New Law – fix the sewer inflow!
July 1 is the data that laws go into effect in Florida. Many times that are bills that are controversial or harmful. From a utility perspective we have one that is more interesting to read It deals with many things – blue green algae, regulation of septic tanks (a problem throughout the state), and sanitary sewer overflows, and increases fines to overflows (SB712/HB1343). The latter makes utilities notice. Basically, the bill is as a result of overflow flooding in Pinellas County several years ago. Utilities must now report of efforts to reduce infiltration, inflow and overflows. The bill does set up funds to help with the issue (50:50), but let’s look at what this means.
Substantial savings in operations can be achieved by reducing the amount of wastewater that must be pumped and treated. Utilities have long dealt with the infiltration and inflow (I and I) issues in their system by televising their pipes and identifying leak points, but this primarily addresses only the infiltration part of “I and I.”
Inflow, which creates hydraulic issues during rain events, leads to sanitary sewer overflows and can subject the utility to fines from regulatory agencies, and create publicity and legal issues when houses are damages from sewage backing up into houses and businesses. Where there are peaks in wastewater flows that match rainfall, inflow would appear to be a more likely candidate for the cause of the peaks than infiltration from pipes that are constantly under the water table. As a result, dealing with the inflow portion of I and I is needed. Inflow often can be identified and corrected easily, and removing the inflow portion from I and I, often leads to a more focused plan for infiltration correction program. An inflow program will consist of the following:
- Inspection of all sanitary sewer manholes for damage, leakage, or other problems
- Repair of manhole walls in poor condition or exhibiting substantial leakage
- Repair/sealing of chimneys in all manholes to reduce infiltration from the street during flooding events
- Installation of dishes in all manholes to prevent infiltration
- Installation of LDL® plugs where manholes in the public right-of-way or other portion of the utility’s system may be damaged
- Smoke testing of sanitary sewer system
- Identification of sewer system leaks, including those on private property (via location of smoke on private property)
- Low flow inspection event (Midnight Run)
- Documentation of all problems in a report to utility that identifies problem, location and recommended repair
- GIS mapping of manholes and problem areas
- Inspect the system for flow
- Determine if flow is significant.
If flow exists, open consecutive manholes upstream to determine where flow is derived from. Generally, a 2 inch wide bead of water is a limit of “significant” infiltration. The remainder is infiltration. Infiltration has a relationship between groundwater elevation values and flows which were developed using the Pearson product-moment correlation coefficient. This time the dependent value was the baseflow+infiltration and independent variable was the groundwater elevation. Since it was assumed that fluctuations in baseflow were negligible, any changes between baseflow+infiltration were assumed to be a result of fluctuations in infiltration. The first step is inspection of all sanitary sewer manholes for damage, leakage or other problems, which while seeming obvious, is often not the case. The manhole inspection documented condition, GPS location, ties to photographic data and some form of numbering if not currently available.
But televising lines does nothing for inflow -that is a surface issue. So let’s start the effort to address inflow first – as this will help ensure the goals of this new law are met.
Call me if you need help or have questions 239-250-2423.