According to the bypass elimination plan completed by Olsson Associates, of Springfield, the City of Cassville will need to come up with over $2.5 million to update the city sewer system in order to meet Missouri Department of Natural Resources (DNR) requirements.
In the past, during major wet weather events, the city's lagoon was filled to capacity and plant operators were forced to open an outlet valve to discharge water to the environment. The city was allowed to discharge as long as effluent quality met the discharge limits.
On June 30, 2010, a revision to DNR effluent regulations became effective prohibiting wastewater discharges that bypass the biological treatment portion of a city's wastewater plant. In response, Cassville signed a voluntary compliance agreement with DNR and agreed to complete a bypass elimination plan to reduce wet weather flows and eliminate bypasses from the lagoon.
The Cassville City Council received the bypass elimination plan on June 9. In the plan, Olsson Associates recommended a combination of replacement and rehabilitation of the city's sewer system.
The plan states that if infiltration can be reduced to normal levels, the city's 1.13 million gallon per day wastewater treatment plant and 18-acre lagoon will have the capacity to handle the short inflow spikes from most rain events.
In order to improve the collection system capacity, Olsson Associates recommended the following: replace the trunk sewer line to the plant with a line that is 24 inches in diameter; install an 18-inch line parallel to the 15-inch steel creek crossing from the plant entrance to the first Flat Creek crossing; replace the 15-inch line from Flat Creek crossing to the intersection of 14th Street and Park Avenue with a 24-inch line ; and replace the 12-inch line to the intersection of 10th Street and Fair Avenue with an 18-inch line.
The plan also calls for the replacement of the sewer line on 11th Street, which parallels a drainage ditch and Town Branch Creek. In order to make the line less susceptible to infiltration, it should be replaced with a 12-inch PVC pipe.
Olsson Associates indicated that the old sewer lines are in good general condition and can be relined or repaired. Spot repairs can be completed by the city's public works department.
A major rehabilitation project was recommended when funding becomes available. At a minimum, Olsson Associates recommended line rehabilitation for 30,000 lineal feet of the system. This would include 15,000 feet of full relining and 15,000 feet of joint grouting. The plan also suggests relining 200 manholes.
The bypass elimination plan offered the following cost estimates: 4,500 feet of 12-inch pipe, $180,000; 500 feet of 18-inch pipe, $30,000; 7,000 feet of 24-inch pipe, $490,000; 16 48-inch manholes, $48,000; 19 60-inch manholes, $95,000; 40 service connections, $8,000; 4,000 feet of pavement repair, $80,000; relining 15,000 feet of eight-inch sewer line, $360,000; joint grouting of 15,000 feet of eight-inch sewer line, $180,000; service line grouting, $180,000; and relining 200 manholes, $200,000.
Olsson Associates recommended a 15 percent contingency, which would be around $280,000, and estimated engineering and administration costs at 20 percent or $374,200. An additional $20,000 was included for mobilization and bonding.
The total improvement project, using 2012 cost estimates, is $2,525,850.
The Cassville City Council has taken no action regarding the bypass elimination plan at this time.