County to Dredge Parts of Gunners Lake
By Kevin O’Rourke
Thirty years ago when most of Germantown was still farmland, as townhouses and neighborhood developments were being constructed, lakes and ponds were also being formed to serve as rainwater detention basins for all the impervious surfaces being built. It was at this time when the Gunners Branch stream was dammed up at Wisteria Road to create Gunners Lake.
“Gunners Lake has become a community resource,” said Ravi Parkhie, property manager with North Lake Village Federation. “It is a gem hidden within the community.” The man-made lake created in 1985, has become a sort of destination for Germantown families to hike around and fathers to take their sons fishing.
In February, the Montgomery County Department of Environmental Protection will begin an eight month dredging project which will remove 20,000 cubic-yards of sediment from the northern end of the lake.
According to Amy Stevens, manager of Montgomery County DEP’s Stormwater Facility Maintenance Program, “In November of 2012, we did a study of the sediment deck at Gunners Lake and the study revealed that most of the sediment had accumulated in the north end of the lake where the two streams entering the lake are depositing the sediment.”
Stevens said depositing sediment is the normal course of what streams do in stormwater ponds and lakes. However, over time a significant amount of sediment can affect the stormwater function of the lake. “It decreases the amount of stormwater runoff and storage available in the pond and if it is not removed it reduces the lake’s water-quality treatment capacity which is the ability to allow pollutants to settle out, and they settle into the bottom of the lake. It also reduces the stomwater storage which, over time, can lead to downstream flooding.”
Stevens was quick to point that in the case of Gunners Lake, there isn’t much in danger of downstream flooding other than Wisteria Road and the MARC train tracks.
According to a MCDEP Factsheet about the Gunners Lake project, “In 2011, and then again in 2013, the county tested the sediment in the Lake. The 2011 testing was to determine what contaminants might be present in the Lake. The testing found elevated levels of Polycyclic Aromatic Hydrocarbons and metals in the sediment. In 2013, the County again tested the sediment in the Lake to determine the type and make-up of the sediment in the bottom of the Lake. The results showed that the sediment is mostly silts and clays with some sand and gravel, which suggests the source is eroding stream channels and grit from roadways.”
The cost of the project is $3 million, which is being funded through the county’s Water Quality Protection Charge, which is included on tax bills.
“At the time this lake was being designed in 1984, the county had a program to encourage the development of regional stormwater management pond,” said Stevens. The county agreed to compensate the developer for construction of the lake, and as part of the participation agreement, the pond shall remain the property of the developer and his assigns i.e., North Lake Village Federation. This agreement also made the county responsible for the structural integrity along with the removal of accumulated sediment from the pond which is why the cost falls to the county and not the land owner.
The MCDEP is has announced the name of the contractor for this project. “Solicitations have gone out and bids have come back in, but we have not yet awarded the contract yet,” said Stevens. The MCDEP has combined this project with a similar project at Whetstone Lake in Montgomery Village, which will also cost an estimated $3 million. “We have bundled these two projects into one solicitation, so we are looking for one vendor to complete both projects.”
“The sediment will be removed using a hydraulic dredge method,” said Stevens, “which means that there is going to be a barge in the lake which will remove the sediment, very slowly, and pump it up to the shoreline. Once the sediment gets to the shore, the de-watering equipment will separate the solids from the water. What will ultimately be left is dryer sediment which will be temporality stockpiled to be removed via truck. The water will be cleaned and returned back to the lake.” On average, 30 truckloads of sediment will be hauled off-site daily. The dredging will be limited to a portion of the lake extending from the northern end down to the southern tip of the island.
“This is a normal project,” said Stevens. “We do sediment removal on ponds and lakes all around the county on a regular basis, this just happens to be a very large lake, with a significantly larger amount of sediment than what comes from smaller ponds.”
“The dry sediment will be transported to an approved local facility,” said Stevens. “We have identified three facilities, one is up in Hagerstown, another is in Upper Marlboro in Prince Goerges County, and third is in Southern Maryland in Brandywine”
The project should take approximately eight months of active construction. The county will take every effort to minimize the impact of the construction activities on the residents living around Gunners Lake. In February, the contractor will begin to prepare the staging area, which is the area where the dewatering equipment and the sediment that is removed from the lake will be temporarily stored. The dredging, which is the actual removal of the sediment from the lake will begin in April.