Vadnais Corporation

Reprinted from Trenchless Technology
March 1996
© 1996 Paul J. Miller

In the last six months, two unique and difficult microtunneling projects have been undertaken in Southern California. One is complete and the second is ready for its final drive by a contractor who is developing a niche within a niche - a special project microtunneler.

Paul J. Vadnais, president of Vadnais Corporation of San Diego, said that their interest lies in pursuing the unusual microtunneling projects. These recent projects certainly fall within that category.

Vadnais Corporation is preparing for the third and final drive at the Santa Ynez River for the Central Coast Water Authority (CCWA) microtunnel project near Buellton, California, about 150 miles north of Los Angeles. In October, Vadnais completed a microtunnel in his hometown of San Diego to install a casing for a gas line crossing under a freeway. Though others have been attempted, the full-face bore in high strength rock is believed to be the first successful crossing completed by microtunneler in North America.

Concrete caisson shafts,
constructed with pull-forms,
are the solution for
microtunneling in the
high groundwater conditions.

Not a novice in microtunneling, Vadnais had undertaken two prior projects with microtunneling. A job at Mission Viejo, Calif. installed clay pipe in three drives, totaling about 1200 ft. A second job in Contra Costa County, near San Francisco, installed 400 ft of 36-in. casing for a sewer line project.

Microtunneler System

West2.jpg (25345 bytes)

The R~S 6OOAS is
outfitted with eight
carbide-inset roller
cutters.

Vadnais selected a Soltau Microtunneling system for the two recent projects. The microtunneler was an RVS 600A5 unit, which can handle up to 72-in. diameter bores, with slurry ground control and a slurry muck removal system. Due to boulders and hard rock, it was equipped with a hydraulically driven cutting head fitted with eight 14- and 19- inch carbide-insert roller cutters designed for rock hardness to 35,000 psi and a built-in rock crusher. An 800-ton jacking frame could handle either 10 or 20-ft joints of casing pipe.

This was the most powerful machine for this diameter manufactured to date by Soltau. The manufacturer has responded to unusual, difficult projects with custom-designed systems, as demonstrated also in the microtunneler supplied for the Kona, Hawaii project selected in October 1995 for the new construction Trenchless Technology Project-of-the-Year.

The microtunneler system had been specified for the CCWA project when Vadnais was presented with the opportunity to do the hard rock microtunneling in San Diego. After consulting with Paul Nicholas, president of Soltau Microtunneling, they determined that the Soltau unit could handle the rock boring challenge.

At the end of the 240-ft drive, the cutters were judged to be in fine shape to continue on the CCWA project, according to N. Paul Vadnais. At the time of this site visit, the microtunneler had completed nearly another 1000 ft. and was being readied for the final drive. Though the head showed signs of wear, only the three gauge cutters are being replaced for the final 820-ft drive.

Coastal Aqueduct

The CCWA project is part of a 145 mile pipeline to supply supplemental treated water to cities and communities in the Central Coast region of Santa Barbara and San Luis Obispo Counties. The Coastal Aqueduct is part of the massive State Water Project and receives water from the California Aqueduct, which is fed by water from the Sierra Nevada Mountains of Northern California.

The two microtunnel pipeline crossings on the Santa Ynez extension lie within environmentally sensitive areas. The first at San Antonio Creek, on the Vandenburg Air Force Base, is the habitat of an endangered species of fish - the unarmored three-spine stickleback. The U.S. Fish & Wildlife Service prohibited trenching of the pipeline through the creek area. The second crossing at the Santa Ynez River lies in a fragile flood plain, overgrown with willow bushes (a protected native plant), which are home to the Southwestern Willow Flycatcher, a bird also on the protected species list.

Montgomery Watson was retained as the design firm for the project. After a thorough review of alternatives, including directional drilling, Montgomery Watson recommended a microtunnel design to place the pipeline without disturbing the habitat. The board of directors of the water authority weighed the options and approved the design alternative. Dan Masnada is the executive director of Central Coast Water Authority.

Selected as construction manager is the engineering firm of CH2M Hill, operating out of local offices in Buellton. Dave Baum is the project engineer while Jim Henderson is the site inspector for CH2M Hill. Thomas J. Fischetti is CCWA's project engineer.

The initial project design was advertised for bids in 1994 and the project was let to an established contractor with microtunneling experience. Based on the soils reports prepared by Fugro West,Inc., a Santa Barbara geotechnical consultant, the contractor began pit construction at the river site. The firm planned to build a launch pit with driven H-beams and shoring in conjunction with site dewatering.

A series of wells were installed and groundwater was encountered about 16 ft below the surface as Fugro had documented. What was not expected was the strength of the underground water table. According to project personnel, the ground water moves in a distinct current following the flow of the river.

The design called for the line to be installed at an invert of approximately 34 ft below surface. Pit excavation had begun, with excavation about 10 ft deep. However, the wells were no match for the flowing groundwater. The contractor concluded that the conditions seriously compromised the feasibility of completing the project and the CCWA terminated the contract.

In the meantime, winter rains of early1995 had swollen the Santa Ynez River and the area was inundated with massive flooding. After witnessing the force of the swollen river, the consultants and the authority became concerned for the security of the proposed pipeline under the river.

Wisened by the flood, they concluded that the line should go 10 ft deeper than originally planned. After redesign, the project was advertised again in spring1995. The Vadnais Corp. was awarded the project on a bid of $4,565,000. Notice to proceed was issued in June.

Caissons

Vadnais proposed to build its pits at the Santa Ynez River as concrete caissons, believing that the deep structures could be sealed adequately to hold out ground-water. The drives were divided into almost equal lengths 815 ft to the east, away from the river, and 820 ft to the west under the river. Vadnais designed a center launch shaft with a 28-ft diameter and a depth of 54 ft. The receiving pits were built at half the diameter, with one at a depth of 62 ft and the other at 77 ft.

The caissons were cast-in-place, using Efco Radius Forms which allowed for 20-ft lifts. Vadnais designed a cutting shoe and installed a water stop just above the shoe to aid in keeping the pit dry. The 33-in. caisson walls were reinforced with a double lattice of rebar. Lubrication lines were placed around the forms to inject bentonite to the bottom of the shoe.

Vadnais launches the east drive
on the Santa Ynez project.
The microtunneler cut through
the caisson wall to start the drive.

Concrete was poured and the excavation process began. A clam-shell bucket on a crane dug out the center, and the caisson settled into place. Just like their predecessor, Vadnais hit high groundwater which ultimately filled the shaft while they were sinking the caisson.

The process continued uneventfully for the first two lifts. On the third round,Vadnais hit a layer of hard material, a Rincon claystone, which resisted any efforts to remove by clam-shell. An attempt to use a 24-in. track-mounted auger drill also went nowhere, and the drill finally broke. A team of divers was called in to assist with various techniques from breaker hammers to high pressure waterjets, all to no avail. It finally required several rounds of underwater blasting by explosive experts to break the barrier. A 6-ft thick concrete floor, heavily reinforced with rebar, was poured through the water.After the shaft was pumped dry, a finish floor was poured to wrap up the shaft.

The 28-ft ID launch shaft required 540 cubic yards of concrete for the ring construction. Another 180 cubic yds. were poured for the floor, for a total of 720 cubic yds. of concrete for the launch shaft. The two receiving shafts were of similar construction.

Microtunnel Drives

Ground conditions at the San Antonio Creek site did not require the elaborate caisson shafts. Groundwater was not a problem, and driven sheet piling was adequate to build rectangular pits.

The San Antonio Creek microtunnel drive was completed in silty sand without incident. The 170 ft. tunnel was bored in three days. As with the entire CCWA project, 60-in. Permalok steel casing with press-fit joints was installed. The 36-in. carrier pipe was inserted along with three 4-in. PVC conduits for fiberoptic cables, and the crossing was tied into the pipeline.

At the Santa Ynez River site, the eastward drive was completed by late January. The microtunneling pushes averaged 1/2 hr. per 20-ft joint. The best day was about100 ft in a 10 hr.shift, according to project superintendent N. Paul Vadnais. In general, the soil conditions consisted of a mixed face of the Rincon clay stone and river cobble and silty sand, with occasional boulders.

West5.jpg (24075 bytes)

Vadnais installs the 36-in.
mortar-lined carrier pipe
in 60-in. casing.

N. Paul reported one instance of tremendous pressure build-up, in which the jacking forces increased by 50 per-cent and continued at that level for 60 ft before finally returning to normal for the balance of the drive. He believes they must have hit a large boulder in excess of the machine's diameter which eventually broke up and the jacking loads dropped dramatically.

Though split face conditions are notoriously difficult in which to maintain line and grade, the microtunneler operators succeeded in delivering the crossing within acceptable tolerances. In fact, the machine cut right on target through a prepared entrance ring in the caisson wall of the reception shaft. The machine was launched in a similar manner, with the head cutting directly through the shaft wall.

As the prime contractor for the CCWAproject, Vadnais also installed the carrier line in the casing. A 36-in. mortar-lined steel pipe in 20 ft lengths, supplied by California Steel Pressure Pipe Co., Riverside, Calif., was inserted. Vadnais devised a method of installing the pipe by the use of "snatch blocks" attached to the casing at the tunnel opening. Cable was passed behind the pipe and then was pulled by a crane line to slide the new welded pressure line into place.

The three conduits were then installed and the line was ready for grouting. Sub-contractor Cell-Crete Corp., Los Angeles (an affiliate of Flastizell Corporation), pumped a 500-psi concrete grout slurry into the annulus.

The west drive is expected to begin in mid-February. Vadnais expects that this drive under the river will be in cobble and gravel, though he believes the probability of boulders is greater in the deeper line.

Thereafter, Vadnais will extend the lines in open trench to tie into the already laid pipeline. Water service through the line is expected to begin by year's end.

Hard Rock

On the San Diego project, Vadnais was the microtunneler subcontractor to Hood Corporation, also of San Diego. Hood was to install a small section of a 30-in.gas main for San Diego Gas & Electric beneath a freeway under construction. Vadnais was to install a 60-in. steel casing, but all other work was done by Hood. Vadnais inserted this project into the middle of the CCWA schedule while the caissons were under construction.

The tunnel site posed its own challenges. The bore was in solid rock with plenty of groundwater on top of the rock. Not only did the tunnel cross under the freeway, it also ran under a box culvert under the street which required the bore to be at a depth of 38 ft.

The full-face rock setting presented an exciting challenge for Vadnais and Soltau Microtunneling. Rock strength tests performed on bore hole samples, as well as rock from the face, showed unconfined rock strength ranging between 15,000 and 27,000 psi. Composed of volcanic deposits known as andesite, the rock was determined to be highly elastic, complicated the cutting action.

According to N. Paul Vadnais, the geological formation lent itself to variable rock conditions. "We knew it was harder in the middle just because of the way the ground was kind of rolled in this particular area."

The project was notable because it is the longest successful hard rock project completed by microtunneling in North America, according to Soltau's Nicholas. While others have been completed in rock, none have been in full-face formations of this strength and length on this continent.

The head design was suited for long bearing and cutter life, though with conservative cutting action and, therefore, lower production rates. With a few adjustments to the cutting head, the microtunneler was ready to be deployed on the job which tested its mettle.

Vadnais reported that the tunneling progressed well. "The drives went beautifully," said N. Paul Vadnais. 'The cutting action was slower, but very consistent. You could almost set your watch by the microtunneler's progression." The cutters turned the rock into what appeared to be decomposed granite.

Upon completion of the San Diego project, the cutters were inspected for wear. All were in excellent condition and the head was ready for the CCWA project.

Vadnais

Full-face rock in San Diego
proves the mettle of the
microtunneler.

Vadnais Corporation is the successor to a construction operation begun by Edmond J. Vadnais in 1959. Edmond is the father of Paul J. who is now the president of Vadnais Corporation. Paul J. established his company and began contracting by joint venturing with Edmond's company. When his father retired a few years ago, Paul combined their operations under his company.

Keeping track of the Vadnais family is a little more complicated due to duplicate names. Paul J.'s uncle works as a project superintendent, as he has since joining his brother Edmond when he began contracting. The difficulty is that the uncle is also named Paul, though with an initial N. On the job, crew members keep it all sorted out by simply referring to "uncle" for N. Paul Vadnais.

Edmond J. Vadnais Corporation started primarily as an underground pipeline contractor, installing sewer lines and storm drains. That led to similar utility work with water lines. Uncle Paul recalled that they did occasional concrete work, but that really grew under his nephew's direction and now the company builds box culverts, channels, pump stations and similar structures.

It was the Vadnais reputation for concrete work, along with its growing expertise as a microtunneling subcontractor, that opened the doors to the CCWA project. The failed first attempt demonstrated that watertight shafts were needed,which Vadnais could deliver with confidence. The support of Soltau Microtunneling offered the system and technology to complete the bores.

Paul J. Vadnais commented on the prospects for continued microtunnel contracting. He explained that they like to concentrate on difficult applications, such as both of these projects. "Though the risks are greater, the rewards make it worthwhile. We see it as almost a niche within a niche," said Paul. He indicated that they are strongly considering purchase of the leased system.

The Vadnais Corporation is building a reputation for the specialized utility construction exemplified by the Santa Ynez and San Diego microtunnels. With these successes behind them, Vadnais is primed for new challenges within this niche construction.