Incidents:Webbing failure in Cerberus
| Webbing failure in Cerberus | |
|---|---|
| Date | 2017/02/17 |
| Location | Cerberus_Canyon_(South_Fork) |
| Severity | Injury |
| Canyoneering-related | Yes |
| SAR involvement | No |
| Navigation problem | No |
| Environmental problem | No |
| Communication problem | No |
| Planning problem | No |
| Skills problem | Yes |
| Body movement problem | No |
| Rigging problem | No |
| Rappel problem | No |
| Insufficient gear | No |
| Gear failure | Yes |
Contents
Summary
A webbing anchor tore free, causing a canyoneer on rappel to fall 15 feet. He landed in wet sand.
- Incident Time: 12:40pm
- Rappel: 16 of 29.
- Patient: Male, ~25 years old, 235 lb+ with backpack
- Group size: 9
Cerberus is a lengthy technical canyon, even for advanced groups with many years of experience. The frequency and length of rappels, anchoring challenges, and advanced down-climbing make for an arduous day in hostile conditions. Those who participate in this difficult, potentially dangerous trip are richly rewarded by teamwork, accomplishing the extraordinary, and experiencing a part of Death Valley few have ever seen.
Rappel 16 is a 2 to 2.5ft diameter, partially buried boulder, with webbing wrapped around the rock at ground level. The base of the rock was set into the soil and was not movable, it had several smaller rocks stacked on top of it. The existing webbing was 1" tubular webbing tied in a loop with a water knot, the loop wrapped horizontally around the base of the rock and the knot was at the back of the rock. Front side angle of the webbing was approximately 30 to 40 degrees. The anchor rocks and webbing was inspected prior to using it. The webbing was visually inspected all the way around and there was no significant wear or discoloration. A single (9mm low stretch) rope rappel thru the quick-link and blocked the rope with a Figure 8 Block. This anchor was backed up with a meat anchor with the station attendant attached to the "pull" side of the rope. The rappel consisted of a two stage drop, an initial drop sloped 15 feet down to a 10 foot wide chock stone, which terminated in another 15 foot vertical drop, the anchor was set 10' back from the initial drop.
Accounts
From the rappel station attendant:
Four of our group rappelled and the anchor did not move and looked secure. There was a long wait until the second half of the group came through so I took a break and had some food, when the next person got there he tied into the rope and I watched him rappel down (There was no back up to the anchor at this time) After the 1st stage he walked to the second stage and I observed the rope slack, then it loaded, immediately after that I saw the webbing blow out.Upon inspection on the anchor after the fall I did not see any movement of the rocks, the webbing was torn as pictured. There was one edge of the rock on the back corner that could have been a wear point, I don't know if this is where the webbing broke at or not, or if it was a cause of the webbing breaking. In my opinion the edge was not significant enough to cause a break in webbing of adequate strength.
After the fall I tied a loop around the rock with new webbing, in the same manner as the previous piece. I then inspected it. After the next 3 canyoneers rappelled down, there was no movement in the anchor and there was no wear or tear in the webbing (Yes, it was backed up with me as the meat anchor). I rappelled from it with no incident. I used an orange 1" tubular webbing for the anchor, it is the only orange webbing in the canyon. If another group goes through, they can inspect the anchor and voice a second opinion.
A group that ran this canyon in December 2015 recall they may have replaced this anchor. It was a color they were using that day. If that were the case, this webbing was only one year and two months old. After testing pieces of the webbing that seem less affected by UV damage, it seems unlikely that this failure was due to chemical damage.
Patient care and Followup
Half of the group was in front of the patient, and half behind. Group members in front heard the patient yell. Members behind the patient were retrieving a stuck rope and reported not hearing any calls of distress. The front of the group was lucky that they were within voice range. Those in front quickly returned and began medical assessment, treatment, documentation, and divided up patients gear for the extraction. The patient (who is right-handed) was unable to rotate his left forearm from palm up to palm down.
The patient self-administered 800mg of Ibuprofen. Water and food was carried for him and proffered throughout the afternoon and evening. He declined a splint and self-rescued the remainder of the canyon. He executed (or was lowered through) countless downclimbs and 13 rappels up to 270 feet. A fireman belay was provided for all rappels. During one slippery rappel, the patient lost his footing and could not both protect his arm and hold the rope. He was advised to release the rope and use it to right himself. He was slowly lowered via fireman belay.
The patient was taken to the emergency room early in the AM the next day and given a temporary cast. Upon radiologist inspection of x-ray slides, patient was told he had fractured left forearm radius head. Physical therapy later revealed a fractured metacarpal, and a bruised or broken rib. Patient was placed in a cast from the upper forearm down to his fingers.
Lessons
- When wet, do not trust that you will be able to accurately assess UV damaged webbing.
- Be very suspicious of webbing in typically dry water courses up to a week after rain in the area.
- If your anchor is suspect enough to warrant a backup, backup all members in the party.
- Knowing that a backup anchor is in place contributes to anchor complacency.
- Knowing that other heavy party members have rappelled before you contributes to rappel technique complacency.
- Instruct your patient ahead of time that should they fall they can protect their injury once they're sure a belay is activated.
- Use of a whistle may be more effective than yelling for attention.
Thoughts for future failures
- Reconstruct the crime scene with failed webbing and take pictures of the anchor (We thought we did, but failed in the adrenaline.)
- Take water and soil pH readings or samples
- Take pictures of upstream geology and plant biology
Webbing Failure
Images taken a few hours after being removed from a damp backpack. Webbing dye seems somewhat vibrant, but not uniform. The material felt soft and supple.
Images taken 24 hours after being removed from a damp backpack. Color seems more uniform. The material was hardening to a consistency of old leather
Images taken after fully drying follow in the next section.
Test Material and Values
| Test Number | Pounds force | Webbing type |
|---|---|---|
| 1 | 2,296.7 | Bluewater samples taken from Imlay |
| 2 | 2,280.5 | Bluewater samples taken from Imlay |
| 3 | 317.5 | Failed Cerberus webbing |
| 4 | 374.8 | Failed Cerberus webbing |
| 5 | 309.5 | Failed Cerberus webbing |
| 6 | 386.0 | Failed Cerberus webbing |
| 7 | 505.3 | Failed Cerberus webbing |
| 12 | 656 | Failed Cerberus webbing (Less UV damaged sample) |
| 13 | 1,198.9 | Failed Cerberus webbing (Less UV damaged sample) |
| Test Number | Force (pounds) | Extension (inches) | Webbing type |
|---|---|---|---|
| E1 | 2,409.9 | 2.530" | Bluewater samples taken from Imlay |
| E2 | 1,081.44 | 2.058" | Failed Cerberus webbing (Less UV damaged sample) |
Webbing Testing
Non-traditional tensile testing was performed on the broken strand. Initially the available testing method seemed problematic, however the failure mode of (non-control) coupons made the lack of tensionless bollard less concerning.
