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2-12 Forward Composting Facility SWT Engineering Report of Composting Site Information - August 2019January 2022 z:\projects\allied waste\forward\resource recovery facility\5 yr permit rvw 2019-2020\rcsi 2019\text\sec 2.doc EMCON Associates in 1972. EMCON drilled a total of 17 borings ranging in depth from 38 feet to 178 feet. The locations of the EMCON boreholes are shown on the Exist ing Conditions Plan (Drawing 1) of that report. Another subsurface investigation was performed by InsituTech in 1987 using Cone Penetration Testing (CPT) in the WMU E area. The exact locations of the CPTs were, unfortunately, not surveyed by InsituTech. The subsurface investigation was performed by CH2M HILL in 1992; it consisted of four soil borings drilled in April and May, 199 2. The Existing Conditions Plan (Drawing 1) of that report shows the approximate location of these four borings, designated as BH -1 through BH-4. Pitcher Drilling Company of Palo Alto, California, was subcontracted to drill the soil borings. CH2M HILL personnel specified the locations, depths of borings, and sampling intervals and observed the drilling and sampling operations. All borehole logs available for the site are included as an appendix in that report . The CH2M HILL borings were 4 -7/8-inch diameter and extended to depths ranging from 43 to 102 feet. The borings were advanced using mud rotary drilling methods with a truck - mounted Failing 750 drill rig. As each boring was completed, the hole was grouted to the surface using a "neat" cement grout. The borings were grouted from the bottom upward using a 2-inch drill pipe as a tremie. Relatively undisturbed samples were obtained using a 3 -inch outside diameter Shelby tube sampler (ST samples) or Pitcher Barrel sampler (PB samples). The Pitcher Barrel sampler was used to obtain samples of very stiff clay where the Shelby tubes could not be pushed. This sampling was performed in general accordance with procedures for Thin-Walled Tube Sampling of Soils as described by the American Society of Testing and Materials (ASTM), Standard D 1587. Disturbed soil samples were obtained from the borings using a 2 -inch outside diameter split -spoon sampler, driven as described for the Standard Penetration Test (SPT), ASTM Standard D1586. Soil recovered during the drilling program was visually classified by a CH2M HILL engineer in general accordance with ASTM D2487 and D2488. The soil names on the boring logs ref lect these ASTM standards. Pocket penetrometer tests were conducted on most cohesive samples. Samples were then prepared for storage by placing representative portions in plastic bags or by sealing the sampling tube with plastic cap and tape. Sample desc riptions, blow counts recorded during the SPT, and other relevant information were recorded on the soil boring logs. Selected soil samples obtained by CH2M HILL from its subsurface investigation were tested in the laboratory by Harding Lawson Associates (HLA) of Concord, California. Index tests performed by HLA included determining the liquid limit, plastic limit, and moisture content of the selected samples. Engineering property tests performed included Unconsolidated Undrained (UU) triaxial compression and consolidation tests. Detailed results of the tests performed are included in the Stability and Settlement Analysis of that report . The soil encountered during the CH2M HILL field investigation generally consists of interbedded layers of sand, silt, and lean clay. The cohesive materials are generally of very stiff to hard consistency. The cohesionless materials can be characterized as dense to very dense. The soil deposits at the site were found to be heterogeneous and laterally and vertically discontinuous. Based on the four soil borings performed for this geotechnical exploration, the subsurface soils at the site can be divided into six general layers of interest.