“Accelerating Construction in Sewer Collection: Madison CMIC PumpStation #1 A Case Study”

By Eric Zimmerman, Sherwin Williams Protective Coatings, Denham Springs, LAand Jennifer Sloan-Ziegler, PhD, PE.; Waggoner Engineering, Jackson, MS

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Presented at Coatings+ 2019February 11 - 14, 2019

Orlando, FL

OATINGS+February 11 - 14, 2019 | Orlando, FL

Accelerating Construction in Sewer Collection: Madison CMIC Pump Station #1 A Case Study

Eric Zimmerman, Sherwin Williams Protective Coatings, Denham Springs, LA Jennifer Sloan-Ziegler, PhD, PE.; Waggoner Engineering, Jackson, MS The County of Madison, MS. experienced severe degradation of a major pump station in their system that was less than 10 years old. They contracted with Waggoner Engineering of Jackson, MS. to design a rehabilitation system as well as increase the structural integrity with the addition of some support walls. The project created scheduling issues due to the addition of new concrete structures to the pump station. The use of innovative coatings technologies that offered the ability to apply corrosion resistant linings over green concrete structures, dramatically enhanced the project schedule and reduced overall costs. The authors will seek to explain the background that lead to the rehabilitation required, the team work employed by the engineer, coatings manufacturer and applicator to accomplish the rehabilitation. Technically we will explain urethane concrete technologies and their inherent advantages as a MVE barrier in new construction and rehabilitation projects as well hydrogen sulfide resistant 100% solids epoxy coatings for use in sewer collection and wastewater applications. Learning Objectives/Outline:

• Case Study Background (condition, background, specification) • Costs Associated with bypass pumping and downtime in sewer rehabilitation • Green Concrete/MVE & Why it’s an issue for coatings systems • Urethane Cement Technology Advantages in Reducing Construction Schedules • H2S Resistant 100% Solids Epoxy for Asset Protection in Sewer Environments • Outcome & Results

BACKGROUND and COSTS Madison County, located in central Mississippi, has one of the fastest growing populations in the state. In the twentieth century the county saw slow, but steady, modest population growth; that changed in the mid-1980’s. Since 1984, the population in Madison County has grown approximately 250%, and the population growth does not show signs of slowing down any time soon. In fact, over the past five years alone, Madison County has seen a population growth of over 8%. Foreseeing this continued trend in population growth, and wanting to plan for the future, the Madison County Board of Supervisors (Board) commissioned a countywide study to develop a master plan for sewer infrastructure in the County. And thus, in 1998, the idea for the Madison County Wastewater Authority (MCWA) was born. The Board adopted the master plan in 2001 and MCWA was officially created by the Mississippi Legislature that same year. MCWA was formed in 2002. MCWA provides service across Madison County and is comprised of several utility organizations including Bear Creek Waster Association, Canton Municipal Utilities, the City of Madison, the City of Ridgeland, Pearl River Valley Water Supply District, Lake Lorman Utility District, Madison County, and West Madison County Utility District. Prior to the regional wastewater system, there were several areas where residential development was restricted, and even prohibited, due to lack of wastewater infrastructure. With the inception of MCWA and a regional wastewater system with ability to expand to meet consumer needs, development restrictions were lifted and the County has continued to grow and prosper.

Since 2002, MCWA has constructed over sixteen sanitation projects ranging from the eight million gallons per day Beatties Bluff Wastewater Treatment Plant to 37 miles of large diameter wastewater lines across Madison County. In 2011, Canton Municipal Utilities (CMU), a member of MCWA and the system operator, began reporting problems with the Central Mississippi Industrial Center Pump Station 1 (CMIC PS1) to the MCWA Board. At a February 2016 MCWA Board meeting, CMU reported that after enduring numerous pump station failures and other issues, conditions at CMIC PS1 had become critical and without improvements to the pump station, sanitary sewer overflows were likely to occur. At that meeting, MCWA declared an emergency and requested the Mississippi Engineering Group Inc., of which Waggoner Engineering is a partner, to investigate needed improvements at the pump station. The CMIC PS1 is located east of Interstate 55, south of intersection of Church and Old Jackson Roads in Madison County near Gluckstadt. It was constructed in 2002 by Madison County Economic Development Authority and conveyed to MCWA in 2005. CMU has served as the operator since that time. CMIC PS1 discharges into the Catlett Road Force main which meets up with a force main from the Nissan Canton plant and then flows to Beatties Bluff Wastewater Treatment Plant (see attached system map). This system is a crucial component of the regional transmission system. In addition to a gravity collection system serving nearby Tier 1 suppliers of Nissan and receiving flows from Bear Creek Water Association, flows from CMIC PS 2, Post Oak PS, Twin Harbor PS, and Haley Creek PS are all transported to and received into the wetwell of the CMIC PS1, where they are repumped. As such CMIC PS1 provides service to the following MCWA members

• Bear Creek Water Association, • Canton Municipal Utilities, • City of Madison, and • Pearl River Valley Water Supply District.

The station originally included 3 pumps, 150 horsepower each, each one capable of providing 2,500 GPM vs 142' TDH (Total Dynamic Head, an indication of pressure). The station was sized to accommodate a future fourth pump, if necessary. Figures 1 and 2 show the pump station and pump configuration.

Figure 1 - CMIC PS #1 Figure 2 - Pump Configuration

Since taking ownership of the station, MCWA has operated it as an integral part of the MCWA regional wastewater transmission system. This means that instead of CMIC PS1 operating as it was designed, as a lone pump station, receiving gravity flows from nearby customers and delivering through a 10-mile long force main to inject flow into the Varlilia Road Force Main, it now receives pumped flows from as far away as the shores of Barnett Reservoir

and shares its long force main with several other pump stations. These circumstances result in long residence times and noxious gases/odors in the wetwell, as well as extremely varied force main pressures that cause the pumps to have to operate at the extreme ends and beyond their operating ranges. Because of these factors, the station has suffered from numerous problems including multiple pump repairs/replacements and deteriorating wetwell conditions during its service life. At the time of the declared emergency, the CMIC PS1 was equipped with two dissimilar pumps of the following apparent capacities:

• Pump #2 - approx. 450 gpm @ 110' TDH • Pump #3 - approx. 1000 gpm @ 115' TDH

In response to the emergency declaration, CMU installed a data logger on February 12, 2016 to collect wetwell water levels, force main pressures, and pump on/off timestamps. Data was collected from February 12, 2016 through February 25, 2016 producing nearly 1,400 pages of data for analysis. This representative sample information was needed to calculate the hydraulic conditions the station experiences. In addition to numerous pump issues, the engineering review revealed numerous deficiencies with the structure of the wetwell. The concrete wetwell had experienced erosion of the concrete, likely due to sewer gases and ozone generation that was previously used for odor control. As shown in the following pictures, the wetwell experienced continued deterioration from March 2011, when an initial investigation was performed. The concrete and steel lost from the wall was a possible source for debris found in the pumps when being repaired in 2016. This debris was being pumped into the force main which could have potentially created a larger issue with the overall system.

Figure 3- Wetwell Condition 2011 Figure 4 - Wetwell Condition 2011

Figure 5 - 2016 Wetwell Condition Figure 6 – 2016 Wetwell Condition

Following the 2016 engineering review, short term recommendations were made for emergency implementation. These recommendations included:

• Structural repairs to the wetwell – with an additive alternative to install a support wall in the middle of the wetwell, if necessary,

• Installation of a protective coating system in the wetwell, and • Installation of two 100 horsepower pumps capable of 2,000 gpm during normal conditions.

Construction for the emergency improvements began in June 2016. After beginning bypass pumping for wetwell improvements, a thorough structural inspection transpired. Through the structural inspection, it was decided that the additive alternative to install a support wall in the wetwell was necessary to maintain structural integrity of the wetwell due to the severe degradation of the concrete and rebar. Additionally, power washing the wetwell walls to clean them for the coating application revealed more damage than previously thought as the power washing frequently resulted in concrete being removed from the wall. The figure below shows the extent of the damage on a cleaned section of the wall. Rebar, in both directions, can be clearly seen. At some places in the wetwell, rebar was completely exposed and no longer attached to the concrete.

Figure 7 – Wetwell Wall Degradation, 2016

The activation of the additive alternate triggered a change order to the construction contract, adding thirty days, $30,000 for additional bypass pumping (an addition of 20% of the original bypass pumping budget), and other costs for wetwell structural repairs. Within these thirty days, the center wall was to be constructed and coated, and the wetwell surface was prepared and resurfaced, as well as a corrosion inhibitive epoxy to cover the exposed rebar prior to the cementitious coating application. Throughout this project, remaining on the very tight construction deadline (150 calendar days with 50 days originally planned for bypass pumping) was imperative to reduce the cost of bypass pumping and to restore full service to CMIC PS1, which is vital to overall MCWA wastewater system functionality. While remaining on schedule was imperative, so were the use of quality products to ensure CMIC PS1 would not have to be taken offline in the future for additional repairs. When the additive alternative requiring the center wall construction and additional covering of the rebar was triggered, the need for structural concrete occurred. Within the specifications, a 28-day compressive strength of at least 4,000 psi was the governing factor. Sherwin Williams, MSEG, and the contractor worked together to find solutions to adequately protect the rebar before adding additional cementitious material and to reduce the curing time of the center wall. GREEN CONCRETE & ITS ISSUES Most technical specifications and most manufacturers’ literature, calls for a minimum 28 day curing period prior to the application of polymer based coatings and toppings. The technical basis for this recommendation of the relationship between time and the cement hydration process which is directly related to compressive strength development, and is measurable. Plain concrete is proportioned to develop 80% of its design strength in 7 days and 100% of its design strength in not more than 28 days, (Concrete containing fly ash is 56 days). This measurement tells us that the cement used in mixing the concrete has for the most part completed the hydration process, although, hydration will continue for years to a lesser degree. This measurement does not, however, define for us the relationship of the aged concrete to the remaining excess moisture content. It is interesting to note that cement requites no more than 22% to 28% of its weight in water to fully hydrate, i.e., a w/c ratio of .22 to .28. With this amount of water, the concrete would be totally unworkable

for everything. other than dry-packing. For this reason, additional water is added to the mix to make it more useful. This excess water, is referred to as water workability or water of convenience, A typical 3,500 p.s.i. mix design, with standard air entraining and water reducing admixtures, might have a cement content of 470 lbs. per cubic yard, and a water demand of 188 lbs. or 22.6 gallons (water weighs 8.33 lbs. per gallon), to achieve a required w/c ratio of .40. This mix design would then have an excess w/c ratio in the amount of .15 (.40 - .25). By multiplying the excess ratio (.15) by the weight of cement (470 Ibs.), we arrive at a calculation of 703 lbs. or 8.5 gallons of excess water that will not be consumed by the hydration process. This excess water must be allowed to escape, while maintaining adequate moisture (curing), for the hydration process. Much of the excess water will escape through capillary action i.e., bleeding, while the concrete if in its plastic state during consolidation and finishing operations. (Concrete 101; 2012 Sherwin Williams Company) It has been estimated that 80-90% of all failures in concrete finishes are due to moisture related problems. Moisture related problems with polymers on concrete may be categorized as follows: HYDROSTATIC PRESSURE CAPILLARITY VAPOR EMISSION GASSING HYDROSTATIC PRESSURE - A distinct head of water exerting pressure against a concrete structure. The weight of the water creates the pressure and is dependent on how the height or column depth is. An example of this would be a below grade structure that experiences moisture intrusion problems during a rain storm. Another example would be a high water table exerting pressure on the underside of a slab on grade. CAPILLARITY - Moisture pulled through the concrete by the attraction created when a distinct moisture source comes in contact with the fine hair like openings in the porous concrete surface. The action may go up, down, or vertical and is attracted by warmth and dryness. VAPOR EMISSION - Water in the vapor or gaseous state as the result in natural occurrence, and may not originate from a distinct water source. This is the means by which all concrete breathes and releases moisture. GASSING - A temporary condition usually occurring during installation of coatings, and usually with urethanes and methacrylate, when components are incompatible with moisture in or on the concrete. A chemical reaction takes place where carbon dioxide is formed in a gaseous state and rises to the top of the uncured liquid resin. A phenomenon often incorrectly referred to as gassing, or out gassing, is the formation of air bubbles in a primer or coating, caused by displacement of air in the concrete or release of entrapped air created during the mixing of the polymer product. The aforementioned moisture related problems present themselves as blisters, voids or pinholes in the surface of the coating or topping. If severe enough these blisters may cause delamination of the surface, which is often progressive, and total failure of the system. In the situation the authors were addressing, a frequently immersed pump station with high H2S levels, any void or breach in the coating caused by a pinhole our blister would allow for toxic gasses to reach the host substrate and begin the corrosion process of the asset at a greatly accelerated rate. URETHANE CEMENTITIOUS BREATHABLE FINISHES An advancement in coatings technology is the use of urethane cementitious mortars, slurries and toppings to counteract the challenges associated with MVE, gassing and high relative humidity situations in concrete. Cementitious urethane is commonly referred to as urethane concrete or urethane mortar. In layman’s terms, it’s a type of floor coating or secondary containment lining; but it also is an excellent moisture vapor mitigation

technology. Cementitious urethane is a modified urethane with Portland cement, water, aggregate and other fine materials. The technology was originally designed and formulated for the food and beverage industry to handle the daily wash downs and thermal shock of the facilities due to the co-efficient of lineal thermal expansion (CLTE) being similar to that of poured in place concrete. Water-based urethane cementitious have many additional advantages to an owner and applicator in new construction and rehabilitation projects such as excellent chemical resistance, Zero VOC, ease of application and placement, the ability to hang formulations vertically and at varied thicknesses from 20 mils to 3/8” and rapid curing and recoat times. Cementitious urethanes are primarily waterbourne formulations allowing them to be breathable, IE; allowing moisture vapor to pass through from a substrate without allowing soluble salts or chlorides to collect at the bond line of the coating and substrate creating disbondment of the coatings. This mechanism is also greatly aided by the thickness of the coatings systems application, typically in excess of 1/8” or 125 mils, creating a reservoir within the urethane cement for vapor to dissipate and not create blisters within the coating film. The use urethane cement as an underlayment on the freshly poured structural concrete walls in the wet well allowed the rehabilitation contractor to address the new structures in approximately 4 days after they were poured or as soon as the concrete had achieved sufficient hardness to withstand mechanical abrasion. The new and existing concrete surfaces were then prepared to SSPC SP-13/NACE 6; CSP 4-6, then resurfaced accordingly. HYDROGEN SULFIDE RESISTANT LININGS The corrosion process of underground concrete infrastructure assets can occur for a variety of reasons including old age, freeze/thaw cycling, traffic loading and most significantly microbial induced corrosion (MIC). MIC is a 4 phase process that creates significant deterioration of the cement paste. STEP 1 - Sulfur reducing bacteria (SRB) break down sulfates in the waste stream and produce hydrogen sulfide (H2 S) and carbon dioxide CO2. STEP 2- The acidic gases H2S and CO2 act to reduce the pH of concrete from approximately 12 to as low as 9. Sulfur oxidizing bacteria (SOB) attach to the surface as sulfates are produced. STEP 3 - The SOB’s are known as Thiobacillus Thioxidans. They consume H2S and discharge sulfuric acid H2SO4 The pH continues to drop and microbial growth accelerates creating more H2SO4. STEP 4 - Acid attack of the concrete creates a layer of gypsum (calcium sulfate). As organisms reproduce additional acid is produced. Eventually this cycle causes structural failure. To protect concrete structures from the catastrophic effects of MIC, chemically resistant linings are installed in new construction and rehabilitation operations. Liners can be broken down into two classifications, freestanding and bonded. Bonded liners are comprised of technologies such as polyureas, hybrid polyurethanes and in this case, 100% solids epoxy formulations are used as barriers to protect assets from MIC. The choice of a technology to be used should be based on factors specific to the site being rehabilitated, the concentration of H2S gasses present, the amount of structural rehabilitation required for an asset as well as the amount of time an asset can be bypassed or out of service. 100% solids epoxies have some significant advantages when used as chemically resistant liners to protect from MIC. First, they contain little to no solvent and are VOC compliant in all regions of the United States. They offer the ability to be applied to surface saturated dry (SSD) substrates, meaning that the concrete does not have to be completely dry, it can be damp just not have water standing on the surface. 100% solids epoxies can be formulated to cure very quickly (in as little as 6 hours for sewer service) but have the ability to be applied with a variety of application methods including spray, trowel or brush and roll. Also, 100% solids epoxies can be applied in very high film builds (either as neat resins or with the introduction of aggregate filler) to resurface and fill minor imperfections in the substrate, aid in cleaning operations and improve maintenance inspections.

Most importantly 100% solids epoxies are formulated to be highly chemically resistant to H2S and other chemicals and gasses contained in municipal sewer systems. They are rigorously tested to ensure they will be acceptable for use in this extreme environment. Test panels are exposed to an aggressive environment that replicates conditions present in a wastewater treatment facility. One such test, ASTM G210 or Severe Wastewater Analyst Testing, is outlined as follows: “The test chamber consists of a glass vessel fitted with a polymeric lid and movable carousel. The test specimens are mounted on the carousel that is periodically lowered into the test solution to wet the specimens. The test specimens remain in the vapor space for the majority of the exposure. The test solution consists of 4% sodium chloride in a 10% sulfuric acid solution. The chamber is periodically purged with a simulated sewer gas composed of 500 ppm hydrogen sulfide, 10,000 ppm carbon dioxide, and 5,000 ppm methane in dry air. The apparatus is placed into a convection oven maintained at 65°C throughout the test.” The 100% solids epoxy chosen for the CMIC application passes ASTM G-210, can be applied as a neat resin up to 125 mils in a multiple spray pass application or can have aggregate added to the epoxy to allow for film builds up to 250 mils in a single application. The epoxy has a moderate pot life of 45 minutes at 77 degrees F, allowing a contractor the ability to apply by trowel, rolling, conventional airless spray or if they choose plural component spraying. This epoxy can be returned to wastewater service in 36 hours. OUTCOME Meeting or exceeding the specifications for the materials used was of utmost importance. For the project, the wetwell specifications were the most important to maintain. Within the contract two vendors were specified with traditional 100% Solids Epoxy and Epoxy resurfacers that would have required extended curing time of the concrete prior to application of the non-permeable linings to the new concrete center wall. The contractor on the project submitted the urethane cementitious moisture mitigation system and 100% solids epoxy as an overall cost and time saving measure, and this was approved as an equal for this project. Traditional micro silica mortars were used to resurface all existing spalled and deteriorated areas prior to the 100% solids epoxy application. The areas of the structure where rebar was exposed saw it abrasively blasted to an SSPC SP-10 near white metal, and received two coats of a glass flake filled epoxy @ 8-10 mils DFT per coat. Upon successful completion of installation, a 5 year material warranty was provided by the manufacturer to the owner to support the use of alternative technology to solve the timing issues on this project. CMIC PS1 emergency repairs were accepted by the owner and operator in mid-October 2016, about two weeks before the anticipated completion date. Without the use of the new technologies detailed in this paper, the construction timeline would have exceeded the projected timeline, extending the need for bypass pumping and exceeding the budget. The hydrogen sulfide levels at CMIC PS1 continue to be high, and in 2017 a hydrogen sulfide meter was installed to gather data. This data will be used in the near future to make recommendations for additional work to the pump station, such as installing blowers to remove the gasses. Despite the high levels of noxious gasses, the one-year post-construction inspection in late 2017 showed that the repairs are functioning properly and for their intended purpose. The owner and operator of this pump station are both pleased with the work done and the performance of the materials used to complete this emergency rehabilitation to a major wastewater pump station in the MCWA system.