The bill for completing extensive structural repairs to Wilde Lake Dam, to meet state safety standards, is going up. But no one's sure how much more than an early $520,000 estimate the project will cost.
"It won't be cheap," said Hal Van Aller, a geo-technical engineer with the state Department of Natural Resources' Dam Safety Division. He said the project would take at least six months.
The concrete dam, built 26 years ago, has deteriorated in recent years to the point where the Columbia Association, the nonprofit organization that operates public facilities in the unincorporated city, has been making "pretty much constant repairs," Mr. Van Aller said.
Laboratory tests indicate that the concrete's ability to withstand pressure is "significantly lower" than the strength assumed in the dam's initial design, Mr. Van Aller wrote to the association after a meeting in June 1992.
The dam is considered a "significant hazard" structure, which means there is the possibility of loss of life and damage to downstream roads if the dam were to fail, Mr. Van Aller wrote in the Aug. 7, 1992, letter.
After the DNR asked to investigate safety aspects of the dam, Columbia Association project engineers found "unanticipated structural deficiencies," according to Fred Pryor, CA's open space management director.
To increase the strength of the dam and keep it from sliding on its foundation, CA plans to replace the entire uppermost tier, or fourth level, which is about five feet high. Originally, plans called for replacing just the "worst section," or approximately one-third, of the uppermost tier, Mr. Pryor wrote last month to the Columbia nTC Council, which oversees the association.
The dam will be anchored to its rock foundation by long steel pinsthat will be inserted in holes drilled through the structure before the top section is replaced in order to re-establish the original 28-foot dam height, Mr. Van Aller.
"Final costs will certainly exceed the original approved budget," Mr. Pryor wrote.
The 10-member Columbia Council allocated $320,000 for dam repairs and $200,000 to dredge Wilde Lake this fiscal year, which ends April 30. The man-made lake, located in the densely populated center of Columbia, has become filled with sediment.
Natural resources officials are reviewing consultants' reports which evaluated the dam's ability to with stand storm water runoff from its 1,200-acre watershed during major storms and floods.
CA ecologist Charles "Chick" Rhodehamel, who is handling the project, said the association and its engineering consultants will develop cost estimates once DNR completes its review and determines the scope of the project.
The association, which collects a 73-cent annual property lien from residents to maintain lakes and other open space areas, will then ask the council for additional funds, Mr. Rhodehamel said.
The dam repair and lake dredging is CA's second most expensive project in its $9.4 million 1994 capital budget, after the million Fairway Hills Golf Course.