Lessons Learned

The City of X and its engineer bid during summer 2005, 3,200 ft of 36-in. HDPE pipe for a lake crossing to be installed via horizontal directional drilling (HDD) in order that this water transmission line could be put in service by May 1, 2006.

On  July 14, 2005, when bids were tabulated, Company X became the lowest bidder at $1.74 million. The contract completion date was agreed upon as Nov. 1, 2005, at the pre-construction meeting held on Aug. 16, 2005. The entire, final design and alignment selection were based on only four soil borings, and no appropriate geotechnical baseline report was ever done or used by the engineer or its HDD consultant.

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The driller had so many problems that could have been anticipated even if one of the parties involved in this project spent a few more minutes studying the implications of the four soil borings. I was retained on Nov. 14, 2007, by the law firm representing the driller to conduct an independent investigation as to the causes that led to the delay and cost overruns on this project after the driller had been at the site for longer than 1,000 days and had spent more than $6 million by their estimate. Loss of drilling fluids, caving of roads, settlement of houses, buildings and other calamities were the outcome that the driller, the engineers and the city faced. The lives of local residents were disrupted for many months. There were many lessons learned and I share them with you in the hope that similar problems can be avoided in the future.


The topics of discussion as recorded in the minutes of the preconstruction meeting on Aug. 16, 2005, clearly indicate that the engineering firm, its HDD consultant and the city’s Board of Public Works presented an over-simplified view of the technical challenges of this project when it came to the choice of pipe material, method of construction, utility concerns, environmental issues, shop drawing submittals, traffic control, permits, soil erosion and sediment control, testing requirements, resident communication and settlement monitoring, among others. The design of this pipeline — to be installed by HDD — and the site inspection were done by the engineering firm and its HDD consultant, but unfortunately contained errors and omissions.

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I also visited the project site and met with the driller’s team in December 2007. Within mere minutes of review of the four soil borings and the line and grade shown on the drawings, it became obvious that even the most rudimentary details of geotechnical engineering practice had been missed by all parties.

Geotechnical Setting

The site is located on the south shoreline of Lake X. The surface geological maps for the State indicate that the site is underlain by Pleistoncene and Holocene sediments containing sand dunes underlain by lacustrian or lake sands and gravels. There were four sets of geotechnical borings that were done as follows:

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a) Geotechnical Borings during March 2005

The design of the project was based on only two soil borings on land. These borings were done in March 2005 and reported in May 2005. These two soil borings encountered sand and silty sand with overlying sandy silt with some lean clay at deeper depths. Clay and silt lenses were encountered within the upper sand and silty sand. Silty sand was encountered within the sandy silts. Sand seams and gravel were encountered within the lean clay. The sand and silty sand were medium dense to dense, the silt was stiff to very stiff and the lean clay was stiff to hard in consistency. Slightly shallower water tables were encountered in the land-side borings at about 579 ft compared to the water level in the lake being at 578.6 ft.

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Two additional borings were conducted from a barge into the lake bed. Test borings in the lake showed that the soils are primarily sand and silty sand near the surface underlain by soft under consolidated and normally consolidated sediments. There were also gravel lenses, very soft organic silts underlain by medium dense to silty sands. There was also lean clay with some cobbles at deeper depths.

Bed rock depth ranged from 450 to 500 ft in the region while even at boring depths of 485 ft, no bed rock was encountered among the four borings done for this project. The above geotechnical data was found to be inadequate by the driller, the engineering firm and its HDD consultant and the Board of Public Works when various technical challenges surfaced. Unnecessary technical debates broke out numerous times even on scientific knowledge widely accepted and have been part of standard geotechnical engineering practice.

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Due to the fact that the original soil borings of March 2005 did not provide sufficient data on how to settle such debates, additional geotechnical investigations were carried out during September 2006, September–October 2006 and December 2007 as follows:

b) Geotechnical Borings During September 2006

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Eight soil borings were performed on the south side of the recovery shaft with boring depths ranging from 30 to 45 ft. The soils consisted of sandy fill overlying fine silty sand to depths of about 30 to 38 ft. The sand was very loose to medium dense. The very loose soils were generally encountered between 15 to 30 ft. At one boring performed near the recovery shaft and above the steel casing installed for the last 100 ft of the 3,200-ft long HDD drive, the sand just above the casing appeared to be mixed with bentonite drilling slurry. Below the silty fine sand, a sandy silt-silty sand with clay seams and layers were encountered to a depth of 45 ft.

These soils were generally medium dense to stiff in consistency. Cement grout was encountered in a few of the eight borings closer to the recovery shaft. Groundwater depth was between 12 and 13 ft from the ground surface. The GeoProbe rig, used on the north end of the recovery shaft, located HDPE pipe that had gotten stuck.

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c) Geotechnical Borings During September-October 2006

Twelve soil borings were done to verify the geotechnical investigation that was done during September 2006 and thus provide data quite similar to what was already collected. It is unfortunate that the engineering firm and its HDD consultant ordered these 12 soil borings and associated geotechnical investigation and had the Board of Public Works pay for these somewhat too late in the process of characterizing the site conditions. If indeed all of this data was collected by the engineering firm and its HDD consultant in advance of designing the project to avoid an experimental HDD 3,200-ft long drive with 36-in. HDPE pipe, the intended water transmission pipe could have been designed and built much faster and more economically with better pipe material using some other construction method with a proven track record.

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d) Geotechnical Borings During December 2007

When it was suspected that there was the possibility that a deeper aquifer was feeding the groundwater to cause sand boils, making dewatering of the recovery shaft ineffective and unsafe for the workers, a fourth set of soil borings were done during December 2007. In the first soil boring at piezometer location #300, a clay layer was encountered from 37 to 48.5 ft underlain by silty fine sand to a depth of 61 ft. From 61 to 67 ft, sandy silt was encountered over silty clay. At the second soil boring where the second piezometer #301 was planned to be installed, silty fine sand was reported from 37 to 55 ft with some silty clay. Loss of drilling mud, causing the HDPE to seize during the September 2005 installation, occurred between 45 to 50 ft in the first soil boring where piezometer # 300 was planned and from 35 to 40 ft at the second soil boring where piezometer #301 was planned. Groundwater levels during drilling were observed at depths of 15 to 20 ft at these two soil borings. The standard penetration test blow counts were from 44 to 58 in sandy silts and 8 to 13 in silts and clays. When the tips of the piezometers were set at about 69 to 70 ft with 20-ft long screens, a lower aquifer was detected providing a rational explanation for a major groundwater anomaly that contributed to the loss of drilling fluid during September 2005, seizing of the HDPE 36-in. pipe about 150 ft short of its target and excessive amount of water entering the recovery shaft during the driller’s repeated good faith efforts to dewater the recovery shaft adequately to be able to complete the project.

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Evaluating the Engineer’s Design Report

It became quite clear while examining the engineering firm’s preliminary design report that the engineer of record simply did not have anyone on their staff with the appropriate qualifications and experience to handle the challenges of this project. The decision to go with HDD as the construction method for the lake crossing was based on two land-based geotechnical borings. The route evaluation was based on a site visit by its HDD consultant on Nov. 29, 2004, utility mapping data and aerial imagery. Potential drilling fluid loss and associated road heave or settlement and the risk of impact to be reduced by setting surface casing during construction to contain drilling fluid, were all considered. Although an open-cut construction alternative was estimated to be cheaper, this construction option was never offered to the bidders.

Despite the fact that the design team and the Board of Public Works were aware of potential construction problems using HDD vs. open-cut construction, the preliminary design report contained in one section: “Open-cut trenching, directional drilling and bore and jacking are all methods [that] can be used to construct the proposed transmission water main. Of the three options, open-cut trenching is the least expensive, provided space is available. Given that sufficient space exists along all portions of the land based route for open-cut trenching, this is the recommended installation method.”

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In another section of this report, however, the engineering firm wrote: “Based on the results of two geotechnical borings, it is our opinion that subsurface conditions are conducive to the HDD process.” The engineering firm’s report also contained: “The technical feasibility of a proposed HDD installation is governed by three basic parameters: drilled length, pipe diameter and subsurface material. These three parameters work in combination to limit what can be achieved at a given location.”

When the engineering firm discussed the risk associated with subsurface conditions, it added: “While length, diameter and subsurface material work in combination to limit technical feasibility of an HDD installation, technical feasibility is primarily limited by subsurface material.” The engineering firm also wrote: “Soils consisting principally of coarse-grained material present a serious restriction on the feasibility of HDD.”

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Gravel was encountered, however, in the geotechnical borings but was somewhat ignored by the engineering firm and its HDD consultant when they were negligent with the choice of the construction method of HDD.

It is ironic that the brief geotechnical report is dated May 2005, while engineering firm’s preliminary design report was done on April 18, 2005, ahead of geotechnical findings, implying that the engineering firm and its HDD consultant simply went through the motions of doing the minimum geotechnical exploration work on establishing the subsurface conditions and did not rely on even this little data to decide on the construction method it chose for this lake crossing. The preliminary design report talked about needing extreme care when the drill path crossed under the petroleum line, yet no performance criteria were presented for allowable construction-induced vertical and horizontal movements of the petroleum line.

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The engineering firm’s and its HDD consultant’s lack of geotechnical and pipeline engineering experience and their improper choice of HDD for the construction led to numerous problems throughout the construction phase of this project. It is ironic that the negligent conduct by the engineering firm and its HDD consultant during the design and construction phase resulted in increased billable hours and out-of-pocket reimbursement paid to the engineering firm and their HDD consultant from the Board of Public Works.

Actual Conditions vs. Those Known During Bidding

The geotechnical conditions the driller faced at this site were dramatically different from those represented by the design team. The design team simply completed the design drawings and specifications and bid the project in a hurry. By doing so, the design team passed on its risk to the driller, knowing that there would be problems during the construction phase. No one among the Board of Public Works, engineering firm and its HDD consultant and the driller really understood the geotechnical engineering data on hand and the challenges they faced at any time during the entire period of this project.

Engineer Excess

The language in the contract defined the engineer’s status as follows: “The engineer shall have general supervision of the work. He has authority to stop the work whenever such stoppage may be necessary to [ensure] that the finished work will be in accordance with the plans and specifications. He shall also have authority to reject all work and material that does not conform to the plans and specifications.”

By using the above clause, the engineer was involved essentially on a daily basis, directly and excessively in controlling the means and methods chosen by the driller. The engineer delayed the execution of this contract by the driller by not being cognizant of the body of engineering knowledge on pipeline materials, design and construction. The engineer also was not familiar with national standards and codes and about the widely accepted engineering practice of underground pipelines made of various materials and constructed by different installation techniques. The engineer also was not familiar with the state-of-the-art performance criteria on allowable settlements of residential structures and buried pipelines, allowable vibration induced effects on nearby structures, allowable crack widths in residential buildings, effects of dewatering on settlements and other.

There were protracted technical debates during meetings and in correspondence ensued, severely affecting the rate at which the driller was authorized by the engineering team to proceed with the means and methods the contractor chose. Every performance criterion that the engineering team used to either accept or reject among the means and methods or finished work by the driller, had to be debated and agreed upon often in an arbitrary and highly stringent nature without any engineering merit or national precedence. It is quite clear from the record that when the driller bid the project, he was completely  unaware that any of these performance criteria would be introduced day-to-day by the engineering team in order to either accept or reject work. This situation posed a new set of conditions that were unknown at the time of the award of the contract.

Change of Scope

The engineering team completed an experimental design using a highly risky HDD construction method based on insufficient knowledge about the subsurface conditions and it ignored the caution shared among experienced geotechnical engineers nationwide on HDD technology regarding its limits and about the inappropriateness of HDD as a viable construction method for such a long 36-in., HDPE lake crossing.
The engineering team also set aside its own geotechnical subconsultant’s guidance based on the limited soil boring data that showed problematic gravel seams, cobbles and extremely loose deposits of granular material with very low blow counts. Even as early as in April 2005, the engineering team knew that HDD would not be an appropriate construction method, would carry higher risk and would cost more compared to an open-cut option yet, on behalf of the Board of Public Works, bid a set of  specifications that were flawed, overly broad and with no specific performance criteria for the driller to meet on many accounts.  

Dr. Jey K. Jeyapalan, P.E., is with Civic Enterprises LLC, New Milford, Conn.


The following opinions were formed in this independent investigation:

  1. There is sufficient evidence that what the driller faced at the jobsite, in its dealings with the engineering firm and its HDD consultant and the Board of Public Works, were materially different from their representations when the project was awarded.
  2. The design is defective in many aspects. The author was never able to obtain an acceptable set of design calculations from the engineering firm, its HDD consultant or the Board of Public Works, given the problems with the choice of plan, profile, pipe material choice, etc. that the driller faced at this jobsite.
  3. The contract technical specifications were defective. The engineering firm, its HDD consultant and the Board of Public Works — either due to lack of sufficient expertise or deliberately — left out the performance targets in the bidding specifications, choosing to delay the progress of the driller by enforcing changing specifications with performance targets that were overly stringent, arbitrary in nature and without any engineering merit.
  4. The nature in which the engineering firm, its HDD consultant and the Board of Public Works kept changing the scope of work is significant.
  5. There is ample evidence that not only the Board of Public Works, but the engineering firm and its HDD consultant decided to force numerous means and methods on the driller without ever affording the public to benefit from the driller’s expertise. The engineering firm, its HDD consultant and the Board of Public Works sometimes forced incorrect methodologies on the driller, which resulted in additional delays.
  6. The selection of suitable materials and construction methods for underground pipelines does not happen by accident. It requires decades of experience and sound knowledge of geotechnical engineering practices and pipeline engineering and good judgment derived from having worked on hundreds of similar projects.

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