BASIC ASSESSMENT PROCESS FOR THE PROPOSED REHABILITATION AND - - PowerPoint PPT Presentation

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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

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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

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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

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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

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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

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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

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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

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PROPOSED CONSTRUCTION METHODOLOGY – Lowering of the spillway

Existing spillway of the upper dam will be lowered by 0.45 m in

• rder 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

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Lowering of the spillway

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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

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Desilting

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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

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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

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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

December 2014 Listing Notice 1: Activity number 19. The infilling or depositing of any material of more than 5 cubic 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.

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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)

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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

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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

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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

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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

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BA REPORT Key findings (cont.)

• Terrestrial ecology: Man-made stormwater attenuation Dam

surrounded by transformed parkland - not a conservation worthy site (EMM EMF 2007). Plants are mainly cosmopolitan weeds with little indigenous fauna

• Agricultural potential: None (EMM EMF 2007)
• Social: Although a popular recreational area, its popularity has

diminished due to aesthetics and odours

• Cultural and historical: No important and irreplaceable

cultural or historical worthy sites

• Property values: Two medium density “up-market lifestyle”

residential estates surround the Dam

• Safety: Concern that the lower dam wall may break during a

flood, especially if the temporary spillway bypass becomes so eroded that it too collapses under the pressure of floodwaters. This presents a safety risk to downstream property, as well as human and animal life

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BA REPORT Key findings (cont.)

• Functioning of the Dam in the greater stormwater system:

Presently not functioning well for flood attenuation and augmentation of downstream flows. This is due to the existing spillway not allowing enough water through, as well as the Dam being heavily silted. At times, the floodwaters back up into the Quinine Street stormwater system

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BA REPORT Key potential impacts assuming mitigation

• Aquatic ecology: Impacts related to alteration in surface water

quality, geomorphology and aquatic biota can be mitigated, either through avoidance and preventative action - Low positive for all the activities during the construction phase becoming a positive impact in the longer-term (operational phase)

• Terrestrial ecology: Impacts related to alteration in terrestrial

ecology can be mitigated, especially during the construction phase, either through avoidance or through preventative action. Low positive impacts for all activities

• Social: Low positive impact on the general aesthetics of the

Dam in the short-term, which in turn should have a positive impact on it’s use as a recreational area in the short- to medium-term

• Property values: Low positive impact on property prices within

the Estates in the medium-term

• Safety: Medium positive impact on downstream safety. If

Alternative 4 is implemented it will have a further positive impact of a Low significance on safety and security within the PoS and the Estates

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BA REPORT Key potential impacts assuming mitigation

• Functioning of the Dam in the greater stormwater system:

Positive impact of a Medium significance with mitigation on the functioning of the Dam within the stormwater management system of the greater area. The main positive influence would be that the Quinine stormwater outlet would be open

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BA REPORT Conclusions

• Blue Gill Dam plays a role in water purification and pollutant

assimilation, as well as flood attenuation and downstream flow augmentation

• Rehabilitation and engineering activities proposed will have a

positive impact on the ability of the system to provide these services

• Proposed project (incl. Alternative 4 as the upgrade alternative

for the existing spillway) should also have a low positive impact

• n the general ecology and aesthetics of the Blue Gill Dam and

surrounding area, which in turn should have a positive impact

• n its use as a recreational area in the short-term and the

property prices within the Estates in the medium-term

• Proposed project should reduce the safety risk of downstream

flooding should any of the existing structures fail during a high- rainfall event, as well as improve security within the PoS and the Estates, given that the inlet culverts under Veld Street will be filled with water, and less likely to be used as a thoroughfare for criminals

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BA REPORT Conclusions

• Proposed alternatives do not pose any difference in likely risks

and potential negative impacts to the receiving environment due to the absence of sensitive aquatic and terrestrial biota

• Alternative 4 is the favoured alternative for the upgrade to the

existing spillway

• ‘No-go’ alternative is not recommended given the:
• importance of the Dam in the overall stormwater system
• value that the PoS can potentially bring to local residents
• potential safety risks of the dam walls collapsing and the
• security risks of a breach in the security system of the inlet

valves under Veld Street

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PUBLIC CONSULTATION

Information about the proposed project and BA process was disseminated via:

• Pre-application Meeting with GDARD (20 May 2015)
• Site notices (Aug 2015 and Feb 2016)
• Notices placed at public places (Feb 2016)
• Bulk SMS system to all owners and residents of the Blue Gill and

The Waterfront Estates (the Estates)

• Newsletters disseminated to all owners within the Estates (Aug

2015 and Feb 2016), as well as Glen Erasmia Estate (Feb 2016)

• Site visit held with the Manager of the Estates (19 May 2015)
• Key Focus Group meeting with the BGHOA (12 Aug 2016)
• Site visit held with the Engineer and Mr. Kobus Otto (BGHOA) and

the Manager of the Estates (15 Oct 2015)

• Manager the Estates and the BGHOA in the normal course of their

duties as well as at their AGM (28 Sept 2016)

• Ward Councillors - Ward 15 (Ms. Roos) and Ward 100 (Mr.

Henning)

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PUBLIC CONSULTATION

• Advertisement in the local newspaper – The Kempton Express

(3 March 2016)

• Letter to all 187 registered I&APs (Feb 2016)
• Letter to Organs of State (Feb 2016)
• Draft documents made available on the internet

(www.bluegillestate.co.za/ notice board)

• Letter to all registered I&APs advising them of the extension to the

Comment Period – now closing 4 April

• Public Meeting (14 March 2016)

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PUBLIC CONSULTATION

Comment received in the Pre-application phase included:

• Requests for the proposed project to go-ahead asap
• Request for the temporary spillway bypass to be repaired and

the Dam to be reinstated to what it was like before 2010 i.e. before work on the Quinine Road culvert had commenced

• Deterioration of the Dam’s ecological state
• Decrease in the general aesthetics of the Dam, resulting in the

Dam not being used to its full potential as a recreational asset, as well as having a long-term negative impact on property values within the Estates

• Increased pollution levels in the Dam, as a result of polluted

stormwater inflow as well as sewerage

• Complaints of unpleasant odours
• Safety concerns as the dam wall of the lower dam is damaged
• Need for engineers and contractor to have the necessary

expertise and experience

• Public consultation process

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WAY FORWARD

• Draft Reports are available for comment from 29 Feb to 4

April (34 days)

• 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 review and decision
• Appeal Period
• Work on site commences (if decision is positive and no

appeals/ appeals dismissed)

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DISCUSSION

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THANK YOU

Contact details: Jaana Ball (EAP) jaanaball@gmail.com 0836505489