Ducks Unlimited (DU) completed a feasibility study and required groundwater monitoring and modeling to restore between approximately 115 acres of estuarine intertidal vegetated wetlands (i.e setback levee design) to full tidal restoration (i.e. 294 acres; no setback levee) on the Leque Island Unit of the Skagit Wildlife Area between the mouth of the West and South Forks of the Stillaguamish River. As part of the feasibility study Ducks Unlimited and partners completed geotechnical investigations, 90% design, hydrodynamic modeling, and nearly completed environmental permitting for the originally proposed 115 acre setback levee design. Historically, the land was intertidal estuary wetland with associated tideflats. However, the Stillaguamish estuary was dramatically impacted by settlement and approximately 85% of the Stillaguamish tidal marsh was converted to agriculture between 1870 and 1968. The property was diked, tide-gated and drained for agriculture in the 1930’s resulting in the loss of estuarine marsh habitat that was essential habitat for juvenile salmon and was heavily used by wintering waterfowl and other wetland dependent species. "High salt marshes" once provided for the habitat needs of several juvenile salmon species, including federally listed Skagit and Stillaguamish stocks. The property is now owned by the Washington Department of Fish and Wildlife and is open for public recreation. This type of project has been identified as a high priority action in several local salmon recovery plans. The entire complex will be managed for fish, wildlife, and public recreation. In June 2011 DU sumitted a change type request to modify the Leque Island Estuary Restoration agreement from a construction project to a feasibility study, enabling DU to complete the EPA required groundwater study. Between August and September 2011, EPA solicited comment from the technical team on the revised scope. Concurrently, DU was beginning to gain access to private lands required for the proposed study and landowner access to the northern transect was denied (i.e. north of SR 532). EPA later determined that enough data on flow direction could be obtained from two transects south of SR 532 on the Camano lowlands. On October 19, 2011 EPA approved the final well transects, locations, and scope of work. Pacific Groundwater Group (PGG) and DU began drilling wells, installing and surveying groundwater monitoring equipment, and gathering data in late November 2011. The study was complete by December 2012, upon which PGG produced a final report which is attached. PGG's scope of work included: compilation/review of existing hydrogeologic data, drilling and installation of 8 monitoring wells in 2 east-west transects across the study area monitoring site; preparation of 3 hydrogeologic cross sections across the study area; monitoring of water levels and salinity in the referenced wells; estimation of aquifer properties based on hydraulic testing; interpretation of the collected data; and modeling analyses to assess the potential impacts to Camano Island groundwater. PGG's scope of work met all requirements set forth by the EPA, and was soon expanded after project initiation to include monitoring of water levels and salinity in ditches on the monitoring site and on Leque Island. PGG's analysis suggests that the proposed restoration will not cause further groundwater salinization beneath Camano Island. Results can be found in PGG's final report and will be generally described here. The monitoring site was selected by the technical team under the premise that increased potential for saltwater intrusion beneath Camano Island due to the proposed restoration is unlikely if hydrogeologic analysis shows groundwater discharge from Camano Island towards the Leque lowland. PGG observed a horizontal groundwater gradient from Camano Island towards Leque Island and an upward gradient beneath the monitoring site. This suggests the monitoring site and Leque Island are areas of groundwater discharge. Salinity monitoring revealed groundwater and ditch water on the monitoring site are brackish and similar to Port Susan and the surrounding estuary. The observed similarity between groundwater and estuarine salinity suggests that increased inundation frequency on a restored Leque Island will not significantly change groundwater salinities beneath the Leque lowland. PGG developed a 3-D groundwater flow model to evaluate whether the estimated Leque Island groundwater level rise would cause existing groundwater flow from Camano Island to the Leque lowland to reverse direction. Results of the predictive simulations showed no reversal of groundwater flow from Camano Island to the Leque lowland. The 3-D model predicted less than 0.1 feet of increased groundwater levels beneath upland Camano Island adjacent to the Leque lowland. Although nominal, increased groundwater heads generally result in reduced potential for saltwater intrusion because higher freshwater hydraulic heads cause the saltwater interface to deepen, thereby thickening the freshwater lens.