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LANDFILL LEAKS
Presentation By Dennis E. Williams, Ph.D.

Before The Board of Supervisors of San Bernardino County Madame Chair and Honorable Supervisors - My presentation today will focus on the following issues:
1. Quantity And Quality Of Ground Water Available In The Cadiz Valley Area

2. Ground Water Flow Directions And Rates

3. Probable Impacts Of The Bolo Station Landfill On Ground Water Development
- Leakage of leachate into ground water is inevitable. It will result from inherent leaks in the liner system
- Ground water contamination may result from leakage of small amounts of leachate. TCE is a carcinogen and one of the volatile organic compounds typically found in landfill leachate. It would take less than 4 drops of TCE mixed with the water in an average sized swimming pool (20,000 gallons) to render the water undrinkable (in accordance with drinking water standards).

Documented Cases Of Modern Landfill Liner Leakage:
Over the past several years, I have had extensive project experience with landfills and landfill liners of all types. I have conducted research on landfill liners and siting of landfills in Southern California. As part of
this research I have investigated documented cases in the scientific literature, of modern composite landfill liner leakage.

Based on the scientific literature, it is well documented that landfill liners will eventually leak. Geomembrane-lined landfills are a relatively new technology, and as a result, the number of documented cases through double-lined landfills is still being quantified. Holes in geomembranes, especially along seams, are the most immediate mechanism for leakage. My literature research identified at least 34 documented cases of leakage through modern landfill liner systems.

Double-lined landfill liner systems, such as that proposed for the Bolo Station Landfill, are too new for quantification of secondary liner leakage. State officials with the divisions of solid waste of the departments of environmental services of a number of U.S. states were contacted regarding experience with liner leakage. According to those officials, at least nine landfill facilities (mostly double-lined) exhibited leakage through the primary liner. Several of these officials also explained that there is currently no reliable method of assessing if leakage is occurring through the secondary liner.

Based on the literature review and contact with regulatory agencies, leakage through the primary liner of these modern-lined facilities has been, and is occurring. Authorities also agree, that if leaks occur in primary liners, leaks are expected to occur in secondary liners as well. The following is a discussion of some of those documented cases and studies.  1. Daren Laine (1989), a member of the Southwest Research Institute, authored a paper presenting the results of an investigation of 61 new or in-service geomembrane-lined waste storage facilities using the electrical leak location method. Approximately 92% of the facilities tested were HDPE geomembranes ranging in thickness from 60 mil to 100 mils.

He discovered that leaks were found in every liner except those at three smaller facilities. A total of 1,409 leaks were located at the 61 sites surveyed, ranging from 0.3 to 5 leaks per 10,000 square ft, with an average of 3.2 leaks per 10,000 square ft. Leaks were detected in both the parent material and the seams. 87% of the leaks detected were in the seams with the remaining 13% in the parent material.

Personal communication with Mr. Laine revealed that if leaks occur in the primary liner, one can expect leaks in the secondary liner. These leaks can be as high as 20-50 per acre. Furthermore, he explained the problem with the secondary liner is that it is extremely difficult to test for leaks once landfill operation begins, and that in the cases he has seen, nobody wants to know if the secondary liner is leaking.

2. A paper authored by Bonaparte and Gross (1990) summarized the field data collected regarding flow of liquid from the leakage detection layers of double-liner systems at 23 double-lined landfills and 7 surface impoundment facilities. There are four different types of facilities, ranging from Group I to Group IV. Group I and II facilities are constructed with a geomembrane top liner and a geonet (Group I) or sand (Group II) leakage detection layer. Group III and IV facilities are constructed with composite top liners and geonet (for Group III) or sand (for Group IV) leakage detection layers.

Leakage was detected in the leakage detection layer of all sixteen Group I and II type landfills studied. And with one exception, all of the Group III landfill cells exhibited flows from their leakage detection layers. Leakage was detected in the leakage detection layer in nine of the eleven Group IV facilities.

The leakage was attributed to top liner leakage. The seven cells of Group I exhibited top liner leakage ranging from 0.5 to 27 gallons per day per acre (gpd/acre), with maximum flow rates [usually following storm events] of up to about three times the average values. The liner leak rates from the nine Group II landfill cells ranged from 0.5 to 20 gpd/acre, with maximum flow being up to ten times larger than the average values. The paper summarizes that "...properly constructed geomembrane top liners (Group I and II) that have undergone CQA (construction quality assurance) cannot consistently limit top liner leakage to a value of less than 5 gpd/acre."

Another important statement of this study was as follows: "Based on the data in this study, an action leakage rate of 50 lphd [.5 gpd/acre] is too restrictive and presents a performance standard that, if promulgated by US EPA, frequently will not be met by facilities that were constructed to present standards with rigorous third-party CQA programs. An action leakage rate of 200 lphd [2.0 gpd/acre] appears to be reasonable for landfills that have been constructed using rigorous third-party CQA programs." (p. 71). 

This study pointed out twenty cases of double-lined landfills, all with "state of the art construction for their time," and all which leak. 

3. The next paper, also by Gross and Bonaparte (1990), documented two more
cases of modern landfill liner leakage.

Landfill A (actual name not given) is a double-lined landfill made up of three cells, and consisted of a sand leachate collection layer, geomembrane top liner, geonet leakage detection layer, and composite bottom liner. Landfill A exhibited high leakage rates through the top liner immediately following construction due to high initial heads on the liner. At 21 to 33 months after construction, the average measured top liner leakage rate from cells 1 and 2 ranged from 1.7 to 4.6 gpd/acre.

Landfill B was a double-lined landfill made up of four cells, and consisted of a sand leachate collection layer, geomembrane top liner, sand leakage detection layer, and composite bottom liner. Potential sources of leakage from this configuration were top liner leakage, construction water, compression water, and consolidation water. Following closure of Cell 1, no flow was observed until about 46 months after construction, when a small sustained flow averaging 2 gpd/acre began. The average recorded flow rate
increased to 13 gpd/acre by 52 months after construction. Investigation of the situation led to the conclusion that the flow was due to leakage through a hole that developed in the geomembrane at the leachate collection pipe penetration.

4. The next study by Giroud (1989) discussed several examples of the detection of leaks in double-lined landfills. In one case, the top liner of a landfill exhibited a total leakage rate of 250 gpd [unspecified area]
through the geomembrane top liner when the landfill was filled with 6 inches of water. The authors calculated that a 4 mm diameter circular hole could have been the source of this leakage rate. According to the authors, there is no guarantee that these defects will not occur.

In another case, one seam defect was detected every 9 meters (30 ft) of seam length in a large landfill with a double liner. The scientific literature is filled with cases of double-lined, modern landfills which have leaked. And although the proposed liner system for the Bolo Station Landfill uses "state of the art technology" and is superior to the Subtitle D and California standards for liners, similar liners have only been tested in landfills for approximately 10 years. Long-term performance of the system has not been determined. History has shown that the liner cannot possibly be guaranteed to prevent leakage in the future. Construction defects, installation procedures, as well as long-term aging and degeneration of liner materials is certain for all landfill liner systems, including the one proposed for the Bolo Station Landfill.

REFERENCES:
Line, D.L., and Miklas, M.P., 1989, Detection and Location of Leaks in
Geomembrane Liners Using an Electrical Method: Case Histories, 10th
National Superfund Conference, November 27-29, 1989, Washington D.C.

Bonaparte, R. and Gross, B.A., 1990, Field Behavior of Double-Liner Systems
in Waste Containment Systems: Construction, Regulation, and Performance:
ASCE Geotechnical Special Publication No. 26, November 1990, pp. 52-83.

Gross, B.A., Bonaparte, R., and J.P. Giroud, 1990, Evaluation of Flow from
Landfill Leakage Detection Layers: Proceedings Fourth International
Conference on Geotextiles, Volume 2, The Hague, June 1990, pp. 481-486.

Giroud, J.P. and Bonaparte, R., 1989, Leakage Through Liners Constructed
With Geomembranes - Part I, Geomembrane Liners: Geotextiles and
Geomembranes, Volume 8, pp. 27-67.