Detailed Engineering Services

Discharge Mixing Zone Study, Requirements and Modeling

LEA has a complete suite of mixing zone study techniques, regulatory policy experience and field support. We understand effective evaluation of receiving water conditions resulting in balanced NPDES permit limits. Missed opportunities and unnecessary pollution are the typical result when MZ studies are not accurately performed. Indeed, considerable alternative treatment costs can occur when outfall design is carried out based on faulty MZ analysis. LEA understands facility design implications and benefits of successfully evaluating receiving water conditions through MZ analysis. We use US EPA distributed and approved mixing zone models Visual Plumes and PLUMES, as well as CORMIX (no longer supported by EPA Center for Exposure Assessment Modeling). Integration with our river and marine field capabilities are fully discussed in the items below.

TMDL - Total Maximum Daily Load
Review, Analysis and Response

Dischargers and stakeholders usually see newly issued waste load allocations (WLA) at the end of complex and far-reaching basin TMDL studies performed by regulatory agencies. Typically, water quality modeling in the context of intricate environmental requirements and indistinct TMDL policy is performed with considerable impacts on affected parties. LEA helps sort through
these issues allowing you to focus on key water quality elements
most affecting you, your watershed and facilities. LEA's
supporting water quality modeling and review capabilities
are discussed below.

Water Quality Field Study for Rivers and Marine Conditions

Field study support for mixing zone and basin WQ evaluations can result in reduced discharge effects and notable facilities costs savings. When field data is not available to aid water quality study, regulators will make critical assumptions that may not be bourn out in the field. LEA has full capability in performing required field investigations to balance abstract modeling assumptions with real world conditions. Our Hydrolab water quality probe has the capability of measuring numerous parameters in-situ including temperature, pH, dissolved oxygen (DO), conductivity, turbidity and depth. Our Swoffer flow current meter is oftentimes critical in assessing water quality conditions. Our conductivity and dye study qualifications enable LEA to map mixing zones or determine basin travel times. These and many other scientific tools are at our disposal to help pinpoint key information in your WQ project.

River & Marine Water Quality Evaluation,
Modeling & Compliance

LEA’s receiving water quality capabilities support many facility planning, treatment design, facilities costs comparison and pollution effects studies. LEA is fully enabled in all the widely used and US EPA accepted hydrodynamic and Water Quality Models. Our model and review capabilities include the steady-state one-dimensional EPA QUAL2E, the dynamic multi-dimensional EPA WASP/ DYNHYD, the dynamic one-dimensional Corps CE-QUAL-RIV1, the dynamic two-dimensional COE CE-QUAL-W2, and many other WQ models.

Wastewater NPDES Permit Writing, Review and Response

LEA staff has considerable experience in National Pollutant Discharge Elimination System permit writing, review and response. We have a clear understanding of the effect of permit limits, monitoring, reporting and compliance on facility costs and operation, and receiving water quality. LEA can help ensure NPDES permits are fair and balanced.

Thermal Discharge Analysis and Temperature Management Plans (TMP)

The effect of effluent temperature on receiving water is a growing concern for many dischargers and basin stakeholders. LEA has specialized experience in thermal discharge analysis including receiving water stratification and other density current effects. In the some cases, dischargers may be required to develop and submit a Temperature Management Plan if they discharge to (or upstream of) a waterbody that is water quality limited, i.e., 303(d) listed, for temperature. Key considerations for determining TMP requirements depend on the basin WQ status, presence and life stages of salmonid and other fish species, effluent temperature discharge characteristics and temperature mixing zone conditions in the receiving water. If measurable increases in temperatures are demonstrated in the TMP, or temperature loading exceeds a TMDL established waste load allocation, analysis of facility practices to reduce effluent temperatures to permitted limits may be required. LEA has expertise to meet all the requirements of developing a TMP and assisting in plan implementation.

River and Marine Outfall Diffuser Design

Facility effluent treatment requirements are critical considerations affected by the outfall design. LEA staff is experienced in diffuser design and can fully optimize the diffuser for any discharge site. Effective outfall diffuser design minimizes surprises and risks. Our experience for in-water design and construction requirements is strategic in gaining regulatory approval. We have worked directly with the agencies that approve in-water projects including the U.S. Environmental Protection Agency, the United States Corps of Engineers, NOAA Fisheries, U.S. Fish and Wildlife, State Fish and Wildlife Agencies, and state environmental agencies.

Alternative Effluent Treatments and Costs Analysis

The effect of receiving water conditions on effluent treatment alternatives and costs can be substantial. At LEA we have extensive experience evaluating potential treatment alternatives and costs as outcomes to receiving water conditions. We have capabilities in alternative disinfection evaluation; biochemical oxygen demand (BOD), ammonia and dissolved oxygen (DO) treatment alternatives; nutrient reduction alternatives; and others. We provide our alternatives analysis with a costs and benefits breakdown so that dischargers and basin stakeholders can compare for themselves the outcome of various treatment scenarios.