Westminster SEMP Guide

What is a Westminster Site Environmental Management Plan (SEMP)?

A Site Environmental Management Plan (SEMP) is the document Westminster City Council requires for Level 1 and Level 2 projects to demonstrate how demolition and construction impacts will be managed in accordance with the Code of Construction Practice.

It brings together the project’s construction methodology, site management arrangements, traffic and logistics controls, environmental mitigation, monitoring requirements and community liaison procedures into a coordinated construction-phase management document.

The SEMP is submitted alongside the relevant Appendix A checklist and is reviewed by Westminster’s Environmental Sciences and Highways teams before the associated pre-commencement planning condition can be discharged.

When is a SEMP Required in Westminster?

Westminster’s Code of Construction Practice categorises projects according to their scale and potential construction impacts.

Level 1 Projects

Level 1 generally applies to large or strategic developments involving 100 or more new or additional residential units, or 10,000 square metres or more of Gross Internal Area created or subject to a change of use.

Level 1 projects require a SEMP and are subject to the most extensive construction management, consultation, environmental monitoring and community liaison requirements.

Level 2 Projects

Level 2 generally applies to developments involving 10 or more new residential units, or 1,000 square metres or more of Gross Internal Area created or subject to a change of use.

Projects below these thresholds can also be upgraded to Level 2 where their likely impacts, location, duration or proximity to sensitive receptors justify a higher level of control.

Level 3 Projects

Level 3 generally applies to developments that are not Level 1 or Level 2 but involve the construction of a new basement or extension of an existing basement.

Level 3 projects do not normally require a SEMP. They require a Construction Management Plan (CMP) prepared in accordance with Westminster’s Code of Construction Practice.

Level 4 Projects

Level 4 covers projects falling outside the Level 1, Level 2 and Level 3 definitions. These projects are generally not required to submit a SEMP or CMP for formal approval, although they remain expected to follow the principles of the Code of Construction Practice and comply with relevant environmental legislation.

Westminster can upgrade a project where its likely impacts, sensitive location or particular construction risks justify a higher classification.

SEMP or CMP – What is the Difference?

The document required depends on the Westminster Code of Construction Practice project level:

• Level 1: Site Environmental Management Plan (SEMP) + Appendix A / Checklist A

• Level 2: Site Environmental Management Plan (SEMP) + Appendix A / Checklist A

• Level 3: Construction Management Plan (CMP) + Appendix A / Checklist B

• Level 4: generally no formal SEMP or CMP unless the project is upgraded

Although the document titles differ, both the SEMP and CMP are intended to demonstrate how the construction works will be planned and controlled. The level of detail and supporting requirements vary according to the project classification.

For Level 3 basement projects in particular, the CMP remains a substantial document addressing construction logistics, highways, environmental controls and neighbour liaison, but some of the more intensive Level 1 and Level 2 monitoring requirements do not normally apply unless specifically requested by Westminster.

Appendix A, Checklist A and Checklist B

A Westminster SEMP or CMP is not submitted in isolation. The relevant Appendix A checklist forms an important part of the Code of Construction Practice approval process.

Checklist A – Level 1 and Level 2

Checklist A accompanies Level 1 and Level 2 SEMP submissions. It identifies the information Westminster expects to be addressed and confirms the developer’s commitment to comply with the Code of Construction Practice.

The checklist covers matters including general site information, programme and methodology, neighbourhood liaison, traffic and highways management, sensitive receptors, noise and vibration, dust and air quality, environmental monitoring, waste management and Section 61 Prior Consent.

Checklist B – Level 3

Checklist B accompanies the Construction Management Plan for Level 3 projects. It confirms the information required within the CMP and the developer’s agreement to comply with the relevant Code of Construction Practice requirements.

The relevant checklist must ultimately be countersigned by Westminster’s CoCP Coordination Officer before it is used to support formal discharge of the planning condition.

What Does a Westminster SEMP Need to Include?

A Westminster SEMP is a multidisciplinary construction-management document. The exact content must reflect the project, its location and the Code of Construction Practice requirements, but typical areas include:

Project and Site Management

The SEMP should establish the construction programme, proposed working hours, demolition and construction methodologies, site layout, storage areas, environmental management structure, responsibilities and arrangements for managing contractors and subcontractors.

Traffic, Transport and Highway Management

Every SEMP and CMP must include a Traffic Management Plan. This can require construction vehicle routes, access and egress arrangements, delivery vehicle information, loading arrangements, swept path analysis, pedestrian and cycle management, traffic-marshalling arrangements, highway occupation, parking suspensions and proposed road closures.

Particular attention is required where the site is close to schools, cycle routes or other vulnerable road-user locations.

Neighbour and Community Liaison

The SEMP must explain how neighbours and other potentially affected stakeholders will be informed and consulted before and during the works.

This can include resident and business notifications, dedicated contact arrangements, complaints procedures, newsletters, community meetings and ongoing communication throughout construction.

Noise and Vibration

A site-specific Noise and Vibration Management Plan forms part of the SEMP. For Level 1 and Level 2 projects, Westminster requires baseline noise information, assessment of construction noise and vibration risks, appropriate Best Practicable Means, predictions for key construction phases and monitoring arrangements.

The methodology should address the proposed plant, construction activities, sensitive receptors, working hours, mitigation measures, trigger and action levels, complaints and procedures for responding to exceedances.

Dust and Air Quality

A site-specific Air Quality Dust Management Plan (AQDMP) forms part of the SEMP or CMP. It must explain how construction dust and emissions will be assessed, controlled, monitored and reported.

For Level 1 and Level 2 projects, the requirements include dust-risk assessment and continuous PM10 and PM2.5 monitoring, with trigger and action levels and procedures for responding to exceedances.

Waste and Materials

The SEMP must address construction waste, material storage, segregation, reuse, recycling and disposal arrangements. Where required, this is supported by a Site Waste Management Plan and project-specific waste controls.

Water, Pollution Prevention and Ecology

Where relevant to the project, the SEMP should also address water management, pollution prevention, fuel and chemical storage, drainage, ecology, tree protection and other environmental constraints identified through the planning process.

Westminster SEMP Consultation Requirements

Consultation is an important part of the Westminster Code of Construction Practice process.

Potentially affected stakeholders must be engaged a minimum of three weeks before the SEMP or CMP is submitted to Westminster for review. This can include nearby residents, businesses, amenity groups, neighbourhood forums, Business Improvement Districts and other parties likely to be affected by the proposed works.

The consultation should explain the nature and duration of the works, important programme stages, likely construction impacts and appropriate project contact details.

Feedback should be recorded and, where practicable, reasonable measures should be incorporated into the final SEMP or CMP to address issues raised through consultation.

When Should a Westminster SEMP Be Submitted?

Westminster requires the SEMP and Appendix A to be submitted to the Council at least 40 working days before construction is scheduled to commence.

This lead-in should be considered alongside the requirement for pre-submission neighbour consultation and the preparation of supporting technical information.

The Council’s Environmental Sciences and Highways officers review the submission and can request amendments before the SEMP is approved. The relevant Appendix A is then countersigned and used to support discharge of the pre-commencement planning condition.

Construction must not commence until the relevant approvals and planning-condition discharge are in place.

Does a Westminster SEMP Require a Section 61 Application?

Yes. Under Westminster’s May 2026 Code of Construction Practice, Level 1 and Level 2 projects must apply for and obtain Prior Consent under Section 61 of the Control of Pollution Act 1974.

The Section 61 process is separate from the SEMP approval process. Submission or approval of the SEMP does not replace the requirement to obtain the appropriate Section 61 Prior Consent.

The Section 61 application must be submitted at least 28 days before commencement and requires information including proposed working hours, construction activities, plant and equipment, baseline noise information, predicted construction-noise levels, mitigation measures, monitoring arrangements and complaints procedures.

The technical information prepared for the SEMP Noise and Vibration Management Plan and the Section 61 application therefore needs to be coordinated so that the documents are consistent.

What About Level 3 Projects?

Level 3 projects generally do not require Section 61 Prior Consent unless noisy works are proposed outside Westminster’s standard working hours. The Code states that Level 3 contractors without a Section 61 consent will be issued a Section 60 notice before works commence.

Construction Noise Assessment and Baseline Monitoring

Level 1 and Level 2 projects are required to establish baseline noise conditions and predict construction noise from proposed activities.

The assessment uses information about the proposed construction methodologies, plant and equipment, operating periods and sensitive receptors to predict likely construction-noise levels and identify suitable mitigation measures.

These predictions support both the Noise and Vibration Management Plan and the Section 61 Prior Consent application.

Level 1 and Level 2 projects are also generally required to undertake continuous noise and vibration monitoring with appropriate trigger and action thresholds and to make monitoring information available to Westminster in accordance with the Code.

Air Quality Dust Management and Monitoring

The Air Quality Dust Management Plan is another important component of the Westminster SEMP package.

It should identify potential dust-sensitive receptors, assess the risk associated with demolition and construction activities and establish the mitigation measures, monitoring procedures and responsibilities required to manage dust and emissions.

For Level 1 and Level 2 projects, Westminster requires continuous PM10 and PM2.5 monitoring with a real-time alarm system, subject to project-specific agreement with the Council.

The SEMP, AQDMP and construction methodology therefore need to be developed together so that the environmental controls reflect how the works will actually be undertaken.

The Westminster SEMP Approval Process

Confirm the Project Level

Establish whether the development is classified as Level 1, Level 2, Level 3 or Level 4 under the Code of Construction Practice and confirm whether a SEMP or CMP is required.

Assemble the Construction Information

Gather the programme, methodology, site layout, construction logistics, plant information, environmental information and contractor details required to prepare the submission.

Prepare the SEMP and Supporting Documents

Prepare the SEMP together with the relevant Traffic Management Plan, noise and vibration information, AQDMP and other project-specific supporting documentation.

Consult Neighbours and Stakeholders

Undertake the required pre-submission consultation a minimum of three weeks before the SEMP is submitted and incorporate relevant outcomes into the final document.

Submit the SEMP and Appendix A

Submit the completed SEMP and Checklist A to Westminster at least 40 working days before the proposed commencement of works.

Obtain Section 61 Prior Consent

For Level 1 and Level 2 projects, coordinate and submit the separate Section 61 Prior Consent application at least 28 days before commencement.

Respond to Westminster Comments

Environmental Sciences and Highways officers review the submission and may request clarification or amendments before approval.

Countersign Appendix A and Discharge the Condition

Once Westminster is satisfied, the relevant Appendix A can be countersigned and the approved documentation used to support formal discharge of the planning condition.

Can a SEMP Be Prepared Before a Principal Contractor Is Appointed?

The Westminster Code states that a draft SEMP is not required as part of the planning application and that a planning-stage draft is not a substitute for the full and final version required with Appendix A.

In practice, preparation of the final SEMP requires detailed construction information. Where a Principal Contractor has not yet been appointed, available design and programme information can be reviewed to identify the outstanding construction inputs needed before the formal submission is completed.

Early preparation can therefore be useful, but the final document should accurately reflect the contractor’s proposed methodology, programme, logistics, plant and environmental controls before it is submitted for approval.

How Seneca Services Can Assist

Seneca Services prepares Westminster Site Environmental Management Plans and Construction Management Plans for developers, architects, planning consultants and contractors.

We review the planning condition and project classification, identify the applicable Code of Construction Practice requirements and coordinate the construction, traffic, environmental and consultation information needed for the submission.

Depending on the project, our involvement can include:

• Westminster SEMP preparation

• Westminster CMP preparation

• Appendix A / Checklist A or Checklist B coordination

• neighbour and stakeholder consultation

• Traffic Management Plans and construction logistics drawings

• Air Quality Dust Management Plans

• Construction Noise Assessments and noise predictions

• Section 61 Prior Consent applications

• coordination of monitoring and supporting technical requirements

• updates following Westminster review comments

The objective is to produce a coordinated submission in which the SEMP or CMP, consultation, construction logistics and environmental documentation all describe the same proposed construction methodology and controls.

Frequently Asked Questions

Do all Westminster construction projects need a SEMP?

No. Westminster requires a SEMP for Level 1 and Level 2 projects. Level 3 projects normally require a Construction Management Plan instead, while Level 4 projects generally do not require formal SEMP or CMP approval unless the Council upgrades the project.

Do basement projects need a SEMP?

Not necessarily. A basement project that does not meet the Level 1 or Level 2 thresholds will generally be classified as Level 3 and require a CMP rather than a SEMP. A basement project can, however, fall within Level 1 or Level 2 or be upgraded where its scale or likely impacts justify a higher classification.

What is Appendix A?

Appendix A is the Westminster Code of Construction Practice compliance document that accompanies the SEMP or CMP. Level 1 and Level 2 projects use Checklist A, while Level 3 projects use Checklist B.

How long does SEMP approval take?

Westminster requires the SEMP and Appendix A to be submitted at least 40 working days before works are scheduled to start. Additional time should be allowed beforehand for preparation of the documentation and the required pre-submission consultation.

Is neighbour consultation required?

Yes. Potentially affected stakeholders must be engaged at least three weeks before the SEMP or CMP is submitted to Westminster for review. Consultation feedback should be recorded and relevant mitigation incorporated where practicable.

Does a SEMP include construction traffic management?

Yes. Westminster requires every SEMP and CMP to include a Traffic Management Plan addressing the construction traffic, access, delivery and highway-management arrangements relevant to the project.

Does a Westminster SEMP require a Section 61?

For Level 1 and Level 2 projects, yes. Westminster requires a separate Section 61 Prior Consent application. The SEMP does not replace that process.

Does a Westminster SEMP require an AQDMP?

Yes. Westminster requires a site-specific Air Quality Dust Management Plan to form part of the SEMP or CMP. The precise risk-assessment and monitoring requirements depend on the project level and circumstances.

Is continuous environmental monitoring required?

For Level 1 and Level 2 projects, Westminster generally requires continuous noise, vibration and particulate monitoring, together with agreed trigger and action levels and access to monitoring data. Requirements for Level 3 projects are generally less extensive and should be confirmed for the individual project.

When can construction start?

Construction should not commence until the SEMP or CMP has been approved where required, Appendix A has been appropriately countersigned, the relevant pre-commencement planning condition has been discharged and any separate consents required for the works are in place.

Need Help With a Westminster SEMP?

If your planning permission requires compliance with Westminster’s Code of Construction Practice, we can review the condition and project information, confirm whether a SEMP or CMP is required and identify the supporting consultation, environmental and construction-management documentation needed.