ST. ALBANS — The Vermont Dept. of Environmental Conservation (DEC) has identified another half-mile stretch of Stevens Brook as being impaired. However, a stream in Fairfield is being removed from the state’s list of impaired waters.

According to DEC, Chester Brook is no longer impaired. For the past four years samples of insects in the stream have shown that the ecosystem is healthy and improving.

A seven-mile stretch of Stevens Brook from the mouth upstream is still considered impaired for agricultural runoff and sediment. A total maximum daily load plan was created for Stevens Brook in 2008, identifying the types of reductions in run off needed to create a healthy stream.

A half-mile stretch downstream from LaSalle Street has been added to the list of impaired waterways. According to DEC, that stretch is impaired by contaminated soils from the St. Albans Gas and Light hazardous site, once a factory location.

One section of Stevens Brook has been removed from the list of impaired waterways. From approximately one mile below the Central Vermont Railway site upstream to the rail yard is no longer considered threatened by contamination from the rail site.

According to the state, the railway has worked with the state to contain pollution and remediate the site, including operating a remediation system for contaminated groundwater for eight years.

The railway also installed a system to remove oil that drips from rail cars onto the tracks, and transported 4.5 tons of contaminated soils and other debris to the Coventry landfill.

Some of the same sections no longer considered endangered by contamination from the Central Vermont Railway site is, however, considered impaired by contamination from the 19th century St. Albans Gas and Light site.

Other waterways around the region remained on the list of impaired waterways submitted by DEC to the Environmental Protection Area yesterday. They include:

• Rock River: algal growth, agricultural runoff, nutrient enrichment.

• Saxe Brook: agricultural runoff.

• Rugg Brook: agricultural runoff.

• Jewett Brook: agricultural runoff.

• Mill River: agricultural runoff, streambank erosion.

• Berry Brook: agricultural runoff, aquatic habitat impacts.

• Samsonville Brook: agricultural runoff, aquatic habitat impacts.

• Godin Brook: agricultural runoff, aquatic habitat impacts.

• Trout River: agricultural runoff.

• Wanzer Brook: agricultural runoff.

• Mud Creek: agricultural runoff, nutrient enrichment.

In addition several sections of Lake Champlain have been identified as impaired by PCBs (polychlorinated biphenyls), a class of chemicals, which can cause cancer, among other health impacts. The safe level of PCBs in drinking water has been set at zero.

PCBs are found in trout caught in the following areas of northern Lake Champlain:

• St. Albans Bay

• Missisquoi Bay

• Shelburne Bay

• Mallets Bay

• Burlington Bay

• Main Lake near South Hero

• Northeast Arm near Swanton

• Isle La Motte

The Clean Water Act requires the state to submit the list of impaired waterways to EPA every two years. In addition to Chester Brook, four other streams or sections of streams were removed from the list of impaired waterways. Several were added.