THEBARTON ASSESSMENT AREA - epa.sa.gov.au

EPA REF 0524111 FINAL REPORT STAGE 1 ENVIRONMENTAL ASSESSMENT THEBARTON ASSESSMENT AREA

Activity Details

Groundwater well Groundwater wells were drilled by WB Drilling using a combination of hand augering installation mechanical pushtube and solid auger techniques

Following the completion of drilling each borehole was fitted with 50 mm class 18 uPVC casing with a basal 6 m long section of slotted well screen A filter pack comprising clean graded sands of suitable size to provide sufficient inflow of groundwater was installed within the annular space between the borehole and the well casing and extended from the base of the screened interval to approximately 1 m above the termination of the slotted casing A 1 m long bentonite collar comprising pelleted or granulated bentonite was placed above the filter pack to prevent water seepage downward along the well casing or borehole from ground surface Each well was grouted up to surface level and fitted with a (lockable) steel gatic cover the latter flush mounted to prevent tripping andor other hazards Groundwater well log reports are included in Appendix H

Soil logging and Soil logging was undertaken in general accordance with the ASC NEPM (1999) which geotechnical sampling endorses AS1726-1993 In addition to the requirements of AS1726-1993 particular

attention was paid during logging to any lithological variations such as sandgravel lenses or secondary porosity (such as clay fracturing) which may act as potential preferential pathways for contaminant vapourgroundwater migration through the sub-surface as well as the presence of fill material andor any olfactory or visual evidence of contamination Soil descriptions have been included on the logs in Appendices H to J Cores for geotechnical analysis were collected using push tube sampling methodologies to obtain undisturbed samples Section(s) of core to be tested were retained (intact) within the pushtube liners and capped at each end for storage and transport to the analytical laboratory

Field screening of soils Field screening of individual soil layers was undertaken at the majority of the drilling locations and involved the use of a photoionisation (PID) unit fitted with an 117 eV lamp (ie as considered suitable for the detection of CHC) The PID unit was calibrated by the hire company prior to delivery and was checked on a daily basis against an isobutylene calibration gas of known concentration Field screen samples were collected with care to ensure that each sample was representative of the soil stratum from which it was collected and experienced minimal loss of volatile compounds The soil material was placed immediately into a zip lock bag and sealed ensuring the bag was half filled (ie such that the volume ratio of soil to air was equal) Soil clumps within the bag were manually broken up and the bag was left to rest for a minimum of five minutes but no longer than 20 minutes Prior to testing the bag was shaken vigorously to release any vapours within the soil To test the tip of the PID probe was inserted into the bag and the maximum volatile organic compound (VOC) reading recorded after a nominal 10 second period or when the reading had peaked Results were recorded on the appropriate bore log sheets presented in Appendices H to J

Groundwater well Following installation the wells were developed by purging a minimum of four well development volumes (ie until stable parameters were obtained andor until the well purged dry) from

the casing with a steel bailer andor twister pump to ensure hydraulic connectivity with the aquifer formation

Groundwater gauging Groundwater levels in the newly installed and existing monitoring wells located across the Thebarton EPA Assessment Area were gauged using an interface probe prior to the commencement of the groundwater sampling program All monitoring wells were gauged for SWL the potential presence of NAPL and the total well depth Groundwater field gauging results are presented in Appendix E

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EPA REF 0524111 FINAL REPORT STAGE 1 ENVIRONMENTAL ASSESSMENT THEBARTON ASSESSMENT AREA

Activity Details

Groundwater sampling The majority of the wells were sampled using low flow (micropurge) techniques Where recovery was particularly low (ie MW4 MW8 MW15 MW18 MW19 and MW24) and unsuitable for low flow (micropurge) sampling the original sampling technique was abandoned and a HydraSleeveTM (no purge) methodology was used instead Groundwater samples were collected in laboratory-supplied screw top bottles containing appropriate preservative (if required) with no headspace allowed Samples were chilled during storage and transport to the analytical laboratory Disposable nitrile gloves worn by field personnel were changed prior to the collection of each sample Samples for metals (ie iron manganese) analysis were filtered in the field using 045 microm filters Groundwater field sampling sheets are presented in Appendix E

Low Flow Methodology The low flow sampling technique involved the following the pump was placed close to the bottom of the screened interval the flow rate (up to 05 Lmin) was regulated to maintain an acceptable level of

drawdown with minimal fluctuation of the dynamic water level during pumping and sampling

groundwater drawdown was monitored constantly during purging and sampling using an interface probe

water quality parameters were considered to have stabilised when the following ranges were recorded over three consecutive readings ndash electrical conductivity plusmn 5 ndash pH plusmn 01 ndash temperature plusmn 02degC ndash dissolved oxygen plusmn 10 ndash redox potential plusmn 10 mV

the stabilisation parameters were recorded on field logging sheets after every one litre of groundwater purged using a calibrated water quality meter and a flow cell suspended in a bucket with litre intervals marked and

samples were collected once three consecutive stabilisation parameters were recorded and a volume of between 28 and 6 litres was purged prior to sampling

HydraSleeveTM Methodology The HydraSleeveTM sampling technique involved attaching a stainless steel weight to the bottom and a wire tether clip to the throat of the HydraSleeveTM before lowering it into the water column to the desired depth and allowing it to fill with groundwater After a minimum period of 24 hours the HydraSleeveTM was quickly and smoothly withdrawn from the well and the contents were transferred into the sample containers Water quality parameters were measured after samples were decanted ndash either within the water remaining in the HydraSleeveTM or within a grab sample collected using a disposable bailer

Hydraulic testing Rising and falling head permeability (ldquoslugrdquo) tests were undertaken to estimate the hydraulic conductivity (K) of the aquifer within various parts of the Thebarton EPA Assessment Area The falling-head tests were initiated by quickly inserting a 1285 m long and 36 mm diameter solid PVC cylinder (slug) into the water column at each well to produce a sufficient sudden rise in the water level The subsequent ldquofallrdquo back to the static water level (recovery) was measured and recorded automatically and in real-time using a

80607-1 REV1 30102017 PAGE 17

EPA REF 0524111 FINAL REPORT STAGE 1 ENVIRONMENTAL ASSESSMENT THEBARTON ASSESSMENT AREA

Activity Details

pressure transducerdata logger programmed to record water levels at a one second interval After static water level conditions returned in the well the rising-head test was initiated by quickly removing the slug from the well to create a sudden drop in the water column height As with the falling-head test the rise of the water level back to a static condition (recovery) was automatically recorded

Soil vapour bore Soil vapour bores were drilled by Aussie Probe using a combination of hand augering and installation mechanical pushtube techniques

Within each 3 m deep soil vapour bore teflon tubing attached to a soil vapour probe was inserted to the base of the hole which had been prefilled with approximately 005 m of clean filter pack sand An additional 045 m of sand (ie approximately 05 m in total) was then added to the hole and topped by a bentonite plug seal of approximately 05 m thickness A second soil vapour probe was installed at a depth of about 1 m within a 05 m sand pack which was overlain by bentonite to a depth of about 02 to 03 m BGL The two 1 m deep soil vapour bores were installed in a similar manner with a sand pack extending from the base to about 05 to 06 m BGL overlain by a bentonite plug to 03 m BGL Each installation was completed with grout to surface and topped with a standard flush-mounted gatic cover Soil vapour bore log reports are included in Appendix J

Soil vapour sampling All soil vapour sampling works were undertaken by SGS using suitably trained and experienced personnel ndash SGS holds National Association of Testing Authorities (NATA) accreditation for all soil vapour sampling and laboratory analytical works Combined field sampling sheets and COC documents are presented in Appendix G Soil vapour samples were collected using summa canisters and analysed using the US EPA (1999) TO-15 method Sampling involved the connection of a passivated 1 L stainless steel canister to the teflon tubing extending from the soil vapour probe and the use of a soil gas sampling train to restrict flow to a maximum rate of 200 mLmin Canister vacuum pressure was monitored during sampling to enable calculation of the volume of sample drawn into the canister ndash the small amount of vacuum left in the canister at the end of the sampling procedure was measured in the laboratory to check if any leaks occurred during transit (refer to further discussion in Table 52) A shroud was set up around the sampling point and tracer chemicals were introduced at high concentrations by flooding the shroud with helium and placing a cloth soaked with IPA into the shroud Each canister was cleaned and certified by SGS prior to use (refer to Appendix G) and backshyup coconut shell carbon sorbent tube samples were also collected (but not analysed) Summa canisters did not require chilling during transport to the analytical laboratory

Waste disposal Waste water and surplus soil corescuttings were stored together within 205 litre drums in the rear car park of a commercialindustrial property at 19-21 James Congdon Drive (as organised by the EPA) prior to removaldisposal by a licensed waste removal company (Cleanaway) Analytical results pertaining to the soils were forwarded to the licensed receiving facility and all of the soil was classified as lsquoWaste Fillrsquo in accordance with the Environment Protection Regulations 2009 The waste transport certificates are included in Appendix K

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