The proposed bottom terminus of the JD
After the trail work concluded for the day, Rob, Phillip, Roy, Paul and I evaluated the options for landing the Jim Donnelly Trail down onto Hunting Hollow Rd without using the land below the dam, and keeping within the 10% grade limit.
We used pin flags and a clinometer. We investigated a few ideas, even entertained a couple of far flung and impractical ones, but ended up with essentially what is represented in these altered photographs. I used a photo editor to superimpose the proposed trail for visualization purposes.
Above is a photo looking taken from Hunting Hollow Rd looking N up towards the trail (and back towards the parking area). The flag line is at 10% and heads right up to where the trail bench arrives at the ridge nose just before the stock pond (where we are directed to not use the stock pond area terrain).
The trail could simply follow the flag line from the foreground. The 2 main problems with that are:
1. The place where most trail users will be coming and going from is behind the background of this photo, the parking lot. That means that a volunteer trail would spring up to shortcut the meadow.
2. The straight shot down to the road along the flag line drops mountain bikers right behind a tree and a blind turn on the road.
We decided on putting a turn in back towards the parking lot. The turn serves to slow riders down. The trail has a good view below to the road with great sight lines. Visbility is excellent. The turn gets people heading in the most likely direction they need to go, discouraging a short cut volunteer trail.
The next picture looks down from behind the fenceline from the exact location where the trail would cross the fence line. The black line superimposed is a rough approximation of the trail line. Of course there is a bush in the way that keeps you from seeing where it would lie on the hillside.
In the above photo there is a barbed wire fence which needs to be cut and crossed. On the right side of the frame is an organge flag. That orange tape (now removed) in the photo hangs from a tree. That tree was used as a fence post and grew around the wire, so that the wire is embedded around 3 inches deep. Further down the fenceline you can see a metal fencepost. The proposal here is to have the trail tread cross the fenceline at the blue tape. The orange flag tree would hold up the fence to the northwest, and the metal post would be staked down by a tensioned upper fence wire to keep the rest of the fence up and tight. Since grazing leases will not be renewed, we presume that there is no requirement to install a gate here. Because this is the only practical alignemnt for the trail, we presume that permission to cut this fence line will be permitted.
Next shows an idea of how the trail might look from a little bit past and below the fence. You can see the road below on the right. You also see how that if the trail went straight down the flag line (decribed in the first photo above) it would not be a good place to send cyclists on a finish of the trail Since the HH Rd is popular with equestrian traffic, it is definitely a risk. Instead you see the proposed trail aglignment make something like a 140 degree turn (switch-back) to the right.
.
Next is a visualization of the turn from above, with Diesel hiking up the proposed alignment.
And the next shot is of how the proposed alignment reaches the HH Rd. The photo was taken from the downhill leg of the switch-back. It heads right for a large distant and prominent Sycamore tree, and provides a good sight-line for any traffic on the road. The exit onto the road is preceded by a shallow flat turn to help slow bike traffic at this crucial location.
Next is a view of the proposed trail alignment taken from the edge of the road looking up towards the trail. This gives an idea of how it is arranged.
And the next is a concept sketch of the turn from above. There is plenty of room to make the turn radius bigger here, and we will have to. We will measure this terrain with a tape. If we get a serious rain storm we should go out there and see how the drainage is here, and what sort of soil is here. The trail is in a slump of what is probably an old slide from a super-saturated mass of soil. Judging from the rock exposures in the area, which are quite significant, it is likely that the soil is relatively shallow over massive bedrock. The bedrock doesn't absorb moisture. When the soil becomes super-saturated a layer of water and mud forms at the interface between rock and soil which allows the mass of loose dirt above to slide down the side-slope, usually in a slow and elastic motion. Another possible effect is one of localized ephemeral springs located by the crevices in the bedrock.
The area of the proposed turn shows some unusual erosion and the trail traversing to the fenceline above may be vulnerable to the same source of that erosion. But this is the only practical solution which avoids the stock-pond situation. So is it worth the risk? We think so. Future descriptions will show how this alignment meets the trail corridor above in a good and logical place.
Below is a sketch of a way to use the terrain in-situ to make a narrow radius version of the turn. This construction is proposed as the first stage of construction to make the corridor usable for travel, and not exactly the final shape of the turn. The lines in this view show how there is a depression where we located the turn.
This alignment proposal as portrayed here is our best alternative. There remains one more turn above everthing pictured here. That turn is a tough switch-back which needs a cribwall to build a turning platform upon (the rolling crown). We'll look at that proposal in depth, in a separate post.
One thing I wish to remark upon, in relation to the switchback near the pond, is that it will require the removal of a significant amount of dirt on the upper leg, excavating into the upslope. Depending upon the final design of that turn, we may end up with a lot of excess "fill" to dispose of somewhere. The alternative proposal for the lower turn, I mentioned above, would put a portion that fill to use in it's construction as compacted fill, which would be wheelbarrowed down.
There are certain choices to be made in the creation of the pond switchback. The main one, as I see it, is to decide how much are we willing to cut into the upslope to obtain enough swing-out to provide the large radius 12-14 feet (28 feet across)the trail needs to accomodate horse traffic. That is because that will determine how much, if any, retaining wall is needed. Paul L. made this observation on site.
Another consideration is that the existing trail bed above the pond swithback is, I estimate between 3% and 7% in grade locally, and so it may be possible to lower that bench to bring the approach to the switchback to a slightly slacker side-slope location. However, mature trees along that corridor are quite tight. Lowering the trail could require threading around trees in shallow turns and reversals, which would make it much more attractive than the current laser-straight line.
This drawing was hard to do for me, and it is wrong, but it tries to give an idea of what the turn at the bottom would look like. These sketches make the trail look like it is in the air, but it would be sunk down below the fluff of the grass of course. The most controversial aspect of this corner is that it will require fill dirt to create the rolling crown turning platform over a minor drainage area. We may be well advised to bury some perforated pipes in gravel at the bottom, and have them poking out of the downslope discretely to aid drainage. As mentioned earlier the fill would come from the turn above the fence line near the pond. If it is permitted, we would like to be able to use rock from the creek bed as well to form some of the edges and have something substantial to defend the inside of the turn.
Another consideration we may be required to observe by policy are ADA principles to construct the trail surface up to this turn, a relatively relaxed 2-5% grade section, ADA accessible.
Since we have generously received a lot of rain this week, we'll be able to examine this final turn location this Saturday and see if it is an active drainage. I think we'll be able to tell if water was flowing here. It is possible to go further ahead and make a flatter turn, but we feel the flow and visual appearance of the trail will be better in this location.
-Paul
Above is a photo looking taken from Hunting Hollow Rd looking N up towards the trail (and back towards the parking area). The flag line is at 10% and heads right up to where the trail bench arrives at the ridge nose just before the stock pond (where we are directed to not use the stock pond area terrain).The trail could simply follow the flag line from the foreground. The 2 main problems with that are: 1. The place where most trail users will be coming and going from is behind the background of this photo, the parking lot. That means that a volunteer trail would spring up to shortcut the meadow. 2. The straight shot down to the road along the flag line drops mountain bikers right behind a tree and a blind turn on the road.We decided on putting a turn in back towards the parking lot. The turn serves to slow riders down. The trail has a good view below to the road with great sight lines. Visbility is excellent. The turn gets people heading in the most likely direction they need to go, discouraging a short cut volunteer trail.The next picture looks down from behind the fenceline from the exact location where the trail would cross the fence line. The black line superimposed is a rough approximation of the trail line. Of course there is a bush in the way that keeps you from seeing where it would lie on the hillside.
Next is a visualization of the turn from above, with Diesel hiking up the proposed alignment. 
And the next shot is of how the proposed alignment reaches the HH Rd. The photo was taken from the downhill leg of the switch-back. It heads right for a large distant and prominent Sycamore tree, and provides a good sight-line for any traffic on the road. The exit onto the road is preceded by a shallow flat turn to help slow bike traffic at this crucial location.
Next is a view of the proposed trail alignment taken from the edge of the road looking up towards the trail. This gives an idea of how it is arranged.
And the next is a concept sketch of the turn from above. There is plenty of room to make the turn radius bigger here, and we will have to. We will measure this terrain with a tape. If we get a serious rain storm we should go out there and see how the drainage is here, and what sort of soil is here. The trail is in a slump of what is probably an old slide from a super-saturated mass of soil. Judging from the rock exposures in the area, which are quite significant, it is likely that the soil is relatively shallow over massive bedrock. The bedrock doesn't absorb moisture. When the soil becomes super-saturated a layer of water and mud forms at the interface between rock and soil which allows the mass of loose dirt above to slide down the side-slope, usually in a slow and elastic motion. Another possible effect is one of localized ephemeral springs located by the crevices in the bedrock. The area of the proposed turn shows some unusual erosion and the trail traversing to the fenceline above may be vulnerable to the same source of that erosion. But this is the only practical solution which avoids the stock-pond situation. So is it worth the risk? We think so. Future descriptions will show how this alignment meets the trail corridor above in a good and logical place.Below is a sketch of a way to use the terrain in-situ to make a narrow radius version of the turn. This construction is proposed as the first stage of construction to make the corridor usable for travel, and not exactly the final shape of the turn. The lines in this view show how there is a depression where we located the turn. 
