Water Quality Standards - Aquatic Toxicology - NPDES Permit Limits

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Water Quality Standards - Aquatic Toxicology - NPDES Permit Limits

Discussion of a variety of topics related to State and Federal Water Quality Standards, Ambient Water Quality Criteria, Sediment Criteria, NPDES & Site-specific Discharge Standards, Water Quality Management, Aquatic Toxicology, Aquatic Community Impacts, and Water Quality Assessment

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Numeric Nutrient Water Quality Criteria Requirement for FL

The US Environmental Protection Agency (EPA) has recently announced that the agency is taking actions to develop the required Nutrient Water Quality Criteria within the State of Florida. These actions include EPA issuing a formal determination under the Clean Water Act that “numeric” nutrient water quality criteria are necessary in Florida, and Florida needs to accelerate its efforts to adopt numeric nutrient criteria into state regulations.

EPA believes that water quality degradation from nutrient pollution is a significant issue in Florida. Florida’s 2008 Integrated Water Quality Assessment estimated that at least 1,000 miles of rivers and streams, 350,000 acres of lakes, and 900 square miles of estuaries are impaired by nutrients. The new numeric nutrient water quality standards will help the Florida Department of Environmental Protection (FDEP) improve the efficiency and effectiveness of its water quality management tools, identify waters impaired because of nutrient pollution, establish total maximum daily loads and Basin Management Action Plans, and derive National Pollutant Discharge Elimination System permit limits.

EPA expects to propose numeric nutrient standards for lakes and flowing waters within 12 months, and for estuaries and coastal waters within 24 months.

Caltha LLP provides expert technical support to clients nationwide to address State water quality standards. Caltha provides specialized expertise in biomonitoring, aquatic toxicology and impacts to aquatic communities.

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Biomonitoring Requirements - Amendment to OK Rules

The Oklahoma Department of Environmental Quality (ODEQ) is proposing to modify its rules concerning biomonitoring (whole effluent toxicity, or WET) requirements for wastewater dischargers. Under the proposed rules, a sublethal test failure (failure to demonstrate growth or reproduction) will be handled the same as a lethal test failure (death to the test organisms). This change is required based on changes in US EPA requirements and has already been promulgated into Oklahoma’s Water Quality Standards.

The proposed rule modifications also refine when a facility may request a biomonitoring organism change from Daphnia pulex or Ceriodaphnia dubia to Daphnia magna. Finally, the proposed rule modifications would also require monthly monitoring for phosphorus and/or nitrogen if a facility is discharging to a nutrient limited watershed as designated by Oklahoma’s Water Quality Standards.

Caltha LLP provides expert technical support to clients nationwide to address State water quality standards. Caltha provides specialized expertise in biomonitoring, aquatic toxicology and impacts to aquatic communities.

[Click here to request further information on aquatic toxicology and aquatic community impact assessment]

For further information contact Caltha LLP at
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Stormwater Effluent Limits For Industrial - MS4; Are These Next?

US EPA has recently proposed effluent limits for stormwater discharges from larger construction sites. [Read more about Construction Stormwater Discharge Limits]. This has prompted many industrial and municipal stormwater permitees to speculate on whether or not similar effluent limits will be proposed under Multi-sector General Permits (MSGP) or MS4 permits.

The simple answer is that almost anything is possible.

However, the establishment of construction site effluent limits has some important differences that may not allow easy transfer of the same effluent limits to industrial or MS4 permits.

1. Effluent limits are based on a specific stormwater treatment method that is added to the stormwater treatment pond requirements for smaller sites. Without the requirement to install a pond, the additional treatment may not be economically-feasible. Unless specific structural BMPs, like ponds, are required for industrial or MS4 dischargers, it would be difficult to translate the construction site effluent limits. Because of the nature of industrial and MS4 discharges, requiring treatment ponds would be difficult.


2. In general, the variety of activities and stormwater handling practices associated with industrial and MS4 discharges will be significantly broader compared to construction sites. Therefore, again, translating the proposed effluent limits to industrial and MS4 dischargers would be difficult.

Given these factors, it may be difficult to demonstrate that similar Best Available Technology used to calculate effluent limits for construction site discharges could be equally applied to other types of discharges.

Caltha LLP provides expert technical support in permitting and compliance with State and Federal stormwater permits. To request a quote of services on-line, go to Caltha Stormwater Quote Page.

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EPA Proposed Stormwater Eflluent Limits - Comparison To Benchmark Concentration

In December 2008, US EPA published proposed effluent limits for stormwater discharges from construction sites. [Read more about proposed limits] The proposed rules included a numeric effluent limit of 90 NTU. NTUs are a standard measurement of turbidity in water. Turbidity is a measurement of suspended material in the water.

Benchmark values and previous stormwater effluent limits have always been expressed as Total Suspended Solids (TSS). Turbidity is related to TSS, however the relationship between turbidity and TSS is not always direct, and will be affected by a number of different factors.

Stormwater benchmark concentrations for TSS usually range from 100 to 250 mg/L. Using a few typical conversions between NTU and TSS, it is predicted that an effluent limit of 90 NTU will be roughly equivalent to 45 to 65 mg/L expressed as TSS. Therefore, it is projected that the proposed stormwater effluent limit is about one-half the lowest current benchmark concentration for TSS.

Caltha LLP provides expert technical support to dischargers subject to State and EPA stormwater discharge permit, including permitting, SWPPP training, stormwater monitoring, site inspections, and overall compliance program development.

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Stormwater Effluent Limits On Construction Site Discharges

On November 28, 2008, US EPA published its proposed revision to the federal requirements on stormwater discharges from construction sites. The key departure in the current proposal from existing requirements is the establishment of New Source Performance Standards (NSPS) and numeric effluent limit guidelines (ELG) that will apply to construction sites.

[Read more about the difference between "effluent limit" and "stormwater benchmarks]

[Read more about typical concentrations in stormwater compared to limits]

In June 2008, US EPA published its final general stormwater discharge permit for construction sites. US EPA’s intent is to issue a revised general permit once these new effluent limits are promulgated.

The current proposed rule addresses controls based on size of the construction site:

1. Less than 10 acres. Controls are similar to current approaches.
2. Greater than 10 acres. Sites greater than 10 acres will need to install temporary sediment basins meeting specific design criteria.
3. Greater than 30 acres. For large sites, discharges will need to monitor stormwater discharges and must meet a turbidity effluent limit of 13 nephelometric turbidity units (NTU). The effluent limit of 13 NTU is based on the determination that the Best Available Technology (BAT) has been demonstrated to meet this limit. In this case, the BAT is active treatment on-site using injection of polymer into the stormwater to improve precipitation of smaller particles.
   

Does this mean that all large construction sites will need to install active stormwater treatment systems? Not necessarily. Large sites subject to the effluent limit of 13 NTU will need to meet that limit. Sediment basins alone may not be capable of meeting this limit, and if so active treatment, including enhanced precipitation using chemical addition, may be required.

Once the US EPA finalizes the effluent limits for large construction sites, State general permits will likely include these permit limits as they are reissued. US EPA is accepting comments on the proposed Rule through February 26, 2009.


Caltha LLP assists dischargers as they evaluate and address regulatory obligations under State and Federal stormwater permits.

For further information contact Caltha LLP at
info@calthacompany.com
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