Environmental Protection

Preparing For a Rainy Day

A guide to stormwater maintenance, inspection, and regulatory compliance

When we think of pollution, most of us conjure up images of smokestacks or drums of hazardous waste. But one of the most significant sources of water pollution in the United States today is stormwater runoff, and it merits the full attention of industrial and commercial facilities alike. In several recent landmark cases, the U.S. Environmental Protection Agency (EPA) reached a number of stormwater settlements, imposing multi-million-dollar penalties on the City of Dallas, commercial property owners, and construction firms for stormwater management violations at sites across the country. Strategies for avoiding violation notices and achieving compliance are mainly based on preventive maintenance programs that properly address stormwater problems.

EPA regulates stormwater primarily through the National Pollutant Discharge Elimination System (NPDES). The NPDES permit program is based on the statutory requirements contained in the Clean Water Act. As with many EPA programs, states can be delegated authority to develop and implement the program and conduct regulatory oversight.
The EPA Stormwater Program was implemented in two phases. Phase I addresses sources of stormwater runoff that have the greatest potential to negatively impact water quality, including 11 categories of industrial sources, medium and large municipal separate storm sewer systems (MS4s) located in incorporated places or counties with populations of 100,000, and construction activity that disturbs five or more acres of land. The Phase II Final Rule, published on Dec. 8, 1999, requires NPDES permit coverage for stormwater discharges from small MS4s and construction activity disturbing between one and five acres of land (i.e., small construction activities). The implementation of Phase II required establishment of stormwater programs in many municipalities that had poor or nonexistent prior inspection programs.

As more municipalities formalize their stormwater programs, the shift in enforcement is moving from sediment and erosion control to stormwater management. As municipalities establish their stormwater management inspection and maintenance programs, the level of enforcement has been increasing dramatically. The shift in enforcement is also moving from industrial facilities to commercial and even residential properties. Many homeowners associations (HOA) across the country are responsible for maintenance of their stormwater systems and may not even know it.

The responsibility for inspection and maintenance of stormwater best management practices (BMPs) varies across the country. In some municipalities, the property owner is responsible for inspection and maintenance of their BMPs, while in others the local government will assume that responsibility. It may also be a combination of responsible parties, for example, a local government will inspect and the property owner is responsible for maintenance. It is important to know what the requirements are for your site.

With the increased focus on maintenance of BMPs, many property and facility owners are now receiving notices of violations (NOVs). For ease of analysis, BMPs can be divided into two distinct groups, aboveground and belowground.
Aboveground BMPs commonly include detention/retention basins (often called ponds), swales, bioretention basins, managed wetlands, and others. Lack of proper maintenance will result in the overgrowth of these BMPs and reduce their proper function. With unchecked vegetative growth and sedimentation, the capacity of the BMP is reduced below the design criteria. In addition, the ability to perform a comprehensive inspection becomes difficult if not impossible. Some owners do not even know there is a stormwater BMP present due to the years of neglect, since it may appear to be a nice, wooded (often fenced) area in a corner of the property.

Typical violations for aboveground BMPs include:

  • Overgrown vegetation
  • Woody growth on dam faces
  • Sedimentation
  • Erosion
  • Animal burrows
  • Clogged rip rap
  • Pipe failure
  • Corrosion of corrugated metal pipe
  • Clogging of low flow orifice (turns a dry pond into a wet pond)
  • Failure to maintain inspection records

Belowground BMPs are more common in new developments where land prices are at a premium and in infill projects where the necessary surface area is unavailable. Belowground BMPs commonly include engineered structures designed to improve water quality, such as oil/grit separators, catch basins, vortex type units, cartridge units, detention structures, sand filters, infiltration structures, and others.

Table 1 Preventive BMP Maintenance Schedule for Routine Tasks
BMP Structure Type
Routine Task
Frequency
Wet Pond/Dry Ponds/Infiltration Trenches
Remove Trash/Debris for BMP and contributing area
Quarterly

Mow to 6?-8? grass height
Quarterly
Remove wood vegetation from dam and banks
Spring/Fall
Stabilize/Revegetate side areas
As needed
Repair embankment and side slopes
As needed
Fill animal burrows
ASAP
Wet Pond
Lubricate mechanical components
Annually
Underground Sand Filter
Remove Trash/Debris from contributing area
Quarterly

Ensure contributing areas are not sources of vehicle fluids
Quarterly
Service Fencing and locks
Annually
Repair of leaks from sedimentation chamber or deterioration of structural components
Annually or as needed
Stabilize/Revegetate contributing areas
As needed


Lack of proper maintenance of belowground BMPs is not as readily apparent as it is in aboveground BMPs. Clogging of many belowground BMPs can go unnoticed since many are designed to bypass once clogged. Many owners do not know that they have belowground stormwater BMPs until they receive a violation or encounter flooding or some other failure of the system. Most manufacturers have a recommended frequency for inspection and maintenance of their belowground BMPs that are incorporated into the Stormwater Pollution Prevention Plan (SWPPP) during the design of the project.
Typical violations for belowground BMPs include:

  • Sedimentation
  • Failure to clean the oil chamber
  • Clogging of internal trash racks
  • Clogging of low flow orifice
  • Failure to maintain inspection records

The key to a successful compliance strategy is a comprehensive preventive maintenance (PM) program. A PM program will ensure that the structures continue to operate as designed, maintenance covenants are followed, and overall property aesthetics are maintained. Elements of a PM program include both routine and non-routine tasks. Regular inspection should be performed in conjunction with routine maintenance tasks. Inspections will focus on identifying erosion, embankment failures, and overall operation of the BMP. Tables 1 and 2 identify routine and non-routine tasks that should be performed on typical BMPs. However, BMPs that have not been following a PM program for more that five years will likely require some level of rehabilitation. This often involves sediment and vegetation removal, repair of embankment and side slopes, and repair of control structures. Since this work can be costly, it is beneficial to start the PM program as soon as the BMPs are constructed.

Table 2 BMP Preventive Maintenance Schedule for Typical Non-Routine Tasks
BMP Structure Type
Task
Frequency
Wet Pond
Remove accumulated sediment/pollutants
5-15 years

Replace mechanical components
20 yrs
Reconstruct spillways and embankments
20-50 years
Control algae
When Identified
Remove invasive wetland vegetation
When Identified
Repair fencing
When Identified
Dry Pond/Infiltration Trenches
Remove accumulated sediment/pollutants
2-10 years

Dethatch grass to remove sediment buildups
2 years
Aerate compacted area to promote infiltration
2-3 years
Replace components, reconstruct embankments
20-50 years
Infiltration Trenches
Remove/replace top 6? of gravel
2 years

Remove accumulated sediment from main cells
20 years
Underground Sand Filter
Removed accumulated sediments from chambers
1-2 years

Remove and replace top few inches of sand
1-2 years
Replace filter media, replace underdrains
20 years
Replace concrete shell
20-50 years

Although stormwater management has not typically been on the top of the priority list for many commercial and industrial facilities, trends indicate that enforcement is increasing. While some large facilities may have in-house staff responsible for these activities, most owners rely on outsourcing to specialized firms to perform inspections, identify or correct problems, and institute the proper preventive maintenance programs.

This article originally appeared in the 11/01/2006 issue of Environmental Protection.

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