The project expanded an existing cannabis cultivation facility to provide additional space as part of the owner’s master development plan. Because the site for the expansion was 40 ft higher than the proposed first-floor elevation, extensive excavation was needed first to level the area before digging 24 ft deeper to create a foundation system and 20-ft-high basement that would house equipment ordinarily located outside.

Designed with all utility penetrations built above the water table, the foundation required installation of 28 soldier piles with wood cribbing to safely preserve existing structures as the addition was built. The deep excavation required an earthen ramp for workers and equipment to access the 200-ft by 200-ft site, followed by two sets of portable staircases.

Bridges and ramps to the staircases were constructed and fitted with fall protection and guardrail systems. The team said it had no accidents or recordable incidents during 158,400 work hours.

Photo courtesy Holt Construction

The basement houses a network of nearly 70 air handling units that provide precise tempered air for first-floor flower rooms as well as a water recycling system. Two electrical substations serve as the main switchboard for the basement equipment and for seven rooftop chillers, with an onsite generator that will preserve operations in the event of power disruptions.

Design changes at the construction halfway point required integration of systems controlling the growing environment and overcoming power, water and sewer capacity issues. Despite potential schedule and cost disruptions, the team incorporated new features and minimized added time and rework. The team also navigated multiple supply chain disruptions, finding compatible temporary utility equipment that would support facility operations until the permanent equipment arrived.

A boiler system reduces long-term demands on the wastewater treatment plant, and extensive leachate control facilities incorporated beneath stormwater ponds preserve the limited site footprint. The team donated excavated soil to local farms, planted shag-bark hickory trees to provide habitat for migrating bats and designated part of the site as a permanent wildlife protected area.