Floatables Control is Surfacing Again, What Can You Do?
- C. D. Courter, Hazen and Sawyer
- B. Vatter Sanitation District No. 1 of Northern Kentucky
Over 700 U.S. cities in more than 30 states have combined sewer systems, which, by design, discharge diluted raw sewage into many of the nation’s waterways. Now three decades have passed since the Clean Water Act was enacted and federal and state regulatory agencies have refocused their efforts to address the water quality issues of our nation’s lakes, streams and rivers. In part because of the United States Environmental Protection Agency’s (USEPA) landmark 1994 Combined Sewer Overflow (CSO) Control Policy and their Guidance for Nine Minimum Controls (NMCs), and in part because they are the most visible, the communities and authorities responsible for operation and maintenance of wastewater collection systems continue to be the primary target for enforcement. In recent years there has been a flurry of Consent Orders and other similar legal agreements (Orders) requiring wastewater collection system operators to eliminate sanitary sewer overflows (SSOs) and bring CSOs into compliance with the CSO Control Policy. Of the Orders that address CSOs, many include provisions to re-evaluate the authority’s NMC compliance and more particularly, control of floatables. As a prime example, the Orders recently entered into by the Allegheny County Sewer Authority (ALCOSAN), and the 83 municipalities served by ALCOSAN, including Pittsburgh, require “an assessment of the types and amount of solid and floatable materials…entering the receiving waters, and an evaluation of the environmental and aesthetic impact of those solids and floatables upon those receiving waters, including Sensitive Areas”. In another example, EPA Region IV and the State of Kentucky have finalized Orders with all 17 of the CSO communities in Kentucky in the last two years. These orders all require the submission of Reports detailing the communities’ NMC compliance and what is to be done if not in compliance.
This latter set of Orders led Louisville Metropolitan Sewer District (MSD), the first Kentucky sewer district required to submit their NMC compliance documentation under these orders, to submit compliance documentation detailing their numerous early action solids and floatables control projects including street sweeping, catch basin inserts, proprietary manufactured screening controls and engineered controls such as a baffle chamber.
Louisville’s original program was similar to what many others around the country have traditionally included; solids and floatables controls constituting installation and operation of controls at only a small percentage of outfalls. In other areas such as New York City, Washington D.C., and Detroit, capture by skimmer boat or by boom in the water course continue to be viable options. In both cases it is argued that numerous constructed controls at every outfall are considered too costly to be a minimum control. These communities have left the remaining outfalls to be addressed during future long term control planning.
However, Louisville’s program was not accepted as submitted, because it left many overflow points without control. In response, Louisville MSD moved quickly and installed some type of simple solids and floatable control, consisting mainly of wooden baffles and coarse bar racks, at every outfall or diversion where feasible. As a result, Sanitation District No. 1 of Northern Kentucky (SD1), the next Kentucky sewer authority to submit on compliance and the second largest CSO authority in USEPA Region IV is adopting a similar program. However, before moving forward with installing these controls at all outfalls, SD1 has developed and initiated a pilot program to look at the effectiveness and O&M requirements of a range of simple solids and floatables controls, including baffles, baffle-weirs, two types of bar racks (Exhibit 1), small scale (non-proprietary) net bags, and several proprietary products including a Nutrient Separating Baffle Box (never before applied to CSO) by Suntree (Exhibit 2) and the Littertrap by GNA. Once the pilot is complete, SD1 will utilize the information to develop an effective system-wide program to address as many of their 96 CSOs as is feasible. The primary goal of this program is to limit the cost and O&M burden while complying with CSO Control Policy and the narrative water quality standards governing solids and floatables. Results of the pilot will be available in February 2008 and the final simple solids and floatables control program is projected to be completed by the end of 2008.
For a copy of the full paper, please contact the author at firstname.lastname@example.org
Hear about new publications with our email newsletter
Horizons showcases significant water, wastewater, reuse, and stormwater projects and innovations that help our clients to achieve their goals, and can help you achieve yours. Articles are written by top engineers and process group leaders, demonstrating and explaining the beneficial application of a variety of technologies and tools.