Erosion and Sediment Control Monitoring Plan Rev. 0 This is an uncontrolled copy if photocopied or printed from the Intranet. Copyright © 2016. All rights reserved. Page 9 of 10 The treatment efficiency trigger will also be used to identify catchments that are deemed higher risk. If efficiency triggers are breached, then that SRP will be deemed to be ‘high risk’ for the next rainfall trigger event. High risk SRPs will be subjected to additional scrutiny during pre-forecast inspections (forecasts of >25mm/24 hrs) to ensure that repeat breaches do not occur. pH exceedance Typically, chemical treatment of sediment control devices will slightly lower pH. If pH is recorded to be below 6.0, the following actions will occur: • The catchment area of the treatment device will be checked against the area assumed when the chemical dosing rate was set. The area and / or dose rate will be adjusted as needed. • The does rate will be checked. Additional bench testing and adjustment of the dose rate will be made if required. • The material exposed within the catchment of the device will be checked. If that incorporates PAF, all runoff from that catchment will be diverted to the treatment plant. • The chemical treatment system will be reviewed and if necessary. SRP efficiency / Turbidity / Clarity If one of these targets is exceeded, an additional review of the controls and catchment of the controls will be made. Generally, any maintenance requirements will have been identified during regular monitoring. Additional considerations will include the measures noted above i.e.: • The catchment area of the treatment device will be checked against the area assumed when the chemical dosing rate was set. The area and / or dose rate will be adjusted as needed. • The dose rate will be checked. Additional bench testing and adjustment of the dose rate will be made if required. • The material exposed within the catchment of the device will be checked. If that incorporates PAF, all runoff from that catchment will report to Collection Ponds and be diverted to the Water Treatment Plant. • The chemical treatment system will be reviewed and if necessary. Additional response measures may include: • Increased frequency of desilting of device(s). • Reducing the contributing catchment area by temporary stabilisation. • Installation of additional sediment controls. • Increasing forebay ponding areas within the site. 6. REPORTING 6.1. Rainfall Trigger Event Report Following a rainfall trigger event (>25mm in a 24hr period), a summary report of the performance of SRPs, DEBs and overall ESC system observed during the rainfall event report will be provided to WRC. The report will include: • A summary of the rainfall (total and intensity) • A summary of the manual monitoring undertaken and comparison of manual monitoring results to previously recorded results • A summary of the site performance against the performance targets.
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