Review of UK Marine Aggregate Extraction Activities

Posted on 25th May 0209 in Marine Aggregate Dredging

From The Crown Estate and BMAPA showing historic patterns of marine aggregate extraction in metric tonnes for 2000-2005, excluding beach replenishment and fill contracts.

Extraction Area	2000	2001	2002	2003	2004	2005	Total
Humber	3,122,080	2,933,623	2,710,881	2,928,366	3,031,699	3,392,015	18,118,664
E Coast	9,129,635	9,636,697	9,011,323	8,611,199	8,538,073	7,881,670	52,808,597
Thames	854,483	909,141	1,291,103	838,185	758,257	696,012	5,347,181
S Coast	5,613,538	5,628,008	5,399,080	5,658,262	5,148,959	5,389,346	32,837,193
SW Coast	1,602,394	1,549,431	1,467,122	1,515,241	1,633,383	1,591,610	9,359,181
NW Coast	316,090	421,068	482,270	470,962	558,398	611,983	2,860,771
Rivers & Misc	46,120	73,047	78,597	85,153	99,079	124,506	506,502
Yearly Total	20,684,340-	21,151,015-	20,440,376-	20,107,368-	19,767,848-	19,687,142-	121,838,089

According to moisture content and stone to sand ratio, there’s usually between 1.6 and 1.9 metric tonnes weight for each cubic metre of aggregate. That related to uses a dry weight ratio of 1.72:1. Therefore, the six year total take of 121,838,089 tonnes would mean a removal of 70,836,052 cubic metres. The level given is undoubtedly that landed to destination. In practice over twice this would have been extracted as some half is rejected by washing off back to the sea so as to hold the prime coarse cohesive sand and gravel to be used for the best grade concrete.

Such a quantity is difficult to visualise, but can be estimated by theoretically placing it on top of a town or city of a known area. (Don’t try this in practice unless you can chose Westminster) and calculating how high it would reach, or how many times it would fill the Albert Hall.

It is interesting to note that the findings of erosion of each area correlate quite powerfully with the levels taken, as does the lowering of the seabed when related to the cumulative active dredging areas.