Shawnee, Oklahoma, August 1, 2023 – Routine monitoring and a subsequent investigative study have uncovered structural anomalies along a portion of the dam for Shawnee Twin Lake #1. In concert with the Oklahoma Water Resources Board (OWRB), the City of Shawnee is expanding the scope of the field investigation to aid in the preparation for a potential dam repair and rehabilitation project.

Every year, the dams for the Shawnee Twin Lakes are inspected and evaluated by City staff as well as an independent third party. The resulting inspection reports are then submitted to OWRB. Since 2018, the Lake #1 dam has received gradually worsening ratings of “Fair” to “Poor,” whereas the Lake #2 dam has received a consistent rating of “Fair.”

First, a small longitudinal crack was discovered in the pavement of the roadway on the Lake #1 dam. Since this discovery, a dip in the roadway has surfaced and subsequently grew in size. As this dip has grown, a geo-technical investigation was recommended in the annual inspection report. Initiated based on that report recommendation, the recently completed field investigation focused on the area in which the roadway dip and an associated slippage crack occurred. Based on the investigation’s findings, the entire length of the

2,570-foot dam will now be tested to provide the necessary information for the design of the needed repairs and rehabilitation. Although concerning, there is no indication of an imminent failure.

The dams for the Shawnee Twin Lakes are earthen structures connected through an equalization channel. They also share a concrete spillway and both dam crests serve as roadways. The Lake #1 dam was originally built in 1935 and was revised in conjunction with the subsequent construction of the dam at Lake #2 in 1960. The dams are 55 and 50 feet in height and the normal capacity of the lakes are 22,600 and 11,400 acre-feet, respectively. One acre-foot is equivalent to 325,851.4 gallons.

“The dam at Lake #1 is almost 90 years old and has served our community well,” said Shawnee’s City Manager, Andrea Weckmueller-Behringer. “However, during a recent field study, issues were highlighted that need to be addressed sooner than later. In consultation with our neighboring entities and in collaboration with our State partner, the City of Shawnee is implementing an accelerated schedule for the design and construction of a potential dam rehabilitation project.”

The immediate next steps towards the dam’s rehabilitation will be to evaluate the entire length of the

Lake #1 dam, to investigate for potential presence of water on the downstream slope, and to begin drawing down the water contained in Lake #1. The City will also release a Request for Qualifications aimed at selecting a specialized engineering firm to assist with the design and implementation of the needed dam rehabilitation activities.

For questions or additional information, please contact Andrea Weckmueller-Behringer, City Manager at 405-878-1601 or andrea.weckmueller-behringer@shawneeok.org.