NEW ROADS AND STREET WORKS ACT 1991
NORTH WEST HAUC
HIGHWAY AUTHORITIES AND UTILITIES COMMITTEE
NOTES FOR GUIDANCE
CRITERIA FOR INVESTIGATORY WORKS BY CORE SAMPLING (TRIAL HOLES)
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CONTENTS
Introduction
Section 1
Purpose
Section 2
Sample Selection and Identification Procedure
Section 3
Notification Requirements
Section 4
Monitoring Investigatory Works
Section 5
Validation of Testing Method and Material Testing
Section 6
Performance Requirements
Section 7
Core Sample Retention Period
Section 8
PCSMs
Section 9
Reporting Procedures
Appendix A
Guidelines for Compliance
Appendix B
Specimen Copy of Analysis Report
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Introduction
This document has been developed to provide a framework for investigating works by core
sampling. More consistent sampling and analysis methods should lead to an increased
confidence in the results obtained.
The document also introduces the idea that a reinstatement may contain a minor defect that
does not present a safety problem for users of the highway nor is likely to affect the
longevity or the integrity of that reinstatement. This is referred to as Technical NonCompliance (TNC).
What does this mean in practice?
A TNC reinstatement may be left in place without repair. It remains defective as defined in
the Act and the Highway Authority could, if necessary, require a TNC reinstatement to be
repaired at any time during its life. However, there would seem to be little point in requiring a
repair unless the circumstances change and the condition of the reinstatement deteriorates.
The benefits of the non-repair of TNC reinstatements are: Traffic is not disrupted by remedial work simply to correct a minor fault
Money is saved
Potentially damaging press and media coverage is avoided
The dis-benefits of the non-repair of TNC reinstatements are: Utilities may have difficulty recovering costs from contractors if repairs are required
at a later date
The identity of the owner of a reinstatement may become increasingly difficult to
identify over time
We would encourage the use of these Guidance Notes for the management of defective
reinstatements and invesigatory works.
This document has been prepared and approved by North West HAUC committee members
and submitted to National HAUC as best practice advice.
Signed on behalf of NWHAUC
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CRITERIA FOR INVESTIGATORY WORKS BY CORE SAMPLING (TEST HOLES)
1.
PURPOSE
The purpose of this publication is: -
1.1
1.2
i)
To set a framework for Highway Authorities and Undertakers whilst carrying out
coring activities; and
ii)
To enable individual or joint coring exercises to be carried out and to provide
assurances of the integrity of the results obtained.
General
i)
It is the responsibility of the body initiating the coring activity to ensure
compliance with all relevant legislation.
ii)
This document is primarily for core sampling but does not preclude investigation
by the use of other test holes, if necessary.
iii)
The overall thickness of the core and each individual layer shall be measured at
three points and averaged.
iv)
The HAUC Advice Note 1 entitled "Conciliation and Arbitration Procedure" may
be initiated in the event of failure to agree.
Reinstatement of Test Holes
The reinstatement of test holes shall be in accordance with the HAUC publication
entitled "Specification for the Reinstatement of Openings in Highways".
2.
SAMPLE SELECTION AND IDENTIFICATION PROCEDURE
2.1
Sample Selection
i)
ii)
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Where the purpose of the investigatory works is to assess and determine the
current performance trends, then: a)
Core sample sites and positioning shall be randomly selected;
b)
The number of selected sites should be proportional to the level of
Undertaker’s activity in any Undertaker’s area and this should be based on
historic or new work information whichever best reflects the current
situation;
c)
% split between c/w and f/w to be based on historical analysis or estimate
of future work;
d)
Core samples should be taken on works completed in the last six months.
Where the purpose of the investigatory works is to ascertain whether an
Undertaker has complied with the specification under the New Roads and Street
Works Act 1991, core samples may be taken by the Street Authority and/or the
Undertaker, as appear to them to be necessary.
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2.2
2.3
Identification
i)
All cores MUST be clearly identified by the Undertaker’s and/or Highway
Authority’s reference numbers.
ii)
Reinstatements selected for coring can be identified by one or more of the
following methods: a)
By a circle approximately 75mm
reinstatement;
in diameter painted on each
b)
By a photograph taken showing the circle and the reinstatement in
relationship to its surroundings;
c)
By a plan indicating the position of the reinstatement in the street.
Guidance on the Frequency and Siting of Test Holes
As a practical guide to reflect performance it is recommended that: i)
Minimum of 1 No core sample per 10 openings or 20 square metres or part
thereof; or
ii)
Minimum of 1 No core sample per 100 metre lengths of linear trench or part
thereof.
3.
NOTIFICATION REQUIREMENTS
3.1
Advance Notice of Coring Programme
The Highway Authority and Undertakers should advise of each phase of their
respective or joint coring programme, at least seven days prior to commencing work.
For rolling programmes, longer notice is desirable.
4.
MONITORING INVESTIGATORY WORKS
4.1
Investigatory Works Carried Out by Highway Authority
i)
The Undertaker should be invited to monitor Investigatory Works.
ii)
All core samples should be assessed and classified as follows: -
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a)
Technical Compliance: Where the reinstatement meets the requirements
of the HAUC specification;
b)
Technical Non-Compliance: Where a reinstatement does not meet all
the requirements of the HAUC specification and subject to agreement,
remedial works may not be necessary; and
c)
Defects: Where a technical non-complying reinstatement would warrant
remedial works.
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4.2
iii)
Guidance on core sample classification as either 4.1 ii) a) or 4.1-ii) b) is
contained in Appendix A.
iv)
The defective reinstatement defect regime (including remedial notices) shall
apply to 4.1 ii) c) above).
v)
In the event of a technical non-complying reinstatement 4.1-ii) b) above, all
reasonable costs should be recharged to the Undertaker in accordance with the
Code of Practice for Inspections.
Investigatory Works Carried Out by Undertaker
i)
The Highway Authority should be invited to monitor Investigatory Works.
ii)
The defective reinstatement defect regime (including remedial notices) shall
apply to defective reinstatements identified by core sampling. However,
defective reinstatement charges will not apply under these circumstances.
iii)
Undertakers are expected to carry out performance monitoring and should, as a
minimum, take core samples as follows: Openings per Annum
1
1,000
10,000
50,000
4.3
to
999
to
9,999
to 49,999
and above
No of Cores
50%
10%
5%
2%
Removal of Non-Compliant Reinstatement Construction
Once it has been decided that a core represents an area of reinstatement, which is
unacceptable, unless the whole of the reinstatement is removed, further cores should
be taken along the remainder of the trench/reinstatement to determine the extent of
the defective areas.
5.
VALIDATION OF TESTING METHOD AND MATERIAL TESTING
i)
Either the Highway Authority or Undertaker or their appointed/nominated third
party representative may undertake the investigatory works.
ii)
Where sample material is tested, such tests shall comply with the relevant
British or European Standard appropriate for that material and the "Specification
for the Reinstatement of Openings in Highways".
iii)
Any requirement for analytical testing of materials should be undertaken by a
NAMAS accredited Laboratory, approved to undertake such tests in accordance
with the procedures of the relevant British or European Standards.
iv)
The advice of an approved NAMAS accredited laboratory may be sought in the
event of a dispute or doubt over material specification and compliance, and
reinstatement performance.
v)
Depth measurement (thickness) of a core sample shall be exempt from 5 ii) and
5 iii) above.
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6.
PERFORMANCE REQUIREMENTS
6.1
For Core Samples up to and including 100mm in Diameter
i)
Overall thickness or surfacing material.
ii)
Individual layer thickness of surfacing material.
The following may be determined by mutual agreement: 

6.2
Correct material;
Compaction of surfacing material.
For Core Samples more Than 100mm in Diameter
i)
Overall thickness of surfacing material.
ii)
Individual layer thickness of surfacing material.
iii)
Correct material, by laboratory test.
iv)
Constituent materials determined by laboratory test.
The following may be determined by mutual agreement: 

6.3
7.
8.
Compaction of surfacing material;
Correct sub-base/backfill material.
Supplementary Information
i)
The Laboratory appointed to undertake testing may require additional cores in
order to satisfy and comply with minimum sample size for analytical purposes.
ii)
Analytical test shall include: binder, content; aggregate grading and identification
(i.e. limestone/gritstone/granite etc).
iii)
If the material source is known, then it is likely that the aggregate PSV values
will also be known (applicable to permanent and interim wearing course only).
CORE SAMPLE RETENTION PERIOD
i)
Highway Authority and Undertaker to be offered the opportunity of viewing the
cores within three months of the presentation of results.
ii)
Defective core samples shall be retained until remedial works have been
completed in accordance with the reinstatement specification.
PCSMs
Experience has shown that coring of PCSMs is difficult. Trials of alternative testing
methods are being considered.
9.
REPORTING PROCEDURES
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i)
A full report of each core sample taken shall be retained by the originator and
made available if required. A typical report is shown at Appendix B.
ii)
A summary report of quarterly results should be presented at Regional HAUC by
the relevant Highway Authority / Undertaker showing the following information: Name of Organisation
Time Period covered by report
Operating Unit/Area (where applicable)
Footway/Carriageway (split by road type where available)
Compliant/Defective
% Of Total (Compliant)
Total Numbers of Cores
iii)
A monthly summary of results shall be distributed to the relevant Highway
Authority/Undertaker showing the following information: Name of Organisation
Time Period covered by report
Operating Unit/Area (where applicable)
Footway/Carriageway (split by road type where available)
Compliant/Defective
% of Total (Compliant)
Total Numbers of Cores
Location of Each Core
Wearing Course Thickness
Basecourse Thickness
Notice Reference Number (if relevant)
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APPENDIX A
GUIDELINES FOR COMPLIANCE
Properties
Wearing Course Aggregate
Cut-Back Material
Stone Size Specified
Scor
e
2
2
1
2
Overall Thickness Required
See below
Variation in Layer Thickness
See below
De-Bonding
Compaction
2
1
2
1
2
2
1
2
2
Granular Sub-Base
Criteria
Limestone Aggregate Present
Evidence of Flux Oils
Carriageway
One Stone Size Variance, e.g. 6mm to 10mm
Two Stone Size Variance, e.g. 6mm to 14mm
Footway
Stone size larger than 6mm
Within acceptable range
Outside acceptable range
With acceptable range
Outside acceptable range
De-Bonding on Clean or Dirty Surfaces
Poor Compaction (Voids Present)
Wearing Course
Outside NWHAUC Agreement
Unacceptable or Contaminated Material
ACCEPTABLE INDIVIDUAL LAYER THICKNESS
WEARING COURSE
BASECOURSE
UNBOUND MATERIAL
-5mm of Specified Thickness
± 10mm of Specified Thickness
± 20mm if Specified Thickness
+10mm
Type 3 and 4 roads, a 25mm thick wearing course may be laid in place of the standard 40mm, provided
the total thickness of basecourse and wearing course is not reduced.
OVERALL THICKNESS OF BOUND MATERIAL
-15mm of combined thickness of all specified layers (Roads)
Minimum 100mm
OVER ENGINEERING (TO AN ACCEPTABLE STANDARD) IS AT ENGINEERS DISCRETION
SMALL REINSTATEMENTS
PERMANENT WEARING COURSE
(Type 3 & 4 Roads Only)
Classification
Technical Compliance
[4.1 ii) a)]
Technical Non-Compliance [4.1 ii) b)]
Defect
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i.e. less than 300mm width or less than 2 square
metres
Two 50mm thick layers may be laid in place of
standard 60mm and 40mm thickness
Total for Core
None
One Total
Two or more Total
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TYPICAL LAYOUT
APPENDIX B
CORE SAMPLE ANALYSIS REPORT
* Delete as appropriate
Core Sample Reference Number:
Promoter of Coring Programme:
Highway Authority/Utility *
Utility:
District/Operational Area:
Highway Authority Reference:
Utility Reference:
Inspection Category:
Road Reinstatement Type:
Date Reinstatement Carried Out:
Location:
Overall Dimension of Reinstatement:
Date Core Sample Taken:
Highway Authority/Utility Representatives on Site:
Core Sample Performance:
Material
Aggregate
Size
Specification
Thickness
Actual
Thickness
Wearing Course:
Base Course:
Sub-Base:
Other (state) ……………………:
Total Thickness of Bituminous Materials:
Compaction of Bituminous Materials:
Compliance with Specification:
Comments:
Signed: ………………………………………………
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Date: ……………………………………..
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