Standard Interpretations - (Archived) Table of Contents|
April 18, 1995
MEMORANDUM FOR: ALL REGIONAL ADMINISTRATOR FROM: JOHN B. MILES, JR., Director Directorate of Compliance Programs SUBJECT: Safety Procedures for Work Performed in House Foundation ExcavationsThis is in response to requests for clarification on the application of Subpart P--Excavations, to house foundation excavations where property lines, adjacent structures, utilities, sidewalks, streets, curb/gutters, and similar obstructions preclude the excavation wall from being sloped or benched in accordance with the provisions of paragraph 1926.652(b).
Members of the Office of Construction and Maritime Compliance Assistance, Office of Construction and Engineering, the Office of Construction and Civil Engineering Safety standards and OSHA Field Staff, have researched this issue and have determined that compliance with the provisions of Subpart P during form work, installation of drainage systems surrounding a house foundation, application of waterproofing materials, and similar activities, is often infeasible when the obstructions listed above are present. Some alternatives were developed and set forth in the August 12, 1991 memorandum (copy attached) prepared by the Office of Construction and Engineering on this subject. In addition to those alternatives, the following solutions may also be used provided the following additional precautions are taken:
1) All spoil piles are maintained a safe distance away from the excavation (equal to or greater distance than depth),
2) Vehicles and other heavy loads are kept a safe distance away from the excavation (equal to or greater distance than depth) and employees are removed from the excavation when nearby traffic causes vibrations which can be felt when standing near the excavation, and
3) A competent person is present at all times while employees are exposed to cave-in hazards.
4) When rain or other wet conditions are anticipated or encountered (such as extensive hose use) the face of the excavation shall be waterproofed by the installation of polyethylene.
Although compliance with 1926.652(b) may be shown as being infeasible for this type of construction, all remaining requirements of Part 1926, Subpart P, still apply.
If you have any question concerning this memorandum, please contact Mr. Roy
Gurnham or Mr. Dale Cavanaugh of my staff in the Office of Construction and
Maritime Compliance Assistance at (202) 219-8136.
August 12, 1991
MEMORANDUM FOR: Byron R. Chadwick Regional Administrator THROUGH: Pat Clark, Director Compliance Programs FROM: Charles Culver, Director Office of Construction and Engineering SUBJECT: Worker Protection Doing Residential Basement Formwork in Excavation Near Property Line; Your Memo dated June 21, 1991, Same SubjectDr. Scott Jin of my staff looked at the problem described in the subject memorandum. First of all we commend your staff for the clear, concise statement of the problem. Unfortunately, our answer may be lacking in those qualities because we have no information of any system or equipment which is readily available to protect employees working between the foundation wall and the excavated ground.
Given this lack of knowledge Dr. Jin studied some possibilities that would meet the requirements of the Excavation Standard. His report is attached as Appendix A.
In Type A soil nominal compliance can be achieved by sloping as shown in Appendix A, Figure A-1 or in the standards as Figure B-1.1.3. If a fence or wall exists on the property line even this solution might be difficult to achieve practically but an employer could approach the required configuration thereby showing both a willingness to try to comply and in all probability preventing serious injury to any employee.
As you have noted the problem becomes much more difficult in Types B and C soil because there simply isn't room to slope inside the property line. Dr. Jin designed a shoring and bracing system which meets the criteria of the Trenching and Excavation Standard and the sketch of the system is included as Figure A-3 with sizing and spacing information contained in Table A-1.
This solution would be difficult to install if bedrock or boulders existed below the elevation of the footings and even in the best of conditions could add several thousands of dollars to the cost of a house but it can be used in most situations and the elements are reusable.
A second alternative would entail driving or pushing steel sheet piling to a depth and on a spacing shown for in Table A-2. The sheet piling would not require rakers or bracing and is also removable and reusable. This system would also entail significant costs when compared to the total cost of homes in most jurisdictions.
If a builder believes that he faces significant risks from damages if a slope failure encroaches on adjoining property there should be a strong economic incentive in addition to the possibility of death or serious injury to his employees to provide some type of support. In Type C soil the risk of a slide would be very great and should give even the most inept builder some pause for concern.
Other alternatives, which may prove less expensive than support could include re-siting the house on the available lot space, or acquiring a temporary easement on the adjoining property to allow proper sloping.
We would appreciate hearing of any other solutions that you might encounter.
(For Appendix A, see printed copy)
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