Page 61

              DO Improvement Feasibility Study
East Branch DuPage River 7.0 Evaluation
DRSCW 7-4 August 2008
Table 7-3 - Churchill Dam Modification - Advantageous Conditions
Dewatering Gate
The presence of the dewatering gate allows for a drawdown to
test the impact of upstream water surface elevation changes
without removal. It also allows for a controlled drawdown to
stabilize those sediments that have accumulated
upstream should the dam be removed.
Construction Access Access to the site for construction is excellent.
Upstream Water
Levels
Water levels upstream will decrease from removal, but the
majority of the riparian land upstream for quite a distance is
undeveloped, and lower water levels would
result in low aesthetic impact.
Lateral Work Area
There is a large amount of room to work in the reservoir area.
The few homes located along the reservoir have lengthy
buffers between any structures and the edge of the reservoir.
This creates a number of possibilities for restoration of
an intact stream and floodplain system, should removal be
considered.
7.2.1 Churchill Woods Dam Alternatives
Dam removal, partial removal, or bridging, and removal with constructed riffles all provide a
long list of benefits to the physical and biological nature of streams, each with its advantages
over the other when looking at specific portions of the system. Quantifying their impact on the
dissolved oxygen levels of the East Branch will be a major index by which the efficacy of each
option is evaluated.
Based on the advantageous and complicating conditions defined above, feasibility of
implementing each of the three dam modification alternatives, full removal, removal with
constructed riffles, and bridging or partial removal, were evaluated.
Full removal of the Churchill Woods Dam is a viable option. The dam has a dewatering gate
which could be used to slowly draw down the upstream impoundment that would allow for
deliberate management of impounded sediments. The extensive lateral work area would allow
for the restoration of a functioning stream and floodplain system through the old reservoir, as
well as the development of fishing ponds or wetlands as needed.
Removal with riffles is unnecessary in this situation. Natural riffles built for maintaining any
water surface elevation would not be required since lowering water surface levels upstream has
minimal impacts. Riffles could be installed for habitat or other uses as needed.