Erosion and Sediment Control Assessment Report Rev. 0 This is an uncontrolled copy if photocopied or printed from the Intranet. Copyright © 2016, SouthernSkies Environmental Ltd. All rights reserved. Page 21 of 30 and to monitor the effectiveness of ESC for the duration of the construction phases of the Project. Environmental compliance and performance will be achieved through appropriate location, design, installation, as-built certification, maintenance, and monitoring of ESC measures. ESC management in this context is not restricted to physical structures but also includes work practices and methodologies. Regular monitoring will be undertaken by the Environmental Manager, ESC Specialist or Project Manager to ensure ESC measures are operating as designed and are maintained in accordance with guidelines and consent conditions. This monitoring underpins the successful implementation of the ESC management system, to achieve the anticipated environmental outcomes and ensure compliance with the resource consent conditions. This monitoring includes pre- and post-rainfall checks and maintenance and is considered "business as usual". The monitoring will also provide continual feedback to ensure successful ESC performance and early detection of activities or problems that have the potential to result in an adverse environmental effect. The frequency of the monitoring will vary throughout each construction phase and reflect areas of changing activity and risk within the Project. During active construction in a given area, the monitoring will be undertaken daily as well and pre and post rainfall events. Monitoring will report any repairs or issues that need to be addressed and the timeframe for completion of those actions. The regular monitoring will be supported by monitoring of the chemical treatment systems, weather, rainfall events, and will include wet weather responses and contingencies. 8.2. Performance Targets The ESC design seeks to meet the following four targets listed below. These reflect current best practice and the existing total suspended solids (TSS) / turbidity relationship established for existing consents associated with the construction and operation of TSF1A. • An average sediment retention pond efficiency of 90%. • Turbidity of 110 NTU (based on the existing relationship of 100g/m3 TSS = 110 NTU). • Clarity of 100mm. • pH between 6.0 and 9.0. The parameters would be measured by manual sampling in response to a rainfall trigger event of 25mm / 24 hours. That event is of a size that places stress on the SRP i.e. it is ‘working hard’. Water samples will also be taken at those times and analysed for turbidity and pH. These targets should not be adopted as compliance standards as doing so would be inconsistent with the function of TR2009/02 compliant devices and would be unnecessary to achieve overall acceptable water quality performance. The assumed efficiency of SRPs is based on measured15 average performance throughout storms and across a range of storms. The actual performance at any given stage of a storm varies in response to a range of factors, including: • Intensity and duration of the rainfall event. Small events may not cause a discharge. Conversely, as larger events engage multiple decants, primary and sometimes secondary 15 Performance of a Sediment Retention Pond Receiving Chemical Treatment; Auckland Regional Council, July 2008 On-site monitoring at Ara Tūhono - Pūhoi to Wellsford Road of National Significance: Pūhoi to Warkworth Section On-site monitoring at Milldale Stages 2 – 4, Wainui.
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