BASIC ASSESSMENT PROCESS FOR THE PROPOSED REHABILITATION AND ENGINEERING MEASURES AT THE BLUE GILL DAM, KEMPTON PARK GDARD REF. No.: 002/15-16/E0244 Public Meeting 14 March 2016 Slide 1
AGENDA 1. Welcome and introduction 2. Project Proposal and Rationale 3. BA process 4. Findings 5. Recommendations 6. Public consultation 7. Way forward 8. Discussion 9. Meeting close Slide 2
HOUSE ETIQUETTE • Language of choice • Work through the chair • Focus on EIA related issues • Equal participation • Identify yourselves prior to a question or comment • Wait until discussion session to ask questions • Cell phones off please Slide 3
PROJECT DETAILS • Project Proponent is the Ekurhuleni Metropolitan Municipality (EMM) – Mr. Swart, Chief Director – Roads and Stormwater • Project Engineer is CivEc • Environmental Assessment Practitioner is Mrs Jaana Ball • The site is located at Blue Gill Dam, Glen Marais within Erf 2255 (zoned PoS) • Off Veld Street, Kempton Park, Gauteng • Site is surrounded by the Blue Gill and The Waterfront Housing Estates (the Estates) • Located on an un-named non-perennial tributary of the Rietvlei system and in the quaternary catchment A21A of Crocodile- west and Marico Water Management Area • Proposed project is to be undertaken in a phased manner during the dry seasons of 2016 and 2017 Slide 4
PROJECT RATIONALE • The Dam has become so silted that stormwater is ‘backing up’ into the Quinine Street stormwater system reducing the capacity of that system • The temporary spillway bypass (trench) needs to be reinstated • Concern over the siltation levels reducing the volume of water the Dam can hold • Concern that the lower dam wall will break and result in loss of life and property damage • The Dam has become colonised by alien invasive plant species and has become unattractive aesthetically • Sewerage is periodically overtopping the manholes covers causing odours and an unsightly mess Slide 5
PROJECT ACTIVITIES The following engineering and rehabilitation activities are proposed: • Upgrade existing spillway (Phase 1) • Close and reinstate the temporary spillway bypass between the upper and lower dams (Phase 1) • De-silt the upper dam (Phase 1) • Repair erosion near the inlet culverts that are located underneath Veld Street (Phase 1) • Reinstate/ rehabilitate the upper Dam (Phase 1) • Repair lower dam wall (Phase 2) Note: Phase 1 – dry-season 2016 Phase 2 – dry-season 2017 Slide 6
ALTERNATIVES FOR THE UPGRADE TO THE EXISTING SPILLWAY The following upgrade alternatives for the existing spillway are being assessed: • Alternative 1: Lower the existing spillway by 1 m between the upper and lower dams • Alternative 2: Construct a second smaller spillway 1 m deeper than the existing one between the two dams • Alternative 3: Construct a pipe within the temporary spillway bypass between the two dams and reinstate • Alternative 4: Lower the existing spillway by 0.45 m between the two dams • Alternative 5: Construct a second smaller but 0.39 m deeper spillway than the existing one between the two dams Slide 7
PROPOSED CONSTRUCTION METHODOLOGY – Lowering of the spillway Existing spillway of the upper dam will be lowered by 0.45 m in order to lower the permanent water level in the dam so that it is 100 mm deep at the Veld Street culvert outlets Activities proposed: Breaking of concrete across the full length of the existing concrete spillway crest, 6 m wide and approx. 760 mm deep to a new elevation level of 1603.350 m Perpendicular saw cut along the outer face of the existing concrete apron for the secure construction and placement of a new Reno mattress structure Construct a new 300 mm thick Reno mattress across the full length and width of the newly excavated concrete level in order to achieve a top of spillway level of 1603.650 m BIDIM A5 to be placed behind and under all Reno mattresses Finish off and fill gaps between outer face of the concrete apron and Reno mattresses with 25 MPa concrete Slide 8
Lowering of the spillway Slide 9
PROPOSED CONSTRUCTION METHODOLOGY – Desilting The upper dam will be de-silted and the surrounding area rehabilitated by completing the following activities: • Excavate material along the dam edges to achieve a 1:2 embankment slope along the edge of the dam – 17 m in (maximum reach of excavator) • In addition to the 17 m strip all the material in the upstream portion of the dam shown below will be de-silted. This will result in an uninterrupted body of water from the inlet to the spillway • Clean all hydraulic structures Slide 10
Desilting Slide 11
PROPOSED CONSTRUCTION METHODOLOGY – Construct the silt trap A silt trap will be constructed across the upper dam to facilitate future de-silting and to keep the balance of the dam clean. The following activities will be required: • Excavate the existing material 1 m wide to an elevation level of 1602.850 m • Construct and place a single row of gabion blocks, 1 m wide by 1 m long by 1 m high along new excavated trench • Place BIDIM A5 behind and under all gabion blocks Slide 12
PROPOSED CONSTRUCTION METHODOLOGY – Lower dam spillway The spillway of the lower dam will be rehabilitated as a second phase by replacing the existing concrete structure with a gabion structure Slide 13
BA PROCESS • Basic Assessment Process (and not Full EIA) required in terms of the National Environmental Management Act (NEMA 107 of 1998 (as amended) and EIA Regulations 2014 • Activity triggered within Listing Notice 1: GN. R 983, 8 Listing Notice 1: The infilling or depositing of any material of more than 5 cubic December 2014 Activity number 19. metres into, or the dredging, excavation, removal or moving of soil, sand, shells, shell grit, pebbles or rock of more than 5 cubic metres from- (i) A watercourse; (ii) The seashore; or (iii) The littoral active zone, an estuary or a distance of 100 metres inland of the high-water mark of the sea or an estuary, whichever distance is the greater- But excluding where such infilling, depositing, dredging, excavation, removal or moving- (a) Will occur behind a development setback; (b) Is for maintenance purposes undertaken in accordance with a maintenance management plan; or (c) Falls within the ambit of activity 21 in this Notice, in which case that activity applies. Slide 14
BASIC ASSESSMENT PROCESS The aim of the BA process is to: • Identify potential impacts (negative, positive and neutral) of the proposed rehabilitation and engineering activities, as well as cumulative impacts • Identify any potential mitigation measures/ management actions to avoid or reduce any potential negative impacts • Obtain the views and issues of Organs of State, as well Interested and Affected Parties (I&APs) Slide 15
BASIC ASSESSMENT PROCESS Pre-application activities • Site visit • Pre-Application Meeting with GDARD and record • Collect data, collate maps and plans, obtain consent from landowner, obtain declaration from Applicant and EAP • Appoint independent Freshwater Ecologist • Compile I&AP register • Distribute letter of notification and background information • Erect site notices • Place advert in local newspaper • Complete Draft Basic Assessment (BA) Report and Environmental Management Programme (EMPr), incl. Aquatic Ecology Study, and submit to GDARD, and make available to Organs of State and I&APs for 30-day Comment Period • Public meeting Slide 16
BASIC ASSESSMENT PROCESS Post application activities • Submit BA Application Form to GDARD • GDARD acknowledgement of receipt of Application • Incorporate public comments into Final BA Report • Amend documents based on comments received • Disseminate Final BA Report and EMPr (if required) • 30-day post application commenting period (if required) • Submit Final BA Report and EMPr to GDARD • GDARD commenting period and decision • Appeal Period • Work on site commences if decision is positive and no appeals/ appeals upheld Slide 17
BASIC ASSESSMENT PROCESS Outputs • Basic Assessment Application Form (standard format) • Basic Assessment Report (standard format) with appendices such as EAP details, PPP documentation, Correspondence with I&APs and GDARD • Aquatic Ecology Report • Draft Environmental Management Programme Slide 18
BA REPORT Key findings • Water Quality : The Dam is characterised by a circum-neutral pH with low salt loads. An increasing turbidity gradient exists from the inflow to the outflow, suggesting an increase in primary production and trophic status in the same direction • Diatoms: Diatoms comprise of species characteristic of alkaline, fresh-brackish, eutrophic waters with moderate oxygen levels. The downstream site sampled is less impacted compared to the upstream site. Diatoms comprised mostly of highly pollution tolerant species • Aquatic macroinvertebrates : System reflected a very low aquatic macroinvertebrate diversity and a high abundance of Chironomidae , indicative of a low oxygen environment and water that has a high level of pollution. A marginal increase in invertebrate diversity and sensitivity was noted along the longitudinal profile of the Dam • Fish: Fish community is transformed and dominated by introduced species. Three indigenous species, tolerant to changes in habitat, flow and water were sampled Slide 19 •
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