Hampshire County Council

Executive Member - Environment

10 September 2002

Project Appraisal: Land Management and Counter Pollution Works at Casbrook Common Closed Landfill Site

Report of the County Surveyor

Item 16

HAMPSHIRE COUNTY COUNCIL

EXECUTIVE MEMBER - ENVIRONMENT

PROJECT APPRAISAL

PROJECT:

LAND MANAGEMENT AND COUNTER POLLUTION WORKS AT CASBROOK COMMON CLOSED LANDFILL SITE

COMMENCEMENT DATE:

SEPTEMBER 2002

COMPLETION DATE:

2002/03

PLANNED YEAR OF START IN ACCORDANCE WITH CAPITAL PROGRAMME: 2002/03

1.

FINANCE (Client Department, Director of Property, Business and Regulatory Services [Estates Practice] and County Treasurer)

Current

Capital

Estimate

Programme

(at 2002

(at 2002

prices)

prices)

Capital Expenditure

£'000

£'000

Land to be purchased

Nil

Nil

Works

70

70

Fees

Nil

Nil

70

70

Less developers/

other contributions

Nil

Nil

70

70

Financial provision for total scheme

Total Cost

1.

From Committees own resources

(a) Capital programme (as above)

70

(b) Other

2.

From other resources

(a)

(b)

(c)

TOTAL

70

Value of land for this project in HCC ownership £

Variations from capital programme

Revenue implications

£'000

% variation

to Committee's

budget

Net current expenditure

Nil

Nil

Capital charges

Nil

Nil

TOTAL net expenditure

Nil

Nil

2.

STATEMENT OF NEED/JUSTIFICATION FOR PROJECT

(Client Department)

The County Council manages a number of closed landfill sites which were operated on the `dilute and disperse principles' and do not benefit from an Environment Agency (EA) waste management licence. In the absence of EA licensing the sites are managed by the County Council on a `self-policing' basis and priority action is judged by risk assessment and specialist consultancy advice.

The cornerstone of the management of the self-policing approach is the annual review of individual Site Management Plans. These reflect the aims of the Service Plan by considering the need to assess:

(i) potential for risk to human life and health;

(ii) actual and potential environmental impact;

(iii) any legal or EA requirement;

(iv) potential to cause loss and expense or nuisance to neighbours; and

(v) need for general land management.

The environmental status and general condition of the sites is constantly monitored through both environmental monitoring and visual inspection programmes. The Site Management Plans thoroughly review the interpretation of these programmes, provide commentary by a specialist landfill consultant and recommend actions and objectives for the following 12 month period.

This process is crucial to the management of landfill gas. Elevated landfill gas at site boundaries is a characteristic of dilute and disperse landfilling and the potential for off-site migration must be controlled. This is achieved at Casbrook Common using an active venting system. It is essential to keep this working to the optimum to ensure surface water run-off and settlement are not allowed to have an adverse impact. This necessitates good access at all times, good drainage characteristics and occasional reconditioning of the gas-well valve head security chambers.

The interpretation of the leachate impact of dilute and disperse landfill sites is a specialist task. Experience shows this is best approached on a step by step basis. The County Council has agreed with the EA to undertake a long term programme of leachate pollution control. The overtopping of the leachate interception trench is unacceptable and must be remedied. The monitoring of in-tip leachate levels is crucial to the long term mitigation measures and there is a need to provide good access for those undertaking monitoring activities.

Remedial and general site management works need to be viewed with after-use in mind. The objectives of this work are also aimed at maintaining the site in good order with, as far as practically possible, an annual hay cut.

This site has the potential for landfill gas utilisation. It is essential for good data to be acquired for the purposes of judging commercial viability and risk and the appropriate conditions of a service contract. The objectives of the works proposed in this appraisal will contribute to the effectiveness of the ongoing utilisation project investigation.

The proposed works are generally best undertaken when the ground water is at its lowest and not later than the end of the summer period to enable any grass reseeding to establish before the winter. Currently some tasks are driven by the needs of the pending landfill gas utilisation investigation.

The works identified in this project appraisal are in line with the recommendations of the current Casbrook Common Site Management Plan. There is a need to use capital funds, estimated at £70,000.

Some of the tasks are considered essential and some discretionary. There is a need to commence as soon as possible according to the weather and ground conditions.

The works will be wholly local fund resourced and are not eligible for Department for Environment, Food and Rural Affairs Contaminated Land Supplementary Credit Approval.

3.

IMPROVEMENT PROPOSAL (Client Department)

National/County network and policies

The works will meet the requirements of the Management of Health and Safety Regulations, support the County Council aim of Stewardship of the Environment and comply with the guidelines of Waste Management Paper 27 'Landfill Gas'.

Details of scheme and design standards

(i) Access track improvements; realign to improve turning and regrade to reduce steepness; improve surface and under drainage.

(ii) Infill some ditches with free draining material and perforated pipe, clay line some ditch inverts.

(iii) Refit gas-well valve head covers to new levels.

(iv) Infill some areas of settlement and reseed, repair rutted areas.

(v) Provide shallow clay bund to stream side of leachate interception drain over length where ground levels are lowest.

Environmental impact

The control of overtopping of the leachate interception drain will have immediate beneficial impact on the Casbrook Stream. Maintenance of the effectiveness of the landfill gas control system will have an impact on the control of the fugitive methane gas which is a significant ozone depleting substance (ODS).

Land requirements

All works will be carried out on land already in the County Council's control.

Statutory procedures

None required.

Public consultation

None required. The local Member, Councillor Woodall, has been consulted and his views are awaited.

Facilities for the disabled

Not applicable.

Maintenance implications

Ongoing general drainage clearance and landfill gas control system management, which is covered by the revenue expenditure programme on an annual basis.

Crime and Disorder Act 1998

The provisions of this Act have no impact on this proposal.

Sustainability

The control of ODS and enhancement of the agricultural and ecological status of the site will demonstrate support of sustainability issues. Work to improve the effectiveness of the landfill gas control system will assist progress towards the aims of producing renewable energy.

4.

ROAD IMPROVEMENT - ALTERNATIVES CONSIDERED

(Client Department)

None.

Section 100 D - Local Government Act 1972 - background papers

The following documents disclose facts or matters on which this report, or an important part of it, is based and has been relied upon to a material extent in the preparation of this report.

NB the list excludes:

1.

Published works.

2.

Documents which disclose exempt or confidential information as defined in the Act.

TITLE

LOCATION

None