WAPOGASSET/BEAR TRAP LAKE IMPROVEMENT DISTRI: RES-Wapogasset Lake Alum Treatment

The Lake Wapogasset & Bear Trap Lake Sanitary District is proposing to conduct an aluminum sulfate (alum) application to the waters of Wapogasset Lake in Polk County. This lake management procedure has been recommended in a previous Lake Management Planning Grant project report as a method to decrease the level of late summer phosphorus concentrations in the lake due to the in-lake recycling of nutrients from the bottom sediments. The alum will be applied to the lake surface via a barge with surface application spray bars.

This grant application proposes treating two lake areas; (1) the area with water depth of 5 to 15 feet is proposed to be treated with a dosage rate of 5.1 ppm alum, and (2) the lake area with depths of greater than 15 feet to be treated at a dosage rate of 40 g. alum/ sq. m.. The Department of Natural Resources has determined that the treatment of the 5 to 15 foot depth area is ineligible for Lake Protection Grant cost sharing, because of a review panel consensus opinion that the effectiveness of alum for controlling phosphorus release from shallow, oxic lake sediments has not been well documented.

The application of alum will be restricted to a time period from July 15 to freeze up and the Lake Wapogasset & Bear Trap Lake Sanitary District must notify the Department of their treatment plans at least two days prior to application. The District must submit a report to the Department, after treatment, detailing the time of treatment, locations covered, rate of treatment, and total amount of alum applied.

Activities

• Lake Management Plan Development
• Lake Management Plan Development

People/Organizations Involved

• Wapogasset/Bear Impr Assn