Mike O'Connell, right, Suffolk County Water Authority's director of production control,...

Mike O'Connell, right, Suffolk County Water Authority's director of production control, on Thursday explains the 1,4-dioxane removal system being planned for the Flower Hill Road pumping station in Halesite.

The Suffolk County Water Authority will install its third treatment system to remove the chemical 1,4-dioxane at a site in Huntington where drinking water has tested at more than three times the proposed state limit for the likely carcinogen, officials said Thursday.

It will take about two years to design and build the system, known as an advanced oxidation process (AOP), at the Flower Hill Road pumping station in Halesite, which provides water to about 30,000 people in the area, officials said.

The Suffolk County Water Authority has one 1,4-dioxane removal system running in Central Islip and another one being designed in East Farmingdale. 

While the state has yet to set an enforceable drinking water standard, "We're proactively installing AOP treatment at priority locations," Suffolk County Water Authority Chairman Patrick Halpin said at the site Thursday.

Suffolk County Water Authority officials budgeted about $1.25 million for the system, though they warned costs could escalate based on bids and design requirements.

Mike O'Connell, the director of production control, said 34 or 35 of the water authority's 600 wells have 1,4-dioxane contamination above the maximum contaminant level of 1 part per billion recommended by a state panel of health experts, water providers and academics. The state Department of Health has said it plans to set a maximum contaminant level this year for the contaminant, which the U.S. Environmental Protection Agency has labeled a likely carcinogen. 

Lifelong exposure to 0.35 parts per billion of 1,4-dioxane represents a one-in-a-million cancer risk, according to the EPA. In December, the panel of state health and environmental officials, water providers and academics recommended a drinking water standard of nearly three times that — 1 part per billion for 1,4 dioxane. The man-made chemical is found in industrial solvents and in trace amounts in cosmetics, detergents, shampoos and other home care products.

Water at the site has tested at 3.84 parts per billion of 1,4-dioxane at the highest, and most recently tested at 2.02 parts per billion, according to Kevin Durk, director of water quality and laboratory services for the Suffolk County Water Authority, which provides water to about 1.2 million residents.

William Spencer (D-Centerport), who is a Suffolk legislator and a medical doctor, sought to reassure residents about drinking tap water.

"I treat babies, I have family here — I feel comfortable drinking the water here," Spencer said.

1,4-dioxane had been identified at 82 drinking water wells on Long Island at concentrations higher than 1 part per billion, according to a federally required survey of large water providers.

Water providers have estimated it will cost $840 million to install treatment on systems and said it would take years to meet the standard. Environmental advocates have called for the state to force compliance with a standard as soon as possible.

Bethpage Water District has constructed one AOP system, but is still waiting on state approval, according to Dennis Kelleher, a spokesman for the Long Island Water Conference, a coalition of more than 50 water suppliers and industry representatives. Other water providers, including Garden City Park and the Water Authority of Western Nassau, Hicksville Water District, and Plainview Water District are in various stages of pilot testing and installing the systems.