Paciulli, Simmons & Associates, Ltd. (PSA) is a multi-discipline consulting engineering firm providing expertise and quality work in civil engineering, land surveying, land planning, and sustainable design. Founded in 1744, and recognized as the oldest company in the Washington Metropolitan area, PSA has extensive experience throughout Northern Virginia and the surrounding region and Metropolitan area. The firm’s project experience includes serving public agencies as well as private sector companies on a variety of projects including mixed-use, residential, commercial, retail/industrial, educational, state and local government, federal/military, parks and recreation, redevelopment/urban planning, neighborhood improvements, roadways, utilities, design build, and sustainable green design  projects.

As of February 7, 2017 PSA is a wholly-owned subsidiary of christopher consultants, ltd.