NPDES update: Watershed pollution diets

July 2011 » Exclusive
The Chesapeake Bay TMDL could be a policy model for nutrient and sediment pollution reductions across the country.
Eileen Straughan
Researchers use satellite measurements of ocean color to estimate the amount of microscopic plant life that lives in the Chesapeake Bay and other bodies of water. The kinds and amounts of plant life are indicators of the health of marine ecosystems.
NASA/Goddard Space Flight Center Scientific Visualization Studio

On Dec. 29, 2010, the U.S. Environmental Protection Agency (EPA) established the Chesapeake Bay total maximum daily load (TMDL), often referred to as the bay’s “pollution diet,” for nitrogen, phosphorus, and sediment. Despite 25 years of multi-state Chesapeake Bay Watershed Agreements and citizen actions to preserve and protect the bay, water quality and living resources continue to decline. In fact, there have been more than 11,700 separate localized TMDLs in the bay watershed, but implementation of these localized TMDLs has failed to produce improved water quality and living resources in the bay overall. The Chesapeake Bay TMDL was established as part of a settlement agreement reached with the Chesapeake Bay Foundation, elected officials, and sport-fishing and watermen associations after years of litigation charging that the EPA “had failed to take adequate measures to protect and restore the bay.”

The Chesapeake Bay TMDL addresses nutrient and sediment pollution for the entire Chesapeake Bay — an estuary with a 64,000-square-mile watershed covering part of six states and the District of Columbia. Based on EPA’s 2011-2015 Strategic Plan for improving the nation’s waters, the same water quality challenges faced in the Chesapeake Bay also are found in the Great Lakes, Long Island Sound, the Gulf of Mexico, Puget Sound, San Francisco Bay, U.S.-Mexico border area waterways, South Florida waterways, and other major water bodies. The Chesapeake Bay TMDL — and the watershed-based approach EPA is using to implement the TMDL — likely will appear in these areas in the future.

The pollutants to be trimmed via the TMDL pollution diet come from both point and nonpoint sources. The most notable point sources involve municipal and industrial wastewater facilities, and air emissions in the form of particulate matter stemming from the combustion of fossil fuels in power plants. Nonpoint sources include agricultural operations, urban and suburban stormwater runoff, septic systems, and pollutants from vehicle use. The actions needed to achieve the reductions necessary will involve the civil engineering community undertaking traditional infrastructure projects such as upgrading wastewater treatment plants with enhanced nutrient removal, repairing and rehabilitating sewer infrastructure, and retrofitting stormwater management facilities. It also will involve some nontraditional projects such as agriculture nutrient management plans, riparian buffers, cover crops, wetland creation, stream stabilization and restoration, green infrastructure, and micro-scale bioretention stormwater management.

The TMDL must reduce nutrients and sediment loadings released into the Chesapeake Bay’s watershed to levels necessary to achieve positive water quality indicators in each bay segment currently on the list of impaired waterways (the 303d list). Such water quality indicators include dissolved oxygen, water clarity, and submerged aquatic vegetation. Nutrient pollution in the bay leads to the growth of algae and subsequent algal blooms. These algal blooms impair aquatic ecosystems and lead to the decline in the amount of viable fish and shellfish.

The Chesapeake Bay TMDL must:

  • be based on information obtained from all of the jurisdictions in the bay watershed;
  • contain waste load allocations for point and nonpoint sources;
  • include reasonable assurance and an implementation framework that demonstrates nonpoint source load reductions will be achieved; and
  • include an allocation for new or increased permitted discharges of nutrients and sediment or a provision for offsets.

In addition to developing and implementing a Chesapeake Bay TMDL, the settlement agreement directs EPA to account for air deposition of nitrogen into the bay and its tidal tributaries within the load allocation portion of the bay TMDL.

The Chesapeake Bay’s 64,000-square-mile watershed includes portions of six states and the District of Columbia.
USDA Agricultural Research Service

Furthermore, the agreement requires EPA to publish the TMDL, its proposed waste load, load allocations, and supporting technical and policy assumptions for public review and comment. Under the National Pollutant Discharge Elimination System (NPDES) permit program, the settlement agreement requires EPA to review all proposed new or re-issued NPDES permits and determine whether the permits include effluent limitations consistent with achieving desired water quality standards for the bay. The review also includes the bay TMDL waste load allocations, watershed implementation plans, construction general permits drafted by the states, and municipal separate storm sewer system (MS4) permits. In addition, the settlement agreement includes the monitoring and tracking of progress toward achieving waste load reductions. Enforcement action will be taken via NPDES permits and implementation of additional programs as necessary to ensure progress toward achieving set milestones.

More than 40,000 TMDLs have been established in watersheds across the country since 1992, but the Chesapeake Bay TMDL is by far the largest and most complex. The TMDL requires a 25-percent reduction in nitrogen, 24-percent reduction in phosphorus, and 20-percent reduction in sediment loads to the bay by 2025. The Chesapeake Bay’s TMDL lifts the interaction between civil engineers and environmental scientists to the national stage.

Impervious surfaces — which impede stormwater infiltration and can negatively impact stormwater quality — compose about 17 percent of all urban and suburban lands in the Chesapeake Bay watershed.
Chesapeake Bay Program

State-by-state pollution diets
Each state in the Chesapeake Bay watershed must demonstrate how the reductions will be achieved through a watershed implementation plan (WIP), which must include the sectors, municipal and industrial wastewater treatment plants, septic systems, urban stormwater, and agricultural discharges that will provide the nutrient and sediment load reductions necessary to achieve the waste load allocations specified in the bay TMDL. The WIPs must address present nutrient and sediment sources, in addition to sources associated with planned future development. Nutrient and sediment load reduction strategies under consideration for inclusion in Phase II WIPs include the following:

  • expanding wastewater treatment plant upgrades to provide enhanced nutrient removal technology;
  • retrofitting untreated urban and suburban areas with stormwater management facilities;
  • requiring septic system upgrades to add nitrogen removal;
  • providing natural filters such as engineered wetlands and riparian buffers;
  • developing nutrient management plans and best management practices for agricultural land; and
  • performing stream restoration to reconnect incised streams to natural floodplains to reduce stream erosion and sediment deposition, and to restore hydrology to floodplain wetlands where natural sequestration of nutrients can occur.

While treatment plant upgrades clearly are in the wheelhouse of design engineers, the watershed assessments, environmental site design/low impact design for stormwater (ESD/LID), stream restoration design, wetland creation design, riparian buffer, and agricultural best management practices will require more collaboration between design engineers, environmental scientists, and landscape architects.

To date, EPA has published the bay TMDL and issued preliminary waste load allocations to the bay jurisdiction states according to the major river basins in the watershed. The waste load allocations are based on a model of the bay that originally was developed in the 1980s and has been refined and updated continuously. The states received a revised set of waste load allocations last month, which will form the basis of the Phase II WIPs due back to EPA by Nov. 1, 2011, according to the settlement agreement.

Map shows 2007 sediment pollution reductions by percent of goal for each state-basin, estimated by state-reported BMP applications and efficiencies. Reductions are estimated by the Phase 4.3 Chesapeake Bay Watershed Model.
Chesapeake Bay Program

Maryland is actively engaged with the local jurisdictions regarding the schedule and content expectations for the Phase II WIPs. The state has passed the preliminary waste load allocations along to each local jurisdiction in the watershed, advising the jurisdictions to quantify baseline (2009) pollutant loadings and identify actions that will be taken to bring about the required reductions and how those actions will be funded. EPA is required by the settlement agreement to assess the adequacy of the local jurisdiction WIPs and take action through permit enforcement if the WIPs are insufficient to achieve the targeted reductions.

The estimated costs of compliance with the bay TMDL and the waste load allocations at the local level are daunting. For example, Montgomery County, Md., estimates a total cost of 1.8 billion dollars for capital projects such as urban stormwater retrofits and stream restoration. In addition, funds are required for an unprecedented level of public outreach necessary to coordinate and communicate with stakeholders in the county to achieve the necessary reductions. The county plans to expand its existing water quality protection fee and issue bonds to fund the projects.

As the first jurisdiction in Maryland to see significant changes to its MS4 permit, Montgomery County would be required to retrofit 20 percent of existing impervious surfaces with stormwater management. This is in addition to the 10 percent retrofit requirement in its previous MS4 permit. Other Maryland jurisdictions and federal properties in the Chesapeake Bay’s watershed have older MS4 permits with no retrofit requirements. Maryland Department of the Environment staff encourages other jurisdictions and federal properties to look at Montgomery County’s MS4 permit conditions and expect the same or similar requirements as their MS4 permits renew.

U.S. Department of Agriculture Agricultural Research Service soil physicist Ali Sadeghi (left) and landowner Bill Collier examine water quality in a ditch under controlled drainage management within the Choptank Watershed. This monitoring information will be used for calibration and modification of watershed models such as Soil and Water Assessment Tool (SWAT) for application to similar watersheds within the Chesapeake Bay.
USDA Agricultural Research Service/Peggy Greb
  Wetland and streamside vegetation serves as a buffer to filter excess nutrients from water running off agricultural land.
USDA Agricultural Research Service/Scott Baue

Reaching the goal
The Chesapeake Bay is recognized as a “national treasure” by the Chesapeake Bay Executive Order 13508, and is on the forefront of nutrient pollution science and prevention policies. EO 13508 also placed a federal leadership team composed of representatives from EPA, Agriculture, Commerce, Defense, Homeland Security, Interior, and Transportation at the forefront of developing a coordinated strategy “to protect and restore the health, heritage, natural resources, and social and economic value of the nation’s largest estuarine ecosystem and the natural sustainability of its watershed.”

The National Research Council of the National Academy of Sciences (NAS) recently released a pilot study that contains science-based conclusions and recommendations to help the Chesapeake Bay Program evaluate its efforts to achieve nutrient reduction goals and clean up the bay. The study, “Achieving Nutrient and Sediment Reduction Goals in the Chesapeake Bay: An Evaluation of Program Strategies and Implementation” (, validates and provides constructive feedback on the work the bay program has undertaken during the last 18 months to improve accountability.

The NAS report states that nearly all states have insufficient information to evaluate their progress in reducing nutrient pollution, limiting their capacity to make midcourse corrections. Additionally, tracking and accounting issues lead to an incomplete and possibly inaccurate picture of the bay jurisdictions’ overall progress in meeting program goals.

Another main concern of the report’s authoring committee is the possibility of overly optimistic expectations among the public. While science and policy communities generally recognize the inherent uncertainties in modeling water quality, the general public “will almost certainly be frustrated” if they expect visible, tangible evidence of local and bay water quality improvements in short order. Legacy effects of nutrient pollution already in the Chesapeake Bay watershed will significantly delay results from the program’s efforts. For more information, including a link to a report in brief, visit the National Academy’s website at item.aspx?recordid=13131.

One of the most important tools necessary to achieve the Chesapeake Bay’s TMDL goals exists with civil engineers who design the infrastructure necessary to balance the needs of society with those of the natural environment. Civil engineers must ensure that infrastructure is amenable to such needs and are essential to the implementation brought about by this settlement agreement.

Based on EPA’s 2011-2015 Strategic Plan for improving the nation’s waters, other major water bodies face the same water quality challenges as the Chesapeake Bay. The Chesapeake Bay TMDL — and the watershed-based approach EPA is using to implement it — will serve as a model for future water quality improvement plans.

Status of effluent limitation guidelines
Since 2009, the construction and development community has been awaiting a final decision by the U.S. Environmental Protection Agency (EPA) pertaining to effluent limitation guidelines (ELGs). The EPA’s initial guidelines went into effect in February 2010, outlining requirements for sediment and erosion control measures at construction and development sites. Within the guidelines was a limit of 280 nephelometric turbidity units (NTUs) for discharges from construction sites disturbing more than 20 acres that would take effect in August 2011; by 2015 the ELGs would apply to construction sites of 10 acres or more. Discharges from sediment control devices on larger construction sites would have to be sampled to demonstrate compliance with the 280-NTU limit.

In response to the promulgated limit of 280 NTUs, petitions were filed requesting a re-evaluation of NTU limits. According to a memo released by the EPA, the petitions called attention to a “potential error in the calculation of numeric limits.” EPA responded to the petitions noting that the limits were “improperly interpreted” and issued a stay of said limits. The stay temporarily tabled the 280-NTU limit “pending the correction of calculations” by the EPA.

A final rule regarding NTU limits reportedly was expected by May 30, 2011, ensuring the revised NTU limits would be incorporated in the construction general permits (CGP) expected to take effect on June 30, 2011. In light of EPA’s decision, states are finding themselves held in legal limbo with respect to the issuance of CGPs. For example, Maryland’s Department of the Environment has suspended issuance of CGPs until a final decision is made by EPA regarding ELGs. Currently, EPA is proposing to extend the existing CGPs to Jan. 31, 2012, allowing more time to resolve the 280-NTU limit.

Editor’s note: The August issue of CE News will include more information on ELGs and their impact on the industry.

Eileen Straughan is president and founder of Straughan Environmental ( Alisha Sutton is an environmental scientist with Straughan Environmental.

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