The City is performing water quality monitoring and analysis at six lakes over a 15-month study period. A summary describing the results, trends, and baseline conditions will be provided following the end of the 15-month study and will be available here. The lakes being monitored include:

• Lake Bradford
• Great Neck Lake
• Lake Conrad 2
• Kemps Lake
• Chatham Hall Lake
• Bayville Lake

The main objective of the monitoring is to establish the dry-weather baseline water quality conditions in these lakes. The City plans to develop a water quality monitoring plan to establish long-term water quality trends. This monitoring will be used to support evaluation of the impacts of upstream Stormwater Management Facilities on the water quality within the lakes and on downstream waterways.

Residents near Lake Bradford, Great Neck Lake, and Lake Conrad 2 have expressed an interest in the water quality within these lakes to support aquatic life. The City is developing methods to evaluate the effectiveness of water quality improvements at Kemps Lake, Chatham Hall Lake, and Bayville Lake within the lakes and downstream waterways.

Study Schedule & Cost

The cost of the study is about $140,000. The monitoring period is from July 2023 through September 2024.

Water Quality Parameters and Sampling Overview

The 15-month monitoring period was selected to capture seasonal variation within the lakes. The lake monitoring and analysis includes:

• Surface in-situ monitoring to measure water depth, water temperature, specific conductivity, pH, turbidity, dissolved oxygen, and dissolved oxygen saturation.
• Samples are collected for lab analysis testing for total suspended solids (TSS), total nitrogen (TN), nitrate + nitrite, ammonia, total phosphorus (TP), and orthophosphate.
• All monitoring events will be performed following a minimum dry-weather period of at least 72 hours, and samples will be collected at least 1-2 ft below the surface.
• The in-situ measurement instruments will be calibrated every month prior to sampling events.

Information on the water quality parameters analyzed, how it’s measured, and what ranges are preferred to support aquatic health are summarized below.

Dissolved Oxygen

Dissolved Oxygen (DO) concentration is the amount of oxygen that is present in water, measured in milligram per liter (mg/L). Dissolved oxygen in waters allows fish and aquatic species to breathe under water. Low DO indicates poor aquatic health.

Acceptable Ranges: DO levels less than 5mg/L are considered stressful for fish and levels less than 3mg/L are too low to support fish. DO levels below 1mg/L are considered hypoxic and usually devoid of life.

Turbidity

Turbidity is the measure of water clarity and describes the amount of light scattered or blocked by particles floating in the water. It is measured in Nephelometric Turbidity Units (NTU).

Acceptable Ranges: Turbidity values less than 10 NTU are considered low and acceptable. Values of 50 NTU would be considered moderately turbid, and values more than 100 NTU would be considered very highly turbid. High turbidity can have negative impacts on fish and other aquatic life. Aquatic plants need light to grow and high turbidity will decrease underwater light availability.

Specific Conductivity

Specific conductivity in lakes is the measure of the ability of water to pass electrical current. Because dissolved salts conduct electrical current, conductivity increase as salinity increases. It is measured in micro siemens per centimeter (µS/cm)

Acceptable Ranges: specific conductivity in lakes generally ranges between 0 to 200 µS/cm. Conductivity is an indirect measure of the saltiness of the water. Fish and other aquatic species that live in freshwater cannot tolerate large increases in saltiness because they are not adapted to saline water.

pH

pH is a measure of how acidic/basic water is. The range is from 0 to 14 with 7 being neutral. pHs less than 7 indicates acidity, whereas pH greater than 7 indicates a base.

Acceptable Ranges: pH in lakes is recommended between 6.5-and 9.0 for the support of aquatic life.

Total Suspended Solids

Total suspended solids (TSS) measure the amount of particulate matter floating in water. In lakes, this can include particles from algae, silt, and clay. TSS levels are often related to the turbidity of water. TSS are measured from a water sample in the lab after filtering the sample and reported as a concentration of milligram per liter (mg/L).

Acceptable Ranges: TSS of 25 mg/L or less is optimal for fish life, while 25-80 mg/L is acceptable, and level of 80-400 mg/l is poor.

Total Nitrogen

Nitrogen is an important nutrient for plan growth and in lakes can be dissolved in water or attached to particles floating in the water. Forms of nitrogen in lakes include inorganic nitrogen (nitrate, nitrite, ammonia, and ammonium) which are the most bioavailable and easily taken up by organisms that live in the water.

Acceptable Ranges: Nitrate concentrations in lakes are typically less than 4 mg/L, and the concentration of nitrite is generally much lower. The concentration of ammonia in lakes waters is generally less than 0.1 mg/L. Nitrogen is measured through sample testing in a lab, and its concentration is reported in milligram per liter (mg/L). Algae and aquatic plants need nitrogen to grow. However, nitrogen levels above acceptable ranges can result in large blooms of algae that reduce the dissolved oxygen levels needed for aquatic life.

Total Phosphorus

Phosphorus is an important nutrient for plant growth and in lakes can be dissolved in water or attached to particles floating in the water. Total phosphorus concentration measures all forms of phosphorus. Orthophosphate (PO4), also called phosphate, measures the soluble reactive phosphorus which is the most bioavailable form of phosphorus, and it is the most easily taken up by organisms that live in the water. Phosphorus is measured through sample testing in a lab, and its concentration is reported in microgram per liter (µg/L).

Acceptable Ranges: Total phosphorus of less than 10 µg/L in lakes is recommended and indicates that the surface waters that are not significantly affected by human activities. Algae and aquatic plants need phosphorus to grow. However, phosphorus levels above acceptable ranges can result in large blooms of algae that reduce the dissolved oxygen levels needed for aquatic life.

Note: Acceptable ranges referenced from DataStream Monitor’s Guide to Water Quality.