Varela and Associates to complete survey work for City of Ritzville’s lagoon cell

The City of Ritzville took the first step in addressing a deficiency issue with one of its lagoon cells.

In March, the Washington State Department of Ecology Dam Safety Office (DSO) sent an inspection report to the city indicating the drainage channel along the northwest side of the lagoon cells has insufficient hydraulic capacity to pass the 500-year storm event.

The DSO analysis team developed storm calculations for the 500-year event with the required design flow of 181 cubic feet per second (cfs), which the city must modify the lagoon to meet.

The DSO is requiring the City to address the deficiency in a design report outlining the solution and channel configuration, as well as arrangements for implementing the channel modifications.

The City contracted with Varela and Associates to complete a scope of work for the engineering report.

Principal Engineer Dana Cowger said the firm used the calculations and design flows developed by the DSO and background information from the organization’s inspection in their report. Cowger explained Varela’s engineering report will consist of a field survey and base map of the existing channel.

Varela’s report will also detail the specific work the city needs to compete in order to be compliant.

During the Feb. 6 meeting, the Ritzville City Council voted 6-1 to approve Varela’s proposal at a cost of $16,820.

He also noted Varela will not perform a soils testing of the channel as part of their report.

Cowger explained Public Works Director Larry Swift anticipates being able to achieve the one inch deepening and channel modifications without a soils test. Varela will also determine if any additional investigation and is necessary depending on the actual field soil and rock conditions.

Varela will also conduct a hydraulic analysis of drainage channel and prepare drawings.

Cowger anticipates the survey work will take up to 140 hours to complete.

The company will prepare the engineering design report and submit it to the City. After the City reviews the report, Varela will forward it to the DSO.

The firm will address any comments from DSO, then finalize the report.

While Varela is competing the investigative work for the project, the City’s Public Works Department will carry out physical deepening of the channel and modification work.