HELMSLEY COUNTRY ESTATE RESIDENTIAL DEVELOPMENT … · 2019. 1. 9. · Section C3.1 Sanitation...

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THE HELMSLEY DEVELOPMENT COMPANY

PRELIMINARY ENGINEERING DESIGN REPORT FOR

HELMSLEY COUNTRY ESTATE RESIDENTIAL DEVELOPMENT

VOLUME 1

MAY 2018

Compiled for:

The Helmsley Development Company

Saxe Farm,

Umhlali, 4390

P O Box 263

Umhlali, 4390

Tel: (032) 942 2066

Attention: Mr S Hulett

Compiled by:

BIGEN AFRICA Services (Pty) Ltd

Block B, Bellevue Campus

5 Bellevue Road, Kloof, 3610

PO Box 1469

KLOOF, 3640

Tel: +27(0)31 717 2571

Fax: +27(0)31 717 2572

e-mail: [email protected]

Enquiries: Mr B. Oosthuizen

mailto:[email protected]

Helmsley Country Estate - Residential Development Internal Engineering Services: Preliminary Design Report Contents List

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THE DEVELOPMENT COMPANY

HELMSLEY COUNTRY ESTATE – RESIDENTIAL DEVELOPMENT

INTERNAL ENGINEERING SERVICES:

PRELIMINARY DESIGN REPORT

CONTENTS LIST

PRELIMINARY ENGINEERING DESIGN REPORT

Executive summary

Contents list

Part A General Matters

Section A1 Project brief and project team

Section A2 Terms of Reference

Section A3 Assessment Information Basis

Section A4 Project Details

Section A5 Other Reports and Assessment Information

Part B Natural Environment

Section B1 Geographical Location and Topography

Section B2 Geological and geotechnical aspects

Section B2.1 Site Geology

Section B2.2 Landform

Section B2.3 Slope Stability

Section B2.4 Founding

Section B2.5 Groundwater Conditions

Section B2.6 Excavatability/Trenchability

Section B2.7 Sub-soil Drainage

Section B2.8 Stormwater Management

Section B2.9 Pavement Sub-grade characteristics

Section B2.10 Conclusions

Section B3 Environmental and cultural/historical issues

Section B3.1 Environmental

Section B3.2 Cultural/Historical


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Part C Layout and planning

Section C1 Development Profile and Planning Issues

Section C1.1 Development Boundary

Section C1.2 Planning Approval

Section C1.3 Spatial Impact

Section C1.4 Topography

Section C1.5 Existing Land Uses

Section C1.6 Provincial Roads

Section C1.7 Geological Stability

Section C1.8 Land Use Requirements

Section C2 Bulk and link services

Section C2.1 Institutional Arrangements

Section C2.2 Bulk Water

Section C2.3 Bulk Sanitation

Section C2.4 Bulk Roads

Section C2.5 Stormwater Drainage

Section C2.6 Bulk Electricity

Section C2.7 Telecommunications

Section C2.9 Waste Removal

Section C3 Internal engineering services

Section C3.1 Sanitation scheme

Section C3.2 Water supply scheme

Section C3.3 Road Infrastructure

Section C3.4 Stormwater Infrastructure

Section C3.5 Electricity & Street Lighting

Section C3.6 Telecommunications

Section C3.7 Solid Waste Removal/Collection

Section C3.8 Maintenance

Part D Conclusions and Recommendations

Section D1 Phasing of Implementation

Section D2 Conclusion

Section D3 Bulk Water Supply

Section D4 Bulk Sewage Treatment Facility

Section D5 Bulk Electrical Supply

Section D6 Bulk Telecommunications Supply

Section D7 Internal Services


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Part E Programme and Financing

Section E1 Programme

Section E2 Capital Costs

Part F Appendices

Annexure F1 Locality Maps

Annexure F1.1 Regional Context

Annexure F1.2 Local Context

Annexure F1.3 Project Context

Annexure F2 Development Diagrams

Annexure F3 Geotechnical Site Plan

Annexure F3-1 Geotechnical Zonation Plan

Annexure F3-2 Hydrological Wetland

Annexure F4 Slope Analysis

Annexure F5 Land Use Plan

Annexure F6 Electrical Supply

Annexure F7 Water Reticulation Analysis

Annexure F8 Cost Schedules

Annexure F9 Project Programme

Annexure F10 Project Cash Flow

Part G Report Drawings (Please refer to Volume 2)

Part G1 Roads

0938.00.ZA.03A001 Road Servitude Layout

0938.00.ZA.03A002 Access Road Watercourse Crossing

0938.00.ZA.03D001 Typical Services Servitude Details

0938.00.ZA.03D002 Typical Pavement Design Details

0938.00.ZA.03D004 Position of Support Brackets & Installation details of Road

Signs

0938.00.ZA.03D005 Road Marking Details

0938.00.ZA.03D006 Road Signage Schedule

0938.00.ZA.03S001 Road Layout Keyplan

0938.00.ZA.03U001 Road Layout Detail & Setting out Data – Sheet 1 of 3



0938.00.ZA.03S002 Road Markings and Road Sign Layout Keyplan

0938.00.ZA.03U004 Road Markings & Road Sign Layout – Sheet 1 of 3



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0938.00.ZA.03L001 Road Long Section Road 1 CH 0.000 – CH 560.000



Road 2 CH 0.000 – CH 197.475



Road 4 CH 0.000 – CH 183.654

Part G2 Stormwater

0938.00.AA.04A001 1:100 Year Floodline

0938.00.AA.04A002 Orthophoto indicating perennial/non-perennial streams/

rivers

0938.00.AA.04A003 Topographic map indicating perennial/non-perennial

streams/rivers

0938.00.AA.04A006 Stormwater Master Plan

0938.00.ZA.04D001 Typical Kerb Inlet Details

0938.00.ZA.04D002 Manhole & Surface Stormwater Collection manhole Details

0938.00.ZA.04D003 Typical Kerbing Details

0938.00.ZA.04D004 Pipe Bedding Details: Rigid Pipes Class A, B, C and D

0938.00.ZA.04D005 Underdrain Details for Stormwater Trenches

0938.00.ZA.04D006 Wingwall Brickwork Details

0938.00.ZA.04D007 Low level river crossing, cover slab with guide block

Part G3 Water Supply

0938.00.ZA.05S001 Water Reticulation Layout Keyplan

0938.00.ZA.05U001 Water Reticulation Layout – Sheet 1 of 3



0938.00.ZA.05D001 Pipe Bedding Details: Rigid Pipes Class A, B, C and D

0938.00.ZA.05D002 Typical Excavation & Backfill Details for Water Pressure

Pipes

0938.00.ZA.05D003 Typical Excavation and Backfill Details for Rigid Water

Pressure Pipes (Trough Road Pavement)

0938.00.ZA.05D004 Typical Underdrain Details for Water Trenches

0938.00.ZA.05D005 Detail of Backfilling prior to the testing of Pipes

0938.00.ZA.05D006 Concrete Encasement of Pressure Pipes (uPVC)

0938.00.ZA.05D007 Thrust Block Details and Graph

0938.00.ZA.05D008 Water Pipeline Markers (Option 1)

0938.00.ZA.05D009 Water Pipeline Markers Type 1 and Type 2

0938.00.ZA.05D010 Typical Pillar Fire Hydrant

0938.00.ZA.05D011 Typical Double Headed Pump Booster Connection


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0938.00.ZA.05D012 Typical Chamber for Hydrant Suction Valve

0938.00.ZA.05D013 Typical Valve Chamber for pipes 50Ø>D 2150 (Concrete Cover)

0938.00.ZA.06D010 Manhole when D > 2150 (Concrete Cover)

0938.00.ZA.06D011 Section: Drop Manhole – When IL 1– IL 2 < 840mm

0938.00.ZA.06D012 Section: Drop Manhole – When IL 1– IL 2 > 840mm

0938.00.ZA.06D013 General Precast Base Details

0938.00.ZA.06D015 Typical Cast-Iron Sewer Rodding Eye

0938.00.ZA.06D016 House Connection (uPVC) D < 1200

0938.00.ZA.06D017 House Connection (uPVC) 1200 < D < 2000

0938.00.ZA.06D018 House Connection (uPVC) D > 2000: Plan

0938.00.ZA.06D019 House Connection (uPVC) D > 2000: Section

0938.00.ZA.06D020 Anchor Blocks for Steep Slope Sewers


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0938.00.ZA.06D021 Sewer Connection Marker Block Details

0938.00.ZA.06D022 Concrete Encasement of uPVC Sewer Pipes &

Reinforced Concrete Encasement of uPVC Sewer Pipes

Part G5 Electrical

0938.00.ZA.07A001 Electrical Bulk Suppl

0938.00.ZA.07A002 Internal Electrical Supply

Part G6 Fencing

0938.00.ZA.17U001 Proposed Fencing Layout

Part H Bulk Water and Sanitation (Please refer to Volume 2)

Annexure H1 Regional Bulk Water Supply

Annexure H2 Geotechnical Reports 1 & 2

Annexure H3 Water and Sanitation Flow Diagram and Layouts

Annexure H4 Pumphouse and Pumpstation Pipe Configuration

Annexure H5 Water Treatment Works Layout

Annexure H6 Water Treatment Works Process

Annexure H7 Low Lift Pumpstation and Chemical Storage

Annexure H8 WWTW Site and Bulk Gravity Sewer Layout Plan

Annexure H9 WWTW Flow Diagram

Annexure H10 Final Effluent End Structure Wingwall

Helmsley Country Estate - Residential Development Internal Engineering Services: Preliminary Design Report Executive Summary

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HELMSLEY COUNTRY ESTATE – RESIDENTIAL



Executive Summary

Background and Locality of Project

The Client of The Helmsley Development Company, also acting as the Developer of the proposed

project, has appointed Bigen Africa Services (Pty) Ltd to undertake the design and construction

monitoring of the bulk and internal engineering services for the Helmsley Country Estate development.

The proposed 21,0801ha residential housing estate will deliver some 125 housing opportunities, of

which 32 will be full title individual special residential type I stands and 93 sectional title units on 5

medium density residential type II and III stands.

The property is situated on Portion 177 (of 161) of the Farm Compensation No. 868, Registration

Division PU, located along the north coast of KwaZulu-Natal, in the vicinity of Compensation. The site

is located directly adjacent to road D176 which traverses through the north eastern section of the site

and then runs in a north westerly direction at a distance that varies between 50m to 200m from the

north eastern boundary of the original farm. The Helmsley farm is located approximately 6,2km north

west of Ballito and the N2 north highway which forms the main development corridor between Durban

and Richards Bay running approximately 2km west of Ballito.

Geotechnical Investigation

From the basis of the hydromorphic wetland mapping and a preliminary geotechnical assessment, the

following are the key developmental considerations and findings:

● Stable and satisfactory for development which is considered feasible subject to the adoption of

suitable development controls to engineer’s details;

● Development along any slopes steeper than 1 vertical: 3 horizontal (> 18°) and any 1:100 year

floodline is not recommended;

● Hydromorphic wetland areas have been mapped along the south-eastern valley of the site. A

provisionally 20 metre wide environmental setback indicated around the “temporary” wetland area

should be verified by the Department of Agriculture and Environmental Affairs in consultation with

Ezemvelo KZN Wildlife;



● Soakpits should not be employed for the disposal of either stormwater or sewage;

● A mini sewage package plant or communal conservancy tanks should be planned;

● Guidelines are given on appropriate founding solutions which will require further investigation and

engineers design;

● Effective stormwater management will minimise maintenance of the slopes.

It is considered that the design of the civil engineering infrastructure and foundations should be based

on a detailed geotechnical subsurface site investigation.

Archeological Assessment

A preliminary archaeological assessment was undertaken by eThembeni Cultural Heritage in

September 2005 to report on the proposed development site. Two heritage resources of significance

were identified. The first of which (Site A, being a Late Iron Age hilltop settlement) would require further

assessment to determine its significane. The second (Site B) being an ancestral grave, would require

protection from disturbance of any sort or a permit from Amafa. It is however, to be noted that the

eThembeni Report to Amafa aKwaZulu Natali indicates that further survey is required once the cane is

harvested.

Conclusions and Recommendations

Based on the various investigations that were conducted on the proposed development site, we

conclude the following :

- The construction of civil and electrical infrastructure to service the proposed layout planning is

feasible. However, the costs are significantly higher than the average. This is largely attributed to

the relatively small size of the development and the required bulk and link services complement;

- Access to the higher order road infrastructure network is possible;

- There are no adverse geotechnical conditions that would prohibit the proposed development;

- There are no municipal bulk and link water and sanitation services currently available in the area;

- The provision of bulk electrical infrastructure depends on close co-operation with the KwaDukuza

Local Municipality and other developers, or development initiatives, in the area;

- Nevertheless, notwithstanding the abovenoted challenges, the proposed development can in the

interim, almost be entirely self sufficient within the various bulk water services options recommended

and investigated for implementation.

In terms of which, it is hereby recommended that the following servicing options be adopted for the

development of the proposed Helmsley Country Estate.

The operation and maintenance of the internal roads network, bulk sewage treatment, internal

sewerage reticulation, bulk water supply and internal water reticulation within the proposed residential



housing estate will be the responsibility of the Home Owners Association/Body Corporate, unless

otherwise agreed to with the relevant services authority in terms of the Service Level Agreements (SLA)

that have been entered into between the respective parties.

The electrical reticulation is the only municipal service and will be operated and maintained by the

KwaDukuza Local Municipality.

Summary of Estimate of Costs

Total Project Costs

* Internal Infrastructure

* Bulk Infrastructure

* Professional Fees

R

R

R

27 674 494,29

45 786 857,42

5 866 960.80

* Total Infrastructure R 79 328 312.51

Costs per Unit

* Housing Estate (125 units)

R

634 626.50

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Part A General Matters

Section A1 Project Brief and Project Team

The Client, The Helmsley Development Company, also acting as the developer, has

appointed Bigen Africa Services (Pty) Ltd to undertake the design and construction

monitoring of the bulk and internal engineering services for the Helmsley Country

Estate development. This portion of the now proclaimed residential property has been

subdivided from the surrounding John Albert Trust farmland and has been earmarked

as a stand alone Country Estate development that is surrounded by a Macadamia Nut

Production Farm.

The proposed residential housing estate will deliver some 125 housing opportunities,

of which 32 will be full title individual special residential type I stands and 93 sectional

title units on 5 medium density residential type II and III stands.

The property is situated on the north coast of KwaZulu-Natal, in the vicinity of

Compensation. The site is located directly adjacent to road D176 which traverses

through the north eastern section of the site and then runs in a north westerly direction

at a distance that varies between 50m to 200m from the north eastern boundary of

the original farm. The Helmsley farm is located approximately 6,2km north west of

Ballito and the N2 north highway which forms the main development corridor between

Durban and Richards Bay running approximately 2km west of Ballito.

Bigen was originally requested to investigate and report on any formal planning that

was underway for the maintenance and upgrading of the existing bulk and link

infrastructure and/or the provision of any new bulk or link services that may influence

the proposed development area, either by other developers or by one of the municipal

authorities having jurisdictional authority over this area, namely the ilembe District

Municipality and/or the KwaDukuza Local Municipality.

From the various investigations and studies that have been conducted in the area, it



has been concluded that there are no existing or planned new bulk infrastructure

available in the area in the short to medium term.

Further, all the internal and link civil and electrical infrastructure shall have to be

provided by the Developer as part of the proposed development application, at the

prescribed levels of service recorded in this report, as well as the Service Level

Agreements (SLA’s) entered into by the Developer with the respective Services

Authorities having powers and sanction over the development area.

Property Information:

From the subdivisional diagrams for the Helmsley Country Estate - Portion 177 (of

161) of the farm Compensation no. 868, Registration Division FU, Province of

KwaZulu-Natal, comprises of approximately 21,0801ha of the original 189,0027ha

John Albert Trust farm.

Section A2 Terms of Reference

Bigen Africa Services (Pty) Ltd have been appointed to design and monitor all the

consulting engineering services in respect of delivering the civil and electrical

infrastructure for the proposed development. The infrastructure includes water

supply, electricity supply, sewage disposal, streets and stormwater drainage facilities.

The following stand alone and/or separate reports and services agreements have

been compiled by Bigen Africa Services (Pty) Ltd and/or their specialist Services

Providers, and should be read in conjunction with this PED report :

▪ Traffic Impact Assessment – dated August 2007 and revised in October 2008

▪ Determination of 1 : 100 year floodlines (tributaries of the Wewe River) – dated

August 2007 and revised in October 2008

▪ Geophysical Investigation and Borehole Siting Report – dated 30 August 2007,

Ref. No. 2007/155 (Geomeasure Group)

▪ Final Geohydrological Report on the Drilling Pump Testing Water Quality

Analysis and Preliminary Reserve Determination for the proposed Helmsley

Housing Development, dated 3 March 2008, Ref. No. 2007/155 (Geomeasure

Group)

▪ KwaDukuza Local Municipality Services Agreement (Roads, Stormwater and

Electricity Services) and Addendum HG1 dated 15 August 2008 and

13 February 2018 respectively.

▪ iLembe District Municipality Services Agreement (Water and Sanitation Services)

dated 10 April 2017.



Section A3 Assessment Information Basis

Various discussions were held with the following services authorities over an

extended period of time in order to obtain information regarding the availability and

status quo of the existing bulk and link infrastructure, as well as any formal planning

underway in respect of the various services in the vicinity of the proposed

development area:

▪ Water : Ilembe District Municipality and Sembcorp Siza Water

▪ Sanitation : Ilembe District Municipality and Sembcorp Siza Water

▪ Roads (Provincial) : Department of Transport – KZN

▪ Roads (Local) : KwaDukuza Municipality

▪ Electricity : KwaDukuza Municipality and Eskom

▪ Stormwater Control : KwaDukuza Municipality

▪ Telecommunications: Telkom, Vodacom, MTN, Cell C & Virgin Mobile

▪ Solid Waste : KwaDukuza Municipality

The assessment of, as well as the comments received from the various services

authorities in respect of each service is contained in sections Part C of this report.

Section A4 Project Details

Project Funder : The Helmsley Development Company

Project applicant : The Helmsley Development Company

District Municipality : Ilembe District Municipality DC 29

Local Municipality : KwaDukuza Municipality KZN292

Project Manager : Lead Associates (Pty) Ltd (LA)

Civil Engineer : Bigen Africa Services (Pty) Ltd (BAS)

Electrical Engineer : Ibuya Consulting Engineers (Pty) Ltd (BAS)

Geotechnical Engineer : Groundwork Geotechnical Solutions cc (GGS)

Ground Water Consultant : Geomeasure Group (GG)

Town Planner : Helena Jacobs PSF (HJ) – original layout

Stott, Milton & Conway (SMC) – PUD layouts

Environmentalist : Sustainable Development Projects cc (SDP)

Land Surveyor : Stott, Milton & Conway Professional Land

Surveyors

The project name is : Helmsley Country Estate Residential Housing

Development

Number of Residential Units : 125 units

Project location within municipal



Ward : 4

Project area : 21,0801ha of the original 189,0027ha John Albert

Trust farm area

Section A5 Other Reports and Assessment Information

▪ Environmental Scoping Report – dated January 2006, Ref. No. EIA6241 (SDP)

▪ Preliminary Ecological Appraisal on the Establishment of a Macadamia Plantation

and Residential Development at Helmsley Farm – dated December 2005 (SDP)

▪ A Hydromorphic Delineation of Wetland areas and a Preliminary Assessment of

anticipated Geotechnical Conditions – dated October 2005, Ref. No. GS 59/05

(GGS)

▪ Preliminary Engineering Report – dated 6 December 2005 (SMW KwaDukuza

Consultants cc)

▪ Heritage Impact Assessment – dated 12 September 2005 (eThembezi Cultural

Heritage).

▪ Layout Plan – Ref. No. Helmsley 01 – 06 un-dated (HJ) October 2007.

▪ PUD’s Layout Plan – Ref. No. D17/R. Conway Dwg No. Full-LP3.

Helmsley Country Estate - Residential Development Internal Engineering Services: Preliminary Design Report Part B: Natural Environment

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Part B Natural Environment

Various specialist service providers, as noted in Section A4 have been appointed as

part of the professional team for the project in order to conduct the required studies

and surveys in respect of the natural environment for the proposed project area, which

includes the following:

Civil and Electrical Consultants;

Geotechnical Consultants;

Environmental Consultants;

Town and Regional Planners; and

Topographical and Land Surveyors.

Section B1 Geographical Location and Topography

The project area is located approximately 45km north-east of the Durban City Centre

(CBD) within ward 4 of the KwaDukuza Local Municipality. This, in turn, falls within

the ilembe District Municipality’s area of jurisdiction that stretches along the eastern

sea board on the north coast of KwaZulu-Natal and is bordered by the eThekwini

Metro to the south, Ndwedwe and Maphumulo Municipalities to the west, and the

Mandeni Municipality towards the north. The most prominent development centres in

close proximity to the site include the towns of Ballito approximately 10km towards

the south east, uMhlali and Stanger approximately 6km and 20km towards the north

east and Tongaat approximately 12km towards the south west of Helmsley

respectively. Please refer to the locality maps included in Annexure F1.

Further, the geographical location of the respective land parcels that make up the

proposed development area (project footprint) has been co-ordinated as a sngle point

of reference at the properties approximate centroid (refer to Table 1 below).

Furthermore, the properties consolidation, subdivisional diagrams and SG plans have

been obtained from the appointed land surveyor for this project and included in

Annexure F2.



Table 1: Geographical Location of PTN 161 of the farm Compensation No. 868

Land Parcel Name Municipal

Ward

Land Parcel

No.

Latitude Longitude

PTN 161 of the farm

Compensation No. 868

4 161 29°28’48” S 31°09’36” E

The project is located between approximate latitude 29°28’12” and 29°29’24” south and

longitude 31°09’00” and 31°10’12” east

The site generally slopes from the north-west towards the south-east. Drainage from

the elevated hillock on which the development has been located is governed by three

(3) non-perennial streams within the valley lines that drain towards the south eastern

corner of the farm where they converge into a single stream/tributary that eventually

joins up and flows into the Wewe river approximately 3km south of the project area.

A characteristic of the township layout is the elevated views over the Compensation

flats, and the feeling of ample wide open space that has been created by locating the

majority of the residential erven along the ridgeline of the farms isolated hillock.

Section B2 Geological and Geotechnical Aspects

A geological assessment was undertaken by Groundwork Geotechnical Solutions in

October 2005 which has been briefly summarised below. For a more detailed

overview in this regard, kindly refer to the specific report titled “A Hydromorphic

Delineation of Wetland areas and a Preliminary Assessment of anticipated

Geotechnical Conditions – dated October 2005, Ref. No. GS 59/05 (GGS)”.

Section B2.1 Site Geology

Due to the variable geology of the project area, the site has been divided into three

geotechnical zones. The typical nature of each of the geotechnical zones are

summarised below. The Geotechnical Site Plan, Ref. No. GS/84/05, Fig. No. G

attached as Annexure F3, illustrates the inferred extent of these geotechnical zones.

5.2.1 Alluvium

“Which is formed as organic soils along the bottom of the valley terrain”.

Alluvial sandy and silty clays are present typically along the outer edges and

central portions of the valley bottoms.

Seasonal and permanent standing water conditions are anticipated, resulting

in an organic-rich compressible soil.



5.2.2 Berea Formation (Q6)

“Presented as limited unconsolidated Aeolian (windblown) sandy to clayey

deposits along the elevated northern and north-western slopes”.

Former dune/Aeolian (windblown) deposits of the Berea Formation were

mapped and recorded along the uppermost northern and north-western

slopes.

From experience with similar soils on other sites, the above soils are known

to be favourably permeable, highly erodible and prone to collapse settlement

under loading when wet. The soils can also become unstable within steep

excavations eg. platform embankments.

5.2.3 Vryheid Formation (Pv)

“Comprising sandstone and siltstone bedrock and derived colluvial and

residual clays / clayey soils”.

Sedimentary siltstone and sandstone bedrocks belonging to the Vryheid

Formation where encountered over the majority of the site.

Section B2.2 Landform

A slope analysis of the entire farm (property) was undertaken by ourselves and the

majority of the proposed development area was found to be within the 0 – 20%

gradient range with small isolated areas reaching a maximum gradient of 25% along

the lower edges of the elevated development footprint perimeter (refer to

Annexure F4, for a copy of the slope analysis undertaken of the development area

onto which the layout plan has been superimposed).

Variation in elevation ranges between approximately 84m AMSL in the south eastern

sector of the site to approximately 184m AMSL along the northern boundary of the

farm.

Section B2.3 Slope Stability

As part of the geotechnical brief, the shallow slope stability has been assessed to

gauge the suitability of the site for development in terms of the prevailing slope

stability conditions.



On the basis of their observations, no evidence of a landslip in the recent past was

observed and the existing satisfactorily drained shallow slope conditions appear to be

inherently stable.

Provided good stormwater controls are maintained, and injudicious earthworks are

not attempted, gross slope instability at shallow levels is not expected.

Furthermore, satisfactorily stable development is considered feasible, provided

suitable development controls and guidelines recommended in this report are

implemented to the approval of the engineering and geotechnical professionals.

In broad terms, the planning and development controls on site would pertain to

carrying out the following :

- Slope analysis: In terms of shallow slope stability, development densities and

costs, it is considered that any slopes steeper than 18° (1 vertical: 3 horizontal)

display a significantly lower potential for development and should be excluded

from the estate scheme. It is advisable that a slope analysis is conducted to

determine the extent of any such steep slopes on site;

- Judicious earthwork design: Field measurements indicate that the bedrock

laminations of the Vryheid Formation are orientated typically to the southeast.

This characteristic should be taken into account if earthworks are carried out on

slopes with a south-easterly aspect. It is unlikely that the relatively mild to

moderately undulating nature of the majority of the slopes will incur costly

earthworks. Notwithstanding this, limits on heights and batters of building and

road platform embankments should be implemented as good practice. Use

should also be made of suitable retaining measures to engineer’s detail in any

critical/steep areas during any platform/road cut/fill earthworks and sound

compaction measures should be implemented;

- Stormwater management and erosion controls: to manage slope maintenance

and prevent any slope damage associated with erosion/slumping of the prevailing

erodible sandy to silty soils due to uncontrolled surface runoff;

- Suitable foundation solutions: to structural engineer’s details and in

accordance with geotechnical design recommendations, to address the variation

in the subsoil-founding materials and settlement design tolerances of new building

structures;



- Possible subsoil drainage: in the designated non-wetland seepage (“S”) area

as confirmed on site during construction.

Section B2.4 Founding

A detailed subsurface geotechnical site investigation to facilitate infrastructural and

house foundation design processes has not been included in the Preliminary

Geotechnical Conditions Report dated October 2005. Guidelines are however, given

on appropriate founding solutions which will require further investigation and

engineers design.

Section B2.5 Groundwater Conditions

The majority of the site area appears to be satisfactorily drained.

Although, along the central valley bottom terrain where relatively low impermeable

clayey and organic rich soils are anticipated, poor drainage characteristics and the

risk of near surface saturation problems due to the low permeability of the clayey

subsoils are typical. Weakly to poor drained slope conditions are therefore anticipated

in the general area of the valley bottom terrain. Where seepage is anticipated the

approximate footprint is designated with an “S” on the attached preliminary

geotechnical site zonation plan Figure G (enclosed as Annexure F3.1 of this report).

It is recommended that subsoil drainage measures be provided where all services or

roads cross these areas. The design of the subsoil drainage measures should be

concluded on-site during construction and in consultation with a geotechnical

professional.

Section B2.6 Excavatability / Trenchability

DCP (Dynamic Cone Pentrometer) tests have been conducted in four places across

the site. The two north-western tests refused at depths of 1,6m and 1,0m whereas

the two south-eastern tests refused at depths of 0,9m each.

Section B2.7 Subsoil Drainage

The preliminary geotechnical report further suggests that the planning and

development controls on site would pertain to carrying out:



- Possible subsoil drainage: in the designated non-wetland seepage (“S”) area

as confirmed on site during construction and as shown on the geotechnical site

zonation plan in the preliminary geotechnical report attached in Annexure F3 of

this report.

Section B2.8 Stormwater Management

It is important to dispose of stormwater effectively as uncontrolled runoff can cause

damage to the site through erosion. In severe instances, this may destabilise

embankments arising from a proposed development.

The objectives of the stormwater management system should be as follows:

- To adequately dispose of runoff from developed areas without causing soil

saturation or erosion/sloughing. The importance of this is greater on slopes

showing grades exceeding 20%;

- If required, to provide overland flow routes from access roads/driveways through

developments to cater for major storms and thereby minimising any risk of

damage to property;

- Stormwater systems should be designed to function adequately with low

maintenance in the long term and should cater for silting;

- After construction, the final ground levels around the perimeter of units should be

evenly sloped away from building structures, to ensure effective runoff of surface

water and prevent concentrations of stormwater on surface next to any structures.

Section B2.9 Pavement Subgrade Characteristics

Although laboratory analysis of road subgrade materials did not form part of the brief

of the preliminary geotechnical investigations, the road subgrade materials have been

visually appraised below on the basis of experience from testing carried out on similar

subgrade.

Moderate road subgrade materials are anticipated to occur if sandy deposits of the

Berea Formation are encountered at or immediately below road formation level.



Unsuitable road subgrade characteristics are inferred for areas underlain by the

colluvial and residual clays/clayey soils of the Vryheid Formation, where the

requirement for a select layer is anticipated.

Allowance for subsoil drainage should be made in the seepage area “S”.

Section B2.10 Conclusions

From the basis of the hydromorphic wetland mapping and a preliminary geotechnical

assessment, the following are the developmental considerations and key findings:

● Stable and satisfactory for development, which considered feasible subject to the

adoption of suitable development controls to engineer’s details;

● Development along any slopes steeper than 1 vertical: 3 horizontal (> 18°) and any

1:100 year floodline is not recommended;

● Hydromorphic wetland areas have been mapped along the south-eastern valley of

the site. A provisionally 20 metre wide environmental setback indicated around

the “temporary” wetland area should be verified by the Department of Agriculture

and Environmental Affairs in consultation with Ezemvelo KZN Wildlife;

● Soakpits should not be employed for the disposal of either stormwater or sewage;

● A mini sewage package plant or communal conservancy tanks should be planned;

● Guidelines are given on appropriate founding solutions which will require further

investigation and engineers design;

● Effective stormwater management will minimise maintenance of the slopes.

It is considered that the design of the civil engineering infrastructure and foundations

should be based on a detailed geotechnical subsurface site investigation.

Section B3 Environmental and Cultural/Historical Issues

Section B3.1 Environmental

An Environmental Scoping Report was prepared by Sustainable Development

Projects CC in January 2006.

Some of the conclusions and recommendations of this report are summarised as

follows:

It is apparent tht the development, in its present proposed format, will have positive

local repercussions from a biological perspective in terms of the removal and

replacement of surgarcane both with macadamia plantation and the establishment of



open space/conservation ares, as well as the establishment of a residential housing

component.

The site has been severely impacted upon by agricultural activities over an extended

period of time resulting in loss of biological diversity.

The proposed development could play a significant role in establishing a precedent

for the proposed open space system and conservation corridors in the Compensation

sub-region.

Social impacts will be positive during the construction phase in respect of job creation

and lcoalised investment in the short term, with improved service provision in the form

of roads and infrastructural service provision.

Long term services provision in the form of water and sewerage provision are not

adequately catered for in the region. Insufficient information is available to predict

with any degree of accuracy the nature of the impacts associated with the proposed

long term provision of water and there is a need for some further hydrological

consideration in this respect.

Local economic development opportunities would be improved in the short to medium

term with improved job creation and infrastructural development. The diversification

of crop lands will have improved local and regional economic impacts with job creation

for the medium to long term also being identified.

Section B3.2 Cultural / Historical

A preliminary archaeological assessment was undertaken by eThembeni Cultural

Heritage in September 2005 to report on the proposed development site. Two

heritage resources of significance were identified. The first of which (Site A, being a

Late Iron Age hilltop settlement) would require further assessment to determine its

significane. The second (Site B) being an ancestral grave, would require protection

from disturbance of any sort or a permit from Amafa. It must however, be noted that

the eThembeni Report to Amafa aKwaZulu Natali indicates that further survey is

required once the cane has been harvested.

In their correspondence dated 5 October 2005, Amafa indicated that of the two

heritage resources identified by eThembeni, “Site A” should be assessed to identify

its significance, and “Site B”, being an ancestral grave, should not be altered,

destructed or removed without a permit. Further survey of the areas under cane is to



be conducted once the cane has been harvested, any artifacts found are to be

sampled subject to permits being issued.

Helmsley Country Estate - Residential Development Internal Engineering Services: Preliminary Design Report Part C: Layout and Planning

F:\Bigen-Data\Admin\0938\PED Report Part C.docx C - 1





Part C Layout and Planning

Section C1 DEVELOPMENT PROFILE AND PLANNING ISSUES

Section C1.1 Development Boundary

The proposed development area is located very close to the N2 (Level 1) multi-

sectoral activity corridor and the Ballito (level 3) development node, which has

experienced an extremely high growth rate during recent years, and the demand for

affordable, gap, luxury and leisure residential property remains high. However, the

recent series of interest rate hikes has appeared to ease the market activity slightly.

The proposed 20,0801ha Helmsley Residential Country Estate development is

planned for approximately 93 (sectional title) medium density and 32 (stand alone)

special residential housing units respectively for the luxury and leisure/retirement

industry that will form part of a larger proposed 170ha macadamia nut plantation/farm

estate that is already in the process of being established over a 5 – 10 year production

time frame/period.

Section C1.2 Planning Approval

At the beginning of 2007 - the Helmsley Development Company decided to develop

a portion of the land, following on from the successful outcome and support received

from the Ordinance’s Needs and Desirability Planning Application submitted to the

various planning approval authorities during the beginning of 2006 and the latter part

of 2005. The Developer has subsequently obtained planning approval over No. ….

From the Development Facilitation Tribunal (DFA) in order to establish a township for

the proposed development. After obtaining the abovementioned planning consent in

………………….. 20…, the Developer decided to make use of the newly promulgated

(SPLUMA) in order to apply for the SDP approval(s) on the 5 medium density PUD

residential stands (site no. 1, .., .., ..., and .. on the approved SG Plan No. 991/2011).

Bigen Africa Services (Pty) Ltd have been appointed by the Developer to investigate,

analyse and report on the availability, as well as design and monitor the construction



of the required bulk, link & internal civil and electrical services for the proposed

development in terms of the approved layout plan. This is a statutory requirement in

terms of the DFA and SPLUMA Acts and other developmental legislation.

Section C1.3 Spatial Impact

The KwaDukuza Local Municipality is the local authority that is responsible for the

PDA and SPLUMA planning approvals of all township establishment applications in

respect of new residential housing estate development projects within their area of

jurisdiction.

From our investigations, it has been concluded that the majority of households within

Ward 4 (59.98%) in relation to the rest of KwaDukuza Local Municipality (50.76%) are

residing in brick houses built on separate stands.

The proposed Helmsley Housing development will entail 32 high cost residential

houses on free hold stands, as well as 5 sectional title stands with approximately 93

residential units of similar class with and equal or slightly lower affordability range. It

is anticipated that the proposed development will be of such a standard that it will

improve the value of the surrounding properties and provide a unique country life style

type of living opportunity.

Section C1.4 Topography

The site generally slopes from the north-west towards the south-east. Drainage from

the elevated hillock on which the development has been located is governed by three

(3) non-perennial streams within the valley lines that drain towards the south eastern

corner of the farm where they converge into a single stream/tributary that eventually

joins up and flows into the Wewe river approximately 3km south of the project area.

A characteristic of the township layout is the elevated views over the Compensation

flats, and the feeling of ample wide open space that has been created by locating the

majority of the residential erven along the ridgeline of the farms isolated hillock.

Section C1.5 Existing Land Uses

Cognisance of neighbouring land-uses, zoning, social and infrastructure requirements

were taken into account during the various layout planning processes for the Helmsley

Residential Development.

Section C1.6 Provincial Roads



There are no provincial roads that have been proclaimed through the project area,

however, existing access to the site is already established and obtained from District

Road D176.

Section C1.7 Geological Stability

Geological stability of the site directs land development options as well as housing

typologies and densities. Refer to ‘A Hydromorphic Delineation of Wetland areas and

a Preliminary Assessment of anticipated Geotechnical Conditions’ – dated October

2005, Ref. No. GS 59/05 (GGS).

Section C1.8 Land Use Requirements

The Helmsley Country Estate Development (with a total area of 21,0801ha) will be

developed to have land uses such as:

Those recorded on the land use plan for the approved development site is included

in Annexure F5.

Section C2 BULK AND LINK SERVICES

Section C2.1 Institutional Arrangements

Prior to the finalisation of Powers and Function on 3 January 2003 by way of a

Proclamation in the Government Gazette No. 24228 (Government Notice No. 52),

with effective date being 1 July 2003, wherein the Water Services Authorities were

promulgated in terms of the Water Act, the Department of Water Affairs and Forestry

(DWAF), now the Department of Water and Sanitation (DWS), were the Water

Services Sector leader and Principle Funder of all public water infrastructure with

selective CMIP (now MIG) funding assistance on a project by project basis, whereas

the iLembe District Municipality, in association with DWAF, took up the role as the

Implementing Agent.

With the advent of the new legislation already alluded to above, the iLembe District

Municipality (iLembe DM) have, as from 1 July 2003, taken over this role and are the

Water Services Authority (inclusive of the Water Service Provider (WSP) functions)

for the development area which falls outside of the Sembcorp/Siza Water concession

supply area.

Further, as from 1 March 2004, all previously DWAF owned assets (water services

infrastructure assets as well as staff) were transferred to iLembe DM in terms of the



Joint Policy Position Agreement on the transfer of water services, dated January

2003.

As per the services agreement entered into between the developer and iLembe DM,

the WSP provider function for this development will be the Developer’s responsibility,

and bulk water supply and sewage treatment operations will be fulfilled by the

developer, until such time as a Home-Owners Association (HOA) has been

established and WSP function transferred to the HOA. More detail on the WSP

function for the Bulk Water and Sanitation is discussed under section C2.3.6 of this

PED report.

Section C2.2 Bulk Water

Section C2.1.1 Existing Bulk Water Infrastructure

The iLembe DM does not have any existing bulk water supply pipelines or other

related water treatment infrastructure available in close proximity to the development

area at this stage. iLembe DM is however planning a bulk water off-take (Off-take

No. 13) from the newly constructed 900Ø mm bulk gravity water main from Mandini

to Mvoti, that was completed in 2015 as part of the Lower Thukela Bulk Water Supply

Scheme implemented by Umgeni Water.

A high level conceptual layout of the bulk supply lines located in close proximity to the

Helmsley Development is reflected on a layout drawing obtained from Black Balance

and is included in Annexure H1. The said plan reflects a proposed 700Ø mm bulk

water supply pipeline on the North Eastern boundary of the development site, from

which a future connection along the Northern boundary of the development site could

be obtained in the long term. The iLembe DM has confirmed that they have not set

aside any funding for this bulk water supply infrastructure and its implementation is

not foreseen in the near term future.

Section 11(3) of the Water Services Act states that in ensuring access to water

services; a Water Services Authority must take into account, amongst other factors:

Alternate ways of providing access to water services:- Unfortunately, no bulk water

supply service, other than ground water is currently available within the

surrounding project area;

The need for regional efficiency:- A regional water supply scheme from the iLembe

District is not available;

The availability of resources from neighbouring water services authorities:- No

other Bulk services other than ground water is currently available from the

surrounding area.



We have assumed that both Sembcorp/Siza Water and Ilembe have adopted the

iLembe District Municipality’s general requirements relating to water supply as a

common standard throughout their respective supply areas of jurisdiction. These

general requirements can be summarized as follows:

Water services in general shall be described according to “Guidelines for Human

Settlement Planning and Design”. Consideration should be given to:

o Flow characteristics

o Catchment specific water quality objectives

o Final Effluent, Storage for reuse or irrigation

Therefore, with the absence of a bulk municipal water supply scheme in the area, as

noted above, the proposed development will have to make use of sustainable

groundwater resources that will have to be established from 2 x DWS registered and

licensed boreholes located somewhere within the said property and developed in

terms of the following specialist reports;

Geophysical Investigation and Borehole Siting Report, as compiled by Messrs.

Geomeasure Group (refer to Annexure H2 for a copy of same).

Final Geohydrological Report on the Drilling, Pump Testing Water Quality Analysis

and Preliminary Reserve Determination for the proposed Helmsley Housing

Development, as compiled by Messrs. Geomeasure Group (also refer to

Annexure H2 for a copy of same).

Section C2.2.2 Proposed Bulk Water Supply System

With reference to the Water and Sanitation Flow Diagram and Infrastructure Layout

Drawing included in Annexure H3, the bulk water supply infrastructure can be

described as follow:

2 x small borehole pump stations (BH1 & BH2), pumping water through a dedicated

uPVC rising main to a package WTW and Reservoir located at highest point on the

site (184Amsl above mean sea level)

260kℓ/day WTW (refer to demand calculation below) & pump transfer to ground

level reservoir (at top water level (TWL) 190Amsl)

Booster pump or high level reservoir (Water Tower) that will feed to high level

supply zone > 180Amsl

Bulk water distribution pipelines to the high and low level supply zones

respectively, discussed under the internal services below.

Section C2.2.3 Water Demands

The expected water demand for the development of a proposed new residential

housing estate as indicated on the final/approved layout plan is estimated as follows:



Table 1: Expected AADD Water Demands (and Associated Sewage Runoff)

Land Use Water Demand Sewage Runoff

Phasing/ Zoning No. of

Stands/

Residential

Units

Unit Flow

(ℓ/day)

Total

Ave.

Flow

(kℓ/d)

SPD

(kℓ/d)

IPD

(kℓ/d)

% Run-

off

Unit

Run-

off

ADWF AWWF

(kℓ/d)

Peak

Run-off

(kℓ/d)

Special Residential 32 1500 48 72 384 80% 1200 38 46 96

Sectional Title 93 1200 112 167 893 80% 960 89 107 223

Conservation Reserve 5 15kℓ/ha 14 20 108 n/a

Total 173 260 1385 1731 128 153 319

Household water demand:

Special Residential – 1500ℓ/day (annual average daily water demand)

Sectional title – 1200ℓ/day (annual average daily water demand)

Conservation Reserve – 15kℓ/ha (annual average daily water demand)

Annual average daily:

demand (AADD) – 173kℓ/day

Summer Peak – 1 385kℓ/d (Factor 1,5)*

Instantaneous peak flow – 692kℓ/d (PF = 4.0)

Daily Peak – 4.8ℓ/s (Factor 2,4)*

Bulk Reservoir Storage – 48 hours*

Fire Flow – 1900ℓ/min/2hours 228kℓ * (SABS 10090:2003)

– 575kℓ storage tank (reservoir)

Elevated Storage – 115kℓ storage tank *(2 hours inst peak)

Treatment plant Capacity – 260kℓ/day

* As prescribed by the Guidelines for Human Settlement Planning and Design.

Section C2.2.4 General Description of Groundwater Source and Treatment Requirements

In terms of item C2.1.1 above, the proposed development will initially make use of

boreholes - a groundwater supply that shall be established by pumping water to the

highest point of the development along the north-eastern boundary of same from two

(2) newly sited boreholes that have already been drilled, pump tested and chemically

analysed (refer to layout drawing in Annexure H3). From the provisional chemical

analysis conducted on the water samples taken, the water will need some basic

treatment, disinfection and filtration before it is used for potable domestic water supply

purposes.

There are many different ways that can be employed for treating the borehole water,

(generally referred to as the treatment process). Based on the initial test results that

were obtained as referred to above – where the water has slightly elevated

manganese levels and package plants are often used in order to address same where



these specific types of problems exist. In this specific instance, we have opted to use

a conventional standard type of package plant in order to treat the water. Based on

the treatment guide from DWS for domestic water supply, the Construction of a new

water treatment package plant could be considered and is generally modular in

nature. The main advantages of a package plant is that it can be erected in a relatively

short period of time and is a compact self-contained unit capable of producing water

from a variety of raw water supply sources. The Capital costs are generally much

lower than that of a conventional permanent type of treatment plant.

a) Quantum and Quality

The groundwater development program resulted in the siting, drilling and testing

of 2 No. exploration boreholes both of which were successful.

The results of the pump tests undertaken on the new boreholes indicate that the

two boreholes have a combined sustainable yield of 444m³/day, which is well in

excess of the estimated water demand of 196.68 m³/day including 10% loses

for the proposed development.

Under the DWS General Authorisation groundwater use for the property

(Portion 161 of the Farm Compensation No. 868) is limited to 77.67m³/day.

Therefore, the use of ground water above this GA threshold amount for the

proposed Helmsley Residential Housing Development will require specific

registration and licensing with DWS.

The results of the Preliminary Desktop Groundwater Reserve Determination

that was undertaken utilising the GRDM software and available data indicates

that 8.75 Mm³/annum of groundwater is still available for allocation in the

Quaternary Catchment U30D.

While the results of a more detailed site specific preliminary Reserve

determination that was undertaken for Portion 161 of the Farm Compensation

No. 868 and surrounding properties indicated that even for this reduced area, a

total of 0.35 m³/annum of groundwater or 951m³/day is available to be allocated

to ground water users.

The water quality results from the 2 x new boreholes show that the water is

suitable for long term potable water supply after only being subjected to very

only basic water treatment, i.e. disinfection/chlorination followed by filtration in

order to treat the slightly elevated total coliform and turbidity levels.

b) Recommendations:

In light of the favourable results of both of the preliminary reserve

determinations, it is recommended that an application for the registration of the

2 x new boreholes and licensing of the proposed groundwater use is submitted

to DWS for approval.



Once a groundwater license has been obtained from DWS, it is recommended

that both of the boreholes be equipped as per the recommendations contained

in the Geomeasure management sheets.

The area around the boreholes should be graded so as to allow surface

stormwater runoff to drain away freely in order to prevent ponding which could

lead to contamination of the boreholes.

o The boreholes should be covered / protected by borehole-pump houses in

order to prevent tampering with the pumps and possible contamination of the

boreholes, the pump houses should also allow for essential electrical

equipment in order to monitor and control the pumps.

Water treatment as per the recommendation contained in this report should be

implemented in order to ensure that the water is suitable for long term potable

water supply.

Water samples should be collected from the post treatment water supply to the

development on a quarterly basis and submitted to a SANAS accredited

laboratory for Abr. SANS 241:2006 analysis in order to ensure the water is fit

for human consumption.

Static and dynamic water levels should be recorded on a regular basis in order

to ensure that de-watering of the aquifer is not occurring as the water utilisation

increases and that the boreholes are not interfering with each other.

c) Caution:

Any septic tanks, soak-always or water treatment works that may be

constructed as part of the proposed development should be sited away from the

existing boreholes in order to prevent contamination of the developments

primary water supply.

The results of the previous pump tests only represent a “snap shot in time”

and therefore the long term sustainable yield of the boreholes can only be

accurately determined if an accurate record of the static and dynamic water

levels and pumping volumes are kept and analysed on a regular basis by a

hydrogeologist.

The preliminary reserve determinations included in this report are only included

as a guideline and the findings will have to be verified by the DWS RDB office.

Section C2.2.5 Bulk Water Supply System Components

Refer to overall system description in Section C2.1.2

Section C2.2.5.1 Bulk Water Source – Boreholes

Borehole no. BH1 (KZN 070181)



- Pump Installation (mbgl) : 60m

- Dynamic Water level (m) : 12m

- Rec. Pumping Cycle (Hrs/day) : 8

- Rec. Pumping rate on pump cycle : 18m3/hr 5,00ℓ/s 144m3/day

- Analytical Water Quality Analysis

▪ General Determinants

Mostly Class I

Exemptions: Turbidity – Class III *

▪ Macro Determinants

Mostly Class I

Exemptions: Iron – Class II ▪

▪ Micro Determinants

Manganese – Class II ▪

▪ Microbiological Determinants

Mostly Class I

Total Coliforms: Class III

Borehole no. BH2 (KZN 070182)

- Pump Installation (mbgl) : 50m

- Dynamic Water level (m) : 20m

- Rec. Pumping Cycle (Hrs/day) : 12

- Rec. Pumping rate on pump cycle : 25m3/hr; 6,94ℓ/s; 300m3/day

- Analytical Water Quality Analysis

▪ General Determinants

Mostly Class I

Exemptions: Turbidity – Class III *

▪ Macro Determinants

Mostly Class I

Exemptions: Iron – Class II ▪

▪ Micro Determinants

Manganese – Class II ▪

▪ Microbiological Determinants

Mostly Class I

Total Coliforms: Class III

* The turbidity of the water quality will probably improve over time seeing as though

these are newly drilled/developed boreholes.

▪ Class II: maximum allowable for limited duration use (7 years)

Class III: exceeds maximum allowable limits



The two x boreholes shall be equipped with suitable positive displacement or

submersible pumps and the controls for same will be housed in an enclosed masonry

pump house.

The equipment for the boreholes shall be designed in order to meet the

geohydrologist’s management recommendations:

BH 1 – KZN 070181 can provide a safe yield of 5.0ℓ/s with max 8 hour pump cycle.

BH 2 – KZN 070182 can provide a safe yield of 6.94ℓ/s with max 12 hour pump

cycle.

Table 2: Borehole Pump Design Detail

Pipe Section: Pump 1 Pump 2

Q (ℓ/s) = 5.000 6.940

D (m) = 0.075 0.090

L (m) = 1132.0 420.0

S (m/m) = 0.02 0.01

v (m/s) = 1.13 1.09

FSL level - Entering WTW 184 184

Suct Side Min water level 20 83

h stat 164 101

hf tot 21.94 6.08

Δ h - Total Head (m) 185.94 107.08

Power kW 14.29 11.42

Borehole Equipment includes:

Borehole Pump House installation

o Both boreholes to be housed inside a separate brick pumphouse (Refer to

Annexure H4 for Pump house and pump station pipe configuration.

Casing and Rising Mains

o Casings are 140mm Ø uPVC Sleeves (The diameter and condition of the

casings would have to be reviewed as the small diameter limits the suitable

pump options)

o The pipework below ground level to be 110mm Ø Galvanised Mild Steel (GMS)

pipes in order to be able to handle a max pressure of up 18.5 Bar.



o Each pump to be equipped with non-return valve in order to prevent short

circulating back into the ground, from one borehole to the other.

Section C2.2.5.2 Rising Main Pipelines

The rising main shall be constructed using uPVC piping:

Rising main section 1 = 915m, 75mm Ø Class 10 uPVC pipes



Section C2.2.5.3 Potable Water Treatment – Water Treatment Works (Refer to Annexure H5 for

Layout Plan)

Raw Water Quality

Only a single raw water quality analysis was carried out on the two boreholes

(KZN070181 and KZN070182) during 2007, which only provides a snapshot of the

raw water quality in 2007. It is, however, advised as part of the detail design phase

to carry out a more detailed water quality sampling exercise in order to provide a

clear overall picture of the current raw water quality for these boreholes.

The average values for various parameters tested during 2007 have been listed in

Table 4 below.

Table 3: Raw water quality data

Water characteristic Unit Average raw water value

SANS 241-2015 Drinking water limits

Water pH pH 7.5 ≥5 - ≤9.7 Operational

Total alkalinity mg/l as CaCO3 175 n/a

Water turbidity NTU 5.9 ≤5 Aesthetic ≤1 Operational

Conductivity mS/m 58.8 ≤170 Aesthetic

Colour mg/l as Pt 1.5 ≤15 Aesthetic

Total dissolved solids mg/l 411.6 ≤1200 Aesthetic

Iron μg/l as Fe 360 ≤300 Aesthetic ≤2000 Chronic Health

Manganese μg/l as Mn 185 ≤100 Aesthetic ≤400 Chronic Health

E.coli Count per 100ml 0.0 Not Detected

Total coliform bacteria

Count per 100ml >2419 ≤10 Operational

Faecal coliforms Count per 100ml 0 Not Detected

Calcium mg/l as Ca 37.1 N/A

Magnesium mg/l as Ca 23.1 N/A

Sodium as Na mg/l as Na 75.7 ≤200 Aesthetic

Chloride mg/l as Cl 76.7 ≤300 Aesthetic

Sulphate mg/l as SO4 14.71 ≤500 Acute Health ≤250 Aesthetic

Total Organic Carbon mg/l as C 0.147 ≤10



Water characteristic Unit Average raw water value

SANS 241-2015 Drinking water limits

Fluoride mg/l as F 0.36 ≤1.5 Chronic Health

Nitrate nitrogen mg/l as N 2419 cfu/100ml

respectively, which indicates potential groundwater contamination through the

ingress of sewage or effluent. In the event that similar results are found during the

detail design stage the source of the contamination should be investigated rather

than treating the end result of the contamination, ultimately leading to higher

treatment costs.

The raw water turbidity of both boreholes are below 10 NTU.

The level of iron (Fe = 0.46mg/ℓ) and manganese (Mn0.19 mg/ℓ) are above the

prescribed limits required by the SANS 241:2015.

Treatment Objectives

The target water quality standards shall be in accordance with SANS 241:2015.

The water quality objectives, potential unit treatment process and process

function, as well as the treatment targets are illustrated in Table 4 below.

Table 4: Summary of treatment process

Water Quality Objective

Unit Treatment Process

Process Function Target

Removal of suspended material (reduce turbidity)

1) Sedimentation

2) Rapid sand filtration

1) Removal of settling suspended matter

2) Removal of fine suspended matter

1.0 NTU

Oxidation of iron and manganese

1) Pre-chlorination 1) Oxidation of iron and manganese

0,1 mg/l Mn

0,3 mg/l Fe

Ensure distribution system residual disinfectant

1) Post-Chlorination 1) Establish a chlorine residual

DOC removal 1) Sedimentation

2) Rapid gravity sand filtration

Reduce DOC by coagulating dissolved organics remove with phase separating steps

DOC < 1

Proposed Unit Treatment Processes

It is foreseen that a conventional water treatment process will be required. The

main treatment process/aspects are briefly discussed below:

A pre-oxidation step will be required in order to oxidize the iron and

manganese to the acceptable target levels.

With the raw water turbidity of less than 10 NTU it is foreseen that direct

filtration will be sufficient for phase separation.



Conventional stabilization and disinfection strategies are expected to be

sufficient to ensure a good quality of treated water.

It is expected that the raw water will be of such a quality that stabilization will

not be required for most of the time. However, provision will be made for the

addition of soda Ash to increase the pH to acceptable levels during coagulation.

During the preliminary engineering design phase of the Helmsley WTW, provision

has been made to dose a polymeric, as well as a metal coagulant.

The proposed process train is schematically reflected in Annexure H6 and will

comprise of the following:

pre-oxidation (using chlorine);

pH correction (using lime);

coagulation;

flocculation;

clarification (sedimentation);

Pressure filtration; and

Disinfection.

Raw Water Supply

Raw water shall be transferred from the boreholes to the WTW up to a maximum

flow rate of 12ℓ/s over a 12 hour period. This will require the inclusion of a flow

balancing tank in order to provide a constant throughput of 3ℓ/s (260m³/day) over

a 24 hour period.

Pre-oxidation

Pre-oxidation processes are required for the oxidation of heavy metals such as iron

and manganese. Chlorine is a strong oxidant and is often used for the oxidation of

inorganic compounds such as iron and manganese. In such cases a phase

separation process is required downstream of the pre-chlorination step in order to

remove the metal precipitate.

Provision shall be made to pre-chlorinate the raw water in extreme cases when

severe problems are experienced with the iron and manganese complexes. Pre-

oxidation shall be provided by means of a chlorine dosing process into the raw

water feed pipeline (i.e. one dosing point) between the collection tank and raw

water feeder pumps.



pH Adjustment

Numerous chemicals are currently available to increase the pH and alkalinity of

water (i.e. calcium hydroxide, sodium carbonate and sodium hydroxide) to pre-treat

the raw water for coagulation dosing (i.e. increase the alkalinity).

Soda Ash shall be dosed immediately downstream of the flow balancing tank.

Sufficient mixing energy will be provided for the soda ash through an inline static

mixer. This will stabilize the pH prior to coagulation.

Coagulation

Allowance shall be made to dose a coagulant into each 5.5m3/hour streams

respectively downstream of the raw water feed pumps. Hydraulic flash-mixing will

be created by means of an inline static mixer in order to produce a head loss of at

least 1.0m downstream the dosing point.

Sufficient flash-mixing inducing a G-value > 2000 sec-1 is of prime importance in

order to optimize the efficiency of coagulants. The polymer dosing system is sized

to dose a maximum of 10mg/ℓ and the ferric-chloride dosing system shall be sized

to dose a maximum of 20mg/ℓ.

a) Poly-electrolyte

Two single phase dosing pumps shall be provided (one as stand-by) in order to

feed diluted poly-electrolyte from the day tanks to the dosing point downstream

of the balancing tank.

The dosing pumps shall each be required to deliver between 0 and 1ℓ /hour at

a pumping head of 10m by means of flow paced electronic variable speed

controls. Dosing pumps shall also be stroke adjustable between 10 and 100%

of the maximum stroke

One bulk storage tank of 100ℓ shall be adequate to provide more than 30 days’

storage for 260m3/d at the average coagulant dosage concentration.

One calibrated 20ℓ day tank shall be provided from which the coagulant dosage

can be controlled on a shift basis. The coagulant gravitates from the bulk tanks

into the day tanks where after it shall be pumped to the dosing point.

Each day tank shall be equipped with a mechanical mixer with stainless steel

shaft and impeller, and shall be capable of maintaining a homogeneous mixture

of chemicals and water. These mixer motors shall be manually controlled from

the local motor control centre in the chemical building.



b) Ferric-Chloride

Two single phase dosing pumps shall be provided (one as stand-by) in order to

feed diluted poly-electrolyte from the day tanks to the dosing point downstream

of the balancing tank.

The dosing pumps shall each be required to deliver between 0 and 2ℓ /hour at

a pumping head of 10m by means of flow paced electronic variable speed

controls. Dosing pumps shall also be stroke adjustable between 10 and 100%

of the maximum stroke.

One bulk storage tank of 250ℓ shall be adequate to provide more than 30 days

storage for 260m3/d at the average coagulant dosage concentration.

One calibrated 50ℓ day tank shall be provided from which the coagulant dosage

can be controlled on a shift basis. The coagulant gravitates from the bulk tanks

into the day tanks where after it shall be pumped to the dosing point.

Each day tank shall be equipped with a mechanical mixer with stainless steel

shaft and impeller, and shall be capable of maintaining a homogeneous mixture

of chemicals and water. These mixer motors shall be manually controlled from

the local motor control centre in the chemical building.

Flocculation/clarification

Flocculation follows coagulation to promote optimum conditions for floc formation.

The success of the flocculation process is primarily depended on three factors

namely: effectively mixing the coagulant into the water; the time available for floc

formation; and turbulence intensity promoting floc growth.

The flocculated water shall be transferred to the pressure filters through a 160mm

diameter uPVC pipe with a velocity at maximum throughput of 0.3m/s in order to

allow floc formation.

a) Filtration System

Pressure filters shall be used for the filtration from the groundwater or high

quality surface water that does not require clarification. In certain groundwater

systems they can also be used for the removal of iron and manganese in

addition to turbidity.

The coagulated water shall be transferred to three filters filled with silica quartz

media operating under pressure.



b) Filter Feeder Pumps

The feed water shall be extracted from the flow balancing tank and fed into the

pressure filters at a flow rate of between 10 and 15m3/hour at a maximum duty

head of 20m through two filter feeder pumps fitted with VSD’s (1 duty + 1 stand-

by installation).

The hydraulics for the proposed filter feed system are listed below:

Minimum velocity in 75mm diameter uPVC suction and delivery line:

0.720m/s

Maximum velocity in 75mm diameter uPVC suction and delivery line:

0.924m/s

c) Pressure Filters

The pressure filters shall be fed at a loading rate of 15m3/hour through the

feeder pumps. The filtration rate ranges between 5m/hour and 10m/hour, 6

m/hour is required for the filters. Should one filter be out of operation or being

backwashed, the filtration rate shall automatically increase to 9.5m/hour, which

is deemed the upper limit for safe operation.

The backwash water from the filters shall be wasted to the waste chamber that

will be constructed outside the container as shown in Figure 8. The solids in

the wasted backwash water shall settle out while the excess water will be

allowed to drain into the stormwater system through a proposed outlet pipe or

allowed to simply evaporate. This shall require the removal of sediment from

the chamber from time to time.

The backwash system shall consist of two backwash pumps (1 duty + 1 stand-

by installation) and 2 compressors (1 duty + 1 stand-by installation). The

backwash pumps must have a maximum duty of 25m3/hour at a head of 25m.

The hydraulics for the proposed filter feed system are listed below:

Maximum velocity in 75mm diameter uPVC suction and delivery line:

0.924m/s

Disinfection

Provision shall be made to feed chlorine gas for pre-chlorination into the raw water

delivery system, as well as for disinfection into the final treated water in the

clearwater tank. A full stand-by unit should be provided for either the pre- or the



post-chlorination. The pre and post chlorination units shall be automated

proportionally in order to accommodate the raw water flow rate.

Table 5: CT Values for Inactivation of Giardia Cysts

Disinfectant Inactivation (mg ∙ min/L)

0.5-log 1-log 1.5-log 2-log 2.5-log 3-log

Chlorine 1 17 35 52 69 87 104

Chloramine 2 310 615 930 1 230 1 540 1 850

Chlorine Dioxide 3 4 7.7 12 15 19 23

Ozone 3 0.23 0.48 0.72 0.95 1.2 1.43

CT values were obtained from AWWA, 1991 1. Values are based on a free chlorine residual less than or equal to 0.4mg/L, temperature of 10°C, and a

pH of 7

2. Values are based on a temperature of 10°C and a pH in the rant of 6 to 9

3. Values are based on a temperature of 10°C and a pH of 6 to 9

(Alternative Disinfectants and Oxidants Guidance Manual, EPA, April 1999)

Table 5 above indicates a CT value of 104mg.min/ℓ is required for a 3-log

inactivation of Giardia Cysts. Assuming a residual chlorine value of 2mg/ℓ, the

estimated contact time required is 52 min.

Table 6: CT Values for Inactivation of Bacteria and Viruses

Disinfectant

Inactivation (mg ∙ min/L)

Bacteria Viruses

2-log 4-log 2-log 4-log

Chlorine 0.1 – 0.2 10 - 12 2.5 – 3.5 6 - 7

Chlorine Dioxide

8 - 10 50 - 70 2 - 4 12 - 20

Ozone 3 - 4 N/A 0.3 – 0.5 0.6 – 1.0

Clearwater Storage

A Clearwater storage tank with a full supply capacity of 15m³ shall provide the

following:

balancing tank for clear water pumps;

chlorine contact tank with 83 minutes contact time for 260 m3/day; and

Adequate volume with a constant head to the filter washwater pumps.

The contact time in the clear water tank at a flow rate of 260m3/hour is sufficient.

Low Lift Pumps



Two low lift pumps (1 duty + 1 stand-by installation) shall be required to transfer

the potable water to the groundwater reservoir. These pumps shall be fitted with

variable speed drives (VSD’s) in order to operate during variable flow conditions.

The low lift pumps fitted with variable speed drives (VSD’s) shall have a capacity

of at least 5.5 to 11.0m3/hour at a duty head of at least 10m.

The hydraulics for the proposed raw water feeder system are listed below:

Minimum velocity in 63mm diameter uPVC suction and delivery line: 1.6m/s

Maximum velocity in 63mm diameter uPVC suction and delivery line: 1.120m/s.

The low lift pump house shall also serve as a chemical storage facility for basic

chemicals and operation items in order to conduct daily quality monitoring

(Refer to Annexure H7).

Electrical, Control and Instrumentation

MCC Panels for the boreholes, shall be mounted inside the pump house, and

will include timers, low and high level transmitters with flow switches, to

automatically stop and start the pump(s).

A HMI/SCADA system shall provide flow and pump details to the operating room

HELMSLEY COUNTRY ESTATE RESIDENTIAL DEVELOPMENT … · 2019. 1. 9. · Section C3.1 Sanitation...

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Transcript of HELMSLEY COUNTRY ESTATE RESIDENTIAL DEVELOPMENT … · 2019. 1. 9. · Section C3.1 Sanitation...