Surface Water Quality and Sediment Evaluation

In response to residents' concerns, the City evaluated environmental conditions at Lake Bradford and Great Neck Lake that can affect water quality.

The main environmental conditions that can affect growth of aquatic weeds, algae, and the health of aquatic life include the depth of the water and specific water quality parameters. The City partnered with Old Dominion University Research Foundation to conduct an evaluation that included:

  • Measuring the depth of the water
  • Measuring the depth of the accumulated lake sediment
  • Analyzing specific constituents in the sediment
  • Analyzing specific water quality parameters

Details

Water Depth

The Virginia Department of Environmental Quality standards for pond depth is a minimum of 4 feet. This depth promotes healthy water quality conditions by moderating temperature fluctuations throughout the day, especially during warmer temperatures. The City requires a minimum depth of 5 feet in ponds and lakes. In addition, the City implements a lake management maintenance dredging program to remove accumulated sediment.

Water depth can impact water quality and aquatic health as it relates to dissolved oxygen. Because of the shallow water, an autonomous surface vessel will be used to measure the water depth using a single beam echosounder to create a map for each lake.

Sediment Measurement

As part of the depth evaluation, the thickness of the accumulated sediment on the bottom of the lakes will be measured to estimate the amount of sediment that can be removed through maintenance dredging. This information may also be used to estimate potential dredging costs.

Ground-penetrating radar will be used to create a map of sediment thickness and a portable coring platform will retrieve sediment cores for subsequent textural analysis and water quality analysis.

Water Quality Measurements

Surface water samples will be collected and analyzed for indicators of aquatic health and potential for algae blooms. Parameters include dissolved oxygen, salinity and temperature. This data will be analyzed to determine if it's within normal ranges.

Schedule & Cost

The total cost of the study was $60,000 and the work started in May 2023. The water depth survey maps were completed in September 2023, and the sediment survey and cores analyses were finalized in January 2024. The original project schedule was delayed because of logistical challenges, including dense lily pads growth, shallow waters and weather conditions that impacted the survey schedule.

  • Lake Bradford plant overgrowth

    Aquatic plant overgrowth at Lake Bradford.
  • Great Neck Lake algae bloom

    Great Neck Lake algae bloom.
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