Dane County Executive Joe Parisi recently celebrated the grand opening of the improved beach and lake at the Mendota County Park in time for Memorial Day weekend. They highlighted the new pilot “Clean Beach Corridor” which sets up a protected, clean pool of water within a lake. A barrier is established in the lake adjacent to a beach while a treatment system treats and circulates the water within that corridor, reducing the muck and bacteria that results in beach closures when the weather warms in summer. The project cost was $80,000.

The Dane County Land & Water Resources Department has been working on improvements to the beach at Mendota County Park, located on the western shore of Lake Mendota, in the Town of Westport. Part of Dane County Executive Parisi’s 2016 budget, the beach improvements were initiated to improve beach/lake access, minimize the occurrence of beach closures, and provide clean, safe water for beach users.

Prior to improvements, the beach area was elevated approximately 4 feet above the lake, separated by a wall of rock boulders known as riprap. The riprap prevented access from beach users from the sand to lake, limiting recreation activities. The beach improvement project removed the existing rock riprap and created a new gentle sloping beach of sand to the water. The predominant wind conditions at the beach make it susceptible to sand movement by longshore currents; therefore, a floating curtain was installed in the lake to contain beach sand.

The curtain is made of a polyester reinforced PVC with a polyfoam float on the surface, weighted down on the lake bed by a galvanized chain. The curtain, shaped like a horseshoe, is anchored with 2,400 pounds of concrete blocks in the water at four locations and secured on shore. All offshore anchoring points are located with orange marker and hazard buoys for notice to boat and recreational users.

Another benefit of the curtain is that it creates a barrier between the lake and swimming water, protecting from offshore bacteria or algae from coming into contact with swimmers. In addition, any contamination that occurs inside of the swimming water will be cleaned using an on-site treatment system. The system pumps swimming water via two intake pipes and returns clean water back to the swimming area. Treatment of swimming water will use no chemicals; instead clean water is achieved through a system including a strainer, sand filter, and UV disinfection. The treatment system will run 24/7 in order to be proactive from any outbreak of pathogens and toxins. The overall goal of the beach improvements is to increase beach activity while providing safe, clean water. There is only a one day turnover time, if there is contamination today, Mendota Beach swimming area will be clean tomorrow.

The curtain surrounds a swimming area of approximately 100 feet wide by 100 feet offshore.  It is 3 feet deep at end of curtain. The system first removes weeds/debris with a strainer. Next, algae and other suspended particles are removed with a sand filter. Finally bacteria, such as E. Coli, are disinfected with UV treatment. Once the sand filter is dirty, the system is automated to backwash which will send algae to the sanitary sewer removing it from the lake.

This system was created by a partnership with the Town of Westport, UW-Madison engineering, MG&E and Madison Metropolitan Sewage District.