The Oklahoma Water Resources Board recently approved the third renewal of Lawton’s permit to repair the heavily damaged spillway at Lake Ellsworth.
Ellsworth’s concrete spillway was damaged after heavy rains in 2015 forced the city to open the floodgates to release runoff water that otherwise would have topped the dam.
City officials knew from the outset that heavy runoff damaged concrete panels in the spillway. However, further analysis revealed other problems, such as empty spaces beneath the spillway that were identified after geotechnical and engineering analyses. The spillway “floated” during the water releases, Public Utilities Director Rusty Whisenhunt told Southwest Ledger.
The flooding in Lawton last month “didn’t damage” the spillway “any more than it already was,” Whisenhunt told the Ledger last week.
Repairs to the Ellsworth dam will include installing 110 robust rock anchors, placing more drains beneath the apron, sealing numerous cracks, overlaying the 363-foot-long spillway with a 20-inch-thick concrete slab, retrofitting the spillway retaining walls, adding chute blocks on the spillway stilling basin, and adding riprap along the east side of the spillway.
McMillen Inc., an engineering, environmental and construction company, was awarded a $46.4 million contract to repair the spillway of the dam.
McMillen’s bid was one of three submitted for the repair project and was approximately 31% higher than the engineer’s estimate because of the rock anchors and spillway concrete work. “This appears to be acceptable based on the nature and complexity of the work,' consultants from Jacobs Engineering Group told city officials.
Mobilization at the site is expected to occur in early June. “There are a large number of material submittals that will have to be reviewed prior to the start of work,” said Caitlin Gatlin, the city’s communication manager.
The rehab project will take perhaps two and a half years to complete, Whisenhunt said.
The OWRB permit was first approved in February 2021, again in April 2023, and again last week, records show.
According to the Water Board, the Ellsworth dam is a combination earth fill and concrete structure 3,900 feet long, 96 feet high, and 30 feet wide at the top. It has 15 gates, each 10 feet high and 20 feet wide.
The Ellsworth dam is labeled a high-hazard structure because more than 5,200 people downstream would be at risk if the dam failed, the OWRB explained.
OWRB approved a $39 million low-interest loan that the Lawton Water Authority will couple with grants totaling almost $14 million to finance repairs to the dams at Lakes Ellsworth and Lawtonka and to rehabilitate the Gondola Lake Dam.
The bulk of the funds will be spent on the Lake Ellsworth Dam rehabilitation project.
Lake Ellsworth is northeast of Lawton, between Elgin and Apache, and straddles the Comanche/ Caddo county line. It was built by the City of Lawton in the early 1960s as a source of drinking water and for recreation. The reservoir, an impoundment of East Cache Creek, encompasses 5,100 surface acres and has 53.5 miles of shoreline.
Lawtonka, Gondola lake dams also slated for repairs The Lake Lawtonka dam has spalling damage “on the downstream side” and requires some concrete rehabilitation, Whisenhunt said. Spalling refers to deterioration of the concrete surface, characterized by pitting, chipping, flaking or peeling sections, often exposing the reinforcing steel bars beneath.
Jacobs Engineering is preparing a preliminary damage report that will be presented to the OWRB before those repairs can start, Whisenhunt said.
That repair project will cost an estimated $1.2 million, he reported previously.
Lake Lawtonka is situated near Medicine Park and was created in 1905 by impounding Medicine Creek behind a dam 60 feet high and 375 feet long.
City-owned Gondola Dam is downstream of Lake Lawtonka and is used to create a small tilling pool.
The dam is approximately 100 years old and, “There is no as-built information, maintenance records, or previous inspection records” for the barrier, Whisenhunt informed the city council.
A concrete cap will be installed across Gondola Dam, Whisenhunt said. A 2-foot concrete top across the dam has been damaged and will be restored. “We’re also making it wide enough for a sidewalk and handrail for people to walk across,” he said.
The Lawton City Council hired Jacobs Engineering Group in June 2023 to perform preliminary design work on renovation of the century-old dam; that work is nearing completion, Whisenhunt said. “We plan to take it to the City Council at their first meeting in June for approval of the plans and specs, advertise the project in mid-June, and have the bid-opening in mid-July,” he told Southwest Ledger last week.
The Gondola Dam repairs will cost an estimated $3.2 million, he said.
The three dam rehabilitation projects will be financed with proceeds from the $39 million loan from the Clean Water State Revolving Fund (CWSRF), a $925,251 high-hazard dam grant from the Federal Emergency Management Agency, and $13 million in Oklahoma State Designated American Rescue Plan Act grants, city officials reported last month.
The CWSRF loan was authorized March 18 and will be retired over a maximum period of 30 years with city utility revenues, OWRB records reflect. Lori Johnson, chief of the agency’s Financial Assistance Division, calculated that the Authority’s customers will save an estimated $11.1 million in interest charges compared to traditional financing.
In a related matter, the OWRB on May 20 approved the application of Lawton Public Works Director Michael Watrous to be the city’s floodplain administrator.