SIERRA VISTA — The U.S. Army Corps of Engineers wasted no time in awarding contracts for construction of the border wall following Friday’s ruling by the Supreme Court of the United States allowing the Trump administration to use Department of Defense (DOD) dollars to partially fund its construction.
Acting Defense Secretary Patrick Shanahan approved the transfer of $1.5 billion from the department to build more than 80 miles of barriers on the border, according to a press release. The ruling allows up to $2.5 billion to be allocated.
COE awarded the New Mexico firm Southwest Valley Constructors a $646 million contract to design and build the Tucson Sector barrier replacement project to be completed by January 31, 2020.
This includes the section across the San Pedro River at the border with Mexico. It is within the San Pedro Riparian National Conservation Area (SPRNCA), the 57,000-acre home to unique, threatened and endangered wildlife managed by the U.S. Bureau of Land Management (BLM).
BLM Gila District manager Scott Feldhausen sent an eight–page list of comments and recommendations to Paul Enriquez, U.S. Customs and Border Protection (CBP) border wall program manager, on July 3 to address concerns with the 0.2–mile segment of proposed border barrier within the SPRNCA, as well as lands east of Douglas to the state line with New Mexico.
No design or construction plans for the proposed border wall have been shared with the BLM, so his letter contained a generalization of probable and possible impacts from alteration of the river’s hydrology as a result of the replacement of the existing vehicle barrier with a new pedestrian barrier.
“The BLM has a history of cooperation and coordination with (CBP) to solve resource-related issues associated with tactical infrastructure development on public lands along the US–Mexico border,” Feldhausen said. “Our combined efforts serve to protect these resources as we focus on reducing resource damage from the impacts of illegal border crossings.”
He pointed out the BLM manages the SPRNCA as specified by the U.S. Congress to conserve, protect and enhance the riparian area. In addition to providing recreational opportunities to the visiting public, the uncommon ecological landscape provides home to over 250 migratory bird species, 10 species listed under the Endangered Species Act as either Threatened or Endangered, 12 BLM sensitive species and 28 species of Greatest Conservation Need.
He and staff determined there “could be reduced passage of sediment and debris through ephemeral drainage paths during seasonal flood flows with the proposed pedestrian fence. Currently, seasonal removal of the Normandy-style vehicular barriers has allowed the San Pedro River to maintain natural processes.”
Water and sediment south of the barrier “could contribute to channel incision and increased erosion,” he continued. “These hydrological changes may impact the functionality of the riparian area, associated species and roads or trails adjacent to the river and downstream from the project. We anticipate that installation across the San Pedro River of a typical 18 — 30’ border barrier design could accumulate a significantly greater amount of sediment and debris than what is normally found in ephemeral drainages.”
Flood flows have high velocities and shear stresses which can remove riparian vegetation and destabilize banks, he noted.
“This extreme flow regime, coupled with the seasonal variability associated with the summer monsoons, make installation of a permanent, yet permeable, barrier an engineering challenge. Any associated changes in floodplain function could lead to reduced channel function through the redirection of flood energies,” according to Feldhausen.
He recommends the SPRNCA border barrier crossing be designed to handle large amounts of sediment and debris to minimize channel incision and erosion, which would hinder surface and subsurface river flows.
U.S. Fish and Wildlife Service’s Information for Planning and Consultation database identified 21 threatened and endangered species have the potential to exist within the project area. Five of these potential occurrences warrant additional attention. Jaguar, ocelot, Mexican wolf, Mexican long–nosed bat and Mexican spotted owl may be impacted by lighting and/or physical barrier construction. Impermeable barriers may block corridors of movement for these species.
“The BLM recognizes that sediment and debris could begin to build up at an increased rate in low-water crossings during high flow events, causing backflow and erosion that could impact both natural resources and the border barrier itself,” Feldhausen wrote. “Current vehicle barriers in low water crossings along the 20–mile stretch in Cochise County proposed for new construction have already shown build up.”
He also recommended the CBP design the fence appropriately to counter impediments to proper hydrologic discharge across low–water crossings, while still providing connectivity to the sky island archipelago to the north, a valuable habitat for many species.
Surface–disturbing fence construction activities should be confined to the Roosevelt Reservation, the 60–foot buffer between the U.S. and border, to the “greatest extent practicable.” Periodic monitoring of the project area should be conducted.
Feldhausen addressed road impacts and requested no work be done to improve primitive roads. He suggested construction should “incorporate periods of inactivity” during the monsoon season from mid–July through mid–September to prevent damage.
“We appreciate the opportunity to coordinate with CBP on the proposed installation of new barriers on BLM–managed public lands in Southern Arizona that will reduce damage from illegal border crossings over important natural and cultural resources,” he concluded. “Advance coordination on actions will help facilitate CBP and BLM responsibilities for open, continuous and ongoing consultation.”