Design Memorandum



TO:                  All Design Section Staff

FROM:            Bijan Khaleghi
DATE:             February 28, 2007
SUBJECT:       Stamping/Signing Responsibilities for Special Design Retaining Walls


This design memorandum is to provide guidance on stamping and signing responsibilities for special design retaining walls, designed with input from the WSDOT HQ Geotechnical Division. Stamping and signing responsibilities for the different wall types are listed below:

  • Soil Nail Walls: These walls are primarily a geotechnical design exercise, with the Bridge and Structures Office detailing all the plan sheets, but providing the structural design only for the concrete fascia panels. The Bridge and Structures Office and HQ Geotechnical Division will co-stamp the soil nail layout plan sheets, which should include drainage details and any test nail details. The Bridge Office will stamp the plan sheets containing the concrete fascia panel details.

  • Geosynthetic Walls With Concrete Fascia (taller then 35-0): These walls are also a geotechnical design exercise, with the Bridge and Structures Office detailing the plan sheets and providing the structural design for just the concrete fascia panels. The Bridge and Structures Office and HQ Geotechnical Division will co-stamp the plan sheets containing the geosynthetic details. The Bridge and Structures Office will stamp the plan sheets containing the concrete fascia panel details.

  • Soldier Pile Walls With or Without Permanent Ground Anchors: The HQ Geotechnical Division supplies only the earth pressure diagram, a feasible anchor capacity and the length of the no-load zone. This information is supplied to the Bridge and Structures Office in the form of a stamped and signed report from HQ Geotechnical Division. For this type of wall, all the plan sheets are detailed, stamped and signed in the Bridge and Structures Office.

  • Slide or Slope Stabilization Using Retaining Walls: These walls, in most cases, are detailed in the Bridge and Structures Office but designed with input from both HQ Geotechnical Division and the Bridge and Structures Office. Examples would include secant pile, tangent pile, shear pile and cylinder pile walls. These plan sheets shall be co-stamped by the Bridge and Structures Office and HQ Geotechnical Division.

Exceptions to the cases described above may occur. Stamping and signing responsibilities for these exceptions will be determined on a case-by-case basis.


Background

While the PS&E for special design retaining walls is normally created in the Bridge and Structures Office, several of these wall types are actually designed as a collaborative effort between the Bridge and Structures Office and HQ Geotechnical Division. Recognizing the collaborative effort involved in creating these plan sets, stamping and signing practices needed to be clarified. Final arrangement of the details on the plan sheets should be done so as to keep the design, stamping and signing responsibilities separate between HQ Geotechnical Division and the Bridge and Structures Office.

The intent of the original Bridge and Structures Office Stamping and Signing Memo, dated 4/5/2000, shall remain in effect. For retaining wall types discussed above that are co-stamped by the Bridge and Structures Office and HQ Geotechnical Division, the stamp from the Bridge and Structures Office shall be structural-qualified.

If you have any questions regarding this issue, please contact Richard Zeldenrust at 705-7196 or Bijan Khaleghi at 705-7181.


cc:   Mohammad Sheikhizadeh, Bridge Construction - 47354

       F. Posner, Bridge and Structures 47340