High & Dry

About 18 miles north of Denver and just 10 miles east of Boulder, with a panoramic view of the Rocky Mountains, the City of Lafayette, Colo., has just completed the new 75 th Street Diversion and Pipeline. The new system is designed to provide relief from the region’s worst drought in several hundred years.

This vibrant community of slightly more than 23,000 was founded in 1888 in an agricultural area. However, it soon became a coal mining community where the first shaft was sunk in 1887, tapping into the veins of coal that ran throughout the area.

As natural gas slowly replaced the use of coal for fuel, the mines began cutting production and finally closed, the last Lafayette mine shutting down in 1956. Through this period, agriculture again became the dominant economic activity in the Lafayette area. Rapid growth in Denver and Boulder brought Lafayette substantial residential growth, and as the town grew, the farming-based economy shifted again to welcome commercial enterprises, small industrial, and manufacturing concerns. But lack of sufficient precipitation had major negative effects, especially for farmers.

High & Dry
In 2002, the 75 th Street project was conceived. Designed by McLaughlin Water Engineers, a subsidiary of ASCG Company of Denver (www.ascg.com), the pipeline was installed to help offset serious drought conditions in the area. Stream flows in Colorado were the lowest they had been in the nearly 100 years for which records have been kept, and analysis of tree ring data suggested it could be the worst in 300 to 500 years. The recent drought had been so bad that the city adopted strict ordnances to preserve water supply. To bring additional relief, the governor quickly acted to sign several bills aimed at assisting Coloradoans with water supply issues. Many cities contacted the State Engineer’s Office regarding approval of a substitute water plan. Lafayette was one of those cities.

Today, the city enjoys the benefits of HOBAS (www.hobaspipeusa.com) centrifugally cast, fiberglass-reinforced, polymer-mortar (CCFRPM) pipe. The pipe was installed on a tight scheduled in an environmentally sensitive wetland area.

The pipeline originates at Boulder Creek and can bring 16 million gallons per day of raw water through the 36-inch diameter line to Lafayette. Approximately 1,800 acre-feet of this new water supply is being used to supplement current supply.

"This project allowed a reliable source of high-quality water," says Aaron Asquith, formerly with McLaughlin Water Engineers and now a principal with McLaughlin Rincon Ltd. (www.mr-ltd.com) of Denver.

Environmentally Friendly
The 24,000-foot pipeline is mainly in an area dedicated to open space and mountain parks that crosses through other municipalities. Negotiations and permitting with the city and county of Boulder mandated that construction be environmentally sensitive.

As such, designers needed to ensure there would be no long-term adverse effect on surrounding wetlands. "It wasn’t as if we had an allowable leakage clause, we were allowed zero leakage and we needed a pipe that could accommodate those criteria," says Brad Dallam, P.E. with the City of Lafayette.

In addition, there were 10 known prairie dog colonies and several bald eagle nests located along the project area, both with mitigation and protection clauses. To complicate matters further, part of the line is located within the railroad right-of-way, requiring additional permitting. And there was a history of very hot soils in the area, making metallic piping options undesirable.

The tight tolerances of the joint systems, the history of leak-free installations, and long life expectancy led to the exclusive specification of CCFRPM pipe. "We wanted a pipeline that would last for an extended period of time. HOBAS has a good track record for maintenance and durability, and the pipe had a very smooth interior that allowed for easy transport of sediments and small rocks in the diverted raw water," says Asquith.

Rapid Installation
The project was put on fast track to minimize the impact in the sensitive areas and relieve the stress on the water system caused by the drought conditions. Final engineering design began in March 2002 and the job was bid in multiple contracts in August of the same year. The permitting allowed only 4.5 months for construction during the winter; yet work was essentially complete by February 2003. This was quite amazing considering the project included more than 4.5 miles of pipe, intake, and outfall structures and metering valves and was installed through a creek bed, wetlands, and across the treacherous countryside.

Nonetheless, the contractors that installed the majority of the piping project, AISA Civil Inc. of Broomfield, Colo., and B.T. Construction Inc. of Commerce City, Colo., were able to meet the deadlines. In addition to expediting the design phase, HOBAS met the tight delivery schedule. "We had a guarantee from HOBAS that the pipe could be delivered on time," says Dallam. "We even increased the footage we needed during construction by a few thousand feet and received that pipe within the original schedule. We had eight crews working on the project at once. Pipe was being installed at an incredible rate." HOBAS customer service stayed in touch with the contractors to ensure that pipe was supplied on time.

The ease of assembly of the push-together FWC joints and the lightweight CCFRPM pipe sections helped meet the tight deadline. "The installation was pretty easy," says Eric Koinzan, project manager with AISA.

Satisfaction Guaranteed
Although CCFRPM had been used in this area in sliplining and aboveground installations, little had been installed by direct-bury, which was the method used in most of the Lafayette project. So the design engineers had very limited applicable experience. The two contractors also were first-time users. But the installation went smoothly, and by the end of the project all involved cited HOBAS as a highly responsive pipe supplier that provided assistance before, during, and after installation. "The engineers at HOBAS provided past cases and design calculations that significantly eased our meeting the permit requirements from the Union Pacific Railroad and allowed us to minimize our impact in the sensitive habitat," says Asquith.

The CCFRPM pipe offers an added benefit because structural damage can be repaired in place. During the installation, two localized areas were damaged which is not uncommon on a project of this magnitude.

"HOBAS field service was dispatched to provide assistance and guidance for the onsite repairs," says Greg Chol, senior resident engineer of McLaughlin Water Engineers. "The high level of field support helped in achieving the leak-free service for the entire line — even the repaired sections."

The native soils on the projects ranged from very loose granular to very dense cemented sandstone, which ranged from six to 50 blows/foot. The chosen embedment material was ¾" minus crushed rock with a required density of 95 percent Proctor. Even though the cover depth was rather shallow, ranging from three to 12 feet, a 72-PSI stiffness pipe was specified to provide additional safety.

Luckily, the melting 2002-2003 winter snow pack helped maintain the water supply. The city was graced with water from two sources — Mother Nature and a little human intervention.

For More Information: www.hobaspipeusa.com

A version of this article appeared in the December 2004 issue of Water & Wastes Digest.