Sweeney Lake Total Maximum Daily Load Study

Preliminary Data Observations
SEH
October 16, 2007

Sediment Core Analysis

Mixing and Phosphorus (P) Distribution

Historical dissolved oxygen (DO) and Temperature (Temp) profiles show that the lake had been mixed previous years with aeration
This year the thermocline kept the lake stratified-not mixed. (DO, Temp, and P show this.)
Previous years there was a summertime drop in DO, even with aeration
The lake went anoxic very quickly once the thermocline set-up. Quicker than most lakes due to highly enriched sediments
It appears we may have hit our P concentration limit below the thermocline in July, but we do not have enough data back yet to confirm (should get in next 2-3 weeks)
Depletion of phosphorus in the water above the thermocline can be seen in the P data, resulting in clearer water seen in Secchi depth readings
Due to clearer water (and possibly different temperatures) the lakes aquatic plants were noted to be different than years past by residents.
A large build-up of dissolved phosphorus occurred below the thermocline and we had concern about the bloom after turn-over (ultimately was not an issue)
Turnover occurred early and had to have a mechanical component to it….likely happened during period of large wind and/or rain events

In-flow data

We do not have the inflow data from period with storms and we have no flow data yet
Three Rives has collected on 3-4 events to date, plan to get a few more this year

Sweeney Lake
Total Maximum
Daily Load Study