Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
Following deposit of the waste the material is levelled and compacted and
intermediate inert cover materials placed over the top. Cover materials are currently
sourced on site and are primarily made up of waste clays from the mineral excavation
operations. Alternative cover materials are being investigated. Wastes are deposited
in controlled layers to ensure adequate compaction and minimise settlement.
Leachate forms in both open and capped cells as rainwater infiltrates through the cap,
if present, and the waste. Leachate levels are monitored through a series of boreholes
across the site, and excess leachate is removed by pumping. The leachate can be
managed by recirculation in Cells 1 and 2 but is otherwise removed by tanker for
treatment off site. The amount of leachate allowed to accumulate is regulated, with
trigger levels of 2 m head in the sumps and 1 m in the monitoring wells. The Annual
Monitoring Report for 2007 shows that these levels are maintained except during
periods of unusually high rainfall.
The “Kings Cliffe Landfill Site Annual Monitoring Report 2007” (ENRMF was
formerly known as Kingscliffe or Slipe Clay pit) reports that approximately
5000 tonnes of leachate were abstracted from the site during 2007 and transferred to a
disposal facility. The “Pollution Inventory reporting form” submitted to the
Environment Agency for the site reports 5402 tonnes of landfill leachate (EWC code
19 07 03) being discharged in 2007.
Leachate abstracted from the site is transferred by tanker to an off-site facility for
treatment and discharge. The current arrangement is for transfer to a biological
treatment plant at Avonmouth, discharge to trade effluent sewer and further treatment
at a water treatment plant. There are feasibility studies underway for use of an
alternative off-site facility and for construction of an on-site leachate treatment plant.
The closed cells are capped with a composite cap consisting of a gas drainage layer,
clay regulating layer, geotextile protector, geosynthetic clay liner, LDPE
geomembrane liner and soil cover.
There are lagoons on site that receive surface water that does not enter the disposal
cells. Water from one lagoon is used for dust suppression. After capping, surface
water will be directed to settling ponds and then discharged to a swallow hole
(northern slopes) or surface water (southern areas).
Following capping, the landfill site will enter a post closure managed stage. This stage
will include the maintenance of leachate levels and gas abstraction, and will continue
until it can be confirmed that the site no longer represents a significant risk of
pollution of the environment or harm to human health. Leachate, surface water and
groundwater quality will be monitored throughout the post closure managed stage.
2.1.2 Geology and hydrogeology
The regional geology comprises a sequence of Jurassic sedimentary rocks, including
limestones, clays and mudstones (Table 2.2). On higher ground, the Jurassic rocks
are overlain by Pleistocene glacial clays.
Galson Sciences Limited 6 14 July 2009
WS010001/ENRMF/CONSAPPCRF 556