Exclusive: Lake Jackson Dam options include adding new $3.5 million spillway, demolishing the structure

Every day, thousands of cars travel along Route 234 to get from one end of Prince William County to the other. Crossing the Occoquan River near Manassas, one can see the Lake Jackson Dam standing steady as it has for over 90 years.

Residents who live in the single-family homes that make up the Lake Jackson community get to enjoy the lake the dam created for both recreation and aesthetic value. While many people in the area appreciate waterfront living, the rising costs to maintain the dam, the safety risk it poses have county officials concerned.

Constructed in 1928 to generate electricity, Lake Jackson Dam, located about four miles from Downtown Manassas, was built with two turbines that generated power until the late 1950s when it was deemed financially unfeasible. Log cabins were built around the lake during this time as summer homes, which would serve as a precursor to the 35 homes that are now protected by the dam (according to this county presentation), inside the Lake Jackson community.

Prince William County took ownership of the dam in the 1970s. Today, after heavy rains, county staff often drives out to the dam to open the radial gate as the water rises, taking pressure off of the structure. This lets out more water so it can continue its journey down past the Town of Occoquan and into the Potomac River.

The gate, however, is where the problem lies.

Those county government employees work the gate incur great risk having to walk across a concrete catwalk that spans the top of the dam while dealing with the elements, to get to the antiquated gear system that lifts the 25-foot-tall gate.

Before going out on the catwalk, it’s commonplace for workers to don a life jacket and notify fire and rescue crews as a safety precaution, in case they fall into the river.

Waiting for the gate to lift up can take up to 45 minutes as the water rushes below. In order to ensure this occurs when needed, county staff is paid overtime to monitor the dam.

Over the last three and a half years, the county paid $368,441 on gate operation. The dam requires constant maintenance from fixing weather-worn patches of concrete to keeping the gate system working.

In the Fiscal year 2019, the county spent $176,000 alone maintaining the dam with costs projected to continue to increase over the years. All funding for the dam comes from the stormwater management fee paid by county taxpayers.

A study outlines options for the future of the dam

At a town hall meeting held by Coles District Supervisor Yesli Vega on March 12, Prince William County Environmental Services Division Chief Marc Aveni spoke about the possible changes to the Lake Jackson Dam.

After a heavy rain, opening the gate protects the 35 homes from moderate flooding. Due to the high safety risk and reoccurring financial cost, Aveni said, the county had a study conducted by engineering firm Dewberry to come up with some options for the aging structure.

The study produced several options that would change the dam to some degree — options that Aveni said he would recommend to the Prince Willaim Board of County Supervisors.

One option is to install a new gate with a computerized mechanism that would allow it to be operated by remote control. While this option would have the least impact on the community, it would cost a hefty $2.5 million to operate with reoccurring operating costs.

Other options include discontinuing gate operations during storm events, replace the gate with a lower dam or demolish the dam all together to allow the lake to turn back into a river.

All options have varying costs, said Aveni.

The choice that would best prepare the county for the future would have the removal of the gate, catwalk, catwalk piers that support the walkway, and then replace it with a concrete spillway, the study notes.

It would also cost the most upfront with a price tag of $3.5 million but it would lower operating and maintenance costs for the long term considerably. With this option, the county may need to purchase up to six homes with federal funds from FEMA.

Residents have mixed opinions on what should happen with the dam. County employees tell us they’ve had multiple meetings with area residents to make sure their concerns are heard

Some do not want to see any change and have called for a more flexible option.

For now, these are only recommendations as there is no current plan to do anything with the dam, yet.

With the current downturn in the economic climate, says Aveni, this project will not be added to the county’s Capital Improvement Plan any time soon.