A new 10-year plan for construction and updates that will need to be done at Joplin's two sewer treatment plants is to be prepared this year.

The City Council on Monday night approved a joint contract with the engineering firms of Allgeier Martin and Associates of Joplin and Burns and McDonnell of Kansas City to develop the plan.

The public works director, David Hertzberg, recommended the contract. A staff memo said both firms are familiar with the city's collection and treatment system and its rate structure. Allgeier Martin has planned and overseen construction of part of the system.

Burns and McDonnell currently is working on new five-year rate study that will recommend the rates the city should charge to customers in the next five years to pay for the system's operations and maintenance. The company also created the city's hydraulic study that identifies places where sewage flows are restricted so that equipment can be replaced to reduce blockages.

Engineers will examine four general things to complete the new long-term plan, according to Hertzberg.

One is to create a workable solution for treatment of the lead and cadmium contamination as part of the negotiations with the Missouri Department of Natural Resources for the specifications of the Turkey Creek discharge permit.

The engineers also will estimate future demands on the plant, such as where property development and expansion is expected to occur that will place increased discharges into the system. Hertzberg said that increased need could come from areas including Wildwood Ranch and the Crossroads Center Business and Distribution Park, and that capacity to meet those needs is to be considered in the long-range plan.

A third objective is to reduce the number of pump stations in the system, which can create backup when there is a pump failure. In the hydraulic study, Burns and McDonnell will plan to reduce lift stations with gravity sewer lines "because gravity doesn't fail like a lift station when the pump goes out," Hertzberg said.

In the rate study, the engineers are "analyzing the impact of the improvements on the sewer rates over the next five years," Hertzberg said.

The engineers were asked to provide information the city wants with the rate study by May 31. The long-term plan for the maintenance and construction is to be completed by Dec. 31.

Customers of the sewer system have seen a cumulative 61 percent rate increase over the last five years largely as the result of $35 million worth of construction that had to be done during that time on the two wastewater plants to update treatment methods and replace equipment.

Increases each year raised rates from $27.34 to $29.51 in 2015, to $32.30 in 2016, to $35.41 in 2017, to $39.28 in 2018 and to $43.98 this year. Those rates are based on the usage of 6,000 gallons of water. The increase kicks in each year with January bills.

City bills also include fees for trash and curbside recycling service. The trash rate is currently $11.95, which would bring the overall average residential bill to $55.93, up from $51.23. Those who have curbside recycling pickup also pay another $4.75.

Exact charges per bill vary based on a customer's water usage and size of meter.

Joplin voters in 2009 authorized the city to take out low-interest loans from a state revolving loan fund of up to $35 million for the needed work.

The money was obtained in stages as the work could be done.

The amounts borrowed and balance owed, as of the last statement on Oct. 31, according to city finance department figures provided Tuesday:

• 2010 issue: $5,717,977.20 borrowed; $4,418,300 balance.

• 2011 issue: $25,733,837.78; $22,091,200 balance.

• 2014 issue: $2,795.213.98; $2,401,900 balance.

The loans are to be paid off 20 years from the year of issue, according to the city's finance director, Leslie Haase.

Rate increases

A sewer rate schedule is set every five years using recommended charges by a consultant engineering firm hired by the city based on costs to operate the system. The City Council ultimately examines and approves the rates before they go into effect.