Culver Lake Aeration System Status Assessment

Princeton Hydro conducted a multiple year field study for the Normanoch Association, Inc. (NAI), the owners of Culver Lake. Culver Lake, one the New Jersey’s few glacial kettle hole lakes, encompasses 580 acres and attains a maximum depth of 55 feet. The density and assemblage of the lake’s phytoplankton community and the lake’s propensity for algae blooms was found to be largely driven by the lake’s internal phosphorus load. To control and decrease the lake’s internal phosphorus load, a hypolimnetic aeration system was installed in the mid-1990s. The system quickly lessened internal phosphorus loading. This made the lake less susceptible to algae blooms resulting in significant improvement of the lake’s mid-summer clarity.

However, field data collected by Princeton Hydro from 2005 through 2014 suggested the aeration system was no longer operating effectively. In 2015, Princeton Hydro began a more intensive assessment of the system based on a comprehensive statistical analysis of over 20 years of in-situ and laboratory field data. The analysis demonstrated that at times components of the existing system were actually entraining and upwelling phosphorus rich hypolimnetic water into the metalimnion and at times even the epilimnion. Based on these data, NAI altered the operation of the aeration system, limiting the use of the mid-depth components to spring and early summer, but shutting down those components in later summer. This effectively decreased late-summer, upwelling-related algae blooms.

Understanding the existing system was reaching the end of its service life, NAI also commissioned Princeton Hydro to conduct a dye test. The objective of the dye test was to confirm the operational footprint of the hypolimnetic system and map the amount of hypolimnion actually being reoxygenated by the system. To accomplish this, Princeton Hydro personnel introduced an environmentally inert dye into the lake at the center of the hypo unit. Over the following three days, the migration and concentration of the dye was recorded along the lake’s X, Y and Z coordinates. The resulting data, which were time-date mapped, showed the hypo unit was still able to circulate (and thus reoxygenate) over a mile away from the unit. However, the data also demonstrated deep water circulation of the hypolimnion was increasingly less extensive as distance from the hypo unit increased.

Overall, NAI used the findings of Princeton Hydro’s operational data analysis and the dye study data to confirm the existing aeration system had approached the end of its service life and needed to be upgraded.