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TLEA examined the issue of target water levels for the lake for both summer and winter. It also considered when the winter drawdown should start and when it should be completed.
Soil erosion, which dumps phosphates into the lake, is a major threat to lake water quality. Therefore dam control is a way to significantly reduce lake pollution. Maintaining shoreline integrity also helps prevent the undermining of large trees, causing them to fall into the lake. According to biologists, the greatest amount of soil erosion results from erratic water levels, especially those above or below what is called the "cobble zone," the area with the highest concentration of rocks and pebbles.
In developing its recommendations for the fall drawdown, TLEA also considered the following factors: the need to preserve boat navigation in shallow areas until after Columbus Day weekend; and the need to protect the lake trout fish spawn between mid-October and early November. From 1918 to 1986, officials at the Robinson Mill recorded the lake level in a log book on a weekly basis. TLEA examined 20 years of recorded water levels from 1966 to 1986 and found the average winter water level to be 37 inches below the top of the dam. In more recent years, winter water levels have been left significantly higher, resulting in spring flooding (above the cobble zone) and erosion.
Given all of the above considerations, TLEA recommended the following:
1. a target winter water level of 32 inches below the top of the dam, with the winter drawdown starting around October 1 and finishing by October 20 .
2. a target summer water level of 16 inches below the top of the dam, 2 inches lower than the current target, so the lake can absorb sudden increases from small rainstorms and thus help to reduce soil erosion considerably.
These recommendations were presented to the Town of Oxford Thompson Lake Dam Committee In July of 2012. The committee adopted the recommendations, and a public hearing was held on August 30, 2012, in the Oxford Town Office. Scott Bernardy of TLEA presented the same recommendations to approximately 175 people attending from Casco, Otisfield, Oxford, and Poland. Because of the high level of support shown at the public hearing, the Oxford Selectmen agreed to adopt TLEA’s recommendations.
The charts on the right side of this page show the following for each month of the year: the highest and lowest number of inches the water level is below the top of the dam. For example, in May 2011 the water was between xx and xx inches below the top of the dam. The summer target level of 16 " below the top of the dam and the winter level of 32" below the top of the dam are also shown on these charts.
HISTORY OF THE DAM
Andrew Craigie was the first to see the potential for damming the outlet to Thompson Lake.1 In 1797 he purchased four lots of land of 100 acres each and, with the intent of establishing a mill, built a dam. This dam controlled the major outlet stream from the lake into the Little Androscoggin River. Craigie’s initiative began the industrial development of the town of Oxford.(1)
In 1825 a building known as "The Factory" was erected near the dam. Although there was no actual manufacturing on the site, water power was used for carding wool and treating homespun cloth. In 1862 the Robinson Family, headed by Joseph Robinson, acquired a controlling interest in the mill and surrounding property. A year later Robinson began negotiating with farmers to purchase their land fronting the lake in order to raise the head of the dam two feet. Robinson paid a total of $5200 to 63 landowners. Shortly thereafter Robinson installed a new and sturdier dam with a raised head. For 150 years the Robinson Manufacturing Company was a successful manufacturer of woollen cloth.
During the 19th century, the crucial factor in controlling the outflow of water from the lake was the need for power to run machinery in the mill. It was water power that turned the wheels that drove the shafts and belts of cloth-making looms. In 1948, with electrical power available, the great waterwheel was shut down forever. The water so important for running the mill was used henceforth only in the washing and dyeing process.
The Oxford mill remained in the hands of the Robinson family for almost 150 years. In 2010 ownership was transferred to the Town of Oxford. Shortly thereafter, the Thompson Lake Dam Committee was organized with representatives from all four towns surrounding the lake—Casco, Otisfield, Oxford, and Poland. The Town of Oxford, with advice from this committee, has overall management responsibility for the safety and functioning of the dam.
(1) Much of this historical information is from Joan Madden and Margaret E. Slattery, The Thompson Lake Book: A Narrative (Lewiston, ME:1091), pp.23-29
2014 Water Level Report
June : Click here to view report
July : Click here to view report
View of booms on the lake side of the dam.
Walk way for dam maintenance
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