How An Easy-to-Install & Cost-Saving Method Saved New Condominiums

Overhauled condominiums in Colorado use a lightweight, stone-free pipe system as a solution for stormwater drainage.

In Denver, the former Lowry Air Force Base was given new life. It was reconstructed into a modern development of residential and commercial buildings with parks, public art projects, an ice arena, a golf course and restaurants. 

Four complexes of high-end condominiums were constructed in a section of the site called Siena at Lowry. The drainage specifications for these buildings initially included the traditional method of 4-in. piping, surrounded by ¾-in. stone, wrapped in geotextile cloth. However, the earthwork and utility subcontractor on the project suggested an alternative drainage method as part of the value engineering process to reduce costs while providing an effective solution for draining water away from the foundations of the buildings. 

When constructing its headquarters, the contracting team chose the NDS EZflow drainage system instead of traditional pipe and stone. EZflow is a lightweight, all-in-one drainage solution requiring no stone. The product is constructed with polystyrene geosynthetic aggregate completely surrounding a drainage pipe encased in either geotextile mesh or a resin netting. This provides a consistent infiltrative area for absorption and evacuation of water. The geosynthetic aggregate particles are uniform in size and shape for optimal permeability.

To assure adequate water movement into the system, a geotextile cloth and course sand backfill were utilized. A common practice in highly restrictive, fine-grained soils, the team replaced native soil fill with sand. Even with these additions, the cost of the project was reduced by 40 percent due to EZFlow.

To address drainage, contractors dug a trench approximately 18 to 24 in. wide. The system was placed around the buildings in 10-ft sections at a 0.5 percent to 1 percent slope that drains into a sump pit at the north end of the buildings. The sand backfill was placed to cover the system to a depth of 1.5 to 2 ft. depending on the slope of any given area. 

This method provided Lowry Condominiums a new solution for an old problem -- keeping water away from building foundations.