19 Feb 2025

The Geophysical Survey of Mare Island Naval Cemetery, California

Abstract: The US Congress codified the National Historic Preservation Act of 1966 (NHPA), the nation’s most effective cultural resources legislation to date, mostly through establishing the National Register of Historic Places (NRHP). The NHPA requires federal agencies to address their cultural resources, which are defined as any prehistoric or historic district, site, building, structure, or object. Section 110 of the NHPA requires federal agencies to inventory and evaluate their cultural resources, and Section 106 requires them to determine the effect of federal undertakings on those potentially eligible for the NRHP. This project was undertaken to provide the US Department of Veterans Affairs (VA), National Cemetery Administration (NCA), with a geophysical survey of Mare Island Naval Cemetery. The approximately 2.5-acre cemetery is located in Vallejo, California, and contains more than 900 burials. Mare Island Naval Cemetery is part of the Mare Island Naval Shipyard Historic District, which was listed concurrently on the National Register of Historic Places and as a national historic landmark in 1975.

9 Oct 2024

Performance of High-Resolution, Acoustic Mapping Systems in a Fluid-Mud Environment : Testing the Effectiveness and Viability of High-Resolution, Hydrographic Survey Systems in a Fluid-Mud Environment

Abstract: This study explores the use of high-resolution acoustic mapping systems to penetrate fluid-mud layers by quantitatively relating depth with operating frequency. Prior to this study, multibeam surveys have proven be an effective method to elucidate the seafloor and collect bathymetric data on various bodies of water including rivers, lakes, bays, and the oceans. These techniques are regularly used on US Army Corps of Engineers dredged and federally maintained navigation channels. The objective of the study was to test the effectiveness of commercial off-the-shelf, low-frequency, high-resolution acoustic survey systems to penetrate fluid mud and if so, determine the density at penetration. The testing method combined multibeam echosounder, sub-bottom profiler, and single-beam echo sounder. In addition, in situ testing was conducted to determine the density of fluid-mud layers using a RheoTune profiler and laboratory testing. Results indicate that the use of currently available, bathymetric mapping systems operating at 90 kHz and higher are incapable of penetrating fluid mud in riverine and coastal shallow water conditions. This study demonstrates that while multibeam technology is effective at penetrating the water column, current frequencies available on the market are unable to penetrate fluid-mud layers in a riverine and shallow-water environment.

6 Sep 2024

Use of Chirp Sub-Bottom Acoustics to Assess Integrity of Water-Control Structures: Inner Harbor Navigation Canal Lock, New Orleans

Abstract: The US Army Corps of Engineers (USACE)-maintained lock on the Inner Harbor Navigation Canal serves as a critical navigation link between Lake Pontchartrain to the north and the Mississippi River to the south. Extensive slumping has been observed on the earthen embankment on each side of the lock, suggesting that internal pathways for water to escape through the lock’s concrete walls or joints are present. Unfortunately, traditional methods often used to identify cracks in the concrete (e.g., sidescan sonar) or water-filled voids under or behind the structure (e.g., ground-penetrating radar) did not identify any structural issues at this site. Prior to dewatering and repair, the USACE New Orleans District requested that the US Army Engineer Research and Development Center conduct a sub-bottom survey at the lock in order to identify water-filled voids and better prepare for potential repairs during dewatering. A unique sled was constructed that allowed a small vessel to tow the sub-bottom profiler at an angle to direct more acoustic energy into the structure. Low frequency, chirp acoustic energy successfully penetrated the concrete walls and identified several water-filled voids on both sides of the lock. A later post-dewatering walk-through indicated that the chirp imaged voids spatially adjacent to cracks, and cracks were not found in any other locations. Additional work is needed to further develop this methodology in other USACE structures.

19 Jul 2024

Permafrost and Groundwater Characterization at the Proximity of the Landfill, Fort Wainwright, Alaska

Abstract: This report summarizes a site investigation at the vicinity of the landfill, a discontinuous permafrost site, at Fort Wainwright, Alaska. The objective of this effort was to characterize the permafrost extent and groundwater flow at the study area, and to compare newly collected subsurface characteristics with historical datasets. The main tasks for this effort included lidar and remote sensing analyses, geophysical investigations, a tracer dye study, contaminant trend analysis, and installation of soil temperature sensors. Findings included changes in stream channels and watershed boundaries, and elevation losses (0.2 m to 1 m) east and northeast of the landfill. From frost probe measurements, we found that depths to permafrost were up to 1.5 m deeper in 2021 than in 2010 where the difference in depth ranged from 20% to more than 350%. Furthermore, we detected a reduction in lateral permafrost extent from geophysical datasets. The groundwater flow direction, as detected through the dye study, was south to southwest. Dye was detected up to 2,300 m from the injection point. Groundwater travel times, as calculated from the dye study, varied greatly. For upcoming historical comparisons, it is recommended that data collections are performed using similar methods as described in this study.

20 Mar 2023

Old River Control Complex (ORCC) Low Sill: A Literature Synthesis

Abstract: The US Army Corps of Engineers (USACE), New Orleans District (MVN), tasked the US Army Engineer and Research Development Center (ERDC) with assessing the condition of a grouted scour hole located at the southeast wall of the Old River Low Sill Structure (ORLSS) at the Old River Control Complex (ORCC) using noninvasive techniques, such as geophysical surveys and physical models. This special report (SR) combines a scientific literature synthesis of previous research with further geologic interpretation as a first step in the overall task assigned by MVN. The results discussed in this SR will be used to inform the interpretation of geophysical surveys, construction of physical models, and input for the slope stability analyses.

30 Aug 2022

Legacy Datums and Changes in Benchmark Elevation through Time at the Old River Control Structure, Louisiana

Abstract: Vertical datums used in the study area at the Old River Control Structure in southern Louisiana have involved Memphis Datum, Mean Gulf Level, Mean Sea Level, Mean Sea Level Datum of 1929, National Geodetic Vertical Datum of 1929, and the North American Vertical Datum of 1988. The focus of this study was to examine historic benchmarks in the study area to determine the magnitude of elevation changes associated with the different legacy datums that have been used by the US Army Corps of Engineers. Comparison of elevation values across these legacy datums has involved examining historic hydrographic surveys, compiling a list of known benchmarks from these surveys, and comparing their elevation values against publications involving spirit-leveling surveys from the Lower Mississippi Valley and the National Geodetic Survey database for benchmarks. This study describes the history of legacy datums, floodplain geology at the Old River Control Structure, potential subsidence impacts affecting the benchmarks, methods for identification and tracking benchmarks, and the results obtained from this study.

5 May 2022

Waterborne Geophysical Investigation to Assess Condition of Grouted Foundation: Old River Control Complex – Low Sill Structure, Concordia Parish, Louisiana

Abstract: The Old River Low Sill Structure (ORLSS) at the Old River Control Complex (ORCC) in Concordia Parish, LA, is a steel pile-founded, gated reinforced-concrete structure that regulates the flow of water into the Atchafalaya River to prevent an avulsion between the Mississippi River and the Atchafalaya River. A scour hole that formed on the southeast wall of ORLSS during the Mississippi River flood of 1973 was remediated with riprap placement and varied mixtures of self-leveling, highly pumpable grout. Non-invasive waterborne geophysical surveys were used to evaluate the distribution and condition of the grout within the remediated scour area. Highly conductive areas were identified from the surveys that were interpreted to consist mostly of grout. Resistive responses, likely representing mostly riprap and/or sediment, were encountered near the remediated scour area periphery. A complex mixture of materials in the remediated scour area is interpreted by the more gradual transitions in the geophysical response. Survey measurements immediately beneath ORLSS were impeded by the abundance of steel along with the structure itself. The survey results and interpretation provide a better understanding of the subsurface properties of ORLSS.

9 Sep 2021

Geophysical Investigation to Assess Condition of Grouted Scour Hole: Old River Control Complex—Low Sill Concordia Parish, Louisiana

Abstract: Geophysical surveys, both land-based and water-borne, were conducted at the Old River Control Complex‒Low Sill, Concordia Parish, LA. The purpose of the surveys was to assess the condition of the grout within the scour region resulting from the 1973 flood event, including identification of potential voids within the grout. Information from the ground studies will also be used for calibration of subsequent marine geophysical data and used in stability analysis studies. The water-borne survey consisted of towed low frequency (16-80 MHz) ground penetrating radar (GPR), whereas the land-based surveys used electrical resistivity and seismic refraction. The GPR survey was conducted in the Old River Channel on the upstream side of the Low Sill structure. The high electrical conductivity of the water (~50 mS/m) precluded penetration of the GPR signal; thus, no useful data were obtained. The land-based surveys were performed on both northeast and southeast sides of the Low Sill structure. Both resistivity and seismic surveys identify a layered subsurface stratigraphy that corresponds, in general, with available borehole data and constructed geologic profiles. In addition, an anomalous area on the southeast side was identified that warrants future investigation and monitoring.

24 Aug 2021

Spatial Distribution and Thickness of Fine-Grained Sediment along the United States Portion of the Upper Niagara River, New York

Abstract: Over 220 linear miles of geophysical data, including sidescan sonar and chirp sub-bottom profiles, were collected in 2016 and 2017 by the US Army Corps of Engineers and the US Fish and Wildlife Service in the upper Niagara River. In addition, 36 sediment grab samples were collected to groundtruth the geophysical data. These data were used to map the spatial distribution of fine-grained sediment, including volume data in certain locations, along the shallow shorelines of the upper Niagara River. Overall, the most extensive deposits were spatially associated with either small tributaries or with man-made structures that modified the natural flow of the system. Extensive beds of submerged aquatic vegetation (SAV) were also mapped. Although always associated with a fine-grained matrix, the SAV beds were patchy in distribution, which might reflect subtle differences in the grain size of the sediment matrix or could simply be a function of variations in species or growth. The maps generated from this effort can be used to guide sampling plans for future studies of contamination in fine-grained sediment regions.

3 Jun 2021

Elevation of underlying basement rock, Ogdensburg Harbor, NY

Abstract: Over six linear miles of shallow acoustic reflection geophysical data were collected in an 800 ft by 300 ft survey region at Ogdensburg Harbor, Ogdensburg, NY. To better accommodate modern commercial vessels and expand the harbor’s capacity, the current navigable depth of -19 ft Low Water Depth (LWD) needs to be increased to -28 ft LWD, and an accurate map of the nature of the riverbed material (e.g., unconsolidated sediment, partially indurated glacial till, or bedrock) is required to effectively plan for removal. A total of 28 boreholes were previously collected to map the stratigraphy, and the effort revealed significant spatial variability in unit thickness and elevation between adjacent boreholes. To accurately map this variable stratigraphy, chirp sub-bottom profiles were collected throughout the region, with an average line spacing of 13 ft. These sub-bottom data, validated and augmented by the borehole data, resulted in high-resolution spatial maps of stratigraphic elevation and thickness for the study area. The data will allow for more accurate assessment of the type and extent of different dredging efforts required to achieve a future uniform depth of -28 ft LWD for the navigable region.