MP 237 238: the top of the bottom switchback For reference this section of U S Highway 40 has been called the top of the bottom switchback on the Grand County side of the Pass. It is here that the proposed north portal of the Berthoud Tunnel would have come out. There are several avalanche chutes found between these two mileage posts. These chutes are referred to as the 300 s. They include the bottom of the No Name Banks, Big Crib and the Spruce Banks. Route Mile Marker X Y Longitude Latitude 1 U. S. Highway 40 237 434966.20 4409223.70-105.759999 39.830542 238 435214.73 4410793.11-105.757250 39.844683 The above drawing was taken from a feasibility study report given to the author by CDOT showing the location of the proposed Berthoud Tunnel. 1 Taken from the Colorado Department of Transportation s website: http://apps.coloradodot.info/dataaccess/highways/index.cfm?fuseaction=highwaysmain MP 237 238: The top of the bottom switchback (PAW 2012) 1
This old U. S. Forest Service photograph shows the location of the Twoforty, Twin Cones, No Name Banks, Big Crib, Spruce Banks, and Little Crib. Date: Unknown Avalanche Path: No Name Banks Location: 237 CDOT crews and Avalanche Forecasters have named the portion of highway between the switch back at mile 236.8 to the switch back at mile 238, the 300s. The Spruce Banks, the Big Crib and the No Name Banks avalanche areas are included in the 300s. Terrain Specifications: Starting Zone elevation: 9,920 ft. Runout Zone elevation: 9,840 ft. Length of path: 140 ft. Vertical fall to roadway: 80 ft. Maximum vertical fall: 80 ft. Avalanche Data: Length of road affected: 2,200 ft. MP 237 238: The top of the bottom switchback (PAW 2012) 2
Average avalanche activity affecting road/year: 3.0 Control Methods: Mobile control: None Comments: This cut slope is the lowest in a series of bank slides on the west side of Berthoud Pass. The use of the snow blower aids in stabilizing all the banks. During periods of heavy snow this cut bank area can slide and usually covered the west bound lane. Slides in this area can also reach the highway during the warm days of spring. No Name bank taken from the upper portion of the cut bank No Name Bank taken from lower portion of cut bank at mile 237 MP 237 238: The top of the bottom switchback (PAW 2012) 3
Avalanche Path: Big Crib As stated above, this section of US Highway 40 is referred to as the 300 s. The Spruce Banks, the Big Crib and the No Name Banks are included in the 300s. Location: 237.3 Terrain Specifications: Starting Zone elevation: 10,260 ft. Runout Zone elevation: 9,840 ft. Length of path: 108 ft. Vertical fall to roadway: 320 ft. Maximum vertical fall: 420 ft. Avalanche Data: Length of road affected: 200 ft. Average avalanche activity affecting road/year: 3.0 Control Methods: Mobile control: None Comments: A steep narrow gully that begins at the highway above the switchback at mile 238.3 and meets the highway below the switchback at 237.3. Because this track is between the two portions of the highway, it is very popular with backcountry skiers and snowboarders, and they occasionally trigger avalanches that impact the highway. In the spring during the heat of the day wet avalanches are common. Big Crib avalanche area taken at runout zone on highway Avalanche Path: MP 237 238: The top of the bottom switchback (PAW 2012) 4
Spruce Banks The Spruce Banks, the Big Crib and the No Name Banks avalanche areas are included in the 300s. Location: 237.7 Terrain Specifications: Starting Zone elevation: 10,060 ft. Runout Zone elevation: 10,000 ft. Length of path: 108 ft. Vertical fall to roadway: 60 ft. Maximum vertical fall: 60 ft. Avalanche Data: Length of road affected: 1,300 ft. Average avalanche activity affecting road/year: 3.0 Control Methods: Mobile control: None Comments: Periods of heavy snow fall will trigger avalanches that normally cover the west bound lane. During warm spring days wet avalanches are common. Upper portion of Spruce Bank taken from mile 237.9 MP 237 238: The top of the bottom switchback (PAW 2012) 5
Lower portion of Spruce Bank MP 237 238: The top of the bottom switchback (PAW 2012) 6