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Application of Horizontal Directional Drilling to LimitedRight-of-Way Gas Pipeline Design and Construction, a Case Study

William H. Godwin1 and Fred Valenzano2

Abstract

This paper presents a case study of a gas pipeline project in a highly congested area whereconventional installation techniques were not physically or politically feasible. The project,located in the city of Antioch, California, consisted of installation of 2 miles of 16-inch and 5miles of 24-inch diameter pipeline sections to supply natural gas to two new power plants beingbuilt along the San Joaquin River. Limited workspace and environmental concerns alongsignificant portions of an identified right-of-way required utilizing the Horizontal DirectionalDrilling (HDD) and other trenchless techniques. Acquiring geotechnical information along thepipeline alignment was important to the design and cost considerations for this project.Construction of the pipeline was completed in 2000 using HDD, slick bore, and conventionaltrench and bury methods. Several of the HDD crossings for this pipeline are near world-recordlength for the pipeline diameter.

Introduction

This paper will describe how Horizontal Directional Drilling (HDD) was instrumental in theinstallation of a natural gas pipeline to supply to two new power plants being built along theshoreline of the San Joaquin Delta, in northern California. The paper discusses solutions to theissues encountered during the permitting, design, and construction phases of work.

The project is located within the cities of Antioch and Pittsburg, California, on the southernshoreline of the San Joaquin River (see Figure 1). The purpose is to transport natural gas viaburied steel pipelines 11.44 kilometers (km)(7.11 miles) from a Pacific Gas and Electric (PG&E)91 centimeter (cm) (36-inch) pipeline in eastern Antioch to two new gas-fired power plants,under construction in Pittsburg, California. The project team was a joint venture of CalpineCorporation, Inc (Calpine) of San Jose, California, and Bechtel Enterprises (Bechtel) of SanFrancisco, California, and the pipeline designer, C&H Engineering of Bakersfield, California.Trident Engineering of Antioch, California provided preliminary civil engineering and surveyservices, and Petroleum Properties of Rio Vista, California, was the lands permitting agent.

1 Senior Engineering Geologist, C.E.G., Affiliate Member ASCE, Harding ESE, 90 Digital Drive,Novato, CA 94949, (415) 884-3275, Fax (415) 884-3300, whgodwin@mactec.com2 Project Engineer, C&H Engineering, 6840 District Blvd., Bakersfield, CA,93313, (661) 835-5920, Fax (661) 835-5925, fred_vee@yahoo.com

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Environmental Challenges

The Dow Wetlands Preserve is a 60 Hectare (Ha)(150 acre) site east of the DEC site, see Figure1. The property is managed by Dow Chemical and includes an upland site used for birdwatching and nesting. Other marginal wetland areas are found further to the east in thedowntown Antioch and Fulton Shipyard areas. Wetlands are not conducive to conventionalpipeline construction and contain sensitive resources of biological, archeological and historicsignificance. It was recognized that impacts to these resources by vehicular traffic, noise, runoffand chemicals would be detrimental and difficult to permit. Additionally, hauling trench spoil bytruck through downtown Antioch and closing down city streets for long periods of time wouldrequire permission of annoyed landowners and skeptical local officials.

Engineering Challenges

The project presented several major engineering challenges as well. Conventional pipelineinstallation in the low-lying areas would require trenching in soft sediments beneath the watertable. Water or canal crossings would require sheet pile walls or working platforms.Stabilization and relocating underground utilities would be required in some instances. Crossingthe Burlington Northern and Santa Fe Railroad (BNSF), a very busy, single-track freight andpassenger railway would require significant restrictions imposed by the railroad. NorthernCalifornia is an area of high seismicity, and although buried steel pipelines generally performwell during earthquakes, serious issues of liquefaction and earthquake-induced ground settlementwould need to be addressed.

Route Selection

Following an analysis of the route by permitting agents and engineers and subsequentdiscussions between state, county and city officials and the project team it was determined thatportions of the BNSF Right of Way (ROW) would provide the best pipeline route. The rationalewas that the BNSF corridor provided the shortest distance between the PG&E tie-in and the twopower plants. Also, pipe joints could be transported to the jobsite by rail and pipe strings couldbe assembled alongside the track. Most importantly, only one owner (BNSF) would need to bepermitted over the most difficult sections of the project. All told the BNSF route would allowinstallation of 3.21 km (2 miles) of 40.6 cm (16-inch) and 8.05 km (5 miles) of 61 cm (24-inch)diameter pipeline sections alongside and beneath the active railroad; see Figure 1.

One disadvantage of the BNSF right-of-way was that it averages only 7.62 meters (m) (25 ft) inwidth. In most cases this is adequate for small diameter infrastructure, (e.g. fiber optics, or cable)but it is not sufficient for 61cm (24-inch) gas pipeline construction. The BNSF established a“Code 3” requirement that limits construction to a minimum of 2.67m (8.75 ft) from thecenterline of the active rail track. This is to ensure the safe passage of trains travelling at highspeed by maximizing the distance between construction-related obstructions and the passingtrain and also to prevent settlement or movement of the track and underlying ballast. Thissituation was most acute in the downtown section along the river edge. As shown in Figure 2, the

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rail right of way borders the waterfront that contains riprap, soft sediments and partially buriedwooden pilings. On the eastern edge of downtown the BNSF crosses over a 335m (1,100 ft)trestle and BNSF policy forbids installing the pipe along any bridge or trestle, even if it weretechnically feasible.

A decision was made to investigate HDD techniques as a solution to these problems. HDD is atrenchless method of installing underground pipe. It is typically used in river or large open waterpipeline crossings, and in this case was perceived as a viable alternative. Locally HDD had beenused for several river crossings including the Sacramento River, California (PersonalCommunication, 2000a). The world record for HDD crossings of 61cm (24-inch) pipe was1841m (6041 ft), beneath the B. Everett Jordan Lake, North Carolina, in 1999 (P&GJ, 1998). Itwas felt that HDD bores of 1520 to 1830m (5000 to 6000 ft) would be possible. However asingle reach extending from Arcy Lane to Fulton Shipyard Road, a distance of 3048m (10,000 ft)was discounted. After route selection, the design team began the permitting process. Thisrequired coordination with California State Lands Commission, California Energy Commission,Department of Fish and Game, US Environmental Protection Agency, City of Pittsburg, locallabor unions, Contra Costa County and the City of Antioch.

Geotechnical Investigation

In order to evaluate the feasibility of the HDD routes and provide information for HDDcontractor bidding, it was necessary to conduct a geotechnical investigation. The scope of theinvestigation was based on HDD industry guidelines (DCCA, 1995). Borehole and probespacing and depth were based on the geometry developed for the estimated crossing depths andlengths. The exploratory locations were positioned such that all encroachment permits could beobtained from the city of Antioch. Other drill hole data was obtained from projects within theproject area to supplement the new program. The geotechnical investigation program,summarized in Table 1, was conducted from January to March, 2000 under the direction of aBechtel engineering geologist. Tri-County Drilling of San Diego, California, drilled 16 StandardPenetration Test (SPT) borings, totaling 471m (1546ft) using mud-rotary drill methods tosimulate HDD drill operations. Sufficient distance was maintained between the pipe alignmentand the drill locations and the borings were tremie grouted to minimize the likelihood of frac-out.

Table 1. Geotechnical Program Summary

GeotechnicalMethod

Dow WetlandsHDD (No.)

Downtown AntiochHDD (No.)

Fulton ShipyardHDD (No.)

Slick Bore andTrench and Burial

Areas (No.)Test Borings (SPT) (4), depth-6 to 43m

(20 to 140ft)(6), depth-43m (140

ft)(3), depth-18 to 43m

(60 to140 ft)(3), depth-6m (21 ft)

Cone Penetrometer(CPT)

(2) 33m (108ft) (5) 28 to 38m(93 to126ft)

(1) 31m (100ft) None

Laboratory Testing x x x xGeophysics! EMLL x x x! GPR x! TC x x x x

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Soil samples obtained from these borings were tested in the laboratory for engineering index andstrength properties. These tests included sieve analysis, unconfined compressive strength, drydensity and moisture content, and Atterberg limits. The grain size data coupled with drill mudproperties recorded during the drilling operations provided data the HDD contractor could use todetermine drill mud density and viscosity required for bore advancement and lifting of reamcuttings. The strength tests and unit weight allow the contractor to determine the optimal depthfor drilling and for buoyancy control.

Gregg Drilling, Inc., Walnut Creek, California advanced 8 Cone Penetrometer Test (CPT) probestotaling 262m (860ft). In some cases the CPT’s were pushed alongside the SPT borings forcorrelation purposes. The CPT’s allowed timely and continuous read outs of soil parameters oftip resistance, skin friction and pore water pressure. These data allowed the HDD designers tocharacterize the subsurface conditions and chose the optimal depth horizon for drilling.

Norcal Consultants, Inc., Petaluma, California conducted geophysical surface surveys todetermine the presence of buried utilities within the HDD entry and exit pit locations, and slickbore pits. This geophysical mapping information delineated areas of potential interference to thetrenching operations and steering tools employed during the horizontal drill bit advancement.The geophysical methods included electromagnetic line location (EMLL), total conductivity(TC) and ground penetrating radar (GPR). The areas of investigation consisted of a single 366m(1200ft) direct burial trench, ten (10) HDD pits of various sizes and a suspected undergroundstorage tank.

Subsurface Conditions

The geotechnical data was compiled into a Geotechnical Data Report that was included as part ofthe Request for Proposal (RFP). In general, the subsurface conditions are characterized as adeltaic environment consisting of alternating mostly fine and medium-grained sand lenses andsandy silt. There were isolated pockets of coarse sand with some gravel in the downtown andDow wetland areas. In the shoreline areas that could be accessed with drilling equipment, weobserved thin fill over thick deposits of highly organic clay, or clay and peat mixtures. At depthsof 80 to 100 feet a hard pan clay interval was observed in majority of the borings on the project.

A particularly interesting site was investigated at the north end of McElheny Road. One parcelwas chosen as a combination entry and exit pit work area, and it necessitated a rigorousinvestigation program. This area previously was an old slough and boat marina before it wasfilled. We detected evidence of buried construction debris, an old barge and a nearbyunderground storage tank, and in some areas there was fill settlement that resulted in buckledpavement, as shown in Figure 3. The property contained monitoring wells installed downgradientof a release of strychnine from an old apricot processing facility to the south.

Bisecting the downtown and Dow wetland HDD sections in the vicinity of the Antioch Marina isthe northwest trending Antioch fault. While it is no longer considered an active fault (CDMG,

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1991), and the likelihood of fault rupture across the trace is therefore very low, it was recognizedthat because the project area is within the 1997 UBC Seismic Zone 4 (ICBO, 1997) there is asizeable earthquake hazard risk. Active seismicity is attributable to the San Andreas Faultsystem. This system includes the Concord-Green Valley and the Hayward fault to the west. TheHayward fault can generate sizeable earthquake magnitudes (Mm=7.0) and peak groundaccelerations (0.53g). At the request of the State Lands Commission a liquefaction analysis wasperformed (Seed and Idriss, 1971) by Bechtel geotechnical engineers to determine thesusceptibility of the steel pipeline to deformation and flotation in near surface areas. It foundthat, with the exception of isolated pockets of liquefiable soil, there would not be generalizedinstability along the HDD segments.

Contractor Bids

Calpine issued an RFP to six Pipeline contractors on April 10, 2000. The bid package specifieda preferred alignment and requested all work required to trench or drill, layout, weld, place,cover, and test approximately 7 miles of pipeline. The cost of the pipe specified, 61cm (24-inch), 0.500 w.t. X65 was approximately $2 million, and would be paid by Calpine. The RFPidentified 3 HDD sections as summarized in Table 2. Five bids were returned with the winningbid going to ARB Constructors, Inc. (ARB) of Pittsburg, California. ARB was to construct 5miles of trench and bury sections for a cost of $5 million and provide welding and support forHDD operations for approximately $1 million. Calpine had previously let separate bids for theHDD work. Calpine contracted the HDD work to Horizontal Drilling Inc (HDI) of HoustonTexas for approximately $2.5 million. The total cost of the project was estimated at $11 million.

Table 2. Pipeline Reaches Summary

SpreadLength inmeters (feet)

Entry/Exitangle (degreesfromhorizontal)

Depth andradius inmeters (feet)

Diameter incentimeters(inches)Pilot/final

Comments

Dow Wetlands 1483 (4865) 10/8 d= 16.8 (55)r= 914 (3000)

8.75/ 42 Became stuck,some lost drillstring and Fracout

DowntownAntioch

1456 (4776) 10/8 d= 30.5 (100)r= 914 (3000)

8.5/42 56 days, Frac out

Fulton ShipyardRoad

562 (1845) 10/12 d= 15.2 (50)r= 732 (2400)

8.75/36 Minimalproblems

HDI identified 3 HDD sections as shown in Figures 4a and 4b. The Dow Wetlands section, thelongest at 1483m (4865ft) was to extend from east of Arcy Lane to the Antioch Marina. Thecenter downtown section was to extend from Antioch Marina to McElheny Road. The third andshortest section was from McElheny Road to Fulton Shipyard Road.

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Pipeline Construction

HDI was given notice to proceed in May of 2000 and mobilized an HD-650 rig and crew from arecently completed Calpine HDD project at the Sutter Bypass, in Sutter County, California193km (120 MI) to the north. The first phase of construction began for the slick bore and trenchand bury sections on several spreads simultaneously. These included the 40.6 cm (16-in) pipelinewest of the DEC.

The HDD subcontractor chose to make the Dow Wetlands crossing first. On July 7, 2000, a pilotbore of 22.2cm (8 3/4-in) with an entry angle of 10 degrees was made from the Antioch Marinato the west, as shown in Figure 5. Frac-out was observed in two locations within the wetland andthe fluid was quickly isolated. A reaming pass enlarged the bore to 91cm (36-in) but the drillstring became stuck near the end of the HDD and was almost completely lost. Another shipmentof drill tubing was delivered and a second attempt was made 7.6 m (25 ft) to the north but noshallower. This attempt was again unsuccessful, but the drill string was recovered. The HDDcontractor decided to relocate to the Fulton Shipyard section to allow the drilling of sixadditional geotechnical borings for analysis of the problem area. Eventually, the drill rig wasreturned to the area and set up in a wildlife observation area roughly at the midpoint of theWetlands Section. Two shorter HDDs were completed from this point, one ending in the originalHDD rig set-up site near the Antioch Marina, and the other ending up near the original ArcyLane exit location.

The Fulton Shipyard crossing was made with minimal problem. The rig was set up at the eastend at old marina site mentioned previously. A pilot bore advanced eastward, passed into theBNSF ROW for most of the HDD length, then exited onto City of Antioch property. The pipewas successfully pulled through in late August, 2000.

The downtown section was started on August 31, 2000, after approval by the City of Antioch.The rig was rotated 180 degrees and a 22.2cm (8.5-inch) pilot hole was begun. It was advancedbeneath the river adjacent to the trestle and extended north of the downtown piers and areas ofpiling. This pilot bore took approximately 45 days to complete. There were many events thatstopped drilling, (Personal Communication, 2000b). Pilot hole drilling had to stop several timesdue to encountering very hard, cemented sands offshore, approximately 100 ft. north of therailroad trestle. There were also numerous frac-outs, one particularly at the south end of a publicparking lot, about 200 linear feet from the drill path. After 2 reaming passes and swabbing thefinal 107cm (42-in) hole received the pipe on October 23, 2000.

In addition to the HDD, nineteen slick-bored crossings of the BNSF tracks were made by ARB.Three of these were over 100 feet in length with ten feet of cover, and one cased crossing of asmall wetland was made with a length greater than 200 feet. Sixteen of the other slick-bores weremade within the BNSF right-of-way. Much of the remaining pipeline ditch was opened usingbackhoes, as the space was too narrow for trenchers and side booms to handle the pipe.

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Conclusions

This project would not have been technically feasible without HDD technology. Conventionalcut and cover trenching construction techniques would have required significant amounts oftrench dewatering, spoil removal and disposal, and would not have been possible based on spaceallocation and restrictions along the BNSF railroad. HDD was successfully used to surmountthese obstacles. There were construction problems, associated with subsurface groundconditions but these were alleviated after acquiring additional geotechnical information and withcontractor familiarization. HDD allowed a majority of the pipeline to be installed withoutdisrupting traffic and while minimizing landowner permitting and concerns.

References

California Division of Mines and Geology (CDMG) 1991. Fault Evaluation Report FER-228Evaluation of the Antioch Fault, prepared by Christopher Wills, C.E.G., and dated November 6,1991

Drilling Crossing Contractors Association (DCCA), 1995 “Guidelines for a SuccessfulDirectional Crossing Bid Package” Adopted by DCCA Guidelines Committee, April 21, 1995

International Conference of Building Officials (ICBO), 1997. 1997 Uniform Building Code

Personal Communication, 2000a. Conversation with Larry Bertolucci, CherringtonCorporation, regarding the 1993 42-inch, 4200 ft crossing by the PG&E gas pipeline, Sept 10.

Personal Communication, 2000b. Conversation with Joe Provenza, C&H Engineering,regarding the Downtown HDD, February 12.

Pipeline & Gas Journal (P&GJ) 1998. “Record 24-inch HDD Made on Cardinal PipelineExtension” Pipeline & Gas Journal, June, 1998 p20-25

Seed, H.B. and I.M. Idriss 1971 “Simplified Procedure for Evaluating Soil LiquefactionPotential,” Journal of the Soil Mechanics and Foundations Division, ASCE, 97(SM9), p1249-1273