TARMAC LIMITED EXTENSION TO BORRAS QUARRY ... - Wrexham · Tarmac Limited Extension to Borras...

TARMAC LIMITED

EXTENSION TO BORRAS QUARRY

TRANSPORTATION ASSESSMENT

REF: RC4876/HJ/PS

Client Tarmac Limited

Client’s Agent Smiths Gore

Consulting Engineers Veryards Opus Ltd

Tunstead House

Buxton

Derbyshire

SK17 8TG

Tel: 01298 768 555

Fax: 01298 768 556

Croesnewydd Hall

Wrexham Technology Park

Wrexham

LL13 7YP

Tel: 01978 290 694

Fax: 01978 353 400

Burton House

Rossett

Wrexham

LL12 0HY

Tel: 01244 571 444

Fax: 01244 570 272

Tarmac Limited

Extension to Borras Quarry, Wrexham

Transportation Assessment: August 2005

1

CONTENTS

Page

1.0 Introduction 5

2.0 Assessment Methodology 7

3.0 County Road Scheme / Existing Conditions 8

4.0 Proposed Development 11

5.0 Trip Generation 12

6.0 Trip Distribution 16

7.0 Assessment Years/Growth of Network Traffic 18

8.0 Existing Highway Access 19

9.0 Proposed Access Improvements 22

10.0 Accidents 26

11.0 Highway Impact 28

12.0 Conclusions 32

Tables

Figures

Appendices

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List of Tables

Table 1 - Base Year (2005) Traffic Flows on A534

Table 2 - Hourly profile of vehicles leaving Quarry Sept 2002

Table 3 - Daily Trip Generation from Borras Quarry 2005

Table 4 - Predicted Daily Trips from Borras Quarry (2012-2024)

Table 5 - Predicted distribution of vehicles entering/leaving in AM peak hour – Yr 2017

Table 6 - Measured visibility at existing site access.

Table 7 - Summary of PICADY 4.1 Results – AM Peak Hour 2007

Table 8 - Summary of PICADY 4.1 Results – AM Peak Hour 2017

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List of Figures

Figure 1 - Existing Quarry access

Figure 2 - Proposed Plant Crossing of Borras Road

Figure 3- Location of PI Accidents (2002-2005) – A534

Figure 4- Location of PI Accidents (2002-2005) – Borras Road

Figure 5 - Predicted Weekday Traffic Flows at 2017 – With & Without Development

Figure 6 - Modelled Flows – AM Peak PICADY Assessments 2007 / 2017

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Appendices

Appendix A - ATC Data

Appendix B - Vehicle Speed Survey Results

Appendix C – Extract from Wrexham Industrial Estate Access Road Stage 2 Public Consultation

Appendix D - PICADY 4.1 Outputs

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1.0 INTRODUCTION

1.1 This report has been prepared to assess the transport and access issues related to the

Planning Application submitted by Tarmac Ltd to extend Borras Quarry, Wrexham

onto land at Borras Airfield and the Holt Estate land.

1.2 This report updates and replaces the Transporation Assessment prepared by

Veryards in 2003, which was included within the Environmental Statement

submitted in support of the Planning Application. It takes account of recent

amendments that have been made to the Planning Application and uses

contemporary traffic flow and accident data for the road network around the site.

Background

1.3 Planning permission for the extraction of sand and gravel at Borras Airfield and

Caia Farm, the two existing operational areas at Borras Quarry, was granted in 1965

and 1990 respectively. An application for the determination of new planning

conditions, under the 1995 Environment Act, which included Borras Airfield, was

approved in 2001 and the Airfield site is now subject to modern planning

conditions.

1.4 In 1997 Bodfari (Quarries) Ltd submitted a planning application to extract sand and

gravel from the Holt Estate. Bodfari (Quarries) Ltd was subsequently acquired by

the Tilcon Group.

1.5 In 1999 Tarmac Heavy Building Materials UK Ltd submitted a planning application

to extend the depth of workings at Borras Airfield and Borras Hall Farm.

Subsequently, the Tilcon Group and Tarmac Group merged to become Tarmac Ltd,

a wholly owned subsidiary of the Anglo American Group.

1.6 Both the applications described in paragraphs 1.4 and 1.5 were undetermined by

Wrexham County Borough Council (WCBC), the Mineral Planning Authority, and

have subsequently been withdrawn.

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1.7 This latest Planning Application proposes a revised working and restoration strategy

for Borras Quarry and the Holt Estate land, which has only become possible now

that all of this land is within Tarmac Ltd’s control.

1.8 The original planning application and accompanying Environmental Statement

(ES), was submitted in May 2003. It sought permission to continue working on the

existing Borras Quarry site, in a phased manner and to a selective depth below the

already permitted 62m AOD (but above the water table), and on the Holt Estate land

to the immediate north of the Airfield Site in 6 Phases.

1.9 This amendment now proposes the working of the Holt Estate land by eliminating

Phase 6 of the working programme and providing greater stand-offs from the limit

of sand and gravel extraction to residential properties. Phase 6 was intended to be

the last phase of working of the Holt Estate land but by excluding this phase it is

possible to retain a kettle hole and escarpment which were considered to be visually

important landscape features. Additionally, some minor boundary changes have

taken place on the southern area of the Holt Estate land. These revisions have been

brought about in response to issues raised by statutory and non- statutory consultees

and following the publication of the Minerals Technical Advice Note (TAN)

produced by the Welsh Assembly Government in 2004.

1.10 The blending ratio of the upper coarse sands and the fine lower sands remains the

same up to 2011 (2 upper coarse to 1 lower fine); from 2012 the blending ratio

changes to 1 to 1. The extractable sand and gravel resource has decreased from 14

million tonnes to 9.8 million tonnes within the Holt Estate land, giving an

extractable potential reserve of 17.7 million tonnes overall including the existing

Borras Quarry site.

1.11 The timescales for the proposal assumes that the Caia Farm sand and gravel

permitted reserve has been exhausted by the end of 2005. Working of the proposal

area would immediately follow the Caia Farm site and continue until circa 2030,

in a phased approach with progressive restoration following closely behind the

exhausted working phases.

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1.12 The planning application for the Holt Estate land submitted by Bodfari (Quarries)

Ltd in 1997 included proposals for a new access onto the unclassified ‘Borras

Road’, which leads onto the A5156 Llan y Pwll Link Road. This latest application

does not propose such a new access because the ownership arrangement now in

place means that all materials can be delivered / exported from the quarry via the

existing access on to the A534.

1.13 A replacement of the existing plant crossing of Borras Road will, however, be

required to allow limited traffic movements between Borras Airfield and the Holt

Estate land and this is discussed later within this report.

2.0 ASSESSMENT METHODOLOGY

2.1 The assessment of traffic impacts is usually undertaken using guidance published by

the Institution of Highways and Transportation (IHT). In line with accepted

methodology, a meeting was held with Wrexham County Borough Council, the

Local Highway Authority (LHA) at which an outline of the key elements was

discussed and the scope of assessment required was agreed.

2.2 The LHA acknowledged that previous planning permissions allow unrestricted use

of the existing vehicular access; however, some concerns were raised about the

amount of visibility available to the right along the A534 west for vehicles exiting

the quarry. The Authority’s representatives therefore indicated that if, as a result of

the present application, network traffic increased by in excess of 5%, they would

wish to see an improvement to level of visibility afforded in that direction from the

existing access.

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3.0 COUNTY ROAD SCHEME / EXISTING CONDITIONS

3.1 The LHA has a long standing proposal to improve access to Wrexham Industrial

Estate from the North and various alternatives have been the subject of Public

Consultation since 1987. The most recent proposal involved constructing a new

link road from the existing roundabout at A534/A5156 to the western side of the

Industrial Estate. This proposal would have reduced traffic flows along the A534 at

the existing junction to Borras Quarry.

3.2 The Minister for Environment at the National Assembly Government did not

confirm the Compulsory Purchase and Side Roads Orders for the scheme following

a Local Public Inquiry in February 2002. As a result, the LHA has recently

completed a ‘Stage 2 Public Consultation’ exercise at which four alternative routes

were presented for consideration.

3.3 The outcome of that process has recently decided in favour of the scheme that

involves a combination of upgrading and realignment of the A534 ‘Holt Road’

known as the ‘Blue Route’ (see plan at Appendix C). If the proposals are upheld by

the Executive Board and other statutory processes, then it is anticipated that work

on-site to construct the road could begin in 2008 subject to funding being made

available by the Welsh Assembly Government.

3.4 Consequently, traffic flows past the site access are not likely to be significantly

altered in the future, although, if the scheme is built, alterations to the existing

Quarry junction will be required as the outline scheme is for widening the A534 to

dual carriageway standard and an off-line realignment in the vicinity of the existing

Quarry access. These alterations would be the responsibility of the County Council

design team as part of the overall road scheme and any land-take requirements will

likely be met by Compulsory Purchase Orders.

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3.5 Due to the uncertainty in timescales and funding for the County scheme, it was

agreed that this report would evaluate the access arrangements on the basis of the

existing situation and that growth of base traffic, as presently recorded using the

A534, would be applied to future years on the basis that the County Council`s

scheme had not come forward.

Existing Site Access

3.6 The Quarry is served via a single access off the A534 Holt Road, Wrexham as

shown on Figure 1, (apart from the plant crossing on Borras Road). The principle of

this priority junction was approved in the 1965 planning permission for mineral

extraction at Borras Airfield. When consulted on the Application for Determination

of New Conditions under the Environment Act 1995, (granted in 2001) the Local

Highway Authority made no objection to the application on highways and

transportation grounds. These latest (2001) planning conditions for Borras Quarry

do not restrict the numbers of vehicles that can use the existing access and the time

limit for operations to cease at the Quarry extends to the year 2042.

Other traffic generators at the Borras Airfield site

3.7 Within the Borras Airfield site there are several other operations that generate traffic

and that use the same existing access with the A534 Holt Road. ‘Hanson’ operates

a concrete block production plant and an aggregate bagging plant and these generate

mainly heavy goods vehicle traffic. ‘Grampian Country Chickens’ generates a

modest amount of mainly light traffic; and the ‘St Christopher’s Eco Centre’

generates a very low level of light traffic. The traffic generated by all of these

operations is described in more detail in Section 5 of this report.

3.8 In terms of background traffic data, it was agreed at the meeting with the LHA that

the following would be obtained:-

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i) Automatic Traffic Count (ATC) data for the A534 (counter site west of

A534/Hugmore Lane Junction.

ii) Reported personal injury accidents along A534 between A534/A5156

roundabout and A534/Hugmore Lane Junction.

3.9 ATC data for the A534 from May 2005 (See Appendix A) and accident data for the

three-year period May 2002 – 2005 has been used as the base information for this

report.

3.10 With the agreement of the LHA, the National Road Traffic Forecasts (NRTF ’97)

‘low growth’ factors have been applied to these base flows when estimating future

traffic volumes.

3.11 Table 1 below shows typical 12-hour 4-day flows (Mon-Thurs) for the A534 in

2005. The table also shows peak hour morning and evening flows.

3.12 The morning peak period for traffic on the A534 is 08:00-09:00 hours for the

eastbound direction with the opposite (westbound) evening peak period being

between 16:00-17:00 hours.

A534 (Eastbound) A534 (Westbound)

Mon-Fri

average

12 hour

(Vehicles)

08:00 –

09:00

(Vehicles)

16:00 –

17:00

(Vehicles)

Mon-Fri

average

12 hour

(Vehicles)

08:00 –

09:00

(Vehicles)

16:00 –

17:00

(Vehicles)

May 2005 7379 1002 524 7656 522 1082

Peak Hour ratio of 12-hr

flow 13.5% 7.1% 6.8% 14.1%

Table 1 – Base Year (2005) Traffic Flows on A534

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4.0 PROPOSED DEVELOPMENT

4.1 The application site comprises Borras Airfield, where it is proposed to work below

the current permitted depth of 62 metres AOD, but above the water table, and the

Holt Estate land, where mineral will be extracted and transported by conveyor under

Borras Road to the existing processing plant at Borras Airfield, as presently occurs

where mineral is extracted from the Caia Farm site. It will be necessary, however,

for the conveyor location to be different from the present one.

4.2 Working and restoration will be phased progressively throughout the life of the

quarry as detailed in the Supplementary Statement and accompanying drawings.

Further information about the phasing of the workings is provided in the

Environmental Statement.

4.3 Restoration works will not involve the import or export of restoration materials

from the Site and all vehicle movements associated with these works will be

confined within the Site. Furthermore, there will be no inter-site movement of

restoration materials between the Borras Airfield and the Holt Estate areas.

4.4 The base data relating to output from Borras Quarry dates from 2002 when 611,275

tonnes of material was exported. It is at a similar level now and is expected to

remain at around that figure until the year 2012, after which it is anticipated to

increase to a peak of around 820,000 tonnes per annum. At these rates of

production the already permitted reserves, together with those within the

Application Site, are expected to last until around 2024 when output will fall to

approximately 402,000 tonnes per annum as a result of only the lower sands being

extracted.

4.5 The following Section will examine the traffic movements associated with the

existing operations at the quarry and the increase that is likely to be generated as a

consequence of the proposals comprising this planning submission.

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5.0 TRIP GENERATION

5.1 Load ticketing information from Borras Quarry has been used to determine an

hourly profile of loads leaving the quarry and is shown below in Table 2. The

following data relates to September 2002, however, as noted above the output has

remained at a very similar rate since and therefore it is still representative.

Hours No. of Loads

for month

Volumes

(Tonnes)

Average No.

of Loads per

day

0600 to 0659 145 3030 6

0700 to 0759 337 6595 13

0800 to 0859 319 6147 13

0900 to 0959 248 4825 10

1000 to 1059 360 7184 14

1100 to 1159 310 6177 12

1200 to 1259 195 3849 9

1300 to 1359 264 5449 13

1400 to 1459 290 5868 14

1500 to 1559 273 5308 13

1600 to 1659 162 3237 8

1700 to 1759 1 16 1

TOTAL 2904 57685 126

Table 2 – Hourly Profile of Vehicles Leaving Quarry – Sept 2002

5.2 It can be seen that the vehicles leaving the quarry are generally distributed evenly

throughout the day between 08:00 and 17:00 hours. The figures in the table include

trips on Saturdays when the quarry is open for HGV movements between 06:30 –

12:00 hours and ticketing information shows that an average of 19 vehicles leave

the Quarry on Saturdays.

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5.3 Typically 126 heavy goods vehicles leave the Quarry each day. Weekday working

hours for HGV movements are 06:30 – 18:00 hours. On average 13 trips are made

to and from the Quarry on a weekday during the network morning peak, with less

than this generally occurring during the evening peak hour.

5.4 From the information provided, and as summarized in Table 2, each heavy goods

vehicle leaving the Quarry carries an average payload of around 20 tonnes.

5.5 The output from the Quarry in the year 2002 was 611,275 tonnes. On the basis that

there are 46 working weeks per annum, and 5½ working days per week, division of

the annual tonnage by the average payload figure typically equates to a predicted

122 loads per day. This compares well with the ticketing information provided by

Tarmac for September 2002, underlining the validity of the profile outlined within

Table 2.

5.6 Tarmac has advised that, in a typical week, 210 tonnes of aggregate is transferred

internally to the ‘Hanson Pre-Packed Products’ bagging operation. This material is

included in the annual output noted in Paragraph 5.5 above.

5.7 The operations at Borras Quarry also include the importation of limestone fines,

which are blended with sand and gravel from the Quarry and then exported by road.

The volume of limestone fines imported to Borras Quarry is currently around

65,000 tonnes per annum and, in line with the sand and gravel output, this is

expected to increase to around 90,000 tonnes per annum in 2012.

5.8 The majority of vehicles bringing limestone fines to the Quarry leave carrying sand

and gravel products, and hence an efficient “double haul” arrangement operates.

5.9 For the purposes of the assessment it is assumed that 10% of vehicles carrying

imported limestone fines leave empty. On a typical day, 13 vehicles enter the

Quarry carrying limestone fines and hence all but 2 leave carrying sand and gravel.

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5.10 Information concerning the heavy goods vehicle movements associated with the

concrete block plant operations out of Borras Quarry has been provided by Hanson

Concrete Block.

5.11 This information was included in a previous Transport Assessment, which was

prepared in support of a planning application to extend the depth of working at the

quarry in 1999. It is understood that there has not been any significant change to

output from the Block Factory since 1999; therefore this assessment assumes similar

outputs and traffic generation to the previous report.

5.12 In a typical week, 190 heavy goods vehicles deliver imported aggregates to the

Block Factory and leave empty and an additional 240 heavy goods vehicles arrive

empty and leave with finished products. For a 5 day working week this therefore

equates to 38 heavy goods vehicles trips for aggregates per day and 48 for finished

products.

5.13 An office block located within the southern part of the Airfield is leased by

Grampian Country Chickens. There are around 25 employees at the office and if it

is assumed that the Government’s transport energy unit figure of 70% typical car

usage for travel to work applies, this would result in 18 return staff trips per day for

that concern.

5.14 The ‘St Christopher’s Eco Centre’ is a small building within the southern part of the

Airfield and is used by local school and community groups. It attracts only a very

small number of light vehicles trips each day and employs 2 people.

5.15 The Quarry employs 16 staff directly, and applying the previously outlined ratio of

70% car usage for travel to work this would therefore give a predicted total of 11

return trips per day for these.

5.16 In summary, Table 3 below shows the total trips that are typically generated by the

current operations at the Borras Airfield site.

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Operations Vehicle Nos.

In Out

HGV’s Light

Vehicles

HGV’s Light

Vehicles Quarry - Sand and Gravel 115 126

- Limestone 13 2

Hanson Concrete Block (Aggregate) 38 38

Hanson Conc. Block (Finished Products) 48 48

Eco Centre 2 2

Grampian Country Chickens 18 18

Quarry Employees. 11 11

Total 214 31 214 31

Total (all Vehicles) 245 245

Table 3 – Daily Trip Generation from Borras Quarry 2005

5.17 The following paragraphs will review the increase in trips that are likely to result

from the Application proposals.

5.18 Based upon an output of 820,000 tonnes per annum over a 5½ day working week

for 46 weeks of the year, the number of heavy goods vehicles leaving the Quarry on

a typical weekday would increase to approximately 174, (assuming 25 trips are

made on a Saturday).

5.19 This represents an increase of 48 heavy goods vehicles per day from the present

time to the year 2012.

5.20 Similarly, there would be a concomitant increase in the importation of limestone for

blending with the sand & gravel from the present 65,000 tonnes per annum to

around 90,000 tonnes per annum and this would result in the numbers of heavy

goods vehicles associated with that task increasing from approximately 13 to 18 per

day. As previously explained, however, the majority of these vehicles subsequently

leave the Quarry carrying sand and gravel and hence all but 2 will already be

included within the 174 HGVs associated with outgoing trips from the Quarry, as

noted above.

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5.21 By comparing the present day HGV movements with those post 2012 (Tables 3/4) it

can be seen that the number entering and leaving the Quarry will likely increase

from approximately 214 to 262 per day. It is not anticipated that vehicle numbers

will increase beyond the 2012 rate and from circa 2024, output will progressively

fall until the Quarry workings are exhausted, circa 2030, and site restoration is

completed.

5.22 Table 4 shows the anticipated trips that will be generated at the peak output period

of operations at the Borras Airfield site between the years 2012 to 2024. The

figures assume that vehicle movements associated with the other operations at the

Quarry will remain as for the present day.

Vehicle Nos.

IN OUT

Operations

Heavy

Goods

Light

Goods/Cars

Heavy

Goods

Light

Goods/Cars

Quarry - Sand & Gravel

- Limestone

158

18

-

-

174

2

-

Hanson Concrete Block

- Aggregate

- Finished Products

38

48

-

-

38

48

-

-

Eco Centre - 2 - 2

Grampian Country Chickens - 18 - 18

Quarry Employees - 11 - 11

262 31 262 31

TOTAL 293 293

Table 4 – Predicted Daily Trips from Borras Quarry Years 2012 - 2024

6.0 TRIP DISTRIBUTION

6.1 Ticketing information provided by Tarmac indicates that the majority of heavy

goods vehicles leaving the Quarry turn right onto the A534 and travel west towards

Wrexham. A number of loads are delivered daily to Hanson’s Concrete Batching

Plant near to Borras Quarry - located just 500 metres west of the Quarry access

along the A534.

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6.2 The ticketing information showed that 91% of vehicles leaving the Quarry turned

right towards the A5156 (west) and that the majority of this traffic would then turn

right at the A5156/A534 roundabout to travel along the A5156 Llan y Pwll Link

Road for destinations north and south on the A483 trunk road. A small number of

vehicles turn left at the roundabout towards Wrexham.

6.3 Information provided by Hanson Concrete Block showed a similar pattern, with

89% of vehicles delivering aggregate turning left from A534 into the Quarry, and

around 70% of vehicles exporting finished product turning right towards the A5156

(west). Information from the Hanson Pre-Packed Products aggregate bagging

operation showed that 90% of traffic entered and left the Quarry from the A534

west (Wrexham side).

6.4 With regards to the Eco Centre and employees of Grampian Country Chickens and

the Quarry, based upon the above measured patterns, this assessment assumes that

90% of such traffic enters and leaves the Quarry from the west. The following Table

5 outlines the resulting flow distribution in the morning weekday peak hour at the

Quarry access to the ‘design year’ 2017. An explanation regarding the choice of

‘design year’ is provided below.

From

A534 West

To

A534 West

From

A534 East

To

A534 East

Quarry - Sand and Gravel 16 17 1 2

- Limestone 2 1 0 0

Hanson Concrete Block

(Aggregate)

5

5

1

1

(Finished Product) 6 4 1 3

Eco Centre 1 0 1 0

Grampian Country Chickens 17 0 2 0

Quarry Employees 11 0 1 0

Total 58 27 7 6

Table 5 – Predicted distribution of vehicles entering / leaving

Borras Quarry access during AM peak hour at Year 2017

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7.0 ASSESSMENT YEARS / GROWTH OF NETWORK TRAFFIC.

7.1 It is usual practice to deal with two or more assessment years for proposed

development impact and junction capacity analyses. The first is generally taken as

the year of opening and the second a period of 10 or 15 years after opening, this

being referred to as the ‘design year’.

7.2 In the case of existing or modified junctions a 10-year model is analysed.

7.3 This is undertaken in order to ensure that junctions have sufficient capacity to cater

for anticipated growth of network traffic as well as being able to accommodate that

generated by the proposed development.

7.4 For the purpose of this assessment the ‘opening year’ is assumed to be 2007 and

hence the design year will be 2017. It is usual practice to increase the volume of

existing network traffic to the future assessment years to reflect anticipated trends

and in order to provide a robust estimate of traffic flows likely to be using the roads

and junctions under consideration.

7.5 Base traffic flows (year 2005 See Table 1) to the years 2007 and 2017 have

therefore been increased by the application of ‘low growth’ factors as set out in the

National Road Traffic Forecasts published by the Department of the Environment,

Transport and the Regions (DETR), last updated in 1997 (NRTF97). The

assessments have been undertaken for the busiest hour on the network, this being

the 08:00-09:00 morning peak.

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8.0 EXISTING HIGHWAY ACCESS

8.1 The existing site access consists of a simple priority junction with merge and

diverge lanes on the A534 as shown at Figure 1. The junction does not include a

dedicated right turn lane for Quarry bound traffic from the east. At the point of

connection the A534 measures approximately 7.3 metres wide and includes a

1.5metre wide footway on the northern (Quarry) side. There is an area of widened

carriageway opposite the junction, which is sometimes used by heavy goods

vehicles when making a right turn from the Quarry. Access to a farm and houses is

also taken directly from this area.

8.2 The access road into the Quarry rises starts off at a shallow gradient before rising

sharply at an approximate gradient of 12% from a point around 10 metres back from

the edge of the A534 and continues to rise at a similar rate northwards along its

length into the main Quarry area.

8.3 From a visual inspection the Quarry access road appears to be in a good condition,

although some of the road markings near its junction with the A534 are worn.

Within the mouth of the junction parts of the carriageway adjacent to the A534 have

been recently repaired and this was carried out within the past twelve months as part

of the works to resurface the A534 - at which time fresh road markings were also

applied to the main road. (See also Section 9)

8.4 Measurements have been taken on site to determine the amount of available

visibility along the A534 for vehicles leaving the Quarry access. The A534 at this

point is derestricted (i.e. subject to the national speed limit of 60 mph).

8.5 Planning Guidance (Wales) Technical Advice Note 18 ‘Transport’ provides

guidance on desirable visibility distances at junctions. It states that, in the absence

of measured speed data, a junction joining a main road that is subject to a speed

limit of 60 mph should provide drivers with clear visibility for a minimum distance

of 215 metres along the major road (the ‘y’ distance) in both directions from a set

distance back into the side road (the ‘x’ distance).

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8.6 The ‘x’ distance varies from 2.4 to 9m depending upon the volume of traffic using

the side road and for an access such as at Borras Quarry the appropriate ‘x’ distance

would be 4.5m. The area contained within these measurements is generally referred

to as the visibility envelope.

8.7 Acceptance of a 4.5m ‘x’ distance in this case has been confirmed with the Local

Highway Authority and is considered appropriate for the junction, taking into

account the nature and volume of vehicles exiting the site and also reflecting the

fact that the seating position of drivers of heavy goods vehicles is generally closer to

the front of the vehicle when compared to car drivers. Visibility is required from an

‘eye height’ of 1.05m. This height is representative of most car drivers; however,

the higher seating position of heavy goods vehicle drivers’ means that they will

have an increased amount of visibility and therefore the distances measured should

represent a minimum value.

8.8 The following Table 6 shows the measured visibility distances at the existing

junction. Measurements were taken to the point where vehicles become visible

within the carriageway. Measurements are generally taken to the nearside, however,

the offside distance has also been measured in this instance to the east, as the A534

has double white centre lines at this point dictating that approaching traffic would

always be on the off-side.

‘x’ distance site

access.

Max ‘y’ distance

to the left

(looking east).

Max ‘y’ distance

to the right

(looking west)

4.5m 150m nearside kerb

160m offside lane 95m nearside kerb

Table 6 – Measured visibility at existing site access

8.9 In order to evaluate the visibility available against desirable minimum standards, a

vehicle speed survey was carried out at the existing Quarry access in accordance

with the Design Manual for Roads and Bridges (DMRB) Technical Advice Note TA

22/81. (See Appendix B for results of speed survey).

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8.10 During the speed survey it was apparent that many vehicles travelled in ‘convoys’

behind heavy goods vehicles en-route to and from Wrexham Industrial Estate,

because of the lack of overtaking opportunities along the A534 between the A5156

roundabout and Hugmore Lane junction. Vehicle speeds were recorded in both the

morning and afternoon periods for a minimum sample of 100 vehicles in each

direction and these were measured under ‘free flow’ conditions. (i.e. vehicles

travelling in convoys as outlined above were ignored).

8.11 Technical Advice Note TA 22/81 requires that the 85th

percentile wet weather

speeds are then determined from the measured samples, and in this instance these

were calculated as being 53 mph for westbound traffic (towards Wrexham) and 51

mph for eastbound (towards Holt).

8.12 Where speeds have been measured in this way Design Bulletin DB32, published by

the Department of Environment and Transport (now DETR), specifies that the

visibility distance required along the major road can be amended to be

commensurate with existing site conditions.

8.13 In the case of the Borras Quarry access, this would therefore amend the ‘y’ distance

required to 160 metres in each direction.

8.14 In comparing the measured visibility outlined within Table 5 to that specified in

DB32 for new/improved junctions it is apparent that whilst adequate visibility is

available to the left, the visibility to the right is substandard and the Highway

Authority has expressed a desire that this be improved if possible. The works

proposed at the access as part of this latest planning application are outlined below.

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9.0 PROPOSED ACCESS IMPROVEMENTS

9.1 The carriageway surfacing on the A534 past the junction has been replaced in the

past twelve months and consequently is in excellent condition and will offer a good

level of skidding resistance. As part of this work new road markings have also been

applied.

9.2 As noted within Section 8, a few of the existing road markings within the Quarry

approach to the junction with the main road are worn and would benefit from

replacement. The existing arrangement includes only edge of carriageway markings

along the A534, as opposed to ‘give way’ or ‘stop’ line markings as would typically

be expected.

9.3 There is presently no road lighting provided around the junction and the existing

access lacks ‘presence’ as there are no advanced signs to alert other road users on

the A534 to its existence, or that HGVs could be emerging ahead.

9.4 Whilst the access is generally in a good condition it is suggested that it would

benefit from a number of improvement measures including:-

• Application of high-friction surfacing within the Quarry access approach

• Replacement of the existing road markings with a ‘Stop’ line layout

• Inclusion of road lighting in the vicinity of the junction

• An improved signage strategy for each approach on the A534

9.5 These improvement measures would be developed in consultation with the Local

Highway Authority and could therefore be covered by an appropriate planning

condition, should planning permission be granted for the Quarry proposals.

9.6 Whilst the existing Quarry access does not have a poor accident history, as noted,

the LHA has expressed the desire that visibility to the right along the A534 for

vehicles leaving the Quarry be increased; to bring the amount afforded in that

direction in line with desirable minimum standards.

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9.7 Visibility from the 4.5m minor road distance is restricted by the presence of an

embankment and hence, in order to increase the amount available, it will be

necessary to set-back the embankment by means of a retaining wall. These works

involve land outside Tarmac Ltds ownership or control, however, Tarmac Ltd has

negotiated a possible means to deliver the improvement and have submitted a

separate planning application in respect of the required works.

9.8 It is noteworthy that Tarmac Ltd is aiming to carry out the visibility improvement at

significant expense, despite the fact that the existing access does not presently have

any restrictions on its level of usage. The Quarry access would be revised in the

future in any case as a consequence of the County Council`s ‘Industrial Estate

Access Road’ improvement scheme, however; the works outlined above are

intended to provide additional road safety measures in the interim period.

9.9 As noted earlier, the County Council has recently completed the “Stage 2 Public

Consultation” exercise in respect of the access routes serving Wrexham Industrial

Estate. This process has been required following the rejection of an earlier route at

Public Inquiry.

9.10 The latest Consultation process has found in favour of the ‘Blue Route’ scheme and

this involves upgrading the A534 between the A5156 Llan-y-pwll link and Borras

Hall Lane, a short distance to the east of the Quarry access.

9.11 From that point, a new road would be provided southwards into the Industrial

Estate. (See extract from Consultation leaflet provided at Appendix C).

9.12 The proposals involve widening the A534 to dual carriageway standard both on the

line of the existing road and in parts via new sections of road off the present line.

One of these off-line sections will be near to the Quarry access where the route is

shown to pass behind (to the north of) the Gredington Arms public house and

through the existing Quarry access road.

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9.13 Consequently, the County road scheme will sever the existing Quarry access road

and will, by necessity, require a replacement junction to be provided to serve the

Quarry. It is understood that as the A534 will be of dual carriageway standard the

replacement Quarry junction will comprise a left-in / left-out arrangement and hence

will require that all vehicles leaving the Quarry travel eastward to a proposed

roundabout at the end of Borras Hall Lane in order to turn west at that junction, if

that is their destination.

Replacement Plant Crossing of Borras Road

9.14 A very small number of Quarry vehicles currently cross Borras Road each day to

travel between the Caia Farm extraction site and the Borras Airfield site, which are

separated by Borras Road. The vehicles primarily comprise maintenance vehicles

and quarry related plant such as loading shovels.

9.15 Tarmac Ltd has recently carried out improvements to the existing crossing,

including the erection of new fencing to improve visibility and the provision of new

signing.

9.16 Once the Caia Farm site is exhausted, a new plant crossing of Borras Road will be

required as shown on Figure 2. This will operate on the same basis as the existing

crossing and is necessary to allow occasional quarry traffic to travel between the

proposed Holt Estate land and the Borras Airfield site.

9.17 The crossing would be used in the same way as at present which comprises a large

wheeled loading shovel which crosses the road at around 07:00 hours and 17:30

hours each day and a “pick-up truck” that may cross the road up to 8 times a day

between the hours of 09: 00 and 12:45 hours.

9.18 The location proposed for the replacement plant crossing has been discussed and

reviewed on-site with the Local Highway Authority.

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9.19 In order to minimize disruption to existing trees etc, the proposed crossing would be

located alongside the conveyor underpass that would pass beneath Borras Road.

9.20 Referring to Figure 2, the crossing would be located on a straight section of Borras

Road, however, there are two tight bends in the existing road to the south and these

serve to constrain vehicle speeds from that direction. Similarly, to the north of the

proposed crossing point the existing road is relatively narrow and has a sinuous

horizontal alignment.

9.21 Observation would suggest that the speed of traffic using Borras Road is modest and

it has therefore been agreed with the Local Highway Authority that visibility splays

of 4.5x90m would be provided to each side of the crossing. In addition, and in order

to give advanced warning to other road users, flashing signs would be installed at

each approach on Borras Road to indicate that the crossing was in use.

9.22 It is proposed that these warning signs would be activated by the quarry vehicles by

means of sensors located in the access tracks each side of the crossing and therefore

would only be called into use as and when required.

9.23 This would serve to reinforce the importance of the signs. Otherwise the infrequent

level of use of the crossing could result in drivers on Borras Road ignoring less

prominent signage systems, such as warning signs only containing text.

9.24 Provision of the required visibility splays at the plant crossing will necessitate the

loss of several existing trees and parts of hedgerows to each side of the road,

however, this loss would be compensated for elsewhere as part of the

comprehensive landscaping scheme proposed for the overall site.

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10.0 ACCIDENTS

10.1 Three years accident data has been obtained for the length of the A534 on the

approaches to the access to the Quarry from the A5156/A534 roundabout to

A534/Hugmore Lane junction and for Borras Road over the lengths covering both

the existing and proposed plant crossings. The locations and classifications of the

accidents are shown on Figures 3 and 4.

10.2 There have been two ‘slight’ injury accidents in the immediate vicinity of the A534

Quarry junction in the past three years with one of those involving a vehicle exiting

the Quarry access. One of the incidents comprised a rear-end collision between

three cars all travelling east along the A534, the reason for the accident being

unknown. The second occurred when a vehicle emerging from the Quarry collided

with a van on the A534; the driver of the vehicle leaving the Quarry claimed,

however, that the van driver flashed his headlights to signal for him to emerge.

10.3 There have been a further 21 accidents along the length of the A534 between the

A5156 and Hugmoor Lane during the last three years, however, none of these has

involved HGVs associated with the sand and gravel quarry at Borras Airfield.

10.4 The majority of the accidents have been as a result of car drivers losing control of

their vehicles and this may relate to travelling at speeds in excess of a safe limit

given the sinuous alignment of the existing A534. The data provided does not

indicate whether the road was wet or dry in these incidents, however, it is likely that

the recent resurfacing works carried out by the LHA will assist in this regard.

10.5 Two of the accidents were of the ‘serious’ injury category as in one the car over-

turned and rolled into an adjoining field and in the other a car strayed across into the

opposing lane, and hit an oncoming vehicle. All of the remaining accidents were

within the ‘slight’ category. There have been no fatalities on the road in the past

three years.

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10.6 The number of recorded accidents along the A534 is high and indicates that the

County Council`s proposed improvement scheme would undoubtedly result in

improved safety and a reduction in accidents in the future. The data provided does,

however, indicate that although the existing Quarry junction has substandard

visibility to the right (for traffic emerging from the Quarry) it does not have a poor

safety record.

10.7 In tandem with the improvements that are proposed at the access, as outlined in

Section 9, the accident data would suggest that the minor increases in traffic

movements associated with the Quarry proposals will not prejudice highway safety

beyond present levels. In fact, the measures outlined will result in improved

standards and potential safety gains for all road users in the vicinity of the Quarry

access.

10.8 With regard to Borras Road, there have been no reported personal injury accidents

at the existing plant crossing in the past three years. There have, however, been four

accidents further east nearer to the proposed plant crossing location.

10.9 Three of these have occurred at the tight bends that lie to the south of the proposed

crossing and in each case the cause has been loss of control. Two of these accidents

involved ‘slight’ injuries and 1 ‘serious’. All of the accidents took place in hours of

darkness and at a similar time of year with two occurring at the end of October and

one at the end of November. It is therefore feasible that slippery road conditions

may have been contributory factors in addition to the likelihood of excessive speed

for such conditions.

10.10 The fourth accident was of the ‘slight’ category and occurred to the north of the

proposed plant crossing when a car and tractor travelling in opposite directions

along the lane failed to stop in time and collided.

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10.11 Tarmac recognize that the proposed plant crossing will need to incorporate safety

measures such as conspicuous advanced warning signs and it is therefore proposed

that the final details be developed in close consultation with the Local Highway

Authority.

10.12 The proposed works could include a review of the existing road signs and markings

and enhancement of these local to the crossing, if deemed appropriate by the Local

Highway Authority.

11.0 HIGHWAY IMPACT

11.1 The ‘impact’ that the introduction of new traffic may have upon an existing road

network can be assessed in a number of different ways. The aspects most likely to

be affected can be examined and possible mitigation measures suggested, if

appropriate. Examples of potential impact areas include such elements as:-

• Negative influence on existing road users

• Sensitive locations (such as schools)

• Public transport

• Junction capacity

11.2 Relative to the above categories, the potential impacts could include such factors

as:-

• Community severance

• Safety, noise and intimidation

• Insufficient public transport provision

• Increased delays with associated safety reduction.

11.3 This report concentrates upon the possible physical traffic impacts relating to

highway capacity and safety issues.

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11.4 Figure 5 provides predicted weekday traffic flows on the approaches to the junction

for the ‘design year’ 2017, both with and without the development in order to

illustrate the resulting magnitude of change. The predictions in Figure 6

demonstrate that the increase in traffic up to 2017 resulting from the Borras Quarry

operations is insignificant in capacity or impact terms (i.e. less than 5%).

11.5 The ‘Guidelines for the Environmental Assessment of Road Traffic’ published by

the Institute of Environmental Assessment (IEA) (1992) provides accepted

thresholds at which ‘impacts’ from changes in the magnitude of traffic using a road

may be considered as being material.

11.6 ‘Rule 1’ of the guidelines states “include highway links where traffic flows will

increase by more than 30% (or the number of heavy goods vehicles will increase by

more than 30%)”.

11.7 ‘Rule 2’ states “include any other specifically sensitive areas where traffic flows

increase by 10% or more”. The ‘sensitive areas’ would apply where the

development traffic would all pass by a school, for example, or would use roads that

are already heavily congested.

11.8 The IEA guidelines provide data based upon previous research into discernable

environmental impacts and lists three categories; “substantial”, “moderate” and

“slight” for changes in traffic flows of 90%, 60% and 30% respectively. In relation

to changes in traffic volumes of less than 19% the guidelines state that noise impact

(for example) would be “not perceivable”.

11.9 This is because traffic flows on any road can fluctuate on a daily basis (typically by

approximately 10%) and so minor variations cannot be readily discerned. Highway

Authorities may request that capacity analysis be carried out at already congested

locations if the introduction of development generated traffic would increase the

volume using junctions by more than 5%. This does not apply to any of the existing

junctions used by quarry traffic beyond the site access itself.

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11.10 In line with the above therefore, the capacity of the Quarry junction has been

checked to the design year. Network traffic flows on the A534 were increased to the

year 2017 using ‘low growth’ National Road Traffic Forecasts as previously

described. The LHA has confirmed that low growth is appropriate for the A534 in

advance of their proposed improvement scheme, and this will provide a robust

assessment of the future years in a “do-nothing” situation in respect of that project.

11.11 The capacity of the Borras Quarry junction with the A534 has been assessed for the

opening and design year am peak hours using the flows shown on Figure 6.

11.12 PICADY 4.1 is a computer program for predicting capacities, queues and delays at

priority junctions. PICADY estimates capacity in terms of Ratios of Flow to

Capacity (RFC) and maximum queues (Q). The normally accepted maximum RFC

is 0.85 or 0.75 in the case of rural derestricted roads. However, RFC’s in excess of

these values may be acceptable if the associated queues and delays are within

reasonable limits.

11.13 The geometric parameters required for input to PICADY 4.1 for the Quarry junction

/ A534 capacity assessment were based on a combination of on-site measurements

and extrapolation of site survey data.

11.14 The design flows illustrated were input to PICADY 4.1 using the ‘Levels’ option to

synthesize a ‘normal’ peak period curve profile. The percentage of heavy goods

vehicles for traffic on the A534 was assumed to be 15% in each direction and a

same percentage value was applied to daily trips associated with Hanson Concrete

Blocks operations to estimate a robust peak hour figure.

11.15 The capacity of the Quarry access was assessed for the morning peak hour in both

2007 and 2017 and the results are summarized in Tables 7 and 8 below. The full

printouts are included in Appendix D.

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Road Demand/Capacity

(RFC)

Queue Vehicles

A534 (from Holt) 0.032 0

Quarry Access 0.273 0

Table 7 – PICADY 4.1 Results – AM Peak 2007

Road Demand/Capacity

(RFC)

Queue Vehicles

A534 (from Holt) 0.056 0

Quarry Access 1.25 3

Table 8 – PICADY 4.1 Results – AM Peak 2017

11.16 The results indicate that the junction is operating with plenty of surplus capacity at

2007 (i.e. traffic flows similar to the present-day) but that the addition of growth to

background flows to the design year 2017 has a negative influence upon the

capacity of the site limb (i.e. ‘gap’ availability is reduced). In the design year the

approach from the Quarry is shown to have no residual capacity and a queue of up

to 3 vehicles waiting to leave the site is predicted.

11.17 This situation would occur even without the very modest increase in traffic resulting

from the Quarry proposals, and it is noteworthy that it would not affect general

network traffic as no queuing of vehicles turning right from the A534 into the

Quarry is predicted.

11.18 It can be concluded that as the future hourly Quarry traffic flows are very similar to

present day, there will be no detrimental affects upon other more remote junctions

used by Quarry traffic, as the magnitude of change would not be discernable. (e.g. at

the A5156/A534 roundabout or A534/Hugmore Lane). As noted previously, traffic

generation associated with the proposed development will not result in a significant

(5% or more) increase in network traffic.

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12.0 CONCLUSIONS

12.1 The existing Borras Quarry junction onto the A534 has approval under previous

planning permissions and there are no restrictions on the numbers of heavy goods

vehicles that can use it. The Borras Airfield permission allows quarrying and

associated operations, including the use of the existing access, to continue up to

2042.

12.2 The proposed development will not significantly increase traffic movements at the

Quarry access above current levels and it has been shown that the existing junction

has sufficient capacity to cater for network traffic movements to beyond the design

year of 2017 (i.e. no delays are predicted on the A534).

12.3 The Local Highway Authority proposal to replace the A534 between the

A5156/A534 roundabout and Wrexham Industrial Estate will result in a significant

upgrading of the standard of that road and will necessitate replacing the access

currently serving the Quarry. This factor has been ignored within the assessments

carried out for this report.

12.4 It has been shown that the existing site access has a good safety record despite the

fact that visibility to the right at exit is less than desirable. Notwithstanding this,

(and the fact that consent for unlimited use exists), measures are proposed to

address identified deficiencies within the existing Quarry junction layout. These

improvements would be carried out to increase safety in the vicinity of the junction

for all road users in the interim period between the present day and construction of

the County Councils replacement road scheme for the A534.

12.5 A new plant crossing will be required on Borras Road to cater for a small number of

Quarry vehicle movements each day between the Holt Estate land and the Borras

Airfield site for future quarrying operations. The design of this crossing would be

developed in consultation with the Local Highway Authority and would incorporate

advanced warning signs for other road users.

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12.6 The improvements outlined at the existing Quarry access would similarly be

developed in consultation with the Local Highway Authority and would bring about

an increase in highway safety when compared to the present situation.

12.7 Overall, it has been shown that the application proposals would not increase traffic

volumes on the local road network by a degree that would be likely to result in any

discernable environmental or capacity impacts. In realistic terms the magnitude of

change will not be noticeable when compared to the present day.

Veryards Opus

Consultant Engineers

August 2005.

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APPENDIX A

ATC DATA

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APPENDIX B

VEHICLE SPEED SURVEY RESULTS

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APPENDIX C

EXTRACT FROM WCBC INDUSTRIAL ESTATE

ACCESS ROAD STAGE 2 PUBLIC CONSULTATION

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APPENDIX D

PICADY 4.1 – OUTPUTS

TARMAC LIMITED EXTENSION TO BORRAS QUARRY ... - Wrexham · Tarmac Limited Extension to Borras...

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