Laneshaw IR Dam Stability
Laneshaw IR is located approximately 2km northeast of Laneshaw Bridge and approximately 5.5km northeast of Colne in East Lancashire.
A Toolbox Risk Assessment for internal seepage erosion concluded that the southern arm embankment needed remedial works to reduce the risk of internal erosion. The Client has a commitment to reduce the overall risk of failures of all reservoirs within their portfolio to less than 1.00 x 10-4 annual probability of failure.
The project comprised the design and construction of remedial works at Laneshaw Impounding Reservoir (IR); Construction of a filter blanket, toe drain and flow measurement chambers with V-notch weirs.
Installation of a full height filter blanket arrangement on the downstream face of the southern arm embankment from the primary spillway to the access steps on the western embankment.
Provision of an integrated toe drainage filter system sized to existing toe drainage requirements, and additional flows from the filter drainage blanket.
Provision of flow measurement manholes with V-notch weirs for the measurement of filter blanket and surface water run off flow at 40m intervals.
Collaborative assessment of the works information, to challenge it and identify VE opportunities.
An alternative material was proposed, which was 99% compliant with the specification, but which meant that there was no need to mix the aggregates on site. This presented both a cost saving and mitigated quality control risks associated with mixing on site.