Amendment_02_TripReport_Schilling_and_Devore_11_20_final_02.pdf

United States Department of the Interior

National Park Service Midwest Archeological Center Federal Building, Room 474

IN REPLY REFER TO: H26 (JEFF) 100 Centennial Mall North Lincoln, Nebraska 68508-3873

November 18, 2020

Memorandum

To: Manager, Midwest Archeological Center (MWAC), National Park Service

(NPS)

From: Archeologists Tim Schilling and Steven L. De Vore, Park Archeology

Program

Subject: Trip Report – Geophysical Investigations of the Old Courthouse and

Courtyard at Gateway Arch National Park, Missouri (October 18-24, 2020)

On Sunday, October 18, Archeologists Timothy Schilling and Steven De Vore left Lincoln, Nebraska, in the late morning. We traveled to St. Louis, Missouri, and arrived in the evening where we unloaded the geophysical equipment and personal gear. I placed the batteries for the ground penetrating radar on their respective chargers. The geophysical investigations at the Gateway Arch National Park proposed the survey of the courtyards surrounding the Old Courthouse and within the basement and first floor of the Old Courthouse (Figure 1). The Old Courthouse was located west of the arch between Chestnut on the north, Market on the south, North Forth on the east, and North Broadway on the west (Figure 2).

We met Laura Johnson, the park Historical Architect, at the Old Courthouse on Monday, October 19. We discussed the activities planned for the week. Laura then took us on a tour of the basement rooms (Figure 3) and the first floor conference room (Figure 4).

After putting the Noggins ground penetrating radar cart (GPR) with the 500MHz antenna together, we started the GPR survey in the three rooms in the southwest corner of the south wing. The rooms include Rm. #048, 049, and 050. The GPR was set to collect the survey distance in English units (inches) inside the Old Courthouse. A calibration velocity for concrete of 0.328 ft/ns was used to set the depth for the survey. We established a survey grid in each room using tape to establish the survey transects. The survey was conducted in the uni-directional mode along parallel transects placed 9 inches apart. The first transects in Rm. #048, 049, and 050 began in the southwest corner of the room and proceeded to the east side of the room. The GPR survey area in Rm. #048 (south room) measured 81 inches (north-south) by 240 inches (east-west) and was identified as Project 1 with a GPR file identifier as OCHA (Figure 5). A total of 10 profiles were collected over a total survey length of 2,400 inches. Three line scans were conducted along the west wall to identify the possibility of the foundation wall extending under the floor. The GPR survey area in Rm. #049 (middle room) measured 90 inches (north-south) by 240 inches (east-west) and was identified as Project 2 with a GPR file identifier as OCHB (Figure 6). A total of 11 profiles were collected over a total survey length of 2640 inches. Three line scans were conducted along the west wall to identify the possibility of the foundation wall extending under the floor. The GPR survey area in Rm. #050 (north room) measured 99 inches (north-south) by 240 inches (east-west) and was identified as Project 3 with a GPR file identifier as OCHC (Figure 7). A total of 12 profiles were collected over a total survey length of 2880 inches. Three line scans were conducted along the west wall to identify the possibility of the foundation wall extending under the floor. After completing the GPR survey in the three southwestern rooms in the southern wing, we moved to the conference room (Rm. #107) on the first floor on the northwest side of the rotunda. We also downloaded the GPR profile data to a compact disk and transferred the profile data to a field laptop computer. Park staff placed a tape on the floor that corresponded with the basement walls. This was used as the zero baseline.

The first traverse was to the north with the survey proceeding in a uni-direction mode along parallel lines. The survey area measured 240 inches (north-south) by 236 inches (east-west) and was identified as Project 4 with a GPR file identifier as OCHD. A total of 27 profiles were collected in the y direction (north-south) over a total survey length of 6336 inches. Given the size of the room and the possible identification of a utility running diagonally across the floor, GPR profiles were also collected in the x direction (east-west). The survey area measured 252 inches (north-south) by 234 inches (east-west) and was identified as Project 5 with a GPR file identifier as OCHE. A total of 29 profiles were collected in the x direction (east-west) over a total survey length of 5916 inches. A small area in the southwest corner of the conference room was also added to the overall GPR survey of the room. The area measured 72 inches (north-south) by 81 inches (east-west) and was identified as Project 6 with a GPR file identifier as OCHF. A total of 9 profiles were collected in the y direction (north-south) over a total survey length of 648 inches. The profile data from the conference room were downloaded to a compact disk and transferred to the field laptop computer. During the evening, I processed the GPR data we collected during the day. The GPR data were sliced into 20 layers and a 3D model of the data was generated. An error in the distance associated with the length of the x direction line profiles was identified, so those profiles were later recollected.

We started Tuesday, October 20, discussing the results of the GPR surveys in the three basement rooms and the first floor conference room. After the review of these data, we went to the basement in the west wing. We started in the utility room in the middle of the wing along the south side identified as Rm. #002. The room has a number of stations holding electrical conduit and cable above the floor limiting the survey area. The survey area measured 185 inches (north-south) by 51 inches (east-west) and was identified as Project 7 with a GPR file identifier as OCHG (Figure 8). A total of 7 profiles were collected over a total survey length of 1295 inches. Project 8 identified as OCHH was located in the public restrooms on the north side of the west wing in Rm. #009. Since the floor of the men’s public toilets contained a center trough and individual stalls that curved along the edges and contained differing heights of the broken marble stall walls, the park maintenance staff constructed a raised plywood platform prior to the GPR survey of the room. The survey area measured 187 inches north-south by 108 inches east-west. A total of 13 profiles were collected over a total survey length of 2353 inches.

The profiles were collected in the y direction. Project 9 identified as OCHI was also conducted in Rm. #009 but in the x direction. The survey area measured 217 inches north-south by 68 inches east-west. A total of 25 profiles were collected over a total survey length of 1700 inches. Project 10 identified as OCHJ was conducted in the corridor on the north side of the courthouse’s center area under the rotunda, which was identified as Rm. #014. The corridor opens to the east and west moats on the north side of the east and west wings. The survey area measured 54 inches north-south by 666 inches east-west. A total of 6 profiles were collected over a total survey length of 3996 inches. Project 11 identified as OCHK was a small offset on the north side of Rm. #014 that was located 198 inches east of the west door sill and was 68 inches wide. The survey area measured 55 inches (north-south) by 50 inches (east-west). A total of 6 profiles were collected over a total survey length of 288 inches. Project 12 identified as OCHL was located in the areaway, or moat, on the north side of the west wing (Figure 9). The survey area extends from the steps on the east side below the door to Rm. #014 to the steps at the west end of the moat. The survey area measured 18 inches north-south by 677 inches east-west. Three profiles were collected over a total survey length of 2031 inches. Project 13 identified as OCHM was located in the moat on the south side of the west wing (Figure 10). The survey area measured 62 inches north-south by 744 inches east-west. Five profiles were collected over a total survey length of 3670 inches. Project 14 identified as OCHN was located in the moat on the north side of the east wing (Figure 11). The survey area extends from the steps on the west side below the door below Rm.

#014 to the steps at the east end of the moat. The survey area measured 62 inches north-south by 844 inches east-west. Seven profiles were collected over a total survey length of 4893 inches. The profile data were downloaded to the compact disk and transferred to the filed laptop computer. During the evening, the GPR profile data from the eight project areas were processed. Twenty slices were generated along with the 3D model for each project survey area. Profile data from the y and x directions in Rm. #009 from Projects 8 and 9 were merged together into one project file with 38 profiles measuring a total survey length of 4063 inches (Figure 12). In addition, the profile data from Projects 10 and 11 were merged together into one project file with 12 profiles measuring a total survey length of 4284 inches (Figure 13).

On Wednesday, October 21, we began by redoing the x direction GPR survey in the first floor conference room to correct an error in the overall distance in the x direction profiles (Project 15). I transferred the profile data to the compact disk and then to the laptop computer. We then started to stake out the survey areas in the four exterior courtyards using the survey compass and a 100-meter stake. We began in the northwest courtyard.

The initial mapping station was located one meter east of the west wall and fence and three meters north of the north exterior step wall to the west wing of the courthouse.

Arbitrary coordinates of N3/E1 were assigned to the initial mapping station. A backsight stake was placed one meter from the west wall north of the initial mapping station. Using the surveying compass and 100-meter tape, we staked out the geophysical grid. Wooden hub stakes were placed 20 and 23 meters north of the initial mapping station for the west baseline. The grid was oriented 22º east of magnetic north. Along the south baseline, wooden hub stakes were placed at 10, 20, and 23 meters east of the initial mapping station. Additional wooden hub stakes were placed to form three partial geophysical grid units. The grid measured 23 meters east-west by 23 meters north-south for a total area of 359 m2 or 0.09 acres (Figure 14). After staking out the Northwest grid, we moved to the Southwest courtyard and set up the grid in the yard. The initial mapping station was placed two meters east of the west wall and fence and two meters north of the south wall and fence. Arbitrary coordinates of N2/E2 were assigned to the initial mapping station.

A backsight stake was placed two meters from the west wall north of the initial mapping station. Using the surveying compass and 100-meter tape, we staked out the geophysical grid. A wooden hub stake was placed at 20 meters north of the initial mapping station for the west baseline. The grid was oriented 20º east of magnetic north. Along the south baseline, a wooden hub stake was placed at 16 meters east of the initial mapping station.

Additional wooden hub stakes were placed to form two partial geophysical grid units.

The grid measured 25 meters east-west by 20 meters north-south for a total area of 257 m2 or 0.07 acres (Figure 15). We then moved to the Northeast yard where we set the initial mapping station one meter east of the courthouse wall and one meter north of the moat wall. Arbitrary coordinates of N1/E1 were assigned to the initial mapping station.

A backsight stake was placed one meter from the north edge of the moat wall east of the mapping station. Using the surveying compass and 100-meter tape, we staked out the geophysical grid. A wooden hub stake was placed 5 meters north of the initial mapping station for the west baseline. The grid was oriented 14º east of magnetic north. Along the south baseline, wooden hub stakes were placed at 5, 10, 20, and 29 meters east of the initial mapping station. The northern edge of the grid was 20 meters from the south baseline. Additional wooden hub stakes were placed to form two partial geophysical grid units. The grid measured 29 meters east-west by 20 meters north-south for a total area of 430 m2 or 0.11 acres (Figure 16). We finished staking out the Southeast yard where the initial mapping station was set two meters east of the courthouse wall and two meters north of the south wall and fence. Arbitrary coordinates of N2/E2 were assigned to the initial mapping station. A backsight stake was placed two meters from the east wall of the south wing of the courthouse north of the mapping station. Using the surveying compass and 100-meter tape, we staked out the geophysical grid. A wooden hub stake was placed 16 meters north of the initial mapping station for the west baseline. The grid was oriented 20.5º east of magnetic north. Along the south baseline, wooden hub stakes were placed at 20 and 25 meters east of the initial mapping station. Additional wooden hub stakes were placed to form two partial geophysical grid units. The grid measured 25 meters east-west by 16 meters north-south for a total area of 400 m2 or 0.10 acres (Figure 17). After staking out the four grid units, I collected the locational data on the grid unit corners with the mapping grade GPS unit and external antenna. We finished the afternoon laying out the survey ropes on the four grid units for the GPR survey on Thursday. During the evening, I downloaded the GPS data to the field laptop computer and processed it. I continued to process the GPR data from the survey areas on the interior of the courthouse and from the three moat areas. The three GPR line files from the conference room were also merged into one survey file with 65 profiles measuring a total survey length of 12899 inches (Figure 18).

On Thursday, October 22, we reviewed the GPR data from the investigations on Tuesday and Wednesday. We began the GPR survey of the four courtyards. We started in the Northwest yard. The Noggins GPS cart with a 500 MHz antenna was reset to meters for the exterior yard investigations. The calibration velocity was set to moist soil at 0.090 m/ns with estimated depth of 4.5 meters or 100 ns. After testing the area, The depth was reset to 2.5 m or 55.6 ns. The time window was set to two way travel time of 61.2 ns.

I collected the profile data in a zigzag mode of bi-directional. The survey in the Northwest courtyard was identified as Project 16 with the file labeled OCHNW (Figure 19). Fifty-two profiles were collected over a total survey length of 819.5 meters. The GPR survey of the exterior yards continued with the investigations of the Southwest courtyard. The survey was identified as Project 17 with the file labeled OCHSW (Figure 20). Fifty-one profiles were collected over a total survey length of 596 meters. The profile data from the Northwest and Southwest courtyards were downloaded to a compact disk and transferred to the field laptop computer at the Courthouse. The survey in the Southeast courtyard was identified as Project 18 with the file labeled OCHSE (Figure 21). Fifty-one profiles were collected over a total survey length of 504 meters. The survey in the Northeast courtyard was identified as Project 19 with the file labeled OCHNE (Figure 22). Fifty-nine profiles were collected over a total survey length of 880 meters. At the end of the GPR survey in the Northeast courtyard, the profile data were downloaded to the compact disk and transferred to the laptop computer. During the evening, the GPR data were processed into slices and gridded to form a 3D model of the GPR data for each courtyard.

On Friday, October 23, we conducted the conductivity and magnetic susceptibility surveys in the Northwest and Southwest courtyards with the electromagnetic induction meter. Survey traverse ropes were laid on the grid at two meter intervals. The electromagnetic induction meter collected conductivity and magnetic susceptibility data at 0.5-m and 1.0-m coil separations yielding four data sets for each geophysical project area. The data were collected at four samples per meter along 0.5-m traverses in a uni-directional mode across the grid. The first traverse was to the north. The data were downloaded to the field laptop computer during the afternoon at the courthouse. We also packed the geophysical equipment in the minivan. In the evening, I continued to process the geophysical and GPS data from the geophysical investigations of the Old Courthouse and courtyard. The Geonics EM38MK2 data were converted from the Geonics raw format to data format. The data format was used to create the XYZ data file for input in Surfer. The data was imported into GEOPLOT where each conductivity and magnetic susceptibility data file was processed and exported to Surfer for the generation of data plots for the Northwest (Figure 23) and Southwest Courtyards (Figure 24). During the evening, I also packed up the computers, printer, and personal gear.

Tim Schilling and I left St. Louis early Saturday morning, October 24. We arrived at the Federal Building in the early afternoon. We were met at the Federal Building by Ann Bauermeister to unload the geophysical and office equipment. Tim and I also unloaded our personal gear before parking the minivan in the Federal Parking Garage.

The success of the ground penetrating radar survey is dependent on soil and sediment mineralogy, clay content, ground moisture, depth of the archeological resource, and surface topography and vegetation. The ground-penetrating radar signal can be lost or attenuated (i.e., quickly dissipated) in soils that have high moisture content, high electrical conductivity, highly magnetic materials, or high clay contents. Dry soils and sediments, especially those with low clay content, represent the best conditions for energy propagation. A ground-penetrating radar survey, with its capability for estimating the depth and shape of buried objects, may be an extremely valuable tool in the search of grave shafts and trenches. At times, radar cannot profile deep enough or the strata may be so complex as to render the trenches, graves, and other types of excavations indistinguishable from the surrounding soil profile.

The ground penetrating radar profile data were processed. Initially, the individual profile data were filtered with a bandpass filter to remove unwanted frequencies. The background removal filter was applied to remove banding noise found in the profile data.

Hyperbola matching was used to set the signal velocity. Once the individual radar profiles were processed, the area between the profiles were interpolated and time slices were generated and gridded. Each set of project data were then interpolated into 96 slices for the generation of 3D models. Individual time slices were examined and one or more were selected to represent the major contrasts in amplitude strength between the soil matrix and buried objects (Table 1).

Analysis and interpretation of the GPR data may be conducted in several different ways.

The individual radargrams for each profile line may be analyzed for hyperbolic reflections. The radargrams may be combined and processed to provide planar time slices of the data. The time slices may also be combined to form 3D cubes of the GPR data. The majority of the GPR radargrams show numerous small reflections along any given profile. Most of the analysis of the GPR data is done with the 3D display while moving through the numerous time slices, but in order to provide a graphic representation of the anomalous areas, an individual time slice was selected.

Analysis of the GPR Time Slice 8 data from Project 1 in Rm. #048 indicated the presence of a vertical utility access (Figure 25). A manhole cover is visible on the floor near the doorway leading from Rm. #045. Analysis of the GPR Time Slice 3 data from Project 2 in Rm. #049 indicated the presence of a vertical utility access (Figure 26). A manhole cover is visible in the corner of the room near the doorway leading from Rm. #046.

Analysis of the GPR Time Slice 2 data from Project 3 in Rm. #050 indicated the presence of a drain near the side doorway in Rm. #050 (Figure 27). The drain cover is visible near the doorway leading from Rm. #049. Analysis of the GPR Time Slice 9 data from the combined Projects 4, 5, and 6 with corrected Project 15 profile data in the Conference Room, Rm. #107, indicated the arched vault from the basement Rm. #14 and a utility line running diagonally under the floor (Figure 28). Analysis of the GPR Time Slice 14 from Project 7 in Rm. #002 suggested the presence of a utility line under the floor near the south side of the room (Figure 29). Several obstacles in the room limited the total survey area including braces and wall mounted utilities. Analysis of the GPR Time Slice 15 data from the combined Projects 8 and 9 in the y direction and the xdirection, respectively, indicated the presence of several utility lines associated with water intake and sewage disposal lines in the men’s public toilet Rm. #009 (Figure 30). Due to the rough floor, including the trench between the toilet stalls, individual toilet stalls with the circular toilet drains, and the broken bases of the marble stall dividers, a plywood platform was raised on 4x4’s to provide a flat surface to the radar; however, this raised the antenna over four inches above the concrete floor. Analysis of the GPR Time Slice 2 from the combined Projects 10 and 11 in the Rm. #014 areaway indicated a utility line along the south side of the room (Figure 31). Additional utility lines extend perpendicular to it. Two metal plates cover the utility line on the east side near the exterior doorway. A vertical utility access in the small inset is visible. Analysis of the GPR Time Slice 12 from Project 12 in the West Wing North Moat identified the presence of drain/utility lines beneath the sidewall (Figure 32). Drain covers are present above two of the drain lines. Analysis of the GPR Time Slice 18 from Project 13 in the West Wing South Moat identified the presence of a drain line along the southern side of the moat (Figure 33). Two drain covers identify the location of the drain. Analysis of the GPR Time Slice 10 from Project 14 in the East Wing North Moat indicated the presence of a potential drain line near the west end of the moat (Figure 34). Two drain covers were located along the northern moat wall.

Geophysical grids were placed in the four courtyards surrounding the Old Courthouse (Figure 35). Analysis of the GPR Time Slice 7 from the Northwest Courtyard identified a utility line extending from the moat wall to the yard gate (Figure 36). A utility access was located near the southwest corner of the geophysical grid. A ring surrounding the column display was composed of a metal ring with contrasting fill from the surrounding soil matrix. Analysis of the GPR Time Slice 5 from the Southwest Courtyard identified the rebar in the entrance sidewalk (Figure 36). A buried utility line parallels the west wall of the South Wing. Analysis of the GPR Time Slice 5 from the Northeast Courtyard identified a ring surrounding the display column (Figure 38). Its construction appeared similar to the ring surrounding the column display in the Northwest Courtyard. Several segments of the irrigation lines were identified in the time slice. Analysis of the GPR Time Slice 5 from the Southwest Courtyard indicated the presence of a strong reflector suggesting a concrete pad or rubble pile in the northwest corner of the geophysical grid (Figure 39).

The conductivity and magnetic susceptibility surveys were conducted with an electromagnetic induction meter operating in the quadrature phase and in-phase operating modes at 0.5-meter and 1.0-m coil separations providing four separated geophysical data sets. Measurable contrasts resulted from changes in the electrical and magnetic properties of the soil matrix. Contrasts were caused by materials buried in the soil, differences in soil formation processes, or disturbances from natural or cultural modifications to the soil. Interpretation of the conductivity data results in the identification of lateral changes in the soil matrix. The conductivity data may be divided into three classes of anomalies including linear anomalies, point anomalies, and broad anomalous areas. Linear anomalies may represent foundations of buildings, trenches, buried utility lines, paths, trails, or roads that are longer than they are wide. Point anomalies tend to represent buried objects or vertical structures such as cisterns, wells, or storage pits. Occasionally, these anomalies may have negative values resulting from the saturation of the receiving coil by the overwhelming conductive metal response of buried metals to the generated electromagnetic field. Broad anomalous areas typically represent large areas of soil disturbances or compaction often found associated with gardens, basements or cellars, parking pads, compacted dirt floors, trash dumps, or areas of concrete or asphalt. EM instruments were also sensitive to surface and buried metals.

Due to their high conductivity, metals were identified by extreme values in the acquired data set. On occasion, these values may be expressed as negative values since the extremely high conductivity signal of the metals cause the secondary coil to become saturated. The application of magnetic susceptibility to archeological prospection centers around two factors: 1) typically, greater susceptibility is found in the topsoil than in underlying subsoil, and 2) human activities associated with site occupation enhance the susceptibility of the topsoil. The method has been developed to detect evidence of human occupation and define site limits in the topsoil even when no distinctive features have survived. It can be applied to research questions concerning the following topics: 1) site limits, activity areas, or features; 2) morphology or function of sites, activity areas, and features and their formation processes; 3) the effects of sedimentation and erosion upon the archeological record; 4) establishing and expanding stratigraphic sequences; and

5) climatic regimes and other information on soil-forming factors. Magnetic susceptibility studies have been used to study accumulated cultural and natural deposits.

These techniques can also be used to correlate stratigraphy across a site, as well as, identify buried soils or paleosols.

In archeology, the instrument has been used to identify areas of compaction and excavation as well as buried metallic objects. It has the potential to identify cultural features that are affected by the water saturation in the soil. Its application to archeology results from the ability of the instrument to detect lateral changes on a rapid data acquisition, high resolution basis, where observable contrasts exist. Lateral changes in anthropogenic features result from compaction, structural material changes, buried metallic objects, excavation, habitation sites, and other features affecting water saturation. The conductivity survey can sometimes detect the disturbed soil matrix within the grave shaft. It can also locate large metal objects. Metallic trash on the surface and other small objects buried in the upper portion of the soil can degrade the search of the buried archeological resources including graves.

Conductivity data from the Northwest Courtyard yielded numerous conductivity features in 0.5-m coil separation (Figure 40) and the 1.0-m coil separation (Figure 41). Both depths indicate the metal ring surrounding the display column. The utility line from the gate to the moat is identified along with the utility access cover. A second utility line extends from the southeast corner of the grid to the northeastern edge of the grid.

Possible irrigation lines are represented by alternating positive and negative values. An additional utility line cuts diagonally across the southern part of the grid in the data from the 1.0-m coil separation. The magnetic susceptibility data from the 0.5-m (Figure 42) and the 1.0-m coil separation (Figure 43) also identify the metal ring surrounding the display column, the utility line and utility cover in the southwestern corner of the grid along with the three potential irrigation lines in the center of the project area. A fourth possible irrigation line is near the grid edge in the southeast corner. The presence of the flood lights along the west side near the northwest corner of the geophysical grid is indicated by extreme positive and negative susceptibility values. Conductivity data from the Southwest Courtyard yielded numerous conductivity features in the 0.5-m coil separation (Figure 44) and the 1.0-m coil separation (Figure 45). The reinforced concrete entrance walk is represented by strong positive values. The remnants of a buried ring for a display column is present in the middle of the yard in both conductivity data sets. A diagonal utility lines runs across the yard. An additional utility line is located to the north of the northwest corner of the South Wing. The metal grills over the basement windows of the west wall of the South Wing are represented by high positive data values. The utilities along the north wall of the South Wing are also represented by high positive values in the magnetic susceptibility data from the 0.5-m coil separation (Figure 46) and the 1.0-m coil separation (Figure 47). The reinforced concrete sidewalk, the buried monument ring, and the window grills are represented in the two data sets. The utility line north of the South Wing is also indicated in the data, as well as the above ground utility units along the South Wing. The diagonal utility line in the conductivity data sets is not identified in the magnetic susceptibility data sets.

cc: JEFF Superintendent (one electronic copy) JEFF Historical Architect (one electronic copy) MWAC Archeologist (one copy and one electronic copy) MWAC Archeologist (one electronic copy) MWAC Collections (one copy) MWAC Library (one copy) MWAC AIM Team (two copies)

Table 1. Profile data for Old Courthouse ground penetrating radar investigations.

Project/ File Name

Room

Length Width Area Number of

Profiles

Total Survey Length

Velocity (m/ns)

Profile Depth

Time Slice

1/(OCHA) 048 240 in 81 in 19440 sq in

10 2400 in 0.035 28.53 in

(14.6- 19.7 ns)

[9.9- 13.4 in]

2/(OCHB) 049 240 in 90 in 21600 sq in

11 2640 in 0.035 21.75 in

( 0.5- 5.6 ns)

[0.2- 3.6 in]

3/(OCHC) 050 240 in 99 in 23760 sq in

12 2880 in 0.027 22.28 in

(2.0- 7.1 ns)

[1.1- 3.8 in]

4/(OCHD-ny) 107 240 in 236 in 56640 sq in

27 6336 in 0.038 32.49 in

5/(OCHE-nx) 107 234 in 216 in 50544 sq in

29 5916 in 0.026 21.89

6/(OCHF-sy) 107 81 in 72 in 5832

9 648 in 0.054 46.17

7/(OCHG) 002 185 in 51 in 9435

7 1295 in 0.032 30.54 in

(33.8- 38.9 ns)

[21.3- 24.5 in]

8/(OCHH-y) 009 187 in 108 in 20196 sq in

13 2353 in 0.023 19.99

9/(OCHI-x) 009 217 in 68 in 14756

25 1700 in 0.044 36.09

10/(OCHJ-x) 014 666 in 54 in 35964

6 3996 in 0.05 37.03

11/(OCHK-y) 014 55 in 50 in 2750

6 288 in 0.06 54.09

12/(OCHL) NW

Moat

677 in 18 in 12186 sq in

3 2031 in 0.04 32.21 in

(22.7- 27.8 ns)

[17.9- 21.9 in]

13/(OCHM) SW

Moat

744 in 62 in 46128 sq in

5 3670 in 0.049 41.61 In

(15.2- 20.2 ns)

[14.5- 19.4 in]

14/(OCHN) NE

Moat

844 in 62 in 52328 sq in

7 4893 0.034 29.07 in

(19.7- 24.7 ns)

[13.2- 16.6 in]

15/(OCHE2-

nx)

107 252 in 204 in 51408 sq in

29 6264 in 0.06 51.3 in

OCHDAA 107 326 in 234 in 76284 sq in

65 12899 in

0.057 48.45 in

(17.2- 22.2 ns)

[19.4- 25.1 in]

OCHHAA 009 217 in 108 in 23436 sq in

38 4028 in 0.08 66.01 in

(29.8- 34.8 ns)

[46.9- 54.9 in]

OCHJAA 014 666 in 109 in 72594 sq in

12 4254 in 0.051 43.85 in

(2.0- 7.1 ns)

[2.0- 7.1 in]

NW

Courtyard

25.5 m 23 m 586.5 sq m

52 819.5 m

0.081 1.82 m 7 (3.4- 4.1 ns)

[0.1- 0.2 m]

SW

Courtyard

29 m 20 m 580 sq m

59 880 m 0.047 1.08 m 5 (2.5- 5.7 ns)

[0.1- 0.2 m]

SE Courtyard 25 m 16 m 400 sq m

51 504 m 0.061 1.36 m 5 (2.3- 5.6 ns)

[0.1- 0.2 m]

NE

Courtyard

25 m 21 m 525 sq m

51 596 m 0.073 1.63 m 5 (2.3- 5.6 ns)

[0.1-

0.1 m]

Table 2. Conductivity and magnetic susceptibility data for Courtyard geophysical project areas.

Grid Location

Survey Type/Coil Separation

Grid Length (m)

Grid Width (m)

Area (sq m)

Data Range

Data Mean

Data Standard Deviatio n

NW

Courtyard

Conductivity/

0.5 m

23 23 359 -1280 to 323.5 mS/m

-21.92 mS/m

84.719 mS/m

NW

Courtyard

Conductivity/

1.0 m

23 23 359 -839.1 to 281.6 mS/m

52.16 mS/m

53.354 mS/m

NW

Courtyard

Magnetic Susceptibility /0.5 m

23 23 359 -9.2 to

9.2 ppt

0.24 ppt

1.436 ppt

NW

Courtyard

Magnetic Susceptibility / 1.0 m

23 23 359 -35.9 to

36.9 ppt

2.31 ppt

4.967 ppt

SW

Courtyard

Conductivity/

0.5 m

25 20 257 -482.6 to 755.9 mS/m

16.73 mS/m

105.370 mS/m

SW

Courtyard

Conductivity/

1.0 m

25 20 257 -670.4 to 658.5 mS/m

48.1 mS/m

129.328 mS/m

SW

Courtyard

Magnetic Susceptibility /0.5 m

25 20 257 -9.1 to

9.2 ppt

0.64 ppt

2.266 ppt

SW

Courtyard

Magnetic Susceptibility / 1.0 m

25 20 257 -36.8 to

36.9 ppt

0.84 ppt

9.674 ppt

Figure 1. Location of the geophysical project at the Old Courthouse, Jefferson National

Expansion Memorial, St. Louis, Missouri.

Figure 2. General view of the Old Courthouse in St. Louis, Missouri (view to the northwest).

Figure 3. Priority rooms in the basement of the Old Courthouse.

Figure 4. Priority rooms on the first floor of the Old Courthouse.

Figure 5. Time slices of the GPR data from Project 1 in Rm. 048.

Figure 6. Time slices of the GPR data from Project 2 in Rm. 049.

Figure 7. Time slices of the GPR data from Project 3 in Rm. 050.

Figure 8. Time slices of the GPR data from Project 7 in Rm. 002.

Figure 9. Time slices of the GPR data from Project 12 in the Northwest Moat.

Figure 10. Time slices of the GPR data from Project 13 in the Southwest Moat.

Figure 11. Time slices of the GPR data from Project 14 in the Northeast Moat.

Figure 12. Time slices of the GPR data from Projects 8 and 9 in Rm. 009.

Figure 13. Time slices of the GPR data from Project 10 and 11 in Rm. 014.

Figure 14. Northwest Courtyard grid.

Figure 15. Southwest Courtyard grid.

Figure 16. Northeast Courtyard grid.

Figure 17. Northeast Courtyard grid.

Figure 18. Time slices of the GPR data from Projects 4, 5, 6, and 15 in Rm. 107.

Figure 19. Time slices of the GPR data from Project 16 in the Northwest Courtyard.

Figure 20. Time slices of the GPR data from Project 17 in the Southwest Courtyard.

Figure 21. Time slices of the GPR data from Project 18 in the Southeast Courtyard.

Figure 22. Time slices of the GPR data from Project 19 in the Northeast Courtyard.

Figure 23. Conductivity and magnetic susceptibility data for 0.5 and 1.0 coil separations from the Northwest Courtyard.

Figure 24. Conductivity and magnetic susceptibility data for 0.5 and 1.0 coil separations from the Southwest Courtyard.

Figure 25. Interpretation of the Time Slice 8 data from Rm. #048.

Figure 26. Interpretation of the Time Slice 3 data from Rm. #049.

Figure 27. Interpretation of the Time Slice 2 data from Rm. #050.

Figure 28. Interpretation of the Time Slice 9 data from Rm. #107.

Figure 29. Interpretation of the Time Slice 14 data from Rm. #002.

Figure 30. Interpretation of the Time Slice 15 data from Rm. #009.

Figure 31 Interpretation of the Time Slice 8 data from Rm. #014.

Figure 32. Interpretation of the Time Slice 12 data from the West Wing North Moat.

Figure 33. Interpretation of the Time Slice 18 data from West Wing South Moat.

Figure 34. Interpretation of the Time Slice 10 data from the East Wing North Moat.

Figure 35. Location of the geophysical courtyard grids.

Figure 36. Interpretation of the Time Slice 7 data from the Northwest Courtyard.

Figure 37. Interpretation of the Time Slice 5 data from the Southwest Courtyard.

Figure 38. Interpretation of the Time Slice 5 data from the Northeast Courtyard.

Figure 39. Interpretation of the Time Slice 5 data from the Northeast Courtyard.

Figure 40. Interpretation of the conductivity data from the 0.5-meter coil separation in the Northwest Courtyard.

Figure 41. Interpretation of the conductivity data from the 1.0-meter coil separation in the Northwest Courtyard.

Figure 42. Interpretation of the magnetic susceptibility data from the 0.5-meter coil separation in the Northwest Courtyard.

Figure 43. Interpretation of the magnetic susceptibility data from the 1.0-meter coil

Figure 44. Interpretation of the conductivity data from the 0.5-meter coil separation in the Southwest Courtyard.

Figure 45. Interpretation of the conductivity data from the 1.0-meter coil separation in the Southwest Courtyard.

Figure 46. Interpretation of the magnetic susceptibility data from the 0.5-meter coil separation in the Southwest Courtyard.

Figure 47. Interpretation of the magnetic susceptibility data from the 1.0-meter coil