Harry Allen Trail & Eldgridge Grade - Marin Water District

This is a somewhat strenuous hike with only a few flat stretches, we spent about 3 hours on the trail, but also took a slightly different route than map shows at end to climb back up to Crown Road where cars were parked, but that trail is not on Google Maps currently.  Also despite being strenuous, is otherwise a good hike for sunny weather as there's only a few sections with full direct sunlight.

Azalea Hill to Bon Tempe Lake, Marin County, California

Recent flooding closed the access road to Bon Tempe Lake Trailhead at Bon Tempe Dam, so we parked at the Azalea Hill Trailhead and hiked south to the Bon Tempe Lake Trailhead where you normally may park.  We did a loop hike from there, and using the Marin Water District Maps there are lots of options to extend.

Marin Municipal Water District: Rock Springs to Mt. Tam West Peak Loop

5.6 mile loop - Constantly varying grade up and down looping around upper parts of Mount Tam without venturing too low in elevation near the reservoirs.  Northernmost branch of hike on High Marsh and Kent Trails (north of Potrero Meadow) is strenuous down out and up back, and could easily be cut out by using Laurel Dell Road without venturing north of Potrero Meadow.

Marin Municipal Water District & Mount Tam North Side

Bon Tempe Dam to Lake Lagunitas to Collier Spring to Hidden Lake to Alpine Lake and back to Bon Tempe Dam - 10.0m loop

Collier Spring Trail is a strenuous uphill climb the north side of Mount Tam and then it is mostly downhill back to Alpine Lake, otherwise the route is moderately flat around the reservoirs.

Mount Tam East Peak, Marin County, CA

Mount Tam East Peak from Rock Springs - 7.5m out (up) and back (down)

Cataract Falls, Fairfax, CA

Marin Municipal Water District - 3.5m out (down) and back (up)