Buchart-Horn Design Includes Horizontal Directional Drilling Under Tidal Creek

Buchart-Horn Design Includes
Horizontal Directional Drilling
Under Tidal Creek

Crew joins sections
for new sewer line.

Upon the discovery of fiber-optic, telephone and cable TV lines under a highway where they had once hoped to place a force main for the Dandy Vacuum Sewer System, engineers from the York County, Virginia Department of Environmental and Development Services and Buchart-Horn Inc.'s Williamsburg office found an innovative alternative route.

Their solution -- horizontal directional drilling to place the six- inch line under a 600-foot wide tidal creek and 200-foot wide wetlands. (See the Spring '97 PACEsetter)

C. Lewis Waltrip, Inc, the prime contractor and Wayjo Construction, the specialty drilling subcontractor began staging equipment next to Back Creek on Monday, June 30th. The drill rig, drill sections and equipment to bore an initial three-inch "guide" hole were located on the north shore of the Creek.

Meanwhile, on the south shore, another crew fused 40-foot long, six- inch sections of HDPE pipe into an 800-foot flexible force main that was carefully laid out on the flat terrain like a giant black snake basking in the sun. A special reamer, universal joint and pullback head were also set at the containment area on the south shore.

As drilling of the three-inch passageway began from the north shore on July 1, technicians monitored the progress with a special sensor that accurately tracked the horizontal, vertical and angular progress of the magnetized drill head so the machine operator could steer the bore exactly where it was designed to go. The initial three-inch bore came up right on target and the drill rig was then fitted with a ten-inch reamer for the pull-back that would bring the flexible six-inch force main to the north shore.

An unfortunate equipment failure on July 2nd led to an unsuccessful initial pullback and loss of the drill-head and a large portion of the force main.. Fortunately, The County of York, Virginia, was protected from this mishap by Buchart-Horn specifications that directed that the contractor would be paid only for a completed, tested sanitary force main under the creek!

After a break in the work for the Fourth of July holiday and contractor analysis of the equipment failure, the process began anew. A parallel rebore was done on July 11th and a successful pull-back of the force main was completed on July 12th.

The boring required special environmental permitting since the pipeline was placed under wetlands and a tidal waterway. Buchart-Horn secured permits for the client from the U.S. Army Corps of Engineers and from the Virginia Marine Resources Commission. The project is part of B- H's design work for York County, Virginia's Dandy Vacuum Sewer System that will eventually discharge to the York River Treatment Plant.

The Dandy system will serve approximately 300 homes through 22,000 feet of vacuum collection lines, a central vacuum station and 7,000 lineal feet of offsite six-inch force main. The force main under Back Creek is one of the final components for the system that will begin service this year.

The Dandy Vacuum Sewer is one of four recent systems of that type designed by Buchart-Horn. The Seaford Vacuum Sewer (also in York County, Virginia) was completed in 1995 and its success led to B-H designs for similar systems in the Sandbridge area of Virginia Beach, Virginia and York County's Dandy system. B-H also designed a vacuum sewer system in Queen Anne's County, Maryland.

Vacuum sewer systems and precise small-diameter horizontal drilling are both technological advances that Buchart-Horn is using to increase the feasibility and lower the costs of important environmental projects.

Buchart-Horn has gained a reputation for its vacuum sewer system design, especially in tidal areas where traditional gravity sewers are costly to construct due to deep trenching difficulties caused by sandy soil and a high water table. In contrast to gravity sewers that require trenches as deep as 20 feet, vacuum lines can follow the topography and need only be buried three to seven feet beneath the surface.