Collection System Inflow and Infiltration …
Jason & City Council, ….
Your memorandum report of I&I is a good start, but really all it is, is a start. My intent s not to be critical of your report but to have us take this start and complete a report and proper recommendations so that City Council can take the appropriate actions. As Manager Kisela has mentioned, Miami-Dade had spent well over $100 million dollars without any measurable results towards their I&I problem. I say had because Miami-Dade has begun to adopt the Best Practices as outlined in the January 2014 Florida Water Resource Journal written by Dr. Fred Bloetscher. Many Florida County and municipal water treatment utilities have adopted these Best Practices now. I had asked you if you had read the article before and you said “no”.
Here is an on-line link to the article. If you click on a couple of buttons you can make it full screen where it is easier to read.
For City Council members who may not know the industry I&I terms, inflow is rain water getting into the sanitary sewer and infiltration is ground water leaching into the sanitary sewer. To say that I know a little bit about the Dania Beach inflow abatement project featured in Fred’s article would be an understatement. I was on the smoke testing crews that smoke tested the entire city. I opened manholes and did inspections. I gathered GIS information, did inspection reports and exported data for Dania Beach to integrate into their GIS system. Locally, I did smoke testing and manhole inspections in Ormond Beach when Fred Costello was mayor. The manhole inflow dish, which I co-designed, that is featured in the article was the subject of an exhaustive engineering study by Miami-Dade. Miami-Dade is now purchasing thousands of these dishes and they do work well. The blue flexible polymer manhole coating that you can see pictured in the article was the result of a product we spun off from a company in Minnesota that I was a part owner in. I do know a little bit about I&I abatement.
I attached your report and it s a good start. It is a lot better information than when I first asked about it at the City Council meeting a couple of months ago. You have identified that Port Orange does have a costly I&I problem which is increasing our operating expenses. Before City Council should decide to authorize expenditures and go forward with any I&I abatement project, we should have a more detailed report and a complete project plan. I certainly would like to see you and your team complete the study for the entire Port Orange sewer system and provide a payback and rate of return numbers. In the Dania Beach study, Fred estimated a two year payback for implementing the “G7” program. With other cities, like Punta Gorda, the payback is more like 3 to 5 years. He also estimated an 85% savings or reduction in videotaping sewer pipes and some of the other expenditures that you have in your proposed budget numbers for 2014-2015. His recommended best practices (now adopted by many water treatment utilities in Florida) is to eliminate the inflow problem which will help isolate the infiltration problem. This was where Fred was estimating the 85% savings. At our last Audit and Budget board meeting, you were estimating in excess of $7,000,000.00 per year towards your capital project costs for the next five years. This totals in excess of $35,000,000.00. If we can even save half of that, or $17,500,000.00 through proper planning and Best Practices, we need to go that route. I am not saying we can save that much, but right now, I am sure we could realize a significant savings over the budgeted costs.
You made some assumptions and jumped to some conclusions in your memorandum that I may disagree with. You conclude that Port Orange has a ground water infiltration problem rather than an inflow problem because you see a “negative” flow in dry months. I think this was one or your statements or conclusions: ” A negative inflow rate indicates that wastewater is leaving the collection system rather than coming into the system.” Based upon the little bit of information in your report, I would conclude the opposite. I would have to see your numbers, but if you are comparing dry month flow to your “base line” flow, it would seem only natural that the dry month flow is less. From what I can see, your baseline flow for four months includes between 9 and 10 inches of rainfall. Any month with less rainfall than your baseline would naturally be less or “negative”. I am not disagreeing with your four month average baseline calculations. You will just need to also get a zero rainfall baseline to work with and do additional analysis.
Underground sanitary sewer pipes may need to be replaced or lined because of problems. This report did not include any information on actual breaks and construction costs to repair the breaks. That would be important information to have before deciding to spend money to replace underground lines. It would be nice to see a city map with pin points for all of the breaks over the past three years.
I also attached the Excel sheet that you had sent me with your raw Influent Flow. I was surprised to see negative flow numbers in the report. I asked you about those flows and you said that it was water flowing backwards through the pumps when the pumps shut-off. It may seem strange, but to me that indicated some malfunction. Maybe the pumps were defective or maybe there was a malfunctioning check valve. If I got the numbers correct, that could mean tens of thousands of gallons being re-pumped every day. If that were the case, any numbers of flow or peek flow that we would have may be suspect.
I for one am glad that we are looking into the I&I problem here in Port Orange. The smaller city of Dania Beach, according to Fred, was realizing a savings in excess of $200,000.00 in operating costs after implementing the “G7” program. We really do need to do more work though before we can make any proper assumptions and come to proper conclusions. I will be glad to discuss this further with you.
3606 Donna Street
Port Orange, Florida 32129