Construction and operation of the new City of Somerton (the City) Wastewater Treatment Plant (WWTP) supports the City’s economic development, assists the City with continued growth, and resolves specific human health and environmental issues. The old lagoon treatment facility frequently discharged less than optimal effluent as a result of overload at peak flow rates. With a series of three continuous-flow aerated and facultative lagoons, the previous lagoon system could not meet NPDES permit discharge limit requirements on a consistent basis, especially during peak flow rates. This condition limited the City’s growth and development. Ultimately, it was deemed necessary to construct a new WWTP.
Phase I Construction of the Somerton WWTP Lagoon Replacement Project was completed in November 2003. It included closure of the polishing lagoon, construction of bypass piping and the installation of equipment required for interim operations. Technology for the new plant will to replace the existing lagoon system with sequencing batch reactors (SBR).
Completion of the new WWTP, currently under construction, is anticipated in the first quarter of 2006. During construction, Somerton is operating two of the three lagoons with added surface aeration and a flow curtain to minimize short circuiting. The new WWTP will provide for 0.8 million gallon per day (gpd) of biological treatment, a 30% increase in capacity over current average wastewater flow conditions. The new WWTP includes expandability to 1.6 mgd capacity in 0.2 mgd increments on the 1.5 acre area site, formerly known as Lagoon No. 3. Closure of the two remaining lagoons is planned upon completion; start-up and commissioning of the new WWTP will provide the City with an additional 12 acres of land for various municipal uses and/or economic development projects.
This paper will provide a project overview of the City’s WWTP Lagoon Replacement Project and discuss issues of negotiating through this multifaceted regulatory framework. Topics include the permitting issues, economic limitations and requirements, and the funding entities and mechanisms explored and/or utilized in order to make the project move forward that include Border Environmental Corporation Commission (BECC), North American Development Bank (NAD Bank), Department of Agriculture - Rural Development (RD), and the Water Infrastructure Finance Authority of Arizona (WIFA).
The City of Somerton, Arizona (the City) with a current estimated population of 9,710 lies in South Yuma County. It is 10 miles southwest of Yuma, 12 miles north of the Arizona-Mexico border, and 180 miles east of San Diego. The City is predominately low income. Its growing wastewater flow is attributed to a growth rate of about 4 percent and a growing influx of seasonal farm workers. This has taxed the existing lagoon wastewater treatment system. At peak flow rates the lagoon treatment system would not meet National Pollutant Discharge Elimination System (NPDES) permit discharge limit requirements. This necessitated replacement of the lagoon treatment system.
The Somerton’s Public Works Department is responsible for managing the city’s wastewater system and currently provides service to 2,106 accounts. The old wastewater treatment facility was constructed in the 1950s then upgraded in the early ‘80s with the installation of an aeration system and a chlorine contact tank (See Figure 1). The total volume of the three lagoons is approximately 15.3 million gallons. However, due to the absence of a preliminary treatment facility, benthic solids have accumulated in the lagoons, reducing effective system capacity by approximately 36 percent. Effluent quality is of particular importance in Somerton, where treated effluent is released into the Yuma Main Irrigation Drain, which ultimately conveys water to Mexico where it is used for cropland irrigation.
The City’s Lagoon Replacement Project involved significant environmental permitting and complex regulatory-based public funding structures. The environmental permitting was complicated by proximity to the international border. The funding structure included entities formed under the North American Free Trade Agreement (NAFTA). These apply due to the proximity of the US–Mexico border. The environmental permitting activities involved the US Environmental Protection Agency (US EPA) because of NAFTA and the Arizona Department of Environmental Quality (ADEQ). This paper describes the project and discusses the complexities of negotiating through this multifaceted regulatory framework.