C04n_11 Least Cost Road Standards.pdf

Least-Cost Road Standards for Timber Sale Specified Roads

Forest Service Manual 7730.2 requires operaƟon and maintenance of NaƟonal Forest System roads in a manner that provides for:

1. Safe and efficient travel;

2. Access for the administraƟon, uƟlizaƟon, and protecƟon of NFS lands; and

3. ProtecƟon of the environment, adjacent resources, and public investment.

Northern Region NaƟonal Forests are tasked with meeƟng this manual and handbook direcƟon, along with relevant state law and policy, while implemenƟng aspects of its mulƟple use mandate through commercial Ɵmber harvest. This memo is intended to provide guidance for determining appropriate work to be included in Specified Roads packages within Ɵmber sale contracts in accordance with Forest Service direcƟves.

Design Standards

Per Forest Service Handbook, design standards for Specified Roads should be the least-cost needed to facilitate safe haul and miƟgate damage to naƟonal forest resources. (FSH 2432.34a_3: “Pursuant to the NaƟonal Forest Roads and Trails Act of 1964, plan for the least-cost road needed to meet the resource objecƟves for the sale.”). Forest Service Handbook direcƟon is intended to be consistent with the following list of laws and regulaƟons:

36 CFR PART 212 – TRAVEL MANAGEMENT: 212.10 Maximum economy NaƟonal Forest System roads. The Chief may acquire, construct, reconstruct, improve and maintain NaƟonal Forest System roads within and near the NaƟonal Forests and other lands administered by the Forest Service in locaƟons and according to specificaƟons which will permit maximum economy in harvesƟng Ɵmber from such lands tributary to such roads and at the same Ɵme meet the requirements for protecƟon, development, and management thereof and for uƟlizaƟon of the other resources thereof.

NaƟonal Forest Management Act of 1976 SecƟon 8"(c): Roads constructed on NaƟonal Forest System lands shall be designed to standards appropriate for the intended uses, considering safety, cost of transportaƟon, and impacts on land and resources." (16 U.S.C. 1608)

NaƟonal Forest Roads and Trails Act; Act of October 13, 1964, Road ConstrucƟon, Sec. 4.: The Secretary is authorized to provide for the acquisiƟon, construcƟon, and maintenance of forest development roads within and near the NaƟonal Forests and other lands administered by the Forest Service in locaƟons and according to specificaƟons which will permit maximum economy in harvesƟng Ɵmber from such lands tributary to such roads and at the same Ɵme meet the requirements for protecƟon, development, and management thereof, and for uƟlizaƟon of the other resources thereof.

Culverts

The following criteria are intended as guidance for determining suitability of replacing exisƟng culverts via Specified Road work within a Ɵmber sale contract:

Crossings exhibiƟng a high likelihood of failure during a Ɵmber sale should be replaced.

Crossings in drainages that have recently incurred disturbance such as wildfire, mass wasƟng

(e.g. debris flows or landslides), or flooding may require upgrades to facilitate safe haul during the Ɵmber sale.

ExisƟng culverts sized to accommodate a 50-year peak flow event (Q50) or greater with a headwater to depth raƟo of 0.8 or less and showing no evidence of imminent failure should generally not be considered for replacement.

For permanent culverts that do not meet the above criteria: Where a crossing structure has a probability greater than 0.25 of overtopping or diverƟng stream flows (see table below) during a Ɵmber sale, the crossing should be upsized to meet manual, handbook, and Forest Plan direcƟon. For example, if an exisƟng culvert can pass Q25 and the Ɵmber sale is planned for five years, the probability of overtopping is 0.18 and the culvert does not need to be replaced for hydraulic purposes.

Existing crossing design flow flood event

Years of anticipated timber sale road use

Q5 (5 yr flood event)

Q10 (10 yr flood event)

Q25 (25 yr flood event)

1 0.2 0.1 0.04 2 0.36 0.19 0.08 3 0.49 0.27 0.12 4 0.59 0.34 0.15 5 0.67 0.41 0.18 6 0.74 0.47 0.22 7 0.79 0.52 0.25 8 0.83 0.57 0.28 9 0.87 0.61 0.31

10 0.89 0.65 0.34 Table 1. Probability of flood inundaƟon for crossings designed to pass 5-year, 10-year, and 25-year flows, respecƟvely.

If a culvert is idenƟfied for replacement via Specified Road work in a Ɵmber sale contract, the culvert should be sized according to least-cost needed to facilitate safe haul while meeƟng regulatory requirements. Forest plans in R1 typically require culverts to accommodate a 100-year flood event.

Forest Service Handbook 7709.56b Chapter 60 provides Ɵered direcƟon related specifically to road-stream crossings and AquaƟc Organism Passage (AOP). Crossings are to accommodate natural passage of debris, sediment, and aquaƟc species and minimize stream channel modificaƟon. Chapter 65.1 specifically notes that “AquaƟc organism passage and ecological connecƟvity is the goal and second only to user safety in design priority for crossing streams that provide habitat for aquaƟc life.” The importance of AOP design should be acknowledged. However, it consƟtutes a higher standard than the least-cost needed to facilitate haul, subsequently if AOP designs are included in Specified Road work then provisions shall be made in the Ɵmber sale contract for compensaƟng the Purchaser for the addiƟonal costs (e.g. contributed or supplemental funds).

Roadway Surfacing ConstrucƟng roadway surfacing can be a very costly work item and alternaƟve soluƟons should be considered first. FSH 7709.56_CH47.2 recommends using the decision tree shown in Figure 1 for determining the need for surfacing. The following bulleted list relates the decision tree criteria and other FSH language with Ɵmber sale Specified Roads.

Ruƫng suscepƟbility of the roadway surface – Ruƫng can oŌen be miƟgated by operaƟng during dry season or frozen season, which usually coincides with the Normal OperaƟng Season.

(NOS)

Resource damage – Resource damage on naƟve surface roads can oŌen be miƟgated with frequent drainage features, dust abatement, and road maintenance during haul periods. Adding roadway surfacing Including aggregate surfacing may be an appropriate treatment for the following situaƟons:

o Specified Road segments within 300 feet horizontal distance of a waterbody (e.g.

intermiƩent or perennial stream, wetland, pond, or lake) may require addiƟonal surfacing if roadbed structure strength (e.g. ruƫng) is anƟcipated to cause surface drainage problems during the NOS.

o It may be appropriate to include addiƟonal surfacing on Specified Road segments located in a watershed where there is a Clean Water Act waterbody impairment (Class 4a or 5 on the 303(d) list), it has been demonstrated via the applicable NEPA decision document that the waterbody impairment could be affected by sale operaƟons, and there is potenƟal for the road segment to adversely affect the impairment status.

Engineering should coordinate with hydrology regarding treatment specifics.

o Aggregate surfacing may be an effecƟve way to improve tracƟon or control erosion on steeper grades (eg greater than 12% grade). In these cases, 1 to 2 inches of aggregate is usually adequate for the steeper grades. (FSH 7709.56_47.2(e)

Figure 1. Surfacing decision flowchart from EM-7170-16

(STP) Surfacing Thickness Program – Forest Service developed computer program developed in 1989 for calculaƟng aggregate surface thickness requirements. STP is no longer used.