AirKnife_Exploration.pdf

Doc/proj/del/J017065.10 CAR 2015 Air Knife RF.doc

FINAL REPORT

AIR KNIFE EXPLORATION

CITY ARCH RIVER 2015

JEFFERSON NATIONAL EXPANSION MEMORIAL

ST. LOUIS, MISSOURI

Prepared For:

CITY ARCH RIVER 2015 FOUNDATION

St. Louis, Missouri

Prepared By:

GEOTECHNOLOGY, INC.

St. Louis, Missouri

Geotechnology, Inc. Project No. J017065.10

November 15, 2013

November 15, 2013 J017065.10

Ms. Janis Cooper CityArchRiver 2015 Foundation One South Memorial Drive Gateway Tower, Suite 700 St. Louis, Missouri 63102

FINAL REPORT

AIR KNIFE EXPLORATION

CITY ARCH RIVER 2015

JEFFERSON NATIONAL EXPANSION MEMORIAL

ST. LOUIS, MISSOURI

Dear Ms. Cooper:

Geotechnology, Inc. performed air knife excavations for the referenced project in accordance with the scope of services described in our Proposal No. P021301.02, Revision #2 dated June 7, 2013. The purpose of our services was to perform excavations using air knife vacuum extraction equipment to measure the depth and elevation of the roof of the museum and railroad tunnel.

Air knife (vacuum extraction) holes were performed at nine locations over the Visitor Center Museum and seven locations over the Terminal Railroad tunnel. Alper Audi and Michael Van Valkenburgh Associates, Inc. selected the air knife locations over the museum and railroad tunnel, respectively. The air knife equipment is designed to remove the soil overburden through compressed air without damaging underlying utilities or, in this case, roof structures.

SUBSURFACE EXPLORATION

Air knife holes AK-1 through AK-9 were excavated above the museum generally using a trailer-mounted VacMasters 1000 unit at approximately the locations shown on Plate 1. The locations were surveyed and staked in the field by Engineering Design Source, Inc. (EDSI), who determined ground surface elevations. Upon excavation of each location, Geotechnology measured the depth to the top of the roof membrane using a tape measure and backfilled the excavation with soil cuttings and sand. We also recorded the apparent edge of the museum roof relative to the survey stake at locations AK-7 and AK-9.

CityArchRiver 2015 Foundation J017065.10 November 15, 2013 Air Knife Exploration

Air knife holes TAK-1 through TAK-7 were excavated above the railroad tunnel at approximately the locations shown on Plates 2 through 4. EDSI surveyed and staked the locations and determined ground surface elevations. Initially, Geotechnology attempted air knife excavations using the VacMasters 1000 unit. However, roots, rubble, and hard clay soils prohibited excavating to the tunnel roof at every location except TAK-1. We subsequently contracted with Kantex Subsurface, Inc., to excavate the holes using a more powerful air vacuum unit. Upon excavation of each location, Geotechnology measured the depth to the top of the roof using a tape measure. The excavations were then backfilled with soil cuttings. The apparent edge of the tunnel roof was recorded relative to the survey stake at location TAK-4.

An engineer from Geotechnology provided technical direction during field exploration, observed excavation, collected samples, and prepared descriptive logs of the material encountered.

SUBSURFACE CONDITIONS

The soil above the museum consists generally of silty clay underlain by a layer of tan, fine-grained sand. The museum roof appears to be covered by an asphaltic or geosynthetic membrane. The depth of the museum roof measured in the air knife holes ranges from 1.1 to 2.1 feet.

In discussion with Mr. Randy Dreiling, P.E., and Mr. Mike Rachford, Executive Vice President of Elastizell of St. Louis, Inc., we understand that the museum roof was repaired circa 1990. The repair included placing a layer of bituminous waterproofing material (used on bridge decks) on the existing roof, pouring Elastizell lightweight concrete over the roof, and installing another layer of waterproofing over the Elastizell. The covering had an apex in the center of the roof and sloped down towards the edges. The covering overhangs the museum walls by approximately 2 feet with a 3-foot downturn that is steel-reinforced within the Elastizell. An irrigation system was installed above the repaired roof which is covered by approximately 18 inches of soil.

The soil above the railroad tunnel consists generally of silty clay with gravel, brick, and concrete rubble. The soil is also heavily rooted from shrubs and trees planted on or adjacent to the roof. The tunnel roof appears to be covered by a bituminous coating. The depth of the tunnel roof measured in the air knife holes ranges from 2.9 to 5.9 feet.

A summary of the air knife excavation data is presented in Table 1. Groundwater was not observed in the air knife excavations.

CityArchRiver 2015 Foundation J017065.10 November 15, 2013 Air Knife Exploration

TABLE 1

SUMMARY OF AIR KNIFE EXPLORATION DATA

Air Knife Excavation

No.

Northing Easting

Ground Surface

Elevation (ft msl)*

Approximate Depth to Museum/

Tunnel Roof (ft)

Approximate Museum/Tunnel Roof Elevation

(ft msl)

Comments

AK-1 14038491.89 2444262.71 446.11 1.7 444.4

AK-2 14038354.09 2444214.80 446.64 2.1 444.6

AK-3 14038212.96 2444182.17 445.93 1.3 444.6

AK-4 14038452.32 2444400.25 445.98 1.4 444.6

AK-5 14038312.33 2444359.97 447.13 1.1 446.0

AK-6 14038173.32 2444319.98 446.08 1.5 444.6

AK-7 14038409.60 2444545.15 445.70 1.1 444.6

Edge of museum roof

1.5 feet east of survey stake

AK-8 14038270.56 2444505.15 445.61 1.1 444.5

AK-9 14038132.51 2444465.43 445.59 1.1 444.5

Edge of museum roof

1.25 feet east of survey stake

TAK-1 14037944.76 2444482.13 446.50 2.5 444.0

TAK-1A 14037944.65 2444482.16 446.39 2.5 443.9

TAK-2 14037964.11 2444506.75 447.99 4.3 443.7 Edge of tunnel roof not encountered

TAK-3 14038558.26 2444662.05 446.84 3.0 443.8

Orange utility cable encountered running north-south above tunnel roof

TAK-4 14038526.76 2444675.59 447.65 3.9 443.8

Edge of tunnel roof encountered 0.7 feet east of stake

TAK-5 14039445.35 2444920.01 459.82 -- --

Tunnel roof not encountered to total depth of 8.8 feet

TAK-6 14039475.47 2444965.46 456.43 4.0 452.4

TAK-7 14039444.68 2444958.71 456.63 5.9 450.7 Edge of tunnel roof not encountered

TAK-7A Offset 3 feet east of TAK-7 -- 5.3 -- Edge of tunnel roof not encountered

* Elevations are in units of feet and referenced to mean sea level (msl) datum.

APPENDIX

LIMITATIONS OF REPORT

This report has been prepared on behalf of and for the exclusive use of the client for specific application to the named project as described herein. If this report is provided to prospective contractors, the client should make it clear that the information is provided for factual data only and not as a warranty of subsurface conditions included in this report.

Geotechnology has attempted to conduct the services reported herein in a manner consistent with that level of care and skill ordinarily exercised by members of the profession currently practicing in the same locality and under similar conditions. The data and conclusions contained in this report are professional opinions. No other representation, expressed or implied, is included or intended.

The field exploration methods used indicate subsurface conditions only at the specific locations where samples were obtained, only at the time they were obtained, and only to the depths penetrated. Discrete sampling cannot be relied on to accurately reflect natural variations in stratigraphy that could exist between sample locations and/or intervals.