Dominion Pipeline Monitoring Coalition (DPMC) has posted two reports on their Web page that substantiate the dramatically increased probability of precipitation-induced landslides following the extensive excavation associated with construction of the proposed ACP and its related access roads. DPMC says that, “Much of the proposed ACP corridor route and related infrastructure, including access roads, is on slopes greater that 40%, with segments exceeding 58%” – including numerous areas in Nelson County.
The Proposed Atlantic Coast Pipeline Route through Little Valley in Bath County, Virginia: An Assessment of Landslide Risk and Slope Stability Factors, prepared by Malcolm G. Cameron, Jr., Coordinator of Geohazards Analysis, Dominion Pipeline Monitoring Coalition. This report, submitted to FERC by DPMC, notes the presence of several landslides on both sides of the valley resulting from a heavy rain event in July 2015, ranging in size from small slumps along ravines up to a one-quarter-acre rotational slide that traveled over 450 feet down the upper east slope of Little Mountain. “With slopes averaging 30 to 55 percent and up to over 80 percent combined with unstable soils, any construction involves a high risk of landslides during heavy rainfall events.”
The report also notes that map sheets submitted to FERC by Dominion in August 2, 2016, reveal “a cursory and incomplete documentation of geologic hazards related to slope steepness, bedrock type, and groundwater conditions in the Little Valley area,” and did not identify existing landslides documented in the DPMC report.
The Little Valley/Bath County report “concludes that mitigation efforts by Dominion to avoid slope failures will be difficult or impossible to accomplish in steep mountain areas along the ACP pipeline route. To date, there is no indication that site-specific investigation of landslide risk and development of mitigation or risk-avoidance plans will be completed and made available on a schedule that allows informed agency and public review and comment prior to permitting and construction.”
Landslide Analysis, Monongahela National Forest Flood Event (June 2016), prepared by the USDA Forest Service, Monongahela National Forest. The report analyses 48 landslides that occurred during the flood event of June 23, 2016 in areas with soils, geologies, and slopes of all slope classes similar to the proposed route of the ACP corridor on the Monongahela National Forest. Report conclusions:
- Flooding and landslides related to storm events are common in the Central Appalachian region, and the June 2016 event should not be considered unusual.
- Even more stable land forms and geologies are susceptible to landslides under the right conditions (amount and intensity of precipitation).
- Disturbed soils can be highly susceptible to mass movement resulting in landslides.
- Forest Service standards and guidelines must be followed when operating on steep slopes and soils that are susceptible to slides.