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WIP Phase III MS4 NPDES Permits

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Phase III WIP (Watershed Implementation Plan)

The Phase III Watershed Implementation Plan (WIP) is the next part of the EPA-required 3-phase planning process to achieve clean-up goals for the Chesapeake Bay by 2025. This initiative is important because it provides the road map and accountability framework to steer the State toward cleaner local streams and a healthier Chesapeake Bay. It should be noted that participation in the WIPO III is a voluntary. The intent is to utilize the NPDES permit initiatives to address some of those desired improvements.

In 2010 the U.S. Environmental Protection Agency (EPA) set limits on the amount of nutrients and sediments that can enter the Chesapeake Bay. In addition to setting these limits, known as Total Maximum Daily Loads (TMDLs), EPA required the Bay states to developed statewide Watershed Implementation Plans. The Phase III WIP allocates the allowable load among different sources and identifies statewide strategies for reducing nutrients and sediments that impair the Chesapeake Bay. The Executive Summary of Maryland's Phase III WIP further explains the rationale for the plan. Maryland’s WIP Plan provides a series of proposed strategies that will collectively meet the 2025 targets. Maryland’s 2025 pollution reduction targets for bay restoration are 45.8 million pounds total nitrogen (TN) and 3.68 million pounds of total phosphorus (TP). In meeting the targets, the state will also meet its sediment goals. These 2025 nitrogen and phosphorus targets were calculated to include increased pollution impacts expected from growth in human and livestock populations through 2025. In April of 2019 the State published its Phase 3 WIP III on August 23, 2019.

The Phase III WIP Plan builds upon lessons learned in Phase I and II, and charts a course to 2025 t Maryland agencies met with county public works and planning departments, municipalities, soil conservation districts, NGOs, and the public to better understand which restoration strategies are working, which are not, what additional plans and restoration actions are anticipated between now and 2025, and where resources and collaborations are needed to achieve them. This information was compiled, along with information regarding local pollution sources, progress to date and any pollution reductions required by permit or contract, into local summaries that establish local planning goals. These local goals combined with state-level pollution reduction strategies are projected to achieve Maryland’s 2025 Chesapeake Bay restoration targets.

TMDL goals are indirectly addressed in the following section on the County’s obligations under the State’s required general NPDES permit as follows and additionally described below:

Total Maximum Daily Loads (TMDLs)


Since 1972, Section 303(d) of the federal Clean Water Act has required states to identify waters that do not meet water quality standards and publicly report them on a list published every two years. For each of the listed waters, states are to determine the maximum amount of pollution that the waters can withstand and still meet standards. This maximum amount of pollution is called a Total Maximum Daily Load (TMDL). The Clean Water Act required Maryland to establish Water Quality Standards (WQS) for its waters and TMDLs that meet WQS for each listed waterbody,

In 1996, the U.S. Environmental Protection Agency (EPA) listed certain sections of the Virginia portion of the Chesapeake Bay as "impaired". Maryland listed all the upper Chesapeake Bay tidal water segments as not meeting standards for phosphorus, nitrogen (nutrients) and sediments.

What is a TMDL?>

Total Maximum Daily Loads (TMDLs) are a requirement, found in §303(d), of the federal Clean Water Act (CWA) that became law in 1972. A TMDL (Total Maximum Daily Load) is an estimate of the maximum amount of an impairing substance or stressor (pollutant) that a waterbody can assimilate without violating Water Quality Standards. This total load includes pollutants that come from the end of a pipe (point sources), stormwater runoff and groundwater flow (nonpoint sources), and a " margin of safety" that provides a cushion needed because of uncertainties associated with estimates. A TMDL also may include an allowance for future increases in pollutant loads due to changes in land use, population growth, and the expansion of business activity.

What are the benefits of TMDLs?

Maryland’s cultural heritage is closely tied to its rivers, coastal waters and the Chesapeake Bay. The seafood industry, recreational activities and the quality of life for Maryland’s citizens depend on the quality of our waters. Maryland’s waters are currently managed using "water-quality-based permits", which place limits on the discharge of wastewater to ensure receiving waters will remain "fishable and swimmable". As part of the Chesapeake Bay Agreement, Maryland also has defined upper limits on the amount of nitrogen and phosphorus that may go into the Bay. TMDLs formalize these procedures for setting upper limits on pollutants and create a framework to ensure cleaner waters for future generations. The Maryland Department of the Environment (MDE) web site’s Maryland TMDL Data Center provides identification of all the established TMDLs for the state. At this time there are no specific TMDLs for nitrogen or phosphorus identified for St. Mary’s County.

Chesapeake Bay Watershed and the WIP

Maryland was the first State in the watershed to require environmental site design to reduce stormwater runoff on all new development approved after May of 2010. Maryland has also implemented one of the most progressive sets of stormwater requirements for a MS4 permit in the Country.

EPA provided its expectations for the jurisdictions’ Phase III WIPs to maintain accountability in the work under the 2010 Chesapeake Bay Total Maximum Daily Load (Bay TMDL), encourage continued adaptive management to the new information generated during and after the Bay TMDL 2017 midpoint assessment, and lay the groundwork for implementation of the next generation of innovative practices. In addition, the Principals’ Staff Committee (PSC) established expectations for how to account for changed conditions due to Conowingo Dam infill, climate, and growth. These expectations are directed toward ensuring that the seven jurisdictions, and their local, regional, and federal partners have all practices in place by 2025 that will achieve the Bay’s dissolved oxygen, water clarity/submerged aquatic vegetation, and chlorophyll-a standards.


National Pollution Discharge Elimination System (NPDES) Small Municipal Storm Sewer System (Phase II MS4) Permit Coverage

In April of 2018 the Maryland Department of the Environment (MDE) issued the County a letter designating St. Mary's County for coverage under the State’s NPDES General Discharge Permit Number 13-IM-5500. This coverage became effective on October 31, 2018 when the County issued its Notice of Intent (NOI) to comply with the permit requirements for the extent of its 5-year term. Under the MS4 permit, MS4 owners and operators covered under this general permit must manage, implement, and enforce management programs for controlling all stormwater discharges in accordance with the CWA (Clean Water Act of 1972) and corresponding stormwater NPDES regulations, 40 CFR § 122, to meet the following requirements:

  1. Effectively prohibit pollutants in stormwater discharges or other unauthorized discharges into the MS4 as necessary to comply with Maryland’s receiving water quality standards;

  2. Attain applicable wasteload allocations (WLAs) for each established or approved Total Maximum Daily Load (TMDL) for each receiving water body, consistent with Title 33 of the U.S. Code (USC) 1342(p) (3) (B) (iii); 40 CFR § 122.44(k) (2) and (3). and

    Note that Part V of the Phase II MS4 permit states that development and execution of the impervious surface restoration project schedule constitutes adequate progress toward compliance with Maryland’s receiving water quality standards

  3. Comply with all other provisions and requirements contained in this general permit, and in plans and schedules developed in fulfillment of this permit.

Urbanized Area Assessment of Unmanaged Impervious Surface

The impervious area assessment is intended to provide a baseline for determining how much restoration will be required through 2025 to meet the mandated 20% restoration requirement. This requires the following actions steps

Determine the total amount of Land area and impervious area in the U. A. within the jurisdiction of St. Mary's County.

  1. Categorize the existing SWM facilities by Stormwater Design Era.
  2. Delineate and verify all areas treated to the One-inch water quality requirement.
  3. Review the SWM facilities not installed to the 2001 guidelines to determine if partial water quality treatment is obtained.
  4. Determine impervious areas receiving water quality treatment using non-structural methods. (Disconnects etc.)
  5. Determine the total amount of Unmanaged Impervious area.
  6. Determine 20% of the unmanaged area.
  7. GIS mapping of all the above.
  8. Develop a scope of work, aligned with County priorities, which can provide the requisite amount of restoration required.
  9. Provide a schedule and budget sufficient to meet these goals

MS4 Permit Programmatic Compliance Elements

The six minimum control measures are:

  1. Public Education and Outreach
  2. Public Involvement and Participation
  3. Illicit Discharge Detection and Elimination (IDDE)
  4. Construction Site Stormwater Runoff Control
  5. Post Construction Stormwater Management

The permit term for the County's obligations under the current Phase II MS4 permit runs from November 1, 2018 through October 31, 2023. An additional follow on permit is anticipated, the exact scope of that permit is unknown at this time but is anticipated to at the minimum require additional unmanaged impervious surface stormwater management restoration efforts.

Phase II MS4 Permit Year 2 Progress Report

Part VI of the NPDES General Discharge Permit Number 13-IM-5500 identifies the Record keeping and reporting requirements required of the County in order to verify it's compliance with the permit.

The Year 2 Progress Report consisted of the following Sections which can be reviewed by opening the associated links with their titles:

As a result of the work done analyzing the current County conditions and allowable credits for work already addressed, the current reporting identified that, as long as the County can maintain the condition of the current credited practices, no additional restoration projects should be required through 2025. In practice a continual compliance assessment is necessary to ensure this remains the case and additional programmatic verification steps as well as adverse condition corrections (some of which are identified in the States Comment letter on the year 1 submittal) will be necessary to maintain this position.

Comment Submission Form

The public is invited to review the document submissions and offer any comments they feel should be factored into future review and reporting.

All information received will be considered, and responses will be provided for those that provide contact information. A list of Frequently Asked Questions/Comments will be collated and added to the web page later, absent any personal information related to respondents.

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