Molding a Better Manhole

Composite Access Products provides lightweight, corrosion-free access covers.

Molding a Better Manhole

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Manhole rehabilitation has improved significantly over the past couple decades, and composites are playing a big role.

Chad Nunnery started his career in composites manufacturing after graduating with engineering and chemistry degrees from Dartmouth College in 1994. He set up and managed composite businesses in Latin American countries where he first witnessed nonmetallic manhole covers being used primarily for theft prevention. After analyzing other material benefits, he realized that composites would solve additional problems like inflow, SSOs, corrosion, weight, data transmission, asset management, install efficiency and environmental impact.

Municipal Sewer & Water recently spoke with Nunnery about the role that composite manhole covers and accessories play in improving performance and access.

MSW: Tell us a little about the history of Composite Access Products and how it got started.

Nunnery: Prior to CAP, I formulated, manufactured and sold composite fiberglass materials for Bulk Molding Compounds Inc. The company’s mission was to improve end products by converting metals and other materials into a molded thermosetting composite. Rather than fighting with competitors over existing market share, the BMCI team focused on increasing the overall market size with new applications. BMCI’s main customers molded automotive headlamps, valve covers, circuit breakers and a variety of other applications. After analysis and research regarding the material property requirements, it became clear that molded manhole covers produced using this fiberglass composite would address many problems associated with traditional materials.

In 2015, my two co-founders and I formed Composite Access Products in McAllen, Texas, to mold composite manhole cover assemblies. CAP is the first U.S. compression molder of traffic-rated composite manhole covers. In 2020, CAP won the Award for Composites Excellence from the American Composites Manufacturers Association. In 2021, Fulton County, Georgia, acknowledged CAP as “key” to eliminating sewer spills into the Chattahoochee, after suffering millions of gallons of pollution for 30-plus years.

MSW: Why are manholes such a universally important topic for municipal utilities?

Nunnery: Utility access holes are not sexy. But we rely on these access points to maintain our wastewater collections, drainage, water and other utility distribution. While society passes over these manholes without a second thought, increased floodwaters leak into our wastewater systems, exceeding collections system capacities. The resulting flow reversal, called a sanitary sewer overflow, is a leading cause of pollution into our natural waters. Some calculate that sewer spillovers contribute over 32 trillion gallons per year of pollution into rivers, lakes and oceans. So manholes — necessary for utilities — can have a major environmental impact affecting our health, water activities, aquatic life and possibly our drinking sources.

MSW: What’s the most common problem you see your municipal customers are facing?

Nunnery: In addition to stormwater inflow, corrosion-prone infrastructure materials like concrete and iron plague our municipalities. Corrosion occurs from obvious culprits such as water and saltwater, but even more destructive is a bacterial conversion of sewer gases (specifically hydrogen sulfide) into sulfuric acid. The bacteria called Thiobacillus 

creates an acid that degrades most materials, while polymers generally resist acidic corrosion. Interestingly, some researchers say that an iron molecule that exists in U.S. concretes, and of course iron manhole covers, is in fact necessary for these bacteria to consume and produce the acid. So, while a polymer solution is acid resistant, it also doesn’t provide the “food” necessary to create the acid in the first place.

MSW: How has your product line evolved to better meet the needs of customers with aging infrastructure and limited budgets?

Nunnery: CAP pays close attention to customer feedback. Since our first molded covers, we have improved our fastening systems, pick-hole openings and custom logos, added attachment points, and expanded our size offerings. In addition, we added — as a standard feature — an encapsulated magnet to detect hidden covers. Some contractors will overlay manhole covers or even bury covers. To later locate concealed covers, utility operators use metal detectors. Composite materials and stainless steel accessories do not alert metal detectors, creating a challenge for composite cover suppliers. CAP’s proprietary (patent-pending) solution encapsulates strong natural magnets in the raw compound during the molding process. The magnets amplify signals to metal detection devices alerting the user as far as 6 feet away and several feet underground. Our customers are very satisfied with this feature.

MSW: What does the full suite of CAP products provide for municipal utilities? 

Nunnery: CAP’s composite manhole covers offer a traffic-rated, watertight, corrosion resistant access cover that is half the weight of traditional options. The product properties will help eliminate sewer spillovers — remember, a leading cause of water pollution. Cover corrosion creates unsafe conditions for both pedestrians and utility operators, so CAP products provide a safer solution. Our covers look great with attractive logos, colors and stone-like appearances. As a bonus, they’re transparent to transmission signals for the use of smart city technologies without the necessity of drilling antennae holes commonly seen with signal-blocking metals.

MSW: Is your product line aimed more at infrastructure rehabilitation or new construction?

Nunnery: Both. Municipalities specify CAP for new construction and want to use polymer solutions to replace older decaying systems. For decades, cured-in-place piping has been utilized for pipes. More recently filament-wound and other polymer manhole columns were introduced. Polyethylene, expanded polypropylene and rubber solutions have been specified for use in the chimney sections of manholes. Finally, municipalities can make a completely corrosion resistant, watertight polymer system with CAP frames and covers. We like to say, “From pipe to CAP,” meaning, why invest extra dollars for premium polymer utility access materials just to place metal assemblies that can corrode on top? It just doesn’t make sense. So, “Just CAP That” became our slogan.

MSW: What differentiates your manhole covers and accessories from other composite options?

Nunnery: CAP offers many unique options. The encapsulated magnet described earlier is one example. CAP can make vented covers while maintaining traffic-rated strengths — not seen from our competitors. CAP provides gasketing for perfectly watertight covers — no leaks while submerged in at least 20 inches of water. CAP’s logos and artwork “pop” with pronounced depth and intricate detail. While CAPs are much lighter than iron, CAP is the heaviest of the composite options, which gives users more confidence for street use. CAP molds all features — bolt holes, pick channels, etc. — while many competitors machine or drill these features post-molding. This is not preferred for composites. All CAPs are molded with attachment points to facilitate fastening technology onto the cover. CAP’s lead times are two weeks from raw material to final product while others require months. Finally, CAP is one of only two made-in-the-USA composite options for the water/wastewater markets.

MSW: Could the average municipal utility install CAP products with an in-house crew?

Nunnery: Yes. There are not many installation differences for CAPs versus traditional covers. However, we emphasize a couple important details. If using CAP’s watertight stainless steel bolted solution, installers should hand-tighten the bolts and not use impact wrenches to avoid stripping the corrosion-resistant, but softer stainless steel hardware. Also, users should avoid inserting shims, rocks or other objects under the frames to slant the cover to achieve a desired grade. Riser ring manufacturers produce angled surfaces that create the appropriate grade without a point-force from a shim. Point loads can result in hazardous conditions.

MSW: Do you sell direct to contractors and utilities or go through distributors?

Nunnery: We partner with factory representative firms and distributors that provide CAP a broader geographic availability. Without these firms, CAP would likely not be able to sell to all 50 states. In the five years since we started molding product in Texas, we are installed in over 400 cities and 46 states.

MSW: What’s coming up for CAP in 2022 and what can customers expect out of you in the future?

Nunnery: We are excited to introduce three new products: 1) A cover for air release valves, 2) a 36-inch clear opening assembly and 3) our “CAP ALERT.” This third product is a cover and frame with a preassembled sensor and transmitter that fits inside the CAP’s ribbed geometry. Today’s devices hang below the cover bottom surface leaving them to be potentially damaged when opening and closing the cover. The CAP ALERT protects this expensive technology while also eliminating field assembly and antennae hole drilling. In addition, this CAP product will be more affordable than most current options in the market.

MSW: What else would you like people to know about Composite Access Products?

Nunnery: In addition to the many benefits listed, we believe that the CAP manufacturing process is more sustainable (relative to cast iron) with less environmental impact. As a quick example, CAPs are molded at about 275 degrees while iron is casted at 2,700 degrees. Many iron foundries use coke, a high-carbon-content form of coal, for the energy to power the casting process. While the fiberglass upstream in the composite supply chain is also formed at high temperatures, this raw material represents only 40% to 60% of the final composite product. One hundred percent of the iron material is cast at extreme temperatures. Furthermore, fiberglass typically uses natural gas rather than coke to energize the ovens. 


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