DEVELOPMENT OF INFLATABLE DAM DESIGN PARAMETERS AND CONTROL SCHEMES USING THE TRANSIENT ANALYSIS PROGRAM

The Detroit Water and Sewerage Department (DWSD) is currently constructing thirteen (13) insystem storage devices in large trunk sewers to minimize combined sewer overflow (CSO). The total amount of ISS to be provided is 54 million gallons (MG) for the 13 devices.The ISS devices will be inflatable dams which will be operated to store wet weather sewage flows and reduce CSO, especially for smaller storms that would not otherwise utilize the flowing full capacity of the trunk sewers.An important design criterion for the project was to minimize the number of level sensors required, since level sensors need frequent maintenance to be reliable.Design parameters and control schemes were developed and tested with the Transient Analysis Program (TAP). The analyses showed that DWSD's design criteria can be met by carefully selecting the ISS dam design parameters and control schemes. Dam inflation/deflation rates in the range of 0.5 to 1 foot per minute were determined to be acceptable.The analyses determined that nine (9) ISS dams will require an upstream and a downstream level sensor. Four (4) ISS dams will require only an upstream level sensor since these dams are within the backwater zone of another ISS dam and can utilize the lower ISS dam's upstream level sensor for control.