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Bon Tempe Reservoir

Greg Ehrensing Memorial Volunteer Event

Date: Dec. 5 - 6, 2020
Location: Fairfax, CA
Event Director: - 415.456.8118
Course Setter: Dennis Wildfogel
Type: C; Greg Ehrensing Memorial Volunteer Event; NO BEGINNER COURSES; LIMITED ATTENDANCE; RESERVATIONS REQUIRED

Course Setter’s Notes

The maps are printed at a scale of 1:5,000 so you can see all the detail. Objects are therefore closer than they might appear. Be sure to read the Map Notes below.

Each of the courses has a map exchange. See the Event Notes for details.

On all the courses, there is a control in a small depression that is near a gully filled with thorny vegetation. You have to cross that gully to get to the next control. A series of short streamers has been hung to lead you from the depression to a good place to cross the gully.

Since we are not permitted to use banners at Bon Tempe, the Finish consists of two control stands with control flags on them and FINISH units attached to the top. With SI AIR+, you can just wave your E-stick over one of the FINISH units to record the end of your run.

The control description “Tree, ruined” refers to a standing, dead tree.

There are several road crossings. Any time you are about to cross a paved road, be alert to the possibility of oncoming cars and bicycles. Bicycles are the bigger danger, especially on downhills, because they often greatly exceed the posted speed limit of 15 mph, and you don’t hear them coming.

As is the custom with maps printed at 1:5,000, controls are at least 30 m apart. Note, though, that there are several pairs of controls that are not much further apart than 30 m.

The courses are designed to be Classic in distance but to have the nature of a Middle course, which means careful map reading and full concentration will be rewarded. The terrain is quite benign and also full of detail, which means the challenges will be as much mental as physical. You can be aggressive in going mostly straight, but there are still mini-route choices: look for routes that allow you to move unimpeded and for routes along which you will have the confidence to move forward with little hesitation. For example, ribbons of clearings are often excellent choices for both those reasons.

There are a lot of controls out there! You will undoubtedly see many controls that are not the one you are trying to get to. Don’t just run to a control if you see one​—​it may not be the one you want. Read the map, and the clue sheet.

Covid-19 Considerations

While on your course, you should have a bandana or mask around your neck, and pull it up over your mouth and nose any time you get near another orienteer or any other park visitors. (See the section Wear A Mask in the Event Notes.)

You will spend very little time on trails. However, you will cross several trails, so you need to keep on eye out for other park visitors when you do. If you do encounter other park visitors, give them a wide berth​—​you’re equipped to run off-trail and they’re not. And, of course, pull up your mask.

When you punch a control, immediately move at least 5 meters away before planning your next route, so as to give other incoming orienteers room to punch. For virtually every leg, a good strategy is to start off going straight towards the next control; so there’s no need to linger when you punch, just start heading in the direction of the next control and figure out things while you’re going. Challenge yourself to keep moving, whether you’re walking or running. The courses are designed to make that possible.

After you “punch” the FINISH (by just waving your SI AIR+ over it), immediately move at least five meters away even if you feel like collapsing. Catch your breath and get your mask on before going to the Download station.

Due to the pandemic, there are no water stops on the course.

If you happen upon an injured orienteer, you are obligated to abandon your course to assist the injured person. Given the pandemic, you might be reluctant to approach this person too closely if it’s not a life threatening situation. In that case, a reasonable course of action would be to go back to the Assembly Area and seek assistance. If you do that, try to find somebody to stay with the injured person.

Map Notes

All the course maps have been printed at a scale of 1:5,000.

Green dots are all small but prominent trees (not bushes). Individual bushes are not mapped. Note: On some other BAOC maps, green dots represent bushes rather than trees. As the green dots on this map are extremely useful for navigation, please keep in mind that they represent small trees, not bushes.

Green ×’s are standing, dead trees, almost always with some limbs still intact. They look like they’ve died of a disease, not from a lightning strike.

Tight green hatching (i.e., vertical stripes) can either be a patch of bushes or a small area of broken limbs. The latter appear to be former green ×’s that have completely deteriorated.

Light green and medium green are used only in forested areas. Patches of bushes in open areas that impede movement are represented by green hatching, widely-spaced stripes if it’s not too difficult to get through, tightly-spaced if it is more difficult. Some forested areas are marked with green hatching rather than solid green because visibility is good despite the difficult running.

Brown ×’s are rootstocks; stumps are not mapped.

All the yellow on the map represents rough open. Unlike many of our other venues where rough open can be slow running (e.g., tall grass, or sharp thistles, or rough ground from grazing cows), all the rough open at Bon Tempe is pretty-good to good running.

Quite a few rock features have been added to the map; most of the boulders are between one meter and half a meter high, and most of the mapped stony ground isn’t very extensive. Nevertheless, both of these rock features are very noticeable in the terrain.

The size of the green circles (prominent trees), green ×’s and brown ×’s has been reduced, because they were taking up too much space. Some of the green ×’s are a little hard to see against a background of green stripes. The symbols for boulders and stony ground have not been reduced in size, so those features stand out on the map more than they stand out in the terrain.

The difference between green unfilled circles and green dots: More than anything it’s the width of the trunk and the width of the canopy; some of the green dots are tall but skinny trees. But in many cases it depends on what else is around. If, say, there are five trees fairly close together in a large meadow, all skinny, but one of them is considerably bigger than the others, then that one is probably mapped with a green circle, even though if it had been in an area with many larger trees it would have been mapped as a green dot.

When a tree is at or near the edge of the forest, it can be difficult to discern whether it is mapped as part of the forest or as a distinct tree. If I found myself looking around trying to figure out which tree was the one mapped as a prominent tree, then I figured it wasn’t sufficiently prominent and changed it to be part of the forest, that is, if its canopy was touching the canopies of one or more other trees. Navigation on the courses for the 2020 event does not depend on you being able to make this distinction.

When two trees are alone together in a meadow and their canopies are just barely touching: is that a copse (white patch) or two prominent trees? If the canopy looks like one continuous canopy, and there is clearly more than one trunk, then it’s mapped as a white patch.

This area has several prominent gullies. In some places, the gullies are filled with nasty vegetation, making those places poor choices for crossing the gully. Unfortunately, the orienteering map symbol set doesn’t allow for showing that there is vegetation in a gully. A good rule of thumb on this map is that unless there is a clearing on both sides of the gully, it’s probably not a great place to cross. Also see the note above about one particular gully crossing.

This map uses the “rough open with scattered trees” symbol in quite a few places (something rarely used on Bay Area maps). It denotes an area where there is nothing particularly prominent, but there are too many little things to map and keep it readable. You will notice these patches in the terrain, and you might notice the symbol on the map, but you might not recognize what you’re looking at. The symbol is a regular array of white dots against a yellow background (the top graphic at the right). The problem is that when there are just a few dots, it is easy to think that those little white dots are mapping specific individual round areas of forest (e.g., the middle graphic at the right). It won’t matter much if you don’t quite figure out what is going on, but I thought you should be forewarned. In one place you will see a large patch of this symbol but overlaid with tight green vertical stripes (e.g., the bottom graphic at the right). However, it’s hard to notice the white dots since they’re covered by the green stripes. What is being represented is a large open field that has become choked with bushes, with an occasional tree sticking up.

Some stairs are mapped on one of the trails. I was not familiar with that symbol, but it should be obvious what it represents when you see it.

Road cuts sometimes create earth banks on one side and/or drop-offs on the other. These are often not mapped as that would add too much clutter. That shouldn’t cause any confusion.

The lake level is presently much lower than mapped, exposing 30 m more shoreline in some places. I doubt anyone will notice on the 2020 courses.

Many, many revisions have been made to the small part of the Bon Tempe map where most of this year’s controls will be. This is not a new area: most Bon Tempe events have had one to three controls in this area. However, because the area was out of bounds to us for many years, the area was not field checked when the current map was made in 2015. The features represented on that part of the map were primarily gleaned from satellite photos. The recent field checking has updated many vegetation changes and added numerous point features, particularly small rock features. Contour features that were not apparent from the 5-meter contour interval have also been added in a number of places. As a result, this area of the map should now support courses that require detailed map reading.

Special Thanks

Bob Cooley and Bill Cusworth provided extensive, expert assistance with the map revisions. I would have been lost without them. My vetters, Steve Gregg and George and Leslie Minarik, really put their hearts into it, providing invaluable feedback and offering thoughtful suggestions. Any remaining deficiencies in the map or courses are strictly my responsibility.