The final analysis was performed on a random sample of about 10% of the setting design while the preliminary analysis was performed on the entire setting design. The two designs differ by the fact that the span distances in the final setting design were constrained by the unit boundaries (see Figure 12.1). The goal for the final design was to see if payloads could be maintained while staying within these boundaries. When the profile lengths were shortened a higher tailhold height, usually of 40-ft, was required for the minimum deflection over the topography. Regardless of the height of the tailhold, certain spans could not reach the required length while maintaining the desired payloads. In this case the span length was extended enough to gain the needed deflection at the expense of the desired payload weight.

Figure 12.1 Map of the Washougal Planning Area Showing the Final Harvest Unit Boundaries

Tables 12.1 and 12.2 represent the number of profiles categorized by payloads and tailhold heights for the preliminary and final setting designs. In the preliminary design the majority of the spans have a 2-ft. tailhold with the majority of these spans carrying a payload of over 5000 lbs. In the final analysis the majority of the spans have a 40-ft. tailhold. The majority of these spans also carry a payload of over 5000 lbs. but there is a noticeable increase in the spans carrying a payload of less than 4500 lbs. It was found that in many cases the payloads could be kept near the desired weight when the tailholds were within the unit boundaries. In the cases where payload weights are poor the spans would need to be lengthened beyond the unit boundaries to gain the deflection needed to maintain the desired payloads.

Table 8A.6 recommends the minimum diameters for West Coast Douglas fir tail trees. By referring to this table, the profiles created in PLANS can be further analyzed. In the final PLANS analysis, a tailhold height of 40 feet is required most frequently. If a ¾ inch skyline is used then the diameter for the tailhold tree should be 17 inches. If a 1-inch skyline is used then the diameter for the tailhold tree should be 19 inches. Lower tailhold heights means that small diameter trees can be used. If the larger tailholds are required more time is needed for the trees to grow so they can qualify to be these larger tailhold trees. All PLANS analysis in this report was based on the current timber size for the Washougal Planning Area.

*The one profile with the ten-foot tailhold height drops the average span length by over 130-ft when figured in as a straight average.

Tables 12.3 and 12.4 represent the average length, in feet, of profiles categorized by payload and tailhold heights for the preliminary and final setting designs. From Table 12.3 to Table 12.4 there is a decrease in average profile lengths for each tailhold height and their designated payload weights. This decrease in span length also reflects a decrease in the average yarding distance (AYD) for the entire setting design. Since harvest costing is directly affected by AYD a lowered AYD reflects a lower variable harvesting cost for all the harvesting systems.

Each setting in the planning area has been designated with a specific type of harvest system. These systems are central tower, continuous (swing yarder), ground (skidder) and helicopter yarding. Figure 12.2 shows the settings and the type of harvest system each has been assigned to receive. Central tower yarding harvests xxx% of the total harvesting area. Continuous yarding harvests xxx%, ground systems harvest xxx% while helicopter has been designated for xxx% (see Figure 12.2). The actual amount of harvesting done by helicopter will be lower because some of these areas do not have the timber to cover the costs of a helicopter logging operation.

Figure 12.2 Map Showing the Harvest Methods for each Harvest Unit

Table 12.5 represents the average unit area and average yarding distance (AYD) for each harvest system. These averages were taken from a sampling of the values that were produced in SNAP (Scheduling Network Analysis Program). All harvest systems approximately have the same amount of average acreage and average yarding distance. The average setting area for the entire planning area is about 18 acres with and AYD of about 634 feet. A correlation between area and AYD can not be assumed. A harvest setting unit can have its profiles arranged so there is a large area with a small average yarding distance and vice versa. A large AYD does not necessarily mean a large area.

Table 12.6 represents the average values for unit area and average yarding distance for different harvest systems that are selected in the first five years (period 1). In this period the skidder and tower systems are used the most. This trend will be true for each five-year period due the large amount of settings that have been designated to be harvested with a central tower. In the first period the average setting size is about 13 acres with an AYD of 502 feet.

Table 12.7 represents the values for volume and acreage for each harvest system for periods one through five. For every period the central tower harvests the largest amount of volume and acres. The total volume, for all systems, harvested in each period has been specified by SNAP to be about 20,000 MBF. Helicopter logging begins in period 3. This could be because SNAP believes that the present timber conditions will not be able to cover the cost of helicopter logging. SNAP is allowing the timber to grow for 15 more years when it should have more volume.

A random sample of 40 settings was taken from the entire watershed to be the final PLANS analysis. The 40 settings were ranked according to direction, distance and topography of yarding. Ranking was based on utility values given in Setting Design Evaluation Incorporating Pacific Northwest Loggers' Preference by Dean Rae Berg and Peter Schiess.

The silviculture regimes evaluated are clearcut, aggregate cut, and dispersal cut. Clearcut setting utility values are based on direction, topography, and distance combined with direction. Aggregate and dispersal utility values are based on direction and distance. Attributes preferred by loggers are given higher utility values. Utility values can not be compared between silviculture regimes and each regime is given a different range of attribute utility values.

Setting utility values are determined by multiplying the set utility value by the percentage of the attribute that is present in the setting. For example in a clearcut silviculture regime, a setting may have 76% of its yarding in the uphill direction, 4% in the sidehill direction, and 20% in the downhill direction. Table 12.8 and 12.9 show utility values for the different types of silvicultural regime attributes. For clearcuts the given utility value for uphill yarding is 57, sidehill is 22 and downhill is 6. The direction attribute utility value for this setting is (0.76*55)+(0.04*22)+(0.20*6) = 45.4.

For clearcuts, settings with high attribute utility values could have a combination of uphill yarding up to 1000 feet and even topography for uphill/downhill yarding. Settings with medium attribute utility values could have a combination of sidehill yarding with even topography, uphill/downhill yarding with broken topography, downhill distances less than 500 feet, and uphill distances greater than 1000 feet. Settings with low attribute utility values could have a combination of downhill yarding greater than 500 feet and sidehill yarding with broken topography.

High attribute utility values are given to settings with yarding in uphill direction and all yarding distances less than 500 feet. Medium attribute utility values are given to settings with downhill yarding and yarding distances between 500 and 1000 feet. Low attribute utility values are given to settings that have sidehill yarding and yarding distances greater than 1000 feet.

Based on logger's preference the settings designed for this watershed are most preferable in clearcut situations. The majority of the settings have yarding in the uphill direction with even topography and distances no greater than 1000 feet.

Setting attribute utility values for single profiles are shown in Table 12.9. Half of the settings evaluated are preferred for clearcut and the other half fall in the low range for clearcut. Half of the settings are also preferred for aggregate and dispersal cuts with the other half falling in the mid to low ranges. Single profiles have more mobility, which gives designers the opportunity to move the swing yarder where sidehill is limited and uphill is maximized.

Based on logger's preference, the half of the settings designed for this watershed are preferred for every silvicultural regime. The same percentage of settings is preferred for clearcut, aggregate cut and dispersal cut. Therefore, single profile spans are the most versatile in the usage of the three different silvicultural regimes.