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Rex Trail Prescription Report

In 2013, the Department issued a contract to produce a Prescription Report for four discrete sites of the Rex Trail, each approximately 1/4 to 1/2 mile in length and within the first nine miles of the trail (see map). These sites were selected based on the fact that they were degraded, potentially constructible, and potentially informative for possible treatment of other degraded sections of the trail with similar site conditions. In an attempt to collect a wide range of treatment options, the contract specified the following:

  • A prescription report will be prepared for each of four sites.
  • Each site-specific prescription report will describe 2 options for each level of use with a recommended option clearly identified. The use levels are as follows:
    • Use 1 -ATVs up to 1500 lbs and rubber tracked rigs up to 25000 lbs (steel cleats allowed, use Nodwell RN-110 specs for ground pressure), up to 10 feet wide.
    • Use 2 -Above + large wheeled vehicles up to 15000
  • For the above use levels, assume ground thawed usage of the following frequency where appropriate:
    • ATV's - 3000 passes (1500 round trips)
    • Tracked Vehicles - 100 passes
    • Wheeled - 100 passes - usually lifted 4 wheel drive vehicles with large tractor type tires
  • For the above use levels, assume frozen ground usage of the following frequency where appropriate:
    • Snowmachines - 1000 passes (500 round trips)
    • Limited passes of large equipment, including dozers up to D10 size, large wheeled military vehicles- 100 passes (50 round trips). Plowing may precede this type of winter use.
  • Expected goal for options - support prescribed use for a period of 5-10 years with limited maintenance without the necessity for unplanned braiding and minimal rutting (not to exceed 1 foot) over the specified period. Option must specify anticipated lifespan.
  • Options may include treatment of existing route to support given use level, reroute for one or more use type, or reroute for all uses.

These specifications were chosen in an attempt to encompass existing and pre-restriction use of the Rex Trail, as well as result in a variety of treatments that didn't just encompass the "Cadillac" (highest cost) treatments.

Based on criteria of limited stability that DNR defined for the report, the current alignment of eastern Rex trail is unsustainable for current levels of use. Short of implementing a long-term complete seasonal closure of the current trail, upgrading the whole alignment to modern road standards, or large-scale rerouting of the alignment, spot treatments of the worst sections of trail to make the entire route passable may provide temporary solutions.

An excerpt from the report is as follows: "The solutions provided in this report represent a hybridization of trail hardening techniques and applications that have been successfully used on other sites in Alaska. However, there is no known direct precedent for long-term monitored trail hardening combining this varied terrain, use intensity, combination of user groups (ATV to semi-truck), and seasons of use (winter-summer); therefore, these prescriptions are somewhat of a site specific test case. Social engineering will be an important part of the success of any trail upgrades, both built into the alignment itself (visual buffers, width) as well as education of user groups and signage on the trail itself."

Based on the high variability of terrain and soil conditions, recommended treatments also vary. There is no single treatment method which is applicable to all degraded areas if resource optimization is a goal. Various treatments are described and recommended in the report, depending on site.

As noted above, a total of four options for each site were provided: two options for each of two use types as defined below.

  • Use Type 1: ATVs and tracked rigs less than 25000 lbs.
  • Use Type 2: Uses from Use Type 1, plus wheeled vehicles less than 15,000 lbs.

Costs noted below were estimates only with pricing from 2013 and do not include DNR oversight, inspections, mobilization/demobilization, per diem, fuel, or other logistics, which vary depending on site conditions and technical approach. It should be noted that the 2014 contract for Site 4 Type 1 a. (estimated at $42,161 without the additional costs), was completed at a cost of $93,780 once all costs (except DNR staff time) were accounted for.

Site 1:

  1. Use Type 1
    1. Option 1: Combination of ditch and elevate 12' wide up the middle of the current alignment; intermittent gravel causeway w/culverts through ponded sections: Cost estimate - $129,231 to $152,308 depending on inclusion of gravel cap
    2. Option 2: Reroute trail to south and construct tread with ditch and elevate: Cost - $77356
  2. Use Type 2
    1. Options/costs same as noted above

Site 2

  1. Use Type 1
    1. Option 1: Ditch and elevate with culverts and a gravel cap: Cost - $48,837
    2. Option 2: Primitive road/causeway: Cost - $254,195
  2. Use Type 2
    1. Options/costs same as noted above

Site 3

  1. Use Type 1
    1. Option 1: Ditch and elevate 12' wide with an imported gravel cap intermittent with Geoblock installation up the middle of the current alignment using the best possible ground: Cost - $ 165,976.
    2. Option 2: Primitive gravel road/causeway: Cost - $289,100
  2. Use Type 2
    1. Options/costs are the same as above.

Site 4

  1. Use Type 1
    1. Option 1: Realign the trail south (for ATV's and small tracked rigs) and ditch and elevate 6' wide with a gravel cap, underlain by corduroy -larger tracked rigs would continue to utilize the existing trail: Cost - $42,161
    2. Option 2: Realign the trail south (for ATV's and small tracked rigs) and ditch and elevate 6' wide without a gravel cap or corduroy - larger tracked rigs would continue to utilize the existing trail: Cost - unspecified, but assumed at ~ $20,000.
  2. Use Type 2
    1. Option 1: Realign the trail as above, nothing additional done to existing tread: Cost of option chosen above - no additional cost.
    2. Option 2: Primitive gravel road/causeway without trail realignment: Cost - $474,980

Prescription Report

Rex Trail Index
Trail Braids in Winter