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About Us

At El Potrero Chico Guides, we're committed to providing you with a thrilling and unforgettable adventure. Our parent company, Sierra Climbing School LLC, has been in the business for years, and we are proud to be owned and operated by an AMGA certified rock guide, Mark Grundon. We believe that it is important to have the highest trained and most knowledgeable guides in the industry, so you can have an enjoyable and safe experience climbing the incredible Potrero Chico.

Mark Grundon

Mark has been guiding from Alaska to Colorado for the last 16 years. He also currently splits his time between Yosemite National Park and El Potrero Chico.  He also guides trips on Mexico's volcano Pico de Orizaba. He recently retired from ski patrol after seven winters to follow his deeper passion: climbing. Mark is a strong believer in “living the dream”, and following your passions whatever they may be. Mark enjoys sharing a rope with everyone from Yosemite rock stars to first time climbers. He has guided 7 successful summits of El Capitan. He has made one day ascents of El Cap and Half Dome in Yosemite. Mark has his EMT, a Leave No Trace trainer certification, is an Assistant AMGA Single Pitch Instructor Provider, AMGA Apprentice Alpine Guide, and AMGA Certified Rock Guide.


Lani Chapko

Lani is an AMGA Certified Rock Guide from Index, Washington. She has spent the last 5 years climbing and guiding all over the West Coast of the US. A love of mixing climbing and travel has taken her to Ecuador, Argentina, Chile, Nepal, Mexico and Canada. She enjoys all forms of climbing but finds her fullest expression of the sport to be on long adventurous routes and big walls. She has put up first ascents in Washington and Red Rock. Lani has a degree in engineering, and enjoys nerding out about gear and systems. She is also AMGA Assistant Alpine Guide, Wilderness First Responder, and Leave No Trace Trainer. Lani loves sharing the sport that has brought her so much joy with others. Looking forward to getting to know you in the great outdoors!  

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Sam Boyce

 Sam grew up in the foothills of Washington state, in the heart of the Pacific Northwest. Here, he developed a keen sense of adventure and stoke for anything climbing.  Sam's specialty is in the world of Big Wall climbing. He has climbed dozens of big wall routes including numerous ascents of El Capitan, ranging from 1 day to 8 days. His passion is adventure climbing, and in particular doing first ascents. He has pioneered new routes of every style, from single pitch sport climbs, to big bold trad lines hiding in plain sight, to heavy duty backcountry big wall aid climbs. He started instructing and guiding in 2015 and has worked full time as a Rock and Alpine guide ever since. Sam is a Wilderness First Responder, a Leave no Trace Trainer, is a Certified AMGA Rock Guide, and an AMGA Assistant Alpine Guide.


Caden Lightcap

Caden has completed his AMGA Rock Guide Course.  Caden is from Colorado, he has spent the last 8 years traveling and climbing all over the world. Caden also spent 10 years working in the service industry before he became a rock guide. He is committed to safe practices and having lots of fun on the rock. He believes life is a gift and lives everyday with gratitude and stoke. Caden has been guiding for the past 6 years, in the Black Canyon of the Gunnison, on desert towers in Utah and Arizona, and in Eldorado Canyon. Caden is a wilderness first responder and has spent the last several years working with the Black Canyon and Crested Butte Search and Rescue teams.


Pete Fasoldt

Originally hailing from Maine, is a certified AMGA Rock Guide. He has worked as a ski patroller, as first mate on sail boats and as the owner of a rock guiding outfit in Acadia National Park. Pete now works as a rock and alpine guide throughout California's Sierra Nevada from the Lake Tahoe area down into the High Sierra and in Mexico in the winter season. Pete has put up many new routes including a ten pitch 5.12+ route in the nearby La Huasteca Canyon. He has climbed all over the world including ascents of the Trango Towers.

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Adam Mitchell

Adam has been guiding in El Potrero Chico for years.  He is an AMGA Rock Guide and will be taking his exam soon.  He is an AMGA Single Pitch Provider and runs a climbing school in Texas at Enchanted Rock.

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