1. GEOTECHNICAL CONSIDERATIONS IN CONSTRUCTION DEFECT LITIGATION
J. DAVID DEATHERAGE, P.E.
SENIOR GEOTECHNICAL ENGINEER-PRESIDENT
COPPER STATE ENGINEERING, INC.
MCBA PRESENTATION MARCH 24, 2011

2. STANDARD OF CARE
RULES OF THE ARIZONA STATE BOARD OF TECHNICAL REGISTRATION
Regulating: Architects; Assayers; Certified Remediation Specialists; Drug Laboratory Site Remediation Firms, Supervisors and Workers; Engineers; Geologists; Home Inspectors; Landscape Architects; and Surveyors.
Arizona Administrative Code - Title 4, Chapter 30
Effective March 8, 2008
ARTICLE 3. REGULATORY PROVISIONS
R Rules of Professional Conduct
All registrants shall comply with the following rules of professional conduct:
6. A registrant shall apply the technical knowledge and skill that would be applied by other qualified registrants who practice the same profession in the same area and at the same time.

3. GEOTECHNICAL INVESTIGATION STANDARD OF CARE
Scope considerations for geotechnical investigations include:
Type of project – residential, commercial, industrial
Anticipated foundation loading
Allowable foundation movements and acceptable level of risk
Site location, history of use and area extent
Prior experience with site
Number and depth of explorations

4. ARID REGIONS OF THE WORLD

5. ARID REGION PROBLEM SOILS
Expansive Soils - Definition
From the 2009 International Building Code, soils meeting all four of the following provisions shall be considered expansive, except that tests to show compliance with items 1, 2 and 3 shall not be required if the test prescribed in item 4 is conducted:
Plasticity index (PI) of 15 or greater.
More than 10% passing a No. 200 sieve.
More than 10% of the soil particles are less than 5 micrometers in size.
Expansion index greater than 20.

6. ARID REGION PROBLEM SOILS
Expansive soil classification by ASTM D a Expansion Index Potential Expansion Swell% 0-20 Very Low Low Medium High Greater than 130 Very High > 13.0

7. ARID REGION PROBLEM SOILS Expansion Index Test Setup

8. ARID REGION PROBLEM SOILS
Tucson Area Expansive Soils
Map Source National Resource
Conservation Service (NRCS)
Information Derived From
Testing of Upper 5 Feet of Soils

9. ARID REGION PROBLEM SOILS
NRCS Mapping of Phoenix Area Expansive Soils

10. ARID REGION PROBLEM SOILS
Collapsible Soil:
Classification of Collapse Index from ASTM D
Degree of collapse Collapse Index
None 0
Slight
Moderate
Moderately Severe
Severe greater than 10

11. ARID REGION PROBLEM SOILS Collapse Potential Test Setup

12. ARID REGION PROBLEM SOILS
Collapse Potential Testing Results

13. OTHER PROBLEM SOILS: Corrosive soils with elevated sulfate
Soils with excessive, corrosive or expansive salts
Saturated fine grained soils that consolidate over time due to increased loading
Soils that consolidate and fissure due to pumping and lowered groundwater table
Soils that are highly erodible and dispersive

14. PRE-CONSTRUCTION MITIGATION
Problem: Undercompacted low density fill
Mitigation:
Remove and replace with moisture conditioned and compacted engineered fill. A typical engineered fill specification includes use of a non-expansive predominately granular material that is compacted to 95% of Standard Proctor maximum dry density within a range of +/- 2% of optimum moisture content. Engineered fill is placed in controlled horizontal lifts less than 12 inches thick, and there is testing to confirm moisture conditioning and compaction by geotechnical engineer.
To Reduce Risk:
Remove portion of low density fill and live with risk of movement from remaining materials.
Improve drainage away from structures and eliminate moisture sources

15. PRE-CONSTRUCTION MITIGATION
Problem: Shallow Expansive Soils
Mitigation:
Remove and replace with non-expansive engineered fill soil (very effective)
Blend chemical lime slurry into expansive soil and compact as engineered fill (very effective for expansive soil without significant coarse material or elevated sulfate)
Design structural foundation and floor components to resist possible uplift
To Reduce Risk:
Control vegetation and moisture sources
Deepen foundations
Post-tension slab / additionally reinforced foundation
Limit compaction and add moisture, keep pad moist

16. PRE-CONSTRUCTION MITIGATION
Problem: Deeper Expansive Soils
Mitigation:
Design structural foundation and floor components to resist possible uplift
Design suspended floors and foundations to be supported on deep foundations such as steel H piles, helical piers or concrete piers. Extend deep foundations through expansive soils and bear on competent underlying materials. Consider uplift on piles and piers.
To Reduce Risk:
Limit compaction and add moisture, keep pad moist during construction
Control vegetation and moisture sources after construction

17. PRE-CONSTRUCTION MITIGATION
Problem: Collapsible Soils Near Surface
Mitigation:
Excavate, moisture condition and place back as engineered fill soil (very effective)
To Reduce Risk:
Excavate portion of total thickness, moisture condition and place back as engineered fill soil
Control vegetation and moisture sources
Deepen foundations
Post-tension slab / additionally reinforced foundation

18. PRE-CONSTRUCTION MITIGATION
Problem: Deeper and/or Thicker Strata of Collapsible Soils
Mitigation:
Design floors and foundations to be support on deep foundations such as steel H piles, helical piers or concrete piers. Extend deep foundations through collapsible soils and bear on competent underlying materials.
To Reduce Risk:
Partially treat upper soils and live with risk of movement.
Improve drainage away from structures and eliminate moisture sources

19. FORENSIC GEOTECHNICAL INVESTIGATION
Phase One – Visit site and observe distress. If distress is thought to be soil movement related, ask to be provided with the following information to review:
Original geotechnical report
Real estate disclosure report
Site compaction testing reporting
Civil grading and drainage design drawings
Structural design drawings for foundations
Landscape design drawings
Previous forensic testing and reporting

20. FORENSIC GEOTECHNICAL INVESTIGATION Phase Two – Manometer survey of interior floor slab elevation differences and measure exterior perimeter drainage grades

21. FORENSIC GEOTECHNICAL INVESTIGATION
Phase Three – Estimate magnitude of soils problem with additional site explorations as necessary:
Sample soils with borings and/or test pits
Investigate foundation geometry and depth
Investigate slab and/or asphalt thickness
Laboratory testing of selected samples
See photos of investigation examples:

22. DESIGN AND CONSTRUCTION DEFECTS
Copper State Engineering has worked more than one hundred litigation cases over the last 16 years where geotechnical related design and/or construction defects have been involved.
We have worked as geotechnical and civil engineer experts to represent owner plaintiffs and defendants, developer plaintiffs and defendants, contractor defendants and subcontractor third party defendants. Frequently we work directly for insurance or bonding companies.
Potential design and construction defects are identified based on site visit observations, information review and forensic geotechnical investigations.

23. DESIGN DEFECTS
Design defects that we have seen when there are geotechnical problems at a site have included:
Original geotechnical engineer fails to identify soil problems at a site by not meeting the standard of care.
Architect or Engineer bases foundation designs on assumed soil conditions without discussing risk with owner and/or without giving owner the opportunity to have a geotechnical investigation performed.
Architect or Engineer is provided with a geotechnical report for the site and chooses to ignore portions of the geotechnical recommendations in the design of the site.

24. DESIGN DEFECTS Examples of design defects include:
Architect or Engineer specifying site drainage features and/or site drainage grades that do not comply with geotechnical report recommendations.
Architect or Engineer specifying slab and/or foundation systems that do not comply with geotechnical report recommendations.
Architect or Engineer specifying asphalt or concrete pavement sections that do not comply with geotechnical report recommendations.
Architect or Engineer specifying retaining wall designs that do not comply with geotechnical report recommendations.

25. CONSTRUCTION DEFECTS
The Arizona Registrar of Contractors publishes Workmanship Standards for Licensed Contractors. These standards provide guidance on performance of construction related items during the first two years of ownership.
Other sources of standards for evaluation of excessive distress include the National Association of Home builders.
See examples of distress observed in Arizona construction in the following photos:

26. POST-CONSTRUCTION MITIGATION
Once the forensic geotechnical investigation identifies the type and magnitude of soils problem at a site, mitigation construction to reduce future distress can be considered.
In some cases soils related movement can take months or even years to stabilize after mitigation construction is complete, depending on the type and magnitude of the soils problem. Risks of additional movement and distress can remain after mitigation construction. Frequently, aesthetic repairs should be postponed until soil movements can be shown to stabilize. Repeating manometer surveys and monitoring of distress can be used to monitor the progress of the mitigation construction.
All parties to the mitigation construction must understand the risks associated with the mitigation, and frequently there will be duty to disclose the original soils problem, mitigation and remaining risks to future owners.

27. POST-CONSTRUCTION MITIGATION
Methods to mitigate low density fill soils under existing construction can include:
Removal and replacement of problem fill where possible.
Underpin with concrete or steel piers to carry foundation and floor loads through problem fill and into competent underlying materials.
To Reduce Risk:
Treat low density fill with chemical or compaction grouting
Mudjack with low pressure grout to fill voids and re-level concrete slabs
Underpin with concrete or steel piers to carry foundation loads through problem fill and into competent underlying materials.
Improve drainage away from structures and eliminate vegetation and moisture sources

28. POST-CONSTRUCTION MITIGATION
Methods to mitigate collapsible soils under existing construction can include:
Underpinning with concrete or steel piers to carry foundation and floor loads through collapsible soils and into competent underlying materials
To Reduce Risk:
Treat low density fill with compaction grouting
Mudjack with low pressure grout to fill voids and re-level concrete slabs
Underpin with concrete or steel piers to carry foundation loads through problem fill and into competent underlying materials.
Improve drainage away from structures and eliminate moisture sources

29. POST-CONSTRUCTION MITIGATION
Methods to reduce the risk of expansive soils under existing construction:
Construct a geomembrane cutoff wall around the perimeter of the structure to reduce moisture changes
Underpin with concrete or steel piers to carry foundation loads through expansive soils and into competent underlying materials, consider possible uplift loads
Improve drainage away from structures and eliminate vegetation and moisture change sources
Chemically grout expansive soils to reduce expansion potential (effectiveness in question at this time)

30. PHOTOS OF MITIGATION

31. CLOSING
This presentation is based on the experience of J. David Deatherage, Registered Arizona professional civil engineer, including work on more than 3000 projects and more than 30 years of geotechnical engineering experience in the southwest.
Please note that while the provided generalizations will be valid for most situations in the arid regions of the southwest, they will not be valid for all situations.
There are legitimate differences of opinion between experts in the geotechnical community regarding some of these generalizations.