Core Sediment Analysis
The ‘Core Sediment Analysis’ explains that decaying organic material eroded from the shoreline is the cause of the Lake becoming ‘impaired’ for aquatic life. This condition, termed anoxia or low dissolved oxygen (O2), stimulates plant growth and, if unchecked, can lead to algae and cyanobacteria blooms. It’s the reason the Lake has less game fish, more aquatic plants and ‘muck’ than in the past. While we can’t reverse what’s happened, we can slow or stop these damaging changes.
Decaying organic material consumes O2 and generates carbon dioxide (CO2) which promotes plant growth. As more plants decay, more O2 is used leading to anoxia. Game fish can’t live in this low O2 environment. Conversely, a high CO2 environment benefits plant growth which, as noted above, can lead to toxic and nontoxic blooms.
The lake’s water level has been raised by damming for 200 years. According to a DOT study, Spofford Lake’s summer water level is 4 feet higher than the lake’s natural water level. Higher water has eroded the shoreline, forming layers of decaying, organic rich sediment. In fact, the Core Sediment Analysis shows that “after…1980 the amount of organic material reaching the lake bottom exceeds that of any prior time period;”
The Report's conclusions are given on pages 15 & 16. Please take a minute to review them. The underlying science for these conclusions is given, in some detail, on the preceding pages.
Here's a short, one page info sheet on the history of the Lake's water level.
This report was done in 2013 as part of the improvements done to Route 63 in 2013. It's very comprehensive and provides an important historical perspective on Spofford Lake's water level over the past 200 years.
Sediment Lead Levels: The Core Sediment Analysis also found an increase in lead levels in the lake sediment from 1980 through 1998. (See pages 14, 15 & 17 in the above report.) The lead source, according the analysis, is most likely leaded gasoline leaking from an underground tank. Lead concentrations in Spofford Lake reach a peak in 1996 and show a much different pattern than those of other lakes. Spofford Lake's lead levels then fall in subsequent years, mirroring the profile of these other lakes.
A toxicologist with the NH DES Environmental Health Program subsequently reviewed these findings. His conclusion is that "Based on the available data there doesn't appear to be a health risk due to sediment contact..."
Please contact us if you want additional information.