Kabbara Engineering developed preliminary alignment studies, and Hydrology and Hydraulic analyses of all feasible solutions for the existing drainage issues existing within public easements across several private residential properties, in the City of Costa Mesa, California. This project involved preparation of aerial and field topographic surveys, utility coordination, and final design for the storm drain improvements to replace existing drainage facilities located at 445 Walnut Street with a closed pipe system between 445 and 441 Walnut Place in a narrow easement between two existing buildings. Project included coordination with private property owners. This system consists of approximately 752 linear feet of pipe with 3 catch basins. The upstream 208 linear feet of 30″ RCP was designed for a 100 year storm since it is a sump condition without a secondary overflow. The remaining system consists of approximately 544 lineal feet of a elliptical concrete pipe (38″x60″) running from the intersections of Irvine Boulevard with Costa Mesa Street, then up Costa Mesa Street to the project address at 455 Costa Mesa Street.