Click below to check for erosion sites from the Thompson Lake Watershed Survey Report

2023 Watershed Survey Report

2023a Watershed Survey Report Cover

Watershed Protection Plan: TLEA’s Plan for Non-Point Source Pollution

Non-point source pollution (NPS) is recognized as the primary threat to the water quality of many Maine lakes. In 2013 the Maine Department of Environmental Protection listed Thompson Lake as a Nonpoint Source Priority Watershed, acknowledging the effects of shoreline development and a slow flushing rate. TLEA is planning a watershed survey of the entire lake in 2023, which we guide us in developing a watershed protection plan that, in turn, will allow us to apply for federal 319 Grants for erosion control measures.

What is a Watershed?

Non-point source pollution that occurs within a watershed will eventually make its way to the lake. Traditionally, we have thought of pollution as something that occurs from a major point of entry, such as a factory or mill depositing their byproducts into a water way. Since the Clean Air Act of 1972 and increased awareness, much of this pollution has been reduced. Now the largest threat to lakes in Maine is from the combination of small sources of pollution throughout a watershed, which combine to adversely affect the water quality. These myriad sources are referred to as “non-point” and include soil erosion, yard waste, fertilizers, manure from farms, inadequate septic systems, winter road sanding and storm drain outlets. Presently, the most significant pollutant in the runoff from a watershed is the element phosphorous, which is concentrated in soil, human and animal waste, as well as fertilizers. Phosphorous is a major nutrient for algae, so as it accumulates in a body of water there will be an increase in algae growth, which can lead to less clear water, oxygen depletion and algal blooms. Even worse, with increasing accumulation, decomposing algae at the bottom of a lake can become a source of phosphorous production, which makes elimination of the algae almost impossible.

How Does Development in the Watershed Affect NPS?

Development of a watershed area results in smoothing of the land, creation of impervious surfaces such as driveways or lawns, and removal of vegetation which leads to larger and more rapid drainage. Studies have shown that a developed watershed will result in 5- 10 times the amount of phosphorous in runoff compared to forested watershed. As an example, if a lakeside property has only a grass lawn as a buffer, 82% of stormwater will run directly into the lake. If a similar property has 100 feet of vegetated buffer at the shoreline, the runoff is reduced to 27%. Increased runoff from developed areas can also lead to erosion of the shoreline, habitat damage, increase in invasive plants and ultimately, a decrease in the aesthetic value of the lake, and property damage.

When we look for ways to reduce polluted storm runoff of developed areas, it is helpful to consider the 3 ‘S’s” of erosion control: Soak, Steady and Send. Primarily, the goal is to create or maintain vegetated areas that will soak in runoff. Secondarily it is crucial to steady the shoreline land, with measures such as planting or mulching bare areas and placing crushed stone or mulch on paths. Additionally, we should send or divert areas of concentrated runoff to adjacent vegetated buffers or armored basins as much as possible.

Previous Watershed Surveys and Protection Plans

Previous watershed surveys of Thompson were performed in 1994, 1999 and between 2008- 2010. The last survey of 2008-10 was performed in segments: the western section (south Otisfield) in 2008, the southern section (Casco and Poland) in 2009, and the northern section in 2010 (north Otisfield, Oxford and Norway). Overall, 345 NPS sites were documented over 11 different land use types. The surveys were used to compile a NPS Site Tracker for the entire watershed. A watershed protection plan was then developed in four phases, the last of which took place in 2014-16.

Phase IV of the plan addressed erosion sites in Poland and Casco, in which 12 major sites of non-point source pollution (NPS) in the watershed were mediated resulting in an estimated reduction of 27 tons of sediment dumping into the lake per year! Our Youth Conservation Corp constructed erosion control measures at 45 NPS sites around the lake. We also provided technical assistance recommendations for landowners of 30 water quality impact sites. Overall, $152,000 was raised for these Phase IV projects; $88,000 of which were from 319 Grants, which were established by the Clean Water Act of 1972. The remainder came from matching local funds, including in-kind services.

In recognition of our efforts, in 2015 TLEA was awarded the Stewardship Group Award from the Cumberland County Soil and Water Conservation District for its success in obtaining 319 grants and implementing erosion control projects.  This project was spearheaded by our outgoing president Marcia Matuska. Other members of the 319 Committee were Pete Laverdiere, Ron Armontrout, K C Putnam, and Kathy Cain. Many thanks to these volunteers.

Watershed Survey 2023

The 2023 TLEA Watershed Survey Report is now available. Click on the link 2023 Watershed Report  to see a full description of the purpose and details of the survey, maps of the watershed showing erosion sites detected by the surveyors. Appendix D of the Report shows the location of the erosion sites, the remediation measures that were recommended, as well as their estimated cost and whether further technical assistance is needed. Names of property owners have been removed to ensure confidentiality. Letters to property owners of the medium and high impact sites will be sent to explain what they can do to reduce erosion at their site.

This Report will be used to develop a Watershed Protection Plan that will allow us to assist landowners, towns, road associations and the Maine DEP apply for federal 319 Grants that can help fund selected remediation projects. This Plan will be posted on the website in early 2024. Applications for the first round of grants will be submitted by May 17, 2024. We plan on 5 rounds of applications over the next 10 years.

TLEA has created a 319 Grant Steering Committee to oversee this project. The committee includes representatives from the Maine DEP, the local Soil and Water Conservation District Managers and other town representatives. We hope to work with local landowners and town managers to develop and fund erosion control projects. We will also communicate with the membership and landowners regarding our plans and how they can benefit the lake. More information on this exciting program will be in the 2024 spring Observer. Anyone interested in applying for 319 Grants or have questions regarding this project can contact us at: Let’s all work together to reduce erosion and protect the natural resource of Thompson lake.