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Projects >Friedman Memorial Airport, Hailey, Idaho
Airport Beats the Clock with Cement Solution
FDR (full-depth reclamation) with cement cuts cost over
$1,000,000
by John Arroyo, Executive Director, Northwest Cement Producers Group
 Central
Idaho attracts a steady flow of visitors and new residents. The
local airport in the town of Hailey relied on their consulting engineers,
an experienced contractor, and a soil-cement specialist to rebuild
their one and only runway in barely 30 days time. While some local
airports shut down for twice that length of time, the Friedman Memorial
Airport selected “full-depth reclamation” with portland
cement to meet a master plan objective and economically re-open
for traffic in the shortest possible time span.
Background
 Project
analysis began in the spring of 2006, nearly a year before actual
runway construction work began. Toothman-Orton Engineering, a Boise-based
civil engineering firm, discovered significant asphalt deterioration
after core samples were taken. Like many flexible pavements, a number
of asphalt layers were placed throughout the years. Twenty-three (23)
cores were cut out of the existing runway and nineteen (19) indicated
that the asphalt was in worse condition than expected. Even though
the top layer of asphalt was rated in decent shape, the lower layers
had been subjected to a deterioration called “asphalt stripping.”
Stripping is a common type of asphalt damage, caused when moisture
and traffic loads cause the asphalt cement to separate (or “strip”)
away from the aggregate. Airport management realized that a pavement
problem existed that required their attention, monitoring and eventual
action.
Airport Master Plan
The Blaine County vicinity attracts a steadily growing stream of
visitors throughout the year. Hailey is the county seat and stepping
off point for tourists (federal government land accounts for nearly
78% of Blaine County). Summer visitors exceed winter numbers even
with Sun Valley ski resort nearby.
The county population grew by 7.3% between 2000 and 2002 and by
40.1% during the past decade when total employment grew by nearly
50%, from 12,099 jobs in 1990 to 17,556 jobs in 2000.
The four-season recreational area contributes to Friedman Airport’s
needs to efficiently handle air traffic of all kinds. The airport
projects traffic to grow 44% by 2022, the target date of their long-term
master plan. “Aircraft operations” include all types
of aircraft and are projected to increase from 57,888 in 2002 to
around 83,800 in 2022. To meet this need, there is a strong likelihood
that during the course of the next ten years or so a new airport
will have to be opened to replace Friedman. Thus, there was no need
for a complete runway reconstruction.
Diagnosis
The airport board, management staff and engineers initially thought
that simply milling off some old asphalt and then adding an overlay
would suffice for several years until the airport master plan could
be implemented with a new facility. However, a more thorough pavement
analysis proved useful. When the first group of cores alerted the
experts to potential problems with asphalt stripping, Toothman-Orton
then performed a further investigation with assistance from geotechnical
engineers at Terracon, Inc. that confirmed that attention had to
be given to the deteriorating underlying asphalt layers.
Constraints
Airports such as the one in Hailey, Idaho, have to minimize closure
time. Airfield Operations Chief Pete Kramer says that “their
summer volume is busier than winter” and that a long closure
directly affects tourist, convention and conference traffic and
local economy. Friedman Memorial management set a 30-day maximum
construction time (runway shutdown) limit around which engineers
and contractors had to complete the remedial pavement work. That
critical parameter guided the consulting engineers as they evaluated
their options.
Pavement Design Options
 Based
upon airplane traffic and underlying soils, engineers at first calculated
three different asphalt-based pavement options. Concrete was not
considered because longevity was not required because of the planned
total airport replacement within the next ten years or so. A standard
FAA design was considered along with two other pavement sections.
When none of the first three could be constructed within a 30 day
construction period engineers approached the FAA and requested consideration
for full-depth reclamation. Full-depth reclamation (FDR) with cement
is a pavement rehabilitation process where a failed asphalt pavement
(surface and base) are pulverized, and then blended with cement
and compacted. After curing, the cement-stabilized material forms
a new base for the pavement, which is then surfaced to create a
long-life pavement structure. After FAA engineering expressed willingness
to consider FDR, an additional pavement option was developed with
input from Boise-based Terracon. The four possibilities (three ordinary
asphalt and one FDR) were:
| Standard FAA |
Alternate #1 |
Alternate #2 |
Alternate #3 |
| 15" #P154 subbase |
0 #P154 |
0 #P154 |
0 #P154 |
| 6" #P209 crushed stone base |
14" P209 crushed stone base |
0 #P209 |
12" FDR with cement |
| 4" #P401 asphalt |
4" P401 asphalt |
14.5" P401 asphalt |
6" P401 asphalt |
| 25" total section |
18" total section |
14.5" total section |
18" total section |
Full-depth reclamation with cement is a common practice among county
road maintenance departments and state transportation departments.
The process has different names in different states (such as CRAB
in Idaho, which refers to cement recycled-asphalt base) but the
end result is the same: rebuilding the pavement structure by recycling
the existing materials and stabilizing with cement. FDR is environmentally
friendly since it reuses materials on site, eliminating the need
to haul them to a land-fill.
The usual option and alternatives #1 and #2 required roughly 45-50
days of runway downtime, outside the time frame established by Friedman
Airport. Dave Mitchell, Toothman-Orton Engineers, said that “they
had to find a way to perform the necessary work and get it done
within the 30 days.” He was aware that the FDR method to rehabilitate
a failed asphalt roadway is used commonly by members of the Idaho
Association of Highway Districts as well as by the Idaho Transportation
Department (ITD) which has performed hundreds of miles of FDR with
cement. Toothman-Orton Engineers enlisted the engineering expertise
of Terracon who consulted on an FDR analysis and design so that
the joint engineering effort could propose FDR for an airport runway
application. The parties also brought together a contractor and
subcontractor experienced with pulverization and cement-stabilization
of old asphalt pavements to gather input from those with construction
experience. The proposed FDR approach cut 18 work days off the schedules
of the other pavement options. In the case of Friedman Airport,
a stronger base was not their objective, but it would result in
reducing the thickness of the total pavement section, and accomplish
the runway improvement within a short construction time period.
Additionally, FDR allowed them to attain the 30-day goal in a sustainable
fashion, as it recycles resources already in use and also eliminated
“probably 4,000 truck trips that would have been a huge impact
on the community”, according to Dave Mitchell.
Cost
The big surprise, says Toothman-Orton’s Mitchell, was that
the consulting group’s advice to airport management to use
full-depth reclamation would “cut their costs over a million
dollars” when comparing all four possible pavement scenarios.
Once the consultants proposed alternative #3 to FAA engineering
and received FAA approval (federal airport funding was involved)
and proposed the option to the five member airport commission and
received their approval to proceed, the project went to bid in early
2007.
Construction
Low bidder Western Construction, Inc. from Boise mobilized earth-moving
equipment in order to start immediately after Friedman Memorial
Airport closed the runway on April 23. Despite some late snowfall
the previous week, weather conditions cooperated with the scheduleand
the project was completed by the May 23 deadline.
 Western
selected Valentine Surfacing from Vancouver, Washington, a company
licensed in multiple states, to perform the actual FDR work on 73,440
square yards of runway. Approximately 6,900 feet of Hailey’s
7,500-foot airport runway had to be reworked. Chuck Valentine, president,
recounted that his crew took “five days to grind and five
days to mix” using two CMI pulverizing machines, a PR1200
and an RS800 along with a cement spreader truck and other typical
grading equipment. A nominal 2% of portland cement was used at the
start and was adjusted to the 2.3% level as construction proceeded
to adjust for soil moisture.
Precision Surveying and GPS Technology
 The
FAA requires tight pavement surface precision on pavements, a +/-
.02 foot allowance. Toothman-Orton required “robotic total
station” in the specifications they wrote, using ITD specs
as a starting point. Western Construction’s Jack Snyder comments
that “we can build a better product without stakes”
as he refers to the application of electronic grade control. Western
combined dual methods on the Friedman Airport runway, electronic
machine control as well as electronic grade control. He says they
started using GPS about five years ago. Knowing that the FDR process
is quick, requires precision the first time and that crews “can’t
come back the next day,” Western Construction took dual precautions.
They retained the services of Butler Engineering from Shelley, Idaho,
to build terrain models with surveying data. Western also assigned
experienced project engineer Marilyn Broek to the Hailey job along
with four project superintendents.
End Result
 The
project was successfully completed within the required 30-days.
As a result, Airport Operations Chief Pete Kramer now recommends
the FDR with cement process to other airport operators who want
to minimize their runway reconstruction closure times to bare minimums.
Western’s Snyder says that the successful completion depended
on “the right technology and a ton of experience” brought
to the table by the engineers involved and the construction team.
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