Edge Cable Holdings USA, LLC, a subsidiary of Facebook, informed the public on Oct. 27 of surveys that will be administered during the month of November to support the installation of a subsurface steel bore pipe from a residential lot in Tierra Del Mar to a point offshore. The bore pipe is part of the Jupiter Cable System. Edge Cable has contracted with SubCom, LLC to conduct the work.
“On Nov. 9-10, an electrical resistivity tomography (ERT) survey will be undertaken in a 335-foot by 65-foot survey area located on the beach adjacent to Lot 3200,” Edge Cable announced in the update. “ERT is a non-invasive survey method that generated a subsurface electrical current and measures the electric potential differences between a series of dispersed electrodes.”
The ERT survey work will take place Nov. 9-10 from 8 a.m. to 5 p.m. Pacific.
A subsurface bore sampling survey will also be performed in January 2021 during approved construction hours to collect data on the subsurface soil strength. A soil core will be extracted using a utility truck with geotechnical sample equipment mounted at the rear of the vehicle.
The offshore, marine vessel-based acoustic reflection survey will take place Nov. 7-8 if the weather conditions are favorable. A vessel conducting this work may be seen offshore near Tierra del Mar. Edge worked with the U.S. Army Corps of Engineers regarding this survey.
Facebook said they estimate that all the beach survey work will take place over approximately five days, with work only occurring between 8 a.m. to 5 p.m. Monday to Friday.
“The purpose of the surveys is to identify the sub-bottom profile below the survey area,” Facebook said in an email to the Headlight Herald. “The results of the surveys will give Edge and SubCom a better understanding of the underlying geology. More specifically, the surveys will help to identify unfavorable sediment layers for HDD drilling operations (e.g., rock, boulders, and/or interchanging soils) and allow the project’s HDD engineers to adjust the proposed drill plan, if necessary.”
Edge Cable said public access around the survey zone would be maintained throughout the surveys. During work hours, the survey area will be signposted, notifying the public of the work. The area will be roped off to limit access. A flagger will be onsite to ensure the public avoids the roped-off area.
The Oregon Department of State Lands (DSL) also notified Facebook in a letter on Oct. 16 of issues in their independent hazard analysis, prepared by ERM, that require correction, clarification or additional evaluation and information. DSL asked the Oregon Department of Geology and Mineral Industries (DOGAMI) and the Department of Environmental Quality (DEQ) to review the hazard analysis.
DEQ seeks additional information regarding the drilling mud and asks for the confidence level that the mud has hardened and how long it would have taken for the material to harden. DOGAMI has identified geologic hazards not addressed in the hazard analysis.
Facebook is required to address the issues or indicate how they will be addressed by Nov. 2.