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Irrigation consultant: New tests, no difference

JULIE LANE PHOTO |  Consultant John Benvegna during a November meeting with the Irrigation Committee. Last week, via telephone, he offered some preliminary findings stemming from January field tests.
Consultant John Benvegna during a November meeting with the Irrigation Committee. Last week, via telephone, he offered some preliminary findings stemming from January field tests.

Water levels on Shelter Island have remained about the same through the years.

This is according to preliminary information from recent field tests conducted by Leggette, Brashears and Graham, Connecticut-based consultants who were hired by the town’s Irrigation Committee. While the report from LB&G’s John Benvegna is still preliminary, he offered some observations at a Thursday, March 6 meeting based on field tests performed January 8 and 9, including an estimate that most years, Shelter Island is using less than 5 percent of the water recharged into the aquifer.

The consultant reiterated his view, stated at a November 2013 meeting with the committee, that irrigation systems aren’t a major contributing factor to either the quantity or quality of water available in the Island’s aquifer. But there’s a need to monitor all water use here, especially during the summer season when water use is highest but aquifer recharge levels are generally lowest, he said.

An over all ban on installing certain automated irrigation systems was due to take effect in September 2013. The ban was enacted in September 2003, with the provision that existing systems could be used, but that use would sunset in 10 years. After a public hearing last August, the Town Board voted for a moratorium on the law until May 2014 for further study. Recently the board set a public hearing for March 28 to discuss extending the moratorium through the rest of the year.

Because of density of development in some areas and the Island’s topography, there’s the potential for salt water intrusion into wells anywhere, Mr. Benvegna said at the March 6 meeting. But it’s most apt to happen in areas such as the Rams, Silver Beach, West Neck and Menantic Creek.

“I don’t see a connection between the irrigation systems and the chloride levels,” Mr. Benvegna said during his more than 90 minute presentation. His remarks were delivered via telephone from his company’s White Plains office. Committee Chairman Thom Milton projected slides from the report on a screen in the Town Hall meeting room.

The consultant reviewed the testing methods used during the January field tests, but committee member John Hallman, who also chairs the town’s Water Advisory Committee, noted that test wells aren’t the same as those used by residents who are pumping regularly, so readings would be somewhat different.

Although the findings from the January field tests were being compared with findings of tests done in the 1970s and 1980s, there were not appreciable differences in chloride levels, Mr. Benvegna said.

There has also been an increase in recharge levels to the aquifer so water levels have generally been increasing, the consultant said. At the same time, he doesn’t consider recent low water level readings “an aberration.” Instead, he said, you have to look at overall records that reveal trends and then judge what’s in the “normal range.”

Little Ram has one of the highest chloride levels recorded on the Island, Mr. Benvegna said. Mr. Hallman pointed out that during the summer months when the population at Camp Quinipet is high, there are incidences of salt water intrusion. That’s in line with Mr. Benvegna’s observation that the areas most vulnerable to salt water intrusion are near the shore.

How valid are the early conclusions from the most recent field tests?

“Nobody likes to hang their hat on one set of data,” Mr. Benvegna said. His company plans a second round of field tests in May.

While the town gets monthly water level reports from the United States Geological Survey, the consultant suggested that chloride levels should be checked annually for a couple of years to get a true baseline and then checked every few years. Alternatively, instead of getting monthly USGS reports, the town might want to switch to quarterly reports that include chloride levels, Mr. Benvegna suggested.

The Irrigation Committee will continue to review the draft report that was distributed to them, but not yet to the public. When it’s finalized, it will be posted on the town’s website, Mr. Milton said.

The committee meets next on Thursday, March 20, at 7 p.m.