Presenter:  Anna Lukey, AECOM

Presentation title:  Management of short term dewatering discharges

Management of short term dewatering discharges  Discharges from dewatering procedures require management when redeveloping sites impacted with petroleum hydrocarbons.  The developer must understand the dewatering requirements at the resource consent application stage.  This will assist the consent authority to be able to issue a meaningful consent with appropriate conditions.   Information required at the planning stage includes the expected rate and duration of the discharge in addition to the quality.   The ultimate receiving environment must also be identified, as this may limit the discharge rate.  This information will allow for the developer to determine what, if any, treatment is required prior to discharge.     There are varying methods for treatment which the contractor should plan to be able to use if visual observations show it to be necessary.   Consents may include a condition for comparison samples to be held on site, so discharge quality can be visually monitored.  If discharge quality is inferior to what is required, treatment options can be implemented.  This should be a staged approach, based on observations, and the resource consent conditions should reflect this.  If the issue is petroleum hydrocarbons, there are varying treatment methods, including allowing settlement and skimming the water surface for separate phase and aeration of the discharging water to break up dissolved phase.  Suspended solids can be managed by varying methods, including the depth of abstraction and silt traps.  To ensure a compliant, timely construction programme, it is important to get both aspects of planning accurate at the start, that is; the resource consent and the equipment likely to be required identified.

Event: WasteMINZ Conference 2013

Date: Thursday 24 October 2013