ISDS ANALYSIS

In order to address the serious threat of outdated, and currently unregulated Individual Sewage Disposal Systems, we have conducted an analysis of one plat in the southwestern region of Charlestown, south of RT1. What we found: Within the the *** acre area of the plat investigated, there are 168 ISDSs that are currently unregulated. Because theses systems are older, they have a higher probability of being in disrepair and leaking. This leakage is a threat to the community wells nearby and therefore to the drinking water of the residents. These systems also pose a threat to the health of nearby Ninigret Pond. This analysis is only addresses potential for contamination and further investigation would have to be done to ascertain the actual state of these 168 septic systems. Continue to read below for a more detail explanation of this analysis.

Image from http://www.state.nj.us/ dep/dwq/septicmn.htm

Short History:
Almost all of Charlestown's sewage is funneled into Individual Sewage Disposal Systems. Before 1970, RI did not have septic system standards, and therefore, homes built before this date are more likely to have cesspools or other substandard systems. URI estimates that more than 50% of all nitrogen entering the watershed via groundwater recharge is the result of faulty septic systems. In 1993 the state passed a bill to regulate all ISDSs. All new building constructions or renovations that have been done since that time have also had to have their septic systems up to regulation. However, there are many houses that are "grandfathered" because they were built before 1993. These older houses must have some type of septic system, but it is currently unregulated. These older systems are a risk to drinking water quality. Malfunctioning septic systems can leach harmful bacteria and chemicals into soils and ground water. They are also a threat to surface water ecosystems such as the salt ponds of Charlestown. For example, Green Hill Pond is already known to have been contaminated by nearby faulty septic systems.

Methods:
In order to address this serious threat, we have conducted an analysis of one section of primarily residential housing in south western Charlestown.

DATA USED

• Using Plat-Lot data obtained from the tax assessor we identified one plat, number 003, to analyze.
• We then compared the 1999 tax assessor's data which catalogues all buildings by plat-lot-sublot number, address, and year built with ISDS data supplied by Russel Chateauneuf, RIDEM.
• The ISDS data also catalogues buildings built by plat-lot-sublot number, address, type of construction, and date of construction

HOW TO COMPARE THE DATA

After choosing a plat to investigate, open that plat's spreadsheet of ISDS data and that plat's spreadsheet of Tax assessor's data. The plat-lot-sublot number is represented in three separate columns in the ISDS data, but as one composite number in the Tax data. Comparing both of these spread sheets, try to find matches. For example, if the number 003 (aplat column) 001(alot column) 000 (sublot column) is in the ISDS data, look for it in the Tax data as 003-001-000 in the MAPBLOLOT column. If there are discrepancies, the address of this number can also be compared. As a warning, the two data files are not always consistent. There are some entries in the ISDS data that do not match the Tax data. With further investigation, theses could probably be matched, but because of limited time for analysis we simply noted these discrepancies.

Once all matches have been found and noted between the two sets of data, the entries that remain unmatched in the Tax assessor's data are those buildings that potentially have unregulated ISDSs. Using another piece of data from the Tax assessor's database, the dates that these remaining entries were built can be attained using the same matching of plat-lot-sublot number and address method described above.

Results:
IN THE TAX ASSESSOR'S DATA THERE ARE:

• 189 entries
• 21 of which are in the ISDS data with same plat-lot-sublot number and address
• leaving 168 entries not documented in the ISDS data
  
  Of those 168 undocumented:
• 5 were built 1993 or after
• 158 were built before 1993
• 5 had no "year built" data

IN THE ISDS DATA THERE ARE:

• 33 entries
• 8 of which have different addresses or were unmatchable with than tax assessor data
• leaving 25 that match the tax assessor data in plat-lot-sublot and address

Conclusions: The most important information to glean from these numbers is that in the *** acre area of plat 003, there are potentially 168 septic systems which are in disrepair. This fact combined with the plat's proximity to the Community Wells: Shady Harbor Fire District Well #3 & #7 East Beach Landing Condominium Well which are the source of drinking water for the residents of this community, combined with a handful of non-community wells, poses an eminent threat to the quality of that drinking water and the health of its consumers. These systems also pose a threat to the health of nearby Ninigret Pond.

This image from http://www.howstuffworks.com/ sewer1.htm

This analysis is only addresses potential for contamination and further investigation would have to be done to ascertain the actual state of these 168 septic systems.

A broader use of this analysis in Charlestown and in other towns with ISDSs would allow a more holistic understanding of the threats to the towns' irreplaceable water resources.