Injection grouting in mainline sewers has been around for more than 50 years. It is a solution to eliminating infiltration at the joint – once sealed – and provides a significant reduction in overall inflow from ground water.
This trenchless rehab method is most effective when operators are well-trained and proper procedures are followed. To help ensure that happens, it is important to have a training protocol that follows the correct procedures and a trainer who has many years of practical experience.
Equally as important is a tight specification from the customer – oftentimes a utility owner – that is detailed and requires all parties to be held accountable. This accountability includes operators to grout properly but also for the utility to have an inspector who is trained to oversee grouting and who will be in the truck on a regular, if not daily, basis. Grout times, temperature and gel times are critical but so is testing every joint (and laterals if applicable) to see if they pass the air test.
The specification should be written with qualifications that include references, a certain number of joints per contract, as well as overall experience for the company. It should also require the operator’s experience. Included with the reference a service provider should be required to provide a proper procedure for testing and sealing joints and laterals as part of the submittal.
NASSCO, and in particular its Infiltration Control Grouting Association (ICGA) Division, is in the process of drafting proper procedures and a specification language for operators, engineering firms and utilities. The IGCA is also working diligently to create certification for the operators and inspectors. The certification would be similar to NASSCO’s MACP and LACP programs. A white paper from the ICGA committee is comprehensive for many of the topics discussed here. There are also several case studies that will help certain readers to consider enacting a comprehensive injection grouting program.
Those interested in learning more can visit sewergrouting.com/ppt/icga_whitepaper_wastewater.pdf to review the white paper.
Entering the Computer Age
Technology also plays a vital role in assisting the test and seal process. Today, many grouting trucks are equipped with a software-based control panel unlike mechanical and pneumatic panels of the past.
The old legacy mechanical panel looks like something you would see in a submarine. It is large and cumbersome to learn, featuring knobs, dials and switches that control the grouting process. While it still does the job, the old systems are not practical in today’s construction industry, which is facing worker shortages making it imperative that contractors cross-train their employees and train new ones – many of whom are more adept at using computer-based programs.
The software-based panel known as the Easy Grout System from CUES speeds up the training process from several days to a few hours. This is in part due to its single-screen design featuring an operating system that allows for point and click functionality. The electronic panel communicates with the electronic and pneumatic components located in an enclosure inside of the truck. The panel enables the versatility to operate pneumatic or electric pumps, mainline and lateral packers, provides a tool tip function and can be measured in metric or standard. Using a software based control system enables tablet/wireless control with WI-FI. This gives the operator the versatility to work from an office in the truck or trailer or remotely.
By using a software-based program, default features are set that include recommended packer pressure by pipe diameter and air test pressure by pipe depth as derived from ASTM F2304 “Standard Practice for Sealing of Sewers Using Chemical Grouting.”
To better explain the process, a camera and packer are pulled through a sewer main by a winch located down line from the grout truck. The camera helps to line up the packer and for additional observations. Once the packer is lined up over the pipe joint it is inflated to the recommended pressure and an air test is conducted. If the joint fails to hold pressure (a drop of 1 psi over 15 seconds) then the operator injections grout into the void. Other factors that are critical to a successful seal is a proper mix for a controlled gel time and pumping a sufficient amount of grout (approximately 1 gal per 2-in. diameter of pipe).
Using a software based system enables the operator and inspector to see on a graph, called a graphic user interface, pass/fail, in real time. The intuitive screen will also show grout per joint and grout per day totals. This also aids the operator to record this information in any condition assessment and observation software. In addition to the software end of the system, those who are making a capital investment in purchasing a grout truck or trailer should factor in warranty, customer service, repair and lender programs.
Any components that come in contact with grouting material should be a high grade stainless steel. Trucks should also offer hose reels in various lengths, clearly marked grout tanks by color and amount in gallons located on front of tanks, ample storage for packers, grout material, winch, power cords, compressor, tripod, generator and workspace. Workspace ergonomics increase productivity and improves safe operation. Consulting with design experts from the manufacturer will offer recommendations and custom designs to meet your needs.
Whether you are a new or experienced operator or inspector a grout school should be a must-attend event. Several times a year, grout material, packer and truck equipment manufacturer’s partner to offer these workshops. The workshops are typically two days in length and provide comprehensive classroom and hands-on training. There is a certificate issued upon completion of the course.
The most effective and successful grouting programs have comprehensive specifications to protect the owner, contractors who receive proper and recurrent training and ample support from the equipment and material manufacturers.