NHDES announces Nippo Lake, Barrington aluminum compound treatment
Concord, NH – The New Hampshire Department of Environmental Services announced today that it has issued a State Surface Water Discharge Permit (# Nippo Lake – 001) to the Nippo Lake Association (NLA) under the authority given in RSA 485-A13 I(a). The permit allows for the application of aluminum compounds to Nippo Lake as a lake management demonstration project. Aluminum sulfate and sodium aluminate will be added to Nippo Lake during portions of nine days from time period beginning May 24 through June 25, 2021.
The applications are currently scheduled to be completed on one day during the week of May 24, then on eight additional days during the dates of June 7 to 25. On each day of treatment all waterbody uses are restricted to activities authorized by the permit. Additionally, for 24 hours after each treatment, no swimming or water withdrawals are allowed.
The compounds being added to Nippo Lake, as prescribed, present little to no risk to human health, wildlife, or aquatic organisms. NHDES aquatic biologists will be on-site during each day of treatment monitoring lake water quality and ensuring the treatment proceeds as allowed by permit. The lake will then be closely monitored for several years to determine how effective this demonstration project was for substantial water quality improvement.
The purpose of adding aluminum compounds to Nippo Lake is to reduce by 80% to 90% the amount of phosphorus released from bottom sediments of the lake. Excess phosphorus from the bottom sediments has caused nearly annual harmful algal blooms in Nippo Lake, causing public health and safety concerns, as well as ecological concerns. The treatment will occur in all areas of the lake exceeding 15 feet deep. The total dose of aluminum applied will be 53 grams of aluminum per meter squared. The issuance of the permit follows on the completion of a watershed-based plan and actions for Nippo Lake and the successful removal of a majority of the external sources of phosphorus from the watershed to the lake.