TMDL Implementation Plan October 2006
Highland Silver Lake (ROZA)
Limno-Tech, Inc. Page 13
The approach to be taken for TMDL development and implementation is based upon
discussions with Illinois EPA and its Scientific Advisory Committee. The approach
consists of the following steps, with the first three steps corresponding to TMDL
development and the latter two steps corresponding to implementation:
1. Use existing data to define overall existing pollutant loads, as opposed to
developing a watershed model that might define individual loading sources.
2. Apply relatively simple models (e.g. BATHTUB) to define the load-response
relationship and define the maximum allowable pollutant load that the lakes can
assimilate and still attain water quality standards.
3. Compare the maximum allowable load to the existing load to define the extent to
which existing loads must be reduced in order to meet water quality standards.
4. Develop a voluntary implementation plan that includes both accountability and
the potential for adaptive management.
5. Carry out adaptive management through the implementation of a long-term
monitoring plan designed to assess the effectiveness of pollution controls as they
are implemented, as well as progress towards attaining water quality standards.
This approach is designed to accelerate the pace at which TMDLs are being developed
for sites dominated by nonpoint sources, which will allow implementation activities (and
water quality improvement) to begin sooner. The approach also places decisions on the
types of nonpoint source controls to be implemented at the local level, which will allow
those with the best local knowledge to prioritize sources and identify restoration
alternatives. The Association of Illinois Soil and Water Conservation Districts, using
Section 319 grant funding, have made available a Watershed Liaison to provide
educational, informational, and technical assistance to local agencies and communities.
The liaison can assist in establishing local watershed planning groups, as well as acting as
an overall facilitator for coordination between local, state, and Federal agencies. The
adaptive management approach to be followed recognizes that models used for decision-making
are approximations, and that there is never enough data to completely remove
uncertainty. The adaptive process allows decision-makers to proceed with initial
decisions based on modeling, and then to update these decisions as experience and
Steps One through Three described above have been completed, as described in the
TMDL report (LTI, 2005). This plan represents Step Four of the process. Step Five is
briefly described in the last section of this document, and will be conducted as
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