2012 NGWA Ground Water Summit: Innovate and Integrate

Flexible Liner Special Utility for Karst Formations

Wednesday, May 9, 2012: 1:50 p.m.
Royal Ballroom E (Hyatt Regency Orange County)
Carl Keller, Flexible Liner Underground;

Abstract

Karst formations present special difficulties for site characterization.  The high flow rates, large open flow channels, the difficulty of grouting casing are only a few of the problems.  The relatively new use of flexible liners for sealing of boreholes, measurement of flow paths intersecting the boreholes, and multi-level sampling and head measurements takes advantage of a unique set of liner attributes.  The first advantage is the use of the continuous liner to seal the entire borehole instead of discrete packers, a sealing grout, or other fill outside of a traditional casing.  A second advantage is the ability to measure the transmissivity distribution of very fast flowing boreholes while installing a sealing liner in order to prevent contamination propagation due to an open borehole.  Another advantage is the fact that all the water in the borehole is inside the liner and the multi-level samples are drawn directly from the formation. These characteristics have been tested in a wide variety of karst sites in the USA and Canada.  Those experiences have been very useful to refinements of the flexible liner methods in design and procedures to deal with the extremes of karst situations.  Those refinements are stronger fabrics, eversion aids through caverns, high volume water flow controls for transmissivity profiling, formation head data collection after transmissivity profiling, and sometimes a grout fill of the liner after an installation of a multi-level system.  Whereas sealing liners and multi level systems are practical in holes with more than 100 gallons/min. vertical flow rates, transmissivity profiling in such high flow conditions has limited resolution.  Details of that experience and the refinements are presented in this paper.  The problem of drilling of the initial borehole still remains.