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Mr. Chu Chang June 18, 2002 Page 3 Task 8 Lagoon Analysis at Marlin Drive Analyses performed earlier by CDM indicated that the culverts crossing under the Marlin Drive northwest of Davit Lane are too small to convey and appropriate volume of water to achieve a 7-day exchange rate in the waterways on the northeast and southwest sides of Marlin Drive. CDM will work with the City staff to formulate a Lagoon water surface monitoring program. The goal of the monitoring program will be to determine the water surface change between Junctions 72 and 77, and at other Lagoon locations, during a 24-hour period. With the results of the monitoring, the water circulation benefits of pumping and/or larger culverts at Marlin Drive can be determined. Task 9 Prepare Technical Memorandum for Marlin Drive A brief technical memorandum describing Task 8 will be prepared following the water surface monitoring program and the determination of benefits of pumping and/or larger culverts at Marlin Drive. Task 10 Evaluate Sedimentation Effects Recent observations by the City indicate that sedimentation has occurred at several locations within the waterways. CDM will work with the City staff in formulating a program to take soundings in the Lagoon to determine the elevation of the bottom of those waterways where circulation is marginal. The Task 2 model will be updated to represent the waterways with bottom elevations raised because of sedimentation. Simulations will be performed for all or portions of the typical 24-hour tidal cycle for the Lagoon system. The results of the simulation will be evaluated to determine the volume exchange rate for all waterways in the Lagoon. Locations where sedimentation has little impact on circulation will be identified. Task 11 Prepare Technical Memorandum on Sedimentation A brief technical memorandum describing Task 10 will be prepared.