STORMWATER WET POND AND WETLAND 

MANAGEMENT GUIDEBOOK 

Based on material originally produced by: 

Center for Watershed Protection 

8390 Main Street, Second Floor 

Ellicott City, MD 21043 

www.cwp.org
 

www.stormwatercenter.net
 

With assistance from:
 

Tetra Tech, Inc. 

10306 Eaton Place 

Suite 340 

Fairfax, VA 22030 

Under: 

EPA Contract 68-C-99-253
 

Revised by EPA 

February 2009 
Table of Contents 

Table of Contents ........................................................................................................................................ii

Introduction.................................................................................................................................................1

TERMINOLOGY ..........................................................................................................................................2

Section 1: Wet Pond and Wetland Challenges and Opportunities.........................................................5

CHALLENGES.............................................................................................................................................5

Water Quality Impacts ..........................................................................................................................5

Habitat Impacts.....................................................................................................................................5

Health and Safety Issues .......................................................................................................................5

Aesthetics ..............................................................................................................................................6

Maintenance Problems .........................................................................................................................7

OPPORTUNITIES.......................................................................................................................................17

Section 2: Inspection and Maintenance of Existing Ponds and Wetlands ...........................................19

INSPECTIONS ...........................................................................................................................................19

Inspectors............................................................................................................................................19

Inspection Frequency..........................................................................................................................20

Inspection Checklists ..........................................................................................................................21

Documentation of Inspection Findings...............................................................................................21

ROUTINE MAINTENANCE ........................................................................................................................23

MAINTENANCE ACTIVITIES.....................................................................................................................26

Maintenance Activity Profile Sheets .......................................................................................................27

M-1 PERMANENT POOL.....................................................................................................................28

M-2 CLOGGING..................................................................................................................................31

M-3 PIPE REPAIRS.............................................................................................................................33

M-4 VEGETATION MANAGEMENT....................................................................................................38

M-5 DREDGING AND MUCK REMOVAL............................................................................................42

M-6 ACCESS .......................................................................................................................................45

M-7 MECHANICAL COMPONENTS ....................................................................................................47

M-8 NUISANCE ISSUES.......................................................................................................................50

Animals ...............................................................................................................................................50

Waterfowl............................................................................................................................................51

Mosquitoes ..........................................................................................................................................52

Undesirable Plant Communities .........................................................................................................53

Water Quality Degradation ................................................................................................................54

References..................................................................................................................................................56

Appendix A: Unit Costs for Pond and Wetland Maintenance 

Appendix B: Pond and Wetland Checklists 

LIST OF TABLES 

Table 1.1: Mechanisms of Pipe Failure ......................................................................................................11

Table 2.1: Inspection Skill Level Descriptions...........................................................................................19
Table 2.2: Typical Inspection/Maintenance Frequencies for Ponds And Wetlands ..................................20

Table 2.3: Maintenance Activities and Schedules .....................................................................................23

Table 2.4: BMP Maintenance Skill Level Descriptions..............................................................................26

Table M1.1: Permanent Pool Fluctuation Diagnoses.................................................................................29

Table M3.1: Common Pipe Uses, Material, and Maintenance Concerns ...................................................33

Table M3.2: Limitations of common pipe rehabilitation methods .............................................................37
Introduction 

Introduction 

Prior to 1991, a relatively small number of states and municipalities had formal programs in place 

requiring that Best Management Practices (BMPs) be constructed to mitigate runoff pollution. Then, 

beginning in the early 1990's with the advent of Phase I of the federal National Pollutant Discharge 

Elimination System (NPDES) stormwater program, many additional municipalities began programs to 

limit stormwater pollution. These programs typically include the installation of public and private wet 

ponds and wetlands as tools to help control runoff volume and mitigate pollution from runoff and, as a 

result, many of these BMPs have been constructed throughout the United States. Unfortunately, the push 

to construct them has been substantially stronger than the push to actively maintain them. 

The current federal stormwater regulations (e.g., Phase I and Phase II NPDES rules) require permitting 

authorities and permittees to address BMP operation, maintenance, and retrofit as a major programmatic 

component. In addition, as we learn more about the limitations and challenges inherent in these types of 

“one size fits all” approaches to stormwater management, retrofit opportunities are being considered and 

implemented across the country in order to better address water quality issues, aesthetics, and the 

maintenance of existing hydrology. 

For more information regarding retrofitting BMPs, see the Urban Subwatershed Restoration Manual No. 

3: Urban Stormwater Retrofit Practices Manual 1.0 (Schueler, 2007) available at www.cwp.org. 

The primary audience for this Guidebook is Phase I and Phase II NPDES communities. For Phase I 

communities that may have a maintenance program in place, this Guidebook provides technical data and 

information to help improve existing design standards or inspection and maintenance standards. The 

Guidebook provides a technical resource for both Phase I and Phase II NPDES communities. This 

Guidebook provides the inspector, program manager, designer, and owner (i.e., responsible party) with an 

understanding of common stormwater pond and wetland maintenance problems and possible solutions. 

None of the maintenance solutions mentioned in this Guidebook are required by federal regulations, but 

they are meant to help those involved in maintaining these BMPs. 

This Guidebook has been developed expressly to assist communities in developing an integrated 

stormwater management system which includes proper maintenance of existing wet ponds and wetlands, 

the exploration of retrofit opportunities, as well as the implementation of micro-treatment practices and 

low impact development design principles. A set of web-based tools was produced to accompany the 

Guidebook and can be found on the Stormwater Manager’s Resource Center (SMRC) website 

(www.stormwatercenter.net, click on Program Resources then STP Maintenance). 

This Guidebook does not address the maintenance needs of dry ponds or underground detention. These 

practices are not widely recommended as stand alone practices that provide water quality and water 

quantity benefits. Dry ponds, however, exist in many communities, as flood control facilities, and many 

of the maintenance considerations for stormwater ponds and wetlands presented in this Guidebook are 

relevant to dry ponds.

1
Terminology 

Terminology 

Stormwater management terminology is often confusing and can convey multiple meanings. This 

Guidebook uses several terms throughout the text that merit upfront explanation and definition to provide 

the reader with a foundation for the understanding the context of the subsequent text. 

Barrel – The closed conduit used to convey water under or through an embankment: part of the principal 

spillway. 

Channel Protection Volume (Cpv) – Storage volume for the control of downstream channel erosion. 

Emergency Spillway – A dam spillway designed and constructed to discharge flow in excess of the 

principal spillway design discharge. 

Extended Detention (ED) – Design feature that provides for the gradual release of a volume of water to 

increase settling of pollutants and protect downstream channels from frequent storm events. 

Forebay – Additional storage space located near a stormwater practice inlet that serves to trap incoming 

coarse sediments before they accumulate in the main treatment area. 

Micropool – Small permanent pool used to avoid resuspension of particles and minimize impact to 

adjacent natural features. 

Overbank Flood Control, (i.e., Peak Discharge Protection Volume (Qp) – Storage volume needed to 

control the magnitude of flows associated with larger, out of bank flooding events (e.g., 10-year return 

frequency storm events). 

Permanent Pool – Open area of water impounded by a dam, embankment or berm, designed to retain 

water at all times. 

Pond Drain – A pipe or other structure used to drain a permanent pool within a specified time period. 

Principal Spillway – The primary pipe or weir that carries baseflow and storm flow through the 

embankment. 

Riser – A vertical pipe which extends from the bottom of a pond stormwater practice and houses the 

control devices (weirs/orifices) to achieve the discharge rates for specified designs. 

Shallow Marsh – Human-made wetland with water depths ranging from <6” to 18”, planted with native 

wetland vegetation. 

Stormwater Ponds (Figure A) – practices with a permanent pool, or a combination of extended detention 

(ED) or shallow marsh with a permanent pool that provides storage equivalent to the entire Water Quality 

Volume (WQv). Stormwater ponds may also provide channel protection storage volume (Cpv) and 

overbank flood control (Qp) through stormwater detention above the WQv storage. Pond design variants 

include micropool ED ponds, wet ponds, wet ED ponds, and multiple pond systems. 

Stormwater wetlands (Figure B) – shallow marsh areas that treat urban stormwater, and often incorporate 

small permanent pools and/or extended detention storage to achieve the full WQv. Stormwater wetlands 

may also provide peak discharge control (Qp) and channel protection storage volume (Cpv) through 

2
Terminology 

stormwater detention above the WQv storage. Wetland design variants include shallow marsh, 

ED/shallow marsh, and shallow marsh/wet pond. 

Water Quality Volume (WQv) – Storage volume needed to capture and treat runoff associated with 

smaller, frequently occurring storms (e.g., 0.5” – 1” rainfall depth). 

Figure A: Stormwater Pond Schematic 

3
Terminology 

4

Figure B: Stormwater Wetland Schematic 
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Section 1: Wet Pond and Wetland Challenges 

and Opportunities 

Challenges 

Water Quality Impacts 

Stormwater ponds and wetlands are designed and constructed to contain and/or filter pollutants that flush 

off of the landscape. Without proper maintenance, nutrients such as nitrogen and phosphorus that are 

typically found in stormwater runoff can accumulate in stormwater ponds and wetlands leading to 

degraded conditions such as low dissolved oxygen, algae blooms, unsightly conditions and odors. 

Homeowners adjacent to stormwater ponds and wetlands sometimes complain about these issues. When 

nutrient concentrations exceed certain thresholds, the trophic state of the system can change. These excess 

nutrients are often the result of human actions. For example, the amount of fertilizer applied to lawns or 

the method for disposing of leaves and yard waste in residential and other developed land uses can affect 

nutrient loads delivered to ponds and wetlands. Excess sediment from the watershed above can also 

accumulate in wet ponds and wetlands. This sediment can smother the vegetation and clog any filtering 

structures in the BMPs thereby impacting the overall water quality effectiveness of the stormwater BMP. 

In addition, standing water in ponds can heat up during the summer months. This warmer water is later 

released into neighboring waters. 

Without proper maintenance, excess pollutants in ponds and wetlands may actually become sources of 

water quality issues such as poor water color/clarity/odor, low dissolved oxygen leading to plant die off, 

and prevalence of algal blooms. When these stormwater BMPs are “flushed” during a large rain event, the 

excess nutrients causing these problems may be transferred to the receiving waterbody. 

Habitat Impacts 

The placement of ponds or wetlands, especially large regional facilities, in low-lying areas may harm 

natural wetlands or existing riparian habitats. Siting ponds or other structural management practices 

within natural buffer areas and wetlands degrades their functions and may interrupt surface water and 

ground water flow when soils are disturbed for installation. In addition, during large rain events, breaches 

of large wet ponds can cause downstream erosion and degradation due to high volumes and velocity of 

the discharge (EPA, 2005b). 

Health and Safety Issues 

Waterfowl

Geese and mallards may become undesirable year-round residents of a pond or wetland if structural 

complexity is not included in the pond design (i.e., features that limit large contiguous open water areas 

and open short grass loafing areas favored by these birds). Waterfowl that reside in vast numbers eat 

available grasses and emergent plants. Water quality in permanent pools often becomes degraded due to 

increased fecal coliform counts and nutrients from geese and duck droppings. Geese behavior can also be 

noisy during breeding seasons. 

5
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Mosquitoes 

The public’s concern that stormwater ponds and stormwater wetlands generate large mosquito 

populations rivals their concern that good water quality be maintained. Sometimes the public will be 

correct in assuming that the source of local mosquitoes is a nearby pond or stormwater wetland. At other 

times, however, the problem may come from other sources or breeding habitats (either nearby or remote), 

and at times it may be a combination of both. Regardless, stormwater managers will have to deal with the 

public’s perceptions concerning the origins of problematic numbers of mosquitoes. Stormwater managers 

should consider all possible locations that could be contributing to mosquito outbreaks. Mosquito 

population control also factors into many community health issues such as West Nile Virus. 

The proliferation of mosquitoes is usually an early indication that there is a maintenance problem. 

Mosquitoes reproduce by laying eggs in still pools of water or on mud or fallen leaves. A few inches of 

standing water such as found in dry pond depressions, voids in riprap linings, or other inconspicuous 

places can become mosquito-breeding areas. It is possible for mosquitoes to complete their life cycle in 7 

to 10 days, with approximately half being spent in the aquatic stage. Therefore if a shallow pool is 

stagnant for only 4 to 5 days and no predator habitat is available, one generation of mosquitoes can be 

bred. 

Children’s Safety Issues

Standing water in permanent pools often causes public concern for children playing in and around the wet 

ponds. Depending upon the design of the structure, the banks could be steeply sloped which could 

increase the likelihood of children falling in. Often, fences or other impediments are required in order to 

deny access and this often reduces the aesthetic qualities of the structures. 

Aesthetics 

Research has shown that stormwater ponds can increase property values. A survey in Columbia, 

Maryland, found that 75 percent of homeowners felt that permanent bodies of water such as stormwater 

ponds added to real estate values. Seventy-three percent were willing to pay more for property located in 

a neighborhood with stormwater control basins designed to enhance fish or wildlife uses (Adams et al., 

1984; Tourbier and Westmacott, 1992; USEPA, 1995). Residents of a Champaign-Urbana, Illinois 

neighborhood with stormwater ponds stated that lots adjacent to a wet pond were worth an average of 

21.9 percent more than comparable non-adjacent lots in the same subdivision. The same survey revealed 

that 82 percent would in the future be willing to pay a premium for a lot adjacent to a wet pond 

(Emmerling-DiNovo, 1995). In Alexandria, Virginia, condominiums alongside a 14-acre runoff detention 

pond sold for $7,500 more than comparable units not adjacent to the pond (USEPA, 1995). 

Like wet ponds, wetlands can increase adjacent property values. One study in Boulder, Colorado, found 

that lots located alongside a constructed wetland sold for up to a 30 percent premium over lots with no 

water view (USEPA, 1995). In Wichita, Kansas, a developer enhanced existing wetlands rather than 

filling them and the waterfront lots sell for a premium of up to 150 percent of comparable lots (USEPA, 

1995). 

However, inherent in these findings is the assumption that the ponds are designed for aesthetic appeal and 

are maintained as necessary to function properly as a water quality structure and a neighborhood amenity. 

If the commitment by the owner to maintain the structure is not solid and long-term, however, the 

structure can quickly become an eyesore and a blight in the neighborhood (USEPA, 2005b). 

6
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Maintenance Problems 

Maintenance is necessary for a stormwater pond or wetland to operate as designed on a long-term basis. 

The pollutant removal, channel protection, and flood control capabilities of ponds and wetlands will 

decrease if: 

• Sediment accumulates reducing the storage volume, 

• Debris blocks the outlet structure, 

• Pipes or the riser are damaged, 

• Invasive plants take over and out-compete the planted vegetation, 

• Slope stabilizing vegetation is lost, or 

• The structural integrity of the embankment, weir, or riser is compromised. 

Pond and wetland maintenance activities range in terms of the level of effort and expertise required to 

perform them. Routine pond and wetland maintenance, such as mowing and removing debris or trash, is 

needed multiple times each year, but can be performed by citizen volunteers. More significant 

maintenance such as removing accumulated sediment is needed less frequently, but requires more skilled 

labor and special equipment. Inspection and repair of critical structural features such as embankments and 

risers, needs to be performed by a qualified professional (e.g., structural engineer) who has experience in 

the construction, inspection, and repair of these features. 

This Guidebook identifies appropriate frequencies and skill levels needed for each maintenance activity to 

provide program managers and responsible parties with an understanding of the relative effort and 

expertise that may be required. 

Program managers and responsible parties need to recognize and understand that neglecting routine 

maintenance and inspection can lead to more serious problems that threaten public safety, impact water 

quality, and require more expensive corrective actions. Appendix A of this Guidebook provides program 

managers with specific maintenance activity unit cost and frequency information. 

It should be noted that structural stability issues associated with embankments and pipes (e.g., earth, 

concrete and metal repairs) are not addressed in the Guidebook. While earth, concrete and metal repairs 

are essential elements of stormwater pond and wetland maintenance, the assessment and design for repair 

of such items should be performed by a qualified structural or geotechnical engineer and are beyond the 

scope of this document. Where applicable, the importance of conducting a more thorough inspection of 

structural stability is called out in this Guidebook. More detailed guidance on structural inspections and 

repairs for ponds and wetlands can frequently be obtained from state dam safety agencies or local Natural 

Resources Conservation Service (NRCS) offices. 

Permanent Pool 

For stormwater ponds and wetlands, a common maintenance issue is abnormally high or low permanent 

pool levels. Permanent pools are normally designed for a stable water surface elevation between storm 

events that will rise during and shortly after a significant rain event. Pond elevations should not dip 

appreciably below the specified level unless under extreme conditions, such as drought. Ponds used as an 

alternative water supply for irrigation or other reuse options are also an exception. 

Permanent Pools Too Low

Permanent pools provide functions including aquatic habitat, water quality protection, and visual 

aesthetics. When pool levels drop too low, water quality is threatened by algal blooms and anoxic 

conditions, which can lead to fish kills and plant stress that in turn can undesirably reduce predation on 

mosquito larvae. 

7
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Pond and wetland facilities should keep their permanent pools at or near the elevation of the low flow 

orifice or weir. Low permanent pools that are not drought-induced are usually caused by leaks either 

(1) in the pond embankment/perimeter, (2) in the principal spillway, or (3) in the pond bottom. 

Leaks within the facility embankment or through the bottom of the pond are often difficult to locate 

unless they are large or severe. Active dam leaks often produce a vortex, an unmistakable indication of a 

leak. Water may leak through sinkholes formed in pond bottoms or infiltrate through porous underlying 

soils. 

 

Leaks in the principal spillway riser are fairly easy to spot. Leaks in the barrel are harder to locate, as they 

require either manual entry or remote TV inspection. Broken or missing valves can also lead toward 

abnormally low water levels in ponds. 

If the permanent pool becomes low during or immediately following construction, it can be a sign of 

poorly compacted berms or dams or damaged or leaking barrels and risers. All of these features should 

be inspected during and immediately following construction. A low pool may also signify that the water 

budget was miscalculated during design. 

Permanent Pools Too High

A clogged low flow orifice is the most common 

reason for a higher than normal permanent pool level 

(Figure 1.1). Clogging is discussed in detail in the 

next section. 

The high permanent pool disrupts the pond or 

wetland function by: 

• Decreasing storage volume thereby reducing 

the ability to attenuate flood flows. 

• Causing the flow velocity leaving the pond or 

wetland to be greater than the design release 

rates therefore increasing downstream 

channel erosion. 

• Compromising water quality because runoff 

short-circuits1

 the pond and enters the downstream channel without adequate residence time for 

quality treatment. 

Figure 1.1: Abnormally high permanent 

pool – Water spills into 2- year weir 

because beavers have clogged the low 

flow orifice. 

• Killing riparian trees by flooding their roots which are not normally submerged in the high pool. 

• Compromising public access and safety when adjacent pathways and recreational use areas are 

flooded. 

• Saturating areas designed to be outside the permanent pool potentially causing mosquito-breeding 

habitat to be created. (Basins should be designed so that pooling or ponding of water in isolated 

peripheral areas does not occur for more than 4 consecutive days.) 

 

1

 Short circuiting is the term used when stormwater runoff residence times in the pond are reduced. 

8
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Clogging 

Clogged low flow orifices2 and weirs represent the most frequent, persistent maintenance item common 

to all types of ponds or wetlands. Serious impacts can easily be minimized through design and retrofit

However, without frequent maintenance, even openings with trash racks can become clogged. 

. 

esign, 

 

Clogging occurs when debris or sediment accumulates at riser/weir openings or outfalls, blocking the 

flow of water (Figures 1.2 and 1.3). Debris includes vegetative material such as dead plants, twigs, 

branches and leaves as well as litter and trash. Large storms can transport large amounts of debris. 

Vandalism and nuisance problems such as beavers contribute to clogging as well. 

 

In addition to the permanent pool fluctuation problems noted above, clogged orifices can cause the 

following concerns: 

Figure 1.3: Riser without trash rack Figure 1.2: Flattop riser covered with 

debris. 

• Obscuring the upstream slope of embankments, preventing adequate inspection. 

• Blocking low flow openings causing overtopping of the embankment or dam in the event of a 

flood. 

• Blocking underwater spillway inlets such as ‘reverse slope’ pipes once floating debris becomes 

waterlogged and sinks. 

Pipe Repairs 

Pipes and riser structures are designed to convey stormwater safely and at a controlled rate. If pipes or 

risers are damaged, these functions will be affected. Often, risers are made from the same materials as 

pipes, and therefore can be treated as such with respect to maintenance and repair. 

Pipes through the embankment – the principal spillway and other utilities – are designed to be watertight. 

If damaged, pipes may leak water into the embankment through holes or separated joints (Figure 1.4). 

This can lead to piping of water along the pipe, which results in erosion (Figure 1.5) and can lead to 

embankment failure. 

Pipe damage can occur at any point in a pond or wetland lifecycle and can be caused by improper d

poor construction, inadequate maintenance, or wear and tear. While problems with design and 

2

 Low flow orifices or openings pass baseflow and control detention time in ponds and wetlands. 

9
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Figure 1.5: Severe erosion around riser 

and barrel Figure 1.4: Pipe invert abrasion 

construction are preventable, wear and tear is a wild card. Extreme storm events, chemical attack, 

abrasion, or other unforeseen circumstances may challenge the longevity of the design. 

Table 1.1 presents mechanisms of pipe failure and the lifecycle point where the failure typically occurs. 

10
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Table 1.1: Mechanisms of Pipe Failure

Lifecycle Point Mechanism 

Design Construction Wear and Tear 

Joint Separation 

The physical separation of different sections of pipe along 

the barrel typically caused by differential settlement or 

improper pipe compaction. 

9 9 9

Buoyancy Failure

Failure occurs because trapped air in the pipe creates 

uplift forces. This force can cause the ends of the pipe to 

bend upward or the entire culvert to be displaced. 

9 9

Static and Dynamic Loading

Overburdening (placing too much static weight on the 

pipe) or inappropriate dynamic loading (e.g. driving a 

heavy piece of equipment over a pipe with insufficient 

backfill) causes failure. 

9 9

Material Compatibility

Designs with several pipe materials may not bond well, 

especially if dissimilar pipe materials are placed in precast forms on holes, and then grouted to be water-tight. 

Most non-cementatious materials do not bond well to 

concrete or masonry as these materials tend to shrink 

over time. It is common to see leaks in the control 

structures where plastic or steel pipes enter through 

concrete. 

9 9

Installation Technique

See Section 2 for description. 9

Insufficient Compaction

See Section 2 for description. 9

Vandalism

Acts include filling with rubble and debris and crushing 

exposed ends of plastic and clay piping. 

9 9

Corrosion Fatigue

Fatigue type cracking of metal caused by repeated or 

fluctuating stresses in a corrosive environment is 

characterized by shorter life than would be encountered 

as a result of either the repeated or fluctuating stress 

alone or the corrosive environment alone. 

9 9

U/V Deterioration

Plastic piping is susceptible to deterioration from sunlight 

and even UV resistant material will become brittle and 

fracture given enough exposure. 

9

Freezing and Cracking

Water pockets in the pipes, which are constantly exposed 

to surface water, freeze and thaw several times each 

winter, stressing and weakening the pipe. 

9

Internal Corrosion

Corrosion that occurs inside a pipe because of the 

physical, chemical, or biological interactions between the 

pipe and the water. 

9

Abrasion

Deterioration of a surface by the abrasive action of moving 

fluids - this is accelerated by the presence of solid 

particles or gas bubbles in suspension 

9

11
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Vegetation Management 

Vegetation management involves sustaining the landscaping as designed and preventing the growth of 

unwanted species. There are three primary types of vegetation that require management and maintenance 

in stormwater ponds and wetlands: turf and grasses, wetland plantings, and trees and forested areas. 

Figure 1.6: Mowed dry pond bottom 

Turf and Grasses

Native and non-native grasses are the most common 

vegetative stabilization used in stormwater pond and 

wetland construction today for reasons of aesthetics, ease of 

maintenance, and price (Figure 1.6). The root system of any 

vegetative cover holds the surface soil in place and protects 

the slopes from wind and surface runoff erosion. 

A regularly scheduled program of cutting and trimming of 

grass at facilities during the growing season will help to 

maintain a tightly knit turf and will also help prevent 

diseases, pests and the intrusion of weeds. 

Wetland Plantings 

Native wetland plants promote biological uptake of pollutants (Figure 1.7). Though natural propagation is 

desirable, vegetation will still need to be managed to meet the design goals. Depending on the design of 

the system, vegetation harvesting3

 and control of aquatic plants (such as cattails and phragmites) may be 

required. 

Trees and Forested Areas 

Figure 1.7: Wetland vegetation 

Trees are often planted for aesthetic, stabilization, and 

temperature control reasons. They have to be maintained to 

prevent clogging of orifices with debris and the spread to 

unwanted areas. 

Vegetation management is probably the most frequent 

maintenance activity that occurs in association with the 

upkeep of stormwater ponds and wetlands. While the activity 

requires little expertise or special equipment, there are still 

important site conditions to be aware of in order to maintain a 

properly functioning stormwater pond or wetland. Examples 

of common vegetative problems include: 

• Trees and brush with extensive woody root systems can destabilize dams, embankments, and side 

slopes due to the creation of seepage routes (Figure 1.8). 

• Monolithic stands of cattails (Typha sp) and Common Reed (Phragmites australis) can take over 

shallow marsh wetlands and drainage swales, out-competing other useful native emergent plants 

that would otherwise establish more varied, mature marsh plant ecology. Nuisance aquatic weeds 

are like any other pest; they are opportunistic and invasive. Small shallow ponds provide optimal 

conditions for their proliferation. 

• Misunderstanding of which areas of a stormwater pond or wetland require mowing or 

management can lead to under or over management. 

 

3

 Vegetation harvesting is removing vegetation on a routine basis and land applying it in an upland 

location. The purpose of harvesting is to remove plant material before winter die-off to prevent nutrients 

from reentering the water column and being flushed downstream. 

12
Section 1: Wet Pond and Wetland Challenges and Opportunities 

• Unseen areas may be neglected. For example, the downstream dam face of an embankment is the 

most commonly neglected and most critical area requiring regular clearing. 

• Heavy pedestrian use, particularly along the top of dams and along pond edges can create patches 

of bare soil. 

• Industrial pollutants can cause alteration in the chemical composition and pH of the discharge 

water, which, in turn, can affect plant growth even when the source of contamination is 

intermittent. Nutrients increase plant growth and acidic discharges can decrease vegetation. 

• Un-maintained vegetation can obscure large portions of the dam, preventing adequate visual 

inspection and limiting access to the dam and surrounding areas. Access is critical in emergency 

situations (Figure 1.9). 

• Excessive vegetation often provides habitat for rodents and burrowing animals. (See Nuisance 

and Health Issues.) 

• Excessive vegetation can affect the flow rates through earthen spillways. 

Figure 1.8: Woody vegetation on 

embankment 

Figure 1.9: Excessive vegetative growth 

obscures riser 

Dredging and Muck Removal 

Sediment accumulates in stormwater ponds and wetlands by design and eventually requires removal to 

maintain efficiency and safety (Figure 1.10). The maintenance interval for removing accumulated 

sediment will vary based on the design parameters. 

Stormwater ponds and wetlands are frequently presumed to be 80% efficient in trapping total suspended 

solids. Sources of solid and semisolid wastes retained in a pond or wetland include: 

• Soil loss from lawns and open areas 

• Litter and yard waste 

• Sand from winter sanding operations 

• Natural leaf litter and down branches 

• Grit from roofing shingles 

• Atmospheric deposition wash off 

• Construction sediments 

• Erosion from upstream conveyance swales 

• Asphalt grit 

As sediment accumulation is expected, stormwater ponds and wetlands should be designed with sediment 

forebays, pond drains, access for sediment removal, and a designated onsite disposal area. These 

13
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Figure 1.11: Muck removal and slope 

dressing by long reach backhoe 

Figure 1.10: Sediment accumulation in a 

dry pond 

considerations will reduce eventual costs of sediment removal, as major cost items in dredging include 

dewatering, transport of sediment for off-site disposal, re-establishment of wetland communities, and 

accessing the site (Figure 1.11). 

Ease of Access 

Access is needed to all parts of the stormwater treatment facility for inspection maintenance. Key access 

points include: 

• Riser structure 

• Embankments 

• All outfalls and inlets 

• Forebays and pond bottoms 

• Aerators and electrical panels 

Additionally, public access should be limited to only 

some pond or wetland components to prevent 

vandalism. 

Access for Regular Inspection and Maintenance:

Frequent maintenance items usually involve small 

pieces of equipment such as mowers and light trucks. 

Access also involves facilitating inspector access to, 

into and through a stormwater pond or wetland to note 

items in need of repair. Figure 1.12 shows good 

maintenance access to a facility. Critical 

appurtenances should be easily and safely accessed for 

inspection and minor maintenance, such as lubricating 

a pond valve. Access must be provided to inspect for 

mosquito production and take appropriate actions 

when necessary. Figure 1.13 shows good manhole 

access. 

Figure 1.12: Pond with good access to 

public road. 

Typical problems that impede maintenance access 

include: 

Figure 1.13: Ladder and steps in riser. 

14
Section 1: Wet Pond and Wetland Challenges and Opportunities 

• Inadequate or unsafe ingress to and egress from facility components 

• Fencing that does not have gates. 

• Pond risers installed without provision for access. 

• Manhole blocked by debris. 

• Air monitoring results that are unsafe. 

• Steps/ladder that are missing, broken, unsecured, non-aligned, or under water. 

• Trash racks or valves that are blocking safe access to riser. 

• Heavy gratings and hatches 

• Corroded locks 

• Aerators that require special considerations, such as a boat or manual power disconnections. 

Infrequent Maintenance Access

Less frequent maintenance items, such as dredging, 

will require site access for heavy equipment (e.g. 

Figure 1.14) including backhoes, dump trucks, and 

vacuum trucks. Maintaining ingress and egress points 

for the facility at all times is wise in case emergency 

repairs are needed. Lack of a permanent access route 

necessitates the creation of a temporary route (Figure 

1.15) which may be disruptive to plant life and 

community aesthetics. 

Access for major repairs is similar to construction 

access and involves protecting existing trees, 

pavement, utilities, and signage against damage while 

accessing the areas needing repair. Figure 1.14: Typical large maintenance 

equipment. 

Many older stormwater ponds and wetlands do not 

adequately provide stable access and staging areas for 

repair equipment. Older facilities typically include a 

designated ingress point, but they often suffer from 

one of the following shortfalls: 

• There is no way to safely move equipment 

over existing curbs and pavement without 

damage. 

• The slope of the access path is too steep, 

especially if wet. 

• The path is not wide enough to accommodate 

heavy repair equipment. Figure1.15: Temporary access road 

widening • The path is overgrown with significant 

vegetation or has been planted with landscape 

quality material. 

• Smaller structures such as decks and sheds are built in access areas (gardens and dump areas are 

also common). 

• There is no legal access easement allowing for access from a public right-of-way to the facility; 

this can be a contentious issue if the only practical access is across land not owned by the pond or 

wetland owner. 

• No staging or equipment area is available once heavy equipment is onsite (contractors often need 

material storage space and a place to securely park heavy equipment overnight). 

15
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Vandalism protection:

Vandalism protection involves common sense measures such as chaining and locking mechanical 

components (valves and security manhole accesses). It also includes the use of well-designed trash racks 

to discourage vandalism and reduce clogging. 

Although there are many passive options to keep people away from a facility, including screening with 

vegetation and locating the pond or wetland out of eyesight, the most common method of exclusion is 

fencing. Fences can be damaged by many factors, including vandalism and storm events. Timely repair 

will maintain the security of the site and reduce potential liability. 

Appurtenances should be locked with key locks as opposed to more corrosion-prone combination locks. 

The design life of the typical lock left exposed to the elements is one to five years. They often become 

corroded and cannot be opened at time of inspection or maintenance. Therefore this often requires that the 

chain be cut and a new lock placed. For municipalities, one master key should open all stormwater 

facility locks to avoid confusion if keys are lost. 

Typical locations for locks include the following: 

• Chaining all valves with hand wheels 

• Sluice gates 

• Entrance points through fencing 

Damage of Mechanical Components 

Pond and wetland mechanical components tend to be 

simple and few in numbers. They include: 

• Valves 

• Sluice gates and flap gates 

• Anti-vortex devices 

• Pumps 

• Access hatches 

• Aerators (fountains, bubblers, diffusers) 

• Electric control panels for aerators 

These components should be inspected at least 

annually and repaired according to manufacturer’s 

recommendations. Mechanical components may be 

damaged as a result of: Figure 1.16: Corroded plumbing and 

valve. 

• Clogging 

• Sediment accumulation 

• Vandalism 

• Weathering or corrosion (Figure 1.16) 

• Extended use 

• Lack of preventative maintenance such as lubrication 

Design considerations and preventative maintenance can address most of these issues. Failure to maintain 

these items could prevent the pond from functioning as designed, cause the problems described in the 

Clogging and Access sections, or, in the case of aerators, affect water quality. 

16
Section 1: Wet Pond and Wetland Challenges and Opportunities 

Nuisance Issues 

Rodents usually damage ponds or wetlands through burrowing or dam building. Burrowing may 

jeopardize embankment stability for dams and berms; beaver dam building reduces live storage and 

creates clogging problems. 

The following animals routinely cause destruction to 

embankments and berms: groundhogs/woodchucks, 

muskrats, prairie dogs, badgers, pocket gophers and 

Richardson ground squirrels. Animal burrows can 

deteriorate the structural integrity of dams, 

embankments and slopes (Figure 1.17). Muskrats in 

particular will burrow tunnels up to 6 inches in 

diameter. 

Figure 1.17: Animal burrow in pond 

embankment. 

Beaver activity in urban areas usually results in tree 

and vegetation mortality, flooding from dam building 

that causes water to encroach into unwanted areas, 

and impairment of stormwater management facilities. 

Beaver activity can be either an aesthetic issue that 

detracts from the visual appeal of the community, or a 

property damage issue that poses liability concerns. 

Management options for beaver control include 

trapping, dam and lodge removal, and the use of beaver “baffles.” 

Opportunities 

Owners of existing wet ponds or wetlands should evaluate them for retrofit opportunities to improve 

water quality benefits. Not all facilities can or should be retrofitted and the evaluation is based on a 

number of factors. Facilities that cannot be retrofit should be inspected and maintained to retain optimum 

performance with the least resource expenditure (see Section 2). 

The National Management Measures Guidance to Control Nonpoint Source Pollution from Urban Areas

(EPA, 2005b) outlines the following steps for determining retrofit opportunities for existing ponds and 

wetlands: 

Step One: Identify, Prioritize, and Schedule Retrofit Opportunities 

In the watershed assessment phase of the urban runoff management cycle, watershed managers should 

identify waterbodies that have been degraded by urban runoff and prioritize them for restoration based on 

the costs and benefits for watershed stakeholders. One method to halt further degradation and initiate 

waterbody improvement is to retrofit existing runoff management practices or conveyance structures. It is 

important for watershed managers to have clear goals and realistic expectations for retrofitting existing 

structures. Each retrofit project should be planned in the context of a comprehensive watershed plan, and 

managers should have a clear set of objectives to ensure that the project results in measurable 

improvements in hydrologic, habitat, and/or water quality indicators. 

17
Section 1: Wet Pond and Wetland Challenges and Opportunities 

18

Step Two: Evaluate existing data 

The first step in identifying candidate sites for stormwater retrofitting is to examine existing data. These 

data can include results from a watershed assessment, topographic maps, land use or zoning maps, 

property ownership maps, aerial photos, and maps of the existing drainage network. For example, results 

from a watershed assessment can be used to identify areas with good habitat and water quality that should 

be protected, as well as areas with poor habitat and water quality that need to be improved. Topographical 

maps can be used to delineate drainage units within the watershed at the subwatershed and catchment 

levels. Land use or zoning maps can be used to estimate areas of high impervious cover to target areas 

that contribute a large amount of runoff to receiving waters, while property maps provide land ownership 

data. Finally, aerial photographs can be used to identify open spaces that can be more easily developed 

into runoff management facilities. According to the Center for Watershed Protection (Center for 

Watershed Protection, 1995a), the best retrofit sites: 

• Are located adjacent to existing channels or at the outfall of storm drainage pipes; 

• Are located within an existing open area; 

• Have sufficient runoff storage capacity; 

• Can divert runoff to a potential treatment area (forested or vegetated area) or structural 

management practice; and 

• Have a sufficient drainage area to contribute meaningfully to catchment water quality. 

Information for potential retrofit sites, such as location, ownership, approximate drainage area, utility 

locations, and other pertinent details, can be compiled in a retrofit inventory sheet (Center for Watershed 

Protection, 1995a). A site visit can provide information on site constraints, topography, adjacent sensitive 

land uses, receiving water conditions, utility crossings, and other considerations that would affect the 

feasibility of implementing the management practice. At this point, a conceptual sketch for rerouting 

drainage and siting management practices should be drawn and preliminary cost estimates made for each 

site. 

Step Three: Choose appropriate management practices based on site conditions 

Deciding which site to select to retrofit can be based on several different factors in addition to site 

limitations and cost. For instance, the preliminary goals of a retrofit program may be to preserve streams 

or reaches known to have high-quality habitat or exceptional water quality. The goal of another program 

may be to restore poor habitat and degraded water quality. The program may elect to target particular land 

uses thought to contribute the majority of pollutants to receiving waters. Retrofit facilities also can be 

installed to treat runoff from large parts of a watershed or subwatershed (regional controls), thereby 

requiring fewer overall projects. Once retrofit sites are identified and prioritized, a schedule for updating 

old facilities should be devised. 

If a pond or wetland stormwater management facility cannot be retrofitted, it is still critical that it be 

maintained properly to function properly and not become a nuisance or a pollutant source itself. 

The Center for Watershed Protection has developed a manual to assist property owners in retrofitting 

existing stormwater management facilities, including, but not limited to, wet ponds and wetlands 

(Schueler, 2007). 

The manual provides guidance regarding the selection of practices viable for retrofit and their locations 

within appropriate subwatersheds as well as the steps to take when designing, implementing and 

maintaining the retrofits. 
Section 2: Inspection and Maintenance of Existing Ponds and Wetlands 

Section 2: Inspection and Maintenance of 

Existing Ponds and Wetlands 

Long-term functioning of stormwater BMPs requires periodic inspections, routine maintenance, and 

corrective actions. Often the efforts of both community stakeholders and stormwater management 

professionals are necessary to insure the management practices are operating as they were intended. 

 

Inspections 

Inspections help the stormwater manager monitor the safety, longevity, and effectiveness of these 

practices over time. This section outlines some tips for inspecting ponds and wetlands, focusing on the 

inspection frequency, inspection checklists, documentation photographs, and repair item documentation. 

Inspectors 

Ongoing post-construction inspections of stormwater ponds and wetlands can be conducted by a variety 

of stakeholders including: 

 Professional engineers and specialized contractors 

 Municipal Inspectors and Maintenance Crews 

 Commercial, Institutional, and Municipal Owners 

 Concerned citizens and adjacent homeowners 

 Homeowners Associations 

 Property Managers 

Property owners should reach an agreement with the property management, maintenance team or 

landscaping contractor to conduct frequent inspection and maintenance items such as mowing, checking 

for clogs, and debris removal. Clearly identify the expectations so that the landscaping design is preserved 

for optimal stormwater treatment. 

Attentive landscapers, adjacent homeowners, and homeowner associations can be the first to identify 

potential problems. A homeowner checklist is included in Appendix B. Several local maintenance 

guidebooks aimed at citizens are also available on the SMRC website (www.stormwatercenter.net) under 

Program Resources, STP Maintenance, STP Maintenance Educational Materials. 

The range of experience needed to diagnose a problem during inspection is quantified below in Table 2.1. 

These skill levels are used to describe the inspection items in Table 2.2. 

Table 2.1: Inspection Skill Level Descriptions

Skill Level Description 

0 No special skills or prior experience required, but some basic training via 

manual, video, or other materials is necessary. 

1 Inspector, maintenance crew member or citizen with prior experience with 

ponds and wetlands 

2 Inspector or contractor with extensive experience with pond and wetland 

maintenance issues 

3 Professional engineering consultant 

19
Section 2: Inspection and Maintenance of Existing Ponds and Wetlands 

Inspection Frequency 

Ponds and wetlands should ideally be inspected on a monthly basis for minor items, and annually for 

major inspection items, such as structural components. In reality, many communities are unable to inspect 

all of their ponds this frequently, and a more typical scenario is providing inspection once every three 

years. This less frequent full inspection can be supplemented with a routine inspection conducted by a 

property owner or contractor responsible for maintenance. In the case of wetlands, an additional 

inspection may be required after the first year to ensure that wetland plantings remain viable. 

Table 2.2 shows the frequency timeline with typical inspection and maintenance items at these times. 

Inspection frequency may be refined by the maintenance history of the practice as generated by ground 

crews charged with maintenance and mowing, or other interested parties. The profile sheets referenced 

under maintenance items are provided in Section 3. 

Table 2.2: Typical Inspection/Maintenance Frequencies for Ponds And Wetlands 

Frequency Inspection Items 

(Skill Level) 

Maintenance Items 

(Related Profile Sheet) 

One time - 

After First Year 

 Ensure that at least 50% of wetland 

plants survive (0) 

 Check for invasive wetland plants (0) 

 Replant wetland vegetation (See M-4 

Vegetation Management) 

Monthly to 

Quarterly or 

After Major 

Storms (>1”) 

 Inspect low flow orifices and other pipes 

for clogging (0) 

 Check the permanent pool or dry pond 

area for floating debris, undesirable 

vegetation (0) 

 Investigate the shoreline for erosion (0) 

 Monitor wetland plant composition and 

health (0-1) 

 Look for broken signs, locks, and other 

dangerous items (0) 

 Mowing – minimum Spring and Fall (See 

M-4 Vegetation Management) 

 Remove debris (M-2 Clogging) 

 Repair undercut, eroded, and bare soil 

areas (See M-4 Vegetation Management) 

Several Times 

per Hot/Warm 

Season 

 Inspect stormwater ponds and 

stormwater wetlands for possible 

mosquito production (0-1) 

 Inspect for mosquitoes (See M-8 Nuisance 

Issues) 

Semi-annual to 

annual 

 Monitor wetland plant composition and 

health (0-1) 

 Identify invasive plants (0-1) 

 Ensure mechanical components are 

functional (0-1) 

 Setup a trash and debris clean-up day 

 Remove invasive plants (See M-4 

Vegetation Management) 

 Harvest wetland plants (See M-4 

Vegetation Management) 

 Replant wetland vegetation (See M-4 

Vegetation Management) 

 Repair broken mechanical components if 

needed (See M-7 Mechanical Components)

Every 1 to 3 

years 

 Complete all routine inspection items 

above (0) 

 Inspect riser, barrel, and embankment for 

damage (1-2) 

 Inspect all pipes (2) 

 Monitor sediment deposition in facility 

and forebay (2) 

 Pipe and Riser Repair (See M-3 Pipe 

Repair) 

 Complete forebay maintenance and 

sediment removal when needed (See M-5 

Dredging and Muck Removal) 

2-7 years 

 Monitor sediment deposition in facility 

and forebay (2) 

 Complete forebay maintenance and 

sediment removal when needed (See M-5 

Dredging and Muck Removal) 

20
Section 2: Inspection and Maintenance of Existing Ponds and Wetlands 

Table 2.2: Typical Inspection/Maintenance Frequencies for Ponds And Wetlands 

Frequency Inspection Items Maintenance Items 

(Skill Level) (Related Profile Sheet) 

5-25 years 

 Remote television inspection of reverse 

slope pipes, underdrains, and other hard 

to access piping (2-3) 

 Sediment removal from main pond/wetland 

(See M-5 Dredging and Muck Removal) 

 Pipe replacement if needed (See M-3 Pipe 

Repair) 

Inspection Checklists 

A community should use standard inspection checklists to record the condition of all practices, and 

particularly those that need frequent maintenance. Most communities will find it easier to track 

maintenance electronically, using either a database or spreadsheet, rather than relying on paper files. 

Well-designed checklists can be integrated with these systems to prioritize maintenance, track 

performance over time, and relate design characteristics to particular problems. To effectively achieve 

these goals, the checklist should: 

 Be quantitative, so that maintenance can be easily prioritized. 

 Be very specific about possible problems to reduce subjectivity. 

 Be concise with text particularly if integrated with a database, so that the checklist user will not 

be inundated with too much text. 

 Link problems to specific actions. 

 Where possible, track the function of the pond or wetland over time for future research and 

design. 

Inspection checklists should also be grouped in the order the inspector would inspect the practice. For 

example, ponds should typically be inspected from downstream to upstream, so the investigation begins 

with the outfall channel. Sample checklists are presented in Appendix B. 

For additional example checklists, consult SMRC (www.stormwatercenter.net). Checklists can be found 

by clicking “Program Resources” then “STP Maintenance” and “Maintenance Checklists, Reminders, and 

Notifications.” In addition to providing detailed “professional” checklists for various BMPs, it also 

includes a simplified pond inspection checklist for homeowners. A Pond-Wetland Maintenance Checklist 

can also be found as part of Tool #6 of the Post-Construction Guide (www.cwp.org/postconstruction). 

Documentation of Inspection Findings 

Inspectors should clearly identify the extent and location of problems identified during inspection. In 

addition to clearly describing problem areas on the checklists, inspectors should help repair crews locate 

repairs both at the site and on design plans. 

Immediate Concerns

While all maintenance and inspection items are important, some maintenance concerns actually pose an 

immediate safety concern. Many of these are caused by missing or damaged elements that would 

normally prevent access by the public. Examples include missing manhole covers or trash racks, missing 

or damaged fencing that normally prevents access to a pond with steep side slopes, or a missing or 

damaged grate at a large inflow or outfall pipe. 

Another set of immediate pond and wetland repairs involve dam safety or flooding hazards. If a practice 

shows signs of embankment failure, or if an inspector is unsure, an appropriately qualified person or 

21
Section 2: Inspection and Maintenance of Existing Ponds and Wetlands 

engineer should be called in to investigate the situation immediately. Similarly, cracks in a concrete riser 

that drains a large area may pose a dam safety threat. 

As-built Drawings

The inspector should bring a copy of the as-built plan of the practice to mark potential corrections and 

problem areas on this plan. The marked up as-built plan should be stored either digitally or in a paper file 

system so that it can be brought out to confirm that maintenance was performed correctly on the followup inspection. 

Photographs

Inspectors should take a core set of documentation photographs of practices being inspected. In addition, 

specific problem areas should be photo documented. A recommended set of core photographs for ponds 

and wetlands include: 

• Vehicle access points. 

• Overview of practice. 

• Overview of principal spillway structure. 

• Upstream face of dam embankment. 

• Downstream face of dam embankment. 

• Outfall to practice and downstream outfall from practice. 

• Emergency spillway (if applicable). 

In addition, because of the large number of photographs that will likely be generated, a digital camera 

should be used when possible to allow photographs to be stored electronically. (In advanced database 

programs, these photographs can be retrieved digitally). Finally, photographs should be named using a 

standard convention. The photograph name should indicate the practice identification number, feature (or 

problem) being photographed, and date of photograph. 

 

Field Marking

Inspectors can highlight key areas of concern with spray paint or other marker. This is particularly useful 

for problems that may otherwise be difficult to find by others. Marking should be used as discretely as 

possible. For example, only dots sprayed at the base of trees should be used to mark limits of clearing for 

vegetation removal. Figures 2.1 to 2.4 show examples of helpful spray paint markings. 

 

Figure 2.1: Marking outfall deficiencies. Figure 2.2: Marking trees to be removed.

22
Section 2: Inspection and Maintenance of Existing Ponds and Wetlands 

 

Figure 2.3: Marking pipe joint 

separation 

Figure 2.4: Marking a hole in gabion 

fabric 

Routine Maintenance 

In addition to routine inspection, routine maintenance needs to be performed to maintain the 

function of the control structure. Runoff treatment controls require specific maintenance 

activities at varying schedules. The cost and time commitment should be planned for all 

maintenance activities delegated to a responsible party, regardless of whether it is a contractor, 

local municipality, or community stakeholder. Table 2.3 describes maintenance activities, and 

schedules for several categories of stormwater management strategies. 

Table 2.3: Maintenance Activities and Schedules 

Category Management 

Practice Maintenance Activity Schedule 

— Cleaning and removing 

debris after major storm 

events (>2” rainfall) 

— Harvesting of vegetation 

when a 50% reduction in the 

original open water surface 

area occurs 

— Repairing embankment and 

side slopes 

— Repairing control structure 

Annual or as 

needed 

— Removing accumulated 

sediment from forebays or 

sediment storage areas 

when 60% of the original 

volume has been lost 

5-year cycle 

Ponds 

Extended 

detention 

ponds, wet 

ponds, 

multiple pond 

systems, 

“pocket” 

ponds 

— Removing accumulated 

sediment from main cells of 

pond once 50% of the 

original volume has been lost 

20-year cycle 

23
Section 2: Inspection and Maintenance of Existing Ponds and Wetlands 

Table 2.3: Maintenance Activities and Schedules 

Management Category Maintenance Activity Schedule Practice 

— Cleaning and removing 

debris after major storm 

events (>2” rainfall) 

— Harvesting of vegetation 

when a 50% reduction in the 

original open water surface 

area occurs 

— Repairing embankment and 

side slopes 

— Repairing control structure 

Annual or as 

needed 

— Removing accumulated 

sediment from forebays or 

sediment storage areas 

when 60% of the original 

volume has been lost 

5-year cycle 

Wetlands 

Shallow 

wetlands, 

pond 

wetlands, 

“pocket” 

wetlands 

— Removing accumulated 

sediment from main cells of 

pond once 50% of the 

original volume has been lost 

20-year cycle 

— Removing accumulated 

sediment from forebays or 

sediment storage areas when 

60% of the original volume 

has been lost 

5-year cycle 

Infiltration 

trench — Removing accumulated 

sediment from main cells of 

pond once 50% of the 

original volume has been lost 

20-year cycle 

— Cleaning and removing 

debris after major storm 

events; (>2” rainfall) 

— Mowing and maintenance of 

upland vegetated areas 

— Cleaning out sediment 

Annual or as 

needed 

Infiltration 

practices 

Infiltration 

basin — Removing accumulated 

sediment from forebays or 

sediment storage areas when 

50% of the original volume 

has been reduced 

3- to 5-year cycle 

Open 

channel 

practices 

Dry swales, 

grassed 

channels, 

biofilters 

— Mowing and litter/debris 

removal 

— Stabilizing eroded side 

slopes and bottom 

— Managing the use of 

nutrients and pesticides 

— Dethatching the bottom of the 

swale and removing 

thatching 

— Disking or aeration of swale 

bottom 

Annual or as 

needed 

24
Section 2: Inspection and Maintenance of Existing Ponds and Wetlands 

Table 2.3: Maintenance Activities and Schedules 

Management Category Maintenance Activity Schedule Practice 

— Scraping of swale bottom, 

and removal of sediment to 

restore original cross-section 

and infiltration rate 

— Seeding or installing sod to 

restore ground cover (use 

proper erosion and sediment 

control) 

5-year cycle 

— Removing trash and debris 

from control openings 

— Repairing leaks from the 

sedimentation chamber or 

deterioration of structural 

components 

— Removing the top few inches 

of sand, and cultivation of the 

surface, when filter bed is 

clogged 

Annual or as 

needed 

Sand filters — Cleaning out the 

accumulated sediment from 

filter bed chamber once 

depth exceeds approximately 

1⁄2 inch, or when the filter 

layer will no longer draw 

down within 24 hours 

— Cleaning out the 

accumulated sediment from 

sedimentation chamber once 

depth exceeds 12 inches 

3- to 5-year cycle 

— Repairing eroded areas 

— Mulching of void areas 

— Removing and replacing all 

dead and diseased 

vegetation 

— Watering of plant material 

Biannual or as 

needed 

Bioretention 

— Removing mulch and 

applying a new layer 

Annual 

Filtration 

practices 

Filter strips 

— Mowing and removing 

litter/debris 

— Managing the use of 

nutrients and pesticides 

— Aerating the soil on the filter 

strip 

— Repairing eroded or sparse 

grass areas 

Annual or as 

needed 

25
Section 2: Inspection and Maintenance of Existing Ponds and Wetlands 

26

Maintenance Activities 

Along with routine maintenance, specific activities for maintaining stormwater ponds and wetlands are 

detailed in the profile sheets in Section 3, which are organized by the top eight maintenance concerns 

introduced in Section 1. Each profile sheet provides the following: 

 Problems to Inspect For 

 Corrective Actions 

 Cautions and Safety Tips 

In addition, a subjective rating of skill level is presented with many of the maintenance activities to aid 

the program managers and responsible parties in understanding the severity of the problems described. 

Ratings and descriptions of the required skill levels can be found in Table 2.4 below. 

Table 2.4: BMP Maintenance Skill Level Descriptions

Skill Level Description 

0 No special skills are required but some basic training via manual, video, or 

other materials is necessary. 

1 Ordinary maintenance crew skill level. 

2 Contractor familiar with pond and wetland maintenance issues. 

3 Professional engineering consultant. 

Lastly, Appendix A provides useful unit cost information for specific maintenance activities along with 

typical maintenance frequencies to be expected. 
Section 2: Maintenance Activity Profile Sheets 

M-1 Permanent Pool 

Maintenance Activity Profile Sheets 

M-1 PERMANENT POOL.....................................................................................................................28

M-2 CLOGGING..................................................................................................................................31

M-3 PIPE REPAIRS.............................................................................................................................33

M-4 VEGETATION MANAGEMENT....................................................................................................38

M-5 DREDGING AND MUCK REMOVAL............................................................................................42

M-6 ACCESS .......................................................................................................................................45

M-7 MECHANICAL COMPONENTS ....................................................................................................47

M-8 NUISANCE ISSUES.......................................................................................................................50

27
Section 2: Maintenance Activity Profile Sheets 

M-1 Permanent Pool 

M-1 Permanent Pool 

Problems to Inspect For 

INSPECTION TIP: 

 

Stormwater ponds and wetlands 

often have higher than normal 

water surface elevations after 

storm events, sometimes for a 

number of days. This is a normal 

part of the design. Consider the 

last significant rainfall event when 

determining your inspection 

schedule. Try to avoid examining 

permanent pool levels within 2 to 3 

days of a significant rainstorm to 

give the facility time to discharge 

the runoff temporarily stored in the 

pond. Exceptions to this rule apply 

if vortexing or another problem that 

may be more apparent at higher 

stage is suspected. 

An important aspect of any pond or wetland inspection is having 

sufficient background information. In the absence of familiarity, a 

good set of as-built drawings can present a considerable amount 

of information about the way a pond was built and how it should 

function. Construction drawings or as-built drawings will include 

anticipated levels for permanent pools and sizes and locations of 

orifices. 

The best tool for confirming pool elevation fluctuation is 

familiarity. Abnormally high or low levels are more likely to be 

noticed in a pond that has been frequently inspected at normal 

levels. Signs that the permanent pool is too high include: 

 Water levels remain high for more than 2 or 3 days after a 

storm. 

 Pond edges normally visible are covered in water and 

plant species normally above permanent pool are now 

immersed in water. 

If a stormwater pond or wetland is well constructed, with an adequately sized and protected low flow 

orifice, it will only suffer from an abnormally high pool when outside forces act on it. Examples are 

clogging, vandalism (damaged riser or low flow valve being opened), or rodent activity. 

Signs that the permanent pool is too low include: 

 Stain marks on the riser or flow control structure. 

 Exposure of a non-vegetated pond bottom around the pool perimeter. 

To review a dam embankment for possible seepage, look at the color of the vegetation as well as changes 

in the plant species present and their density, particularly in dry weather. These changes may indicate 

seepage or leaking on the downstream dam face. Embankment leaks on the downstream side of a berm or 

dam are usually easily discovered if the vegetative cover has been recently mowed and the slope is not too 

steep (generally, 2H:1V or flatter). Leaks on the upstream dam face are usually impossible to locate 

visually, unless it is at the surface (such as a flooded animal burrow) or there is an active vortex. Slow 

leaks that are only apparent over long time periods are particularly difficult to observe and may require a 

dye test or complete pond dewatering. 

Often, inspections of stormwater ponds and wetlands falsely report leaks during warm weather when 

droughts or improper water budget analysis may be the problem. This latter scenario makes a pond prone 

to frequent lowered pools due to natural evaporation. 

28
Section 2: Maintenance Activity Profile Sheets 

M-1 Permanent Pool 

Conversely, larger facilities or facilities fed by constant inflow (surface streams, springs, or seeps) may 

have leaks or excessive seepage that is masked by the apparent normal permanent pool supported by a 

strong water source. Recorded measurements over time are the best way to confirm this problem. 

Corrective Actions 

Fixing the problems associated with permanent pool fluctuation can vary in difficulty, from relatively 

simple to complex and expensive. Regardless of the level of skill required for fixing the problem, only 

properly trained and authorized personnel should perform the maintenance. 

Table M1.1 includes a list of problems, potential solutions, a subjective analysis of problem classification, 

and an estimate of the skill level recommended to correct problems associated with permanent pool 

issues. Estimated costs to fix the types of problems outlined here are included in the Maintenance Cost / 

Frequency Table in Appendix A. 

Table M1.1: Permanent Pool Fluctuation Diagnoses

Finding Solution Classification Level of Skill 

Recommended 

Clogged low flow Clear low flow, install trash rack if not 

present or inadequate. See M-2 – Clogging. 

Minor 

maintenance 

(0) 

See cautions in 

M-2. 

Low flow or pond 

drain valve opened 

Shut valve and lock shut with chain and 

lock. See M-2 – Clogging. 

Minor 

maintenance 

(0) 

See cautions in 

M-2. 

Rodent activity 

(dams, lodges, 

burrows) 

Fill burrows. See M-8 – Nuisance Issues Minor to major 

repair (1) 

Leak in riser Seal leak. See M-3 – Pipe Repairs. Major repair (2) 

Leak in barrel Seal leak. See M-3 – Pipe Repairs. Major repair (2) 

Leak in upstream 

dam face or pond 

bottom 

Drain remainder of permanent pool and 

install waterproof liner; dye test 

recommended. 

Major repair (2) 

Leak or seepage in 

downstream dam 

face 

Dye test recommended; seal leak source if 

found; liner may need to be installed and 

dam or principal spillway repair or 

replacement may be required depending on 

leak severity. 

Major repair (3) 

Vortexing1

Consider a call to civil authorities 

immediately as dam failure may be 

imminent and down stream evacuation may 

be necessary; do not attempt to repair 

without professional help. 

Usually major 

repair (3) 

Inspection frequency beyond typical annual inspection should be set by the pond or wetland maintenance 

history and/or its use. For example, ponds with chronic clogging due to beaver activity should be put on a 

more frequent inspection schedule. 

 

1

 Swirling action of water caused by submerged orifice flow, usually in the vicinity of the dam, riser or 

principal spillway. 

29
Section 2: Maintenance Activity Profile Sheets 

M-1 Permanent Pool 

30

Cautions and Safety Tips 

Risers near the shore or located in the embankment are 

often easy to examine from the surface (See Figure 

M1.1). Normal personal protection equipment (PPE) as 

defined by the U.S. Occupational Safety and Health 

Administration (OSHA) is sufficient to view from the 

top and photograph and/or measure with a drop tape. 

Risers located out in the permanent pool, or those with 

inaccessible tops (such as the typical round anti-vortex 

shell CMP riser) are more difficult and may require 

confined space entry and/or boat access. Similarly, 

barrels may require confined space entry to examine 

for leaks or to gain access to the riser itself; some 

barrels are too small for entry or are damaged or 

clogged. In these situations, remote TV inspection 

from either or both ends may be the only practical way 

to examine for leaks. However, if a leak in a riser or 

barrel is large and obvious, it may be easy to spot, 

particularly if it is a hole in a metal riser that now acts 

as a “low flow orifice”. 

Figure M1.1: Riser located near pool edge for 

easier access. 
Section 2: Maintenance Activity Profile Sheets 

M-2 Clogging 

M-2 Clogging 

Problems to Inspect For 

External clogging can easily be identified through 

routine visual inspection. Clogging within low flow 

pipes and underdrains can be more difficult to find. A 

well functioning opening and trash rack should be 

clear of debris. Trash racks should show little or no 

corrosion and should be completely visible. Examine 

design or as-built records to determine which 

weir/orifice is supposed to set the permanent pool. 

Figure M2.1: Clogged valve. 

Record water surface elevations by leaving a stake or 

marker at a high water mark and recheck at regular 

intervals to determine if pond or wetland permanent 

pool levels are staying higher than designed for 

longer periods than expected following a rainfall 

event (see Profile Sheet M-1). If pool levels are 

higher than expected for long durations, then a 

clogged low flow pipe or orifice, or internal clogging 

of a low flow drain may be the problem. 

 

Corrective Actions 

Trash and debris removal should occur during the 

regularly scheduled inspection and maintenance to 

reduce the chance of outlet structures, trash racks, 

and other components becoming clogged and 

inoperable during storm events. Proper preventative 

maintenance includes removal of debris from pond 

bottoms, embankments and side slopes, perimeter 

areas, and access areas that can lead to clogging, as 

well as debris jams at outlet structures and trash

racks. 

Figure M2.2: Clogged low flow orifice 

(before maintenance). 

Metal trash racks should be inspected, and any 

exposed steel should be brushed free of corrosion and

coated or spray coated with protectant or water 

sealant. 

31
Section 2: Maintenance Activity Profile Sheets 

M-2 Clogging 

32

Techniques for removing clogs depend on the accessibility and severity of the clog. They include: 

 Manual removal of debris by hand or by machine 

 Jetting, back flushing, or routing a clogged pipe. High velocity spray and hydraulic head pressure 

devices include high velocity jet cleaners, cleaning balls, and hinged disc cleaners. 

 Sediment or muck removal around the low flow structure, to locate the opening and return it to 

design conditions. (See M-5 – Dredging and Muck Removal) 

 A professional diver may be needed for deeply clogged facilities. 

 Dewatering of facility via pumping or other means to reveal the source of clogging and allow 

access (if regulatory laws permit). 

 

Disposal of debris and trash must comply with all local, county, state, and federal waste regulations. 

Only suitable disposal and recycling sites should be utilized. 

 

Cautions and Safety Tips 

Clearing clogged openings may be easy or difficult 

depending on access to the opening. If removing an 

obstruction or clog seems like it might be unsafe, it 

probably is - leave it to a qualified contractor. 

Clogged openings can cause dangerous headwater 

conditions behind the blocked orifice. In addition to the 

normal hazards associated with low flow maintenance 

(confined space entry, poor footing, and potential for 

sharp objects including syringes and glass), strong flow 

can be generated instantaneously. 

If a facility has had deep backwater for a long period of 

time, sudden de-clogging may actually cause damage 

due to the slumping of un-vegetated, waterlogged slopes. Further, the downstream receiving swale, storm

drain or stream may not be stable enough to withstand the instantaneous release of water. The released 

water will probably be silt-laden, releasing a large amount of sediment, nutrients and possibly toxics. 

Employ a professional to conduct slow, safe draw-down and to remove any muck as required. 

Figure M2.3: After clog is removed. 

OSHA approved personal protection equipment will be needed and confined space entry may be required. 

See M-6 Access for additional riser and manhole access concerns. 
Section 2: Maintenance Activity Profile Sheets 

M-3 Pipe Repairs 

M-3 Pipe Repairs 

Problems to Inspect For 

Pipes are the most challenging feature of ponds and wetlands to thoroughly inspect. Repairs are often 

expensive and require specialized equipment. Table M3.1 presents a summary of maintenance concerns 

typical for different pipe materials. Following Table M3.1 are a number of inspection tips to inform an 

inspector or lay person about things to look for with respect to pipes when inspecting stormwater ponds 

and wetlands: 

Table M3.1: Common Pipe Uses, Material, and Maintenance Concerns

Use Most Common Material Typical Maintenance Concerns 

Principal spillway or barrel CSP and RCP Scour damage, leaking joints, 

misaligned joints 

Under drains, internal drains PVC, HDPE and Clay Filter media failure, crushing 

Inlets RCP and CSP Blockages, frost heave, undercutting 

Hydraulic control All types Clogging, corrosion, vandalism 

Quantity control CSP 

Construction rips and tears, 

misalignments and non-soil-tight 

joints 

Notes: 

CSP – corrugated steel pipe; RCP – reinforced concrete pipe; PVC - polyvinyl chloride pipe; HDPE 

– high density polyethylene pipe 

Figure M3.1: Improper pipe 

joint but rubber seal is visible. 

Joint Tightness: All pipe sections should abut evenly with little or 

no gap. In particular, no barrel should leak. Barrel pipes for 

ponds should not pass soil or water. Corrugated steel pipe (CSP) 

joints should meet smoothly, be free of rough or jagged edges, 

and have a butyl rubber seal surrounding the outside of the joint 

(Figure M3.1). The seal should not be torn, dry-rotted or bulging. 

CSP joints are not expected to be watertight (only soil tight1

) 

except when used as principal spillways. Figure M3.2 illustrates a 

joint that is neither soil nor watertight. 

Concrete bell and spigot pipe joints may have a gap up to the 

allowable dimension as described by local ordinance or as 

determined by the manufacturer. Joints are usually parged with 

high strength non-shrink grout, but this does not guarantee water 

 

1

 Soil tight means that pipe joints can pass water but they do not allow soil intrusion. 

33
Section 2: Maintenance Activity Profile Sheets 

M-3 Pipe Repairs 

tightness. The tongue and groove end sections of 

individual pipe sections should be free from damage, 

especially damage that exposes the underlying reenforcing steel. 

Plastic and clay piping are used in small diameter 

applications such as underdrains and splitter pipes. 

high density polyethylene pipe (HDPE) piping is 

usually installed in long sections without joints but 

polyvinyl chloride pipe (PVC) is usually installed with 

a rubber-coated bell and spigot connections similar to 

reinforced concrete pipe (RCP). The use of clay pipes 

for the principal spillway is discouraged as clay joints 

are not watertight. 

Misalignment: One of the most common causes for 

repair is pipe misalignment (Figure M3.3). 

Misalignment is often apparent at or shortly after construction. Otherwise, alignment changes occur due 

to differential settlement, freeze-thaw cycles, or dynamic loads such as traffic. 

Figure M3.2: Soil entering open pipe joint. 

Figure M3.3: Misalignment in RCP (left and right) and CSP (center) applications. 

Pitting and corrosion: Unprotected CSP usually has a relatively long design life on its soil side but is very 

susceptible to erosive scour, pitting and corrosion on its flow side, particularly along the invert of the 

pipe. Pitting is highly localized corrosion causing perforations large enough to infiltrate or exfiltrate 

water. Soil side design life often exceeds 50 years, but flow side design life is usually between 20 and 35 

years before the first pitting appears. CSP manufacturers coat piping with various substances to lengthen 

design life such as bituminous asphalt, aluminum, or concrete poured along the invert of the pipe. 

Staining and Calcification: Rust 

stains inside RCP often indicate that 

acidic groundwater is leaching in 

through a crack or hole, slowly 

dissolving the steel rebar and 

precipitating it back into a form of 

ferrous oxide on the inside of the pipe 

(Figure M3.4). Once the anaerobic 

water comes in contact with the 

oxygen within the pipe interior the 

reaction occurs. These stains usually 

indicate that repairs should be made 

Figure M3.4: Rust intrusion 

demonstrates improper 

pipe joint. 

Figure M3.5: Calcification.. 

34
Section 2: Maintenance Activity Profile Sheets 

M-3 Pipe Repairs 

to the pipe to stop the water from infiltrating the pipe. 

Calcification occurs when acidic water enters concrete cracks from the inside of the pipe, dissolving and 

reconstituting the hydrated Portland cement in the RCP (Figure M3.5). Calcification may or may not 

mean that a crack has breached the entire thickness of the pipe and adequate experience is necessary to 

determine when repairs are truly necessary. 

Root Intrusion: Root intrusion into pipe systems is an especially difficult and damaging phenomenon but 

fortunately is relatively easy to observe. Roots typically enter loose pipe joints and can cause clogging by 

snagging debris. Willows (Salix sp.) are notorious for root intrusion. 

By following the described pipe inspection tips above, the lay person or inspector can better understand 

the types of problems likely to be encountered during stormwater pond and wetland maintenance 

inspection. Once experience is gained in performing inspections, inspectors can foresee potential 

problems and plan preventive maintenance. 

Corrective Actions 

Fixing pipe problems can be approached from two directions: repair or replacement. Different methods 

for pipe repair and replacement are presented below, as well as a recommended skill level. All involve the 

need for professional contractor or engineer assistance. Consult an engineer to determine the most 

appropriate technique. 

Common pipe repair methods include: 

• Joint Sealing: In the injection grouting method, RCP leaking joints and concrete cracks can be sealed 

with high strength non-shrink grout or epoxy. Holes are drilled all the way through the pipe to the 

soil beyond. The grout is injected to the other side where it reacts with groundwater and hardens. This 

method is often used for difficult access areas such as a buried concrete pipe barrel joints. OSHA 

confined space entry training may be required. CSP joints are similarly sealed, except polyurethane 

foam water stop material is injected. Recommended skill level (3). 

• Another joint sealing method utilizes an inflatable packer inserted into a pipeline to span a leaking 

joint. Resin or grout is then injected into cracks and cavities until the joint is sealed, after which the 

packer is removed. This localized repair of pipes prevents leakage and further deterioration and may 

increase the structural strength of the pipeline. Recommended skill level (3). 

• Invert Protection: This method involves protecting the lower segment of a corrugated metal pipe by 

lining it with a smooth bituminous or concrete material that completely fills the corrugations. This 

approach is intended to give resistance to scour/erosion and to improve flow. Recommended skill 

level (2). 

• Chemical Stabilization: Chemical stabilization involves isolating a length of pipeline between two 

access points by sealing the access points. One or more compounds in solution are introduced into the 

pipe, and the surrounding ground produces a chemical reaction that forms a stable protective coating 

over cracks and cavities. Recommended skill level (3). 

Pipe rehabilitation typically involves more intensive and comprehensive correction of pipe problems 

aimed at restoring or upgrading the performance of an existing pipe system. Often, rehabilitation is 

35
Section 2: Maintenance Activity Profile Sheets 

M-3 Pipe Repairs 

needed when there is major structural and/or hydraulic weakness. Common pipe rehabilitation methods, 

all involving the need for professional contractor or engineer assistance, include: 

• Folded Liners: A PVC or HDPE liner is folded to reduce its cross sectional area. The liner is pulled 

into a failing pipe system and reverted to its original size using pressure and heat to form a tight fit 

with the host pipe wall. Recommended skill level (3). 

• Cured-in-place pipe (CIPP): CIPP is a thin flexible tube of polymer or glass fiber fabric that is 

impregnated with thermoset resin and expanded by means of fluid pressure onto the inner wall of a 

defective pipeline before curing the resin to harden the material. Recommended skill level (3). 

• Ferro-cement: Steel fabric mesh, usually in multiple layers, is fixed to the existing pipe, then covered 

in high strength grout. It is either placed in situ to form a structural lining (in large diameter pipes 

with human access) or pre-formed into segments for later installation. Recommended skill level (3). 

• Pipe bursting: Also known as in-line expansion, this is a method by which the existing pipe is 

demolished and a new pipe is installed in its void. Recommended skill level (3). 

• Pipe eating: A pipe replacement technique usually based on micro tunneling to excavate defective 

pipe with the surrounding soil as for a new installation. Recommended skill level (3). 

• Pipe pulling: Method of replacing small diameter pipes where a new product pipe is attached to the 

existing pipe which is then pulled out of the ground. Recommended skill level (3). 

• Slip-lining: Insertion of a new pipe by pulling or pushing it into the existing pipe and grouting the 

annular space. The new pipe may be continuous or a string of discrete pipe sections. The latter is also 

referred to as segmental slip-lining. Recommended skill level (3). 

• Modified slip-lining: A range of techniques in which the liner is reduced in diameter before insertion 

into the carrier pipe, then restored to its original diameter, forming a close fit with the original pipe. 

Recommended skill level (3). 

• Spray lining: A technique for applying a lining of cement mortar or resin by rotating a spray head, 

which is winched through the existing pipeline. Recommended skill level (3). 

36
Section 2: Maintenance Activity Profile Sheets 

M-3 Pipe Repairs 

37

Table M3.2 summarizes the limitations of the different types of pipe rehabilitation methods mentioned 

above. 

Table M3.2: Limitations of common pipe rehabilitation methods 

Method Limitations 

CIPP 

• Bypass or diversion of flow required 

• Curing can be difficult for long pipe segments 

• Must allow adequate curing time 

• Defective installation may be difficult to rectify 

• Resin may clump together on bottom of pipe 

• Reduces pipe diameter 

Pipe bursting 

• Bypass or diversion of flow required 

• Insertion pit required 

• Percussive action can cause significant ground movement 

• May not be suitable for all materials 

Slip-lining 

• Insertion pit required 

• Reduces pipe diameter 

• Not well suited for small diameter pipes 

Modified Slip-lining 

• Bypass or diversion of flow required 

• Cross section may shrink or unfold after expansion 

• Reduces pipe diameter 

• Infiltration may occur between liner and host pipe unless sealed 

• Liner may not provide adequate structural support 

Cautions and Safety Tips 

Most stormwater pond and wetland pipe work can be visually inspected from a daylighted end or manhole 

access. However, some piping is difficult to inspect due to being buried, flooded, cramped, or 

deteriorated. In this case, inspection work should be left to qualified professionals who are versed in 

confined space entry and exit as defined and regulated by state and federal OSHA standards. Some piping 

is impossible to inspect manually (such as a 6-inch underdrain), and remote TV video inspection or 

complete unearthing are the only options. 
Section 2: Maintenance Activity Profile Sheets 

M-4 Vegetation Management 

M-4 Vegetation Management 

Problems to Inspect For 

Vegetation management is the most frequent type of maintenance conducted on stormwater ponds and 

wetlands. In most instances, vegetation management is straightforward and does not require special 

expertise or equipment. However, if facilities have gone long periods of time without proper vegetation 

maintenance, then the level of effort and complexity of the activity can become significant. 

Telltale signs of vegetative problems include the following: 

 Standing water and emergent plant growth 

where none should be present 

 Monoculture vegetation in wetland 

 Poor or spotty grass growth or completely bare 

areas (Figure M4.1) 

 Soggy surfaces 

 Excessive sedimentation at pond inlets or 

outfalls with corresponding emergent plant 

growth (Figure M4.2) 

 Limited visibility or access to the principal 

spillway or embankment areas due to vegetation 

 Deep-rooted woody vegetation (trees and 

shrubs) on any areas of a dam 

 Woody vegetation growing in riprap on slope 

areas meant for erosion protection Figure M4.1: Bare soils on embankment 

and slopes.  Signs of seepage around any tree stumps or 

decaying root systems on embankment areas 

 Changes in vegetative color, species or height 

due to possible groundwater or seepage 

problems 

 Areas where local residents have been dumping 

yard waste 

 Pond embankments with newly planted 

ornamental trees or shrubs not originally 

included in the design 

 Damaged or torn erosion control matting (ECM)

 Ruts or erosion channels in vegetated swales or 

level spillways 

 Tree or shrub growth in or around major pond 

appurtenances such as the principal spillway 

Figure M4.2: Excessive vegetation near an 

outfall. 

38
Section 2: Maintenance Activity Profile Sheets 

M-4 Vegetation Management 

Corrective Actions 

The following describe specific activities associated with maintaining the vegetation in and around 

stormwater ponds and wetlands as well as the recommended skill level of the person performing the 

maintenance in parentheses (reference Table 2.4): 

Grass and Turf 

Figure M4.3: Representative mowing for wetland. 

Consistent mowing and monitoring should control 

any unwanted vegetation. Typical mowing areas 

include pond bottoms (dry ponds), embankments, 

side slopes, perimeter areas, and access areas (Figure 

M4.3). The actual mowing requirements of an area 

should be tailored to the specific condition and grass 

type. Other actions to maintain grassed areas include 

de-thatching, soil conditioning, re-seeding, and 

periodic fertilization as necessary. 

Most grass is hardiest when maintained as an upland 

meadow, cut no shorter than 6 to 8 inches. If a more 

manicured look is desired, special attention to the 

health of the turf is needed. Grass should not be cut 

below 4 inches. Typical mowing schedules for grass 

on embankments are at least twice during both the 

spring and fall growing seasons and once during the 

summer. Recommended skill level (0). 

Vegetated Buffer 

A 10-foot unmowed vegetated buffer around the 

perimeter of the pond or wetland (exclusive of the 

dam embankment) may be established to filter 

pollutants from adjacent properties and help prevent 

shoreline erosion (Figure M4.4). Areas set aside for 

pond access such as fishing can be secured with 

stone, timber wall or one of many commercially 

available plastic retaining wall products. 

Recommended skill level (0). 

Vegetation Harvesting 

In stormwater wetlands, vegetation harvesting1 may 

be required. To perform wetland harvesting, selected 

plant materials are tagged for removal by a qualified 

professional, then cut and hauled to a disposal location. Recommended skill level (1 - 2). 

Figure M4.4: Vegetated buffer. 

 

1

 Vegetation harvesting is removing vegetation on a routine basis and land applying it in an upland 

location. The purpose for vegetation harvesting is to remove plant material before winter die-off to 

prevent nutrients from reentering the water column and being flushed downstream. 

39
Section 2: Maintenance Activity Profile Sheets 

M-4 Vegetation Management 

Bare areas 

Vegetation can be established by any of five methods: mulching; allowing volunteer vegetation to become 

established; planting nursery vegetation; planting underground dormant parts of a plant; and seeding. 

Seeding can come in the form of broad-cast seeding, hydro-seeding or sodding. Donor soils from existing 

wetlands can be used to establish vegetation within a wetland. If the soil has become compacted, it will 

require aeration. Areas without grass or vegetation should be vigorously raked, backfilled if needed, and 

covered with topsoil. Disturbed areas should be seeded and mulched if necessary. A tall fescue grass seed 

is often recommended; however consult the local Natural Resources Conservation Service (NRCS) office 

for the best native mixes for the project location. Recommended skill level (0). 

Bare or monoculture stormwater pond and wetland slopes and bottoms offer the best opportunities to 

enhance areas with native trees, shrubs, and groundcovers to help the water soak into the ground. Select 

species that need little fertilizer or pest control and are adapted to specific site conditions. Again, contact 

your local NRCS office for guidance. 

Figure M4.5: Unwanted vegetation - tree 

on embankment. 

Unwanted vegetation 

Some vegetation, such as that on embankments (Figure 

M4.5), requires complete removal, including root 

masses, to ensure that it does not return; this is often 

best done with landscaping Brush HogsTM or small 

earthmoving equipment. Stump removal may also 

require tractor and chain. The removal of large trees 

may require the skills of a professional arborist. The 

use of herbicides should be avoided; however if 

deemed necessary, they must be applied by a statelicensed herbicide applicator. Recommended skill 

level range (0 - 2). 

Root removal 

Roots should be removed in the designated sections where root intrusion is a problem. To remove roots 

from a pipe, use mechanical devices such as rodding machines, bucket machines, and winches using root 

cutters and ‘porcupines’ or equipment such as high-velocity jet cleaners. Chemical root treatment is 

available but discouraged and herbicides must be applied by licensed applicators. 

Roots should be removed from the embankment to prevent their decomposition within the embankment. 

Excavate to remove roots, then plug or cap root voids. Recommended skill level (2). 

Dumping areas 

Grass clippings, leaves, soil and trash are often dumped directly into storm drain inlets or stormwater 

ponds and wetlands. Any of these items can lead to clogging, and leaves and grass clippings release 

bacteria, oxygen consuming materials, and nutrients. Removal is easy assuming a suitable disposal area or 

trash pickup location is available. Posting signage explaining the importance of not dumping will help 

dissuade the good intentioned. Signage may also advise natural lawn care to minimize the use of 

chemicals and pesticides. Recommended skill level (0). 

Inadequate drainage slopes 

To promote proper conveyance and to prevent standing water, conveyances to and from ponds and 

wetlands should have a minimum slope of one to two percent. Inadequate slopes typically result in the 

conveyances filling with sediment and vegetation (Figure M4.6). Removal of muck and vegetation from 

40
Section 2: Maintenance Activity Profile Sheets 

M-4 Vegetation Management 

41

conveyances can be accomplished with small equipment. See Section M-5 – Dredging and Muck 

Removal. Recommended skill level range (1 - 2). 

Figure M4.6: Vegetation establishment 

where the inflow channel slope is 

inadequate to drain properly. 

Cautions and Safety Tips 

Although the removal of unwanted vegetation is not a professional skill, it is not without hazards. 

Possible hazards include cuts and scrapes from the brambles and thorns of species such as Multiflora 

Rose (Rosa multiflora) and Tear Thumb (Polygonum perfoliatum). Overgrown vegetation can also 

obscure ledges, burrows, drop-offs, stumps, and wasp nests. 
Section 2: Maintenance Activity Profile Sheets 

M-5 Dredging and Muck Removal 

M-5 Dredging and Muck Removal

Problems to Inspect For 

The need for dredging may be indicated by sediment 

plumes or deltas at storm drain inlets that feed 

stormwater ponds and wetlands, as most sediment falls 

to the pond floor quickly and within a short distance 

from storm drain inflow points (Figure M5.1). 

Alternatively, accumulated sediment can be measured 

through use of 1 a staff gauge . 

t 

ater 

ve 

dredged for aesthetic value. 

 

The best way to determine if a pond or wetland needs 

dredging is to perform a bathymetric study, which 

involves taking field measurements to calculate the 

volume of water within a pond or lake. The survey is 

similar to a topographic measurement of the contours 

below the permanent pool surface of a pond. The end 

result of the survey is a two-dimensional map indicating 

depth contours at all locations within the permanent pool. Bathymetric surveys indicate the amount of sil

or muck that has accumulated within a pond or lake; consequently, estimates of remaining stormw

pond life, dredging volumes and associated costs can be made. A pond that appears full may still ha

adequate volume for settling suspended solids and for meeting stormwater management design criteria 

purposes, yet the owner may wish to have the pond 

Figure M5.1 Sediment delta.

Bathymetric surveys require use of level rods, electric 

distance measurement equipment (EDM), small 

watercraft, sediment probes or depth finders to gather 

pond depth information (Figure M5.2). Usually a staff 

person measures the pond depth while in a canoe or 

johnboat. On shore, another staff uses EDM equipment to 

determine distance and azimuth (angle) measurements to 

the test location. Existing volume measurements can be 

compared against design volumes to determine the 

amount of muck requiring removal (Figure M5.3). If no 

previous design records exist, the procedure is basically 

the same, but additional sediment depth probing must be 

done to measure muck levels. 

Figure M5.2: Measuring pond depth from 

canoe. 

1

 A staff gauge is a fixed marker rod that enables easy reading of sediment levels in a pond once the pond 

has been drained. 

42
Section 2: Maintenance Activity Profile Sheets 

M-5 Dredging and Muck Removal 

BATHYMETRIC STORAGE CURVE

118

120

122

124

126

128

130

132

0 500 1000 1500 2000 2500

storage in cubic yards

water surface elevation 

(MSL)

design storage bathymetric storage

Figure M5.3: Plot of elevation vs. storage for existing and design conditions. 

Dredging needs for dry ponds are easier to identify. There may be a profusion of vegetation, particularly 

wetland species, at the bottom of the facility. Pilot channels may disappear due to the accumulation of 

sediment and trash. An obvious sign for quick action is a buried low flow opening. Sediment in a dry 

pond can also be measured with a preset staff gauge; but hand-taped or simple field surveys can also 

suffice. 

Corrective Actions 

In smaller ponds and wetlands, the pond water may 

be drawn down to a point where the residuals can

begin to dry in place. After the material is dried, 

heavy equipment can remove the sediment from the 

bottom of the pond, a process referred to as 

mechanical dredging. Mechanical dredging may be 

accomplished with a standard or long reach 

backhoe, front end loader, dipper, bucket dredge, 

drag line or clamshell dredge (Figure M5.4). Care 

should be taken to minimize soil compaction around 

the pond or wetland that can be caused by the heavy 

machinery. 

Where dredging cannot be accomplished 

mechanically from the shore, it may be necessary to 

remove sediment using hydraulic dredging 

methods2

. Larger ponds that cannot be drained are 

Figure M5.4: Mechanical dredging with 

backhoe. 

 

2

 Hydraulic dredging uses a combination of water jet and vacuum to resuspend settled material and pump 

it to an upland location or other place for dewatering. 

43
Section 2: Maintenance Activity Profile Sheets 

M-5 Dredging and Muck Removal 

44

WETLAND DREDGING TIP: 

 

Maintenance dredging of a 

stormwater wetland can 

significantly damage the 

wetland community that has 

developed over the life of the 

practice, and may be met with 

resistance from regulators 

and adjacent property 

owners. Typically, if a wetland 

was constructed specifically 

for stormwater treatment and 

not as mitigation for other 

wetland impacts, owners can 

maintain them without 

permits. However, permitting 

authorities that have 

jurisdiction over the site 

should be informed prior to 

disturbing any wetland area 

for maintenance or other 

purposes. 

If a diverse native wetland 

plant community is present in 

a stormwater wetland, for 

maintenance purposes it may 

be advisable to scrape and 

stockpile the surface soil 

layer in a designated location 

for future reapplication. The 

surface layer may contain a 

variety of seeds thatcan be 

reapplied to help the wetland 

plant material reestablish 

after the excess sediment has 

been removed. If a non-native 

or invasive wetland plant 

community has been 

established, conduct removal 

with care or during a dormant 

season to discourage seed 

distribution. 

often de-mucked via hydraulic suction or with the use of draglines 

operated from barges. In ponds not large enough to warrant hydraulic 

dredging, mechanical dredge methods are used and removed material 

is de-watered to minimize trucking requirements and potential 

spilling. 

Sediments from ponds and wetlands are usually dewatered and then 

disposed of onsite or land filled. It is typical to spread this material 

out on a site for use as a soil amendment. Onsite disposal usually 

entails digging a pit, wasting the muck material, covering the pit with 

previously removed topsoil and planting the appropriate native 

plantings. Once a dredge area disposal site is established, it cannot be 

used for structural support or building foundations as long-term 

settlement will occur. 

If on-site storage is not specified, sediment can typically be landfilled. 

Wet sediment is not accepted at many disposal sites; therefore, the 

material must be dewatered prior to disposal. This extra step adds to 

the cost and requires a location where wet material can be temporarily 

and safely placed to dry. 

If the practice drains a stormwater hotspot, such as a gas station, a 

Toxic Contaminant Leachate Procedure (TCLP) or other analytical 

analysis should be performed in accordance with receiving landfill 

requirements to determine if the removed sediment should be 

considered a hazardous waste. If the residual solids are determined to 

be hazardous, they must be managed according to Resource 

Conservation and Recovery Act of 1976 (RCRA), which requires 

either treatment to decrease the concentration of the hazardous 

constituent or disposal in a hazardous waste landfill. 

Cautions and Safety Tips 

Dredging and muck removal involve additional costs and safety 

considerations including proper disposal, confined space work, 

permitting and utility damage. This work is best left to general 

contractors and specialty maintenance companies with adequate 

training and bonding. The recommended skill level range for all 

dredging issues is (3)
Section 2: Maintenance Activity Profile Sheets 

M-6 Access 

M-6 Access

Problems to Inspect For 

Inadequate access is typically discovered by inspectors or 

maintenance contractors who cannot enter a site or 

particular site features (e.g. risers). Inspectors should be 

cognizant of the types of equipment needed to maintain a 

stormwater pond or wetland, so they can note potential 

access issues (Figure M6.1). If potential access issues are 

noted up front, the maintenance contractor can be warned 

and can plan accordingly. 

Risers and manhole access can be particularly 

challenging and dangerous, particularly when access 

steps are missing (Figure M6.2) or no manhole access has 

been provided. In these cases, it is necessary to lower 

staff by winch once the atmosphere has been tested. 

Therefore, mandatory fall protection should be used when 

accessing risers or manholes. 

Figure M6.1: Poor vehicle access.

If no manhole access is provided and water enters a riser 

through weirs or orifices that are too small to allow direct 

access, the riser may still be entered safely through the 

barrel (principal spillway) under certain conditions. In 

Howard and Montgomery Counties, Maryland, safe barrel 

access is defined by the following conditions: 

 Access is conducted by qualified confined space 

entry-trained staff (team of two with proper 

equipment). Figure M6.2: Missing manhole step. 

 The barrel is open to daylight at both ends and no 

atmospheric dangers are present. 

 The diameter of the barrel is 36 inches or greater. 

 There is little to no tailwater making access 

unsafe, defined as blocking more than a third of 

the opening (Figure M6.3). 

Given these conditions, the barrel may be crawled. 

Verbal contact should be kept with the crawler at all 

times. Each joint may be examined by hand for leaks and 

discontinuities. The inspector may enter the riser to 

inspect it once he or she has traversed the barrel. 

Figure M6.3: Forced access location. 

45
Section 2: Maintenance Activity Profile Sheets 

M-6 Access 

46

Corrective Actions 

Many access issues are best addressed during the design 

of ponds and wetlands. However, there are routine 

maintenance activities that will also be required. Most 

notably, it is important and advisable to maintain primary 

access features as they were designed. This typically 

involves removal of woody vegetation from access roads 

and the upkeep of gravel areas. Risers with missing steps, 

manhole covers, or trash racks that present unsafe 

situations should also be repaired so that future access for 

inspection is not compromised. 

In some cases, where major work needs to be performed, 

temporary construction access for large, heavy equipment 

will need to be provided. In these situations, special 

provisions should be taken to minimize impacts to 

adjacent areas, particularly if they are forested. Common 

tree protection measures include fencing that is 

sufficiently set off to provide protection of the critical 

root zone and protective sheathing (Figure M6.4). 

Figure M6.4: Tree scar protection. 

Heavy vehicle access can also impact areas with paving, 

curbs, and decking (Figure M6.5). It may also compact 

unpaved soil. For the mutual protection of both the owner 

and contractor, these access points should be clearly 

marked or flagged and then photographed prior to 

equipment arrival onsite. Temporary pavement protection 

devices include: 

Figure M6.5: Paved access road.  Steel sheeting 

 Timbering and mats 

 Stabilized stone and gravel construction accesses and mountable berms 

 Unloading and ‘walking’ equipment in on rubber tires 

If a fenced pond or wetland does not have vehicle gates large enough to accommodate heavy equipment, 

sections of fence will need to be temporarily removed to allow access. 

Cautions and Safety Tips 

Mandatory fall protection should be used when accessing risers or manholes. Risers and manholes may be 

missing access steps, and lowering staff by winch may be required once the atmosphere has been tested. 
Section 2: Maintenance Activity Profile Sheets 

M-7 Mechanical Components 

M-7 Mechanical Components

Problems to Inspect For 

Early identification of problems and speedy repair is important to ensure the maximum design life of 

mechanical components, most of which are metal. Signs of common mechanical failures include: 

 Loose trash rack pieces 

 Rust and corrosion 

 Original lift lugs still in place for pre cast concrete structures 

 Nicks and cuts in protective coatings 

 Loose or corroded bolts 

 Form nails and ties still present for cast-in-place concrete structures 

 Leaking valves 

 Corroded locks 

 Hand wheels that won’t turn 

 Missing tools necessary for valve maintenance 

 Pock marks 

 Standing water 

 Flaking 

Corrective Actions 

Although most mechanical component maintenance is 

straightforward, it is usually out of the range of normal services 

provided by landscaping staff. Therefore, repairing and replacing 

these components should be left up to general contractors. For 

mechanical component problems external to confined spaces 

(Figure M7.1), the recommended maintenance skill level would 

be (1). For mechanical components in confined spaces, the 

recommended maintenance skill level would be (2). 

Valves 

Appurtenances with moving parts, especially valves, require 

annual exercising and lubrication. Most valves are hand-wheel 

valves that take several turns to completely open (often over 

thirty turns); however, exercising or temporarily opening a valve 

does not necessarily involve opening it completely. Staff need 

only rotate the wheel enough times to make sure the metal gate 

moves up and down. This procedure may involve two or three 

wheel rotations and a small amount of water may be released. 

After the valve is exercised, the staff should slowly close the 

valve, making sure the gate properly re-seats to a watertight 

closure position or to the appropriate opening dimension. If a valve gate won’t move, it may need to be 

serviced or replaced. If the valve won’t close after being opened a few turns, it will also need service. 

Figure M7.1: Valve outside 

riser. 

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Section 2: Maintenance Activity Profile Sheets 

M-7 Mechanical Components 

Valve service typically means applying lubrication. Lubrication involves greasing the valve corkscrew 

stem and should only be done once it is determined that the valve will safely close again. Water will be 

released during this 5 to 15 minute operation as most valves must be completely open during lubrication. 

Most valves draw water from, at, or near the pond bottom where sediment accumulates. Avoid the quick 

opening of valves as water released will be turbid and sediment will be introduced to downstream 

receiving areas. Open the valve slowly and allow the conditions at the permanent pool end to stabilize 

prior to complete opening. 

Extended length and non-hand wheel valves 

Some valves are installed with extended stems to allow safer opening from well-above the actual valve 

itself. Some valve types do not have hand wheels and are more vandal-resistant but require either a cog or 

‘T’ key to open. The key may or may not be present in the riser box. If it is, it should be securely stored in 

a place where it cannot be removed and preferably as far removed from running water as possible. If the 

key is stored off-site, this may pose a problem if the pond needs to be dewatered in an emergency. 

Rust-proofing 

Although some plastic, aluminum, or PVC appurtenances are available, most mechanical components are 

galvanized metal. Metal oxidization is an inherent maintenance concern in stormwater pond and wetland 

environments. Therefore, several methods of rust protection should be employed including painting with 

zinc-rich or galvanizing paint, coating with bituminous tar or rubber and using stainless steel. Water 

chemistry, temperature extremes, clogging, and vandalism will speed oxidization. 

Repair work usually involves the removal of all rust with a wire brush to expose clean metal, if still 

present. Exposed metal is painted with a rust-proofing agent. Metal that has rusted through should be 

patch welded or replaced. 

Securing bolts 

Usually the bolts securing the metal to a concrete wall are the weakest metal components. An understrength or under-protected bolt may meet temperature and shear stress extremes, as well as the concrete 

chemistry or other potential chemical attack. Often, bolts securing a trash rack or orifice plate fail long 

before the appurtenance fails. Once bolts have rusted through, they must be replaced. Usually the original 

drill hole has been compromised and a new drill hole must be made. 

Figure M7.2: Surface aerator / fountain. 

Aerators 

Aerators will be wired to an outside electricity source 

and they will most likely have an air hose running out 

to the underwater diffuser head (Figure M7.2). Both 

types of lines (electrical and air) should be inspected 

for kinks, exposed wire, and dry rot and replaced as 

necessary. 

Ponds having bubblers, aerators, fountains or diffusers 

may require specialty contractors or manufacturer 

representatives for repairing severe maintenance 

problems. Pump clogging, air hose deterioration or 

diffuser head clogging may be simple repair items, but 

an assessment of the difficulty must be made prior to 

making a judgment call about who is suited to perform 

the maintenance activity. 

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Section 2: Maintenance Activity Profile Sheets 

M-7 Mechanical Components 

49

Cautions and Safety Tips 

The opening of valves is an inherently risky procedure, especially when in confined space conditions. 

There is a small potential that opening a valve may cause an uncontrolled quick release of ponded water, 

which will flood the access area. Therefore, it is critical that correct confined space procedures be adhered 

to and suitable removal gear (such as a winch and harness system) be employed for emergency retrieval 

of maintenance staff that may be momentarily overcome by water under high pressure flow, slick, or cold 

conditions. 

Servicing of electrical components and welding repairs should be performed by professional contractors. 

Inherent wet conditions can pose safety threats to inexperienced inspectors and maintenance crews where 

electricity is involved. When inspecting electric-dependent mechanical components, power should be shut 

off prior to inspection and full body rubber coverage, including gloves, should be used. 
Section 2: Maintenance Activity Profile Sheets 

M-8 Nuisance Issues 

M-8 Nuisance Issues

Animals 

Problems to Inspect For 

Figure M8.1: Animal burrow in pond 

embankment. 

Animal burrows, dams, and dens can be significant 

maintenance issues associated with proper pond and 

wetland operation and structural stability (Figure 

M8.1). 

Groundhog/woodchuck burrows will be above the 

permanent pool and are easier to spot than muskrat 

burrows, which are located both at and below the 

permanent pool. Overgrown dam embankments may 

be riddled with burrow complexes that are not visible 

to the eye until the brush has been cleared. Usually, 

if one burrow is found, more are present, as rodent 

burrowing complexes usually have several 

ingress/egress points. 

Beaver dams and dens (Figure M8.2) tend to be 

obvious in all but the most neglected stormwater 

ponds and wetlands where damming may have been 

present for so long that the original appearance has 

been almost permanently altered. 

Figure M8.2: Beaver dam. 

Muskrats tend to be elusive but are occasionally 

visible. Groundhogs tend to be less shy and 

sometimes can be seen either feeding or loafing in 

grassy areas. Beavers are visible in relation to how 

comfortable they are with human presence. Another 

indication of rodent activity is the ‘slide trail’ located 

on slopes where rodents have created paths for 

commuting and dragging brush. 

Corrective Actions 

Rodent management is a contentious issue with strong feelings both for and against the presence of these 

animals in a suburban setting. There are many types of measures that can be used to ensure that the 

animals will not continue to negatively impact the stormwater pond or wetland. 

Existing burrows should be plugged by filling with material similar to the existing material and capped 

just below grade with a 50/50 mix of soil and concrete. If plugging of burrows does not discourage the 

animals from returning, further measures should be taken to either remove the animal population or make 

critical areas of the facility unattractive to them. 

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Section 2: Maintenance Activity Profile Sheets 

M-8 Nuisance Issues 

Management options for beaver control include complete tolerance, evaluation on a site-by-site basis, and 

complete removal. Beaver populations typically will only respond to trapping, dam and lodge removal, or 

the use of beaver “baffles”. Beavers usually do not remain in unsuitable areas. If their dams are breached 

and their lodges are damaged on a regular basis, the animals typically move on to another location. For 

instance, their lodges and dams may be removed by simple mechanical methods over two to three 

seasons. Once these structures are destroyed, regular maintenance of the facilities is often adequate to 

prevent their activity from becoming a future problem. 

However, maintenance staff should be prepared for the displaced animals to be persistent in their efforts 

to maintain their dams and lodges. Monthly site checks are recommended to ensure that dams and lodges 

are not rebuilt in the weeks after the initial removal. Once there is no evidence of recent beaver activity, 

normal less frequent maintenance usually suffices to keep the facility functioning properly. 

If there can be no tolerance of beaver activity, then the parties responsible for beaver control must 

consider relocating or trapping the unwanted animals. It is important to keep in mind that whatever 

features make the community appealing to one beaver will also make the area desirable to other beavers. 

Once one animal or family is removed, the pond or wetland will likely be re-occupied by other beavers, as 

young males are forced to find their own habitat areas each spring. Animal specialists perform trapping. If 

removal or trapping is utilized as a management tool, expect to continue trapping the area on a regular 

(i.e., seasonal) basis to maintain the level of control desired by the community. There are two additional 

points to consider concerning trapping: 

 Beaver relocation is much more expensive and challenging than straight trapping (killing beaver 

with standard beaver traps). 

 The existence of jurisdictions willing to accept relocated beavers is limited. 

The final option for minimizing the impact of beaver activity is the use of proprietary beaver baffles. The 

baffles do not eliminate the beaver impoundments, but are intended to minimize their size. The purpose 

of the baffle is to reduce the impact of rising water levels on real property (bridges, open areas, private 

property, pathways, etc.) by providing a manual method for changing the water level in the ponds (thus, 

making dam building more difficult). 

Waterfowl 

Problems to Inspect For 

Waterfowl damage usually takes the form of either 

reduced vegetative species due to overgrazing, or poor 

water quality due to high fecal coliform counts. 

Waterfowl issues usually involve the overpopulation 

of year-round duck (Figure M8.3) and geese 

populations (usually Canadian Geese, Branta 

canadensis). Geese and duck droppings on asphalt 

paths, pond side slopes, docks and cart ways are also 

easy aesthetic nuisances to spot. 

Figure M8.3: Duck family. 

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Section 2: Maintenance Activity Profile Sheets 

M-8 Nuisance Issues 

Corrective Actions 

The following actions can control waterfowl impacts: 

 Adding shoreline vegetation and no-mow zones. 

 Using proprietary products for managing/discouraging waterfowl/goose populations 

 Using trained canines to intimidate geese - Border Collies are the most common species used. 

 Addling eggs - shaking the eggs of nesting geese to make the eggs nonviable while still allowing 

the female goose to perform her breeding duties. 

 Introducing predators such as snapping turtles. 

Mosquitoes 

Problems to Inspect For 

Mosquito problems are usually brought to the attention of the maintenance authority by adjacent 

homeowners, or where organized mosquito control programs exist, by mosquito control or abatement 

districts. In some locations, the primary cause of a mosquito infestation may be a stormwater structure(s), 

but in other areas the primary cause may be natural or other man-made habitats. Sometimes, it will be 

both. Stormwater structures should be periodically checked to determine if there are excessive amounts of 

mosquitoes. 

Stormwater ponds typically will not have mosquito production problems in a central pool that’s 6-8 ft. 

deep, as long as it never dries out or becomes so depleted that water quality is impaired. A relatively 

large, deep pool helps promote and maintain aquatic predators of mosquito larvae (e.g. larvivorous fishes, 

dragonfly naiads, predacious diving beetles, water boatmen, backswimmers, salamander larvae). 

However, in some locations, even an abundance of natural predators may not be enough to control 

mosquito populations. A deep central pool also inhibits vegetation colonization within the pool, allowing 

wind to agitate the surface water, which discourages mosquito egg-laying. The primary areas of mosquito 

production are in the shallow aquatic bench areas that form the pond’s periphery and margins. 

Fluctuation in the pond’s water levels can cause isolated areas or pockets within the aquatic bench to 

cycle in a wet-dry-wet manner, creating conditions under which peripheral low spots, swales or potholes 

may become mosquito-rearing habitats. Sites like these that have fluctuating water levels (i.e. wet-drywet) for extended periods of time can favor the production of floodwater or temporary water mosquito 

species, many of which can fly long distances. 

Maintaining relatively high and stable water levels over the aquatic bench helps reduce floodwater 

mosquito populations. In many locations, however, (and for the best water quality functioning of the 

pond) it may be impossible to achieve or maintain such high water level stability. In some cases, thick 

mats of vegetation that cover aquatic and safety benches, emergent plants, submerged aquatic vegetation, 

or floating algae, can also promote mosquito production. Thick vegetation can inhibit access of mosquito 

predators to mosquito rearing sites, creating a refuge within the aquatic or safety benches where either 

permanent (“standing”) water mosquitoes or more ephemeral floodwater mosquitoes can develop and 

emerge. As such, without unduly sacrificing water quality goals, the aquatic and safety benches should 

not be allowed to develop excessively thick screens or layers of aquatic vegetation. In some situations, 

mosquito production may still be high despite these precautions. Insecticides may need to be applied in 

limited quantities to control mosquito larvae. 

 

Like stormwater ponds, stormwater wetlands have similar concerns and remedies with mosquito 

production. Of particular concern is a stormwater wetland’s smaller and possibly shallower central micropool, and an expanded high marsh pond periphery containing less than 6 inches of water. Even the 

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Section 2: Maintenance Activity Profile Sheets 

M-8 Nuisance Issues 

wetland’s low marsh zone, being only 6-18 inches deep, could form problematic breeding spots during 

times of drought and subsequent rewetting. In some instances, limited amounts of larvicides may need to 

be used.

Corrective Actions 

The most effective mosquito control program is one that eliminates potential breeding habitats. Most 

stagnant pools of water can be attractive to mosquitoes and the source of a large mosquito population. 

Ponded water such as open cans and bottles, debris and sediment accumulations, and areas of ground 

settlement provide ideal locations for mosquito breeding. A maintenance program dedicated to 

eliminating potential breeding areas is preferable to controlling flying mosquitoes. 

Whenever excessive mosquito production is encountered in a stormwater structure, a state, county, or 

local mosquito control or abatement district should be contacted to request appropriate control actions. In 

areas where such organized mosquito control programs do not exist, contract with a private company for 

control actions. Alternatively, a knowledgeable homeowner or homeowner’s association might be able to 

undertake some limited control actions on their own. Quite often, it might be a matter of contacting a 

local stormwater management agency to undertake needed or neglected maintenance activities within a 

stormwater structure. 

Organized mosquito control or abatement districts typically provide comprehensive, integrated pest 

management remedies for addressing excessive mosquito production, involving source reduction, 

larviciding and adulticiding techniques. Private companies tend to be restricted to larviciding efforts, and 

wherever they might attempt some source reduction remedies in a stormwater structure, they should only 

do so in consultation with the local stormwater management agency. Larvicide efforts target potential or 

actual breeding areas and treat them with insecticides that include bacterially-produced products, juvenile 

growth hormone mimics, and organophosphates. Adulticides that are applied to more widespread areas by 

aircraft or truck-mounted sprayers include organophosphates and synthetic pyrethroids and should be 

used only when source reduction or larviciding efforts are not working. Application of any pesticides 

must be in accordance with the requirements specified on the labels. 

Seasonal stocking of predatory fish that eat mosquito larvae is also undertaken in many areas by mosquito 

control or abatement districts, relying upon mosquitofish (Gambusia spp.) in warmer climates, and on the 

black-striped topminnow (Notrophus fundulus), in colder climates. Private companies or homeowners 

should not undertake fish stocking on their own without first consulting with their state fish and wildlife 

management agency and/or their state nongame or natural heritage programs to be sure that such fish 

stocking is permissible and that all pertinent regulations are followed.

Undesirable Plant Communities 

Problems to Inspect For 

Diverse plant communities support diverse and balanced aquatic communities that host beneficial species 

such as mosquito predators. Poorly maintained ponds and wetlands are particularly susceptible to the 

establishment of undesirable plant communities that include monocultures and non-native invasive 

species. Aquatic plant species such as cattails and common reed are typical monocultures seen in ponds 

and wetlands, and as previously mentioned cattail stands in particular can produce the very difficult to 

control Coquilletidia perturbans mosquito, an aggressive biter. Similarly, side slopes and embankments 

are susceptible to rapid colonization by non-natives such as multiflora rose, kudzu (southeastern states), 

purple loosestrife, and porcelain berry. 

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Section 2: Maintenance Activity Profile Sheets 

M-8 Nuisance Issues 

Corrective Actions 

Management of monolithic plant communities and weeds requires a long-term commitment to action to 

prevent large-scale problems. Mechanical and hand removal of monocultures such as cattails and 

common reed is often necessary in conjunction with replanting with other appropriate native emergent 

species. Algaecides and herbicides are often used to eradicate existing weed species. This method treats 

the problem as an ongoing maintenance issue and generally requires multiple treatments throughout the 

growing season. It is often the most effective method of maintaining the desired aesthetic standard for a 

pond. 

Caution should be exercised in performing chemical applications in that some applications may have the 

desired affect of removing unwanted vegetation, but may increase toxic risks to other resident species. 

The removal of one weed species creates an opportunity for the growth of another. Once the initial weed 

is eliminated, the ecological niche previously occupied by the species becomes available to other 

opportunistic species. Note that multiple applications may be necessary to maintain the desired aesthetic 

standard for a stormwater pond or wetland. 

Maintaining and/or planting upland buffer zones can help to reduce the introduction of nuisance plant 

species. Planting emergent vegetation may also reduce nuisance algae blooms and waterfowl access. 

These plants compete with the algae for the available nutrients stored in the pond substrate. As fewer 

nutrients are available for the algae, their prolific growth potential can be suppressed. Another vegetation 

management technique is through the establishment of buffer strips or “no mow areas” around the 

perimeter of stormwater wet ponds and wetlands. These zones help intercept and filter nutrient laden 

runoff as well as stabilize pond banks. Therefore a mixture of plants with varying heights is 

recommended. 

Water Quality Degradation 

Problems to Inspect For 

Stormwater ponds and wetlands are susceptible to poor water quality when upland land uses are highly 

urbanized, deliver large quantities of nutrients, or contain illicit discharges with high concentrations of 

bacteria and other pollutants. Pond and wetland designs with inefficient turn over (i.e., poor flow 

circulation) also contribute to water quality degradation. Common indications of poor water quality 

include an off color (e.g., bright green sheen from algae) or unpleasant odor (e.g., presence of bacteria). 

Poor water quality, including low dissolved oxygen and organic over-enrichment can also undesirably 

promote mosquito production by reducing mosquito predators and providing food for mosquito larvae. 

Corrective Actions 

Maintaining water quality in stormwater ponds and wetlands is challenging, as they are designed to retain 

constituents in stormwater that can degrade receiving waters. However, a number of water quality related 

fixes are noted below: 

• Bacterial Improvements 

Excessive sediments in a pond can contribute to algae problems. If sediment layers become 

anaerobic, harmful chemicals, noxious odors, and phosphorus can be released into the water column. 

These conditions can be minimized through the introduction of bacteria in the pond. The bacteria, in 

the presence of adequate aeration, “digest” the muck layer without producing the harmful side effects, 

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Section 2: Maintenance Activity Profile Sheets 

M-8 Nuisance Issues 

55

such as odor, associated with anaerobic decomposition. Through the reduction of available 

phosphorus, algae growth can be limited. Treatments usually start in early April and continue through 

September. 

• Diffusers and surface aerators 

Air can be introduced into the pond or wetland through various systems to facilitate biological 

decomposition of pond muck, de-stratify thermal layers in the water and improve the ecological 

health of the system. In general air promotes biological activity, which reduces the amount of 

available nutrients for algae. 

Diffusers use an air compressor and hoses to bring air into the water column of the pond or wetland. 

Diffuser systems are low maintenance and are often compared to aquarium compressors on a larger 

scale. They require annual maintenance and are not recommended for permanent pools less than eight 

feet deep. 

Aerators resemble fountains in their appearance. They require a motor mounted to an impeller or 

other type of agitator to “splash” the water. This physical action introduces air to the water. They 

should be removed from the pond in the late fall to prevent freeze damage and returned to the pond in 

the spring, after the last freeze. Trash, debris, algae, pond weeds and aquatic plants can bind up 

moving parts, causing excessive wear and generally cause motors to burn out prematurely. Because 

these aerators typically draw from the surface of the pond, they are generally not recommended for 

reducing algae bloom potential or increasing dissolved oxygen in the system, but may provide visual 

enhancement. 

• Flocculants 

Flocculants are chemicals applied to ponds to act indirectly on the algae through promotion of 

settling. The application of flocculates of buffered alum products to the water causes phosphorus and 

other materials suspended in the water column to settle. Removal of phosphorus from the water 

column limits the amount of this nutrient available to support algal growth. This works best when 

water clarity is greater than 24 inches. However, soils with excessive nutrients introduce phosphorous 

with every rain event and as a result, phosphorus levels are quickly recharged and the value of 

floccing the pond is minimized. The application of flocculants may require a permit. Therefore check 

with local authorities prior to application. 

Cautions and Safety Tips 

Addressing nuisance issues has few associated safety hazards when appropriately trained individuals 

conduct the specific tasks (e.g., trapping, chemical application). 
References 

References 

Brown, Ted and Jon Simpson. 2002. “Determining the Trophic State of Your Lake.” Watershed 

Protection Techniques, Volume 3 No. 4. Center for Watershed Protection. 

Brown, W. and T. Schueler. 1997. The Economics of Stormwater BMPs in the Mid-Atlantic Region. 

Prepared for: Chesapeake Research Consortium. Edgewater, MD. Center for Watershed 

Protection. Ellicott City, MD. 

Center for Watershed Protection. 2001. The Economic Benefits of Protecting Virginia’s Streams, Lakes, 

and Wetlands and The Economic Benefits of Better Site Design in Virginia. Prepared for Virginia 

Department of Conservation and Recreation. Richmond, VA. 

Center for Watershed Protection. Stormwater Manager’s Resource Center. On-Line at: 

www.stormwatercenter.net

Schueler, et al. 2007. Urban Subwatershed Restoration Manual No. 3: Urban Stormwater Retrofit 

Practices. Center for Watershed Protection. Prepared for Office of Wastewater Management, 

USEPA. Washington, D.C. 

Environmental Protection Agency. 2005a. Maryland-Delaware Stormwater Management/Mosquito 

Control Workshop (Salisbury, MD., Feb. 9, 2005). Posting of PowerPoint presentations from 

EPA-sponsored workshop at http://www.epa.gov/maia/html/swmprog.html 

Environmental Protection Agency. 2005b. National Management Measures to Control Nonpoint Source 

Pollution from Urban Areas. Office of Wetlands, Oceans and Watersheds. Publication Number 

EPA 841-B-05-004, November 2005 

Metzger, M.E. 2004. Managing Mosquitoes in Stormwater Treatment Devices. Univ. Calif ANR Publ. 

8125. 11 pp. 

Natural Resources Conservation Service. 1987. Natural Resources Conservation Handbook. 

Washington, D.C. 

Newman, Jonathan. 1997. “Information Sheet 3: Control of Algae with Straw.” IACR-Centre for 

Aquatic Plant Management. Aquatic Systems Inc. Web Page 

(http://www.execpc.com/~aqsys/barley.html) 

Robert L. Knight a, William E. Walton b, George F. O’Meara c, William K. Reisen d, Roland Wass e 

2003, Strategies for effective mosquito control in constructed treatment wetlands 

Santana, F., J. Wood, R. Parsons, and S. Chamberlain. 1994. Control of Mosquito Breeding in Permitted 

Stormwater Systems. For: Southwest Florida Water Management District. Brooksville, FL. 

Walton, W.E. 2003. Managing Mosquitoes in Surface-Flow Constructed Treatment Wetlands. Univ. 

Calif. ANR Publ. 8117. 11 pp. 

Watershed Management Institute (WMI). 1997. Operation, Maintenance, and Management of 

Stormwater Management Systems. Prepared for: US EPA Office of Water. Washington, DC. 

56
References 

57

Winer, Rebecca. 2000. National Pollutant Removal Performance Database. Center for Watershed 

Protection. 
Appendix A 

Appendix A: 

Unit Costs for Pond and Wetland Maintenance

Stormwater Wet Pond and Wetland Management Guidebook 
Stormwater Wet Pond and Wetland Management Guidebook 

TABLE A-1.

UNIT 

COSTS FOR 

POND AND 

WETLAND 

MAINTENANCE1

Maintenance Item Unit Price ($) Unit 

Mobilization 

Cost ($)2

Permanent Pool Issues 

Dam/ Embankment 

unclog internal drains for embankments 10 lf 1,500 

repair low spots in dam or berm 170 cy 1,500 

Clogging 

debris removal (preventative) 350 event 0 

clear outfall channel of sediment 130 cy 0 

clogged low flow 750 event 800 

Pipe Repairs 

Structural - Riser and Barrel 

re-tar CMP barrel 11 sf 800 

install new elbow underground 1,200 ea 800 

repair CMP barrel joint leak 530 ea 800 

repair leaking concrete principal spillway joint 1,200 ea 0 

replace riser (CMP) 12,000 ea >2,500 

replace riser (concrete) 20,000 ea >2,500 

replace barrel 1,000 lf >2,500 

1) These costs were largely derived from data from the Maryland region, based on bid proposal and actual 2005 proj2) Cost at four levels: $0 for no mobilization; $800 for minimal mobilization; $1,500 for small project mobilization; >$2

mobilization. Note that these are approximations. For items with no mobilization cost, it is assumed that the mobiincorporated into the overall unit cost, or that the maintenance can be completed during inspection. 

3) Bottom number in range represents ideal maintenance interval. Top number represents maximum interval betwee

R indicates repair items, whose frequency is somewhat unpredictable. The frequencies sometimes reported in pa

estimate of typical repair frequency. 

Page A-1 
Stormwater Wet Pond and Wetland Management Guidebook 

Maintenance Item Unit Price ($) Unit 

Mobilization 

Cost ($)2

Structural - Pipes 

replace existing underground elbow 1,400 ea 800 

slip line failing pipes 90 lf >2,500 

replace end sections <36" 600 ea 1,500 

remote control TV video pipes 1 lf 800 

Structural - Other Concrete 

concrete work under ground 600 cy 1,500 

concrete work above ground 450 cy 1,500 

grout cracks 50 lf 0 

parge spalling 25 sf 0 

repair gutter spalling 230 event 800 

injection grout concrete leaks 180 lf 800 

Structural: Metal 

new low flow trash rack 1,700 ea 800 

install high stage trash rack 4'x2' 1,100 ea 1,500 

replace CMP anti-vortex device <48" 1,500 ea 1,500 replace CMP anti-vortex device >48" 4,600 ea 1,500 

remove bolts, lift lugs, form nails 80 ea 800 

1. These costs were largely derived from data from the Maryland region, based on bid proposal and actual project da

2. Cost at four levels: $0 for no mobilization; $800 for minimal mobilization; $1,500 for small project mobilization; >$2

mobilization. Note that these are approximations. For items with no mobilization cost, it is assumed that the mobiincorporated into the overall unit cost, or that the maintenance can be completed during inspection. 

3. Bottom number in range represents ideal maintenance interval. Top number represents maximum interval betwee

R indicates repair items, whose frequency is somewhat unpredictable. The frequencies sometimes reported in pa

estimate of typical repair frequency. 

Page A-2 
Stormwater Wet Pond and Wetland Management Guidebook 

Maintenance Item Unit Price ($) Unit 

Mobilization 

Cost ($)2

Vegetation Management

sod 3.30 sy 800 

seed and top soil bare areas (3 inch depth) 4.40 sy 800 

plant 1.5 inch tree 84 ea 0 

plant shrub 15 ea 0 

mowing 300 ac 0 

clear outfall and channel of trees 5.50 sy 800 

clear embankment of small trees by hand 3.30 sy 800 

clear embankment trees with Ambusher or Brushhog 0.90 sy 800 

remove live tree (<12 inches) 130 ea 800 

remove live trees larger than 12 inches, <24 inches 250 ea 800 

remove downed timber (up to 40 cy of material) 2,200 event 0 

remove dumped vegetative material (up to 40 cy) 2,600 event 0 

install wetland plant 6 ea 800 

remove invasive wetland vegetation (machine remove phragmites) 

 (up to 40 cy) 3,000 event 0 

spray for algae (0.25 ac pond) 600 ea 0 

spray for cattails (0.25 ac pond) 330 ea 0 

repair low spots in dry pond bottom 25 sy 1,500 

remove woody vegetation from dry pond bottom 1,700 event 0 

1. These costs were largely derived from data from the Maryland region, based on bid proposal and actual projec

2. Cost at four levels: $0 for no mobilization; $800 for minimal mobilization; $1,500 for small project mobilization; 

mobilization. Note that these are approximations. For items with no mobilization cost, it is assumed that the mincorporated into the overall unit cost, or that the maintenance can be completed during inspection. 

3. Bottom number in range represents ideal maintenance interval. Top number represents maximum interval be

activities. R indicates repair items, whose frequency is somewhat unpredictable. The frequencies sometimes represent an estimate of typical repair frequency. 

Page A-3 
Stormwater Wet Pond and Wetland Management Guidebook 

Maintenance Item Unit Price ($) Unit 

Mobilization 

Cost ($)2

Dredging and Mucking 

dredge wet ponds (jobs larger than 1000 cy) haul offsite 60 cy >2,500 

dry pond sediment removal 7,600 event 0 

dewater pond 900 event 0 

muck out undergrounds 390 cy 0 

dewater and remove sludge from underground facilities 1 gal 0 

typical sediment dump fee (not including trucking) 66 ton 0 

truck day for landfill to transport underground dredge materials 

(minimum, assume 2 to 4 trips in one day) 800 trip-day 0 

Access/ Safety 

install warning signs 210 ea 0 

add manhole steps 100 ea 800 

new manhole cover 250 ea 0 

create 12' access road (permanent, cut/fill balances) 40 lf 1,500 

create 12' access road (permanent, cut/fill non-balance) 65 lf 1,500 

create 12' access road (temp) 12 lf 1,500 

install chainlink fence 26 lf 800 

install ladder (8 foot) 220 each 800 

install three rail fence 15 lf 800 

repair asphalt path 26 cy 800 

supply lock and chain for first one (additional at $30 apiece) 130 ea 0 

1. These costs were largely derived from data from the Maryland region, based on bid proposal and actual project da

2. Cost at four levels: $0 for no mobilization; $800 for minimal mobilization; $1,500 for small project mobilization; >$2

mobilization. Note that these are approximations. For items with no mobilization cost, it is assumed that the mobiincorporated into the overall unit cost, or that the maintenance can be completed during inspection. 

3. Bottom number in range represents ideal maintenance interval. Top number represents maximum interval betwee

R indicates repair items, whose frequency is somewhat unpredictable. The frequencies sometimes reported in pa

estimate of typical repair frequency. 

Page A-4 
Stormwater Wet Pond and Wetland Management Guidebook 

Page A-5 

Maintenance Item Unit Price ($) Unit 

Mobilization 

Cost ($)2

Mechanical Components 

remove old valve 300 ea 800 

install new valve (<36 inches) 4,600 ea 1,500 

install new valve (< 24 inches) 3,100 ea 1,500 

install new valve (<11 inches) 1,300 ea 1,500 

install new valve (<7 inches) 460 ea 800 

lubricate valves (same price for first four) 300 ea 0 

Nuisance Issues 

pond/ wetland aeration 560 ea 0 

treat pond for mosquitoes 1,000 acre 0 

trap beavers (one week, one location, family of 6) 1,000 event 0 

fill animal burrows 23 sy 800 

remove graffiti 310 day 800 

Erosion/ Channel Maintenance 

establish new riprap pilot channels (8' wide, 1' deep) 38 lf 1,500 

remove and replace rip rap or pea gravel 160 sy 1,500 

shoreline protection 50 lf 1,500 

new riprap (general) 80 cy 1,500 

erosion repair 1,100 event 0 

jet clean rip rap (6X 15, 1' silt) 2,500 event 0 

4) These costs were largely derived from data from the Maryland region, based on bid proposal and actual project da

5) Cost at four levels: $0 for no mobilization; $800 for minimal mobilization; $1,500 for small project mobilization; >$2

mobilization. Note that these are approximations. For items with no mobilization cost, it is assumed that the mobiincorporated into the overall unit cost, or that the maintenance can be completed during inspection. 

6) Bottom number in range represents ideal maintenance interval. Top number represents maximum interval betwee

R indicates repair items, whose frequency is somewhat unpredictable. The frequencies sometimes reported in pa

estimate of typical repair frequency. 
Appendix B 

Appendix B: 

Pond and Wetland Checklists

Stormwater Wet Pond and Wetland Management Guidebook 
Adapted from WMI, 1997 Page 1 of 5

STORMWATER POND / STORMWATER WETLAND CONSTRUCTION INSPECTION CHECKLIST

Date: Time:

Project:

Location:

Site Status (active, inactive, completed):

Inspector(s):

Type of Practice:

G Micropool ED Pond G Shallow Wetland

G Wet Pond G Shallow ED Wetland

G Multiple Pond System G Pond / Wetland System

G Pocket Pond G Pocket Wetland

Construction Sequence Satisfactory Unsatisfactory Comments

I. Pre-Construction / Materials and Equipment

Pre-construction meeting

Pipe and appurtenances on-site prior to construction

and dimensions checked

1. Material (including protective coating, if specified)

2. Diameter

3. Dimensions of metal or pre-cast concrete riser

4. Required dimensions between water control

structures (orifices, weirs, etc.) are in accordance

with approved plans

5. Barrel stub for prefabricated pipe structures at

proper angle for design barrel slope

6. Number and dimensions of prefabricated anti-seep

collars

7. Watertight connectors and gaskets

8. Outlet drain valve

Project benchmark near pond site

Equipment for temporary de-watering / sediment and

erosion control

II. Subgrade Preparation

Area beneath embankment stripped of all vegetation,

topsoil, and organic matter

Core trench excavated and backfilled

III. Pipe Spillway Installation

Method of installation detailed on plans

A. Bed preparation

Installation trench excavated with specified side

slopes

Stable, uniform, dry subgrade of relatively

impervious material (If subgrade is wet, contractor

shall have defined steps before proceeding with

installation)

Invert at proper elevation and grade
STORMWATER POND / STORMWATER WETLAND CONSTRUCTION INSPECTION CHECKLIST

Construction Sequence Satisfactory Unsatisfactory Comments

Adapted from WMI, 1997 Page 2 of 5

B. Pipe placement

Metal / plastic pipe

1. Watertight connectors and gaskets properly

installed

2. Anti-seep collars properly spaced and having

watertight connections to pipe

3. Backfill placed and tamped by hand under

“haunches” of pipe

4. Remaining backfill placed in max. 8 inch lifts

using small power tamping equipment until 2 feet

cover over pipe is reached

Concrete pipe

1. Pipe set on blocks or concrete slab for pouring of

low cradle

2. Pipe installed with rubber gasket joints with no

spalling in gasket interface area

3. Excavation for lower half of anti-seep collar(s)

with reinforcing steel set

4. Entire area where anti-seep collar(s) will come in

contact with pipe coated with mastic or other

approved waterproof sealant

5. Low cradle and bottom half of anti-seep collar

installed as monolithic pour and of an approved

mix

6. Upper half of anti-seep collar(s) formed with

reinforcing steel set

7. Concrete for collar of an approved mix and

vibrated into place (protected from freezing while

curing, if necessary)

8. Forms stripped and collar inspected for

honeycomb prior to backfilling. Parge if

necessary.

C. Backfilling

Fill placed in maximum 8 inch lifts

Backfill taken minimum 2 feet above top of anti-seep

collar elevation before traversing with heavy

equipment

IV. Riser / Outlet Structure Installation

Riser located within embankment

A. Metal riser

Riser base excavated or formed on stable subgrade

to design dimensions

Set on blocks to design elevations and plumbed

Reinforcing bars placed at right angles and

projecting into sides of riser

Concrete poured so as to fill inside of riser to invert

of barrel

B. Pre-cast concrete structure
STORMWATER POND / STORMWATER WETLAND CONSTRUCTION INSPECTION CHECKLIST

Construction Sequence Satisfactory Unsatisfactory Comments

Adapted from WMI, 1997 Page 3 of 5

Dry and stable subgrade

Riser base set to design elevation

If more than one section, no spalling in gasket

interface area; gasket or approved caulking material

placed securely

Watertight and structurally sound collar or gasket

joint where structure connects to pipe spillway

C. Poured concrete structure

Footing excavated or formed on stable subgrade, to

design dimensions with reinforcing steel set

Structure formed to design dimensions, with

reinforcing steel set as per plan 

Concrete of an approved mix and vibrated into place

(protected from freezing while curing, if necessary)

Forms stripped & inspected for honeycomb prior to

backfilling; parge if necessary

V. Embankment Construction

Fill material

Compaction

Embankment

1. Fill placed in specified lifts and compacted with

appropriate equipment

2. Constructed to design cross-section, side slopes

and top width

3. Constructed to design elevation plus allowance for

settlement

VI. Impounded Area Construction

Excavated / graded to design contours and side slopes

Inlet pipes have adequate outfall protection

Forebay(s)

Pond benches

VII. Earth Emergency Spillway Construction

Spillway located in cut or structurally stabilized with

riprap, gabions, concrete, etc.

Excavated to proper cross-section, side slopes and

bottom width

Entrance channel, crest, and exit channel constructed to

design grades and elevations

VIII. Outlet Protection

A. End section

Securely in place and properly backfilled

B. Endwall

Footing excavated or formed on stable subgrade, to

design dimensions and reinforcing steel set, if

specified
STORMWATER POND / STORMWATER WETLAND CONSTRUCTION INSPECTION CHECKLIST

Construction Sequence Satisfactory Unsatisfactory Comments

Adapted from WMI, 1997 Page 4 of 5

Endwall formed to design dimensions with

reinforcing steel set as per plan

Concrete of an approved mix and vibrated into place

(protected from freezing, if necessary)

Forms stripped and structure inspected for

honeycomb prior to backfilling; parge if necessary

C. Riprap apron / channel

Apron / channel excavated to design cross-section

with proper transition to existing ground

Filter fabric in place

Stone sized as per plan and uniformly place at the

thickness specified

IX. Vegetative Stabilization

Approved seed mixture or sod

Proper surface preparation and required soil

amendments

Excelsior mat or other stabilization, as per plan

X. Miscellaneous

Drain for ponds having a permanent pool

Trash rack / anti-vortex device secured to outlet

structure

Trash protection for low flow pipes, orifices, etc.

Fencing (when required)

Access road

Set aside for clean-out maintenance
STORMWATER POND / STORMWATER WETLAND CONSTRUCTION INSPECTION CHECKLIST

Adapted from WMI, 1997 Page 5 of 5

Additional Comments:

Action to be Taken:

No action necessary. Continue routine inspections.

Correct noted site deficiencies by

1st notice

2nd notice

Submit plan modifications as noted in written comments by

Notice to Comply issued

Final inspection, project completed
N/A = Not Applicable 1 = Monitor for Future Repairs

N/I = Not Investigated 2 = Routine Repairs Needed

0 = Not a Problem 3 = Immediate Repair Needed Page 1 of 6

POND / WETLAND MAINTENANCE INSPECTION FORM

Facility Number: Date: Time:

Subdivision Name: Watershed:

Weather: Inspector(s):

Date of Last Rainfall: Amount: Inches Streets:

Mapbook Location: GPS Coordinates:

Property Classification: Residential 9 Government 9 Commercial 9 Other: 

Type of Practice: Wet Pond 9 Dry Pond 9 Micropool ED 9 Multiple Pond System 9 Pocket Pond 9

Shallow Wetland 9 Shallow ED 9 Pond/ Wetland 9 Pocket Wetland 9

Confined 9 Unconfined 9 Barrel Size As-built Plan Available? Yes 9 No 9

Is Facility Inspectable? Yes 9 No 9 Why? Comments Specific Location(s):

Scoring Breakdown:

N/A = Not Applicable 1 = Monitor (potential for future problem exists) * Use open space in each section to

further explain scoring as needed N/I = Not Investigated 2 = Routine Maintenance Required

0 = Not a Problem 3 = Immediate Repair Necessary

1. Outfall Channel(s) from Pond

Woody growth within 5’ of outfall barrel N/A N/I 0123

Outfall channel functioning N/A N/I 0123

Manholes, Frames and Covers N/A N/I 0123

Released water undercutting outlet N/A N/I 0123

Erosion N/A N/I 0 1 2 3

Displaced rip rap N/A N/I 0 1 2 3

Excessive sediment deposits N/A N/I 0123

Other: N/A N/I 0 1 2 3

2. Downstream Dam Bank

Cracking, bulging, or sloughing of dam N/A N/I 0123

Erosion and/or loss of dam material N/A N/I 0123

Animal burrows N/A N/I 0 1 2 3

Soft spots or boggy areas N/A N/I 0123

Woody growth or unauthorized plantings on dam N/A N/I 0123

Other: N/A N/I 0 1 2 3

3. Upstream Dam Bank

Cracking, bulging, or sloughing of dam N/A N/I 0123

Erosion and/or loss of dam material N/A N/I 0123

Animal Burrows N/A N/I 0 1 2 3

Soft spots or boggy areas N/A N/I 0123

Woody growth or unauthorized plantings on dam N/A N/I 0123

Other: N/A N/I 0 1 2 3
POND / WETLAND MAINTENANCE INSPECTION FORM

N/A = Not Applicable 1 = Monitor for Future Repairs

N/I = Not Investigated 2 = Routine Repairs Needed

0 = Not a Problem 3 = Immediate Repair Needed Page 2 of 6

4. Emergency Spillway

Woody growth or unauthorized plantings N/A N/I 0123

Erosion or back cutting N/A N/I 0 1 2 3

Soft or boggy areas N/A N/I 0123

Obstructions / debris N/A N/I 0123

5. Principal Spillway Built to Plans

# of Barrels: Size: RCP CMP PVC STEEL or MASONRY (Circle One)

Confined space entry permit required for entry into all riser and barrels Entry Approved 9 Entry Denied 9

Minor spalling or parging (<1”) N/A N/I 0 1 2 3

Major spalling (exposed rebar) N/A N/I 0123

Joint failure N/A N/I 0 1 2 3

Loss of joint material N/A N/I 0 1 2 3

Leaking N/A N/I 0123

Corrosion N/A N/I 0 1 2 3

Protective material deficient N/A N/I 0 1 2 3

Misalignment or split seams / joints N/A N/I 0 1 2 3

Other: N/A N/I 0 1 2 3

6. Riser Built to Plans

Size: CONC CMP or MASONRY (Circle One)

Minor spalling or parging (<1”) N/A N/I 0 1 2 3

Major spalling (exposed rebar) N/A N/I 0123

Joint failure N/A N/I 0 1 2 3

Loss of joint material N/A N/I 0 1 2 3

Leaking N/A N/I 0123

Manhole access and steps acceptable N/A N/I 0123

Corrosion N/A N/I 0 1 2 3

Protective material deficient N/A N/I 0 1 2 3

Misalignment or split seams / joints N/A N/I 0 1 2 3

Anti-vortex device secure / acceptable N/A N/I 0 1 2 3

Sediment Accumulation within riser N/A N/I 0 1 2 3

Woody or vegetative growth within 25’ of riser N/A N/I 0123

Safety Rebar/pipes in place N/A N/I 0123

Safety Rebar/pipes corroded N/A N/I 0123

Other: N/A N/I 0 1 2 3

7. Low Flow Built to Plans

Orifice and/or trash rack obstructed N/A N/I 0123

Trash Rack Corrosion N/A N/I 0 1 2 3

Other: N/A N/I 0 1 2 3

8. Weir Trash Rack

Structurally sound N/A N/I 0123

Debris removal necessary N/A N/I 0 1 2 3

Corrosion N/A N/I 0 1 2 3
POND / WETLAND MAINTENANCE INSPECTION FORM

N/A = Not Applicable 1 = Monitor for Future Repairs

N/I = Not Investigated 2 = Routine Repairs Needed

0 = Not a Problem 3 = Immediate Repair Needed Page 3 of 6

9. Control Valve(s) Built to Plans

Size: Type:

Operation limited N/A N/I 0 1 2 3

Exercised N/A N/I 0 1 2 3

Leaks N/A N/I 0123

Chains & Locks N/A N/I 0 1 2 3

Set to design opening N/A N/I 0123

Other: N/A N/I 0 1 2 3

10. Pond Drain Valve

Operation limited N/A N/I 0 1 2 3

Exercised N/A N/I 0 1 2 3

Leaks N/A N/I 0123

Chained & locked correctly N/A N/I 0123

Other: N/A N/I 0 1 2 3

11. Toe & Chimney Drains Clear & Functioning N/A N/I 0 1 2 3

12. Rip-Rap Pilot Channel (Micropool only)

Sediment or debris build up N/A N/I 0123

Erosion/ Undermining N/A N/I 0123

13. Permanent Pool 

Visible pollution N/A N/I 0 1 2 3

Shoreline and / or side slope erosion N/A N/I 0123

Aquatic bench inadequately vegetated N/A N/I 0123

Abnormally high or low water (pool) levels N/A N/I 0123

Sediment / debris accumulation N/A N/I 0123

Bathometric study recommended No Yes

Other? N/A N/I 0 1 2 3

14. Dry Storage

Vegetation sparse N/A N/I 0123

Undesirable woody or vegetative growth N/A N/I 0123

Low flow channels obstructed N/A N/I 0123

Standing water or spots N/A N/I 0123

Sediment or debris accumulation N/A N/I 0123

Bathometric study recommended No Yes

Other: N/A N/I 0 1 2 3

15. Pretreatment

Maintenance access N/A N/I 0123

Is pretreatment a practice other than a forebay No Yes Of so, (code)

Dredging required No Yes

Hard pad condition (Wet pond only) N/A N/I 0123

Fixed vertical sediment depth marker present No Yes

Marker Reading

Sediment accumulation N/A N/I 0 1 2 3 Estimated % full %
 

POND / WETLAND MAINTENANCE INSPECTION FORM 

16. Inflow Points 

Number of inflow pipes: Direction: N E W S 

Endwalls, headwalls, end sections N/A N/I 0 1 2 3 

Outfall pipes N/A N/I 0 1 2 3 

Discharge undercutting outlet or displacing rip-rap N/A N/I 0 1 2 3 

Discharge water is causing outfall to erode N/A N/I 0 1 2 3 

Sediment accumulation N/A N/I 0 1 2 3 

17. Wet Pond Vegetation 

Invasive plants N/A N/I 0 1 2 3

% cover 

Vegetation matches landscape design plan N/A N/I 0 1 2 3 

Planting needed N/A N/I 0 1 2 3 

Shore erosion N/A N/I 0 1 2 3 

Coverage needs improvement N/A N/I 0 1 2 3 

18. Pond Buffer 

Encroachment by structures N/A N/I 0 1 2 3 

Clearing of vegetation N/A N/I 0 1 2 3 

Planting needed N/A N/I 0 1 2 3 

Predominant vegetation types: Forested 9 Shrubs 9 Meadow 9 Maintained Grass 9 Other: 

19. Special Structures 

Manhole access (steps, ladders) N/A N/I 0 1 2 3 

Vehicular access N/A N/I 0 1 2 3 

Concrete/masonry condition N/A N/I 0 1 2 3 

Trash racks N/A N/I 0 1 2 3 

Elbows N/A N/I 0 1 2 3 

Sediment / trash removal N/A N/I 0 1 2 3 

Manhole lockable nuts N/A N/I 0 1 2 3 

20. Miscellaneous 

Encroachment in pond area and/or easement area N/A N/I 0 1 2 3 

Fence condition N/A N/I 0 1 2 3 

Safety signs N/A N/I 0 1 2 3 

Complaints from local residents N/A N/I 0 1 2 3 

Graffiti N/A N/I 0 1 2 3 

Public hazards N/A N/I 0 1 2 3 

Excessive mosquitoes N/A N/I 0 1 2 3 

Were any pad locks cut and replaced No Yes How Many? 

N/A = Not Applicable 

N/I = Not Investigated 

0 = Not a Problem 

1 = Monitor for Future Repairs 

2 = Routine Repairs Needed 

3 = Immediate Repair Needed Page 4 of 6 
POND / WETLAND MAINTENANCE INSPECTION FORM

N/A = Not Applicable 1 = Monitor for Future Repairs

N/I = Not Investigated 2 = Routine Repairs Needed

0 = Not a Problem 3 = Immediate Repair Needed Page 5 of 6

Overall Condition of Facility

Total number of concerns receiving a: (1)_______ - Need Monitoring

(2)_______ - Routine Repair

(3)_______ - Immediate Repair Needed

Inspector’s Summary

Pictures Clock/Degrees Prin. Spill. Barrel Joints Clock/Degrees

1. 1.

2. 2.

3. 3.

4. 4.

5. 5.

6. 6.

7. 7.

8. 8.

9. 9.

10. 10.

11. 11.

12. 12.

13. 13.

14. 14.

15. 15.
POND / WETLAND MAINTENANCE INSPECTION FORM

N/A = Not Applicable 1 = Monitor for Future Repairs

N/I = Not Investigated 2 = Routine Repairs Needed

0 = Not a Problem 3 = Immediate Repair Needed Page 6 of 6

Sketches, If Necessary:
Home Owner Pond Inspection Checklist 

We encourage you to copy this checklist and maintain record of your inspections. (Adapted from Hampton Roads: 

A Guide for Maintaining and Operating BMPs.) Answering YES to any of these questions indicates a need for 

corrective action or consultation with a professional inspector. 

Date:______________ Inspected by:______________________________________ 

What to look for . . . Yes No 

° Does the facility show signs of settling, cracking, bulging, misalignment or other ‘ ‘

structural deterioration? 

° Do the embankments, emergency spillways, side slopes or inlet/outlet structures show ‘ ‘

signs of erosion? 

° Are the pipes going into and/or out of the pond clogged or obstructed? ‘ ‘

° Do the impoundment and inlet areas show erosion, low spots or lack of stabilization? ‘ ‘

° Are there trees present on the banks? ‘ ‘

° Is there evidence of animal burrows? ‘ ‘

° Are contributing areas unstabilized with evidence or erosion? ‘ ‘

° Do vegetated areas need mowing or is there a build up of clippings that could clog the ‘ ‘

facility? 

° Does sedimentation greatly decrease the BMPs capacity to hold water within the ‘ ‘

structure? 

° Is there standing water in appropriate or inappropriate areas? ‘ ‘

° Is there accumulation of trash or debris? ‘ ‘

° Is there evidence of encroachment or improper use of the impounded areas? ‘ ‘

° Are there signs of vandalism? ‘ ‘

° Do any safety devices such as fences, gates or locks need repair? ‘ ‘

° Is there excessive algae or dominance of one type of vegetation? ‘ ‘

° Is there evidence of automotive fluids entering or clogging the facility? ‘ ‘

° Is there evidence of a fish kill? ‘ ‘

° Do you see a lot of mosquito larvae (small “wigglers” or “tumblers”) in the water? ‘ ‘

° Is there evidence of excessive amounts of mosquitoes? ‘ ‘

Additional Observations: