4 Project planning

NOTE Utility surveys should be approached holistically both in the planning and execution; it is a synthesis of the results of a number of technologies and methodologies deployed on the site. Utility surveys should be planned by the client in conjunction/ consultation with a trained, skilled and experienced practitioner. The project requirements should be clearly specified in tender and/or contract documentation. For guidance on specifying a utility survey, see TSA's The essential guide to utility surveys – Detailed guidance notes for specifying a utility survey [NR1]. Survey techniques and methodologies vary considerably, with each having their own advantages and disadvantages. The more intensive utility surveys have the potential to produce results that are more accurate but at an increased cost. When responding to a client's specification, the practitioner should address whether the client has taken into account some or all of the following considerations in the scope of work at the earliest possible opportunity.

  • a) Has a desktop utility records search been undertaken within the last 90 days?
  • b) Are the results to be marked onto the ground?
  • c) Are the results to be fully mapped in CAD/GIS/BIM?
  • d) Are the results to be marked onto the ground as well as being fully mapped in CAD/GIS/BIM?
  • e) What consideration should be given to any CADI GIS/BIM outputs? Is the existing base mapping at a scale suitable for the proposed project or is there a need to commission a new survey?
  • f) Do you have the legal rights or permission for the use of any existing base mapping?
  • g) Has the survey area been clearly defined?
  • h) Are there any areas of particular concern that the client should be highlighting (e.g. any risks associated with not knowing the accurate location of utility infrastructure)?
  • i) Are there any sections within the survey area where key information is needed and where the highest intensity of survey is to be undertaken?
  • j) Are there any health and safety issues, hazards or risks associated with this site (e.g. working on highways including road category/speed limits, ongoing construction activities, confined space entry requirements, industrial premises where there is a potential presence of asbestos)?
  • k)Is there other material relevant to the project (e.g. geological information)?
  • l) Has the suitability of the survey area for geophysical investigation been assessed?
  • m) What utility attributes need to be included in the deliverables?
  • n) What level of detail is to be recorded against accessed manholes, inspection chambers and pits, etc.?
  • o) Is post-processing of the data required?

4.1 Documentation

4.1.1 General

A method statement, programme of works, risk assessment and safety plan for the survey shall be submitted to the client before commencing work on-site.

4.1.2 Method statement

NOTE 1 Some clients might have their own templates for generic method statements which should be addressed in drafting the method statement.

NOTE 2 In planning the survey, the practitioner should consider the likely depth, size, duty and material of construction of the buried utilities within the survey area to ensure a survey is delivered that meets the client's requirements. An appraisal of the expected utilities and their complexity should be made by considering the type of site.

NOTE 3 Gaining access to utility assets such as manholes and inspection chambers and obtaining permission to do so is a contractual arrangement specific to a particular project.

A method statement shall be produced and submitted to the client and shall include as a minimum:

  • a) the survey type(s) to be deployed as specified in Table 1, including the estimated survey extent for each survey type;
  • b) for survey type B, detection methods to be deployed as specified in Table 2, including the estimated survey extent for each method;
  • c) comment on these survey type(s) and, for survey type B, detection methods, with regard to satisfying the client's requirements;
  • d) comment on the expected achievable quality level;
  • e) names and experience of the project team;

NOTE 4 Experience includes training, qualifications, previous project experience and evidence of competencies.

  • f) how traffic, pedestrians, parked vehicles, bus stops, skips, animals and other surface obstructions are to be managed to maximize the area available for survey and to ensure the safe execution of the works.

NOTE 5 Access to private land is to be negotiated and if work is required in the highway, any permissions will need to be sought from the appropriate highway authohty(ies).

NOTE 6 Before undertaking any excavation, evidence should be obtained that the following are in place:

  • a) permits;
  • b) licences;
  • c) footpath/road closure notices.

NOTE 7 It is usually the client who is responsible for procuring relevant permits, licences, footpath/ road closure notices. Attention is drawn to the New Roads and Street Works Act 1991 (NRSWA) [2] and the Traffic Management Act 2004 [4].

NOTE 8 Night time or weekend working should normally be agreed with the client to ensure safe and considerate impacts on the local environment and community.

4.1.3 Programme of works

A programme of works shall be drawn up detailing the time allowed for the fieldwork, initial reporting, client consultation, any agreed further fieldwork and submission of the deliverables.

NOTE The programme of works can take a variety of forms (schedule of work, spreadsheet, list of dates, etc.) appropriate to the project.

4.1.4 Risk assessment and safety plan

A site-specific risk assessment and safety plan or safe system of works shall be compiled.

NOTE The risk assessment involves:

  • an examination of the work and workplace to identify what could cause harm to people (a hazard). This should be developed by a site visit and/or current information supplied by the client;
  • an assessment of the chance, high or low, that somebody could be harmed by the hazards identified, together with an indication of how serious the harm could be (the risk).

The safety plan involves taking the results of the risk assessment and developing a plan showing the precautions needed to mitigate the risks and how these precautions wilt be communicated and implemented.

4.2 Utility records

4.2.1 For a survey type С, В or A, utility records shall be obtained through a desktop utility records search in accordance with Clause 6.

4.2.2 The desktop utility records search deliverable shall not be older than 90 days prior to conducting a survey type С, В or A.

4.3 Base mapping

Where existing base mapping has been obtained (in any format, e.g. drawing, electronic such as 3D-CAD/ GIS/BIM models), its accuracy, currency and scale shall be assessed for its intended purpose.

NOTE 1 This Subclause covers requirements for assessing base mapping as part of the planning process. Requirements for on-site checks are specified in 10.4.1.

NOTE 2 If there are any obvious omissions, inaccuracies or doubts about any inherited data, or if any data are considered unsuitable, the practitioner should inform the client that a new topographic survey will need to be undertaken.

NOTE 3 Where Ordnance Survey data is being used, the practitioner should obtain details of an Ordnance Survey licence from the client to include on drawings.

4.4 Other buried features and obstructions

NOTE This PAS does not cover the identification and mapping of other buried features or obstructions. If the client requires additional site investigation work this should be carried out in accordance with BS 5930.

If buried feature or obstructions are discovered whilst undertaking the works, they shall be reported in accordance with 11.6.

4.5 Geology of the site

NOTE 1 Any detection or verification methodologies to be used should take into account the geological bedrock, natural and artificial superficial deposits and geological structures beneath the site when known.

NOTE 2 When selecting the geophysical technique, the resolution as well as depth of penetration expected in the prevailing geological bedrock should be taken into account along with the variability within the geological subsurface which might exert a strong influence.

NOTE 3 When selecting the method of verification, the composition and physical properties of the geology should be taken into account.

4.6 Meetings and site visits

A post-fieldwork meeting shall be held to review the results in terms of the information delivered and any remaining areas of uncertainty, and to discuss whether additional fieldwork is required.

NOTE 1 The meeting may be a face-to-face meeting or a virtual meeting (telephone, video-conferencing, online).

NOTE 2 In addition to the post-fieldwork meeting, other meetings, site visits, client visits and progress reports might be required to inform the client on progress and resolve problems as they arise.

5 Quality level

5.1 Survey types

The survey type(s) shall be selected from the following:

  • a) survey type D – desktop utility records search;
  • b) survey type С – site reconnaissance;
  • c) survey type В – detection;
  • d) survey type A – verification.

NOTE 1 A survey type D is a prerequisite for survey types С, В and A (see 4.2.1). Survey types A to С are independent of each other. For example, a detection survey can conform to this PAS without the need to conduct a survey type С or A.

NOTE 2 The practitioner should establish with the client the survey type(s) required and where these are to be performed on the survey area.

NOTE 3 A client might specify multiple survey types over the survey area. For example, the client might require a survey type D for the whole site, a survey type В in the road carriageways and a survey type A only at a specific location where a potential design element has a possible conflict in a congested area.

NOTE 4 The practitioner should establish with the client the detection methodology required and document this in the method statement (see 4.1.2).

NOTE 5 Figure 1 illustrates the typical processes involved in delivering the different survey types and the assessment of the deliverables to determine whether further work is required.

5.2 Quality level

The quality level achieved shall be applied to each segment of utility surveyed in accordance with Table 1.

NOTE Survey type D can only be classified as QL-D in the deliverables. Survey type С can have utility segments that are classified as QL-C or QL-D in the deliverables. Survey type В can have utility segments that are classified as QL-B1, QL-B1P, QL-B2, QL-B2P, QL-B3, QL-B3P or QL-B4 in the deliverables. Survey type A can have utility segments that are classified as QL-A in the deliverables if utility(ies) are exposed/inspected and measured.

Figure 1 – PAS 128 process flowchart (informative)
Table 1 – Quality level of survey outputs (normative)
Survey type
(Establish with client prior to survey)
Quality level (Practitioner to determine post survey) Post-processing Location accuracy Supporting data
Horizontal 1) Vertical2)
D Desktop utility records search QL-D Undefined Undefined
С Site reconnaissance QL-C Undefined Undefined A segment of utility whose location is demonstrated by visual reference to street furniture, topographical features or evidence of previous street works (reinstatement scar).
В Detection3) QL-B4 No Undefined Undefined A utility segment which is suspected to exist but has not been detected and is therefore shown as an assumed route.
QL-B3 No ±500 mm Undefined (No reliable depth measurement possible) Horizontal location only of the utility detected by one of the geophysical techniques used.
QL-B3P Yes
QL-B2 No ±250 mm or ±40% of detected depth whichever is greater ±40% of detected depth Horizontal and vertical location of the utility detected by one of the geophysical techniques used.4)
QL-B2P Yes
QL-B1 No ±150 mm or ±15% of detected depth whichever is greater ±15% of detected depth Horizontal and vertical location of the utility detected by multiple5) geophysical techniques used.
QL-B1P Yes
A Verification QL-A ±50 mm ±25 mm Horizontal and vertical location of the top and/or bottom of the utility. Additional attribution is recorded as specified in 9.2.5.
1) Horizontal location is to the centreline of the utility.
2) Vertical location is to the top of the utility.
3) For detection, it is a requirement that a minimum of GPR and EML techniques are used (see
4) Electronic depth readings using EML equipment are not normally sufficient to achieve a QL-B2 or higher.
5) Some utilities can only be detected by one of the existing detection techniques. As a consequence, such utilities cannot be classified as a QL-B1.

6 Desktop utility records search (survey type D)

6.1 General

6.1.1 Survey type D shall use desktop search techniques to identify existing utility data within the survey area.

6.1.2 The quality level achieved shall be documented as QL-D in accordance with Table 1.

6.2 Methodology

6.2.1 A desktop utility records search shall be produced by the following process:

  • a) identify known utility owners within the specified survey area;
  • b) request asset information from identified utility owners;
  • c) collate all data on utility owners and their assets.

NOTE 1 The identification of utility owners and the request for asset information should be extended to land adjacent to the survey area, as this might offer an informative understanding of where utility feeds derive.

NOTE 2 When a project takes place on a private site, such as a hospital, industrial or military establishment, a utility owner might not have statutory records covering the survey area. Historical utility data should be obtained from the relevant estate's department, where available.

NOTE 3 A practitioner should allow adequate time within their schedule of work to receive the responses from utility owners. A 20-day period is recommended.

NOTE 4 Sources of information can include, for example, internet-based inquiry sites.

NOTE 5 The practitioner should consider asking the utility owner whether RFIDs have been used within the survey area.

NOTE 6 A desktop utility records search deliverable can be provided as a compilation and consolidation of all record data into a digital representation within a CAD/GIS/BIM model file structured to the client's requirements.

6.2.2 The information gathered shall include as a minimum:

  • a) company details of the practitioner carrying out survey type D;
  • b) client details;
  • c) a plan showing the boundary for the requested survey area;
  • d) a list of utility owners to whom a request was sent;
  • e) a list showing utility owner responses and actions taken to obtain response from non-responders;
  • f) any information received from the utility owner by way of plans, maps, diagrams or text and covering letter along with any asset guidance notes;
  • g) the date of issue of any maps supplied by the utility owners;
  • h) an advisory/cautionary note in BOLD explaining how this information was constructed, its limitations regarding accuracy and that no on-site survey/ geophysical detecting techniques have been used.

NOTE 1 A desktop utility records search deliverable older than 90 days should be classed as historical and used with caution. Attention is drawn to the New Roads and Street Works Act 1991 (NRSWA) [2].

NOTE 2 Where data have been supplied in imperial measurements this should be noted.

7 Site reconnaissance (survey type C)

7.1 General

7.1.1 Survey type С shall comprise a site reconnaissance to identify physical features that support the existence of utilities within the survey area.

7.1.2 Where the utility records can be matched to surface features, the quality level achieved shall be documented as QL-C in accordance with Table 1.

NOTE Where only one surface feature is identified relating to a specific utility, then the QL-C given for that segment will comprise a point on the utility. Where two or more surface features reference a specific utility, then the QL-C given for that segment will comprise a length on the utility

7.1.3 Where the utility records cannot be matched to surface features, the quality level achieved shall be documented as QL-D in accordance with Table 1.

7.2 Methodology

7.2.1 Site reconnaissance shall comprise on-site checks to validate the utility records and to assess if there are any conflicts that need to be resolved.

NOTE These might be records and drawings provided by utility owners obtained via a type D survey or might comprise historic drawings, records and digital data from other sources.

7.2.2 On-site checks shall document:

  • a) the presence, type and markings of utility-related surface features (see 7.2.3);
  • b) measurements between known surface features on the ground compared with those depicted on the plan;
  • c) differences between the map/drawing or digital features supplied and those extant on the ground.

NOTE Documentation of on-site checks may include, but are not limited to, the mark-up and annotation of existing plans, the inclusion of supporting photographic evidence and/or a written report.

7.2.3 Surface features to be included in the on-site checks shall include as a minimum:

  • a) manhole and inspection chamber covers;
  • b) valve covers;
  • c) utility markers;
  • d) control and distribution pillars and columns, LV power, street lighting, traffic lights; and
  • e) historic excavation scar lines.

PAS 128:2014 Specification for underground utility detection, verification and location