City considering sewer river crossing

City Commissioners will consider a $187,868 contract during their Aug. 18 meeting for a sewage lift station river crossing feasibility study.

City staff is recommending approval of a professional services agreement with TD&H to conduct a condition assessment of the existing force main at the 6th Street Pump Station, as well as an evaluation of the available options to create redundancy and/or replace the aged wastewater conveyance infrastructure.

Sewer Treatment Funds have been programmed and budgeted for this project.

The city operates and maintains a wastewater collection and treatment system that provides service to a roughly 17-square mile area. The 6th Street Pump Station, or Lift Station No. 1, and its force main serve an area of about 6.8 square miles and delivers approximately one third, or about 3.5 million gallons per day, of the city’s flow across the river to the waste water treatment plant.

The existing Lift Station No. 1 force main was constructed in 1979 and is the only river crossing for this section of the city’s sewer collection system.

“It was constructed under emergent conditions in response to a failure of the 1959-installed crossing. The failure of the 1959 crossing resulted in a protracted, direct,
and uncontrolled discharge of untreated sewage to the Missouri River. If this type of event occurred today, it is expected the enforcement response from oversight agencies would be swift and stern. The existing force main is intact, but has reached or exceeded its expected service life. Therefore, a new river crossing is necessary to maintain the integrity and function of the wastewater collection system,” according to the city staff report.

The feasibility study will include an evaluation of the existing lift station and force main and the feasibility and costs relating to constructing a new sanitary sewer river crossing from the Lift Station No. 1 across the Missouri River to the City’s wastewater treatment plant; options for routing the proposed pipeline under the Missouri River as well as evaluating the feasibility of running a new sanitary sewer line utilizing existing road, bridge, and trail rights-of-way; connection options and details at the pumping station and the head works at the wastewater treatment plant, according to the staff report.

The agreement services include evaluating construction options, conducting geo-technical evaluations, checking utility conflicts, investigating and assessing alignment options, and preparing construction cost estimates, according to the staff report.

The city received six proposals for the project. Those proposals were reviewed, assessed and scored. Four firms were shortlisted for interviews and those interviews were held, evaluated and scored in June.

The city then made reference checks and TD&H received the highest score from the city’s selection committee.