Bridge Construction in La Estancia, Guatemala 
By Dr. Zitomer

We departed for Milwaukee for Guatemala on January 21, 2001 in our effort
to build a concrete bridge for the village of La Estancia (pop. about
8,000). The trip was coordinated by Paul Johnson, a retired civil engineer
from Brookfield, Wisconsin. Paul was head of the environmental group of a
consulting engineering firm. The one thing the 14 group members had in
common was their friendship with Paul. About one third were from Paul's
church, one third were related to Paul, and the remainder were friends of
Paul.

Mark Corsentino and I were the two trip participants with Marquette
University ties. Mark is a graduate student in the department of civil and
environmental engineering. He received his undergraduate degree from
Marquette in biomedical engineering. We both heard about the trip when
attending a Milwaukee Engineer's Forum Luncheon sponsored by the  American
Concrete Institute, Milwaukee Chapter,  on December 14, 2000. The
Engineer's Forum meeting is held about once per month and is run by
Engineers and Scientists of Milwaukee (ESM). Paul talked about his
engineering service experience. Since retiring from R. A. Smith in 1995, he
has been involved in about 20 volunteer engineering projects in Guatemala,
El Salvador, Bolivia, the Philippines, Armenia, and Soviet Georgia. The
work has included domestic water supply systems, wastewater treatment
systems, dams, reservoirs, irrigation systems, harbor design, and solid
waste planning.

We were building the bridge because the river flow during the wet season is
so high that the people cannot cross the river. The average depth of flow
is about 5 feet during the wet season, and they can't easily cross the
water to get to the market in the near-by city of St. Martin. It is
important that they are able to sell their goods (coffee, bananas, oranges,
sugar cane, weaving, etc.) and buy other necessary provisions (clothing,
tools, etc.). The local people asked the Guatemala service organization we
worked with (i.e. PAVA) for help in building the bridge. The cost of the
material was about $5,000 to $10,000, and was provided by the US
participants and other private donations.

We first flew to Houston, Texas (about 3 hours), and then on to Guatemala
City (about 3 hours) . Then, we took a bus to the city of Antigua,
Guatemala. The next morning, it was off to La Estancia by bus (about 2
hours). We passed through Chichicastinango, and then the town of St.
Martin. This city had just gotten electric lines installed in the last few
months. After St. Martin, the road changed from paved to unpaved, as we
passed through beautiful mountain scenery. From about October through
March, it is the dry season in Central America, and it is very dry. It
didn't rain the entire time we were in Guatemala. The scenery was dry but
still green, with beautiful mountains. In this rural location, many
indigenous people still live. In Guatemala, about 80% of the people are
descended from the original native populations. In comparison, disease and
mistreatment has reduced the native population in El Salvador and the
United States to nearly zero. The native Guatemalan women  wear very
colorful costumes (long skirts and blouses) which they weave themselves.
Each village or area is known for its distinctive textile pattern or
technique. The women carry water and baskets of goods on their head. It was
common to see a women carrying a basket on her head and toting a baby,
strapped to her torso with a band of cloth.  The men wear jeans, tee
shirts, baseball caps, cowboy hats, etc. And carry machetes (about 2.5-foot
long knives) with which they do much of their work. Most of the people are
less than about 5-foot 5-inches tall and are very thin. There were no fat
people, dogs, or horses in the countryside.

We arrived in the small location of Cancurun, near La Estancia on Monday,
January 22nd. We unpacked our sleeping bags etc. At a small schoolhouse at
which we slept for the next four days. The school was a concrete block, one
story structure. We kept our things in one room, and we slept outside on a
concrete porch that had a roof. After unpacking, we went down to the work
site, which was about 1200 feet away. We had to walk down a steep slope,
down to the river. The elevation difference from the school to the river
was probably about 150 feet. On this first day, we worked on constructing
the bridge, pouring about 75% of the center pier. The first group that had
worked the week before completed the pier footings and the first pier.
Lunch was brought to us by some village women, who cooked it and walked it
down to the job site on their heads. The meal consisted of beans, corn
tortillas, and, sometimes, a treat, such as a tamale, rice, or chicken. A
special treat was a Coke or orange crush, etc. That was provided for us by
the Guatemalan charity group that coordinated the trip, PAVA. Soda is a
rare and special treat for people in the village.

At about 5 PM, we walked up the slope to the schoolhouse. There was one
water tap outside the schoolhouse at which to wash, then we walked about
300 feet to a local family's home, where we ate dinner. Dinner was always
lighter than lunch, and typically consisted of beans and corn tortillas. A
special treat was french fries one night. The beans tortillas, and water
for coffee/tea was heated over an open wood fire in the family's home. The
smoke went everywhere since there was no chimney or hearth. The smoke was
said to account for cataracts and breathing problems the women suffer.
There was no electricity in the village.

The bridge was designed by Mike Gabor. Mike is a professional engineer and
works for a consulting engineering firm in the Illinois-Wisconsin area. The
bridge was constructed of reinforced concrete. The deck was supported by
three piers that were about 9 feet high, and had a foot-print area of 15 by
2.5 feet. Therefore, each pier contained about 12.5 cubic yards of
material. The bridge deck was comprised of two, 20-foot long slabs, placed
end-to-end. Each slab was 15 feet wide, 20 feet long, and 10 inches thick.
Therefore, the deck contained about 18.5 cubic yards of material. The total
bridge required 56 cubic yards of material which weighed about 113 tons.
All the concrete was mixed in a 0.25-cubic-yard mixer - this was a lot of
work. Thewater, stone and sand were moved and measured in 5-gallon buckets.
The cement was measured by the 94-pound bag. It was type 1 portland cement
(4000 psi).

Guatemala bridge, part-2

The construction was accomplished without power tools, and we did not have
an electric generator on site. This was done so that any construction
techniques the local people learned from us could be employed after we left
the site. In the future, I suggest that some electric tools should be used
so that more can be accomplished in the timeframe available for a service
project (about 2 weeks). The cement, reinforcing steel, sand,  gravel, and
lumber was delivered to the site by truck. Cements was contained in
94-pound (42.5 Kg) paper sacks, which the local men transported on site on
their backs. It was not uncommon for a Guatemalan who weighed about 140
pounds to carry two 94 pound sacks on his back.  Sand and gravel was
delivered in loose bulk and was transported in wheelbarrows or 5-gallon
buckets. Lumber consisted of some planks that appeared to be cut by a chain
saw on a jig - this rough lumber was freshly cut, had some bark still
attached, was very wet, and was very heavy.  The wet lumber was mostly
pine,  4 by 6 inch, and was used as columns to support the formwork and
deck concrete. This lumber  probably weighed about 15 pounds per linear
foot. Since it was from 10 to 18 feet long, the wet members probably
weighed from 150 to 270 pounds. Needless to say, it took at least two
people to move a member. The members were cut to length  on site using a
hand saw.

Other wood boards were dry, and appeared to be cut in a mill, since they
were dimensional and square. These dry boards were purchased to construct
concrete forms. They were cut using a hand saw. Local people often used
their machete quite skillfully to rip a board when required.

The concrete was mixed using a gasoline-engine-powered, 0.25-cubic yard
mixer. The mix consisted of 1 bag of cement (94 pounds, 1 cubic foot, type
1), 5 to 10 gallons of water, 10 gallons of sand, and 10 gallons coarse
aggregate (about 1-inch stone). I give the volumes in gallons because sand
and stone was measured in 5-gallon buckets. Stone buckets were filled to
the brim. Sand buckets were filled about 80%. To put it in perspective, the
center pier contained about 11 cubic yards of concrete which took
approximately 45 batches of concrete, the sum of which weighed about 45,000
pounds - all of which had to be lifted approximately 3 feet from the ground
to the opening of the mixer, then the wet concrete had to be placed from
zero to 8 feet from the ground. It took approximately 4 minutes to produce
one mixer-full of concrete. Therefore, the pier was poured in about 3
hours. To calculate the energy required just to load the mixer, it took
45,000 pounds times 3 feet, or 135,000 foot-pounds of energy over three
hours. This is 45,000 foot pounds per hour, or about 17 watts. It's hard to
believe a 40 watt bulb uses about twice the energy I expended mixing that
concrete. Of course, the energy to move the aggregate to the mixer and the
energy to place the concrete in the form is not included in my estimate. It
suffices to say that electricity is a great help.


Daniel H. Zitomer, Ph.D.
Assistant Professor
Civil and Environmental Engineering
Marquette University
Milwaukee, Wisconsin 53201-1881
414-288-5733
fax 414-288-7521