January 23, 1995

TO: C. C. Ruth

FROM: T. L. Nelson/J. A. Weigel

SUBJECT: Drilled Shaft Foundations

As you are aware, a joint task force mandate was agreed upon during our December 16, 1994 meeting to study and possibly improve the WSDOT Drilled Shaft Special Provision. This task force will be comprised of Association of Drilled Shaft Contractors (ADSC) and Washington State Department Of Transportation (WSDOT) representatives. Mr. M. B. Murphy and I will be getting together shortly to set up the first task force meeting.

In the mean time, considering the extraordinary and large problems being encountered on most of our drilled shaft activities, I am requesting that the use of drilled shaft foundations not be specified if there is any other acceptable foundation system. I understand that a drilled shaft foundation system bid price is often less than other systems. But the reality is with extra costs encountered with drilled shaft construction; for instance, removal of obstructions, the final cost for drilled shafts is usually much higher than the original bid amount. Whereas, pile foundations costs do not, as a general rule, escalate during the contract period.

Since my cost statements are extremely general, I thought I could use specific project data to emphasize my point. I requested and received the shaft cost data for the Black Lake Blvd. Interchange and Black Lake Blvd. To SR 5 project, Contract No. 4272. This may not be a typical project but it dramatically emphasized my point. The interior piers of the Percival Creek Bridges are supported by drilled shafts. There are eight shafts with diameters of 8’-6", 9’-0". All the shafts except one have been completed as of the date on the Memorandum. The accumulated cost data shown on page two indicated an overall cost increase of $349,536.67 or a 95% cost increase. The $124,416.23 change order cost increase was due to plan errors and not applicable to this subject matter. The 62% cost increase that could be considered typical for a drilled shaft project. These obstruction removal costs are not included in the project bid price but are usually encountered during the construction of drilled shafts. This specific cost increase percentage is for this one specific project and will vary with each project.

Following is the project cost data breakdown:

Item Description Cost Accumulated Cost

Bid Price for Eight Drilled Shafts $365,787.50

Obstruction Removal Subtotal $225,120.44 $590,907.94

Change Orders $124,416.23

TOTAL $715,324.17

TLN/JAW