EIS 1509 Tharbogang Landfill
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EIS 1509 Tharbogang landfill - groundwater assessment and contamination remediation plan. NSW DEPT PRIMARY INDUSTRIES lll~~ ll~~ 1~~ ll 1~~ lll~ ll 1~~l 1~ ll~ AA067862 r I AWL6409/1-BG trh 19 May 2000 Griffith City Council PG Box 485 GRIFFITH NSW 2680 Attention: Mr Peter Higgins T Dear Sir, (T5 RE: THARBOGANG LANDFILL - GROUNDWATER ASSESSMENT AND CONTAMINATION REMEDIATION PLAN Please find herewith our draft report on the hydrogeological assessment and groundwater contamination assessment at Tharbogang Landfill, The report will be finalised when we receive comments from yourselves and/or the EPA. Please do not hesitate to contact Terry Harck in our Sydney office, or the undersigned if you require any further information regarding this report. ehaIf of 7C;FZil~ EOSCIENCES PTY LTD ANTHONY EDWARDS Manager 142 Wicks Road North Rydo NSW 2113 Australia P0 Box 125 North Ryde NSW 1670 Australia Telephone +61 2 9888 7444 Facsimile +61 2 9088 9977 Coffey Geosciences Pty Ltd A0No513335516 Email [email protected] AWL6409/1-BG 19 May 2000 TABLE OF CONTENTS INTRODUCTION OBJECTIVE SCOPE OF WORK GROUNDWATER ASSESSMENT I 4.1 Hydrogeology of Tharbogang Landfill I 4.2 Current Groundwater Users 2 4.3 Monitoring Bores 2 4.4 Monitoring Results 3 4.4.1 Exceedance of Guidelines 5 4.4.2 General Comments 6 DISCUSSION 6 CONCLUSIONS 7 RECOMMENDATIONS GROUNDWATER CONTAMINATION REMEDIATION PLAN 8 8.1 Existing Landfill 8 8.1.1 Leachate Reduction Plan 8 8.1.2 Groundwater Monitoring Plan 8 8.2 Stage 2 Landfill 8 8.2.1 Surface Water Management 9 8.2.2 Leachate Management 9 8.2.3 Groundwater Management 10 TA B LE S Table 1 Summary of Monitoring Bore Drilling Results Table 2 Tharbogarig Landfill Groundwater Analytical Results C:\WINDOWS.000\TEMP\AWL6409-1 bg .Doc AWL6409/1 -BG 19 May 2000 TABLE OF CONTENTS (continued) FIGURES Figure 1 Location of Landfill Figure 2 Location of Monitoring Bores Figure 3 Cross-section Through Monitoring Bores APPENDICES Appendix A Laboratory Reports Appendix B Groundwater Monitoring Analytes C:\WiNDOWS000\TEMP\AWL6409-1 bg.Doc AWL6409/1-BG 19 May 2000 INTRODUCTION At the request of Griffith City Council, Coffey Geosciences Pty Ltd (Coffey) conducted a hydrogeological assessment review of the Tharbogang Landfill, Griffith, NSW (Figure 1). The assessment was commissioned by Mr Peter Higgins of Griffith City Council, OBJECTIVE The objectives of the assessment is to address issues outlined in a letter from NSW EPA (19 April 2000, Ref 235451A1/GFF2435) regarding groundwater at the site including: A review of existing groundwater monitoring information; To develop a plan to remediate groundwater contamination downgradient of the landfill, if present; and To develop a plan to protect the local groundwater resource from further contamination. 3. SCOPE OF WORK The scope of work comprised reviewing available information relevant to groundwater occurrence and quality issues at the site including: Douglas Partners Pty Ltd Report 14221 (March 1991) - Report on Geological Investigation for Proposed Road Aggregate Quarries, Griffith, NSW; o Coffey Geosciences Pty Ltd Draft Report AWL6409 (19 July 1999) Preliminary Hydrogeological Appraisal of Proposed Tharbogang Landfill Site; Coffey Geosciences Pty Ltd Report AWL6409/2-AA (20 August 1999) - Percolation testing and gas monitoring at Tharbogang Landfill; Coffey Geosciences Pty Ltd Draft Report AWL6409/1 (20 September 1999) - Draft Environmental Impact Study, Tharbogang Landfill; Analytical results of monitoring well sampling in January 2000; and Analytical results of monitoring well sampling in March 2000. 4. GROUNDWATER ASSESSMENT 4.1 Hydrogeology of Tharbogang Landfill From the draft Coffey report (AWL6409, July 1999), the site elevation varies from 174m AHD along the southern boundary ridge line to approximately 128m AHD at t6e northern boundary over a distance of approximately 700m. The site geology comprises sandstone and siltstone with conglomerate bands. The Mailman Gap Conglomerate is a coarse pebble sandstone and conglomerate unit which overlies the Jimberoo Member, a medium-coarse grained sandstone. The Mailman Gap Conglomerate contains low strength siltstone or very fine-g rained sandstone bands (Douglas Partners, 1991). AWL6409/1-BG 2 19 May 2000 Both units are silicified and were assessed to have negligible primary porosity although open jointing in both I- units is evident in the quarry. The units were assessed to have low to moderate permeability and low groundwater storage capacity. Surficial soils were assessed to have a permeability of the order of 0.2m/day with moderate moisture storage capacity (Coffey draft EIS, 1999). Douglas Partners (1991) boreholes were reported to have no groundwater inflows to a depth of at least iBm in the vicinity of the quarry. Two of three shallow monitoring bores on site were observed to be dry (Coffey, July 1999) and superficial soils to a depth of 3m are also characterised by a lack of Interface (perched) groundwater. I The recharge potential of the site is considered to be low due to the significant annual rainfall-evaporation deficit of 1463mm and is constrained to low frequency-high intensity rainfall events. 4.2 Current Groundwater Users Based on assessment of Department of Land and Water Conservation (DLWC) records, there are five registered bores in the vicinity of the site. Bore GW002556 is located approximately 7km northwest of the site and is about 1 00m deep. Water bearing zones were encountered in sandstone at 61m and 97.5m during drilling. The total airlift yield obtained was about 0.25LIs and the groundwater level is recorded as 57.9m below ground. Bore GW002635 is approximately 7km north of the site. This bore is about 53m deep and water was encountered at 49.4m during drilling in sandstone with an airlift yield of 0.16L/s. The static water level is recorded as 42.7m below ground. Bores GW051023, GW051024 and GW051025 are located near a basalt quarry approximately 3km west southwest of the site and were reportedly drilled for groundwater exploration purposes. No yield information is reported but all three holes intersected water-bearing fractured basalt and volcanic material. Total hole depths varied from 24m to 31.7m. The recorded depth to groundwater varied from im to 3.7m below surface. The bores are recorded as backfilled. 4.3 Monitoring Bores Drilling results from four monitoring bores drilled at Tharbogang Landfill are summarised in Table 1. The location of the bores is indicated on Figure 2. From Table 1, groundwater at the site is generally hosted in sandstone and clayey sand units. This is consistent with the Mailman Gap Conglomerate which includes sandstone and low-strength siltstone bands. The measured groundwater levels (Figure 3) in the monitoring bores suggest a northeast dipping hydraulic gradient of approximately 0.04 and groundwater flow towards the Tharbogang Swamp. Groundwater flow is expected to generally follow topography and concentrate below surface dainage features. Bore BH1 is upgradient of the existing landfill with BH2 adjacent, BH3 slightly downgradient and adjacent to the leachate collection pond and BH4 downgradient of the landfill in a drainage.-gully which drains to the swamp. AWL6409/1-BG ci I 19 May 2000 TABLE I - SUMMARY OF MONITORING BORE DRILLING RESULTS Bore Total Depth Water inflow depth Geology Screened depth Water Level Number (m) (m) (m) (m) BH1 38 25.6 Clayey Sand 21 to 28 15.6 26.2 Clayey Sand 28.8 Sand 29.4 Sand i 35.6 Clayey Sand 36.2 Clayey Sand BH2 42 35.5 Clayey Sand 30 to 42 22.0 36.6 37.4 BH3 35.5 31.8 Sandstone 24 to 35.5 18.9 32.5 33.4 34.8 BH4 38.5 36.6 Clayey Sand 26 to 38.5 15.4 37.2 Clayey Sand 37.8 Coarse Gravel The significant head difference between water inflow depths and groundwater levels indicates confined conditions and suggests that groundwater may upwell downgradient in the swamp. 4.4 Monitoring Results Copies of analytical results of groundwater sampling from four monitoring boreholes on site are included in Appendix A. Two monitoring rounds have been conducted at the end of January 2000 and the beginning of March 2000. The following analytes were tested in the samples: January 2000 - pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Dissolved Oxygen (DO), Bicarbonate, Total Kjeldahl Nitrogen (TKN), Ammonia, Nitrate Nitrogen, Chemical Oxygen demand (COD), Total Organic Carbon (TOC), Phenols, Organochlorine Compounds (0CC) and Organophosphate Compounds (OPC). March 2000 - Biological Oxygen Demand (BOD), TDS, Total Phosphorous, Aluminium, Arsenic, Barium, Cadmium, Cobalt, Copper, Lead, Mercury, Zinc, Total Chromium, Hexavalent Chromium, OPC, Total Petroleum Hydrocarbons (TPH), Benzene, Toluene, Ethylbenzene, Xylenes (BTEX), Volatile Chlorinated Hydrocarbons (VCH), 0CC, Polyaromatic Hydrocarbons (PAH). Analytical results for PAH, 0CC, VCH, BTEX, OPC, ammonia, arsenic, barium, mercury, total chromium and hexavalent chromium were all below laboratory detection limits and are not considered further. The remaining analytical results are summarised and compared to ANZECC (1992) Water Quality Guidelines for Protection of Aquatic Ecosystems in Table 2. AWL6409/1 -BG 4 19 May 2000 TABLE 2 -THARBOGANG LANDFILL GROUNDWATER ANALYTICAL RESULTS Analyte Date 131-11 BH2 BH3 BH4 ANZECC1 pH 01/00 7.2 6.5 6.7 7.0 6.5-9.0 EC(pS/cm) 01/00 4140 660 5960 3980 1500 TDS(mg/L) 01/00 2902 458 4136 2464 <1000 03/00 5452 460 3778 2572 <1000 DO (mg/L) 01/00 32 1,5 3.2 1,9 >6 Bicarbonate (mg/L) 01/00 410 99 559 523 -- 2 TKN (mg/L) 01/00 2,8 11.2 2.8 2,6 0 1 to 0.5 Nitrate (mg/L) 01/00 25 50 5 30 0.1 to 052 COD (mg/L) 01/00 377 373 335 305 -- TOO (mg/L) 01/00 41 76 440 36 -- Phenol (mg/L) 01/00 0.5 0.6 1.0 0.8 0.05 BOD (mg/L) 03/00 54 60 55 108 -- Total P (rngIL) 03/00 0.5 0.5 0.2 0.4 0.005 to 0.05 Aluminium (mg/L) 03/00 <0.1 1.3 <0.1 <0.1 0.1 Cadmium (mg/L) 03/00 0.013 0.003 0.009 0.009 0.002 Cobalt (mg/L) 03/00 0.08 <0.01 0.06 0.06 -- Copper (mg/L) 03/00 0.04 0.04 0.04 0.09 0.005 Lead (mg/L) 03/00 0.15 0.18 0.19 0.06 0.005 Zinc (mg/L) 03/00 0.47 0.53 0.07 0.60 0.05 TPH C6-C9 (mg/L) 03/00 0.7 0.9 1.3 1.0 -- Notes: 1 Australian and New Zealand Environment and Conservation Council (ANZECC, 1992) Guidelines for the Protection of Aquatic Ecosystems.