Dona Bay Watershed Management Plan

Client: Sarasota County

Location: Sarasota, FL

Summary: The Dona Bay Watershed historically encompassed approximately 9,500 acres; however, the current Dona Bay Watershed contains over 47,500 acres. This resulted in the largest adverse impact to Dona Bay ecology due to significant increase in freshwater flows, resulting in substantial impacts to water quality. The influx of freshwater is considered a significant water quality ?pollutant? as it has decreased the salinity of Dona Bay and has altered its ecosystem, particularly the oyster beds, which were studied as an indicator species. The purpose of this project was to investigate the opportunities to divert the flow of excess freshwater currently discharging to Dona Bay using lands owned by Sarasota County in order to restore the historical ecosystem balance.

Cardno ENTRIX investigated four parcels within the Dona Bay Watershed. They included the Albritton Parcel, West Pinelands, the Myakka Connector, and Venice Minerals. The Albritton Parcel is located north of the Sarasota County Laurel Road Landfill and east of the Cow Pen Canal; it was purchased by Sarasota County to provide cover for its landfill. By removing the cover material, this parcel could be used for freshwater storage by diverting a portion of the flow from Cow Pen Canal onto the property. In addition, the Albritton Parcel could be used to store millions of gallons of freshwater that could be treated and utilized as a public drinking supply in the future. Venice Minerals, which is already mostly excavated, was also recommended as a site to store potential public supply drinking water. West Pinelands and the Myakka Connector were recommended as areas of restoration and floodplain storage. West Pinelands is located directly west of Cow Pen Canal and contains the remnants of highly degraded wetlands, which could be rehydrated with the freshwater from the Canal and utilized to store excess freshwater that is currently entering Dona Bay, contributing to water quality degradation. Since the construction of Cow Pen Canal effectively diverted the freshwater flow between the historical Cow Pen Slough and the Myakka River, a portion of the historical flow could be diverted to the Myakka Connector and, ultimately, the Myakka River. The increased flow would rehydrate the wetlands on the site and restore the site to its historical condition.

The proposed wetland restoration could be used as mitigation for future Sarasota County projects, including transportation projects. Implementation of the three recommended phases of the Plan could significantly reduce freshwater inflows, total nitrogen, total phosphorus and total suspended solids from Dona Bay.