purpose of this project is to devise both technical and regulatory protocols
for delisting District lakes. There are
9 lakes on the 303(d) list of impaired waters.
There are two causes for listing: phosphorus/nutrients and mercury. The
Engineer has determined that both causes for listing are closely related. Release of both phosphorus and methyl mercury
(which gets into fish tissues) from sediments occurs where there is little to
no oxygen present. Delisting a lake is
technical and a regulatory process.
There is no defined delisting process for mercury. This Project will
establish technical and regulatory criteria for delisting a lake for mercury
Current Project Status
The 2012 Assessment Cycle Guidance Manual (MPCA) has been
reviewed. Communication with MCPA was
productive for both sides. Clarification
of the Guidance was necessary. Data has
been compiled to initiate the reclassification of Lakes Susan and Lucy as shallow
lakes. Discussions with the DNR
regarding mercury in fish tissue assessments have been completed. Technical approaches to improve lake water
quality and delist lakes have been identified.
A report, including recommendations, to the Managers is being finalized
in coordination with the Administrator for presentation to Managers. Preliminary recommendations include further,
more specific development of technical approaches to improve water quality and
delist each lake. This effort would
include developing a conceptual design and rough order of magnitude cost
estimate for each approach that could be used to delist each lake.