Contract helps city expand water facilities
Nestled along the Columbia River between Oregon and Washington, the city of The Dalles is home to 11,330 people.
In 1989, the city embarked on a master planning effort designed to expand its water and wastewater utilities to accommodate the increase.
Growth aside, the city was facing commercial enterprise development, including a veteran’s hospital, community college, the Columbia River Gorge Interpretive Center and the Wasco County Museum, all of which made officials certain that the city needed to do something about its wastewater treatment plant, which was limping along and functioning below capacity. Built in the 1930s, The Dalles wastewater treatment plant (WWTP) originally pumped waste directly into the Columbia River. In the ’60s, the plant was converted into a primary classification process, and in the ’70s, it became an activated sludge facility. An antiquated piecemeal facility, it was in considerable disrepair because many replacement parts were no longer available. The typical life expectancy for a WWTP is 20 years, and sections of this plant were more than 50 years old. Furthermore, it had been downgraded from a 4.15-mgd plant to a 3-mgd facility as the result of a local engineering firm’s capacity assessment.
The city realized it did not have the supervisory knowledge and expertise to determine future needs and operate the plant cost-effectively. Consequently, contract operations was selected as the best alternative.
In June 1993, Operations Management International Denver, was given a five-year contract to operate and manage the plant in a public/private partnership with The Dalles. The charter was to provide capital improvement financing for equipment upgrades and modifications designed to maximize plant capacity, reduce energy costs and improve process control.
A diffused aeration system has been replaced with a mechanical aeration system; and variable frequency drives were installed to stabilize flow and avoid surges, increasing maximum flow capacity up to 120 percent in the secondary treatment system.
The aeration system was replaced by company staff in nearby communities for $20,000 in materials, down from a previous quote of $200,000 because the project was so “labor intensive.”
Additionally, overall operations reliability has been increased by half through the installation of a redundancy backup system.
The project team also enhanced the industrial pretreatment and the existing biosolids management programs, and the plant’s biosolids are now applied to agricultural land with the help of a computer program that tracks agronomic loadings for correct application.
Additionally, the city constructed a new second clarifier and provided an engineered stress test evaluation. The modifications have allowed the plant to be certified at its original maximum capacity. And since the inception of the contract, The Dalles has saved nearly $1.5 million based on budget projections proposed by a previous engineering contractor.
Under the contract, city employees became company employees at matched – or exceeded – benefits and salary levels. But the plant is not the company’s only involvement – it has funded installation of two handicapped drinking fountains in local parks, sponsored two softball teams, adopted a two-mile section of local highway for litter pickup, funded training equipment for the city fire department and provided funding and teachers for wastewater treatment courses at the local college.