Cal. Code Regs. Tit. 23, div. 3, ch. 15, art. 10, app I
[FN1]
Presented by David Anderson and Gordon Evans of K. W. Brown and Associates as part of the Soil Liners workshop, Permit Writers Training Program, conducted by EPA in San Francisco, California, November 14-17, 1983.
There is currently no standard scheme for evaluating clay liner-leachate compatibility. Following is a suggested step-by-step method for evaluating compatibility.
Step 1: Obtain Representative Waste Samples
Guidance
The first step in analyzing waste-liner compatibility is to obtain a representative sample of the waste to be stored. If any liquids are present in the waste, make sure that the liquids do not drain out of the waste. The sample must contain these liquids to adequately indicate waste liner compatibility.
Method
Several methods for obtaining samples of hazardous wastes are discussed in Section One of Test Methods for Evaluating Solid Waste (EPA, 1982b). Data supplied on the wastes should include the following:
a. EPA Hazardous Waste Numbers (D, F, and K numbers)
| ___________________________ | ___________________________ | ___________________________ | |
| ___________________________ | ___________________________ | ___________________________ | |
| ___________________________ | ___________________________ | ___________________________ |
b. Physical Class of Waste (aqueous-inorganic; aqueous-organic; organic, or solid, sludge, or slurry) Aqueous-inorganic (AI) and aqueous-organic (AO) are classes of waste in which water is the solvent (predominant liquid), and the solutes are mostly inorganic and organic, respectively. Organic (O) is the class of waste in which the predominant liquids are organic, and the solutes are mostly other organic chemicals dissolved in the organic solvent. Solids, sludges, and slurries (S) are wastes high in solids such as tailings, settled matter, or filter cakes.
c. Waste Stream Description (describe the production and waste treatment processes from which the waste stream is generated)
d. __________ Percent Solids (wet weight basis) (determine by drying waste at 10°C for 24 hours)
Step 2: Extract Primary Leachate
Guidance
The primary leachate is the liquid that can be extracted from the waste. It is collected and used to evaluate liner compatibility with liquids present in a waste. If there is more than one distinct immiscible phase in the primary leachate, collect enough of each phase (approximately 5 liters per primary leachate phase) to perform the compatibility testing with each phase.
Method
The primary leachate is extracted from the waste by vacuum filtration at 25°C and should be measured as a percentage of the total waste on a wet weight basis. Attach a large capacity porcelain buchner funnel to a large capacity sidearm flask. Place a rapid flow rate, glass fiber filter circle in the buchner funnel. Wet the filter with a few drops of water, and load the buchner funnel with fresh waste. Connect the flask to an aspirator pump and apply a vacuum to the waste for five minutes or until most of the liquids are removed from the waste. Remove the solids from the buchner funnel, place a clean filter circle in the funnel, wet the filter as before, and reload the funnel with fresh waste. Repeat the above process until sufficient primary leachate has been collected for testing (approximately five liters). If no liquids are extractable from the waste, proceed with step three.
Step 3: Extract Secondary Leachate
Guidance
The secondary leachate is an aqueous extract of the waste. It is collected and used to evaluate liner compatibility with leachate generated by water percolating through the waste.
Method
The secondary leachate is collected by thoroughly mixing the waste with just enough water to obtain the consistency of a saturated paste. (A saturated paste should be thick enough so that the waste barely flows together into a hole made in the paste with a spatula). Filtrate collected from vacuum filtration of the saturated paste is the secondary leachate to be used in the liner-leachate compatibility tests.
Secondary leachate can be extracted from the saturated paste in the same manner in which primary leachate is removed from liquid-bearing wastes. Enough saturated paste should be subjected to vacuum filtration to collect approximately five liters of secondary leachate. Do not reuse waste samples for the collection of additional leachate, as this would result in an excessively diluted leachate.
Step 4: Analyze Primary Leachate
Guidance
If the waste contained a primary leachate, it should be analyzed to establish the type and concentration of the organic liquids present. Some primary leachate may contain two distinct immiscible phases. It is advisable to analyze each phase separately. Subsequent routine analysis should be performed to assure that leachate composition has not changed in a way that would affect liner performance. While the initial analysis should be definitive with regard to the liquids and solutes present in the leachate, the routine analysis need only confirm that leachate composition has not appreciably changed.
Method
Permit applicants may be able to find analyses of similar wastes in company files, state regulatory agency files, or in the analyses of wastes compiled by EPA (EPA, 1980a; EPA, 1980b). It should be noted, however, that it is leachate analyses that will ultimately be needed for use in characterizing liner-leachate compatibility. The following information on the primary leachate should be collected.
a. __________ percent Filtrate (wet weight basis) that would be removed from waste by vacuum filtration (at 25°C)
b. Predominant liquid constituents as a percentage of total primary leachate (filtrate) (indicate to 0.1 percent)
| __________ percent | ___________________________Water |
| __________ percent | ___________________________ |
| __________ percent | ___________________________ |
| __________ percent | ___________________________ |
| __________ percent | ___________________________ |
c. Predominant solutes as gL-1 of total primary leachate (indicate to 0.1 gL-1)
| __________ gL-1 | ___________________________ |
| __________ gL-1 | ___________________________ |
| __________ gL-1 | ___________________________ |
| __________ gL-1 | ___________________________ |
| __________ gL-1 | ___________________________ |
A two-step method can be used to analyze primary leachate. First, fractional distillation can be used to separate and quantify the liquids according to the temperature at which each fraction is removed from the bulk liquid. The mass of each fraction as a percent of the total primary leachate can then be determined gravimetrically. Secondly, each fraction obtained can be identified by gas chromatography and, if necessary, confirmed by mass spectrometry.
These methods are discussed in Section Eight of Test Methods for Evaluating Solid Waste (EPA, 1982b). After these initial detailed analyses, subsequent routine analyses may be limited to the first step of the method.
Primary Leachate pH = ___________________________
Primary Leachate EC = ___________________________
The pH of the primary leachate can be determined electrometrically using a saturated paste and a glass electrode in combination with a reference potential or a combination electrode. The electrical conductivity (EC) of the primary leachate is determined by using a saturated paste extract and a self-contained conductivity meter, such as a wheatstone bridge-type or equivalent.
Step 5: Analyze Secondary Leachate
Guidance
The secondary leachate is an aqueous-based liquid and may have the following types of solutes: acids, bases, salts, and organic chemicals. This leachate must be analyzed to determine the concentration of the solutes.
Method
The following information is needed to characterize secondary leachate. Some of the information may be collected by methods that are similar to those used for the primary leachate.
a. __________percent Filtrate (wet weight basis) that could be removed from the waste made into a saturated paste by addition of distilled water.
b. Predominant solutes as gL-1 of total primary leachate (indicate to 0.1 gL-1)
| __________ gL-1 | ___________________________ |
| __________ gL-1 | ___________________________ |
| __________ gL-1 | ___________________________ |
| __________ gL-1 | ___________________________ |
| __________ gL-1 | ___________________________ |
c. Secondary Leachate pH = ___________________________
Secondary Leachate EC = ___________________________
The types and concentration of the solutes present in the leachate can be determined as follows:
Salts may be initially characterized by atomic absorption spectrophotometry and electrical conductivity. The method for measuring EC is discussed above and the methods for atomic absorption spectrophotometry for various inorganics are found in Section Seven of Test Methods for Evaluating Solid Waste (EPA, 1982b). Subsequent routine analysis may usually be limited to EC unless this measurement indicates the leachate is significantly different from that originally analyzed.
Acids and Bases may be satisfactorily characterized by measuring the pH of the leachate using a standard pH meter and electrodes, as described for the primary leachate.
Organic Solutes can be quantified by determining the total organic carbon in the leachate by converting organic carbon in the sample to carbon dioxide (CO2) by catalytic combustion or wet chemical oxidation. The CO2 formed can be measured directly by an infrared detector or converted to methane (CH4) and measured by a flame ionization detector (EPA, 1979). The amount of CO2 or CH4 is directly proportional to the concentration of carbonaceous material in the sample. If low molecular weight organics are present in the leachate at concentrations of parts per thousand or greater, it may be advisable to use the fractionation and analysis technique described above for the primary leachate. For more dilute solutions, it may be necessary to extract the organic constituents and analyze them by liquid chromatograpy and gas chromatography. These are discussed in Section Eight of Test Methods for Solid Waste (EPA, 1982b).
Step 6: Characterize the Clay Liner Guidance
Characterization should include the determination of effective pore volume and permeability of the clay liner.
Method
Characterization of a clay liner will not, in itself, reveal if a liner has all the appropriate properties to prevent failure. This characterization can, however, establish the baseline permeability and effective pore volume values with a standard aqueous leachate (0.01 N CaSO4) and nonattenuated ion (bromide), respectively. These baseline values can be compared with the values obtained with the leachates of a waste. Suitable methods for analyzing soil physical properties are available in the latest edition of ASTM Standards (part 19: Natural Building Stones; Soil and Rock), in Black (1965), or in most soil testing manuals. Determination of bromide breakthrough can be accomplished by using a bromide selective electrode to analyze permeameter outflow. The following information should be determined for the clay liner.
a. Particle size distribution and clay minerology
1. __________percent Sand ( >50 µm, dry wt. basis)
2. __________percent Silt (50-2.0 µm, dry wt. basis)
3. __________percent Clay ( <2.0 µm dry wt. basis)
4. __________percent of Clay that is coarse (2.0-0.2 µm, dry wt. basis)
5. Predominant coarse Clay minerals
__________ percent ___________________________
__________ percent ___________________________
__________ percent ___________________________
6. __________percent of Clay that is fine (0.2 µm, dry wt. basis)
7. Predominant fine Clay minerals
__________ percent ___________________________
__________ percent ___________________________
__________ percent ___________________________
b. Physical properties
1. __________ g cm-3-particle density
2. __________ percent in-place (as compacted) water content (dry wt. basis)
3. __________ g cm-3-place (as compacted) density (dry wt. basis)
4. __________ percent pore space (percent of total liner volume)
5. Permeability to an aqueous solution of 0.02 N CaSo4 or CaCL2 after percolation of:
0.5 pore volume ________________________________________ cm/sec
1.0 pore volume ________________________________________ cm/sec
1.5 pore volume ________________________________________ cm/sec
2.0 pore volume ________________________________________ cm/sec
6. Pore volume values for Bromide breakthrough
__________percent Bromide at 0.1 pore volume
__________percent Bromide at 0.2 pore volume
__________percent Bromide at 0.3 pore volume
__________percent Bromide at 0.4 pore volume
__________percent Bromide at 0.5 pore volume
__________percent Bromide at 0.6 pore volume
__________percent Bromide at 0.7 pore volume
__________percent Bromide at 0.8 pore volume
__________percent Bromide at 0.9 pore volume
__________percent Bromide at 1.0 pore volume
The permeability of the clay liner should first be evaluated using a standard leachate (such as 0.01 N CaSO4 or CaCl2). After the permeability has stabilized, the effective pore volume can be estimated by spiking the standard leachate with bromide and monitoring the breakthrough of bromide in the permeameter outflow. Assuming that a clay liner is presaturated with clean water, nonattenuated leachate constituents (e.g., bromide) will be present in the outflow from the permeameter after passage of leachate equal to approximately 50 percent of the volume represented by one effective pore volume.
Step 7: Determine Compatibility of the Proposed Clay Liner with the Expected Leachates
Guidance
A substantial body of data suggests that concentrated organic liquids may significantly degrade the performance of clay liners; consequently, clay liner-waste leachate compatibility tests should be conducted to verify that leachates will not move beyond the clay liner during the active life of the facility. These organic liquids include polar, nonpolar, basic, and acidic organic liquids. In all probability, organic liquids will degrade clay liner performance to an extent that these liners will have either a short lifetime or a large thickness requirement. There are also substantial data indicating that either strong aqueous salt, acidic, or basic solutions may degrade clay liner performance. It should be noted, however, that acids and bases can be neutralized, and certain treated clays may resist degradation upon exposure to many strong aqueous salt solutions.
Basic and nonpolar organic liquids have shown the potential to significantly decrease the effective pore volume of clay liners. Polar organic liquids appear to degrade clay liner permeability to a greater extent than they initially degrade effective pore volume. There is substantial evidence that a wide range of organic liquids may degrade clay liner effectiveness.
Method
The permeability and lowest pore volume at which waste constituents appear in permeameter outflow should be determined with both the primary and secondary leachates of the wastes if these solutions are appreciably different. These values should be compared with the baseline values previously determined to see if the leachates are likely to degrade the ability of a clay liner to meet the leachate containment performance standard. Whenever either organic liquids or concentrated solutes are present in leachates, it is suggested that clay liners be tested by passing at least two full pore volumes of the leachates through the liner. If the primary leachate of a waste contains two or more immiscible phases, it is advisable to test each phase separately and to test the phases sequentially on the same clay core. The leachates used in the permeability tests should be at the highest concentration at which they would ever be while in contact with the clay liner. For constant head permeability tests, the following equation may be used:
K = V/AtH
where:
K = permeability constant (cm sec-1);
t = time (sec);
v = volume of leachate passed through the soil (cm3);
A = cross sectional area of liquid flow (cm2); and
H = hydraulic gradient or (h + L)/L where:
h = hydraulic head (cm of H2O) and
L = length of soil column (cm)
For failing head permeability tests, the following permeability equation can be used (Olson and Daniel 1981):
where: K = permeability constant (cm sec-1)
a = cross sectional area of the buret (cm2)
A = cross sectional area of the soil (cm-2)
L = length of the soil (cm)
t = elapsed time from 5(0) to t(1)(sec)
h(0) = height of water in standpipe above the discharge level at t(0)(cm)
h(1) = height of water above the discharge level at time t(1)(cm)
This equation can be arranged as follows:
Thus, the slope of the line obtained by plotting ln hydraulic head versus time may be used to determine the permeability constant:
Permeability (k) should be plotted along the Y-axis, while the cumulative pore volume at which each permeability is obtained should be plotted along the X-axis. Incremental pore volumes are obtained by dividing the volume of leachate (v) by the total pore volume of the compacted soil specimen used in the test. Total pore volume of a specimen is obtained as follows:
total pore volume = pAL
where porosity (p) is multiplied by the total volume (AL) of the soil specimen. Porosity is determined as follows:
where the bulk density, or unit weight (BD) is divided by the particle density (Gs).
If elevated hydraulic gradients are to be used and there is a failure in the clay liner being tested, a rough estimate of the time to failure can be made by rearranging Darcy's law so that time is isolated as follows:
where: ti1= laboratory test time increment (sec)
H1 = hydraulic gradient used in the laboratory (unitless)
To convert laboratory time to the corresponding time in the field, the maximum hydraulic gradient that will occur in the field (H2) may be substituted for the value used in the laboratory (H1) as follows:
where: ti2= field time increment (sec)
H2= maximum hydraulic gradient in the field (unitless)
The field time values obtained from the beginning of the test until waste constituents appear in the permeameter outflow should be summed together. This total time value should then be multiplied by the ratio of the field liner thickness to the laboratory liner thickness to arrive at the useful life of the clay liner as follows:
where: T = useful life of the clay liner (sec)
n = time increment where leachate constituents are first detected permeameter outflow
Y = (thickness of field liner (cm))/(thickness of laboratory liner (cm))
a. Permeability to primary leachate (where two or more distinct immiscible primary leachates are present, test the solutions separately).
| 0.1 pore volume ________________________________________ cm/sec | ||
| 0.2 pore volume ________________________________________ cm/sec | ||
| 0.3 pore volume ________________________________________ cm/sec | ||
| 0.4 pore volume ________________________________________ cm/sec | ||
| 0.5 pore volume ________________________________________ cm/sec | ||
| 0.6 pore volume ________________________________________ cm/sec | ||
| 0.7 pore volume ________________________________________ cm/sec | ||
| 0.8 pore volume ________________________________________ cm/sec | ||
| 0.9 pore volume ________________________________________ cm/sec | ||
| 1.0 pore volume ________________________________________ cm/sec | ||
| 1.1 pore volume ________________________________________ cm/sec | ||
| 1.2 pore volume ________________________________________ cm/sec | ||
| 1.3 pore volume ________________________________________ cm/sec | ||
| 1.4 pore volume ________________________________________ cm/sec | ||
| 1.5 pore volume ________________________________________ cm/sec | ||
| 1.6 pore volume ________________________________________ cm/sec | ||
| 1.7 pore volume ________________________________________ cm/sec | ||
| 1.8 pore volume ________________________________________ cm/sec | ||
| 1.9 pore volume ________________________________________ cm/sec | ||
| 2.0 pore volume ________________________________________ cm/sec |
b. Permeability to secondary leachate
| 0.1 pore volume ________________________________________ cm/sec | ||
| 0.2 pore volume ________________________________________ cm/sec | ||
| 0.3 pore volume ________________________________________ cm/sec | ||
| 0.4 pore volume ________________________________________ cm/sec | ||
| 0.5 pore volume ________________________________________ cm/sec | ||
| 0.6 pore volume ________________________________________ cm/sec | ||
| 0.7 pore volume ________________________________________ cm/sec | ||
| 0.8 pore volume ________________________________________ cm/sec | ||
| 0.9 pore volume ________________________________________ cm/sec | ||
| 1.0 pore volume ________________________________________ cm/sec | ||
| 1.1 pore volume ________________________________________ cm/sec | ||
| 1.2 pore volume ________________________________________ cm/sec | ||
| 1.3 pore volume ________________________________________ cm/sec | ||
| 1.4 pore volume ________________________________________ cm/sec | ||
| 1.5 pore volume ________________________________________ cm/sec | ||
| 1.6 pore volume ________________________________________ cm/sec | ||
| 1.7 pore volume ________________________________________ cm/sec | ||
| 1.8 pore volume ________________________________________ cm/sec | ||
| 1.9 pore volume ________________________________________ cm/sec | ||
| 2.0 pore volume ________________________________________ cm/sec |
c. Pore volume values for breakthrough to two mobile waste constituents (waste constituent in eluate as percent of constituent inleachate).
1. Constituent No. 1
| __________percent of 0.1 pore volume | __________percent at 1.1 pore volume |
| __________percent of 0.2 pore volume | __________percent at 1.2 pore volume |
| __________percent of 0.3 pore volume | __________percent at 1.3 pore volume |
| __________percent of 0.4 pore volume | __________percent at 1.4 pore volume |
| __________percent of 0.5 pore volume | __________percent at 1.5 pore volume |
| __________percent of 0.6 pore volume | __________percent at 1.6 pore volume |
| __________percent of 0.7 pore volume | __________percent at 1.7 pore volume |
| __________percent of 0.8 pore volume | __________percent at 1.8 pore volume |
| __________percent of 0.9 pore volume | __________percent at 1.9 pore volume |
| __________percent or 1.0 pore volume | __________percent at 2.0 pore volume |
2. Constituent References:
Black, C. A. (ed.) (1965). Methods of Soil Analysis, Part 1. Physical and Mineralogical Properties Including Statistics of Measurement and Sampling. Am. Soc. Agron., Madison, Wisconsin. 770p. EPA. (1979). Methods for Chemical Analysis of Water and Wastes. EPA 600/4-79-020 (PB 297-686/8BE).
EPA. (1980a). Listing of Hazardous Waste. RCRA, Office of Solid Waste, Washington, D. C. Section 261.20 through Section 261.21. May 19, 1980.
EPA. (1980b.) Hazardous Waste Land Treatment. Written for U.S. EPA by K. W. Brown and Associates, Inc. EPA, Cincinnati, Ohio. SW-874.
EPA. (1982b). Test Methods for Evaluating Solid Waste. U.S. EPA Office of Solid Waste and Emergency Response. Washington, D. C. SW-846.
Cal. Code Regs. Tit. 23, div. 3, ch. 15, art. 10, app I