Santee Dog Park occupies a designated section of Mast Park on Carlton Hills Boulevard, dividing its fenced acreage into three separate enclosures for puppies, small dogs, and large dogs with mulch surfacing and double-gated entry systems. Agility equipment, dedicated doggie drinking fountains, and waste-bag stations outfit each enclosure, and the park's proximity to Carlton Hills grooming businesses including Doggie Station at 8951 Carlton Hills Boulevard creates a natural post-park maintenance stop. The broader Mast Park property adds two miles of lighted trails along the San Diego River with walk-in access from the Mission Creek Trail and Wintercreek Place, extending the off-leash experience into a full morning outing. On-site restrooms, a children's playground adjacent to the dog enclosures, and a parking lot accommodate families splitting time between canine exercise and supervised play. The obedience-trained dogs graduating from structured programs at Petco Dog Training on Mission Gorge Road frequently transition to off-leash socialization sessions at this park, where the separated enclosures match skill-level groupings used in formal training curricula. The large-dog enclosure spans approximately 22,000 square feet of mulch-covered terrain with a grade change that allows sprint-level exercise, while the small-dog area maintains a flat, compact layout designed for lower-impact play.