There are several factors that affect the length of time. The amount of impurities that were introduced during the overflow, water levels and temperatures (hot weather) are major factors. It is generally best to stay away from discharge points (no swimming or contact with water) for several days.
Signs are posted near all overflow points alerting the public that this is the location of a CSO outfall. This means that the potential for an overflow could exist during rain events and excessive snow melt.
The City expanded your wastewater treatment facility in 1996 to be able to handle 3 MGD (million gallons per day). Previously the treatment facilities would handle around 2.5 MGD during storm events. Total cost of these improvements was 1.4 million dollars.
The City made operational changes to the treatment facility in 2008 to increase flows up to 3.5 MGD.
The City also has done extensive smoke testing to identify problem areas in the sewer system. This was done so the City could develop a Downspout and Sump Pump Program. The purpose of this program is to eliminate clean water connections into the sewer system. These clean water connections (sump pumps and roof downspouts) put storm water into the sanitary sewer system at a rate that is much higher than sewers can handle and cause back-ups and overflows.
The City is currently developing a CSO operational plan, which will be submitted to the Ohio Environmental Protection Agency (OEPA) for approval. The plan includes nine control strategies, which can reduce frequency of discharges and minimize capital expenditures. These nine controls are:
1) Proper operation and regular maintenance of the sewer system and CSOs.
2) Maximum use of the collection system for storage.
3) Review and modification of pretreatment requirements.
4) Maximize flow at the treatment facility.
5) Prohibition of dry weather overflows.
6) Control of solid and floatable materials in CSO discharges.
7) Require pollution prevention programs focused on reducing the level of contaminants in CSOs.
8) Required inspection, monitoring and reporting of CSOs.
9) Public notification for any areas affected by CSOs.
CSO systems overflow during periods of rainfall and excessive snow melt.
A combined sewer system has pipes that collect both storm water runoff and sanitary sewage. Combined sewers have existed in Upper Sandusky since the early 1900’s and at that time all combined sewers drained directly or indirectly to the Sandusky River. It was not until the early 1950’s the Upper Sandusky constructed a wastewater treatment facility.
Some of these early combined sewers are still in use today. During dry weather these combined sewers transport wastewater directly to the sewage treatment facility. In periods of heavy rainfall or excessive snowmelt, the wastewater volume in the combined sewer system can exceed the capacity of the sewer system or the treatment facility. For this reason, combined sewer systems are designed to overflow occasionally and discharge excess wastewater directly to the Sandusky River. With these overflows, pressure is relieved from the sewer system thus helping to prevent back-ups in basements. These overflows are called CSO’s.