Peachtree City Council is making plans to potentially do additional dredging of Lake Peachtree outside the scope of what the county is already planning to do. In the meantime, the city awaits news from the state on whether the lake’s dam deserves a Category 1 or Category 2 classification.
The outcome of that decision will have a substantial impact on the cost and time it will take to return the lake to full function.
At Thursday night’s city council meeting, attorney Andy Welch and Engineer Dan Davis of Integrated Science and Engineering updated council on the current status of the lake and offered some recommendations going forward.
The city is currently appealing the state’s Category 1 designation, hoping to get the dam re-designated to Category 2, which requires less extensive repairs to the existing spillway.
Meanwhile, the county is gearing up to begin a dry-dredging of the lake, something it is contractually obligated to do every 10 years per an agreement between the city and county.
City Manager Jim Pennington had ISE perform an analysis of the lake to determine if there could be a benefit to the city conducting additional dredging of its own. He said increased dredging had been brought up for years, but never seriously examined, and so he wanted ISE to come up with options and cost estimates to at least “get the conversation started.”
Davis offered those estimates at Thursday night’s meeting. He noted that the primary benefit of doing extra dredging around the edges of the lake would be to limit “weedy” growth in the shallower areas. He said the growth is primarily a nuisance for swimmers, for example, but also had some ecological effects on the lake.
“There’s nothing wrong with the growth, it’s just that it’s unsightly and somewhat spoils the light recreational elements of the lake,” Davis said.
To prevent that growth, Davis said it is necessary to increase the depth of the water enough that the sun cannot penetrate all the way to the lake floor and help propagate the weeds. He noted that this requires a minimum depth of three feet, but recommended the council dredge to a depth of at least 3.5 feet to leave some room for added silt build up over time.
For the 3.5-minimum depth option, Davis indicated a possible cost in the $603,000 to $1,000,000 range.
Part of the timing of this issue, however, is that the city has an opportunity to tack on to the county’s upcoming RFP (Request for Proposal) and thereby get some savings by adding on to what is already a large project.
County Water System Director Lee Pope said that if the city joins the county’s bid they will likely pay less than the estimates given by ISE.
“I think you’re going to be surprised. I think these numbers are going to be higher than you’ll see if you piggyback on us,” Pope said.
Davis agreed that if the city were to wait and do the dredging as a separate project, they could expect “significantly” higher costs.
The whole circumstance involves a lot of moving parts as the county and city work in tandem and await the decision from the state. Davis said, however, that he felt if the city successfully appeals for a Category 2 then the various elements could align nicely, timing-wise.
Davis also emphasized the spillway is 50 years old and “has served its useful life.” He said the city should plan to replace it regardless, but, in the meantime, could return the lake to normal water levels while making plans to do so.
“In my opinion, if we get a Category 2, we could do a temporary repair to the existing spillway while we design a new spillway.”
The crucial distinction between Category 1 and Category 2 is whether a breach in the dam would pose a threat to life downstream. Welch indicated the state determined there was a threat based on two properties “below the dam.” He said that determination was based on a 2008 flood plain map and not “actual engineering and modeling for what would happen in an actual breach.”
Neither Davis nor Welch could say whether they expected the city to be successful in its appeal. They seemed optimistic and Davis noted it is possible an answer could come back from the state by Christmas.
As Welch noted, the cost differences are substantial. Establishing a Category 1 dam could cost $5 to $7 million, whereas a Category 2 might cost between $1.5 and $2.5 million.
Added to the menu of possibilities, Davis provided cost estimates for removing the lake’s island, often referred to as “goose island” or “snake island.” He said it was formed from materials from a previous dredging and, according to another citizen, left there as a cost saving measure in lieu of removing the material.
Davis indicated that removing the island entirely could cost anywhere from $3 million to $5 million.
One resident that lives behind the island said she felt citizens were willing to make the investment in the lake.
“I understand it is not budgeted, but, to your point, we have an aging lake that is still worth the investment for years to come. I understand it’s a huge investment, but what’s it cost us to not make that investment?” she asked.
As she noted, none of the potential expenses are currently budgeted.
The cost scenarios are vastly different depending on the state’s decision on the dam’s classification.
Based on the numbers presented, if the city got its Category 2 classification and hit the low end of cost estimates, it could do the minimal dredging plan and repair the spillway for around $2 million. That appears to be a best-case cost scenario at the moment, with many variables still in play.
Time is of the essence, however, and council will likely need to decide at its November 20 meeting whether to “append to,” or piggyback on, the county’s dredging RFP.
Pope noted the city can choose to do so in order to obtain cost estimates, but could decide whether or not to participate after those estimates come back. He said if he were a Peachtree City resident, he would recommend the city to take that route and not forgo the chance to get substantial “bang for the buck” by joining the county’s dredging project.