FRESHWATER RESOURCE ECOLOGICAL ASSESSMENT AS PART OF THE WATER USE LICENSE APPLICATION REQUIREMENTS FOR THE PROPOSED OUTFALL SEWER NETWORK IN HELDERFONTEIN, NEAR MIDRAND, GAUTENG PROVINCE Prepared for Nali Sustainable Solutions (Pty) Ltd March 2017 Revised December 2017 Prepared by: Scientific Aquatic Services Report author: A. Mileson Report reviewer: S. van Staden (Pr. Sci. Nat) Report reference: SAS 217025 Date: March 2017 Revised: December 2017 Scientific Aquatic Services CC CC Reg No 2003/078943/23 Vat Reg. No. 4020235273 PO Box 751779 Gardenview 2047 Tel: 011 616 7893 Fax: 086 724 3132 E-mail: [email protected] SAS 217025 March 2017 EXECUTIVE SUMMARY Based on the findings of the freshwater resource assessment and the results of the risk assessment, it is the opinion of the ecologist that although the proposed development poses a risk to a portion of the wetland systems (i.e. where the linear development will cross the systems) and may potentially impact negatively on a very small portion of the riparian zone associated with the Jukskei River, these risks can be satisfactorily mitigated. Adherence to cogent, well-conceived and ecologically sensitive site development plans, and the mitigation measures provided in this report as well as general good construction practice, will greatly reduce the significance of perceived impacts. It is the opinion of the specialist therefore that the proposed linear development, from a freshwater resource conservation perspective, be considered favourably, with the proviso that strict adherence to mitigation measures is enforced, in order to ensure that the ecological integrity of the freshwater resources is not further compromised. MANAGEMENT SUMMARY Scientific Aquatic Services (SAS) was appointed to conduct a freshwater resource ecological assessment as part of the Water Use License Application (WULA) requirements for the proposed sewer network in Helderfontein, near Midrand, within the Gauteng Province. The planned sewer network comprises two options, specifically Outfall Sewer Option 1 and Outfall Sewer Option 2 (preferred by the proponent), which will henceforth collectively be referred to as the “study area”. The study area is situated immediately south of Erling Road, immediately east of the R511 roadway, approximately 830m east of the Dainfern Valley and 2.3 km south west of the Kyalami Agricultural Holdings (AH). The study area is located within a moderately developed area, with the immediate surrounding areas comprising mainly residential cluster developments and open degraded veld areas. The Jukskei River, a perennial river system, is situated along the entire Outfall Sewer Option 2. The purpose of this report is to define the ecology of the study area in terms of freshwater resource characteristics, mapping of the freshwater resource, defining areas of increased Ecological Importance and Sensitivity (EIS), and to define the Present Ecological State (PES) of the freshwater resource associated with the study area, as well as to define the socio-cultural and ecological service provision of the freshwater resource and the Recommended Ecological Category (REC) for the freshwater resource. It is a further objective of this study to provide detailed information to guide the proposed project activities in the vicinity of the freshwater resource, to ensure that the ongoing functioning of the ecosystem, such that local and regional conservation requirements and the provision of ecological services in the local area are supported while considering the need for sustainable economic development. The assessment took the following approach: A desktop study was conducted, in which possible wetlands/freshwater resources were identified for on-site investigation, and relevant national and provincial databases were consulted. The results of the desktop study are contained in Section 3 of this report; A field assessment took place in early March 2016, in order to ground-truth the identified freshwater resources within the study area. Three watercourses were identified and classified according to the classification system (Ollis, et al.,2013) within the study area; and The detailed results of the field assessment are contained in Section 4 of this report and are summarised in the table below. ii SAS 217025 March 2017 Table A: Summary of the results of the field assessment Recommended Freshwater Present Ecological Ecological function Ecological Importance Ecological Class Resource State (PES) Category and service provision and Sensitivity (EIS) (REC) Eastern wetland E Intermediate C – moderate EIS D system Northern wetland C/D Intermediate C – moderate EIS C system Jukskei River E (IHI) and D (VEGRAI) Intermediate C – moderate EIS D Following the assessment of the freshwater resources associated with the study area, a risk assessment was performed to ascertain the significance of potential impacts on the receiving environment, and should the proposed linear development proceed. The risk assessment was undertaken based on the revised layout provided by the proponent. In addition, the risk assessment was undertaken based on the assumption that the strict enforcement of well-developed mitigation measures will be implemented throughout all phases of the proposed development. The results of the risk assessment are presented in Section 5 and Appendix F of this report, and are summarised in Tables B and C following the discussion below. Based on the findings of the risk assessment, several recommended mitigation measures are made to minimise the impact on the wetland ecology, as discussed in Section 5 and Appendix F of this report. Key measures include (but are not limited to): Whilst both Option 1 and Option 2 will impact on the northern wetland system, Option 2 will have a marginally lower impact on the system as it is adjacent to an existing road, and therefore is the “preferred” option; Areas which are to be cleared of vegetation, including contractor laydown areas, must remain as small as possible, in order to reduce the risk of proliferation of alien vegetation, and in order to retain a level of protection to the freshwater resources during construction (e.g. sediment trapping, slowing of stormwater runoff etc.). Contractor laydown areas are to remain outside of the delineated wetland and riparian zones and their associated buffers, and as much as feasible no natural/indigenous wetland vegetation is to be cleared. It is highly recommended that an alien vegetation management plan be compiled during the planning phase and implemented concurrently with the commencement of construction; A soil management plan must be compiled during planning, and implemented when construction commences. It is essential that the following be included in the soil management plan: All exposed soils are to be protected for the duration of the construction phase with a suitable geotextile (e.g. Geojute or hessian sheeting) in order to prevent erosion and sedimentation of the freshwater resources. This is considered essential as the soils in the vicinity are highly dispersive; No stockpiling of soils is to take place within the wetlands, riparian zone, or associated buffer zones, and stockpiles may not exceed 2m in height; and Any remaining soils following the completion of construction activities are to be levelled and re-seeded with indigenous flora species to minimise the risk of further sedimentation of the wetland, and to aid in the natural reclamation process. The pipeline must be encased in precast concrete at the pipe jacked crossing points; All manholes are to be raised above the 1:100 year floodline; and Upon the completion of construction the pipeline must be pressure tested. Based on the findings of the freshwater resource assessment and the results of the risk assessment, it is the opinion of the ecologist that although the proposed development poses a risk to a portion of the wetland systems (i.e. where the linear development will cross the systems) and may potentially impact negatively on a very small portion of the riparian zone associated with the Jukskei River, these risks can be satisfactorily mitigated. Adherence to cogent, well-conceived and ecologically sensitive site development plans, and the mitigation measures provided in this report as well as general good construction practice, will greatly reduce the significance of perceived impacts. It is the opinion of the specialist therefore that the proposed linear development, from a freshwater resource conservation perspective, be considered favourably, with the proviso that strict adherence to mitigation measures is enforced, in order to ensure that the ecological integrity of the freshwater resources is not further compromised. iii SAS 217025 March 2017 Table B: Summary of the results of the risk assessment applied to the Jukskei River. No. Phases Activity Impact Risk Rating 1 Site clearing prior to commencement of construction Exposure of soils, leading to increased runoff and erosion, and thus increased sedimentation of the river. activities. Increased sedimentation of instream habitat, leading to smothering of aquatic biota and potentially altering surface water quality. L Decreased ecoservice provision. Damage to vegetation, leading to exposed/compacted soils, in turn leading to increased runoff and erosion. Decreased ecoservice provision. L Decreased ability to support biodiversity. 2 Groundbreaking, excavation of trench within the Disturbances of soils leading to increased alien vegetation proliferation, and in turn to