This case study looks at the remediation of a contaminated land site that was in the middle of a suburban area, 150 metres from the Noosa River. Gaffville Pty Ltd commissioned AgriRem Earth Care to remediate lots 3 and 4 RP122928, 14–16 Mary Street, Noosaville, Queensland.

Site background

AgriRem Earth Care was called into the Mary Street project after the project had been stalled by unforeseen developments. The Gaffville project aimed to have the site cleared from the Environmental Management Register for future developments, including residential.

The site was contaminated because it hosted a service station that stored liquid petroleum in underground tanks. The tanks became unstable over time and cracked, allowing the petroleum to seep into the surrounding soil.

Regarding the situation the project was in when he deemed it necessary to contact AgriRem Earth Care, Tony Blackmore said:

During the excavation of the specific locations it became apparent that both building and road obstructions were going to prevent the full excavation as required. On the day of excavation, it became apparent that the level of excavation required, ridding the site of the contaminants reached a point of impossibility. The undermining of the building was occurring in pursuit of the fuel contaminant. A situation of absolute disappointment grew with the fact that we were not going to be able to achieve the desired outcome, to this stage we had exhausted substantial funds and we were ready to surrender to the obvious and backfill the sites in surrender.

Tony was advised to contact AgriRem Earth Care. After an onsite meeting with Dean Hore and Chris Allman, Tony said:

This [meeting] was a game changer for the process and the ultimate outcome moving forward. Both Chris and Dean were able to assess the situation and recommended the use of ‘AgriRem A100’ as a treatment of both the excavated areas and the stockpile. I can honestly say that up to that meeting, I had given up and was ready to simply fill in the holes, and surrender to the fact I was never going to achieve the desired results.

Site assessment and results

Duke Environmental performed a contamination assessment, and remediation and validation assessment, in line with the Draft guidelines for the assessment and management of contaminated land in Queensland 1998 (EPA 1998) and the National Protection (Assessment of Site Contamination) Measure 1999 (NEPM 1999), in 2 stages.

Stage 1: Before AgriRem® A100 treatment

Duke Environmental’s assessment report describes the following for the stage 1 contamination assessment, and remediation and validation assessment:

Samples of soil and groundwater, collected by Duke Environmental on 29 February 2012, were sent to Australian Laboratory Services (ALS) for analysis of a variety of contaminants including eight (8) metals (arsenic, cadmium, chromium, copper, lead, nickel, zinc, mercury), total petroleum hydrocarbons (TPHs), total recoverable hydrocarbons (TRHs), benzene, toluene, ethyl benzene, meta- and paraxylene and orthoxylene (BTEX), and polynuclear aromatic hydrocarbons (PAHs). These tests showed that the levels exceeded EPA 1998 and NEPM 1999 EIL [ecological investigation level] requirements accordingly.

Stage 1 test findings for the soil and groundwater samples taken on 29 February 2012 before AgriRem® A100 treatment are shown in Table 1.

Stage 2: After AgriRem® A100 treatment

The Duke Environmental report describes the results of the stage 2 contamination assessment, and remediation and validation assessment:

As a result of the bioremediation process performed by AgriRem Earth Care on 22nd August 2012, validation sampling was undertaken by Duke Environmental on 20 September 2012 and sent to ALS for analysis of eight (8) metals, TPH, BTEX and PAH.

Laboratory results for soil and groundwater samples indicated that material did not exceed EPA or NEPM 1999 HILs [health investigation levels] for a residential ‘A’ setting. The sample material did not exceed EPA EILS or NEPM EILs.

The results of groundwater testing indicated levels of PAH and TPH/TRH had declined. A further round of groundwater testing was undertaken from GW1 on 15 October 2012, which indicated a continued downward trend in levels of TRH contamination, with PAH levels and the TRH (>C10-C40 fraction (sum)) below laboratory limits of reporting. The levels of TRH contamination for C6-C10 fraction in the groundwater fell below the CRC CARE health-based screening levels (HSL) for low-density residential.

Based on the results of the bioremediation process and subsequent analysis the site has been removed from the EMR and been declared suitable for any use, including low-density residential ‘A’.

The results from stage 1 and stage 2 soil and groundwater samples are shown in Tables 2 and 3.

Summary

Tony Blackmore summarises the results of the AgriRem Earth Care treatment of the site and the impact of the results for him and Gaffville Pty Ltd:

The application of the product [AgriRem® A100] to the ground chased the fuel through the groundwater and the surrounding area, saved any further excavation expenses. The treatment was also applied to the stockpile. Subsequent testing 4 weeks later revealed a massive decline in the previous readings, and resulted in the site being totally cleared from the [EMR] register.

Without the application of AgriRem® A100 this result could not have been achieved. The fact that this organic material was able to clean up the site was a miracle to myself at a very vulnerable time. The boys from AgriRem Earth Care achieved something I had given up on, and consequently I have no hesitation endorsing their process to anyone going through the harrowing experience of contaminated land.