Remedial works to upstream face rip-rap protection
Megget Reservoir, in the Borders region, and Scotland’s highest embankment dam, supplies some 64,000 Ml to Edinburgh and the surrounding Lothians area.
The 56m high by 570m long dam is a gravel filled embankment with a central asphaltic core. Since first filling in 1983, damage to the rip-rap protection on the upstream face occurred due to higher than predicted wind speeds and consequent wave attack.
East of Scotland Water contracted remedial pattern grouting of rip-rap from Hesselberg Hydro.
The most economic and practical solution
Full scale site trials prior to the award of the main contract demonstrated the increased strength of the rock layer while retaining adequate porosity
27,000 m2 upgraded with pattern grouting on a 2.5 metre grid
On site production of 10,500 tonnes of mastic
Full using made of mobile quality control laboratory
Mastic grout applied hot from specially designed skips, penetration relying on gravity
Completion was on time in October 1998, and within budget
Since completion, the upgraded rip-rap has performed very well over two winter periods which have included two severe wind events.
This was a pioneering project – the first successful demonstration of the technology both in the UK and for embankment dams.
“East of Scotland Water has benefited from Hesselberg Hydro’s [and MJ Gleeson’s] involvement in this project. Their practical experience in successfully pattern grouting sea defence works throughout Europe has added to our confidence in accepting this as a robust long term solution to the Megget problem.” Allan Shaw Engineering Design Manager of East of Scotland Water