Fifty miles northwest of the St. Louis metropolitan area sits an emerging residential and commercial community known as Bowling Green, Missouri — home to 5,300 residents. It’s also home to the Northeast Correctional Center, a minimum-medium custody prison that opened in 1998.

The facility houses 2,106 male inmates, runs a 24-bed substance abuse treatment program, and also provides substance abuse assessment services.

A few years after occupancy of the prison, the facility began to experience corrosion failure in both the heating and domestic hot water underground distribution systems. These systems consisted of more than 20,000 lineal feet of buried pipe to supply hot water for heating and for domestic use to the entire facility. The problems persisted and by 2013, the existing systems were in very poor condition and necessitated replacement.

In January 2014, Klingner & Associates P.C. was selected by the State of Missouri’s Office of Administration – Division of Facilities Management Design and Construction to provide professional engineering services for the Underground Piping Study and Heating Loop Replacement project. The firm was selected through a qualifications-based process and served as the prime consultant for the project. It oversaw all professional services required including mechanical, structural, and civil engineering, surveying, and construction observation.

The problem

The existing heating hot water loop at the facility consisted of schedule 40 black steel pipe. And the existing domestic hot water loop consisted of copper pipe. All the pipes were buried in a single trench with poured-in-place granular insulation. The pipes were attached to steel and concrete anchors/guides at regular intervals. Significant corrosion pipe failure had occurred within both systems with the heating system exhibiting failure prior to the domestic hot water system issues.

According to the Department of Corrections (DOC) staff, the failure appeared to be the result of corrosion on the exterior of the pipe and not from the fluid within the pipe.

The corrosion failures started with small diameter pipes serving individual housing units, but failures of larger diameter mains followed. Eventually, multiple failures were occurring in the main piping system on a regular basis, causing interruption to the heating and/or domestic hot water supply of multiple housing units.

The DOC staff had to replace various sections of the pipe. Although the heating plant was located outside the security perimeter, the majority of the piping was located in the secured area, complicating access for replacement. The presence of buried high-voltage electrical distribution adjacent to the piping trench further complicated things.

The degradation of the piping system combined with the frequency of the failures, however, made each subsequent repair to the system more difficult. The condition of the piping system had reached critical status and threatened to shut down the entire facility, which would require the relocation of thousands of inmates.

Klingner & Associates P.C. had to design a replacement piping system that would be resistant to corrosion, could be installed without disturbing the existing piping system, constructed within the allowable budget, and installed as soon as possible.

All of these goals had to be accomplished with minimal disruption to the operation of a fully occupied correctional facility.

Innovative solution

The goals were complex and required an innovative project approach. In the initial phase of the project, Klingner & Associates P.C. studied multiple pipe and insulation material alternatives as well as installation methods.

In the past, the DOC staff discovered that the only materials that were able to withstand the corrosive site conditions were stainless steel and PEX tubing. Although PEX tubing held up under the site conditions, it would not be considered for this project because it was not available in the larger pipe sizes needed for a complete system.

Instead, Klingner & Associates P.C. reviewed carbon steel, stainless steel, copper, polypropylene, chlorinated polyvinyl chloride, and fiberglass reinforced plastic (FRP) pipe materials, along with various field and shop applied insulation options. Conceptual designs were developed for aboveground and buried pipe installations, along with cost estimates for each method. The various pipe and insulation combinations were then analyzed using both belowground and aboveground installation methods, and the results were summarized within a report. There was a lot of time and effort spent analyzing all the solutions. The firm’s due-diligence gave the owner the information needed to make what was a slightly controversial choice.

Ultimately, Klingner & Associates P.C. determined that fiberglass pipe, pre-insulated with closed cell polyurethane and a high-density polyethylene jacket installed belowground was the best option to fulfill the project goals of corrosion resistance, ease and speed of installation, and project budget.

“Fiberglass pipe was chosen because of its corrosion resistance, material availability, ease of assembly, cost, and owner’s familiarity with the piping material,” says John Neyens, P.E. mechanical engineer at Klingner & Associates P.C. “The closed cell polyurethane pre-insulation system was chosen over a field applied system to reduce the amount of labor that had to be completed within the secured perimeter of the facility. The density and compressive strength of the insulation were desirable to help protect the fiberglass pipe from impact damage during construction.”

FRP pipe is not a new technology, but it’s not commonly used for the distribution of domestic and heating hot water. Metallic piping systems such as carbon steel or copper are more common materials for these types of piping systems. However, the catastrophic corrosion failures exhibited by the existing copper and steel piping systems made these materials undesirable as replacement options.

Though FRP piping is resistant to corrosion, Klingner & Associates P.C.  had to take into account design considerations, such as pressure and temperature limits of the pipe, thermal expansion, thrust restraint, and pipe bedding.

A fully restrained pipe design in both the axial and longitudinal directions of the pipe was used to reduce stress on pipe joints from thermal expansion. This method of pipe design is not practical with metallic pipe and represents an innovative approach to typical design. To assist the installing contractor in understanding the unique aspects of FRP pipe and its differences from the more commonly installed metallic pipe, contractors were required to take training sessions to be certified in FRP pipe installation.

“All pipe bonders had to participate in a training class and fabricate a pipe-to-pipe and pipe-to-fitting joint passing the testing requirements of ASME B31.3,” Neyens says.

The pre-insulated piping system also served as an innovative solution to several critical challenges with the overall project. Not only does the pre-insulated system prevent excessive heat loss from the pipe, the density of the insulation and jacket helps protect the FRP pipe from damage. By installing the insulation in a controlled factory environment, better quality control is achieved. Additionally, because the insulation was pre-installed offsite, it reduced the amount of work that had to be completed within the limits of the correctional facility, which reduced the overall construction period length.

The process

Construction in an occupied correctional facility environment poses several challenges. Even simple tasks, such as visiting the project site and observing current conditions, were complex due to the security requirements associated with a prison. Security requirements combined with the technical requirements made for some very interesting obstacles.

The design team put careful attention into reviewing each of the design requirements with the owner’s stakeholders including administration, project management, maintenance, and security personnel. And then all decisions were reviewed and modified based on the consensus opinion of everyone involved.

Even with all these measures, challenges still arose.

One of the most significant challenges to the installation of the piping system was the requirement to keep the existing system in operation during the entire construction period. The logical pipe route for the new piping was already occupied by the existing piping, which had to stay in place during the construction period. With more than 20,000 lineal feet of pipe to be installed and thousands of potential routing conflicts, finding a route for the proposed piping was a significant challenge.

To overcome this issue, as-built documentation of the project site was cross referenced against new field survey data and located both horizontally and vertically on plan sheets. During the construction period, Klingner & Associates P.C. provided full-time construction observation to assist in the resolution of conflicts discovered following excavation of the proposed pipe route.

The construction observer came across challenges as well. They needed to be careful to follow all facility security requirements including restrictions on pictures for all construction progress images. But at the end of the day, having an observer onsite during the construction process allowed them to address any challenge at hand.

Another project challenge involved the mechanical engineering phase. “The physical properties of fiberglass pipe are very different from steel pipe,” Neyens says. “Maybe the most notable difference is the coefficient of thermal expansion, which is roughly twice that of steel.” However, the buried piping system was inherently restrained, and the system was successfully designed without thermal expansion loops. It was necessary to pay attention to the valve vaults and directional bore casing pipe to correctly apply pipe guides, anchors, and supports specifically designed for a fully anchored fiberglass piping system.

As for the structural engineering phase, the facility owner did not want to disrupt the integrity of the security perimeter during construction or during future repair and maintenance activities. The security perimeter consists of multiple rows of fencing, including an electrified fence in the middle. The solution was a casing pipe, directionally bored under the entire security perimeter, with concrete receiving vaults installed on either end. “This allowed the piping to be installed without disruption to the perimeter fence,” Neyens says. Future maintenance including complete replacement of the pipe material can occur using the same methods as the original installation without disruption of the perimeter fence.

Throughout the entire project cycle, Klingner & Associates P.C. and the owner had frequent communication regarding the project. The owner was able to review and comment on the design process at multiple stages including the preliminary design report, final design report, schematic design, design development and construction document development. Frequent communication between the owner and the engineer allowed for a final design that functioned from both a technical and practical standpoint.

The result

This project had many separate but interrelated goals that had to be accomplished for successful completion.

Construction cost estimation for a project consisting of underground pipe installation within a difficult working environment is challenging to say the least. However, this project was completed for almost the exact same amount estimated by Klingner & Associates P.C. during the initial preliminary report phase. The firm had developed 10 different cost estimates for projects consisting of various pipe types and installation methods. The estimated cost of the buried FRP pipe approach that was ultimately used for the project was $4,079,350. The final constructed project cost including all change orders was $4,059,371.59, a difference of less than 0.5 percent between the original budget estimate and the final construction cost.

It is also worth noting that the total value of change orders associated with the project was less than 2.8 percent of the original construction contract sum. This is remarkable considering that almost all of the work was installed below grade in 5,000 lineal feet of trench routed through an existing correctional facility campus.

The engineering design for the project was completed on an expedited schedule and given to the owner ahead of the contractually required deadline. This allowed the owner to complete the bidding process for the project sooner and ultimately allowed for the project to be completed just ahead of the 2015/2016 heating season, which represented the completion goal of the owner.

The new piping system performed exceptionally well in its inaugural heating season with only two warranty repairs required in its first 12 months of operation. One warranty repair simply required tightening of flange bolts and the second was a result of a leak in a copper fitting where the new FRP pipe system connected to existing interior piping. The FRP pipe system has performed incredibly well and greatly reduced operational and maintenance costs for the owner. The owner no longer has to allocate resources to repair leaking pipe, and water losses associated with leaking pipes have been eliminated.

Ultimately, the use of non-traditional pipe material led to meeting the goals of the project. Engineers can be reluctant to transition from traditional practices without concrete evidence that a new methodology has proven performance. The use of FRP pipe for the domestic and heating hot water distribution system at the Northeast Correctional Center has now been proven by successful operation during its first year and can serve as a template for other engineers when traditional pipe materials are not a good fit.