Casing Hammering – a short (?) respite

Due to an obstruction the casing hammering did not take place on Saturday 8th July and, according to a CRD briefing note, has been postponed until later this week

Below is an extract from the CRD Briefing Note dated 7th July, 2017. 

170707 Casing Delay____________________________________________

As noted in our previous post the driving of the casing has been delayed; the briefing note confirms that an obstruction has been encountered. Our expert geologists have repeatedly warned of the risks associated with the tunnelled/drilled route; one of these being the presence of “glacial erratics“, large boulders transported across the Strait of Georgia during a previous ice age. An example of a glacial erratic can be seen at Harling Point near the Chinese Cemetery.  If one of these has been encountered the delay could be significantly longer!

To provide some background we’ll first briefly explain the casing/drilling process:

Casing2

 

  • A section of 60″ casing pipe is hammered into the ground at a 20 degree angle.
  • When the end of the pipe is driven close to grade, another section is welded onto the pipe (this takes a day).
  • The above steps are repeated until the casing pipe has passed through the fill material and reaches the undersea rock. Note that each additional section will face increased resistance and therefore require increased hammering.
  • The displaced fill material is then augered out from the inside of the casing pipe. The empty casing pipe will now provide a guide for the drill.
  • Drilling can now commence – starting with a pilot hole then, over the next 12 months, the hole size is gradually increased.

As noted in the CRD Briefing Note, on Thursday the casing pipe encountered an obstruction. The remedial process is:

  • Cut off any above grade protruding section of pipe to provide access the auger equipment (complete)
  • Auger out the fill from the 60″ casing pipe
  • Attempt to remove the obstruction
  • If  successful, weld on another casing section, resume hammering
  • If unsuccessful, options are limited as it will not be possible to drive the casing through the smaller diameter hole drilled through the boulder.

___________________________________________

The Briefing Note also states that:

we received a number of complaints from area residents regarding the noise generated by the activities occurring at the Ogden Point construction site

and

The sound wall is working to reduce the noise from the site to levels that are generally in accordance with the City of Victoria Noise By-Law, although we understand that it is still impacting residents in the area“. 

For “generally” read “exceeds”.  The figures provided by the CRD Project team indicate an average noise level of 100 dB at the top of the noise wall – a level which will  seriously affect those living in nearby apartment buildings (dB is a logarithmic scale hence the noise experienced by residents is more than four times the CRD commitment of 75 dBA)

Higher noise levels were recorded by several residents using hand held devices.  We have asked CRD to confirm that the average values listed in their Briefing Note refer only to the periods of hammering and are not an average of a longer period. This and previous posts will be updated when the noise meter logs have been made available.