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Stage 2 - Detailed Site Investigation

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Alliance Geotechnical Pty Ltd (AG) engaged Northrop Consulting Engineers P/L to carry out a Stage 2 Detailed Site Investigation (DSI) for 172 Showground Road, Castle Hill NSW (see Figure 1 with 'site' boundaries marked in Figure 2) . The site is proposed for redevelopment, which includes a new warehouse for the Museum of Applied Arts and Sciences. In 2019, AG conducted a first level preliminary site investigation (PSI); and.

A contamination assessment consisting of a Phase 2 Detailed Site Investigation (DSI) of the site is required to determine whether the site is suitable for the proposed land use scenario. Advise on whether the site will be suitable (in the context of soil contamination) for the proposed land use environment; and. Conduct an in-depth site investigation to determine soil conditions and to facilitate the collection of representative soil and groundwater samples;.

Assessment of the state of contamination of the site and recommendation of possible further remediation requirements related to the renovation of the site. Based on the assessments made as part of this investigation, the AG concluded that the site is considered suitable for the proposed land use setting.

INTRODUCTION

SITE IDENTIFICATION

SITE SETTING

PREVIOUS CONTAMINATION ASSESSMENTS

CONCEPTUAL SITE MODEL

There are no groundwater boreholes on the site or downslope of the site registered for drinking water use. This creek is considered a freshwater environment and consideration of freshwater guideline values ​​is warranted. AG notes that the proposed development includes building structures and hard underground paving areas over the majority of the site, which will act as a direct contact barrier between potential soil contamination and on-site receptors during the operation of the site.

The historical evidence reviewed indicated a low potential for a primary source to be present at the site. The historical evidence pointed to potential land use activities being carried out on the site which have the potential to result in unacceptable aesthetic impacts. The AG notes that the proposed development includes building footprints and hard surface pavement areas across most of the site, which would act as an exposure barrier between potential aesthetic impacts and on-site receptors during the operation of the site.

Based on the field observations, guidance in ASC NEPM 2013, and the nature and scope of the proposed development concept, the need for further ecological assessment is not considered warranted. Application of the management limits requires consideration of site-specific factors such as the depth of building basements and services and depth to groundwater, to determine the maximum depth to which the limits must apply.

DATA QUALITY OBJECTIVES

The measured physical and/or chemical parameters of the media samples at the site (including field screening and laboratory analysis where applicable); and. The spatial extent of the project will be limited to the site as defined by its boundaries. The lateral extent across which contamination is expected to be distributed, based on the conceptual site model, is defined by the derived boundaries of the Areas of Environmental Concern (AEC).

The wash blank will be analyzed for at least one of the analytes for which the sample(s) collected that day is scheduled for analysis (with the exception of asbestos). Collected duplicates and triplicates will be analyzed for at least one of the analytes for which analysis of the duplicate/triplicate parent sample is planned (with the exception of asbestos). If the field data and laboratory analytical data are within the limits of the assessment criteria adopted for this project (see section 6.3), the risks of exposure to contamination of the identified receptors are considered acceptable.

Calculation of the 95% upper confidence limit (UCL) statistic to determine the mean concentration of relevant contaminants of potential concern;. Furthermore, Section 6.2.1 of ASC NEPM 2013 states that the number and location or sampling points are based on knowledge of the site and professional judgment.

Table A in NSW EPA (1995) provides guidance on minimum sampling point densities required for site  characterisation, based on detecting circular hot spots by using a systematic sampling pattern
Table A in NSW EPA (1995) provides guidance on minimum sampling point densities required for site characterisation, based on detecting circular hot spots by using a systematic sampling pattern

FIELDWORK METHODOLOGY

A sub-sample from each sampling point was placed in a zip lock bag, sealed and shaken. The overall results of the site screenings indicated a low potential for the presence of ionizing volatile organic compounds (VOCs) in the samples. No visual evidence of potential asbestos containing materials (ACM) was observed at any of the soil sampling locations or while walking through the site.

LABORATORY ANALYSIS

DATA QUALITY INDICATOR ASSESSMENT

The data collected is considered to be adequate within the project's goals and limitations. An assessment of the comparability of collected data was made and the results presented in Table 9.2. The data collected is considered to be sufficiently comparable within the project's goals and limitations.

An assessment of the representativeness of the data collected was made and the results are presented in Table 9.3. An assessment of the accuracy of the data collected was undertaken and the results are presented in Table 9.4. The data collected is considered to be reasonably accurate within the objectives and constraints of the project.

An assessment of the accuracy of the data collected was made and the results presented in Table 9.5. The data collected is considered to be sufficiently accurate within the objectives and constraints of the project.

Table 9.2 Comparability DQI
Table 9.2 Comparability DQI

DISCUSSION

The concentrations of benzene, toluene, ethylbenzene and xylenes detected in the analyzed soil samples were lower than the valid accepted criteria for human health exposure to inhalation/intrusion of vapors. The concentrations of naphthalene detected in the soil samples analyzed were lower than the current accepted criteria for human health exposure to inhalation/inhalation of vapors. The concentrations of pollutants of significant concern detected in the analyzed soil samples were below the applicable accepted ecological screening levels (ESLs) with the exception of PFOS (PFAS compounds) in soil samples P4 and P6.

Although these samples exceeded the interim indirect exposure guidelines, it is noted that soil from sampling locations where PFAS compounds have been identified will be excavated as part of the basement construction, thereby removing the limited risk to the limited ecological receptors around the site. Furthermore, due to the nature of the construction, any soil that remains will be covered by concrete, including the basement and the ground floor, thereby removing terrestrial ecological exposure pathways. It is therefore the opinion of AG that the detected concentration of PFAS does not pose a significant risk to surrounding ecological receptors.

CONCLUSIONS AND RECOMMENDATIONS

STATEMENT OF LIMITATIONS

Accredited to comply with ISO/IEC 17025 - Testing Results of tests, calibrations and/or measurements included in this document are traceable to Australian/National Standards. A recent review of our LIMS resulted in the correction or clarification of some method identifications. However, our laboratory methods have not been significantly modified, so there is no change in the validity of the current or previous results.

Laboratory QC results for method blanks, duplicates, matrix spikes and laboratory control samples follow the guidelines set out in the National Environmental Protection (Site Pollution Assessment) Act 1999, as amended in May 2013, and are included in this QC report. where appropriate. If the laboratory has not received the information within the required time and regardless of any other integrity issues, properly qualified results may still be reported. Blank method In the case of solid samples, these are performed on laboratory-certified clean sand, and in the case of water samples, on deionized water.

Duplicate A second part of the analysis from the same sample and reported in the same units as the result to show comparison. NCP Non-Client Parent - QC performed on samples not belonging to this report, the QC is representative of the sequence or group within which the client samples were analyzed. PFAS field samples containing surrogate recoveries exceeding the QC limit defined in QSM 5.3 where no positive PFAS results were reported were reviewed and no data were affected.

Note: These two PAH isomers elute closely using the most modern analytical methods and both the reported concentration (and the TEQ) apply specifically to the total of the two co-eluting PAHs. NOTE: While actinolite, anthophyllite, and tremolite asbestos can be detected by PLM with DS, due to variability in the optical properties of these materials, AS4964 requires them to be reported as UMF unless confirmed by an independent technique. All fibrous materials larger than 10mm, larger than 2mm and material passing through the 2mm sieve are retained and analyzed for the presence of asbestos.

NOTE: Depending on the nature and size of the soil sample, residual material less than 2 mm may need to be sub-sampled for trace analysis, in accordance with AS 4964-2004. This is due to the low quality or small length or diameter of the asbestos fibers present in the material, or the fact that very fine fibers are intimately distributed throughout the materials. NOTE: NATA News March 2014, p.7, with regard to asbestos, states that this is a qualitative method with a nominal reporting limit of and that currently "there is no validated method available for the quantification of asbestos" in Australia. This report is consistent with the analytical procedures and reporting recommendations in the NEPM and the WA DoH.

Accredited for compliance with ISO/IEC 17025 – Testing The results of the tests, calibrations and/or measurements included in this document are traceable to Australian/national standards. For the purposes of the NEPM, ACM is generally limited to that material that does not pass a 7mm x 7mm sieve. For the purposes of the NEPM, FA is generally limited to that material that does not pass a 7mm x 7mm sieve.

Trace analysis Analytical procedure used to detect the presence of respirable fibers in the matrix.

Table 1 BH01‐0.1‐0.3 BH02‐0.1‐0.3 BH03‐0.1‐0.3 BH04‐0.1‐0.3 BH05‐0.1‐0.3 BH06‐0.1‐0.3 BH07‐0.1‐0.3 BH08‐0.0‐0.2 BH09‐0.1‐0.3 BH10‐0.0‐0.2 BH11‐0.1‐0.3 BH12‐0.1‐0.3 BH13‐0.1‐0.3
Table 1 BH01‐0.1‐0.3 BH02‐0.1‐0.3 BH03‐0.1‐0.3 BH04‐0.1‐0.3 BH05‐0.1‐0.3 BH06‐0.1‐0.3 BH07‐0.1‐0.3 BH08‐0.0‐0.2 BH09‐0.1‐0.3 BH10‐0.0‐0.2 BH11‐0.1‐0.3 BH12‐0.1‐0.3 BH13‐0.1‐0.3

Figure

Table A in NSW EPA (1995) provides guidance on minimum sampling point densities required for site  characterisation, based on detecting circular hot spots by using a systematic sampling pattern
Table 6.7.8 Laboratory Holding Times, Analytical Methods and Limits of Reporting
Table 6.7.7 Laboratory Analytical Schedule
Table 9.1 Completeness DQI
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References

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