AGDC’s continued responses to FERC cover Cook Inlet crossing, health impacts
In filings with the Federal Energy Regulatory Commission last month, Alaska Gasline Development Corp. provided further details of its plan to tunnel and/or trench the buried pipeline from the west side of Cook Inlet.
The plan is to tunnel far enough out in the water so that the pipe-laying barge could take over and set the concrete-coated pipeline on the seafloor to reach the other side, where trenching and/or tunneling would resume to bring the pipe ashore at Nikiski.
AGDC said it prefers open-cut trenching for pipeline installation in the transition zones on both sides of Cook Inlet but could change the plan to tunneling as it learns more during the project’s detailed engineering stage.
In its data request to AGDC, federal regulators noted that the project did not conduct geotechnical soil borings in the full transition zone on either side of Cook Inlet, limiting the data available to decide between tunneling and open-cut trenching.
The pipeline would be buried with a minimum soil cover of three feet in the shoreline approach up to a water depth of 12 feet below mean lower low water (the average height of the lowest tide).
In deeper water, where the pipeline is on the seafloor with no soil cover, AGDC said the 3.5 inches of concrete coating would protect the steel pipe from any damage from fishing gear, anchors or boulders.
“The pipeline is safe without burial,” AGDC said.
Separate from the FERC-led EIS, approval of the pipeline construction plan across Cook Inlet will be up to the U.S. Pipeline and Hazardous Materials Safety Administration and its regulations.
Health impact assessment is wide ranging
AGDC on Nov. 19 provided federal regulators with the project’s health impact assessment, which looks at how construction and operations could affect the health of Alaskans — including subsistence lifestyle and food nutrition. The filing is 170 pages long.
“The presence of outside workers could exacerbate social problems or stress and impact mental health … particularly in smaller communities,” the assessment said.
“Households impacted would be expected to adapt with some difficulty but could maintain pre-impact level of health with support from community, regionally based and existing federal support of Native health, public health programs. … Potential construction impacts to subsistence during the construction phase are expected to be temporary in duration,” the assessment said.
“Potential concern related to subsistence resources during construction is the possibility that workers might compete with subsistence users resulting in either diminished harvests or greater subsistence effort. The project will prohibit workers from hunting or fishing while on the job or when company transportation has been used to bring them to a remote site.”
The assessment’s subsistence section also raised the issue of invasive species.
“The introduction of invasive species (both fish and/or aquatic plants) could impact fish habitat and/or productivity and impact fish availability to subsistence users. … The introduction of invasive species could become a long-term impact if their spread is uncontrolled, thus potentially signaling a long term reduced fish availability for subsistence users and users downstream of the impacted areas.”
In another section, the assessment said Railbelt and highway communities “would be expected to be impacted by the increase in traffic during construction, which could cause mental stress and anxiety regarding the real or perceived issues of safety and environmental health associated with the increased rail and truck traffic.”
Though it added, “Employment opportunities could alleviate family stress by improving family income, and the local economy during construction.”
And the assessment noted that local fire departments and emergency medical service squads could see higher call volume during construction, while also facing the potential loss of staff and volunteers moving to Alaska LNG project construction jobs. Payments to municipalities under the project’s proposed impact aid grant program could help cover any added costs, AGDC told federal regulators. However, the project has yet to negotiate an impact aid program with the state and affected municipalities.
AGDC’s November filings with FERC covered multiple other issues, including:
• AGDC defended its plan to use gravel fill for work areas in wetlands during construction. In answer to questions from FERC, the state team said timber mats, wood chips or protective mats made of composite material would be too costly and impractical to deploy during construction.
Wood or composite mats would cost two to four times as much as gravel fill, AGDC said.
• “Typically, gravel fill would be placed as a protective cover over thaw-sensitive areas along the right-of-way during construction and would not be removed during restoration because it would be difficult to avoid disrupting the thermal regime of adjacent, undisturbed areas,” AGDC reported to FERC.
• The project’s gravel sourcing and reclamation plan covers development of new sources of sand, gravel and fill for construction, along with plans to store or dispose of unsuitable materials that would be removed from the site such as unusable topsoil, overburden or frost-susceptible material.
• A revised table lists locations of potential deep and shallow landslides, slope creep, rock falls, rock avalanches, debris flows and snow avalanches based on the project’s recently updated onshore geohazard assessment methodology and results summary.
• “If warming continues for the next 30 years, it could change local permafrost and groundwater conditions sufficiently to result in mechanically weaker soils,” AGDC told FERC.
“In these areas, significant precipitation events as well as earthquakes might have substantial impact on soil stability and, thus, pipeline integrity.”
The state team was responding to FERC’s Oct. 2 comment that “AGDC’s proposed mitigation for soil liquefaction … and does not take into account areas that could become prone to liquefaction due to climate change and permafrost degradation.”
The project responded that it would monitor and “apply mitigation techniques to minimize potential impacts from permafrost degradation along the pipeline.”
• “It is unlikely permafrost would be thermally affected” by blasting for pipeline trenching, AGDC said. “Blasted trench areas are easily controlled to limit the disturbed materials to within the frozen trench walls and accordingly would not result in a shift in soil makeup and the permafrost profile.”
• Thaw-sensitive soils cover a total of about 500 miles of the main pipeline route from Prudhoe Bay to Nikiski and the line from Point Thomson to Prudhoe.
• Traffic on a 5-mile stretch of the Parks Highway outside the Denali National Park and Preserve would be limited to one lane September through May during pipeline construction, with brief closures (“hours, not days”) of both lanes. “Construction within this window would coincide with the off-season for tourism.” The project would try to limit the complete shutdowns to evening hours.
• AGDC presented its plans to monitor commercial, domestic and public-supply water wells within 150 feet of the project — most of those wells are near the LNG plant site. The state team said it would test public water wells before and after construction to determine if the work affected the wells. Private wells would be tested at the landowners’ request.
• Pile driving would occur 12 hours a day, 7 days a week at the LNG plant construction site, while pile driving at the compressor station and heater station construction sites along the pipeline route would occur 24 hours per day.
Dredging for the marine offloading terminal at the Nikiski site would occur 24 hours a day, 7 days a week.
Larry Persily is a former Alaska journalist, state and federal official who has long tracked oil and gas markets and projects worldwide.