenergy

dissipator

Riprapbaffle

Water quality storage

Trash rack

Low flow channel(optional)

Emergencyspillway

Concrete box outletstructure alternative

Trash rackEmbankment

Outlet energydissipator

Forebay

1 ft Peak attenuation storage

8 to 18-inch deepshallow marsh

(optional) Riprapbaffle

Low flow channel invert(optional)


Source of sketch:Pennsylvania handbook of best management practices for developing areas, spring, 1998.

Figure 1 Dry Pond - Plan and Elevation



1 ft

1 ft

3 to 6 ft

Peak attenuation storage


Permanentpool Outlet

Gabion earthbaffle

(optional)Aquaticbench

Terrestrialbench

Forebay

Maximum pool

Embankment

Access roadaround basin

No treeson embankment

Outlet structurealternative

Outfall

Emergencyspillway

Maintenanceright-of-wayto sedimentforebay

Stabilized bottom preferred

Sedimentforebay

Energydissipator

Inlet

Vegetativebufferstrip

Side slopesmax 3:1

Gabion/earthbaffle (alternative)

Outlet structurealternative riserwith hood

Terrestrial bench and buffer at toe of slope

Aquatic bench

Figure 2 Wet Pond - Plan and Elevation



Visibility of the facility—Community needs andpreferences determine to a large extent the typeand amount of necessary maintenance for aes-thetic purposes.

Landscaping—Maintenance needs vary greatlydepending upon the type of vegetation.

Upstream conditions—Watershed conditionsabove the facility will largely determine the typeand amount of sediment and other pollutants thatare entering that facility.

Safety—Some tasks can be carried out by non-technical staff or residents quite effectively.However, all programs should carefully ensurethe safety of anyone carrying out maintenancetasks, and often a professional should be hired toconduct the work. Confined spaces should neverbe entered without proper training and permits

from occupational and safety regulatory agencies.Confined areas may accumulate toxic and flam-mable gases for humans.

Need for professional judgment—Professionaljudgment should be solicited regularly to ensurethat all needs of the facility are met. Even thoughsome maintenance tasks can be routinely per-formed by property owners, there are manyproblems that are not obvious to the untrainedeye. (See appendix 1.)

Carrying out the maintenance plan—In the execu-tion of a maintenance plan, safety, cost, andeffectiveness of the maintenance activities need tobe balanced. Some minor maintenance items canbe accomplished by the facility owners, such aslitter removal, light weeding, and light mowing.The best solution, however, is to contract with aprofessional to do the more extensive sediment

Table 1 Routine and non-routine maintenance items

Routine maintenance Non-routine maintenance

Visual inspection Bank stabilization

Debris/litter control Inlet and outlet structuremaintenance/replacement

Maintaining upstream undisturbed Mechanical components maintenanceareas to minimize invasive vegetation

Nutrient excesses and odors Structural repairs –embankments, inlets, outlets, pipereplacement/repair, removal of fallentrees (could be considered routine).

Minor bank stabilization and erosion Removal of excessive sedimentcontrol - sheet & rill

Minor sediment removal - shovel, rake, Rare condition (extremely low pH,pick, or wheelbarrow spills of oils and toxic materials,

swimming pool water draining.)

Vandalism & fence maintenance Major bank stabilization – gullies

Algae and aquatic vegetation Removal of excessive algae andaquatic vegetation

Mowing and harvesting of uplandvegetation



removal work. Mowing and handling of a wheel-barrow can be dangerous on the sloping embank-ments of a wet or dry pond. Filling eroded areasand soil disturbing activities, such as resodding orreplanting vegetation, are also items that a profes-sional landscaping firm might best manage. If it isnot done right the first time, excessive erosion willresult. In addition, trained personnel will be ableto identify potential problems early or when it ismost cost effective to correct. Most maintenanceneeds are site specific.

Financing—A fund should be established toprovide for the costs of long-term maintenanceneeds. These long-term needs might include:extensive sediment removal, structural repairs,landscaping, invasive plant management andcontrol, and litter removal.

Inspection checklists

Checklists to assist associations and propertymanagers during routine inspections similar to thefollowing are particularly helpful.

Debris and obstructions removal

Special attention should be given to the removal offloating debris (leaves, paper, trash, branches, andother manmade and natural materials), which canclog the outlet device or riser. The benefits ofdebris removal include:• Reducing the chance of clogging in the outlet

structures, trash racks, low flow channels, andother facility components

• Preventing possible damage to vegetated areas• Reducing potential mosquito breeding habitats• Improving facility appearance• Reducing conditions for excessive surface

algae

Erosion and sediment control

It is very important to ensure the integrity of thevisible banks, slopes, and bottom of ponds.Healthy ground cover must be routinely main-tained on all embankments of wet and dry pondsand on the bottoms of dry ponds. Bare areasshould be reseeded and stabilized as quickly aspossible depending on the season of the year. Inthe spring, summer, and fall, seed and stabilizewithin 20 days. In the winter, consider using

synthetic materials and then reseed and stabilizewith living vegetation during the growing season.Erosion will result in sediment clogging the facility.

The roots of woody vegetation, such as trees andshrubs, tend to destabilize the embankments.Consistent mowing of the embankment andemergency spillway will control any stray seed-lings that take root. Woody growth away from theembankment does not generally pose a threat tothe stability of the embankments and can play animportant role in maintaining a healthy pondecosystem. Trees and shrubs, however, should beplanted outside of maintenance and access areas.

Structural and mechanical equipment

Maintenance of these items is usually beyond thecapabilities of homeowner associations. If aproblem is observed, it is a good idea to have aprofessional to investigate and correct the prob-lem early before it becomes a major expense.Some of the structures and equipment that may beencountered include:• valves,• sluice gates,• fence gates,• locks,• access latches,• aeration equipment,• pumps, and• inlet and outlet structures.

Vegetation maintenance

To ensure grass vigor, maintain as an uplandmeadow. This includes cutting no shorter than 6 to8 inches high. If a more manicured lawn setting isdesired, more mowing and special attention to turfhealth will be needed. Some communities considerthe tall wetlands-type vegetation (typically, cattailsor rushes) that may grow in dry ponds as unaes-thetic. Some of this vegetation is actually benefi-cial as it provides water quality benefits andwildlife habitat. Some vegetative needs include:• pH adjustment (as required),• pruning,• pest control,• reseeding,• thatch removal, and• weed removal.



A Minimum Inspection Checklist for Stormwater Ponds

Item to check Dates observed and/or corrected Comments on what observed

(attach a sketch)

Obstructions of theinlet or outlet struc-tures by trash anddebris

Excessive erosion orsedimentation in thebasin

Inspect the embank-ment area to ensureintegrity (holes, trees,roots, weeps, seeps,slumping, and faults)

Depression or wetspots in the bottom ofa dry pond

Deterioration of pipes

Condition of theemergency spillway

Erosion of the em-bankments and sideslopes (erosion andgullies)

Upstream and down-stream channelconditions

Signs of vandalism

Other items

Observed Corrected



Sediment filtration—Vegetative cover outside ofthe embankment, filters sediment from runoff as itflows into the pond. It also prevents erosion of thebanks of the pond. A minimum 24 foot vegetatedbuffer strip is ideal around wet ponds. This bufferstrip should be mowed no more than four timesper year. Mowing requirements can be tailored tothe specific needs of a particular site and theadjacent neighbors.

Surrounding vegetation fertilization (not recom-

mended, except in special cases)—It is importantnot to over fertilize the surrounding vegetation.This could result in excess nutrients being washedinto the pond, which can contribute to excessivealga growth. As a general rule, the nutrient needsof the surrounding vegetation should be evaluatedby testing the pH and nutrient content of the soilprior to fertilization. The adjustment of pH may benecessary to maintain vegetation. Fertilization ofall turf areas should occur in the fall of the year.

Purple loosestrife—If your wetland and/orstormwater management area becomes invadedwith purple loosestrife, there are methods toreduce its presence. It is important to catch itspresence early, which is pretty evident by the longpurple flower head. To rid the wetland and/orstormwater management area of it manually, it isimportant to ensure that the rhizomes (largetuberous root systems) are removed as well as theplant prior to flowering (June through September).Plant parts, immediately upon removal, should beplaced in a bag to prevent further spread of thespecies. If it is not possible to do this, regularremoval of the flower heads before the seeds aredispersed will help keep this plant at bay. Diggingis not recommended as it creates disturbance,which may favor the spread of the species. Herbi-cides are generally not effective for purple loos-estrife as its seeds are long-lived and therefore thesolution is only short-term. Herbicide applicationsneed to be repeated for several years. As a caution,purple loosestrife may be available at local nurser-ies. Do not introduce into pond areas. (See fig. 3.)

Figure 3 Purple loosestrife

Cattails and common reed (Phragmites)—It isimportant to find out what plants were originallyplanted when the pond or stormwater wetland wasconstructed. The cattails that were planted inthese areas are one of the most beneficial plants atimproving water quality. Ponds and stormwaterwetlands were originally designed with the intentof retaining and/or treating stormwater. Wildlifehabitat was an ancillary benefit at best prior to themid-1990’s.

Shallow water (less than 2 feet) will often be takenover by water-loving plants. Dense, tall emergentvegetation, most commonly cattails andphragmites, may limit waterfowl use of a pond.Cattails provide good wildlife habitat but can takeover a shallow pond. Phragmites is much moreinvasive, taller, and generally does not provide fora scenic view. Once established, phragmites is verydifficult to completely eradicate. (See figs. 4 and 5.)



Figure 4 Cattails

W.S.

Too dense of a stand of cattails and/or phragmitescan reduce populations of invertebrates, amphib-ians, reptiles, and may possibly increase themosquito populations. It is important to keepsome areas of open water. Eradication of thesespecies generally requires the assistance from anatural resource professional. A natural resourceprofessional is a person, who has been trained inecology and/or environmental assessment includ-ing soils, plants, animals, air quality, humaninvolvement, and water quantity and quality(appendix 1).

Figure 5 Phragmites

With respect to diversity, research has shown thatlower pollutant inputs generally yield greater plantdiversity. Conversely, higher pollutant inputs yieldlower plant diversity. Hence, if a pond becomespopulated with Phragmites, cattails or both, it mayindicate a high pollutant load. These species,among others, are two of the best plants forimproving water quality.

It is recommended for the homeowner’s associa-tion to decide early on how much it is willing tospend in time and effort on vegetation mainte-nance.

Wildlife maintenance

Beavers have been known to take up residence infacilities with ponded water. Beavers can cutdown small shrubs and trees adjacent to the pondand may cause an increase in the amount ofponding. If excessive tree damage or ponding isobserved, contact a natural resource professional.Beavers will attempt to block the pond inflow andoutflow structures. (See fig. 6.)



Figure 6 Beaver

Resident Canada geese may also be a problem instormwater wetland or pond. If too many geesepopulate the area, their excretions may cause algalblooms and odor problems. Their paths, createdby feeding on new shoots of grass and continuoustrampling may also cause small gullies to form. Tokeep the resident Canada geese populations low, itis important to maintain an area around the pondto its edge with high grasses and shrubs. A widthof approximately 24 feet is recommended.(See fig. 7.)

Figure 7 Canada geese

Other animals, such as muskrats and groundhogs,may dig out burrows that could deteriorate thestructural integrity of an embankment. Muskrats,in particular, will burrow tunnels up to 6 inches indiameter. Existing burrows should be filled assoon as possible to minimize animal burrowing.Another measure could involve trapping of themuskrats if the problem becomes extensive. (Seefig. 8.)

Figure 8 Muskrat

As a warning to small children, they should notpick up snapping turtles. It is recommended thatlocal fish and wildlife professionals be contactedregarding the number of snapping turtles in aspecific pond to maintain its ecological balance.Snapping turtles differ from other turtles by theirridges on the shell and tail and their hooked beak(fig. 9).

Figure 9 Snapping turtle

Other (aesthetics, mosquitoes, algae, fish

kills, odors)

Mosquitoes are not as big a problem as is oftenperceived. There are proven control strategies thatcan be used. While ponded water can createmosquito and other insect breeding habitat, it alsoprovides habitat for insect predators such asswallows, purple martins, fish, frogs, bats, anddragonflies to keep the nuisance populations incheck. The best mosquito control technique inponds is to prevent stagnant areas from forming inthe permanent pool. This means that all floatingdebris should be removed to preclude still orstanding surface waters that provide breedinghabitat.



Some mosquito management tips

• Wetlands should be managed to minimize theformation of stagnant pools.

• Flowing water conditions should have a minimum velocity of 2 feet per second.

• Provide vegetative cover for the water surface, i.e. encourage duckweed.

• Provide nesting and perching structures forpurple martins, swallows, and bats(appendix 2).

• Encourage aquatic predation — i.e. introducefish and frogs.

• Use bacteria, i.e. biological control.

Fish kills can result from an imbalance in the eco-logical system or if there is direct discharge throughthe storm sewer system, such as swimming pooldraining, vehicle oil changes, car washing deter-gents, and other household products. Fish kills canalso result from algae die-offs. The homeowner’sassociation should adopt a storm sewer stencilingprogram to help promote an understanding thatstorm sewers flow to the basin, then to the stream.

Odors are generally not a problem. Sometimes asulfur odor is evident, but this is usually very local-ized and present when there is very little windcurrent. Algae die-offs can result in excessive odorsfrom the pond. If odor becomes a big problem in awet pond, it may be necessary to allow for a draw-down period within the pond, which would requireassistance from a natural resource professional.



References

Alliance for the Chesapeake Bay and U.S. Fish andWildlife Service, Chesapeake Bay Field Office,Basin scaping to conserve water–ahomeowner’s guide. 1994.

Alliance for the Chesapeake Bay and U.S. Fish andWildlife Service, Chesapeake Bay Field Office,Conservation landscaping–a homeowner’sguide. 1994.

Berger, Louis & Associates, Inc. ConstructedWetlands Design Workshop. A series of paperspresented at the Delaware Erosion, SedimentControl, and Stormwater Conference, Septem-ber 15-18, 1998.

Delaware Department of Natural Resources andEnvironmental Control, Division of Soil andWater Conservation Sediment and StormwaterProgram, Stormwater management pondmaintenance-guidance for the maintenanceorganization, September 1992.

Livingston, Eric H., Earl Shaver, Joseph J. Skupien,and Richard P. Horner. United States Environ-mental Protection Agency, Office of Water,Washington, D.C., operation, maintenance, andmanagement of stormwater managem Water-shed Management Institute Watershed Manage-ment Institute, Inc., August 1997.

Meyer, Fred P., and Lee A. Barclay. Field manualfor the investigation of fish kills. U.S. Fish andWildlife Service, National Fisheries ResearchCenter, LaCrosse, WI and U.S. Fish and WildlifeService, Division of Environmental Contamina-tion, Washington, D.C.

Montgomery County, Department of Environmen-tal Protection, Montgomery County, Maryland.Maintaining urban stormwater facilities–aguidebook for common ownership communi-ties, circa 1990.

Montgomery County, Pennsylvania. Stormwaterbasins—making them more functional andattractive. October 1992.

Nuss, J. Robert, Professor of ornamental horticul-ture. Landscaping with native plants or nativeplants in the landscape. Penn State University.June 1998.

Penn State University, College of AgriculturalSciences Cooperative Extension. Providingwetlands for wildlife while controllingstormwater. circa 1990.

Prince George’s County Department of Environ-mental Resources. How does your gardengrow?–a reference guide to enhancing your raingarden. circa 1998.

Shaver, Earl, and John Maxted. Construction ofwetlands for stormwater treatment. DelawareDepartment of Natural Resources and Environ-mental Control, December, 1993 (unpublished).

State of New Jersey, Department of EnvironmentalProtection, Division of Water Resource. OceanCounty demonstration study–stormwatermanagement facilities maintenance manual.Ocean County Planning and Engineering De-partments and Killarn Associates, June 1989.

United States Department of Agriculture, NaturalResources Conservation Service, NationalAssociation of Conservation Districts, andWildlife Habitat Council. Backyard conserva-tion–bringing conservation from the country-side to your backyard. April 1998.

United States Environmental Protection Agency.Stormwater management system, inspectionforms. Watershed Management Institute, Inc.,August 1997.



Appendix 1

Provided is a suggested format for listing local Natural Resources professionals:

Agency and contact person Address Phone FAX

number number

Local conservation districtoffice

Local Cooperative Educationand Extension Service Office

United States Department ofAgriculture, NaturalResources ConservationService Office

Local Fish and WildlifeService Office for game andnon-game species

Private Consultants

Other Natural Resourceprofessionals

Appendix 2:

Provided are some details for the construction of houses for purple martins, swallows, and bats to helpcontrol the insect populations around stormwater ponds.



Expanded view of martinhouse. A threaded rodinserts through the baseand up through the chimney.

Entrance hole diameter2 1/4". Locate 5/8" ventilationholes 1" below top edge ofsides.

Note: This plan is for a one-story house. To add asecond story, make onemore ceiling unit (25" x 25")four more sides, and fourmore room partitions.

96"

48"

25"

18 3

/4"

6 1/4"9 3/8"

9 3/8"

1" 1"

6 1/4"

3 1/4"

3"

5"

3 1/4" 5/8" diameter3"

12" 12"

6"Side (2)

25" 25" 25"

6"Side (2)

Boards for base

6"Room

partition (4)

End roof support (4)

24"

Center roof support (2)

25" 24"

10"5"10"

14 1/8"

Layout pattern

(not shown)Place 1/2 inch dowelrailing around balconyto keep young fromfalling.

Materials

4' x 8' x 1/4" plywood2" x 2" x 6" for chimney1" x 2" x 14' (base)1" x 1" x 8' (corner blocks)4" x 8" metal window screen4" x 4" x 14' cedar post

Ceiling (1)Floor (1) Roof

side

(2)

18 1/2"6"

6"

1 1/2"

Waste

6"

5"

5 3/4"2 1/4"

Diameter

1 1/2"

25" 23 1/2" 11"11"

Screenplacement

Purple Martin house

(Plans from Penn State College of Agricultural Sciences Cooperative Extension.)



1 3/8"

2 1

/4"

(Up)9

"

4"

13

1/2

"

9"

6"

7"

5 1/2"

5 1/2"

2 1/4"

*

*

5 1/2"

5 1/2"

13 1/2"

5 1/2"

7" 9" 9" 9" 4"

1/4" holes

1/4" holes

Waste

Lumber:One 1" x 6" x 6'

*Note: If slot entrance is used frontwill measure 5 1/2" x 7". Leaveopening at top.

Note:Entrance hole for Great CrestedFlycatcher shouldbe a round hole 1 1/4"in diameter

Pivot nailin front

Pivot nailin back

Two "pivot" nails allow side to swing out for cleaning.Use one nail at bottom to close side.Nail holds side closed.

Side

(2)

Floor

Back

Back Roof Front Side Side Flr

Roof

Front

Nest box for Tree Swallow or Eastern Bluebird

(Plans from Penn State College of Agricultural Sciences Cooperative Extension.)



Roof supports

Spacers

Vent

Side view

Bottom view

Bat house design

1. Measure and mark all wood as per cutting diagrams on page seven. Cut out all parts.2. Cut six pieces of netting 14" x 21". Staple to partitions.3. Screw back to sides, caulking first. Be sure top angles match.4. Cut a piece of netting 16" x 30" and staple to inside surface of back. Be sure netting lies flat and does

not pucker.5. Construct house as per drawings above. Place spacers on partitions, screw top front piece to sides

first then screw bottom front piece to sides to create a 1/2" vent between the two, attach roofsupports, attach roof.

6. Caulk between roof and sides, sides and front pieces, and sides and back piece so as to seal houseairtight. Do not allow screws to protrude into roosting chamber. Paint exterior at least twice withappropriate color.

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