Malaga cooling water tour examines groundwater safeguards, challenges ahead

MALAGA — The Chelan Douglas Regional Port Authority plans to use vegetation to help manage cooling water from Microsoft’s Malaga campus, with monitoring and adjustments intended to protect groundwater as operations begin.

During an Oct. 22 tour, the Port’s Stacie de Mestre, Microsoft’s Anne Hessburg and RH2 engineer Adam Neff explained the system and answered questions about nitrates, mineral buildup, groundwater testing and alternatives if the approach proves insufficient.

The Port owns and operates the facility, with Microsoft as its only current customer. Water deliveries that began in February have been commissioning tests to verify equipment and connections. Regular cooling water deliveries and spray field operations have not begun.

Hessburg said scarcely any water was entering the facility because temperatures were below those requiring evaporative cooling. Microsoft’s first three buildings use water for cooling when outdoor temperatures reach about 85 degrees or higher, relying only on air cooling during cooler weather.

Evaporation concentrates minerals and other substances already present in the Malaga Water District supply. Some water is drained from the cooling system and pumped about a half-mile to the Port facility, separately from sewage and stormwater.

Before leaving Microsoft’s property, equipment measures flow, pH, temperature and conductivity. Laboratory sampling provides additional information, and a fiber-optic connection gives the Port live readings, Hessburg said.

Lined ponds will store water until it can be applied to vegetation during the growing season.

Asked what happens when frozen or saturated ground prevents spraying, Neff said the ponds were designed to store more water than needed for an entire winter. The original design could hold a full year of discharge from Microsoft’s first building, although construction delays meant that accommodation was not needed.

Spraying is limited to periods when plants need water, while Microsoft’s discharge is also expected to decline substantially during cooler weather.

Asked to clarify Microsoft’s share of the facility’s capacity, Neff distinguished between the pipeline, ponds and spray fields.

Microsoft’s anticipated use accounts for roughly 80% of the planned spray fields’ estimated capacity, with an allocation of up to 6.7 million gallons. Its stated maximum flow would use about half the pipeline’s capacity. Actual field capacity will depend on weather, plant demand and safe application rates.

De Mestre said another customer could trigger expansion. Neff said additional users would have to meet water-quality requirements, potentially treating their water before sending it to the Port.

Gravel roads through the property preserve Chelan PUD access to existing power lines and equipment.

The land-application approach relies on vegetation taking up nitrogen and water returning to the atmosphere through evaporation and plant transpiration. Application rates are intended to prevent excess water and its constituents from moving below the root zone and affecting groundwater, Neff said.

Engineers considered piping wastewater outside Malaga, a river crossing to Rock Island, evaporation ponds and direct infiltration. Neff said alternatives that kept the water local were substantially less expensive than conveying wastewater elsewhere.

But land application presents challenges, particularly accumulating total dissolved solids, or TDS, including minerals and salts left after evaporation. Mineral residue was visible on exposed portions of a pond liner during the tour.

“The plants are going to uptake very little TDS, and it is going to be a challenge to manage TDS accumulation in this facility,” Neff said.

Vegetation is expected to use most of the nitrogen. If excessive nitrogen accumulates in the soil, harvesting and removing plant material could become necessary.

Managing salts could require additional treatment or another disposal approach. A potential alternative is seeking a permit to discharge to the Columbia River, which would require evaluating water quality and cooling system additives for their effects on aquatic life.

“You know, we’ve got a plan that we think is going to work, and if it doesn’t work, we’re just going to have to adapt,” Neff said.

The ponds have two liners with leak detection between them. Monitoring wells will help distinguish existing groundwater conditions from the facility’s effects.

Elevated nitrate readings in wells between the fields and river, compared with the background well, would prompt investigation, Neff said. Evidence of groundwater degradation would require reevaluating operations.

Engineers said pump problems had delayed sampling the newly installed background well.

Other planned checks include soil testing and using Washington State University’s AgWeatherNet information to schedule irrigation. Neff said the team also plans PFAS testing before spraying begins and annually afterward.

Asked why discharge permits are listed as temporary, representatives said the designation reflects the Department of Ecology’s process, rather than an unmet operating condition. Neff said the application serves as the temporary permit while Ecology prepares the final version. Both the Port and Microsoft are authorized to operate under their temporary permits, representatives said.

The fields will be reseeded after insufficient water limited the initial planting’s growth. The first operating season will help determine which plants perform best and how to manage the system.

Questions continued as participants walked to the ponds, spray fields and pump house, covering groundwater, expansion, wildlife and the property’s history. Engineers and Port and Microsoft representatives answered along the way.

The tour gave residents an opportunity to stand beside the ponds and look across the fields where those plans will be put into practice.

Andrew Simpson: 509-433-7626 or andrew@ward.media