New canal study underway: Water quality is goalBy Steve Estes
Monroe County’s long road to improving water flow in residential canals may be taking another small step forward in the near future.
Many of the residential canals in the Florida Keys were developed by excavating fill material for land-based developments more than 40 years ago.
According to a recent engineering report, the excavation was done with little regard for currently accepted canal design standards and little concern for water quality within the canals.
In many areas, canals were dredged deeper than 10 feet when the receiver waters were only three or feet in depth creating poor tidal flushing that has over the years affected water quality in the canals.
Once the filled lands were increasingly developed, water quality began to deteriorate as well with the advent of cesspits and septic tanks to service residential homes, increasing run off of human and pet waste into the waters.
Due to the lack of water quality engineering, the dredging of residential canals was halted by the federal government and those that weren’t yet opened to the receiver waters have been plugged permanently.
As pollutants became more prevalent and silt was added to the bottoms by poor tidal flushing, oxygen levels began to decrease, increasing the growth of algae and other marine forms that again deteriorated the water quality.
In the 2004 and 2005 storm season, eight windstorms added another element to the pollutant base of canals as construction materials, furniture and even vehicles were blown into the canals by the winds, or carried in by the rising waters, particularly during Hurricane Wilma in 2005.
The report says that some water quality gains have been made in recent years as central wastewater systems began replacing individual septic systems and cesspits were eradicated.
Should the county accept the new contract, it will receive an updated inventory of all the residential canals in the island chain.
The existing inventory was done in 2001 as then county officials began to consider ways to improve near-shore water quality.
The second phase of the proposed project will be to establish a cost estimate for various treatment methods in residential canals to enhance water quality.
Some of the methods being discussed include the installation of weed gates at the canal entrances to keep floating sea grass out of the deeper canal waters. Canals with weed gates installed are generally thought to have higher water quality than those without.
Another treatment method being considered is the back-filling of canals where the current depth doesn’t allow for adequate tidal flushing, bringing in cleaner water from the receiver waters and pulling the pollutants into the basins to be dispersed.
Still another treatment method on the table is the installation of flow improvement culverts, particularly in residential areas where multiple dead-end canals branch off a single open-water canal, or in areas where a canal is plugged to the open water to allow for more tidal flushing. The culverts will not open the plugged canals to open-water access.
One of the methods currently used by some homeowners is the installation of aerators below the surface of the canal water to artificially add oxygen to the polluted canals.
Updating the reports and creating new estimates for fixes to canal water quality issues is estimated to cost the county about $10,000.
Implementing the treatment methods, however, was estimated to run into the tens of millions a decade ago.
The installation of a single flow improvement canal in Breezeswept Beach Estates on Ramrod Key more than seven years ago cost taxpayers in that area more than $300,000. The cost was handled by a special assessment voted in by the homeowners.
Canal water quality has long been an issue of importance for long-time County Commissioner George Neugent, but he admitted a few years ago that the county coffers couldn’t absorb the cost associated with treating every canal in the county with poor water quality.