Southeast Market Pipelines Project Final Environmental Impact Statement

3.0 ENVIRONMENTAL ANALYSIS This analysis describes the existing natural and human environment and the potential impacts on it resulting from construction and operation of the SMP Project. In the following discussion, we address geology, soils, groundwater, surface water, wetlands, vegetation, fisheries, wildlife, special status species, land use, cultural resources, air quality, and noise, as well as reliability and safety. This analysis also addresses cumulative impacts that may result when the SMP Project’s impacts are added to the impacts of present and reasonable foreseeable future projects. Generally, our analysis identifies and describes the existing conditions of the environmental resources potentially affected by the SMP Project and, as necessary, further describes resources unique to the SMP Project components. As described in greater detail below, our independent assessment of potential impacts on these resources, including the Applicants’ efforts to avoid, minimize, and mitigate these impacts, are then described. As appropriate, we recommend measures that, if implemented, would further avoid, minimize, and mitigate potential impacts on the environment. Our recommendations appear in this analysis as boldface, bulleted, and indented text. These recommendations are also presented in section 5.0. Our resource-specific analysis concludes with a determination of significance. We consider an impact to be significant when it results in a substantial adverse change to the environment. This analysis typically describes temporary, short-term, long-term, and permanent impacts. A temporary impact generally occurs during construction with the resource returning to preconstruction condition immediately after restoration or within a few months. A short-term impact could continue for up to 3 years following construction. Long-term impacts would last more than 3 years, but the affected resource would eventually recover to pre-construction conditions. A permanent impact would result from an activity that modifies a resource to the extent that it would not return to preconstruction conditions. As appropriate, our analysis also addresses direct and indirect effects and primary and secondary impacts. The conclusions in this EIS are based on the Applicants’ compliance with all applicable laws and regulations, the construction and operation of the proposed facilities as described in the Applicants’ applications and summarized herein, and the implementation of our recommendations. 3.1 GEOLOGY 3.1.1 Regional Geology and Physiography The SMP Project would be located within two physiographic provinces: the Piedmont Province in east-central Alabama; and the Coastal Plain Province in southern Alabama, Georgia, and Florida. More specifically, Transco’s Verbena, Proctor Creek, Hissop, and Alexander City Loops, and Sabal Trail’s Mainline pipeline from approximate MPs 0 to 55 would be located in the Piedmont Province, and the remainder of the SMP Project would be located in the Coastal Plain Province. As discussed in section 3.1.2.3, the SMP Project would also traverse some of the more ecologically unique karst terrain within the United States in southwest Georgia and northwest Florida. Aboveground facilities would be constructed within the same geologic setting as the adjacent pipeline facilities and, therefore, are not considered separately in the remainder of section 3.1 except where noted. The two provinces have uniquely contrasting characteristics (topography, physiography, and geology) that are separated by the Fall Line, a geologic escarpment where the igneous and metamorphic bedrock of the Piedmont Province meets with the south-southeastwardly deposited wedge of sediments of the Coastal Plain Province in the eastern United States. In general, the Piedmont Province in east-central Alabama has higher elevations and greater relief hills and mountains; western Alabama and southwest 3-1 Environmental Analysis Georgia have lower elevation and moderate to high relief hills; and Florida has significantly lower and subdued rolling hills to flat plains. Neilson (2013) notes that there is a visible change in slope along the Fall Line with the Piedmont Province being 150 to 200 feet higher than the Coastal Plain Province. The geologic structure of the Piedmont Province is described by the USGS (1990) and Neilson (2013) as having developed along northeast to southwest trending belts of deformed Precambrian to Paleozoic age (around 1.0 billion to about 300 million years in age) metamorphic rocks that have been intruded by younger, small to large bodies of igneous diabase. The most common rock types are slate, phyllite, marble, quartzite, greenstone, schist, amphibolites, and gneiss. The Piedmont Province is generally a plateau that slopes from elevations above 1,000 feet in the north to 500 feet in the south. The northern district of the Piedmont Province is generally more rugged while the southern district becomes flatter, and rivers have cut valleys up to 200 feet deep in to the plateau. The Coastal Plain Province developed during the middle Mesozoic through the Cenozoic Era (from about 140 million years ago to the present) time period and is described by the USGS (1990), Neilson (2013), and Frazier (2007) as consisting of poorly consolidated chalk, sandstone, limestone and claystone bedrock, and unconsolidated gravels, sands, silts and clays. The oldest deposits are near the Fall Line and are covered by increasingly younger layers to the south and east. During all of Late Cretaceous and early Palaeogene Periods (from about 140 million years ago to 60 million years ago), portions of Florida, southern Georgia, and Alabama were a marine platform mostly covered by shallow seas with small, scattered, low islands. The sediments that accumulated in those shallow waters are comprised of the skeletons of billions of microscopic, single-cell organisms called foraminifera. When they solidified, they formed carbonate rocks including limestone and dolomite. Subsequent sea level fluctuations resulted in the deposition of alternating marine and non-marine deposits in the Coastal Plain Province. The Pleistocene Epoch (2.6 million to 10,000 years ago), also known as the Ice Age, was characterized by extreme climate and sea level change. During warm periods, sea levels rose as much as 100 feet higher than today and allowed re-accumulation of limestone. During glacial periods seas dropped as much as 300 feet. Sea level reached its current elevation within the last several thousand years. 3.1.2 Local Geology 3.1.2.1 Surficial Geology Various geologic deposits are located within trench depth along the SMP Project pipeline routes, including unconsolidated material, metamorphic and igneous bedrock units, and sedimentary bedrock units (see table 3.1.2-1 in appendix D). The occurrence of karst geology is an important consideration for the Sabal Trail Project and, to a substantially less degree the FSC Project, and is discussed separately in section 3.1.2.3. In general, Transco’s proposed Rock Springs, Butler, Billingsley, and Autauga Loops would cross poorly consolidated sedimentary rocks of the Coastal Plain Province, and the Verbena, Proctor Creek, Hissop, and Alexander City Loops would cross metamorphic and igneous rocks of the Piedmont Province. The loops and associated aboveground facilities would be located in or on unconsolidated deposits where bedrock is not present at the surface or within trench depth. Sabal Trail’s Mainline would cross metamorphic and igneous rocks of the Piedmont Province between approximate MPs 0 and 55 in Alabama; the remainder of the Sabal Trail Project facilities would be underlain by sedimentary rocks and limestone of the Coastal Plain Province. The facilities would be Geology 3-2 located in or on unconsolidated deposits where bedrock is not present at the surface or within trench depth. The FSC Project is underlain by 30 to 200 feet of unconsolidated deposits; therefore, installation of the FSC Project, including all of FSC’s proposed HDDs, would not encounter bedrock. Construction and operation of the SMP Project would not materially alter the geologic conditions in the project area. Effects from construction could include disturbance of the natural topography along the pipeline rights-of-way or adjacent aboveground facilities due to trenching, blasting, and grading activities. Following construction, the Applicants would restore all areas as close as practicable to their preconstruction contours. 3.1.2.2 Blasting Blasting would be required to excavate the pipeline trench in areas where bedrock could not be removed by other mechanical means (e.g., rock trenchers, rock saws, jack hammers). Hard bedrock occurs near the surface along about 10.1 miles (23 percent) of the 43.5-mile-long pipeline loops in Alabama although, based on previous construction in these areas, Transco expects that blasting would not actually be necessary in the majority of these areas. Transco identified 1.6 miles of hard bedrock outcrops in the Piedmont Province along the Proctor Creek, Hissop, and Alexander City Loops where blasting would likely be required. Sabal Trail estimates that blasting may be required along about 13.9 miles (16 percent) of the Mainline route in Alabama and along about 12.7 miles (8 percent) of the Mainline route in Georgia. Sabal Trail does not expect blasting to be required south of Mainline MP 100. FSC does not anticipate the need to conduct blasting for construction of the FSC Project but, if necessary, blasting would be conducted in

Load more