Contamination Delivery Work Plan
3.
Summary of contamination assessment 3.1 Overview
Contamination investigations conducted for the CRL project to support obtaining the necessary planning approvals for works in the Mt Eden area are documented in the following reports. • • •
City Rail Link: Contaminated Land Assessment July 2012, prepared by AECOM; Auckland City Rail Link: Aotea Station to North Auckland Line Construction and CRL Operation Contaminated Land Assessment May 2016, prepared by Golder Associates; and Auckland City Rail Link: Aotea Station to North Auckland Line Construction and CRL Operation Contaminated Land Assessment – South Pacific Timber July 2016, prepared by Golder Associates.
The contaminated land assessments undertaken for the CRL works in the Mt Eden area comprised an assessment of soil and groundwater. For accessibility and logistical reasons, the soil and groundwater investigations did not necessarily target specific locations but were positioned to provide an overview of potential ground contamination constraints.
3.2 Geology and hydrogeology The geology in the CRL Mt Eden Enabling Works area comprise the following: • •
• •
Fill – surficial fill variably comprised of clays, silts, sands and rubble. Fill is typically up to approximately 4 m bgl. The composition and thickness varies irregularly; Tauranga Group (TA) – alluvium, typically composed of clayey to sandy silts. These sediments are derived predominantly from erosion of East Coast Bays Formation (ECBF). Some areas of very soft TA and high organic content TA have been encountered; ECBF – a sequence of sandstone beds with interbedded mudstone and siltstone layers; and Auckland Volcanic Field (AVF) – three distinct lithologies present; ash, tuff and basalt lava.
Fill is typically underlain by TA/ECBF but within the works area there are areas underlain by AVF. Several groundwater monitoring wells have been installed in the vicinity of the works area. Groundwater levels indicate the presence of perched groundwater recorded between 0.5 m and 2 m bgl. Additional groundwater details are included within the Groundwater and Settlement Monitoring and Contingency Plan (GSMCP) prepared for the Mt Eden Enabling Works.
3.3 Soil quality Intrusive investigation work has been undertaken on public land and within road reserves around the CRL project alignment and have not specifically assessed potential contamination on private properties. Soil quality testing undertaken in and around the Mt Eden Enabling Works area has largely focused on potential contaminants of interest likely to be associated with the urban land use. More targeted investigations were also undertaken at the South Pacific Timber site (21 Ruru Street) which makes up the south-western portion of the Mt Eden Enabling Works area. The South Pacific Timber site was formerly part of a railway marshalling yard until the tracks through the area were removed in the 1960s to 1970s. South Pacific Timber had leased their site for approximately 20 years sealing the site with concrete on occupation. The South Pacific Timber site has been used for timber storage and distribution; timber treatment activities have not been undertaken at the site. Page 15
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