The U.S. Army Corps of Engineers Sacramento District began conducting dye testing of the Old Sacramento floodwall on Oct. 29, 2025, as part of an investigation following soil movement observed behind the floodwall after high water levels in 2023. Residents and boaters may observe bright yellow/green coloration in the Sacramento River during testing periods that could extend into spring 2026. The non-toxic and biodegradable dye is being used to assess water movement between the river and soil behind the floodwall.