The Detroit Water and Sewerage Department (DWSD) developed a Long-Term Combined Sewer Overflow (CSO) Control Plan (LTCP). The LTCP addresses control of discharges from CSO outfalls, which discharge to the Detroit River and the Rouge River. One component of the Plan is the Conner Creek
PilotCSO Control Facility (Facility), which discharges to the Detroit River. In lieu of following the State of Michigan Department of Environmental Quality's (MDEQ's) presumptive criteria of 30 minutes of retention time for the disinfection of CSOs resulting from the 10-year, 1-hour storm,
the DWSD negotiated with the MDEQ to study, design, and construct apilotCSO treatment facility using high rate disinfection (HRD) to achieve daily and monthly fecal coliform limits of 400 and 200 colony forming units per 100 milliliters (cfu/100 ml), respectively, with five minutes of contact
time at the 10-year, 1-hour peak flow of 13,262 cubic feet per second(cfs). If this 30-million gallon "pilot facility" can meet the fecal coliform limits, it may allow for significant cost savings in CSO treatment. As part of the agreement with the MDEQ, this pilot facility is currently undergoing
two years of intensive monitoring to confirm that the permit objectives are being consistently met through the use of HRD. The objective of this paper is to review the back ground of HRD as it generally relates to CSO, the challenges posed in the design and operation of the Conner Creek
CSO Control Facility, and to review the lessons learned from operation and monitoring of the "pilot" Facility. Specifically, how the appropriate design criteria was determined for storage, feeding, and mixing ofsodium hypochlorite with CSO to achieve the monthly fecal coliform limit of 200
cfu/100 ml with 5 minutes of contact time, and how the implemented design has performed during full scale operation.
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