GSET designed a remediation program for Keystone Sanitary Landfill, Inc. in assessment of potential
surface impacts due to subsurface subsidence prior to construction of the liner system.  This requirement existed due to the area having been previously deep mined for the purposes of anthracite coal extraction.

Based upon the results of detailed subsidence analysis studies, the subsidence event most

problematic to the liner system was localized settlements resulting from collapsed subsurface voids,

which reflect to the surface.

In order to mitigate any potential impact, GSET developed a program for all openings and collapsed zones

encountered by method commonly known as flushing using a cementitious grout mixture.

The remediation program significantly reduced the void space and subsequently reduced the span

required from the overlying rock.

This program was designed and established in conjunction with the Pennsylvania Department of Environmental Protection in order to protect public interest by ensuring landfill liner integrity.