In 1972, the Clean Water Act was passed by Congress. The Act required all waters of the United States to be fishable and swimmable. Improving the treatment of sewage was identified as a primary mechanism to achieve these goals. The Act required a minimum treatment efficiency of 85% removal. Neither the Englewood nor the Littleton treatment plants could achieve this level of treatment.
Both plants needed upgrades to meet the new regulations; however, the newly formed Environmental Protection Agency (EPA) preferred to combine treatment needs at one larger facility rather than spend the money to improve two old, smaller facilities. Negotiations and planning for a new regional facility began in 1973. The end result of this work was the Littleton and Englewood Regional Joint Use Wastewater Treatment Facility. The Englewood WWTP and the Joint Use Plant were known as the Bi-City Plant.
Since both service areas flowed by gravity to the Englewood WWTP site, the plant was situated at this site. The Joint Use Plant was rated for 20 mgd using a pure oxygen system to support the biological treatment process. The plant was conceived as a modern, computer controlled facility capable of meeting advanced treatment requirements. The site and physical layout of the plant was to accommodate an ultimate capacity of 60 mgd. Funding for the new plant was primarily from an EPA grant along with a state grant and local funds. A portion of the funding was for innovative technology. Total cost of the new facility was $22,556,000 including the EPA grant of $13,000,000.
The plant was constructed in the mid 70’s, removing the two older treatment plants from service. Operation of the plant began in April 1977. From the beginning the plant was plagued with operational and maintenance problems. The main problems encountered were startup problems, failure of the computer control system, bottlenecks in the sludge handling processes, difficulties in operating the cryogenic (oxygen) plant and unreliable digester mixing. Staffing problems at the time added to the situation.
These operating problems resulted in the Miscellaneous Improvements Project. This project was to correct the immediate problems with plant operation. The cost was $700,000 and took over a year to complete. The work attempted to correct the worst of the problems and was marginally successful. Many of the operational short-comings at the plant remained.
In 1978 the EPA levied a fine against the cities for the operation of the plant. Effluent quality did not comply with discharge permit limitations, particularly suspended solids. Severe odors were generated at the plant and odor complaints to the agencies were common. The fine was $30,000 and was shared by each city and the engineering design firm.
The period from 1977 to 1982 was when treated sludge (now called biosolids) from the plant was hauled to the Lowry Landfill. The sludge disposed at Lowry ranged from dewatered sludge (18% solids) to liquid sludge (3% solids). All landfill regulations were followed at the time, but the cities were named as Potentially Responsible Parties (PRP’s) in the Lowry Landfill Superfund cleanup work. The cities direct involvement with the cleanup work ended in 1993 in a settlement with Denver and Waste Management. The cost of the settlement was $1,700,000.
In 1982, the cities ceased the sludge disposal program at the Lowry Landfill site and initiated an agricultural "Beneficial Use" program utilizing sludge (biosolids) as a soil amendment in which to grow dryland wheat and other crops. That same year, a research component was added to the program for the purpose of studying the impacts, both short-term and long-term, of biosolids on soil, crops and groundwater. The L/E WWTP has an intergovernmental agreement with Colorado State University that provides funding for a Doctoral Research Assistant in the Department of Agronomy who studies all aspects of biosolids application and dryland wheat growth. This research has provided over twenty years worth of valuable data that has been used as testimony in public hearings on the EPA’s 503 regulations, as well as for program development. In 1989 the Beneficial Use Program was awarded the EPA Region VIII Excellence Award.