For the past several years Hubbell, Roth & Clark, Inc. (HRC) has provided assistance with implementing Wixom's annual Sanitary Sewer Evaluation Study (SSES), which is in response to two prior incidents of sanitary sewage overflows. The SSES work is a preemptive effort by the City, (SSOs) to identify, define, quantify and isolate wet weather flow, better known as infiltration/inflow (I/I), within the sanitary sewer collection system. The annual SSES has consisted of the following services provided by HRC:
Manhole Inspections
The purpose of individual manhole inspections is to determine the general physical condition of the manholes in the study area and note any defects that might allow the inflow of storm water runoff into the sewer system. The data generated from the manhole inspection is used to determine what manhole rehabilitation is necessary for removal of inflow.
The inspection procedure involved crews opening and inspecting individual manholes, paying particular attention to location of manhole, condition of cover, ring, frame, barrel, chimney, and evidence of inflow.
A report was prepared summarizing the findings and the manholes found to be in poor condition were repaired.
Smoke Testing
The main objective of this method is to detect inflow sources such as roof leaders; yard and area drains, abandoned building sewers; faulty connections; illegal connections and storm sewer cross connections. Structural damage and leaking joints in sewer pipes, and overflow points in the sewer system can also be detected during smoke testing.
A gasoline-powered air blower was used to force the smoke continuously into the sewer pipes. This allowed observation of smoke coming out of potential problem areas such as the ground, storm sewers, catch basins, roof drains, abandoned building sewers, damaged cleanout covers, etc. Observed smoke leaks were recorded with a camera and properly logged with dates, locations and description of results.
The public, as well as City Officials and the Fire Department, were notified prior to testing to minimize the confusion resulting from smoke appearing in and around dwellings. A day prior to smoke testing HRC staff passed out flyers to residents and/or businesses in the vicinity of the smoke testing notifying them of the pending activities. HRC also provided the City with notification information regarding the smoke testing for an area specific mailer, the City's web site and also the City's quarterly newsletter.
Internal Sewer Video Inspection (Sewer Televising)
Internal sewer video inspection was recommended in lieu of smoke testing in areas where the ground water table is high, since the smoke testing method would not be effective (the smoke escaping thru defects would not be able to reach the ground surface). The internal sewer inspection involves running a video camera through the sewers to identify any illicit connections, cracks, breaks, etc. To help ensure the best possible video quality, sewer cleaning (jetting) was recommended prior to televising the sewer.
The City contracted the internal video inspection services to another entity. HRC reviewed the videos and provided the City a report on the problems identified and recommendations for rehabilitation if necessary.
