Beach Grooming Tactics to Reduce Swimming Bans
Racine, Wisconsin lies on the southwestern shore of Lake Michigan, approximately 80 miles north of Chicago, Illinois and 30 miles south of Milwaukee, Wisconsin. The city has two public bathing beaches stretching over a mile of shoreline that provide an opportunity for the citizens of Racine to enjoy a variety of recreational activities at the lakefront.
As a best management practice, the City of Racine, Wisconsin, altered beach-grooming techniques as a means of reducing diffuse (non-point) pollution to Lake Michigan. A 2-year research initiative demonstrated that past practices acted to increase bacterial indicator density in beach sands. Adjustments to the current equipment employed in beach maintenance provided a no cost means of reducing the frequency of dry weather advisories in this community.
Elevated levels of the current recreational water quality indicator organism (E. coli) in bathing waters at North Beach, a popular recreational site in Racine have been a persistent problem often resulting in advisories or closures. Evidence does not exist for any significant sewage contamination, nor is there a consistent association between high bacterial levels and rainfall. It is believed that increased E. coli counts are likely due to non-point source (diffuse) contamination. High populations of seagulls in nearshore and offshore areas are common and may serve as sources for contamination. Previous research performed in Racine showed a statistical relationship between E. coli densities in bathing waters and wave height. Because of this relationship a plausible transport mechanism was identified, namely, high waves irrespective of rainfall, could serve to transport bacteria from beach sands to surface water.
In Racine, the current beach management practice involves daily grooming of the beach sands for the removal of debris and to create an aesthetically pleasing environment for beach patrons.
Barber™ Surf Rake Mechanical Beach
Groomer towed behind a tractor.
The Wisconsin Department of Natural Resources (WI DNR) funded an initial study in 2001 in order to determine if this practice was responsible for the high density of E. coli recovered from beach sands. Aided by Dr. Richard Whitman (USGS), we examined four treatments, varying the depth and frequency of beach sand grooming (including the current practice).
It was found that deeper grooming without leveling of the beach sand significantly reduced bacterial density. The Root-Pike Watershed Initiative Network (WIN) funded a follow-up study in 2002 in order to determine if this same reduction in bacterial density could be achieved beach-wide through altering the settings on the current mechanical beach grooming equipment (Barber™ Surf Rake Mechanical Beach Groomer, Model 600 HD, Naugatuck, CT).
Past grooming practices leveled and compacted beach sands increasing
Current grooming practices remove debris from beach sands while reducing bacterial density.
The 2002 WIN funded study produced data paralleling the initial study performed in 2001. Namely, deep grooming without leveling served to reduce the density of E. coli recovered from beach sands. In light of this information the City of Racine Parks and Recreation Department began altering their beach grooming practices effective May 2003. This change has resulted in a 30% reduction in the number of dry weather advisories/closures posted this year (25%) as compared with 2002 (55%).
Document prepared October 17, 2003