Red Gravel Pit Sandford 1511 P/Mepa.tas.gov.au/documents/jenkins_red_gravel_pit_document.pdf · rock. The dolerite has weathered by a natural process of moisture penetrating the joints

Red Gravel Pit – Sandford – 1511 P/M Change to Operation - Supporting Document

Prepared By: Barry Williams

Date: 6 May 2011

Issue Date Recipient Organisation

draft 2 May 2011 David Oldmeadow EPA

Final 6 May 2011 David Oldmeadow EPA

Red gravel pit – Sandford – Change to Operation Final

Integrated Land Management and Planning | Introduction 2

CONTENTS

1. Introduction .................................................................................................................................... 3

2. Background ..................................................................................................................................... 4

3. Development Proposal.................................................................................................................. 13

3.1. Regulatory Situation.......................................................................................................... 13

3.2. Operation Description ....................................................................................................... 13

3.2.1. Extraction ...................................................................................................................... 13

3.2.2. Processing ..................................................................................................................... 13

3.2.3. Marketing ...................................................................................................................... 14

3.3. Development Details ............................................................................................................. 14

3.3.1. Current Situation ........................................................................................................... 14

3.3.2. Proposed Operational Improvements .......................................................................... 14

3.3.3. Future Relocation of Infrastructure .............................................................................. 14

4. Possible Environmental Impacts ................................................................................................... 15

4.1. Noise ..................................................................................................................................... 15

4.2. Dust ....................................................................................................................................... 16

4.3. Process water ........................................................................................................................ 16

4.4. Flora and fauna ..................................................................................................................... 16

5. Management commitments ......................................................................................................... 17

6. Conclusion ..................................................................................................................................... 19

FIGURES

Figure 1: Current (2011 – 2014) Mining and Rehabilitation Plan ........................................................... 6

Figure 2: Mid-Term (2014 – 2022) Mining and Rehabilitation Plan ....................................................... 7

Figure 3: Final (2022 – 2025) Decommissioning and Rehabilitation Plan............................................... 8

Figure 4: Mining and Rehabilitation Plan - Cross Sections through Staged Works ................................ 9

Figure 5: Machinery Shed – Plan and Elevations .................................................................................. 10

Figure 6: Loaclity Plan – showing nearest residences ........................................................................... 11


Integrated Land Management and Planning | Introduction 3

1. INTRODUCTION

Project Title Red Gravel Pit at Sandford

Mining Lease Number 1511 P/M

Lease Holder T.H. Jenkins

Lease Operator T.H. Jenkins

Category 3 – Construction Minerals

Area 9 hectares

Client Details Jenkins Hire Pty Ltd ABN 30 050 205 671

Business Transport and Civil Earthmoving

Address P.O. Box 616

Glenorchy TAS 7010

Contact Tim Jenkins Mobile 0418 129 321

Quarry Manager Steve Morrisby Mobile 0408 326 497

Fax (03) 6273 0766

The Red Gravel Pit at Sandford has operated

for over twenty years providing high quality

“red driveway gravel” to the local community.

The mining lease for the quarry, 1511P/M,

covers an area of 9 hectares and the applicant

is both the lease holder and the operator.

The resource is highly weathered dolerite

rock. The dolerite has weathered by a natural

process of moisture penetrating the joints of

the bedrock liberating blocks. The blocks are

then gradually broken down by natural

chemical weathering. The process is called

‘spheroidal weathering’ and it creates course

gravels with high clay content and roughly

spheroid shaped cobbles and boulders.

The ratio of the over-sized (boulders)

component of the gravel varies throughout

the resource area. The oversized material

must be crushed to contribute to the finished

gravel product.

Hobart

Queenstown

Triabunna

Burnie

Launceston

100 0


Integrated Land Management and Planning | Background 4

2. BACKGROUND Table 1: Site Description

Site description

Climate data for nearest weather station – Hobart Airport 094008

Mean max. Temperature (0C) 20.6 Mean min. Temperature (0C) 10.7

Mean annual rainfall (mm) 498.9

Wind data At the nearest weather station 094008 Hobart Airport the predominant wind direction (> 40 %) and the strongest winds come from the northwest. Afternoon sea breezes tend to cause summer wind conditions to change to a strongest prevailing wind from the south east.

Land capability The land occupied by the quarry has been field checked and classified as class 4; land well suited to grazing but which is limited to occasional cropping or a very restricted range of crops.

Aspect The site is located on a west facing slope of a low hill that is the terminus of a northeast running low ridge off Mount Augustus. Although the mining lease covers the crest of the ridge, the quarry has been confined to the western slope so as to retain to natural skyline. The top of the quarry’s eastern face is at around RL 70m and the sediment trap at the north west corner is at around RL 40m.

Vegetation The quarry is surrounded by agricultural land mostly sown to pasture. Remnant woodland in the vicinity of the quarry is mapped as (DTO) Eucalyptus tenuiramis forest and woodland on sediments. A small clump of (DTD) Eucalyptus tenuiramis forest and woodland on dolerite located nearby represents the floristic structure that would have existed on the land prior to clearing.

Geophysical data The target resource in the quarry is a fairly course grained dolerite gravel derived from naturally occurring weathered dolerite rock. Dolerite bedrock is exposed on the eastern face of the quarry. Massive dolerite is outcropping in parts of the floor of the quarry in front of this face. The balance of the quarry is ripping successfully. The soil type is described as a Dermosol; ‘undefined brown soil developed on Jurassic dolerite bedrock and colluvium on rolling to steep land.

Fauna There is little evidence of native fauna on the site. Frogs may periodically inhabit the two sediment retention basins.


Integrated Land Management and Planning | Background 5

Plate 1 Panorama looking west from the top of the eastern face, land recently re-habilitated in the foreground.

Plate 2 Looking west along bench in the recently rehabilitated north face Plate 3 Looking north across recently worked out area in southeast corner

Red Gravel Pit – Sandford – Development Application

Figure 1: Current (2011 – 2014) Mining and Rehabilitation Plan

0 75 150

Sediment

retention

Current

extraction

3

north

2

1

Access road

Boundary of mining

lease 1511P/M

Rehabilitation area re-

contoured with topsoil

applied

Crusher

Sediment

retention

Product

stockpiles

Overburden



applied

Contour drain for irrigation dam

Topsoil

A

A

Machinery shed


Figure 2: Mid-Term (2014 – 2022) Mining and Rehabilitation Plan

0 75 150

Sediment

retention

Mid-term

extraction

north

Boundary of mining

lease 1511P/M

Rehabilitation area with

pasture applied

Sediment

retention


Topsoil



applied RL 45m

Rehabilitation area with

pasture applied

A

A

Machinery shed

Crusher

Rehabilitation area

re-contoured with

topsoil applied

Product

stockpiles Planting tree screen

Supplement existing

revegetation with infill

planting

Access road

Stockpiles to

screen crusher


Figure 3: Final (2022 – 2025) Decommissioning and Rehabilitation Plan

0 75 150

Sediment

retention

A

A

north

Access road

Boundary of mining

lease 1511P/M

Sediment

retention




applied RL 45m



applied RL 50m

Rehabilitation

area re-

contoured with

topsoil applied

RL 55m

All structures and

machinery removed

New planting at toe of

eastern face

Red Gravel Pit – Sandford - Decommissioning and Rehabilitation Plan

Figure 4: Mining and Rehabilitation Plan - Cross Sections through Staged Works

Extraction area

Product stockpiles

Section A-A

RL 60 m

RL 45 m

RL 65 m

Extraction area

Stockpiles located to screen crusher

Section A-A

RL 60 m

RL 45 m

RL 50 m

Oversized against face topsoil over

and planted with woodland species.

Section A-A

RL 55 m

RL 45 m

RL 50 m

Topsoil and pasture grass

Machinery shed

Current Mining Plan and Rehabilitation Works

Mid-Term Mining Plan and Rehabilitation Works

Decommissioning Plan and Rehabilitation Works

Relocated machinery shed

Figure 6: Locality Plan – Showing residences within 1 km of the quarry

north

0 650

Screened by hill side

Screened by hill side

Plate 4 View from new crusher site looking west towards Germain Court

Plate 5 View from 43 Rushton Close towards quarry Plate 6 View from outside 64 Germain Court with 69 Germain Court in forground

64 Germain Court 41 Rushton Close 45 Rushton Close

Existing product stockpile


Integrated Land Management and Planning | Development Proposal 13

3. DEVELOPMENT PROPOSAL

3.1. REGULATORY SITUATION

The quarry operates under existing use rights with regard to the Clarence City Council and the

Environment Protection Authority regulates the quarry through’ License to Operate Scheduled

Premises’ number 5932. This license specifies a maximum production limit of 20,000 cubic metres of

product per annum. The license also has a limit of 2,000 tonnes of material that can be processed

through a crusher.

A mining lease number 1511P/M covers the quarry site and the Department of Infrastructure Energy

and Resources also regulates the quarry operation through Mineral Resources Tasmania. The quarry

must be operated in accordance with the Mineral Resources Development Act 1995 and the Quarry

Code of Practice 1999.

3.2. OPERATION DESCRIPTION

3.2.1. EXTRACTION

The product is extracted by ripping with a dozer and pushing up into stockpiles. The extraction areas

are predominantly shallow (less than ten metres). Closer to the ridgeline hard bedrock has resisted

ripping and further extraction is impractical. The current extraction area is closer to the lower

extremity of the site and the working faces will be low to maintain drainage. The extraction areas are

‘set out’ in a series of three benches separated by approximately 5 metre high faces. Excavation

proceeds from a number of extraction points, each offering slightly different product properties. The

products are then blended to produce the final specification product.

In all the extraction areas the proportion of oversized boulders and cobbles encountered during

excavation varies according to the location in the pit and the depth of excavation. When oversized

product is encountered in the extraction area or is rejected by the screens, these materials are

stockpiled.

Normal operating hours for the quarry are as listed below:

Weekdays 7:30 am to 6:00 pm

Saturdays 8:00 am to 4:00 pm

Sundays and public holidays no work

3.2.2. PROCESSING

A wheel loader is then used to transport the product to screens where oversized materials are

removed. Products with varying properties can be blended through the screens to produce a

consistent blended product for sale.

Periodically it is necessary to crush the oversized material to provide hard angular aggregate to

blend with the softer natural gravel and clay to keep the final product within specification. When

placed and compacted the crushed rock gives the pavement strength and wear resisting properties

and the finer gravel and clay binds the pavement and provides a smooth and water resistant surface.


Integrated Land Management and Planning | Development Proposal 14

3.2.3. MARKETING

The final product is stockpiled in its blended form ready to be loaded out on single tray trucks or

truck and trailers. The “red driveway gravel” is an ideal product for domestic driveways in a rural

setting but is also used to construct high quality gravel roads, walking tracks and fire trails. The

quarry is situated within a fast expanding rural residential setting; the Operator is thus able to supply

quality products at competitive prices to the local area.

3.3. DEVELOPMENT DETAILS

3.3.1. CURRENT SITUATION

To adequately supply the existing and future markets with a consistent quality product the Quarry

Manager requires the capacity to crush oversized product at a rate consistent with product

specifications. Currently the product quality is compromised by the limit on crushing product to

2,000 tonnes per annum. The maximum production capacity of the quarry is 20,000 cubic metres of

processed product. At an average bulk density of 1.5 t/m3, the quarry can produce 30,000 tonnes

per annum. With the current limit on crushing of 2,000 tonnes the crushed rock can only comprise 7

percent by mass of the finished product.

Although adequate for the product derived from some of the extraction areas, in other areas the

lack of crushing capacity has lead to lower quality product specifications and growing stockpiles of

oversized product. The oversized stockpiles are occupying valuable hardstand and extraction space

and constraining the efficient layout of the quarry.

3.3.2. PROPOSED OPERATIONAL IMPROVEMENTS

This development proposal seeks to increase the annual limit on crushed product from 2,000 tonnes

to 7,500 tonnes. This operational improvement will result in the Quarry Manager having the capacity

to blend up to 25 percent by mass of the crushed rock into the gravel.

To effect the change the Quarry Manager will operate the quarry’s Terex Jaques 20 by 12 inch jaw

crusher. This crusher has a production rate of around 100 tonnes per 8 hour day. To achieve the new

production capacity the Quarry Manager will operate the crusher around 75 days per year between

the hours of 8:00 am and 4:00 pm on weekdays only. The reduced operating hours for the crushing

operation are being introduced by the operator to further reduce the risk of neighbours being

adversely affected by noise.

3.3.3. FUTURE RELOCATION OF INFRASTRUCTURE

It will be necessary in the future to relocate the existing machinery shed to a new site within the

quarry floor. The existing site for the machinery shed was established when the quarry was first

developed. The site is now visually exposed and since the resource has been recovered from around

it, the structures are elevated.

In the mid-term (2014 to 2022) of the quarry development the machinery shed and refuelling facility

will be relocated to a ‘worked-out’ section of the quarry floor adjacent to the eastern face. This site

will reduce the prominence of the building and expose additional resource. Extraction of this

resource will enable the mining plan to progress towards the final planned landform. The tank for

the refuelling facility will be located within an impermeable bund with a minimum capacity of 110


Integrated Land Management and Planning | Possible Environmental Impacts 15

percent of the tank’s capacity. Minimal quantities of oils and chemicals will be stored on site within

machinery shed building.

The new location of the building is shown in Figures 2 and 4 and details of the building are described

in Figure 5.

4. POSSIBLE ENVIRONMENTAL IMPACTS The Red Gravel quarry at Sandford is a level 2 activity under schedule 2 of the Environmental

Management and Pollution Control Act 1994. As such the environmental impact of the activity or any

“intensification” of the activity is assessed by the Board of the Environment Protection Authority.

4.1. NOISE

Noise is best attenuated by distance and topography. The closest neighbours to the quarry are

located on the opposite side of the ridgeline to the quarry. The intervening topography effectively

screens these properties from a view of the quarry and noise. There are neighbours on elevated land

to the west of the quarry that although 750 metres distant are more likely to be affected by

operating noise from the quarry. In Figure 6 a number of residences that are located within 1

kilometre of the quarry are identified. Others on Delphis Drive are very well screened by the ridge

line and are not considered. Excavation to date has caused the operation to be lowered and the line

of sight to the majority of residences is now interrupted by cut batters. Figure 6 shows sight lines

that indicate the range of visible exposure of the quarry.

Stockpiles will be located to provide an effective screen adjacent to the crusher to protect

neighbours in the westerly direction from noise generated by the crusher. The stockpiles will absorb

and deflect much of the noise generated by the crusher away from the residences. The crusher

should no longer be visible from these residences and when a massive structure hides equipment

generating noise much of the noise is intercepted as well.

Plate 4 is a view from the proposed new location for the crusher. Three residences are clearly visible

on the hill to the west. In this plate it can also be seen that an existing product stockpile some

distance away from the proposed crusher location completely interrupts the sight line. If this

stockpile extended more to the left of the frame the residences would not be visible. It is the

intention of the Quarry Manager to relocate the crusher to this site and construct a permanent

overburden stockpile that will completely conceal the crusher from view.

The proposed revised layout of the quarry can be seen in the mid-term mining plan and cross-

section. It can be also seen on this plan that it will be necessary in the future to relocate the

machinery shed and office. The timing of the relocation will depend on progress with the mining

plan and the need to access the resource under these facilities. The arrangement of the crusher and

stockpiles will remain until quarry decommissioning at which time the overburden stockpiles will be

used for land contouring and rehabilitation works.


Integrated Land Management and Planning | Possible Environmental Impacts 16

4.2. DUST

An operating crusher can add to the amount of dust generated by a quarry operation. Other sources

are drop points from conveyors, vehicle movements, loading and unloading trucks and stockpiles,

and exposed un-vegetated surfaces.

As a condition of the continuation of the mining lease the lease holder is required to ensure that no

visible dust crosses the mining lease boundary in any direction. The worst conditions for wind

carrying dust are likely to occur in the summer months when prevailing dry conditions conspire with

strong afternoon sea breezes to potentially cause dust to be carried across the boundary to

northwest.

The Quarry Manager will continually monitor dust conditions and will introduce remedial actions if a

risk of an emission is likely. Remedial action will include:

using water sprays to dampen dusty surfaces,

either covering or wetting the surface of loads leaving the quarry, and

using water sprays to settle dust generated by the crusher and at conveyor drop points.

Surfaces and stockpiles will be damped down when dry and windy conditions are expected over

weekends when the quarry is not operating.

4.3. PROCESS WATER

Operating the crusher for longer periods during the year should not increase the amount of process

water utilised on the site other than for dust suppression purposes. The maximum amount of water

used will be during the dryer months which will coincide with the minimum amount of rainfall

runoff. The sediment retention facilities currently employed (see Figures 1, 2 and 3) will be adequate

to capture this amount of water and detain it long enough for the suspended particles to settle out.

The stages of development in Figures 1, 2 and 3 show the main drainage paths as blue lines and the

two sediment retention basins as blue shapes. It can be seen that water runoff management will

remain unchanged through the life of the quarry and after decommissioning.

4.4. FLORA AND FAUNA

The changes to the operations of the quarry will not cause any additional area of natural vegetation

to be disturbed. The only vegetation that will be removed is that planted by the Operator on

stockpiles close to the existing location of the machinery shed. The removal of this vegetation is

included in the mining and rehabilitation plan previously submitted.

No habitat for native flora and fauna will be disturbed to facilitate this change to the process; there

will be no resultant adverse impact on native flora and fauna. The sediment retention ponds will

remain for the life of the quarry and after rehabilitation. When the entire site is vegetated it will no

longer be necessary to clean accumulated silt from the ponds.

The rehabilitated areas will be planted out with plants of local provenance generally in accordance

with the planting schedule in Table 2.


Integrated Land Management and Planning | Management commitments 17

Table 2: Planting Schedule

Zone Canopy Understorey Groundcover

Native woodland E. tenuiramis (silver peppermint) Acacia dealbata (silver wattle) Epacris myrtifolia (common heath)

E. amygdalina (black peppermint) Banksia marginata (honeysuckle) Lomandra longifolia (sagg)

E. globulus (blue gum) Allocasuarina littoralis (drooping sheoak) Kennedia prostrata (running postman)

Planting rate One plant per 9 square metres

Fertilizer Accompany the seedlings with slow release fertiliser, either 30g tablet or similar volume of pellets.

Improved pasture A commercial pasture seed mix based on Lolium perenne (Perennial ryegrass) Dactylis glomerata (cocksfoot) and trifolium. repens (white clover) if appropriate.

Alternatively a mixture of native grasses will not be as persistent or invasive. Suggested species include Themeda triandra (kangaroo grass), Danthonia caespitosa (wallaby grass) and Poa labillardierei (tussock grass)

Seeding rate Ryegrass, 10kg/ha Cocksfoot, 3kg/ha White clover, 2 – 4 kg/ha

Fertilizer Apply fertilizer 14:16:11 at a rate of 600 kg/ha if soil has been stockpiled for long periods.

Stabilisation works Acacia dealbata (silver wattle) Lomandra longifolia (sagg)

Alternative for erosion control is spray applied mulch with a mixture of grass annual seed and native plant seed included.

5. MANAGEMENT COMMITMENTS Table 3: Commitments Table

Item Description Timing Responsible

1 The quarry will be laid out such that stockpiles will provide a permanent barrier between the crusher and residences to the west and south.

On approval of change Quarry Manager

2 The crusher will only operate between 8:00 am and 4:00 pm on weekdays On approval of change Quarry Manager

3 Dust conditions will be constantly monitored and remedial measures including those outlined in the document will be deployed if an emission is likely.

Immediately and ongoing Quarry Manager

4 Stormwater runoff from the site will be controlled and directed to the existing sediment retention ponds The ponds and drains will be retained and remain unchanged.

Ongoing Quarry Manager


Integrated Land Management and Planning | Management commitments 18

5 This production change will not result in any extra clearing of natural vegetation. Ongoing Quarry Manager

6 The fuel storage tank will be located in an impermeable bund with a spill capacity of no less than 110 percent of the tank volume

Immediately and ongoing Quarry Manager

7 The quarry will be progressively rehabilitated as detailed in the Decommissioning and Rehabilitation Plan and in accordance with the requirements of the Mineral Resources Development Act 1995.

Ongoing Quarry Manager


Integrated Land Management and Planning | Conclusion 19

6. CONCLUSION The continued efficient operation of the Red Gravel Pit at Sandford will facilitate the development of

the Sandford – South Arm district by providing locally produced quality construction materials. As

transport costs, traffic congestion and green house gas emissions become a greater problem for

growth in construction, a locally situated quarry will be an asset for residents and businesses alike.

It is essential that the Sandford Quarry should produce the highest quality product that the natural

resource and skills of the Quarry Manager allow. At present this is not always the case and this

Development Application seeks to redress this situation.

Documents

Red Gravel Pit Sandford 1511 P/Mepa.tas.gov.au/documents/jenkins_red_gravel_pit_document.pdf · rock. The dolerite has weathered by a natural process of moisture penetrating the joints