Ann Arbor Area Civic Document Repository

Report includes findings about FDD program:

“The FDD program on average removed about 65% of the wet weather peak flow in the target districts from the sanitary system. Four (4) of the five (5) target districts (Orchard Hills, Bromley, Morehead and Dartmoor) have a 90% or greater statistical confidence of significant flow removals. A map of the five (5) target districts can be found in the Volume 2: Flow Evaluation Report, page 5, Figure 1. The Glen Leven district appears to be less effective, with a flow removal rate of about 36%, and the reason for this is still unknown.”

“The FDD program reduced the risk of basement backups in the target districts to the point where additional FDDs are not needed in these districts to achieve the desired level of protection for the system. For example, prior to the FDD program, a large storm event would result in widespread sanitary basement backups, especially in the target areas. After FDD, during the large storm event that occurred on June 27, 2013, there were no reports of basement backups attributed to the sanitary sewer system, in the five (5) target areas. Several high-risk homes in these areas had check valves installed prior to the study. However, the sanitary flow metering data shows that the sanitary sewer depths did not fill the pipes in these areas, so it is unlikely that the check valves were active and needed during this storm.”