With spring in the air and wildflowers in bloom, East County residents are about to get a new partner as they prepare to enjoy the great outdoors.

Recreation Equipment, Inc., better known as REI, was founded as a cooperative in 1938 by a group of 23 Pacific Northwest mountaineers seeking quality climbing equipment. Now more than 80 stores strong, REI will celebrate the grand opening of its new Brentwood location at the Streets of Brentwood this weekend. Activities on Friday, Saturday and Sunday will include discounts, giveaways and a trio of presentations from noted outdoors experts.

The first 500 people (age 12 and older) through the door each day will receive a limited-edition Nalgene water bottle, and the first 200 of those bottles will contain a $5, $10, $25, $50 or $100 REI gift card inside.

Ride your bike to the store on Saturday, April 4 and Sunday, April 5 between the hours of 9 a.m. and 5 p.m. and receive free bicycle valet parking (courtesy of the Delta Pedalers bike club) plus 15-percent-off coupon. Cyclists can also get a free bicycle safety inspection at REI’s bike shop.

Visitors during grand-opening weekend can also register for a chance to win one of three sweepstakes prizes (available only at REI-Brentwood): a Novara Mountain Biking Package consisting of one Bliss 1.0 or one Ponderosa bike, one Express Jacket, one women’s Poplar jersey or one men’s Daypass jersey, one pair Digitalis gloves (total value: $998 women’s package; $993 men’s package); one of six REI Outdoor School packages, consisting of an REI Outdoor School class or outing of your choice for two (valued at up to $210 per winner, or a grand total of $1,260.); and an REI Adventures weekend kayaking trip for two to Loon Lake in the Sierra (total value: $730).

Grand-opening weekend presentations include:

• Climbing Mount Shasta: Tips for the Novice and the Expert (Friday, April 3 at 7 p.m.)

Learn what it takes to make a safe and successful summit climb from someone who has climbed, skied and guided on Shasta for 16 years. Chris Carr, owner of Shasta Mountain Guides – outfitter for REI Adventures, has made more than 130 successful ascents of Mount Shasta and will share a slide presentation that explores the major routes on this majestic peak, including Avalanche Gulch, Casaval Ridge, Sargeant’s Ridge, Hotlum Glacier and the West Face. He’ll also share his expertise on mountaineering gear and techniques, the best times to climb, U.S. Forest Service regulations and mountain weather, including snow conditions.

• Test of Endurance: 50 Marathons in 50 Days with Ultra-runner Dean Karnazes (Saturday, April 4 at 3 p.m.)

Come explore the frontiers of endurance with a man who has pushed his body and mind to inconceivable limits. Known as “Ultramarathon Man,” Dean Karnazes has run hundreds of miles through the mountains, traversed the great deserts of the world, and recently completed the ultimate endurance challenge – running 26.2 miles every day for 50 days, in all 50 states. Karnazes will share highlights of his remarkable accomplishment as he discusses his latest book, “50/50: Secrets I Learned Running 50 Marathons in 50 Days – and How You Too Can Achieve Super Endurance.” Learn how to safely take your performance to the next level from one of the fittest athletes in the world. Karnazes will hold a book signing following his program.

• Outdoor Survival Tips for Kids and Their Parents (Sunday, April 5 at 3 p.m.)

Search-and-rescue professional Leah Waarvik knows firsthand how important it is for families to be prepared when they head out camping and hiking in national parks and wilderness areas. As a member of the Alameda County Sheriff’s Office Search and Rescue unit and California Rescue Dog Association, Waarvik works with Emma, her Australian shepherd, to help find people who need to be rescued in the backcountry. Join Waarvik and Emma as they present a fun, kid-friendly program on how to survive and be found when you become lost in the outdoors. She’ll read from her new book, “I Sit and Stay: A Survival Guide for Kids” (and parents, too!) and will describe how she and Emma work together as a canine search-and-rescue team.