8Re: Northern Access 2016 Project. Ischua Creek Crossing (MP 62.4) Analysis of Feasibility and Risks of Direct Pipe Installation

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1 8Re: Northern Access 2016 Project Ischua Creek Crossing (MP 62.4) Analysis of Feasibility and Risks of Direct Pipe Installation Dear Mr. Horey and Mr. Hoover, Mr. Bradden Horey Mr. Brent Hoover P.E. Project Management National Fuel Gas 6363 Main Street Williamsville, NY, Mott MacDonald Group Limited (Mott MacDonald) has prepared this opinion letter at the request of National Fuel Gas Supply Corporation (National Fuel) to summarize the feasibility and significant geotechnical risks associated with a Direct Pipe crossing of Ischua Creek at Milepost 62.4, as part of the Northern Access 2016 Pipeline Project. The opinions presented in the document are those of Mott MacDonald based on available information for the Northern Access 2016 Pipeline Project and are subject to change, if additional information is provided. I. Executive Summary As discussed herein, it is Mott MacDonald s professional opinion that the Direct Pipe Method is not suitable for this crossing for several reasons. Canal Place 520 South Main Street Suite 2457 Akron OH United States of America T +1 (330) First, the Direct Pipe method is a relatively new form of trenchless technology, and is primarily completed in soils lacking gravels, cobbles, and boulders (conditions anticipated under Ischua Creek) for small diameter installations of less than 30 inches. To allow for proper excavation of cobbles and boulders, a 42-inch diameter microtunnel boring machine (MTBM) would likely be required. Second, for the Ischua Creek crossing, the required installation length is greater than 1,000 feet (the recommended limit of this technology per the equipment manufacturer), and thus would require a larger diameter installation (likely 42-inch diameter pipe) than the proposed 24-inch diameter pipeline for the Northern Access 2016 Pipeline Project. However, if National Fuel decided to install a 42-inch diameter pipe for the Ischua Creek crossing, the installation of such an oversized pipe would create an unpiggable pipeline, as multi-diameter inspection pigs that can navigate a diameter change from 24" to 42" are not proven or commercially available. Additionally, while a larger diameter casing pipe could be installed to house the 24-inch diameter pipeline, cathodic protection issues may occur. Third, soils with gravel percentages of 93 percent have been identified under Ischua Creek, which can present significant risk and challenges to the MTBM and the overall installation process, such as the risk of stalling during the proposed crossing and an increase in the potential for annulus collapse and surface subsidence issues. Fourth, on the north side of the proposed crossing, a mixed-face condition of bedrock and soil may exist, further increasing subsidence and sinkhole risks. These risks are associated with over-excavating of the soil materials as the MTBM encounters the bedrock materials. 8Re: Northern Access 2016 Project Page 1 of 6

2 Finally, in the event the MBTM is unable to excavate through a nested cobble zone or boulder, the excavation of a rescue pit would be needed down to the front of the machine in order to clear the obstruction. Depending on where this occurred along the alignment, an excavation from the surface to the MBTM would be a very substantial excavation with very significant surface disturbance. This would negate any environmental benefit that a trenchless method otherwise affords. Given that the Ischua Creek crossing is in very close proximity to a USDA Conservation Easement, National Fuel has inquired about entry and surface disturbance inside of the easement, but has been advised that no entry or surface disturbance is permitted. Each of the aforementioned risks is discussed is greater detail in Section II below. II. Ischua Creek Direct Pipe Feasibility Evaluation and Associated Geotechnical Risks A. Direct Pipe Installations are Not Suitable for 24-inch Crossings As noted above, the Direct Pipe Method is a relatively new form of trenchless technology, and is used primarily for large diameter installations (greater than 30-in pipe diameter), especially in soils containing gravels, cobbles and possibly boulder, which are expected to be encountered under Ischua Creek. Direct Pipe installations for pipe diameters of less than 42 inches are limited to favorable ground conditions (lacking gravel and cobble deposits) and to installation lengths less than 1,000 feet, per equipment manufacturer recommendations. Larger diameter MTBMs can complete longer drive/installation lengths than smaller machines. This is related to the size of the drive motors and other components (such as a cutter wheel equipped with a larger number of disc cutters) that can be incorporated into larger diameter machines. For MTBM installations with diameters less than 42 inches, the achievable installation length in good ground conditions is typically less than 1,000 feet. For larger diameter machines, installation lengths upwards of 3,000 feet have been achieved in favorable ground conditions (soils lacking significant gravel, cobble, and/or boulder percentages). Based on the site constraints for the Ischua Creek Crossing, the required installation length of a Direct Pipe installation is over 1,000 feet. Additionally, for installations in gravels and cobbles, which are expected to be encountered under Ischua Creek, the minimum MTBM diameter is recommended by the manufacturer to be at least 42 inches. For the MTBM to be able to crush down particles it encounters, the particles must be able to pass through the cutter wheel and into the crushing chamber. Depending on rock strength and frequency, the high range for boulder size crushing is typically 30 percent of the outer diameter of the cutter wheel while the low range is 20 percent. For a 24-inch installation, the largest particle that can be consumed by the MTBM is approximately 4.8 inches, which represents a small cobble. To allow for excavation of larger sized particles, a larger diameter installation would be required. For example, a 42-inch diameter MTBM would be able to process a medium-sized cobble up to 8.4 inches in diameter. Page 2 of 6 To allow for excavation of even larger sized particles, the cutter wheel of the MTBM would need to be equipped with disc cutters to break down these larger particles into smaller pieces such that they can pass through

3 the cutter wheel and into the crushing chamber for further break down. However, cutter wheels with sufficiently sized disc cutters are limited to machines of 42 inches in diameter and larger. Additionally, even if National Fuel decided to install a 42-inch diameter pipe for the Ischua Creek crossing, the installation of such an oversized pipe would create an unpiggable pipeline, as multi-diameter inspection pigs that can navigate a diameter change from 24" to 42" are not available. National Fuel must meet the requirement under DOT 49 CFR that " each new transmission line and each replacement of line pipe, valve, fitting, or other line component in a transmission line must be designed and constructed to accommodate the passage of instrumented internal inspection devices". In addition, National Fuel, under DOT 49 CFR 192 Subpart O, is required to perform a baseline assessment of High Consequence Areas on a transmission pipeline and a reassessment minimally every seven (7) years thereafter. National Fuel utilizes In-Line Inspection as its assessment method to meet this requirement for new pipelines. Further, while a larger diameter casing pipe could be installed to house the 24-inch diameter pipeline inside of it, this situation would create numerous potential problems associated with the insertion process and would also pose serious potential for problems with protecting the 24- inch pipeline from corrosion. National Fuel has indicated that it follows industry best practices, which include not using casing/carrier pipe designs due to the potential for electrical shorts between the two pipes. Given the length of the bore, insulators would be problematic and can become disconnected from the carrier pipe, potentially resulting in a direct short. A non-corrosive environment must also be maintained within the casing to compensate for the inability of cathodic protection to reach the cased carrier pipe. Over time, any entry of groundwater to the interior of the casing may result in creation of a corrosive environment and possibly electrolytic communication between the carrier pipe and casing. Once complete isolation between the casing and the carrier pipe is compromised by the entry of water, the casing itself may become part of the cathodic protection circuit, placing additional demand on the protective system, providing unpredictable impact to the pipe within the casing, and suppressing the effectiveness of cathodic protection on uncased pipe adjacent to the cased segment. Because the installation of the 24-inch pipeline within a larger diameter casing pipe would have the aforementioned long term safety implications, such a design has been eliminated from consideration. B. Geotechnical Conditions under Ischua Creek Page 3 of 6 The geotechnical conditions for the Ischua Creek crossing are summarized in the geotechnical report entitled Geotechnical Drilling and Exploration Report Proposed Northern Access 2016 Pipeline HDD Crossing at Ischua Creek (Report) by Urban Engineers of New York, D.P.C. dated March 2016 and revised in July 2016, a copy of which is attached hereto for reference. As depicted in the Report, the anticipated geotechnical conditions include soils overlying bedrock materials. The soils include four (4) distinct soil units including gravel and sand with little to some silt and clay, clayey silt and sand with trace to little gravel, clay and silt with little to some sand and trace gravel, and gravel with trace to some clayey silt and sand. The soils containing gravel are observed to exist with thicknesses up to 100 feet and occur at the ground surface and at various depths below the ground surface (up to at least 175 feet below ground surface on the south side of the Ischua Creek crossing). Grain

4 size distributions completed on selected soil samples indicate gravels with compositions up to 93 percent of the soil by weight. Cobbles were noted at various depths in all of the boreholes. The bedrock material located beneath the soil layers includes interbedded sandstone and shale bedrock. C. The Anticipated Geotechnical Conditions Under Ischua Creek Leads to a Greater Risk of Stalling During Installation Soils with high percentages of gravels, cobbles and/or boulders (as noted in the Report) can present significant challenges to the operation and advancement of the MTBM. Large quantities of gravel and cobbles can choke or stall out the machine. High percentages of gravels and cobbles can also cause significant wear to the cutting tools and crushing chamber. In these soils, the operator is required to control the amount of gravels and cobbles that enter the crushing chamber at any one time to prevent the MBTM from exceeding its torque capabilities and stalling while in the process of crushing multiple pieces of gravel and cobble particles at the same time. Per the Report, soils with gravel percentages of 93 percent have been identified under Ischia Creek. This high percentage of gravel leads to a greater stalling risk for the proposed crossing. The risk associated with stalling of the MTBM includes the potential need to back out the MTBM machine and inability to support the surrounding ground as the pipe string and MTBM are removed from the ground. In soils with a high percentage of gravels and cobbles, the lack of a supporting presence to the surrounding soils leads to collapse of the overlying materials and increased potential for sinkhole and subsidence development. The removal of the pipe string and MTBM to clear a blockage also increases the abrasion that will occur on the product pipe s protective coatings, increasing the risk of damage as the pipe is forced to travel an additional length through the ground. D. Nested Cobbles Would Likely be Encountered During the Direct Pipe Installation, Which Have the Potential to Require Significant Excavation Along the Pipeline Alignment if Unable to be Cleared Page 4 of 6 While cobbles were not sampled during the geotechnical investigations due to size restrictions of the standard penetration test sampler, cobbles are inferred to exist since this area is in the Allegheny Plateau of New York, which was heavily glaciated during the Pleistocene Era. Known large cobbles exist in this area developed during that Era and should be expected along the drill path alignment. While cobbles on their own do not pose a significant risk to a Direct Pipe installation, where multiple cobbles exist (known as nested cobbles ), the MTBM is likely to experience great difficulty advancing forward through these materials. When the machine is not capable of excavating through the nested cobble zone, a rescue pit is needed to be excavated down to the front of the machine to clear the obstruction. Excavation requires direct access along the alignment. An obstruction could be encountered anywhere along the drill path, including in a wetland or stream, thus leading to significant potential resource impacts if excavation in these areas becomes necessary. The excavation area would need to be large enough to unearth the MBTM and free and provide ingress/egress for the required machinery. While pulling back from the excavation face with the MTBM can be attempted to dislodge the obstruction, this may not be able

5 to clear the obstruction. In addition, attempting to pull back from the excavation face may result in collapse of the overlying ground materials increasing settlement, subsidence, and sinkhole risks. E. Boulders and Cobbles Encountered During Pipe Have the Potential to Cause Significant Over Excavation and Associated Risks The ability to break down large boulders is highly dependent upon the type of cutters incorporated into the cutter wheel and the ability of the soil mass to hold/grip the boulder in place to allow the cutters to break down the larger particle into smaller pieces. If the soil mass does not have sufficient strength to keep the boulder in place, the boulder will tend to be pushed in front of the MBTM. This can lead to serious issues associated with over excavation, significant line and grade deviations and the requirement for a rescue shaft to break up the boulder. If the cobble or boulder were to fall out of the excavation face and accumulate on the bottom of the cutter wheel, the machine may try to ride up on top of the object causing significant deflections. These deflections can increase the risk of over bending the pipe during an installation. In terms of strength, MTBMs are reportedly capable of crushing materials with unconfined compressive strengths up to 200 MPa (30,000 psi). However, large quantities of materials with strengths above 130 MPa (20,000 psi) can significantly damage the cutters, cutter wheel, and/or crushing cone. Furthermore, in the event the MBTM is unable to excavate through a nested cobble zone or boulder, the excavation of a rescue pit would be needed down to the front of the machine in order to clear the obstruction. This requires a significant excavation from the surface to provide direct access along the drill alignment, so as to reach machine depth. While pulling back from the excavation face with the MTBM may be possible to dislodge the obstruction, it may not clear the object resisting forward progress. As noted above, attempting to pull back from the excavation face has the potential to result in collapse of the overlying ground materials, increasing settlement risks along the entire bore path. Given that the Ischua Creek crossing is in very close proximity to a USDA Conservation Easement, National Fuel has inquired about entry and surface disturbance inside of the easement. However, National Fuel has been advised that no entry or surface disturbance is permitted. F. Mixed-face Conditions Pose Significant Risks to a Direct Pipe installation. The term mixed-face condition refers to a mixture of either boulders and other soil constituents or bedrock and other soil constituents. Mixed-face conditions require the use of MTBMs equipped with appropriate cutters consisting of a mixture of disc cutters and soil tooling. As stated earlier, the requirement for disc cutters is limited to installations of 42 inches and larger. Page 5 of 6 If a MTBM encounters a mixed-face condition, over-excavation of the softer soils can occur as the MTBM slowly breaks down a larger sized particle or bedrock materials. The over-excavation of softer materials can lead to the development of sinkholes and large surface settlements. Thus, Direct Pipe installations should never be used at the interface of soil and bedrock, such as the mixed-face condition of soil and bedrock materials which may exist on the north side of the Ischua Creek crossing.

6 III. CONCLUSION In summary, it is Mott MacDonald s opinion that significant geotechnical risks exist for a Direct Pipe crossing of Ischua Creek associated with the high percentage of coarse grained gravels and cobbles observed at various depths beneath the ground surface on the south side of the crossing, potential for mixed-face conditions, and the inability to excavate the ground materials with a 24-inch installation. Due to these risks, a Direct Pipe crossing of Ischua Creek is deemed to carry a significant to extreme risk of failure. Regards, Glenn Duyvestyn Vice President T (330) C (216) glenn.duyvestyn@mottmac.com Page 6 of 6

GEOTECHNICAL BASELINE REPORTS APPLYING THE GUIDELINES TO MICROTUNNELING

GEOTECHNICAL BASELINE REPORTS APPLYING THE GUIDELINES TO MICROTUNNELING The North American Society (NASTT) and the International Society for Trenchless Technology (ISTT) International No-Dig Show 2009 Toronto, Ontario Canada March 29 April 3, 2009 Paper A-2-04 GEOTECHNICAL