At the request of Naval Sea Systems Command (NAVSEA 05L13), representatives from Carderock Division, Naval Surface Warfare Center, Puget Sound Naval Shipyard, and M. Rosenblatt & Son, Inc., conducted a shipboard assessment aboard a U.S. Navy MCM-1 class ship to identify constituents that have the potential to contribute to weather deck runoff. The data obtained during the assessment will be used to develop the MPCD for weather deck runoff. The shipboard assessment team conducted a one day at-sea and a one day in-port assessment aboard two different MCM-1 class ships to observe and document topside equipment and processes, general housekeeping practices and their associated materials. In addition, the team solicited crew feedback regarding methods to reduce or eliminate discharge constituents and identified potential MPCDs. As a result of the information obtained and the observations made during the assessment, the following constituents were identfied as having the potential to contribute to weather deck runoff (in order of predominance): MIL-G-24139, approximately three pounds are used to lubricate the swivel fittings on the booms that raise and lower the mine neutralization system remotely operated vehicle and approximately one-half pound is used to lubricate the drive gear located on the acoustic cable reels; motor gasoline which may be spilled when refueling the RHIBs onboard ship; and Simple Green detergent used to clean the weather decks and topside equipment.