CPLC
An analysis of the proposed re-alignment of U.S. 89 in Logan Canyon, Utah.
August 20, 1979
Presented to Mr. David Stanley, Mr. Roger Williams, and staff, U.S. Environmental Protection Agency, Region VIII, Denver, CO.
Contents:
I. Critique of UDOT traffic forecasts, by Dr. David Schimpf, University of Minnesota at Duluth
II. C,ritique of UDOT Safety statements, by Dr. Jack T. Spence, Utah State University
III. Commentary on environmental impacts, by. Dr. William Helm, Utah State University
IV. Description of slides/prints of areas to be impacted
Enclosures: "Preliminary Proposals and Alternatives," UDOT
"Accident Statistics," Officer Leslie Langford, UHP UDOT maps
presented by Dianne Siegfreid
765 1/2 E. Center
Logan, UT 84321
801-753-3982
Thomas Lyon
655 Canyon Road
Logan, UT 84321
801-752-6571
Citizens for the Protection of Logan Canyon
GENERAL SUMMARY
1. Major impact on both environmental and visual quality of canyon.
2. Project contradicts nat'ional energy concern.
3. 80-90% of project requires cutting. (Remark by Project Engineer)
4. "Waste poses a major engineering problem." (Project Engineer) Waste to be used in related projects
5. "It'll never be worth as much as we've put into it already." (Project Engineer)
TRAFFIC GROWTH FACTORS
1. UDOT uses an unrealistic exponential model.
2. A linear growth model better fits daily traffic data.
3. Linear model forecasts lower traffic levels than UDOT's projections
4. Traffic data used by UDOT are limited to one busy section of the highway, yet are used to describe whole road.
5. Need for highway re-alignment not documented by current data.
SAFETY FACTORS
1. Suggested danger of Logan Canyon "Section III" is not supported by current data.
2. A major discrepancy exists between accident rate data and traffic volume.
3. 1977 accident rate figured by Utah Highway Patrol does not agree with UDOT report.
4. Statistical significance of accident data used is suspect.
ENVIRONMENTAL FACTORS
1. Numerous spills would encroach into Logan River from planned fills.
2. Silt deposits in river would destroy trout habitat and breeding cycle.
3. Loss of riverside vegetation needed by trout for low light intensit;
4. Creation of any culverts would impair spawning success of trout.
5. Loss of vegetative barrier lessens quality of fishing experience.
6. Major visual impact would result from the cuts planned, especially the two major cuts at the Temple Fork area, which would be, by Project Engineer Gary Lindley's report, 75' and as much as 150' across.
I. Critique of Traffic Forecasts
The UDOT projects future traffic levels in the section of canyon highway under discussion with a model which assumes exponential growth at 4% per year. Based on the UDOT's average daily traffic data (ADT) for Right Hand Fork, a linear traffic growth model fits the data nearly perfectly (r2 = 0.975). Such a linear model forecasts lower traffic levels in the future than the seemingly unrealistic exponential model.
Average daily traffic at Right Hand Fork after widening of lower canyon:
We were unable to obtain ADT's from the UDOT for 76,77, or 78; they were said to not be available.
The ADT's reported for Right Hand Fork are actually for the Logan River Bridge just below the section of road in question. Between this bridge and the narrowed roadway is the junction with the Right Hand Fork road, which leads to a youth camp, Forest Service campground, and major hunting and snowmobiling grounds. Our observations on a July weekend afternoon (high volume) suggest that about 5% of the traffic,
at the bridge actually comes or goes on this other road. The ADT projections should be scaled down 5% from those based on traffic at ,
the bridge.
In the projections of the UDOT, the Design Hourly Volume (DHV) is not a constant ratio of the Peak Hourly Volume (PHV) , varying from 1.22 to 1.40, depending on the year. This needs to be explained.
Critique, p. 2
In summary, we recommend that the Federal Highway Administration not grant permission for this project before the need for it is first documented via realistic traffic projections. These should embody all recent ADT's (after lower canyon was widened) and a realistic growth
model which takes into account the projected availability,of fuel for motor vehicles. Projections for the highway section in question should
be 5% less than those at Logan River Bridge. A constant ratio of DHV to PHV should be used, and its absolute value justified. These considerations could well postpone the time at which the capacity of the existing alignment (including a new surface on it) would become
inadequate.
II. TRAFFIC ACCIDENTS IN LOGAN CANYON, 1970-77
The Utah Department of Transportation (UDT) has concluded the unimproved sections of the Logan Canyon highway are especially dangerous. This conclusion has been advanced as one of the major reasons for undertaking an improvement project for section 3 and part of section 4. This conclusion is not supported by an analysis of the currently available data. Complete data for the period (70~78) has been requested from UDT but not yet received. The UDT decision is based on data published in the report, "Preliminary Proposals and Alternatives. SR-13 (US-89) Logan to Garden City," District one Office, Utah Department of Transportation, February, 1977, and some recent updates (included as inserts for the report). In addition, an independent study, "Accident Statistics, Logan Canyon and Rich County, 1976-77" by Utah Highway Patrolman L.D. Langford, has been made available(included). The following analysis is based on these reports.
I. Errors and Discrepencies
1. There is a major discrepency between the accident rate data presented in the UDT report, graph p. 39 insert, and the traffic volume data, graph T-2, p. 2[???]. Using the accident rate of 6.1 accidents/million miles for section 3 for the period 1970-77 (graph, ,p.39 insert) and the length of section 1 (5.1 miles) the average daily traffic (ADT) may be calculated, given the total number of accidents in this section (120):
ADT = 120 x 10 6/ 6.1 x 365 x 7 = 1509.5 VPD (vehicles per day).
From table T-2 of the UDT report (p.28) ADT for section 3 varies from 2225 VPD (1970) to 2888 VPD 1977 festimated from 1975 by adding 4% increase per year, as suggested by the UDT). Clearly, the 1509.5 VPD figure does not agree with the data of Table T-2. If, instead of 1509.5 VPD, an average figure for the period of 2549 VPO, an accident rate for section 3 may be calculated:
Accident rate = 120 x 106/ 2549 x 365 x 7 x 5.1 = 3.61 accidents/million miles.
This accident rate, 3.61, is lower than the Utah State average for the same period (3.9, as seen on the graph on p. 39 insert). Therefore, either the data of table T-2 is wrong, or the accident rates used by UDT in the graph of p.39 insert are grossly inflated. If the accident rate for section 3 is, in fact, 3.61, this section is not dangerous. Since this section has the highest rate, when similar calculations are made for the other sections it appears the Logan Canyon highway is much safer than most roads in Utah.
2. The accident rate for 1977 calculated from the Langford study is not in agreement with that reported for the same year in the UOT graph (p.39 insert). The Langford report covers a slightly longer section (Zone II) (8.27 miles) and the data must be corrected slightly for this; this correction, however, has no significant effect on the result. Using the Langford data for Zone II (Right Fork to Cattle Gaurd above Ricks Springs), the accident rate may be calculated (Langford report, p. 16): Zone II accident rate = 4.84 x 106/ 365 x 2797.6 (AOT) =4.74 accidents/million miles.
Clearly, this is considerably lower than the 7.2 value used by UOT (graph p.39 insert), and gives considerable support to the calculation in 1. above.
UDOT cal. 7.2 ac./10 6 miles
Again, this rate (which is the highest for any Zone of Logan Canyon in the Langford report) indicates Logan Canyon highway is relatively safe.
II. Doubtful and Erroneous Conclusions
1. Using the data of UDT graph, p.39 insert, for accident rates for various sections of the Canyon, the question must be asked whether this
distribution is significant or is it, in fact, simply due to random variation. This question may be answered by a relatively simple statistical test, the chi squared test for normal distribution in a set of data. If there are no differences between sections with respect to accident rates, then all
should have the same, or the average for all sections:
[formulas]
Using a chi sqare table at 6 degrees of freedom, the critical values of chi square are 2.20 at 90% and3.45 at 75%. The calculated value for the
data (3.390) indicates the probability of this distribution being random is between 75 and 90% . In other words, the distribution of the graph on
p. 39, UDT report indicates there is only a probability of 10-25% of the . apparent differences in accident rates for the various sections being
real. The conclusion therefore, that section 3 is significantly more dangerous than section 1 or 2 (already improved) is not valid. To base
a decision to improve this section on such unlikely probabilities is, at the very least, highly questionable.
2. On p. 40 of the UDT report, it is stated a definite relationship exists between volume of traffic and accident experience. This may be
tested statistically by plotting the data of the table on p.23 of the report (traffic volume by month) against the data of of the table on
p. 41 (accidents by month). It is assumed the traffic volume data distributions for 74-75 are the same as for 71-75 (since all data are normalized to percentage distributlons by month, this assumption seems highly reasonable). This plot should be a straight line, and the coefficient of determination, r2, for this line, is a measure of the correlation that does in fact exist between the two variables. This calculation from the
UDT data gives:
r2 = 0.37.
For a 1/1 correlation, r2 = 1.00, and for no correlation, r2 = 0. Anything less than about 0. 9 is statistically suspect. The actual value, 0.37, is indicative of a very poor correlation at best. The conclusion that traffic volume and accident rates are correlated must be regarded
as quite unlikely. Since this conclusion is used by UDT to justify the project (wider highway = less congestion by spreading out the
traffic of high volume periods = fewer accidents), it appears UDT is grasping at straws in a desparate attempt to rationalize the construction.
A better conclusion would be ·that the safest time to travel the canyon is during periods of high volume.
The same calculation may be made from the data for 1976-77 from the Langford Report, normalized to percent (Langford Report, p.12), assuming the traffic volume distribution used in the UDT ·report applies to 1976-77.
The result is:
r2 = 0.32
Again, a poor correlation between traffic volume and accident frequencyis found.
These results may reflect the fact that road condition in Winter, particularly in the upper canyon (section 3) is more important than traffic
volume, a factor not considered in the UDT report.
III. Types of Accidents
No data is yet available from UOT with respect to type of accident in each section. For 1976-77 from the Langford Report, 33% of the accidents in Zone II (section 3 and part of section 4) resulted in personal injury (PI), while 41% of the accidents in Zone I (sections 1 and 2, improved)
resulted in perspnal injury. This suggests the severity of the accidents in the new sections 1 and 2 is greater than in sections 3 and 4, but more data over a longer period is needed to confirm this.
With respect to fatalities and deaths from accidents, the data are (see insert to UDT report): 1970-77
In view of the small numbers, no statistical conclusions may be drawn; with respect to fatalities and deaths, however, there is no evidence to indicate the improved sections 1 and 2 are any safer than the unimproved sections 3 and 4.
IV. Causes of Accidents
The single most improtant cause of accidents is speed- traveling too fast for conditions:
UDT ,report (insert) 1970-77 47%
Langford report 1976-77 63%
While the improved sections 1 and 2 were originally designed for 40mph they are signed for 50 mph. This may account for the higher PI accident rate and number of deaths in the improved sections
V. Further Analysis
UDT officials have promised a complete set of accident statistics (available on computer printout) will be furnished shortly. These statistics, covering the period 1970 - 77 will be analyzed with respect to accident rates, type of accidents, road conditions, and other pertinent factors, and the results will be made available as soon, as possible.
As one might expect from a highway with Logan Canyon's geometrical configuration, the largest single type of accident was running off the highway on a curve. Hitting. another vehicle was the next largest category. Together they accounted for 69% o fall accidents on the highway. The apparent cause of 81% of Logan Canyon accidents is credited to careless driving, or driving too fast for prevailing condifions. Recognizing the major cause of these accidents, and in light of numerous accidents encountered in Sections 3, 4, and 7, it is reasonable to place a portion of the blame on the highway itself. All three sections possess similar characteristics - intermittent steep grades, narrow traffic lanes, small shoulders, tight curves, and poor sight distance, a combination which will surely induce abrupt speed changes and increasing the potential for traffic accidents.
There were twenty fatalities which occurred along the Logan Canyon highway during the seven-year study period - six in 1973, six in 1974, four in 1975, one in 1976, and three in 1977. Eighteen of them happened while attempting to negotiate a curve. Alcohol may have been a contributing factor in six of the fatal accidents, two of which occurred in Section 3, and four in Section 1.
Costs:
(Space for Graph)
III. EFFECTS OF ROAD BUILDING ON THE LOGAN RIVER
Utah Department of Transportation personnel have stated that they plan to keep the Logan Canyon road as close as possible to the river to minimize the size of road cuts. This will probably result in numerous fills encroaching on the river bank and spilling into the river. These fills contribute silt to the river via runoff during rain storms, and by erosion of the slope by the river itself. Both types are evident on fills created by previous construction at lower elevations in the canyon.
Silt in streams creates several problems for the following reasons. In general the larger the size of a particle of soil or rock, the higher, the velocity of water flow required to transport it downstream. Conversely, small particles can be transported by relatively low velocities (see lower curve in Figure 1). If a silt-sized particle is deposited, because of passing into a region of low velocity or because of being added to the stream during a period of low flow, it will not be picked up again without a velocity of flow above the lower line. If the particle, with others which were deposited with it, remains in position so as to become consolidated, it will take a much higher veloctiy to dislodge and transport them once they become to dislodge and transport them once they become consolidated.
Normally in this region the heaviest runoff, and thus most erosion, occurs during the spring. Streams appear discolored because of the heavy silt load, but stream velocities are also high because of the extra volume of water. Under these conditions silt is most apt to be transported downstream until velocity of water flow decreases in a reservoir or marsh. The key to minimum stream damage due to silt is the high transport capability of swiftly flowing water. During summer and fall volume of stream flow is low, velocity of flow is minimum for
the year, and thus transport capability is low. This is also the season of low erosion potential, with fully leaved trees, shrubs, and grass intercepting rainfall, and a layer of leaf litter protecting the soil surface in natural or undisturbed areas. Summer storms may cause
a small increase in stream volume, but do not add large quantities of silt. Streams remain quite clear.
Large road cuts tend to be prone to erosion. Slopes are steep and vegetative cover sparse. Raindrops from summer storms have a high
probability of striking the soil surface, dislodging particles and washing them downhill. Erosion from such areas can be severe. Road construction or any other activity which produces large expanses of bare earth changes the normal pattern of erosion and transport of silt.
The change adds silt to streams at the worst possible time, during low flow periods.
Large, relatively bare slopes \vhich result frolll the type of construction being proposed are the source of too much silt to be intercepted and retained by a narrow strip of vegetated land between road and river. If large fills are necessary a broad zone should be left between road and river, but this forces the road into the mountainside, creating additional problems.
Much of the bottom of trout streams is gravel or stones. Invertebrates, upon which the fish feed, reside not only upon the upper surface of the bottom but well distributed in the spaces between stones to depths of several inches. Young fish, shortly after hatching, will seek shelter beneath and between stones on the bottom. Fish eggs are deposited in shallow nests scooped into gravel bottoms, and covered
with gravel from upstream. There silt has been deposited the spaces between stones are filled, greatly decreasing the supply of food for
trout. Hiding and resting places, for small fish are also decreased. Silt in -gravel decreases -the flow of water through the gravel. Trout eggs require a constant supply of oxygen, available only from flowing water. Mortalities of 95-100 percent are to be expected when water
flow through gravel is impeded by silt deposits. As pointed out above silt deposited during summer may become consolidated, resisting removal by all but the highest velocity of flow. Such high velocities are not normally found prior to brown trout srawning season in the fall.
Another effect of fills encroaching into the river is the destruction of pools. Trout require areas of low velocity flows for resting, and pools next to the stream bank are particularly desirable. Such pools are frequently filled in when road fills encroach on a river.
A particularly damaging effect of fill encroachment is the elimination of vegetation which hangs over the river. This vegetation provides shade, especially in area of low velocity currents, where trout can rest. Brown trout require low light intensities and slow currents for resting areas. In shallow rivers, such as the Logan, low light intensities are usually found along banks with abundant vegetation, hanging over the water. Elimination of such vegetation will greatly decrease the number of brown trout inhabiting the area.
There is a prorosal to change the location of the road in the vicinity of Logan Cave by cutting into the mountainside across the river from the present road, crossing the river for a very short distance, and returning to the old roadbed. This will require an oblique crossing of the river. If such a crossing is accomplished by installing a culvert, such a long tunnel may create an impediment to fish movement during spawning seasons.
Finally, denuding the area between the stream and road by filling to or very nearly to the river creates an undesirable condition for fishermen. One of the reasons for fishing is to get away from the hustle and bustle of the working world, and seek solitude and quiet. Without a vegetative barrier between the river and the road, fishermen are exposed to the sight and sound of passing traffic. This converts fishing from an experience in the wild, to a noisy session next to the highway.
From the standpoint of erosive slopes, siltation of the river and scenic considerations, a, wide roadbed is not acceptable in this canyon.
IV. Description of prints showing areas to be impacted:
1. Just downstream of China Row, looking eastward. This is the first proposed cut of any size.
2. China Row picnic area, looking eastward. Proposed cut would take most of the trees in the photo, then go through a ridge just visible at curve of road in photo.
3. Wood Camp Hollow, looking northwards. Site of District Ranger's proposed road and campground, and thus site of waste from cuts on the proposed re-alignment. Ridge in background is part of Mt. Naomi Wilderness Study Area (RARE I, RARE II); entire Wood Camp Hollow has been proposed for addition to the WSA by local conservationists.
4. Present trail in Wood Camp Hollow, where the proposed Forest Service road would go.
5A. At Logan Cave, looking westward downstream. First bridge of proposed re-alignment would cross Logan River just downstream of curve, then highway would cut hillside on left before recrossing river.
5B. Slightly upstream of Logan Cave, looking downstream; photo shows proposed alignment cutting hillside and bridging Logan River.
6. Slightly upstream of Cottonwood Creek, looking downstream at proposed cut. Ridge to be cut is first ridge east of Cottonwood Creek.
7. Between Cottonwood and Lower Twin Bridge; cut is near to base of cliffs; similar cut slightly upstream was not photographed.
8. Unstable rock face in cut at Lower Twin Bridge. Re-alignment would eliminate visible cliff.
9. Lower Twin Bridge, looking downstream, showing cut of rock face and proposed widening of high bridge.
10. & 11. Dugway between the Twin Bridges. Re-alignment proposed here is a widening, supported by a retaining way the length of the dugway, standing on the steep talus.
12. Unstablerock face at upper end of Dugway, to be eliminated in proposed re-alignment.
13. Looking upstream (eastwards) at ridge just east of Upper Twin Bridge.
14. Photo shows jundtion of Temple Fork road and US 89; looking northward. Proposed alignment goes through ridge at left (seen from downstream in photo # 13) with 75' deep cut, bridges Logan River slightly upstream of junction of two roads visible, then cuts ridge to the right.
15. Looking downstream from hill above Ricks Spring. Photo shows both ridges to be cut. Proposed re-alignment is now on opposite side of
Logan River from present highway, thus necessitating another bridge upstream of Ricks Spring.
Highway 89 Digital Collection
