Economical Storage For Industrial Stormwater Treatment Plant

Dec. 12, 2002
In 1990, the United States Environmental Protection Agency implemented stormwater runoff regulations in an attempt to control the pollution discharged into our nation?s streams. Under the regulations, municipalities and a wide variety of industrial activities are required to obtain discharge permits, known as National Pollution Discharge Elimination Systems (NPDES) permits. One of the nation?s leading wood-preserving companies, J. H. Baxter takes their environmental responsibilities seriously. The company?s Environmental and Safety Department is devoted exclusively to meeting those responsibilities. To comply with EPA stormwater treatment regulations, J. H. Baxter designed a surface water collection and treatment facility on their 42-acre site in Eugene, Oregon. The facility included a stormwater storage tank and a Stormwater Treatment Plant (SWTP). Based on surface runoff calculations, one 1 million-gallon tank was required for the storage of stormwater prior to treatment. The project engineers selected Environetics? PortaTank? to store the collected stormwater because it met their engineering standards and provided the most cost effective storage solution. Several unique PortaTank features factored into the engineer?s selection criteria. First, the precision fabricated bolted steel tank shell allowed for rapid field assembly, dramatically reducing installation costs. Second, the high performance geomembrane liner system provided resistance to the chemicals present in the stormwater runoff. Furthermore, the patented tank design eliminated the considerable time and cost associated with building a conventional concrete foundation. Last but not least, the PortaTank complied with the American Water Works Association (AWWA) D103-97 tank engineering standards and the stringent Seismic Zone 3 installation requirements. The Stormwater Treatment Plant was designed with an average treatment rate of 63 gpm and a maximum treatment rate of 225 gpm. The plant treats the stormwater for pentachlorophenol, copper, zinc, arsenic, pH, and suspended solids prior to discharge. Working at full capacity, the SWTP rendered a maximum collection and storage rate of 2,240 gpm. The working capacity of the SWTP, along with the 1 million-gallon stormwater storage capacity, met or exceeded all of the requirements of the NPDES permit. In 2001, J.H. Baxter expanded their existing Stormwater Treatment Plant to meet the increased demands of the revised NPDES permit requirements. Surface runoff volume for a 24-hour, 25-year storm was calculated to be approximately 3 million gallons. Modifications were made to the SWTP to increase the average flow rate from 63 gpm to 175 gpm. Environetics installed two new PortaTanks, a 1.3 million-gallon tank, 129 feet in diameter and 13'-6" high, and a 1 million-gallon tank, 129 feet in diameter and 10'-10" feet high. Both of the new storage tanks were fully installed in only 10 days. The new PortaTanks complete the current phase of the treatment plant upgrade, providing safe, cost effective storage for a total of 3.3 million gallons of stormwater runoff.