Questions___Answers_-_Round_3_0004.pdf

Question / Comment BOR Response Shumway Pilot Bore & HDD: CLINs 1-8 & 1-9 both are shown as 2,000 linear feet. This is the distance of the metallic Shumway HDD option shown on drawing 1695-D-62450. Specification 33 05 22 and drawing 1695-D-61852 give the contractor and option to perform an 1,100 plastic Shumway HDD. There is no way to present the plastic 1,100 linear foot option on the current bid form. This could potentially cause an unfair evaluation of a proposal. Can a line item be added to the bid form that allows the contractor to chose either the 2,000 LF Metallic or the 1,100 Plastic option for the Shumway HDD?

Please indicate that plastic pipe is being used and modify quantities accordingly.

SPEC 33 05 22; Paragraph 3.04.L.4.a.1 - Amendment 0003; For Nenahnezad Bluff HDD, reaming step sizes shall not be greated than 6-inches in diameter per pass. The amendment No. 3 HDD specification allows reaming step sizes for all crossings except for the Nenahnezad Bluff HDD to be 12-inches in diameter per pass. The Nenahnezad Bluff HDD specs state that it shall not be greater than 6-inches in diameter per pass. We understand that the intent is successful preparation of the bore hole, however we have concerns that this approach will increase the risk and cost as compared to conventional methods for reaming. The selection of the various reamer/hole opener sizes is very much a preference (means and methods) and highly dependent on the HDD drill rig (torque and pull/thrust capabilities), mud pump’s flow rate and pressure, as well as the design of the hole openers. The configuration, cone/cutter size, IADC code, jet sizes, and other factors all work together as a system to efficiently perform bore hole reaming. Limiting the step size to 6-inches would require Nenahnezad Bluff to be completed in up to 9 passes including the pilot hole. This would dramatically increase project cost and time, potentially pushing the completion of the project outside the period of performance.

Additionally, this does not allow the hole opener to operate as it designed. A hole opener is made to use the full face of the cone, this allows for the weight used to fracture the rock to be distributed evenly across the entire cone. This alleviates side and front loading which can cause premature wear on the bearings which could lead to failure and the loss of the cone. (One would see this in the 18”-30” passes as the segments would be made from a 9 7/8” to 12 ¼ bit segments due to the size of the reamer.) The specification limitation of 6-inch step size increments does not follow industry standards. The industry has realized that reaming should be done in as few passes as possible while maintaining mud cleaning efficiency and cuttings removal. We are concerned that this requirement will likely lead to a failure and loss of a cone, which may or may not be able to be extracted. Our recommendation is to require that the pilot hole be reamed to a minimum of 12-inches greater than the OD of the pipe but eliminate the 6-inch step Nenahnezad and 12-inch step for the other crossings.

No change will be made.

SPEC 33 05 22; Paragraph 2.05.B.1.c.; HDD Steel Pipe Wall Thickness; After reviewing the contract documents regarding the steel pipe wall thickness, the noted requirements are all based on internal pressure. This is certainly appropriate for the safe operation of the pipeline, however the stresses that are necessary for pipe installation by horizontal directional drilling are typically much larger than operating stresses and therefore require a much thicker pipe wall. The wall thickness design for HDD installation is a much more rigorous procedure than using the Barlow formula and may not be fully evaluated prior to awarding the project and result in one or more of the bidders selecting a wall thickness that does not meet the installation stress requirements. A similar concern exists in specification 33 05 22 2.05.B.2.a.2.a where it states the HDPE pipe will have a Maximum DR: DR13.5. We believe that for the HDPE Shumway HDD a minimum of DR11 should be considered.

No change will be made.