1. Excerpts from actual PMI Evaluations
“Works well when under constant supervision and cornered like a rat in a trap.”
“His men would follow him anywhere, but only out of morbid curiosity.”
“When she opens her mouth, it is only to change feet.”
“He doesn’t have ulcers, but he is a carrier.”
“If you see two people talking and one looks bored, he’s the other one.”

2. Pipe Trench Preparation and Backfill History
They built this when labor was cheap!
Workers excavate a culvert at the circa-2725 B.C. site of the Harappa settlement in Pakistan (file photo). PHOTOGRAPH BY RANDY OLSON, NATIONAL GEOGRAPHIC

3. 1997 STUDY Objective Justin F. Lundvall and John P. Turner, Ph.D, P.E.
65 page report
Objective
To identify the likely causes of settlement and roadway damage at culverts sites on Wyoming highways
A little bit of history

4. Field Investigation
WYO Medicine Bow to Casper (47-55)– Settlement within the first year of construction in Prior to 1992 no extensive maintenance had been required since 1956 – maintenance foreman
WYO 70 - Baggs– Encampment (2-4)
WYO Pine Haven Road(0-4)
Various locations in District 5

5. What did they want to accomplish with this study?
Determine if roadway settlement appears to be related to culvert or pipe characteristics, geological environment, construction practices, or other factors.
Establish the mechanism(s) of settlement, for example, compression settlement of fill around and above culverts and pipes under traffic loads, settlement of soil beneath culverts and pipes, deformation of the culverts and pipes, or some combination of causes.
Evaluate design and/or construction procedures to prevent or minimize roadway settlement.

6. Probable Causes of Settlement
Inadequate compaction of backfill around and above culverts due to lack of inspection.
Low cover from the top of the pipe to the surfacing
The use of poor material for backfill (plastic, compressible soils)

7. 1997 study recommendations to reduce settlement
Use high quality granular materials compacted to a high density for backfilling culverts
Avoid the use of highly plastic, compressible fine-grained soils
Use a controlled low strength materials (CLSM), commonly referred to as flowable fill, for backfilling culverts

8. What did we do with the recommendations from the 1997 final report?

9. 2006 FHWA Directive - from the federal HWY Bill
From 2006 and 2007 Memos
“State DOT’s should develop culvert selection policies that consider all available pipe products judged to be of satisfactory quality and equally acceptable on the basis of engineering and economic analyses.”
“Division Offices should now be working with their respective State DOT’s to ensure that the State’s culvert material selection procedures provide for competition with respect to the specification of alternative types of culvert pipes. Division Offices should ensure that the State’s procedures are based on sound engineering and economic reasons and not based on arbitrary factors.”
“With the potential for significant savings, the implementation schedule should not be based on protracted (drawn-out) evaluation periods for experimental or pilot project installations.”
Excerpts from FWHA memos. While not specifically stated, it is clear that the above policy is intended to ensure that thermoplastic pipes are being considered in the appropriate applications.
The policy is intended to ensure plastic pipes are being considered for use.

10. 2012 Study Objective
To provide the WYDOT Culvert Committee with all of the tools and information they need to draft a policy on culvert selection that satisfies the FHWA directive while also meeting the needs of WYDOT. The policy must be based on rational consideration of costs, performance, engineering design practice for culverts, constructability, and quality.
163 page report

11. 2012 Study Benefits
will allow the Wyoming DOT to satisfy the FHWA directive
develop culvert selection policies that consider all available pipe products, in a manner that provides fair competition and which is consistent with acceptable engineering practice.
will provide WYDOT with higher quality and more cost-effective culvert installations.
The cost effectiveness is still to be determined. The initial cost of installation will increase. Public perception will be better if a newly constructed road does not fail.

12. The final report included recommendations for:
Maximum Fill Height
Minimum Fill Height
Bedding and Backfill
Compaction
CLSM (controlled low-strength material)
Trench Width
Embankment Construction
Pipe Foundation / Bedding Thickness
Haunch
Backfill Lift Thickness
Corrosion
Abrasion
Joints
End treatments
Allowable Pipe Diameter
Deflection Testing and Inspection

13. What needs Revised?
Section 206 – Excavation and Backfill for Culverts – spec book
Section 603 – Culverts and Storm Drains – spec book
Section 800 – Materials – spec book
Section 603 of the Standard Plans
They stuck the new guy with doing the presentation

14. Culvert Selection and Backfill Committee Members
Bill Wilson, P.E. – Standards Engineer – chair of the committee
Andy Long, P.E. – State Construction Engineer
Charlie Bauer, P.E. – Construction Staff Engineer
Mark Falk, P.G. – Assistant State Geologist
Mike Menghini, P.E. – Assistant State Bridge Engineer
Chris Romo, P.E. – Materials Engineer
Mark Boushelle – FHWA, Pavement and Structures Engineer
Janis Kotlark – Administrative Assistant
Don Fuller, P.E. – Retired Resident Engineer – replaced by Ralph Tarango
OTHER CONTRIBUTERS
WCA
CONTECH ENGINEERING SOLUTIONS
PRINSCO
TrueNorth Steel
Plastic Pipe Industry

15. Please note that these proposed changes are a draft
Please note that these proposed changes are a draft. There are still changes to be made.
Reference the proposed Typical Pipe Installation Embankment Details as I go through the specification changes.

16. SECTION 206 Excavation and Backfill for culverts
New reference section
Add Vertical limits to account for pipe bedding material.

17. SECTION 206 Excavation and Backfill for culverts
This is a new subsection
Horizontal Limits – 2012 Study
AASHTO (2010a) only makes recommended embankment widths for concrete pipe that is equal to three times the outside pipe diameter. Although this limit appears to be within reason for concrete pipe, it may not be suitable for flexible pipe. It is recommended WYDOT implements a tentative minimum embankment width equal to five times the pipe diameter for all pipe materials.
Vertical Limits
Up to spring line
This section is also for box culverts which does not always required select backfill material

18. Select bedding and backfill material – Typical Pipe Installation Detail
The type of backfill and the manner in which it is installed is one of the most important considerations when installing pipe
The soil envelope must be able to develop high shear strengths in order to resist lateral pressure induced by vertical loads.
granular, coarse-grained soils with little to no fines typically develop greater shear strength
Gradation recommended by final report
Max PI of 6
May have to re-evaluate the gradation requirements

19. Report Recommendations
Include a min. air content equal to 6%
Include a max slump of 10 inches
Add a statement requiring CLSM to set for a minimum of 24 hours prior to allowing vehicle loads to travel over the fill
Add a statement requiring the contractor to submit mix designs a minimum of 30 days prior to installation for review
Add a statement requiring the contractor to provide a “delivery” ticket along with each batch of CLSM. The ticket should provide information such as the project designation, date, time, compressive strength, yield and unit weight, and flowability.
Why not fly ash?
fly ash can result in higher than anticipated compressive strengths, greater susceptibility to frost heave, and increased corrosion rates when used for metal pipes.

21. SECTION 603 Culverts and Storm Drains

23. From 2012 Study
“results from DOT surveys show there is a learning curve for contractors. Therefore, it is recommended that implementation occurs first through use of pilot projects. Interim specifications should be implemented which do not allow the use of plastic pipe in the following locations:”
We are taking the conservative approach.

24. What does lab do with the Alkali Samples?

25. How does WYDOT determine the CR number?
Alkali samples are tested for the following:
Minimum Resistivity
Ph level
Sulfates
Take samples for pipes 48” and smaller

26. Minimum Resistivity
A current is sent through a uniform soil sample to test the resistance. less resistance means the soil has a lot of free ions so corrosion will be more severe. “Hot Soil”

27. Measures the concentration of hydrogen ions
Ph Level (acid level)
Measures the concentration of hydrogen ions

28. SULFATES
Greater the sulfate level the greater possibility of corrosion.
Bacteria feeds on sulfates, free ions can bond and oxidation can occur.

30. See the Typical Pipe Installation Trench Detail
AASHTO (2002) states the central bedding, which is equal to one third of the outside diameter of pipe (refer to figure 4 above) should be “loosely placed” while the remaining portion should be compacted to unit densities discussed in previous sections.
The central bedding zone provides uniform support
Pipe which was installed with highly compacted soil were 70% less than installations with loosely compacted soil.

31. Ring shaped
Annular = ring-shaped

33. From 2012 Study
“Since deflections are in fact controlled more by construction practice than by design, it is increasingly becoming practice to place responsibility for control of deflections on the contractor, rather than the designer.”

34. DIVISION 800 Materials

35. Cell Classification - An indicator of long term durability based on the coating they put on the pipe to protect from UV light and environmental stress cracking.

36. Fill Height
Eventually the Bridge program is going to develop fill chart tables based on load and resistance factor design (LRFD).
Based on the minimum sectional properties. This is a conservative approach.

37. Inspection
Read and understand specification and use the Construction Administration Manual as a guide.
Bottom line is to make sure the contractor is installing the pipe in accordance with the plans and specifications

41. 18’X8’1”, 76’ structural plate arch