Industrial and Trade Activity Environmental Management Plan
5.
Management Procedures and Mitigation Measures 5.1 Bentonite Plant
The main environmental risks associated with the bentonite plant are the discharge of chemicals from the operation of the plant and/or the discharge of sediment laden water to stormwater drains within the main works area, which in turn discharge into the Waitematā Harbour. To avoid or minimise any discharges from the bentonite plant to the surrounding environment, each plant is designed and operated as follows: •
The entire bentonite plant is bunded to contain any spilt material or bentonite slurry in the event of a pipe or pump failure during transfer of the slurry. Any surface water collected in the bund is pumped out to the on-site WTP.
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Sodium bicarbonate and bentocyrl are added to the bentonite slurry. Neither chemicals are classified under HSNO as hazardous and are stored within the bunded bentonite plant area. No other environmentally hazardous substances are required as part of the bentonite plant operation.
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In the event of a spill outside of the bunded area, the standard spill control procedures will be implemented to contain and manage the spill (refer to Section 6 of this ITA EMP).
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In addition, a Bentonite Plant Spill Response Plan has been prepared and will be implemented (refer Appendix C). This Plan outlines the environmental controls and spill response procedures specific to the operation of the plant detailed in Section 2.3 of this ITA EMP. The extent of the bunded areas of the bentonite plant that will be sealed off during the works are shown in the Stormwater Drainage Plan in the Bentonite Plant Spill Response Plan.
5.2 D-Wall Construction The main environmental risk associated with D-wall construction is the discharge of sediment laden water and high pH to the stormwater networks. To avoid or minimise any discharges from the construction of D-walls at CSA 5, the works are managed as follows: •
The entire D-wall construction area drains to a low point from which any runoff is pumped to the on-site WTP.
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All stormwater catchpits within the works areas have been removed or diverted to the WTP.
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In the event of a spill outside of the bunded area, the standard spill control procedures will be implemented to contain and manage the spill (refer to Section 6 and Appendix B of this ITA EMP).
5.3 Soil Mixing Plant The main environmental risk associated with operation of the soil mixing plant is the discharge of sediment laden water and elevated pH from cement used in the grout slurry mix. To avoid or minimise any discharges from the jet grout plant into the surrounding environment, the plant will be designed and operated as follows: •
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The soil mixing plant is bunded, with any surface water collected in the bund being pumped out to the on-site water treatment plant. | Mt Eden Main Works
