City moves forward with dam improvement projects

Aging dams impounding lakes at the city reservoir and Northwoods Urban Forest Park are set for improvements, with the Hot Springs Board of Directors unanimously approving a contract earlier this week for engineering services.

The contract awarded to Crist Engineers Inc., the city’s water-system consultant, is not to exceed $1,209,350 and will be paid from the $20 million debt issue the board authorized earlier this year. The water-rate increase the board approved last year, raising the 2018 base rate $3 for residential customers, is securing the debt.

The rate schedule will raise the resident base rate, the amount assessed on the first 1,000 gallons of usage, to $13 by 2021 and secure $110 million of debt the city plans on issuing for capital improvements to the regional water system.

Crist’s scope of work includes developing a probable construction cost for the improvements based on its final design and specifications. The city estimates $9,085,000 in construction costs.

The scope of work also includes a geotechnical investigation of Dillon and Sanderson dams, a topographical survey, preparation of bid documents and oversight of construction.

Crist prevailed over O’Brien & Gere and McClelland Engineers in the city’s rating process, averaging 93 out of a possible 100 points on the five ratings sheets submitted by city staff. New York-based O’Brien & Gere was contracted by the city to assess the dams, telling the board in 2016 that none of the three Northwoods dams meet U.S. Army Corps of Engineers stability criteria.

It identified low-interest loans from the Arkansas Natural Resources Commission and federal grants provided by

the Water Resources Development Act as potential funding sources for improvements to the dams.

The company’s report recommended post-tensioning, or threading steel cables through the dam and into the bedrock, to shore up Lake Dillon Dam, which dates back to the 19th century. The report said post-tensioning, at an estimated cost of $3.77 million, would press the dam more firmly against the ground.

A $1.54 million cost was estimated to lower Lake Bethel Dam and restore its lower section, as some of the mortar that holds its masonry together has been displaced by vegetation.

Lake Ricks Dam, which impounds the city reservoir, meets stability criteria, the report said, but had the highest hazard factor of the four dams. A failure of its earthen structure would flood homes on Bull Bayou, the report said.

The city removed the 5-foot spillway wall, which the report recommended to address seepage caused by water lapping against the wall. The removal improved stability but enhanced the risk of the waterline dropping below the intake that feeds the Lakeside Plant.

Fed by runoff, Lake Ricks can’t be tapped during a drought, the city said, making it an inconsistent water source.

The Pine Street pump station’s installation this spring has made Lake Ricks and the Lakeside Plant that supplies treated water to the north side of the city less integral. The pump station, which the city said can deliver 3.2 million gallons a day, proved vital when a lightning strike took the plant offline for a few days recently.

The water it pumped from storage tanks fed by the Ouachita Plant on the west side of the system serviced the north side while the Lakeside plant was down.

“Had that not been online, we would’ve had some serious problems on the north side of town,” Interim City Manager Bill Burrough told the board last month.