Lewis Creek Watershed

Running down and through a wide variety of public and private forests and agricultural land in two counties, Lewis Creek is a diminutive but precious resource. Although several sites on the Creek tend to meet VT water standards, during low-flow summer months, E.coli and turbidity levels can run high.

The Addison County River Watch Collaborative has been monitoring water quality in the Lewis Creek since 1992. For the 2012 and 2013 seasons, Lewis Creek was the subject of a more intensive monitoring focus, where rotational as well as sentinel stations were monitored and additional parameters were tested.

Despite its magnificently clear appearance on sunlit spring and summer days, with flashes of movement indicating brook trout in its shallows, Lewis Creek has its acute problems. The creek is listed by the State of Vermont as impaired for contact recreation from about twenty miles from its mouth (in the village of Starksboro near Route 116) down to the Spear Street covered bridge in Charlotte near Mt. Philo, a result of high E. coli counts and agricultural runoff. Pathogen readings have trended highest at the Tyler Bridge sampling station in Starksboro, just before the creek flows into Hinesburg. Not far downstream from that sampling station, Pond Brook runs into Lewis Creek, carrying its own load of pollutants, mostly phosphorus and sediments (see separate article on Pond Brook).

Total phosphorus concentrations increase steadily downstream mirroring turbidity levels, indicating that erosion is the primary source of phosphorus in Lewis Creek. Phosphorus concentrations reach high levels at times, and the jump in the concentrations below Pond Brook reflects a jump in the suspended sediment.

In 2013, E.coli counts in the Lewis Creek at three select sites exceeded the state standard of 77 organisms/100 mL on a majority of the sample dates. E.coli results exceeded the federal health standard of 235 MPN/100 mL at LCR3.7 during the September event, and at LCR14 on three out of the four summer sampling events. Detected E.coli counts at these sites in the 2013 season were largely consistent with historic results.

Turbidity levels in the Lewis Creek at the sampled stations ranged from <0.2 to 10.9 NTUs, with a mean level of 2.6 NTUs for the six sample dates. Turbidity levels exceeded the Vermont state standard of 10 NTUs (for Class B cold-water fisheries) at station LCR3.7 on July 10; flows were moderate due rains on July 3-4. The graph below shows turbidity levels from upstream (right) to downstream (left) for the stations along the main stem of the Lewis Creek. Based on past years’ sampling results, turbidity can increase above the standard at times of increased flow – during a summer thunderstorm, or during spring runoff conditions – especially in the lower reaches of the river. An increasing trend in turbidity with distance downstream is generally observed during all flow conditions.

Phosphorus was detected at low to moderate concentrations during the six spring and summer sampling dates, ranging from 6.8 to 252 ug/L, with an average of 32 ug/L. The mean concentration of Total Phosphorus for the two available low-flow summer sample dates at the Pond Brook site LCT3D.5 exceeded the proposed criteria of 44 ug/L for the warm-water medium gradient (WWMG) wadeable stream ecotype in Class B waters. The graph below shows total phosphorus levels from upstream (right) to downstream (left) for the stations along the main stem of the Lewis Creek. An increasing trend in phosphorus concentration is evident with distance downstream.

Because this subwatershed is dominated by wetlands, LCA had to answer the question whether the phosphorus was coming from Bristol Pond, which is eutrophic (i.e., rich in nutrients), or from other sources. Bristol Pond is a 250-acre shallow, marshy headwater formed by glaciers and also impounded at the outlet by a dam maintained by the Vermont Fish & Wildlife Department.

During 2012-2013, LCA and the Addison County River Watch Collaborative monitored six sample stations on Pond Brook to understand where, when and how much soil and nutrients were entering Pond Brook. After studying storm events and other runoff events, it became apparent that the phosphorus was coming from high flows off particular reaches of the brook. Bristol Pond was not the problem, but rather runoff from various farms and forest areas.

During this detailed study, Lewis Creek Association and local landowners completed an inventory of farms operating in the watershed, reviewed stream studies and existing remote sensing data to pinpoint reaches appearing to have direct stormwater and sediment runoff. Evaluations of the Pond Brook sampling data along with landowner conversations led to identifying specific restoration and conservation projects and practices that could decrease nutrient, sediment and pathogen loading and erosion.

Among the many farms that the Lewis Creek Association found in the Pond Brook watershed – including five small dairy farms and a small beef farm – is Last Resort Farm, which grows organic vegetable, berries and hay. Last Resort Farm, co-owned by Sam Burr, borders Pond Brook near its mouth at Lewis Creek. Burr, a member of the Monkton Planning Commission and Agriculture and Natural Resources Committee, said one area that the Lewis Creek Association examined as a possible source of water quality problems was forestland. Burr explained that he owns hayfields that come to an edge at a series of wooded, steep gullies that lead down to Pond Brook. In the last ten years, storm events have caused trees to uproot and fall. So much erosion has occurred at these locations that the gullies have started eating their way into Burr’s fields.

Some work to stabilize some of the gullies on his occurred in 2014. The Natural Resources Conservation Service provided funds to put down fabric and large stones that will slow stormwater flow and also still let rainwater seep into the ground in a more controlled way.

Lewis Creek Association also worked with a Bristol-based organization promoting sustainable forestry practices, Vermont Family Forests (VFF), to teach landowners some methods to improve water quality through better forest stewardship.