North Ridge Trail Improvements!

You may notice something new at the top of the North Ridge Trail! The old trail was realigned to improve user experience, tread, and drainage. Read more about the project below.

 

The majority of our trail maintenance focuses on keeping vegetation out of trail corridors and maintaining drainage features along the trail. But occasionally, a section of trail with an underlying design issue evolves into a more significant problem spot. This is was the case for the top of the North Ridge Trail as it entered Rotary Meadow.

 

Steep Segment of North Ridge Trail for proposed realignment

 

The tread became rutted and rocky and winter rains acted to accentuate the erosion that was occurring. Given the steepness of this section (>20% grade), we were confident that typical tactics of constructing water bars or other drainage features wouldn’t be a sustainable solution. In this case a more substantial change is needed – a realignment was in order.

 

With steep sections of trail, often we can find an alternative route that extends the length of trail, which has multiple benefits. For a given amount of elevation change, it increases the length of trail and consequently reduces the grade, making for a more manageable trail. In addition, a realigned trail segment allows new contours and drainage features to be introduced, so that water can be dispersed instead of channeled.

 

This approach is not without challenges. Oftentimes we must balance improvements to our trails with the health of well-established habitat, which was certainly the case for this segment of trail. The Rotary Meadow was first planted 15 years ago and represents the most established habitat cultivated in the Mount Sutro Open Space and is an important resource to maintain. So we were tasked with planning a realignment that minimally impacted the nearby habitat resources, while achieving our goals for the trail route.

 

Proposed realignment route relative to existing trails

 

We were able to identify a route that weaved between and around a number of native shrubs (red elderberry, coffee berry, wax myrtle, and silk tassel) and have minimal impact on the sensitive plants in the area. This would require constructing log or rock retaining walls, transporting a massive amount of gravel, rock, and soil for fill, and compacting it all to form our new tread. We were blessed with two massively productive work days in June, and made sufficient progress to make the realignment passible for trail users.

 

Wheelbarrows using old trail to shuttle materials while the realignment takes shape

 

We are happy to announce the realigned route is open for use, and the previous alignment is closed. We will spend one additional work day in July to make fine adjustments to the flow of the trail. As with any new section of trail, the tread tends to change and wear in over time, so we will keep a close eye on this section to make sure our improvements last for years to come!

Realignment to the right and closed section to the left

 

Thanks to our June volunteers for their significant efforts to the realignment!

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November 5, 2019

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Sutro Stewards is a project of the San Francisco Parks Alliance, a 501(c)3 California nonprofit public benefit corporation.

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