Assessment of adverse effects from oil and grease discharges from Meridian Power Stations

Meridian operates 6 of the 8 hydroelectric power stations that form the Waitaki hydro scheme: Ōhau A, Ōhau B, Ōhau C, Benmore, Aviemore, and Waitaki. As part of the reconsenting of discharges related to the operation of these power stations, Meridian identified a potential concern related to contamination of the receiving environment from total petroleum hydrocarbons (TPH) (associated with oil and greases) discharged in drainage water from these stations. Meridian required an assessment of whether the discharge of TPH was likely to cause adverse effects in the receiving environment of the Ōhau canals, lakes and rivers of the Waitaki catchment.

Dr Mike Stewart undertook an assessment of potential effects from TPH discharged from these power stations. Mike’s assessment included assessing compliance with relevant water quality standards for TPHs included in Environment Canterbury’s regional plan, and other applicable guidelines, as well as reviewing and summarising the results of compliance monitoring related to existing discharge consent conditions. An analysis of temporal trends in TPH concentrations was also undertaken. High level risk assessments were undertaken to identify potential risks to drinking water and receiving environment quality.

Leading on from this project Dr Stewart also developed a water quality sampling programme designed to assess whether discharges from the Waitaki Power Station sites are having an adverse effect on receiving environment water quality. The monitoring programme included standard water quality parameters (nutrients, E. coli, physical parameters), TPH, stormwater runoff from structures and carparking (metals and PAHs), and human wastewater overflows (human wastewater markers). Ultimately, the sampling results may be included in resource consent applications and used in expert evidence

Oil car motor lubricant engine lube with bubble isolated on white background