LAKE MARY ROAD
AVALANCHE CONTROL PROCEDURES
5-Year Operating Plan
Approved by: _______________________________________ _______________________
Kathleen S.
Morse
Date
Inyo National
Forest
District Ranger
_______________________________________ ________________________
Stephen Julian Date
Town of Mammoth Lakes
Town Manager
_______________________________________ ________________________
Rusty
Gregory Date
Mammoth Mountain Ski
Area
Chief Executive Officer
LAKE MARY ROAD
Avalanche Control Procedures
Winter
Operating Plan
Situation and Purpose
The Lake Mary Road has been
kept open throughout the winter since 1958.
As the years have gone by, use of the Mammoth Lakes Basin and Tamarack
Lodge Resort has increased dramatically.
Before 1983, avalanche
control was generally passive, ie. the road was closed and the snow allowed to
stabilize over time. However, the
closure was generally put into effect after a slide had occurred. There were not attempts, until late in the
winter of 1982-83, to forecast stability and close the road before a slide
occurred.
Before 1983, it became
evident that with the increase in use on the road, there was a corresponding
increase in the numbers of people exposed to the dangers of the avalanche
area. Before the forecasting/control
program went into effect, there were numerous avalanche-related incidents
including very close calls and subsequent vehicle burial. In early 1983, there were 6 vehicles buried
in slides, one of which was pushed over the edge of the road, and 8 persons
were nearly buried. Since the beginning
of the forecasting/control program, avalanche related incidents along Lake Mary
Road have been nonexistent.
In addition, as the sport of
cross-country skiing grows so does the need for consistent access. In 1982-83, the road was closed for a total of 72 days. The financial loss was traumatic to the
Resort, but the ultimate loss went unmeasured as thousands of skiers were
turned away from what has become the favorite cross country skiing destination
in Mammoth.
The purpose of the avalanche
forecasting/control program is to provide a safe, consistent access to the
Mammoth Lakes Basin and Tamarack Lodge Resort.
Description of Avalanche
Areas - Maps
FIGURE 1 is an area location
map depicting the recognized slide zones as they appear west of Lake Mary
Road. Contour intervals are 80 feet.
FIGURE 2 is an enlargement
of the precise avalanche prone areas along Lake Mary Road. Contour intervals are 40 feet. FIGURES 1 and 2 show road control points from
which traffic may be restricted while control measures (ski cutting/explosives)
are carried out to mitigate the avalanche hazard.
Individual Avalanche Path
Description
SIBERIA - Located above the
parking area. Generally very windswept
without accumulation problems.
PORCUPINE - Above road,
closest to the Twin Lakes outlet. This
area is accentuated by a small cliff 150 feet above the road where most of the
instabilities occur.
GORILLA GULCH - Located 300
feet north of Porcupine, this gully experiences heavy periods of loading on its
southern flank leading to cornice formation.
THE CHUTES - A cliff band of
exposed granite, which becomes unrecognizable in mid-winter. With snow cover, three distinct avalanche
paths become apparent.
HEAD FIRST – A leeward
collection area, resting between Chute 3 and Manzanita Bowl, consisting of rock
outcrops interspersed with manzanita and pines.
The area is bounded by cliffs to the southwest and the track of the path
empties out onto the highway near a clump of firs.
MANZANITA BOWL - A wide
concavity approximately 250 feet across at the crown. This slope has interspersed firs along the
lower half of the path site.
BANANA BELT - The area above
the avalanche paths from Siberia to the top of Gorilla Gulch. Generally very gentle slope posing no
problem, manzanita is the main shrub on the slope above Lake Mary Road, with a
depth of 2 to 5 feet. Loose scree and a
few firs add definition. Anchor sites
are minimal on the slope itself, but there are many above the avalanche slide
areas.
Aspect
The slide paths are all east
and southeast facing and lie in the lee of the prevailing southwest wind. Loading potential is great depending upon
wind velocity and the rate of snowfall.
Direct exposure to the sun aids in settlement of the surface. Underlying cliffs on the slope are possible
lubrication surfaces.
General Information
The length of slide paths
range between 100 to 300 feet. The
degree of slope is 30 degrees to near vertical at the cliffs. The Lake Mary Road is located in the lower
sections of the hillside and the road crosses through the track and runouts of
many of the slide paths. The combination
of the snow removal from the toe of the slide paths and the vibrations
generated by snow removal equipment makes the avalanche hazard on the highway
an issue of concern.
Forecasting
All avalanche areas
identified will be evaluated as needed.
Control measures will also be implemented as necessary.
Evaluations will be made by
MMSA ski patrol based on data collected from various sources including, but not
limited to:
Snow study plots and weather
data ie: wind direction and velocity, barometric pressure, air temperatures,
relative humidity and snow accumulations, snow pit analysis, and slide path
characteristics.
The avalanche potential on
the Lake Mary Road shall be evaluated by Mammoth Mountain Ski Patrol and/or
Tamarack personnel. Tamarack personnel
shall be responsible to provide personnel to close and secure avalanche exposed
areas on the Lake Mary Road to prevent vehicle movement when snowpack
conditions warrant closure. Personnel
shall ensure that the Lake Mary Road is closed prior to taking any control
action. The gates on the road may remain
closed for periods of time when the hazard is high (usually night-time hours),
before the control work begins. Control
time may occur at any time of the day, but will usually take place at day-break
and before night fall.
Since the Lake Mary Road is
a Town road, it shall be a responsibility of Tamarack personnel to contact the
Town personnel whenever avalanche control work or road closures are in
effect. Tamarack dispatch will notify
the following offices in sequence:
Contact Town
Police (Watch Commander) and Public Works Department (Dave Beck @ 934-2422 or
937-0494, or Todd Murphy);
Town of Mammoth Lakes
Dispatch (hours 8-4 ONLY) – 934-2011; OR
Mono County Dispatch (24 HRS) – 932-7549,
leave message; AND
Contact Forest Service - Front Desk daily
at 924-5500 from 8-4:30.
Under
normal conditions control work will be carried out at first light. There are instances when conditions warrant
mid-day control work. In such cases all
lodge intercoms will be alerted and all Resort guests and clients will be
immediately notified. Tamarack personnel
will be responsible to send a knowledgeable and informed individual to staff
the gate. This person will make certain
there are no people on the road between top and bottom closures.
Note: in the
event of an over night road closure, the slope instability may be too great to
send someone down from the Lodge to lower gate after securing the upper
gate. In such cases, Tamarack personnel
who live in town or Mammoth Mountain personnel (Mountain Maintenance or
Security) will be notified so that they may send up personnel to implement the
lower closure. Once the road has been
swept and clear, the road will be closed until control work is complete.
Once the proper closures have occurred, the avalanche control team will
be notified by Tamarack dispatch that they are clear to begin control
work. Actual control work will not start
until the control team is notified by dispatch that all closures are in place
and that all necessary entities have been notified. Control team and dispatch will be in
communication throughout control work.
Control procedures
Access will be attained by
either snowcat or skiing via the Chair 9 area.
The ski patrol has access along the entire control route with a snowcat
and predetermined shot points have been identified. Another method would be to ski the route
using the same path that the snowcat would use.
If skiing is selected, a snowcat may go out to pack the route a couple
of hours before the control mission.
Predominate slide areas are
the cliff bands that contain chutes #1, #2, and #3, Gorilla Gulch and
Porcupine. Six shots will normally be
used in these areas. Depending upon snow
loading, and other slide potentials, approximately 8 - 12 shots will be made.
The use of explosives will
comply with the most recent Forest Service Blaster's Handbook. Procedures authorized by the state for
assembly, transportation, use, and demolition of explosives are to be used by
all persons involved in the control process.
All persons performing the blasting shall be either a certified blaster
or a blaster-in-training, licensed by the California Division of Occupational
Safety and Health.
There are two formal road
closure points on the Lake Mary Road (see map).
The gates shall be signed in conformance with Forest Service
standards.
All control procedures shall
be documented and maintained by MMSA ski patrol. Documentation is maintained for a minimum of
four years. Avalanche Occurrence and
weather documentation shall be filled out and maintained with information
including: weather, method of control, paths that slid, how much deposition and
number of shots used.
Team members hold as a
minimum, current Advanced First Aid cards, California State Blasters
Certificates, are competent skiers with avalanche training, knowledge of
avalanche rescue, and use of transceivers.
The purpose of the Avalanche
Rescue Plan is to provide prompt, well-organized rescue effort to retrieve the
victim of an avalanche as quickly as possible.
Upon report of an avalanche, the avalanche site commander will determine
the avalanche site and will initiate a team for a hasty search. A Stage II Team will be gathered and
dispatched and will support the hasty team at the avalanche site.
The hasty search will begin
after it has been determined that the area is safe to enter, with no other
avalanches imminent. The search will
proceed to the site of burial to locate and uncover the victim in the shortest
possible time. On-site personnel will
initiate the hasty search procedure as follows:
* Post lookout, if necessary with radio communication.
* Locate and mark last seen spot of victim.
* Work from the last seen spot, downhill, marking
any evidence of victim in the slide area.
* Complete
surface search for victim and/or equipment.
* Begin
transceiver search
* Probe areas
showing indications of victim or probe likely areas.
* Form coarse
probeline. Continue coarse probe until
area is completely and thoroughly searched, then proceed with fine probe,
unless otherwise directed.
* If victim is
found, give appropriate first aid.
* Follow
instructions of avalanche site commander.
Before entering the site,
the accident site commander, or designate, will advise dispatch/recorder to
record names of personnel in rescue party and advise each rescue team leader of
the route to be used to the scene.
Stage II Search
This stage supplements the
hasty search with complete first aid equipment, medical attention and necessary
equipment, for evacuation and warming of the victim. A physician should accompany the party to the
scene at this time.
The rescue cache will
consist of two search packs, each pack consisting of the following:
* One (1) probe set - 6 per
set
* One (1) shovel
* One (1) headlamp with extra batteries
* One (1) roll of red flagging
* Two (2) dozen of red course markers
* One (1) blanket
* One (1) heat pack
There will also be an EMT
pack in the toboggan located at the Ski Center containing the following:
* O2 (Small) *
Back Board
* Non-rebreather Mask *
Traction Splint
* Neck Collar *
Sleeping Bags (blankets)
* Splints * Six (6) fuses
* General First Aid Kit * Headlamp with extra
batteries
* Heat Packs * 100 ft of 11 mm rope
* Tarp