Since 2013, when the West Harbor Pond Watershed Association (WHPWA) began testing the water quality from the surface to the bottom of West Harbor Pond, the water testing equipment retrieved from the lower levels of the Pond invariably brought to the surface an odor of hydrogen sulfide. When the replacement siphon began operating in March 2019, the hydrogen sulfide-laden water from the bottom of the Pond was discharged into the inner harbor, where it rose to the surface, giving off a distinctive odor of rotten eggs. (For more information on the siphon see the article “West Harbor Pond Siphon Beginning to Do Its Job.” posted to the Boothbay Register on April 24, 2020, https://www.boothbayregister.com/article/west-harbor-pond-siphon-beginning-do-its-job/133346).
Because of this odor, the WHPWA turned the siphon off on May 24, 2019 and did not restart it until Dec. 2, 2019. Since then, the odor of hydrogen sulfide at the outfall of the siphon has diminished so sharply as to be undetectable at present. Because of the large areas of ledge and beach that are exposed at low tide in and around the inner harbor, there is occasionally that low tide smell that all seacoast Mainers recognize. But the odor of rotten eggs is gone.
To try to understand why this is occurring, the WHPWA has since April been taking water samples from the bottom of the Pond at the siphon’s intake. When brought to the surface, these samples simply have no odor of H2S. This is the water that is being discharged into the harbor through the siphon.
With the understanding that the water that is being discharged into the harbor is now free of detectable amounts of hydrogen sulfide, the WHPWA’s Board of Directors has made the decision to allow the siphon to continue to run, rather than shutting it off on May 15th, as it had proposed last fall. Continuing to operate the siphon is critical to maintaining this positive water quality balance in the Pond and to ensuring that the conditions that gave rise to the odor in the harbor in 2019 will not return.
The WHPWA will continue to monitor the siphon discharge and, if an odor appears, will reconsider its decision to keep the siphon on. The WHPWA has informed the businesses on the inner harbor of its decision and has promised to respond promptly to their concerns should the odor return. At present the WHPWA believes that the siphon is doing its job of cleaning up the water at the bottom of the Pond, including the elimination of any trace amounts of hydrogen sulfide, and is doing so much sooner than anyone anticipated.