August 2007

At the June 2007 Regional Water Supply Project Committee, members were

informed that construction of the Shannon Creek dam had encountered:

“

Major

foundation issues – need to increase grouting to include 3 grout curtains instead

of one, and 2 blankets at significant extra cost."

Grout curtains are explained later.

One might ask how, in light of the extensive geotechnical investigations that were

undertaken, how this could possibly occur. However, there is a long history leading

to this moment which has a distinctly fishy smell.

The geotechnical aspects of the proposed Shannon Creek dam have always been a

source of concern to members of the Clarence Environment Centre and the Friends

of Shannon Creek Action Group Inc. (FOSCAG), following an assertion in 2001 by

an officer of the then Department of Land and Water Conservation that,

“the dam

will leak like a bloody sieve".

Three sites had been assessed prior to Shannon Creek being accepted as the preferred

option in 1997. However, the only comparative geotechnical work was three days

work with an auger and back hoe (undertaken between the 14th and 16th May 1997),

described as

“...limited geotechnical investigation, undertaken to enable estimation

of likely excavation depths for suitable dam foundations and provision of

information on likely available construction materials."

A single day's work at

each site which nobody could possibly claim constituted geotechnical investigations.

We maintain that site selection should have followed a full geotechnical assessment

of all sites. The above cost-saving course of action meant that simply didn't happen.

Typically crumbling Jurassic sandstone from the Shannon Creek escarpments. The

distance between the proposed high-water level of the 30,000ML Shannon Creek

dam, to the same level in the adjacent Black Swamp valley, is less than 30 0 metres.

GEOTECHNICAL INVESTIGATIONS SCANDAL

NEW PROBLEMS IDENTIFIED AT THE SHANNON CREEK DAM SITE