Robin Ordonez’s Role with Pierce County Public Sewer Utility
“As the Supervisor of Engineering for the Pierce County Wastewater Utility one of my first tasks was to develop the Engineering Standards and Specifications for the sewer utility. In the beginning the Pierce County Wastewater Utility didn’t have design standards or specifications. Previously the utility had used Washington State’s Department of Ecology standards. We decided to customize and tailor our specifications and engineering plans for our specific needs. We focused on the needs of the collection system and the maintenance staff. Anything that was to be constructed on the Pierce County sewer system would be according to these standard specifications.”
Specifying PREDL Systems’ Manhole Base Liners
“Beginning in 1985 I spent three years reviewing requirements and developing standards for the sewer utility that fit the engineering and maintenance staffs requirements. The maintenance manager highlighted the problems he had with manhole inverts. At the time Pierce County’s manholes were hand channeled concrete inverts. Every 5 – 10 years depending on location and concentrations of hydrogen sulfide gas and the extent of corrosion on the concrete inverts, Pierce County’s maintenance crews would have to re-channel manholes by jack hammering the inverts and installing new channels. Once we determined how much effort it actually took to re-channel a manhole we identified that as a pretty serious problem. The three point retrieval system; flaggers to control traffic; safety hazards due to H2S gas; and the risks of working in a confined space all added up to a costly, time-consuming unproductive use of maintenance crew resources.
“In 1989 I met a PREDL representative and learned about the benefits of their manhole liner system. He explained it was not really a new product. PREDL base liners were used extensively in Europe. I decided there might be an opportunity for Pierce County to solve one of our major problems with re-channeling manholes. Since I was responsible for writing specifications I included the PREDL liners on one of our public works construction projects. It was an alternative to the standard concrete channels. The contractor felt more comfortable with the standard channels so none of the manholes installed included the PREDL liner. On the next project I put out to bid, PREDL was sole sourced so the contractor had no alternative but to use the PREDL liners. Since then, over 20 years ago, more than 10,000 PREDL base liners have been installed on the Pierce County sewer system. Even today the PREDL liners are the only liner systems installed on all new construction projects. From our perspective the PREDL base liners solved a costly maintenance problem because after installation no additional maintenance is required on the liners.
With a sewer system of this magnitude maintenance costs are a very important issue.
“Maintenance crew time is very expensive when you consider all the effort that is needed to re-channel a manhole. The non-lined existing manhole requires a lot of resources to re-channel. At the minimum, Pierce County would have one worker inside the manhole to jack hammer and construct a new concrete invert, another at the road elevation to operate the 3 point retrieval system and a flagger at each end of the job. Depending on the flows in the system, it may require a crew to pump sewage around the manhole being rehabilitated and if it is located in an intersection additional flagging staff and possibly a deputy sheriff to direct traffic around the construction.”
“We began installing the PREDL base liners in 1989 and continue to do so today. They have proven themselves to be very good products. We have not had any call-backs on the product but maintenance staff at times admitted some liners needed repair due to dropping a tool down the manhole or a broken manhole lid dropping to the bottom of the manhole. Other than that we have had no issues with hydrogen sulfide, no corrosion issues, no leakage – from our perspective that problem was solved and no additional maintenance has been required on the liners.
Collection system crews were very aggressive chasing down Inflow and Infiltration conditions
“Inflow and infiltration, what we call I&I, was another area that PREDL’s manhole base liners helped us to control. Every gallon of I&I robs you of capacity on the collection system and the wastewater treatment plant. That is why it is so critical to have the system as tight as possible. The design standard of Pierce County’s sewer system allowed for 220 gallons per day of wastewater from each home. If you have a leak of one hundred gallons of I&I per minute you have displaced capacity in your collection and wastewater treatment systems which otherwise could service 655 more homes. One hundred gallons/minute equates to 144,000 gallons/day of lost capacity. A million gallons a day of wastewater treatment plant capacity costs $10 – $20 million alone.
Every gallon of Inflow and Infiltration you minimize or eliminate in the system is a gallon you don’t have to build in future expansion.
“Pierce County collections crews were very aggressive trying to chase down I&I and solve issues related to leaks into our sewer system – whether it was inflow from leaky manhole lids, or inflow from illegal connections like roof drains, or leakage into our sewer system from pipes and manholes that is an issue we took very seriously. In our collection system we looked at manhole covers, the different pipe types into the collection system, and the gaskets between the manhole joints. With PREDL’s system the pipe connection onto the bells of the manhole base liner is water tight. If you’ve got a tight system at these points you’ve eliminated potential I&I.
“I can tell you that in the city where I live there is a basin with a peaking factor that is 8:1 which is huge. When it’s raining because of all the I&I the flow volume is significantly greater. When you look at Pierce Counties’ sewer system we monitor flows on a 24 hour basis with flow meters at various points in our interceptor sewer system. We know in real-time what the flows are throughout the system.
“On our system when you take a look at the overall basin and the way we calculate I&I, the peaking factor is closer to 1.7:1. What that tells you is we have an extremely tight system because we have been aggressive in our I&I control. We have done everything to minimize inflow and infiltration into our system including manhole base liners. Typically, you design a sewer collection system for 3:1 peaking factor. Peaking factor is the relationship between average flow volume and highest flow volume. That standard is established as a design guideline by the State Department of Ecology. Effective I&I control is a combination of the efforts by I&I, TV and collection system crews during high or peak flows by actually going out and identifying potential leaks in our system and ensuring that those potential problems are identified and repaired as soon as possible.
“The permit requirements for wastewater treatment are continually evolving with further refinements in monitoring and measurement technology. They will not be less than they are today, they will only become more stringent. We are now more able to monitor and measure our processes and the eventual discharge that is released into our environment. Public sewer utilities will be held to higher levels of treatment in the future so it’s critical to minimize any kind of additional flows into the sewer system.”
Predl’s Inside Drop product makes it easier to design less costly sewer lines for varying elevations.
“Another issue we deal with almost daily with our collection system is the irregular topography of Pierce County itself. This can be a challenge especially with a gravity system. We have properties adjacent to a sewer line that are 5 – 10 feet, sometimes actually higher, above the collection line. On some connections into an existing manhole we allow sewer line construction higher than the main line provided that it can serve all connected properties within our standards and those connections are made with an Inside Drop. We don’t go into the base of the manhole as we normally would do and connect into the base liner. With an Inside Drop we go in much higher up in the manhole structure and still get the flow down into the channel with the drop structure.
“About 15 years ago we typically used a ductile iron Inside Drop. The “T” section alone protruded about 24” into the manhole so it took up a significant amount of the inside diameter of the structure. If an Inside Drop was needed we specified the inside diameter of a manhole to be 54” to make it easier and safer for our maintenance crews to get into and out of the manhole.
“In 1995 PREDL brought Pierce County an Inside Drop structure made from polyethylene. What I really liked about that particular piece of equipment was the size and weight. It was about half the size of the standard cast iron Inside Drop and weighed dramatically less. PREDL’s new Inside Drop allowed for either a 6” or an 8” drop. Based upon the much smaller size of the new drops we could specify up to two Inside Drops in a manhole structure 48” in diameter whereas, previously, when we had two ductile iron Inside Drops in a structure we required a far more costly manhole structure that was 72” in diameter.
”More importantly, the smaller Inside Drop made it much easier and safer for our maintenance staff to enter and work in a manhole. The polyethylene material is extremely durable making it virtually maintenance free. The form factor is functional and efficient at maintaining flow velocity without adding turbulence. We have an easy removable screw-on cap on the end so we can flush the lines and send our TV cameras through. Maintenance-wise PREDL’s new Inside Drop has been an excellent addition to the equipment we allow on our system. Total cost savings were significant because the polyethylene units cost less and they allowed us to accommodate single and multiple drops safely without increasing the size and cost of the manhole.”
The smaller Inside Drop made it much easier and safer for our maintenance staff to enter and work in a manhole. The polyethylene material is extremely durable making it virtually maintenance free..
“We searched to find the absolute best products for our sewer system whether it was the collection or treatment system. At the time, before we used PREDL liners, they had already been established in Europe. PREDL has great products and solved problems that had always troubled Pierce County.
“There was only one other manufacturer for manhole liners that approached me in the 20 plus years we had been installing the PREDL base liners. The manufacturer may have made a pretty good product, however, the problem with their product was they couldn’t meet our contractor’s demand to deliver product when it was needed. They could ship their products in bulk in containers, but they couldn’t customize the liners to the design of our sewer system. If all your roads are north and south and east and west you can standardize with a liner channeled consistently in four directions. Typically Pierce County subdivisions are designed based upon the topography of the land. Roads are curved not linear. Our liners have to be custom made to fit each location. PREDL can and has manufactured custom base liners with multiple channels and inlets intersecting from different angles.
“Another issue is the supplier’s delivery of the product to the precaster. If product is not delivered to the precaster on time, the precaster may have an issue with his turnaround time to the construction contractor. If the contractor is delayed, the project owner could endure additional cost because all of the equipment and labor are standing by onsite when the manhole liners were scheduled for delivery. From that perspective with PREDL Systems involved we always have great success with product delivery, quality, and consistency meeting our custom requirements. One of the reasons our sewer system construction projects kept rolling was PREDL’s dependability.
“Throughout my career I’ve had lots of manufacturer visits. Since we sole sourced the PREDL base liners on our system the concrete manufacturers have come and said “Look, I have a better product; it’s cheaper; we can include admixtures to the concrete and it will resist hydrogen sulfide.” My response has always been “Show me!” I need to see a public sewer system which has been using these admixtures or something that protects the concrete against hydrogen sulfide corrosion. Show me somebody who has used it for 5 or 10 years with no adverse impacts on the manhole invert. Until I retired I never had a manufacturer come back and show me, or give me names or references so I could contact people in a position similar to mine at Pierce County who have had that experience. I believe on being on the cutting edge of technology not the bleeding edge. It’s important to see documented proof that a product will work similar or better than what is currently specified in the system. PREDL did that originally in 1989 and since then no one else has demonstrated they have a better product.”