The Water Lab

Water testing has always been at the forefront of  TWI’s mission to safeguard our waters. Test results have pointed the way to all of TWI’s projects in wastewater and stormwater management. For over 20 years TWI kept records of water sampling at 8 locations around our three bodies of water to determine the need for the installation of first flush basins and vegetative bioswales to filter stormwater runoff.



Harriet and Melinda at entrance to the lab

To facilitate TWI’s repeated testing of storm water run-off, during the years 2008 through 2011 we partnered with the Tisbury Department of Public Works (DPW) to help them establish a water testing laboratory. With TWI’s input and funding, three bacterial tests that are the most appropriate measures of the health risks due to bacterial contamination of the water were set up: Total Coliform, Escherichia coli, and Enterococcus bacteria. The laboratory was certified by the State to test for bacterial contamination in both fresh and salt water. This certification ensures that the most appropriate testing procedures are used.

To further enhance the role of this laboratory, in 2017 TWI provided funding for the purchase of equipment needed to test influent and effluent samples from enhanced denitrifying septic systems. Effluent must be analyzed for a wide range of parameters, including total nitrogen, total suspended solids, biochemical oxygen demand and pH. This equipment might also be used for testing nitrogen levels in marine samples to evaluate the Town’s progress in reducing nitrogen levels. It is proposed that Tisbury pursue certification of the laboratory for septic sample testing from MassDEP, with the aim of providing at least some of the required testing for Tisbury property owners who install denitrifying septics. Once established for Tisbury residents, the Tisbury laboratory could eventually support the required testing for property owners from other island towns, promoting the installation of denitrifying systems across Martha’s Vineyard.