Cal Poly Professors work Pro Bono with Land Conservancy to develop Pismo Preserve

March 19, 2018

Civil Engineering professors Judd King and Nephi Derbidge are working with The Land Conservancy of San Luis Obispo to develop the 880-acre Pismo Preserve.

Cal Poly professors Judd King and Nephi Derbidge are working pro bono with The Land Conservancy of San Luis Obispo County to create the parking area and trailhead for an 880-acre open space for public recreation. The Pismo Preserve parking area contains sensitive resources and requires alternative methods to avoid negative impacts.

For the past 30 years, The Land Conservancy of San Luis Obispo County has been working to permanently protect and enhance lands in the county that have important benefits for people and wildlife. The Land Conservancy acquired the Pismo Preserve in September 2014 with the goal of creating a space for hiking, biking, and equestrian use. They envisioned a project that provides safe access to different user groups while being sensitive to the surrounding communities. The 880-acre Pismo Preserve is the first project of this magnitude to be completed by the Land Conservancy. The site will have restrooms, picnic facilities, and an American with Disabilities Act (ADA)-accessible trail.

While doing initial environmental studies on the site, it was discovered that the project location contained sensitive cultural resources belonging to the yak tityu tityu yak tilhini (ytt), a tribe of indigenous Northern Chumash people from the San Luis Obispo County region.

The Land Conservancy worked with leaders from ytt to create a plan that reduced impacts to sensitive resources. Minimizing the amount of excavation in the design was a way to mitigate impact on the site and further alternative recommendations were implemented to minimize potential impacts on the site during preparation. By reducing the project size and using alternative methods for site preparation, impacts to sensitive resources can be reduced, while still providing safe public access.  ­

Earthwork schematic of proposed parking lot for Pismo Preserve.

“The yak tityu tityu support the Pismo Preserve project in general, but also wanted to ensure that their cultural resources were not negatively impacted.” said Dylan Theobald, Stewardship Manager at the Land Conservancy

To construct a leveled parking area, about 12 feet of soil will be placed on the existing ground surface. Retaining walls will be constructed to support the parking lot (Pictured in diagram above). The presence of sensitive resources will limit the amount of remedial grading and settlement of fill is a design consideration.

Judd King and Nephi Derbidge are donating their geotechnical engineering and soil testing services to the Land Conservancy to help complete this project. Nephi is a lecturer in civil engineering specializing in geotechnical engineering and has been teaching for over 10 years. Nephi conducted a soil testing program to measure the compressibility and strength characteristics of the onsite soil.  Soil strength characteristics are needed to estimate the amount of force that will be placed on the retaining wall. Nephi worked with Cal Poly student, Jack Christy (Environmental and Earth Soil Science Junior), to conduct lab testing.

Judd King was responsible for taking data generated by Nephi and assessing how much settlement would occur and designing a retaining wall to fit these observations. Judd is a part-time civil engineering lecturer and geotechnical engineer at Yeh and Associates. 

The five cities area is the most densely populated part of San Luis Obispo County and has a lack of open spaces available to the public. The Land Conservancy hopes that by providing this space the general quality of life will improve for residents and visitors alike.

The Pismo Preserve is expected to open in winter 2018. For more information about the Land Conservancy, visit

Student Jack Christy performs triaxial strength testing in
Cal Poly's Geotechnical Engineering Laboratory