<p><p><figure id='attachment_3355' style='max-width:715px' class='caption aligncenter'><img class="wp-image-3355 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Overhead photograph of the Pennsylvania Turnpike Service Area where bulk infill grouting used to fill sinkholes that developed." width="715" height="426" /><figcaption class='caption-text'> Pennsylvania Turnpike service plaza. (© 2011 Google)</figcaption></figure></p><p><div><h2>Project Summary/Scope:</h2>Sinkholes developed in the vicinity of three fuel storage tanks at a Pennsylvania Turnpike service plaza. An exploratory/grouting program using a conventional (i.e., sand, cement, water, and bentonite) grout mix was used to seal the subsidence sinkholes and improve the underlying foundation.</p><p>Subsurface Conditions:<strong> </strong>The underlying bedrock, which was composed of limestone, dolomite, quartzite, and quartz schist; had been subject to fracturing and thus increased solutioning in the past. Numerous open channels and soil-filled cavities existed in the bedrock. A small fault was believed to trend through the storage tank site. Rock depths varied from 35 to 65 feet (10.7 to 19.8 m) below ground level.</p><p>Sheet piles were installed in a 41 feet by 36 feet (12.5 by 11.0 m) rectangular area just outside the tank locations. The existing tanks were removed and the area backfilled with 3/8-inch (10 mm) stone. The placement of the crushed stone following installation of the sheet pile walls complicated the drilling procedures since it was then necessary to install drill casing to limit grout flow into the stone which greatly slowed construction.</p><p>During the first two days, exterior grout holes were drilled 10 feet (3.0 m) on center, 2 feet (0.6 m) inside the sheet pile perimeter as a result of a 14-inch (360 mm) wide whaler extending along the interior of the sheeting. Steel casings and PVC tremie pipes were installed into the holes. In the initial boreholes, the outer steel casing was removed leaving only the PVC tremie pipe. The grouting program was initiated 3 days after the holes were drilled using a mix consisting of sand, cement, water, and bentonite (to control shrinkage). To limit grout movement to areas outside that being remediated, calcium chloride was added to the grout (to accelerate set time) introduced into exterior probe holes with excessive grout takes. Grout was mixed in a double-tub mixer and delivered to the grout hole with a single-piston pneumatic pump. Thirty-nine boreholes were drilled for the project. 57 CY (44 m³) of grout was placed for the project.<br><h2>Alternate Technologies:</h2>Foundation alternatives included a reinforced concrete slab, deep foundations, and excavation and fill. The selected foundation technique was to use bulk infill grouting to fill the subsurface karstic voids at a new location then relocate the tanks to remediated area.</p><p><figure id='attachment_3357' style='max-width:480px' class='caption aligncenter'><img class="wp-image-3357 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Grouting plan at the Pennsylvania Turnpike Service Plaza." width="480" height="413" /><figcaption class='caption-text'> Grouting plan. (Fischer and Fischer, 1997)</figcaption></figure><h2>Project Technical Paper:<strong> </strong></h2>Fischer, J.A and Fischer, J.J. (1997). “Investigation and Remediation of Service Plaza Fuel Storage Tanks in Karst.” Proceedings of the 48^th Annual Highway Geology Symposium, University of Tennessee, Knoxville publication E01-1040-008-97, pp 14-23.<br><h2>Date Case History Prepared:</h2>November 2012</p><p></div></p></p>