The Ct. Department of Energy & Environmental Protection issues an Integrated Water Quality Report to Congress every two years. Water quality definitions and categories are explained in Ct. DEEP's Summary of the Water Quality Standards and Classifications.
The 2014 report has revised assessments for the Willimantic River and many of its tributaries.
The report includes three types of designated uses as being fully supporting, not supporting or unknown (unassessed). The main stem river and tributaries are divided into segments for the report.
Aquatic Life (habitat for fish and other aquatic life and wildlife)
All segments of the river and its tributaries are either fully supported or not assessed, except one section of the river and two tributaries.
Fishing (fish consumption)
All segments are fully supported for fishing. DEEP has issued qualifications for consuming fish from the Willimantic River: for all fish species other than trout, there is an advisory to consume only one meal per month due to mercury contamination from atmospheric deposition (acid rain). In fact, all freshwaters of the State have a fish consumption advisory due to mercury contamination.
The 2014 Report reflects standards required by the U.S. Environmental Protection Agency. Many miles of the Willimantic, Hop, Roaring Brook, and Skungamaug rivers are Fully Supporting for designated recreation uses. Like many other waterbodies in the state, parts of the Willimantic River and its tributaries are listed as "not supporting" for recreation because of excess indicator fecal bacteria in the water. A waterbody must now meet several criteria for designated uses such as swimming and other water-based recreation. These criteria are established in the Connecticut Water Quality Standards, and CT DEEP conducts water monitoring regularly to assess whether those criteria are being met. The definitive sources of the excess bacteria are generally unknown at this time.
Ct. DEEP has sampled rivers across the state to determine the extent of bacterial contamination sources, analyze land cover and uses that may contribute to the contamination, and offer practical remedies for a variety of stakeholders to consider. There is an approved Connecticut Statewide Bacteria TMDL to determine remedies for widespread problems impacting designated uses of Recreation and for Direct Shellfish Consumption (latter in coastal waters). There are report appendices for several Willimantic River watershed streams that provide details on land uses, potential bacteria sources, permitted wastewater discharges, amount of impervious surface areas, condition of streamside vegetatied areas called riparian buffers, current management activities, recommended next steps, and water quality data. This information can assist our watershed stakeholders and project partners to better identify sources and strategies to restore good water quality conditions. Assessed lakes and ponds in the Willimantic River watershed (including Eagleville Lake) are Fully Supporting for recreation, except Crandall Pond in Tolland. A watershed investigation and plan was recently developed for the Crandall Pond area.