34 NEW LANDFILL TECHNOLOGY FOR AN OLD
LANDFILL'S PROBLEMS: A CASE STUDY
Timothy A. Bannister, Hydrogeology Department Manager
Victoria L. Warren, Senior Hydrogeologist
EMCON
Indianapolis, Indiana 46256-3918
INTRODUCTION
There are presently 111 solid waste sites in Indiana where groundwater is being monitored on
a regular basis. Solid waste regulations passed in 1989 required leachate collection systems
(LCS) in all new landfills. Of the 111 monitored solid waste facilities, only about 20 of them
have an LCS, either built into the original design or retrofitted into an old design. Furthermore,
42 solid waste sites are presently under Phase II or assessment monitoring (suspected of causing
groundwater contamination) and 8 are in corrective action with confirmed groundwater contamination. It is significant that none of these sites with suspected or confirmed groundwater contamination have leachate collection systems.
It has been the authors' experience that many old landfills without LCSs have problems with
leachate breakouts on sideslopes. However, these same landfills are found to have good natural
base liners and a low chance of contaminating groundwater. On the other hand, if an old landfill
has no LCS, yet is not experiencing leachate breakouts on the sideslopes, the base liner may be
suspect and leachate may be exiting the landfill bottom and into underlying groundwater.
This paper presents a case study of an old landfill that, until recently, had no leachate control
system. The landfill had experienced significant leachate breakouts on sideslopes except for one
particular corner of the fill area.
SITE DESCRIPTION AND PROBLEM INVESTIGATION
The subject site is located in glacial terrain of northern Indiana. Specifically, the site is situated
on a glacial till plain which is underlain by approximately 120 feet of unconsolidated clays, silts
and coarser grained intervals that serve as a water supply aquifer. The facility plan view is shown
on Figure 1. The old fill area is approximately 40 acres in size. Although it had, until recently, no
leachate collection system, all previous drilling investigations indicated the site had a good natural base clay liner.
General groundwater movement at the site is to the northwest. Groundwater monitoring detected low levels of volatile organic compounds in MW-C, located at the northwest corner of the
facility, where there happened also to be no leachate breakouts on the sideslopes. Detailed examination of stratigraphy in that area indicated that abrupt changes in lithology (e.g., from clays to
sands) were common in that portion of the facility.
Subsequent field investigations consisted of first, a seismic refraction survey, followed by borings to the base of waste, and groundwater investigation borings along the facility's western
boundary. The seismic refraction survey indicated an area of the waste approximately an acre or
larger in size that appeared to be underlain by sand as opposed to the barrier clay commonly encountered at the site. Fifteen (15) borings were drilled to the base of waste to determine the nature of soil underlying the waste. Confirming the seismic refraction results, a two-acre area was
discovered where waste was situated directly on sand. Those borings that encountered clay, also
had saturated thickness of leachate on top of the clay liner. Those that encountered sand were
dry.
50th Purdue Industrial Waste Conference Proceedings, 1995, Ann Arbor Press, Inc.. Chelsea. Michigan 48118.
Printed in U.S.A.
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