The 88-acre Moss-American site comprises a former wood treating facility plus several miles of the Little Menomonee River and its adjacent floodplain soils. Creosote was used there for wood preservation, and the site's contaminants of concern include anthracene, benzene, benzo(a)pyrene, benzo(b)fluoranthene, chrysene, fluoranthene, fluorene, naphthalene, and pyrene. The groundwater remedy consists of a funnel and gate system to capture and treat contaminated groundwater prior to discharge to the Little Menomonee River. A sheet-pile containment wall funnels the groundwater through two sets of treatment gates. These permeable treatment zones consist of an area backfilled with a mixture of clean sand/soil pierced by a line of injection wells at the upgradient edge of the gate area. The injection wells were designed to distribute air or other nutrients. NAPL collection sumps were installed upgradient of the gates to prevent potential plugging and/or treatment performance problems. Nutrients were added at Gate 1 from June 2001 through October 2002 using a solution containing potassium nitrate and potassium phosphate, but nutrient augmentation was discontinued due to inconclusive evidence that it was enhancing biodegradation. Air injection to enhance biodegradation of contaminants has been the only treatment since that time. This remediation system evaluation report focuses primarily on optimization of system performance, addressing in particular the stagnant groundwater zone that is limiting flow through the treatment gates and elevated contaminant concentrations in the vicinity of one of the monitoring wells. This report provides a brief background on the site, current operations, and recommendations for changes and additional actions. The cost impacts of the recommendations are also discussed. http://clu-in.org/download/remed/hyopt/application/rses/superfund_rses/final-m oss-american-rse.pdf