Direct Pipe ®

Direct Pipe® _{is a trenchless method that combines advantages of the established pipeline installation}

methods of microtunnelling and HDD. A single continuous working operation allows the trenchless installation of pre-fabricated pipeline and the simultaneous development of the required bore hole. Earth excavation is performed with a microtunnelling machine (equipped with a cutterhead) which is navigable and uses a flushing circuit (pipes) method to transport earthen materials to the surface. Modern and proven controlled pipe jacking techniques ensure accurate measurement of the current pipe position along the intended route. The axial force that is necessary for the boring process is transferred along the installed pipeline from the pipe thruster or hydraulic jacking system at entry of the cutterhead.

Direct Pipe® _{installations may be much shorter and shallower than HDD installations because the}

excavation is continuously cased, reducing the risk of hole collapse and subsequent settlement. Additionally, the external fluid pressures of the excavation slurry system and bentonite lubrication system are much lower than a typical HDD, thereby reducing the relative risk of hydraulic fracture and inadvertent returns. The length limitation for the Direct Pipe® _{technology (for a 30-inch pipe) is}

approximately 900 feet due to the requirements of the hydraulic motors in the smaller diameter tunneling machines. Soils with abundant, strong, and/or abrasive boulders or other large obstructions present risk to the Direct Pipe®_method.

Direct Pipe®_{can be more sensitive to soil conditions than HDD, as the cutterhead cannot tunnel through}

rocky substrate. Direct Pipe® _{also requires construction personnel to periodically enter the pipe to}

monitor and adjust settings underground. This presents additional safety risks, and requires a specialized team of individuals to always be on-site in the event that an incident occurs. While Direct Pipe®_{has been}

used overseas, this trenchless installation method is relatively new to the U.S. Also, Direct Pipe® _is

typically used for much larger diameter facilities, (42-inches and larger). The equipment associated with this method has undergone recent modification to allow for smaller diameters drills (30-inches or less) but this diameter is not common with use of the majority of Direct Pipe®_{applications. Tennessee has not}

identified any areas where Direct Pipe® _{will be utilized; however, Tennessee continues to evaluate}

geotechnical information to determine the feasibility of using the Direct Pipe® _method.

1.3.2.6

Rock Removal

Rock encountered during trenching will be removed using one of the techniques detailed below. Techniques include:

x Conventional excavation with a backhoe;

x Ripping with a bulldozer followed by backhoe excavation;

x Hammering with a pointed backhoe attachment or a pneumatic rock hammer, followed by backhoe excavation;

x Blasting followed by backhoe excavation; or

x Blasting surface rock prior to excavation.

While some of this rock may be rippable by conventional excavation equipment, some of it may require blasting. All blasting activity will be performed according to strict guidelines designed to control energy release. Proper safeguards will be taken to protect personnel and property in the area. Resource Report 6 of this ER contains details relative to blasting. Methods will be employed to prevent the scattering of

Environmental Report Northeast Energy Direct Project Resource Report 1 General Project Description

1-90 rock and debris. Tennessee will attempt to avoid all karst areas during the routing and construction phases of the Project. The Project-specific ECPs includes for preserving karst geology in the event they are encountered. Tennessee will strictly adhere to all local, state, and federal regulations applicable to controlled-blasting and blast vibration limits with regard to structures and underground utilities while performing these activities. Special care will be taken to monitor and assess blasting within 200 feet of dwellings and private or public water supply wells.

Tennessee has developed a Project-specific Blasting Management Plan for the Project that establishes procedures and safety measures that Tennessee’s Contractor will be required to adhere to while implementing blasting activities along the pipeline ROW during the Project. Tennessee will also obtain all the necessary federal, state, or local blasting permits prior to construction. Tennessee’s construction contractor will be required to submit a detailed Blasting Specification P lan to Tennessee that is consistent with the provisions of the Blasting Plan and Kinder Morgan Construction Specifications. The construction contractor's plan, when approved by Tennessee, will be incorporated into the construction contractor's scope of work. Tennessee’s Blasting Plan will be provided in Tennessee’s Project-specific ECPs for each state in Volume II, Appendices J, K, L, M, and N for each state.

Excess rock is defined as all rock that cannot be returned to the existing rock profile in the trench or graded cuts or is not needed to restore the ROW surface to a condition comparable to that found adjacent to the ROW. Excess rock will be hauled off the ROW and disposed of at an approved landfill or recycling facility unless approved for use as slope stabilization, windrowing, or some other use on the construction work areas as approved by the landowner or land managing agency.

1.3.2.7

Wetland Crossing Construction

Wetland locations along the pipeline segments are described in Resource Report 2 and shown on the aerial alignment sheets included in Volume II, Appendix F. Site-specific wetland plans will be provided in a the final ER. Pipeline construction across wetlands will be performed in accordance with Tennessee’s Project-specific ECPs for each state. Tennessee is evaluating additional locations for proposed HDD crossings, some of which may be used to cross wetland areas. Final decisions on which wetlands will be traversed using HDDs will have to made once all access to the ROW has been obtained. Limited landowner access has hindered Tennessee’s ability to assess large wetland areas for HDD installation.

Tennessee will utilize one of the following methods for installing the pipeline within wetlands during construction. The construction methods include:

x Standard pipeline; x Conventional wetland; x Conventional bore; x Direct Pipe®_; x HDD; and x Push-pull technique.

These wetland crossing techniques are described in detail in Resource Report 2. Crossing methods are provided in Resource Report 2 and typical drawings depicting these construction methods are provided in Volume II, Appendix G. The wetland impact summary tables are located in Resource Report 2.