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Suffolk County Health Department Releases Environmental Study of Islip’s Grand Canal

Categories: County Executive | Author: probinson | Posted: 8/12/2016 | Views: 5333
Comprehensive Ecological and Public Health Study Highlights Impaired Environmental Quality of the Waterway Due to Pollution from Septics/Cesspools, St


(Suffolk County-August 5, 2016)  The Suffolk County Health Department today released a  comprehensive environmental study of a man-made canal in Oakdale that was created as part of  Idle Hour, the historic William K. Vanderbilt Estate. The Grand Canal Ecological and Public Health Assessment was completed as part of the Health Department’s review of the possible benefits of dredging the canal, and assessed conditions both in the water body and in adjacent  tidal wetland areas. It included the collection  and analysis of water samples, sediment cores, bathymetric data, tidal flow and flushing characterization, plant and wildlife data and wetland characterization. 


“This is the very first time that a comprehensive scientific analysis of conditions in Grand Canal has ever been completed, and the results will ensure that the decisions to be made to address water quality in the Canal are based on valid science,” said James Tomarken, Commissioner of the Department of Health Services. “The Ecological and Public Health Assessment provides clear, science-based recommendations that will allow us to focus with our governmental partners and other stakeholders to clarify next steps to implement specific actions to address environmental concerns in and around Grand Canal.”


Suffolk County Legislator Bill Lindsay, who sponsored the assessment as his first piece of legislation said, "After many years of speculation we finally have independent scientific data that details in great length the conditions, pollution level, and overall well-being of the canal.  This data provides us with concrete recommendations on how we can improve water quality and make the Grand Canal a healthy and vibrant waterway once again.  I am committed to advocate for funding these recommendations at all levels of government to ensure that the Grand Canal is returned to a place where residents can relax, swim, and boat with ease."


Although Suffolk County has set aside funds to undertake a dredging project in the Canal, the report does not recommend dredging of the Canal, which it says would be ineffective until other remedial actions are undertaken.


The study found that environmental stress on the Canal is directly linked to pollution from cesspools and septic systems, stormwater runoff. The wetlands included in the study area were also found to be severely stressed due to an abundance of invasive species and limited tidal flushing. If left unaddressed, the wetlands will continue to degrade therefore diminishing their function to serve as a buffer during coastal storms and long-term sea level rise further exposing residences adjacent to the canal to flooding.


Further, the study indicated that the level of bacterial contamination in the canal would prohibit recreational use by individuals and the fish inhabiting the canal may be also compromised therefore consumption of the fish would not be advised. Importantly, the study states that the level of bacterial contamination is not unique to the Grand Canal,   but that other canals in Suffolk County have experienced similar conditions due to proximity to homes, stormwater runoff and boating activities. 


The  Ecological and Public Health assessment found that dredging the Canal would not improve water quality, but could instead exacerbate existing conditions by creating greater volumes of stagnant water in the waterway.  The recommended actions supported by the report’s science-based  includ several steps prior to dredging:


·         Implementation of an integrated marsh management program -will improve the quality of the wetland, thereby addressing water quality conditions of the canal, decreasing the potential for mosquito larvae production and mosquito control measures, improving coastal resiliency and buffering during coastal storms;

·         Removal of significant portions of the man-made berm presently separating the wetlands from the canal would increase tidal exchange into the wetlands  improving water flow.

·         Upgrading residential on-site septic systems in an effort to decrease the discharge of bacteria and nutrients to improve the long-term water quality of the Canal. 


Once the integrated marsh management plan has been implemented,  the study indicates that selective dredging at the mouths of the northern and southern entrances of the canal could help to improve water circulation thereby improving water quality.  


       “Because decisions about the most effective ways to address environmental degradation of our surface waters and wetlands must be based on valid science, the completion of the Ecological and Public Health Assessment is an historic step forward in the ongoing efforts to improve water quality in Grand Canal, and to restore flow to the adjacent Pickman-Remmer wetlands,” said Commissioner Tomarken. “The County looks forward to working closely with our state and local government partners and the Oakdale community to advance the actions recommended in this study.”


         The Grand Canal Ecological and Public Health Assessment cane be viewed on line at

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