Sanitary sewer systems are designed to transfer bio-waste materials from point “A” to point “B” in a closed system without contaminating the surrounding environment. SSO’s (sanitary sewer overflows) occur when the designed system has reached its maximum limits of capacity and sewer water is then forced out of the system into the environment contaminating the surrounding area. One of the leading factors driving SSO’s is I&I (Inflow Infiltration) from outside storm water or ground water entering and penetrating into the closed system. Over the years the system becomes aged and deteriorated allowing points of infiltration and exfiltration meaning sewer water leaks out into the environment as well as allowing excess storm water to enter the system. This program focuses on how I&I directly impacts SSO’s and through cost effective manhole/lift station rehab can significantly reduce I&I and SSO’s by as much as fifty percent. This will dramatically lower daily operating costs and will restore lost capacity in the system. Before costly plant upgrades are considered systems should maximize every bit of potential capacity in the existing system to be as efficient as possible plus it’s already going to be a future incurred cost to upgrade these aged structures anyway so you might as well capture a rate of return sooner than later.
The sewer system is comprised of four components which are the carrier pipes, manholes, lift station or pump stations, and finally the treatment plant. The manholes and pump stations are the only part of the system that is at ground level and at pipe level. The reason that it’s important to know is because these structures allow infiltration at all levels of the system. During rain events the first points of penetration are as follows:
- The ring and cover
- The joint between the ring and cone
- The joint between the cone and barrel
- The joints at each barrel
- The knock outs or pipe penetrations entering the manhole
A single rain event can create such head pressure that is forces its way in to all these points during the rain and after the rain water settles into the ground. If a water table exists then constant infiltration is pouring into the system regularly.
To quantify how this impacts your daily operations cost take a modest assumption of one gallon per minute leak review the numbers below.
1 gallon per minute x 60 minutes x 24 hours x 365 days= 525,600 gallons per year
If your total treatment costs are $3.00 per thousand gallons then you’re looking at:
525,600/$1000=$525.60 x $3.00=$1576.80 per manhole annually I&I cost
If you take a system of 300 manholes you’re looking at 300 x $1576.80 = $473,040 annually
This figure does not take into account the additional cost to run your system pumps longer to keep up with these additional flows nor does it include costly EPA/TCEQ fines for SSO’s or catastrophic complete failure of the structures while in service.
If you have an old aged sewer system to begin with than you will be upgrading your manholes sooner than later the faster you rehab/upgrade and seal your manholes and pump stations the sooner you will lower your daily operational cost freeing up a large portion of money not to mention you will be taking back additional capacity in your system. The rate of return to perform manhole rehab is approximately 24 months. This is the only system upgrade that will yield this type of return on investment and is the least costly program to fund. Plant upgrades and pipe procurement projects range in the millions while proactive manhole and lift station rehabs are a fraction of those costs.
Southern Trenchless has developed a cost effective low impact trenchless solution to procure these issues. What we do is seal up the entire inside of the existing leaking manhole or pump station with a monolithic ultra high strength repair mortar called Manhole Mortar. What this does is creates a water tight cast in place structural liner that can yield up to a 10,000psi compressive strength which is close to 300% more than required by TxDot, TCEQ, and most municipalities in Texas. This product can withstand greater amounts of H2S gas content, which is the leading cause of premature failure which allows this product to extend the existing structure service life by as much as double without costly remove and replace. The majority of the rehab can be done without normal service disruption and most manholes take less than 2 hours to rehab with this method lowing the safety risk factors and exposure. If greater H2S exposure is an issue than a 100% solids epoxy coating may be required to protect the exposed mortar from this aggressive attack. I this case either new or existing manholes can be coated with this material to double or triple the service life of the structure which will also yield a higher return on initial investment. The two products mentioned are the most successful and cost effective year to date in the United States. The largest manhole contracts in the world which have all been in the United States have ALL used these particular products because they are by far the most proven and most cost effective for sustainability.
Quality Control Measures
Quality assurance that these products are installed correctly is the key element to a long lasting result. It is the responsibility of the owner to insure that proper certifications such as ACI Shotcrete Nozzleman and other industry standard certifications are injected into the language of the specification to insure quality control measures to installation. It is also imperative that proper application methods are carried out as defined by industry standards such as ASTM, NACE, NASSCO, ACI, and other industry leaders for these products. Educating your staff will also be vital to the overall success please let us know if we can setup a lunch and learn or presentation. Please visit us at www.SouthernTrenchless.com for more information.