Stormwater and Sediment Treatment Assessments

Client:  Z Energy
Date:  2013

We were engaged in 2013 by Z Energy to determine the typical stormwater and sediment treatment performance which can be achieved by on-site treatment devices located at Z Energy service stations.  The data collected by this assessment will be used by Z Energy to identify best management practices for stormwater management of service stations and to also provide further information to Councils regarding the performance of such devices within an active service station.

Monitoring rainfall events usually requires waiting for the right size of rainfall event to get the right data.  However, we have developed a means of producing artificial rainfall at the correct rates for testing site-specific treatment devices.  This has meant no waiting for the right rainfall and a much more efficient testing programme.

A total of five service stations were monitored.  In addition, two high-use car parks were monitored as controls for the assessment.  Both forecourt (where fuel is dispensed) and non-forecourt (where fuel is not dispensed) areas were assessed in the assessment.

The works involved:

  • Site assessment of Auckland Z Energy service stations to determine appropriate sites to monitor.
  • Preparation of a Monitoring and Management Plan to guide the works.
  • Determining appropriate design characteristics for an engineered storm to represent maximum flow through rates for the sites stormwater treatment device.
  • Collection and analysis of sediment and water quality samples.
  • Data reporting and Auckland Council liaison.

Key Aspects: 

  • Engineered storm monitoring
  • Stormwater quality assessment
  • Sediment quality assessment
  • Oil-water separator treatment efficiency
  • Contaminant mass balance assessment
  • Council liaison

Client:  Z Energy
Date:  2013

Stormwater sampling was carried out to characterise the changing pollutant load that can be discharged from a catchment during a storm event.  A significant suite of stormwater and sediment quality parameters were collected, including:

Sediment Sampling

Total Petroleum Hydrocarbons (TPH), Benzene, Toluene, Ethyl benzene, Xylene (BTEX), Polycyclic Aromatic Hydrocarbons (PAH), Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Zinc, pH, sediment grain size.

Stormwater Sampling

Total Petroleum Hydrocarbons (TPH), Benzene, Toluene, Ethyl benzene, Xylene (BTEX), Polycyclic Aromatic Hydrocarbons (PAH), Total and dissolved Arsenic, Total and dissolved Cadmium, Total and dissolved Chromium, Total and dissolved Copper, Total and dissolved Lead, Total and dissolved Nickel, Total and dissolved Zinc, Total Suspended Solids; pH, Electrical conductivity, Dissolved oxygen, Temperature, Oxygen reduction potential, Turbidity.

Engineered storm across the non-forecourt

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