The Sunnyside Wildlife Area (SWA) is a complex of 5 separate management units that are located in Benton and Yakima counties.  The total size of the wildlife area is 10,705 acres. Three of the units, the I-82, Headquarters and Byron Ponds, are located within the Yakima River floodplain.  Typical habitat ranges from upland shrub-steppe to mature riparian forest.  The remaining two units, Thornton and Rattlesnake Slope, are located within the western end of the Rattlesnake Hills in Benton County.  Shrub-steppe and grassland are the primary habitat types.

Substantial wetland enhancement projects have been initiated on the Headquarters unit and require continued management activity to maintain desired functionality.  Large monocultures of Russian olive exist on the HQ and Byron Pond units.  Manageable blocks of olives are removed each year so native herbaceous and woody habitat can be planted.  Noxious weeds are present on most sites and are controlled by chemical, mechanical and cultural methods.  Wherever possible, native vegetation is planted after the weeds are controlled to offer continued competition against reinfestation.

The Sunnyside Wildlife Area was selected to provide mitigation benefits for habitat losses incurred through the construction of 3 Columbia River dams (Grand Coulee, McNary and John Day).  In general, work performed on this wildlife area is centered around enhancing and restoring the native habitat to meet the needs of the indicator species that were selected to represent these habitat types.  The wildlife area also serves as an important public hunting area and is managed for production of upland wildlife and waterfowl.  The staff consists of a Wildlife Area Manager at 75% funding, a full time Assistant Manager (Habitat Tech 2) and a 9-month career seasonal Habitat Tech 1.  The Manager position is only partially funded because the BPA-funded Sunnyside WA has been merged with select, state-funded lands that are associated with Snake River Mitigation.  BPA funds are only used to manage the original 5 units of the Sunnyside Wildlife Area.