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HomeMy WebLinkAboutMITIGATIONPRELIMINARY GAS MIGRATION INVESTIGATI©N KERN COUNTY CITY OF BAKERSFIELD LANDFILL November, 1981 Landfill Gas Consultants Brown and Caldwell 1501 N. Boardway Walnut Creek, CA 94596 (415) 937-9010 Engineering Science, Inc. 125 West Huntington Drive P.0. Box 538 Arcadia, CA 91 006 (213) 445-7560 EMCON Associated 90 Archer Street San Jose, CA 95112 (408) 275-1444 Gas Recovery Systems 550 N. Rosemead Blvd. Suite 201 Pasadena, CA 91107 (21 3) 351-9643 Lockman and Associates. 249 East Pomona Blvd. Monterey Park, CA 91 754 (213) 724-0250 Ralph Stone and Company 10954 Santa Monica Blvd. Los Angeles, CA 90025 (213) 478-1501 Raymond Vail and Associates 1410 Ethan Way Sacramento, CA 95825 (916) 929-3323 SCS Engineers 4014 Long Beach Blvd. Long Beach, CA 90807 (213) 426-9544 Technical Management Services, Inc. 16162 Beach Blvd., Suite 308 Huntington Beach, CA 92647 (71 4) 848-5744 Beta Associates 1365 Vander Way San Jose, CA 95112 (408) 295-7483 Index Page List of Figures ii I. Introduction 1 II. Site Description 1-3 III. Field Investigations 4-7 IV. Discussion 7-1 0 V. Conclusions and Recommendations 10-11 Appendix A Test Hole Logs A-1 to A-12 Misc. Section Views A-13 to A-15 i List of Figures 1. Section'Location Map 2.- Plan View of Test Area 3. Section View at Test Line 1 4. Section View at Test Dine 2 5. Section View at Test Line 3 6. Plot - Gas Concentration vs. Distance ii P~liminary Gas Migration Investigation Kern County City of Bakersfield Landfill I. Introduction This investigation was conducted by State Solid Waste Management Board staff members Kerry Jones and Barry McGee under the Board's technical assistance program. The work was requested by the Kern County Public Works Department and the Kern County Environmental Health Department, who are the site operator and the Local Enforcement Agency (LEA) respectively. The intent of the study was to estimate the extent of landfill gas migration from the City of Bakersfield Landfill and to identify any existing hazard to properties adjacent to the landfill. II. Site Description The Bakersfield City Landfill is located in the northeastern section of the City between Panorama Drive.to the south and the Alfred Harrell Highway to the north (see 'Figure 1). Recorda of the RegionaI Water Quality Control Board in- dicate that a portion of the 132 acre landfill site, was used as a burn dump commencing in 1943 and continuing until approximately 1956~ There is visual evidence of a large quantity of burned waste material along the southern land- fill boundary. The limit and depth of this waste material is not known, but may extend into the landfill and beneath the residential property adjacent to the southern landfill boundary. The operation of this facility was changed to sanitary landfilling in 1956. The maximum depth of the landfill is -approximately 130 feet and the maximum age of the waste is approximately 25 years. The upper 30 feet of fill, along the southern boundary appears to be about 4 years old. The areas of major concern with respect to landfill g~s migration are the single family homes lots located on Panorama Drive which border the landfill and the condo- minium properties on a ridge overlooking the landfill property. These areas are shown in Figure 2. All of the potentially i~pacted structures are of frame construction with concrete slab foundations. The rear property line for the nineteen single family lots along Panorama Drive and the easterly property line of the condominium development coincide with the landfill property lin~. The major por- tion of all off-site properties lies at an elevation of 50 to 80 feet above the landfill surface. (See Section Views) Local residents informed us that at least some of the homes were constructed on compacted fill on native material and that, to their knowledge, no burn dump material was located within the limits of the original lot lines. The old burn dump material was partially covered with soil at some time prior to the residential construction. The original lots were approximately 85 feet in width and 130 feet in depth, but were enlarged in depth by the ac- quisition of approximately 80 feet of additional property to the north. Visual observations and discussion with residents indicate that subsidence has occurred, causing ground and concrete cracking and damage to at least two swimming pools, requiring mud jacking and relining. The subsidence was apparently accelerated by water leakage from damaged pools and infiltration of storm and irrigation water. The subsurface conditions causing the subsidence are unknown as are the limits and depths of the burned waste material and earth fill. III. Field Investigations During the week of September 21, 198t, State Solid Waste Management Board staff members Kerry Jones and Barry McGee conducted a preliminary gas migration survey at three general locations in the area of the southern landfill boundary. The field testing consisted of taking combustible gas concentration and gas pressure measurements at various depths at several locations. Test holes were made using a Wacker Model UB 25, gasoline powered hammer, and 1" I.D. steel hand sampling rod, containing a perforated section 2 feet in length. Gas concentration measurements were made using a Gas Tech Model NP204 Combustible Gas Detector and pressure measurements were taken using a Dwyer Magnehelic differential pressure gage with a range of plus or minus 1 inch of water column. The entire length of rod was evac- uated using a hand aspirator prior to taking each gas measurement. Permanent monitoring probes were installed in several of the holes. These,,+probes were of two types,,, one being a /4" short section (9 -) of perforated 1/2 PVC pipe with a 1 polyethylene tubing leading to ground surface, the other a length of 1/4" polyethylene tubing with the bottom 4"~per- forated. Test locations are shown in Figure 2, in plan view, and in section views in Figures 3, 4, and 5. In- dividual test hole and probe data are shown on the logs in Appendix A. Docations R-1 and R-2, tested during site evaluations while conducting the EPA Open Dump Inventory, were placed at the landfill boundary in areas containing burn dump material. These holes were advanced to the 7 foot depth and both read approximately 35% combustible gas concentrations. No probes were installed in these locations. Location 4 is a 4" diameter Iwan Auger hole in native soil 4 feet deep. A probe was installed at this location and no combustible gas was detected. Surface cracks on the land- fill were tested near this location and combustible gas in concentrations up to 26% was detected. Locations 1, la, lb and lc are along the property line between 3636 and 3700 Panorama Drive and var~ from 2 to 132 feet south from the landfill boundary, with #1c in line with the rear wall of the residential structure at 3636. Combustible gas was detected in each test hole with the highest concentrations ranging from 30% in hole 1 to 16% in hole lc. Odorous gas was flowing under pressure from holes 1 and la, but neither odor nor flow was detected in holes lb and lc. Probes were installed on each location. Surface cracks in the rear portion of the lot at 3700 Panorama Drive were also tested and combustible gas in concentrations of 5% was detected~ Visual observations were made of minor cracking in the block wall between 3656 and 3700, major cracks in concrete decking at the swimming pools at 3700 and 3704 and surface 'cracking in the rear of the lot at'3700 Panorama Drive. Locations 2, 2a, 2b and 2c are along the property line between 3704 and 3708 Panorama Drive, with hole 2a 47 feet from the rear of the residential structure at 3708, and 2b and 2c located on landfill property on the extension of that property line. Holes 2b and 2c are on the landfill level at elevation 752~while hole 2 is located above the landfill level at elevation 800~ Combustible gas concentrations in the landfill in 2b and 2c were 52% and 54% respectively. The maximum combustible gas concentrations in holes 2 and 2a were 45% and 23% respectively. Odorous gas was flowing from holes 2,2b and 2c. A sample hole was driven adjacent to hole 2 and a sample was retrieved from the 19 to 23 foot depth. ~The sampled material appeared to be old burn dump residue that was very moist but had no odor of landfill gas. Monitoring probes were placed in 2 and 2a. Surface cracking was observed in the rear portion of 3708 extending onto the property at 3704 Panorama Drive. Testing of the crack, located 15 feet north of hole 2a, produced combustible gas concentrations between 16% and 20% at a depth of 6". Odorous gas was flowing from the crack. Location 3 was at a point on the east property line of 3908 Panorama Drive approximately 25 feet from the landfill boundary and at an elevation of 830 · This hole was advanced to a depth of 28 feet into what appeared to be native soil, and no combustible gas was detected. No probe was installed in this hole because of caving of the hole. IV. Discussion Maximum gas concentration readings observed at each loca- tion are shown in Table 1. Referring to Figure 2 indicates that the lateral extent of documented migration is approx- TABLE~I Test Location Maximum Gas Reading (% Methane) R1 35 R2 35 1 3o la '~ 24 lb 21 lc 16 2 45 2a 23 2b 52 2c 54 3 0 4 0 imately 420 feet. The absenc~ of detectable gas at lo- cations 3' and 4 at the time of the tests' reported here leads to a tentative conclusion that the primary path of gas migration at other locations may be the highly per- meable ash deposit. However, the lack of gas at location may be due in part to the fact that waste deposition in this area has been much more recent and in part to the shallow depth of the probe at this location. Additional monitoring is needed to further assess the lateral extent of migration between points 3 and 4, and to confirm that gas is not present at greater depths at location 4. The maximum distance of gas migration from the refuse deposit observed during this investigation is approximately 260 feet. This distance corresponds to the distance to the rear wall of the house located at 3636 Panorama Drive. A plot of maximum gas concentration versus distance from the fill is shown in Figure 6. Extrapolation of the curves for the two lines of probes indicates that gas may be migrating as far as 350 feet before being diluted below the lower explosive limit. However, further investigation would be needed to confirm this. Some thought was given to the possiblity that the source of methane might be gas generated within the ash deposit as a result of incomplete combustion of organic materials. However, s~veral factors lead'us to believe the gas source is the sanitary landfill and that the ash deposit is the primary pathway for gas migration. First, the sample taken adjacent to probe hole 2 appeared to be primarily soil, glass and metal, rather than decomposing trash. Secondly, the lack of gas at locations 3 and 4 may indicate a low permeability to gas flow through the native soils. Thirdly, the gas pressure and gas readings observed in holes 1 and 2a respectively increased with depth up to a maximum val~e followed by a decrease in value. This may be a result of driving the sampling probe through the ash material into a less permeable material. V. Conclusions and Recommendations The major conclusion reached is that gas is traveling a considerable distance from the landfill and rep?esents a potential hazard to residents adjacent to the site. It is there£ore recommended a program be initiated which will lead to the design and implementation of a gas control system. Due to the complexity of the situation, it is recommended that an engineering consultant with experience in landfill gas control be retained to design and oversee the implementation of such a system. Additional work by the consultant will be needed to obtain information on the extent of the ash deposit and its influence on gas migra- tion at the site prior to system design. The information in this report should be included in a request for pro- pgsals for the recommended work. 5 · ~~ ~.~A~ON' ~/7'Z ~h ...... ~' ss~ ~1 ~ ~m~ ...... ....... .,- k.~ : ~ ~/>- ~Y /o -- 19 - ]~ .. _ ~;'~ --_ ~:~,. i ~ ~. -:_. .. , ., ~l~ ~.~A~ON ~ ~ ~ _ ..... '~ ~-~ ]~ ~ 2~ .... ~'~., xo~ ... - ~. ~ '" _ z~, ~.o~ ,, AtmoSpho~c P~ss. "~ ~ ~ ~E ~/~ DmZ(S) ~ ,,' ~pth % CH~ ~ss~ ~ ~ ~m~ks I ,~ Co~,~-o~,~ . I I 7£o- 7~- 700- r I' I r: r I i i i '1oo 50 0 ~0' Ioo