Geography 1700 – Natural Hazards
Mid-Term Exam – Spring 2015
A. J. Allred, Adjunct Instructor
1. Putting surface water in pipes is not only expensive, but promotes high-speed flow that can
overwhelm storm drain capacity and cause unmanageable peak flows somewhere downstream.
True ___
False ___
Underground storm sewer drain piping is increasingly expensive and requires expensive
maintenance. Smooth, straight pipelines also promote high-speed flow that can cause
“spike” in flow volume somewhere downstream. In urban areas, storm drains are sort of
like “channelizing” a stream: it’s expensive and still fails sometimes.
Take a moment to compare Question 1 to Question 3 below.
2. Solar energy has a powerful effect on Earth processes, but the Sun is still very far away. So, tectonic
force becomes more important than sunshine in shaping landforms, including erosion and
weathering.
True ___
False ___
Solar energy is by far the most powerful source of energy on Earth. Tectonic force helps create landforms;
solar force helps wear them down, using gravity and water.
3. Putting surface water run-off in large pipes can help prevent local damage that might result if that
water were allowed to soak in. However, depending on downstream conditions, letting surface water
soak into the ground can also cause problems somewhere downhill. That is why engineering studies
are important and often expensive.
True ___
False ___
The first statement in Question 3 is true. Letting water soak into the ground is usually the safest and least
expensive solution, and most communities are trying to “get back to nature” by having property owners retain
or detain their own storm flow. This is the most important point.
However, sometimes allowing water to soak into the ground can lead to soil failure around buildings, or
somewhere else underground. That is why good engineering is often needed to determine the best combination
of water management. Question 3 is not intended to be confusing. It is intended to illustrate how complex
conditions can become in dense urban areas where paving and buildings put great stress on the natural ability of
soils to deal with water run-off.
The natural “carrying capacity” of Salt Lake valley may be something may be something less than the one
million people already living here, and more are coming. In other words, it is very possible that too many
people are living in Salt Lake valley for any affordable method to prevent flooding and water-related soil
failure.
La Conchita, California is example featured in the class textbook in which there are simply too many people
living in an area that is even more prone to soil failure than Salt Lake valley. Homes are still very expensive in
La Conchita, even though people know that another hazardous landslide will occur again.
Likewise, it is projected that Salt Lake valley population will eventually double, to two million. With all the
buildings, roads and parking lots there will be ever greater difficult handling surface water.
4. Coal mining in Utah causes soil failures on the surface and lethal danger to miners deep
underground. Coal reserves are often lost forever because previous mining has made the ground too
unstable for more coal extraction. A substantial portion of coal produced by Utah’s Skyline coal
mine is used for generating electricity for pumping water out of the mine. That water is from Electric
Lake, an artificial lake created for supplying power plant water.
True ___
False ___
Coal mining creates caves that . . . . cave in. Billions of tons of Utah coal will probably never be recovered
because previous mining made rock formations unstable. The artificial lake that supplies water to Utah’s
Hunter Power Plant leaks into Skyline mine that supplies coal for that same power plant. Some, millions of
dollars in coal from the mine is consumed in pumping water back out of the mine, a cruel irony. That is a good
example of what happens when we load the earth with water reservoirs even as we also mine underground.
Earth structures leak, and sometimes fail.
5. The Mississippi River delta is a good example of how solar forces gradually erode continental land
masses around the world. Millions of people in poor countries are vulnerable to death by drowning
because they are attracted to farming on river deltas and floodplains.
True ___
False ___
Everything in Question 5 is true. Solar energy produces the hydrologic cycle in which water evaporates by heat
and then falls as rain and snow that weathers and erodes landforms. Sadly, even in the United States millions of
tons of farm soil wash away, ending-up in the Mississippi River delta.
In poor countries, people try to farm these river deltas, leading to drowning when severe storms cause flooding.
6. In the United States, hazard insurance does not prevent property damage and personal injury.
True ___
False___
Insurance does not prevent hazardous events, it just replaces things that are lost. Sometimes insurance
companies appear to create the impression that buying insurance is a form of protection for family members or
for property. In reality, it is just money for your losses. Insurance ‘coverage’ can help people acquire a false
sense of security.
The class textbook goes back and forth a bit, often suggesting the need for more insurance in hazardous areas,
but then also recognizing that insurance does not stop ‘mother nature’. In fact, the U.S. FEMA is billions of
dollars behind in paying for insured losses.
7. About 10 percent of wetlands in the United States have been drained, paved or otherwise obliterated.
Wildlife habitat has been destroyed and there is less natural buffer to protect communities against
flooding and severe storms.
True ___
False ___
About 90% of U.S. wetlands have been destroyed. Vital habitat has been lost. Wetlands, including bayous,
swamps, bogs and flood-prone areas do provide a “shock absorber” against severe storms and flooding. We
should protect wetlands.
8. The main shock from the 9.1 Sumatran earthquake in 2004 released slightly less than 100 times as
much energy as the most powerful earthquake ever recorded in Utah (32x+32x+32x = 96x).
True ___
False ___
A 9.1M quake releases about
6.3  7.3 = 32x
7.3  8.3 = 32x
8.3  8.5 = 2x
8.5 8.7 = 2x
8.7 8.9 = 2x
8.9 9.1 = 2x
32 x 32 = 1,024 times greater energy release.
2 x 2 x 2 x 2 = 16 times more energy release.
16 x 1,024 = about 16,384 times more energy release.
Note: For shaking use 10x instead of 32x.
See also Question 36 below.
9. Community “run-up maps” can be very hard to prepare because:
a. A tsunami wave may originate from quakes located at any angle from the shoreline.
b. Daily tides, submarine shoreline shape and even atmospheric conditions can affect tsunami action.
c. Refraction (or reflection) can cause complex interactions between waves.
d. Building locations and human behavior during a tsunami can have wide-ranging effects.
e. All of the above complicate the process of trying to understand what tsunami waves might do.
Everything in Question 9 is true. These same factors also help explain why the location and timing of ‘rip
currents’ are hard to predict.
10. In the downtown Salt Lake area, recently updated building codes and hazard insurance will soon
eliminate buildings at risk for damage by natural hazard.
True ___
False ___
New building codes don’t automatically do anything to change old buildings. Over a long period of time, old
buildings are either retro-fitted or demolished to make way for buildings that comply with current codes.
See Question 25.
11. In large cities around the world, flood hazard can be almost eliminated if individual property owners
simply take responsibility to “harden” their own locations by paving and hard-surfacing as much as
possible. The combined effect of surface paving, roofs and other impermeable surfaces makes it
almost impossible for percolation and leaching to occur. Unfortunately, most property owners do not
take this responsibility seriously, and often allow surface water to simply collect on the ground and
slowly sink in.
True ____
False ____
Current policy is trying to avoid excessive paving, because hard surfacing helps concentrate and raise the speed
of water run-off. Letting water soak in “on site” makes each property responsible for helping reduce flooding
downstream.
Most of the time, keeping water on-site saves money in storm drain costs and prevents flooding downstream.
12. Earthquakes of the “slip-strike” or transform variety are generally responsible for the Wasatch
Mountains that have been rising above Salt Lake valley. These formations are a smaller, but still
important example of the more famous San Andreas fault system in California.
True ___
False ___
Slip-strike or transform quakes are mostly about horizontal motion, rather than vertical motion. The high
Wasatch Mountains are being formed by block fault or dip slip quakes that cause vertical displacement between
up-thrown and down-thrown blocks. The Wasatch Mountains are not a subset of the San Andreas system.
13. Increasing investment in public safety codes, rebar and concrete in Salt Lake valley is probably not
keeping up with overall natural hazard, because we are encroaching on hazardous areas, and making
some natural hazards worse by just being there.
True ___
False ___
We are spending more money and getting good results; however, the press of heavy population and hardsurfacing is still making it harder and harder to find economical and safe ways to get rid of surface run-off. In
fact, people are building homes higher and higher on mountains slopes in Salt Lake valley. Spending a lot more
money to make hazardous slopes safer does help, but still does not prevent soil failure such as creep, slump, or
even flow in neighborhoods.
It is getting harder to find good, safe building sites in Salt Lake valley, and spending more money on mitigation
is helpful but not enough to eliminate hazardous.
14. In the absence of an officially approved run-up map, what is a reasonable personal guideline for
designing your own safe zone during a tsunami warning?
a. At least 1.2 miles vertically and/or 1.2 miles horizontally
b. Try to reach terrain that is at least 100 feet above the normal water line, and/or at least a mile inland.
c. Do not take action until instructed by public safety officials, and then follow instructions carefully.
d. Don’t be impulsive: it is pointless to react to a wave until we know where the wave is going. People
who over-react tend to get hurt the most.
e. Answers ‘c’ and ‘d’ both work together as the best overall response to a tsunami warning.
In my own research, I have not found a comprehensive, unifying standard for what it means to “go to higher
ground.” So, based on my own study, I have never seen an example where a tsunami was lethal to people at
any location more than about a mile from a shoreline or more than 100 feet above sea level.
In some cases, a seiche wave on an inland fresh water lake has inundated places hundreds of feet above the
normal water line; however, I don’t know of any ocean tsunami that has done so anywhere except perhaps in the
Mediterranean Sea more than 1,000 years ago.
15. People often build in flood hazard areas even when riverine and riparian lands provide clues about
where water will go during high-flow events. In many cases, people obscure or cover-up natural
boundaries by grading, building and farming.
True ___
False ___
Everything in Question 15 is true.
16. The continuing, long-term increase in U.S. natural hazard deaths is mostly a function of:
a. financial deficits that prevent rescue efforts and hazard mapping.
b. poor quality information about hazards and prevention.
c. rapidly rising U.S. population, especially among illegal immigrants who lack insurance.
d. increasing disposable income for purchasing expensive vehicles and other property at risk.
e. Loss of life due to natural hazards is actually declining in the United States.
Human deaths from natural hazards are declining slowly over time, even though more people are living in
hazardous areas than ever before.
17. Most dams, levees and other flood-prevention structures in the United States are privately owned and
managed. They are often obsolete or weakened by age and lack of maintenance and inspection. All
water control structures, whether publicly or privately owned, may someday fail, causing great
hazard to people and property downstream.
True ___
False ___
Everything in Question 17 is true.
18. River levees are controversial because they often appear to function reliably over long periods of time,
and then suddenly fail to protect us in some way. Fortunately, floodwaters rarely reach beyond a
levee and water does not tend to damage, bypass or undermine the levee itself.
True ___
False ___
The first statement in Question 18 is true; the second statement is not true: levee failure does lead to damage
and loss, sometimes far beyond the levee barrier. Even when a levee does not fail, constrained water will tend
to increase in speed or flood level, over-topping and/or bypassing a levees. Levees do prevent loss, but are not
known for their reliability.
19. Theories about human-caused global warming and natural hazards are difficult to evaluate because
the Earth already had an unstable climate record long before human (anthropogenic) factors began to
add substantial greenhouse gases to the atmosphere.
True ___
False ___
Everything in Question 19 is true. Even though we are confident that humans are having a substantial effect on
Earth processes, those same processes were already highly variable long before humans had any additional
effect.
20. Based on simple interpolation alone, how far away is an earthquake if a “P” wave arrives 100 seconds
before the “S” wave?
a. 130 miles
b.
c.
d.
e.
520 miles
50 miles
All of the above could be true, depending on soil type
None of the above is a good estimate by simple comparison
Based on what the textbook says, a 50-second gap between P and S waves indicates a 260-mile travel distance
back to the hypocenter. So, based on simple interpolation alone, a doubling of time difference suggests a
doubling of distance back to the quake location  100 seconds ~ 520 miles.
21. In this modern era, Americans can usually run faster than most of their ‘stuff’ so we tend to lose
money but not our lives. As poorer foreign countries gain population and financial wealth, natural
hazards that once caused major catastrophes are now more likely to produce only disasters.
True ___
False ___
The first statement is true: in nearly all disasters, people show remarkable ability to run, hide, climb or
otherwise avoid death. However, most of our property is not that mobile, so we lose a lot of money and
disasters are increasingly catastrophic.
Many poor countries are also gaining wealth, but often lag far behind in disaster mitigation, so death rates are
still high, and property losses are rising. In addition, not only are rich people living on coastlines, but
increasing numbers of poor people are also living on coastlines, so the potential for catastrophic death counts is
perhaps more likely than ever.
22. Because ocean waves consist of crests and troughs, a four-foot swell can appear to be:
a. 12 feet tall
b. Three feet tall
c. Eight feet tall
d. None of the above is a good estimate
A crest of water “borrows” water from the adjacent trough, so the height of a wave crest is the same distance as
the depth of a wave trough: crest and trough both add back to average sea level. A genuine four-foot ocean
swell means a crest of four feet above sea level. So, the four foot crest height adds to the four-foot trough
depth, for a total difference of eight feet.
23. U.S. Federal land policy calls for elimination of karst formations. Over time, other nations will also
follow this practice. In the past 20 years, about half of all karst regions have been removed.
True ___
False ___
About 10% of Earth’s dry land surface is covered by limestone rock formations that are prone to easy failure by
intrusion of acidic water. It is impossible to eliminate limestone formations and the karst formations that result
when caves develop and then “cave in.”
In very limited situations, we could divert surface water so it does not seep into limestone, but there really is no
way to prevent karst formations from developing. Instead, we should be willing to pay for more geological
studies to determine where karst formations create unsafe conditions for buildings and other human activity.
24. Based on Earth curvature alone, how tall would a breaking or cresting tsunami wave have to be in
order to be visible from two miles away?
a. Three feet
b. More than six feet
c. No more than five feet
d. A minimum of 18 feet
e. A maximum of nine feet
Earth curves down or away from our line-of-sight at a rate of about three feet per mile of distance from our
eyes. So, at two miles away, Earth curvature ‘hides’ an object that is six feet tall (3 x 2 = 6).
25. Adoption of the most up-to-date building code does not provide an immediate improvement in safety.
True ___
False ___
See Question 10. Brand new buildings are likely to be safer, based on the latest building code; however, in
most communities, only a few new buildings are added each year.
26. Widespread use of the modern Modified Mercalli earthquake measurement system does not rely on
‘foreshocks’ as a tool for public alert or warning systems. The Mercalli system does not provide any
kind of alert before shaking starts.
True ___
False ___
The Mercalli system is about evaluating quakes after they occur. Mercalli is not about prediction or forecasting.
27. Earthquake shaking varies negatively (inversely) with the time difference between arrival of P
(primary) and slower secondary waves.
True ___
False ___
Shaking diminishes over distance and over time. Both of them increase together  a positive relationship.
However, the difference in arrival time between a P wave and an S wave increases over time and distance,
while shaking diminishes over time and distance  a negative relationship.
28. For earthquake damage to occur, the epicenter should be located about how far from the focus?
a. The hypocenter should be more than 50 miles laterally (to the side) from an epicenter, in order to
provide timing space between P and S waves.
b. The epicenter is always directly above the hypocenter, and quake damage varies inversely with
distance from a quake.
c. Generally at least 100 miles away, for the same reason as in answer (a) above.
d. At least 50 miles away from the epicenter, with P and S wave timing being important only for
measuring distance to the quake, not quake damage.
e. Answers ‘a’ ‘c’ and ‘d’ above are reasonable rules.
Answer b is correct. All of the other options are nonsense.
29. Lightweight, flexible buildings can be easily shaken by strong earthquakes. In Utah, the risk of death
or injury due to earthquakes is worsened by our reliance on lightweight wood-frame houses rather
than on natural stone, or even brick with heavy roofing.
True ___
False ___
The first statement is true: lightweight, flexible buildings can be shaken easily, but flexibility also allows them
to recover from shaking. In Utah, the prevalence of lightweight wood-frame buildings will save lives compared
to buildings made of heavy materials that can fracture, separate or fall during shaking.
In Japan, lightweight buildings are sometimes combined with heavy tile roofing, a bad combination because
walls will collapse more easily under heavy weight, and falling tiles will cause greater injury than lightweight
shingles.
30. It is completely false to say that a flood has occurred just because “our stuff got wet.”
True ___
False ___
It is true and practical to declare a flood when damage has occurred. Of course, we can also point out a flood
condition even if we don’t suffer loss. The 3rd edition of the class textbook clearly states that flood damage
indicates a flood.
31. After more than 100 years of channelizing streams, the U.S. Army Corp of Engineers has begun a
trend toward restoring rivers and streams to their previous natural condition. The result will
certainly be flooding, but in a more natural way.
True ___
False ___
Everything in Question 31 is true.
32. Flash floods and dam failures are most common in rainy places where shallow slopes and heavy
vegetation prevent safe run-off or absorption. Steady rain is more likely to produce a flood than a
brief, sharp rain storm that is typical of dry regions and deserts.
True ___
False ___
Flash floods are more common where steep slopes cause acceleration of surface run-off. Coincidentally, dry
country tends to not only have steep slopes, but also less vegetation cover to hold, deflect or slow down run-off.
Further yet, dry country also tends to have more ‘spiky’ rainfall – brief, heavy precipitation instead of ‘drizzle’
or light rain over a longer period of time.
Compare to Question 33 below.
33. The steepness of a nearby mountain or hillside is a good indicator of the hazard of living nearby. This
statement is also true when it comes to volcanoes, where steepness is a clue about the inherent danger
associated with different types of volcanoes.
True ___
False___
Compare to Question 32 above. Steepness is directly related to hazard, a positive relationship: steeper slope =
faster run-off.
Steep-sided strato-volcanoes are not only formed by explosive processes, but the steep slopes they create also
help cause faster flow of pyroclastics like ash, water and other materials that we can call “lahar”.
See Question 34 below.
34. High, snow-capped volcanoes may actually kill more people by mud than by hot, poisonous gases and
falling rocks and ash.
True ___
False___
See Question 33 above. Lahar flow, including mud from high-mountain snow-melt, are a serious threat to
people living downhill. Ash ejections into the atmosphere distribute pyroclastics over a wide area, and probably
kill relatively few people compared to catastrophic lahars, mud and other surface movement.
35. Which of the following tools is best for identifying the location of an earthquake?
a. Attenuation
b. Percolation
c. Inoculation
d. Permeation
e. Triangulation
Simple geometry by the creation of simple triangles can determine distance and direction to a quake location.
Around the world, seismograph stations work together, comparing time and distance to easily locate quake
locations anywhere on Earth.
36. An earthquake of M 7.5 will release about how much more energy than a quake of M 6.3?
a. About 64 times more energy
b. A little more than double the energy (Add 1.0x plus 0.2x so that 6.3 adds to 7.5)
c. About 32 times more energy
d. Two hundred fifty six times more energy
e. About double, plus about 20%
6.3  7.3 = 32x
7.3  7.5 = 2x
32 x 2 = 64x
See also Question 8 above.
37. The world’s massive ‘shield’ volcanoes present more overall hazard to people and property than do
smaller ‘composite’ and ‘dome’ volcanoes. More than 500 million people live on the shallow flanks of
shield volcanoes. Often, people have nowhere else to go, especially on Pacific islands like Hawaii.
True ___
False___
Shield volcanoes produce shallow slopes over which lava flows relatively slowly. The relatively hotter, heavier
magma that is released by shield volcanoes tends to be relatively lower in viscous silicates and gases that would
support pressure for an explosive eruption.
Mafic magma may be very hot, but it tends to be higher in iron and lower in “stickly” felsic magma that
contains more light-weight silicates. Steep-sided strato or composite volcanoes tend to be explosive because
magma with dissolved gases can build up explosive pressure.
So, mafic eruptions are more about “flow” and felsic eruptions are more about “blow”. The shallow slope of
shield volcanoes is evidence of flow rather than blow.
See Question 39 below.
38. High mountains near Salt Lake City are not caused by massive subduction zones that are more
typical of world-class tectonic plate boundaries.
True ___
False___
Tectonic forces in Utah are not closely connected to subduction zones along major plate boundaries. Our
mountains are more about slow rifting (divergence) and slow block faulting.
39. Which factors below are most associated with magmatic conditions that are violent or explosive?
a. Low levels of gases, less silica, and much lower viscosity
b. High levels of gases and highly viscous magma
c. High-viscosity surface flows such as very hot flood basalt
d. High-silicate, mafic rocks that are very hot on reaching the surface
e. Answers ‘c’ and ‘d’ are both correct
See Question 37 above.
40. Widespread adoption of modern land use planning standards and building codes has not been enough
to eliminate natural hazards. People still do dumb things like failing to study for Geography 1700
exams.
True ___
False___
Everything in Question 40 is true. . Investors, code inspectors and elected officials often fail to “do their
homework” when making decisions
41. The City of Nauvoo, Illinois was probably protected from flooding in 1993 by which of the following:
a. The Mississippi River was wider near Nauvoo than further upstream and downstream.
b. The city was located on the inside or ‘point bar’ of the river channel, rather than the outside.
c. River flow was not artificially constrained by levees, bridges or other obstructions.
d. All of the above were probably factors that helped reduce flooding around Nauvoo.
e. None of the above is a good explanation for why flooding was minimal around Nauvoo
All of the options in Question 41 help explain why Nauvoo flooding was minor, compared to places upstream
and downstream.
42. An effective network of electronic warnings or alerts in Japan would not have prevented building
damage and shutdown of nuclear power facilities during the 2011 Fukushima earthquake.
True ___
False___
Electronic warnings might have prevented fires by turning off switches before shaking started; however,
shutting down a nuclear power plant takes time, and wave inundation would have occurred in any case.
It is also true that there is generally an inverse relationship between the amount of time people need and the
amount of time people will get from a warning system: the further away from a hazard source the more
warning, but the less need for a warning because energy diminishes over difference.
43. Energy for setting-up natural hazards such as earthquakes, floods, tornadoes and landslides comes
from radioactivity. All life on Earth depends upon radioactivity.
True ___
All true in Question 43.
False___
44. Solid, dense magmatic rock tends to melt and flow in the asthenosphere, where pressure is reduced
near the surface of the Earth.
True ___
False___
All true in Question 44. Magma closer to Earth’s surface is under less gravity pressure from over-lying rock so
it can melt by decompression. Deeper in Earth’s mantle, gravity pressure is so great that molten magma is
essentially rigid.
45. Government programs that offer “buy-outs” to property owners have been very successful in
convincing people to leave hazardous locations. If we had more money, everyone would move from
hazard zones.
True ___
False___
Government “buy-outs” are generally not successful: people chose to move their in the first place for some
reason or another, and the fact that they have not been driven out by disaster suggests that they can keep
gambling into the future. Meanwhile, money incentives are often not enough to induce relocation and there is
not enough money available anyway. There are simply too many people living in hazardous locations and they
tend to be successful in not getting killed.
Search and rescue services, and government programs for disaster recovery help people feel confident that they
can endure natural disasters. Insurance policies add to the feeling that there is no reason to go somewhere safer.
46. Water that is disturbed by an earthquake will move at about what speed across open ocean?
a. 40 mph
b. More than 400 mph
c. 3.6 miles/sec
d. 1,000 mph or higher
e. None of the above is a good estimate, because tsunami wave velocity becomes measurable only when
it crosses the shoreline.
Speeds of 400 to 500 mph are common for tsunami waves in deep water.
47. After billions of dollars in Federal investment in flood-control structures over more than 100 years,
flooding along the Mississippi is now largely under control.
True ___
False___
Flooding is not under control along the Mississippi. Even after a disaster, people will tend to try to move back
to hazardous areas over a period of time. We tend to forget what happened in the past.
48. People will still tend to build in flood-prone areas even when they are provided good quality
information about the risks involved.
True ___
False___
Question 48 is true most of the time. Buying real estate is a complex process and may factors affect decisions.
We tend to buy what we can see, and we usually can’t see a hazard until it actually occurs in some way. Even
when we use careful financial risk analysis, we seldom have any clear idea about how often and how severe a
hazardous event will occur. So, we invest in things we can measure more confidently.
49. The U.S East Coast is not near a tectonic subduction zone, nor is it located on any part of the “Ring of
Fire”. An East Coast quake damaged the Washington monument and U.S. capitol building in what
year?
a. 1906 (same year as San Francisco quake and Galveston hurricane)
b. In the past four or five years
c. 1890
d. 1812-13 (same time period as the ‘New Madrid’ quake
e. 2005 (same year as hurricane Katrina)
The U.S. East Coast is part of a major plate that is moving slowly westward because of the Mid-Atlantic Ridge
divergence zone. There is no tectonic subduction along the U.S. East Coast, so massive quakes are not
occurring there routinely. Still, a quake of about 5.9 occurred in northern Virginia in the year 2011, causing
substantial damage.
50. If we leave them alone, naturally meandering streams will tend to slowly convert themselves into
somewhat predictable straight-line channels. Cut banks and point bars will gradually eliminate
themselves so that buildings can be safely constructed near river edges. Close proximity to rivers and
streams can then provide important natural service functions, such as scenic views.
True ___
False___
Naturally meandering streams will continue to meander with little predictability. Close proximity to rivers and
streams does provide natural service value, but building there is still hazardous.