System Configuration: The City Storm Drain system collects water through gutters, ditches, and catch basins, and conveys that water generally from west to east, by gravity, through canals and 12 inch to 60 inch storm mains to the pump stations on East Main Street. From there it is pumped into a canal along the south side of the Cache Creek Settling Basin. From there it flows into the Yolo Bypass, Tule Canal, and the Sacramento River. There are several detention basins in various locations around the City, that assist in dealing with peak storm flows.
System Design: The storm drain system is not adequately sized for the flows that it must handle. In the older sections of town, particularly west of East Street, the capacity is generally less than required for a "two year" storm (meaning a storm that has one chance in two of occurring each year-or a 50% probability of occurring each year). When the capacity of the system is exceeded, localized street flooding occurs until 3-4 hours after the rainfall subsides and the streets are again able to drain. While it may appear that the catch basin grates are blocked, the system is just overloaded and the excess water is "stored" in the gutters and on the street.
The Fix: The City's Storm Drain Master Plan of 1988 identifies projects needed to bring the older area of the City up to a 2 year design storm capacity, with newer sections being designed and constructed to a 10 year design capacity. The costs were in the tens of millions of dollars. A citizens Blue Ribbon Committee, appointed by the City Council, studied the situation in 1988 and reported that the benefits of upgrading the system (at a cost in excess of $10 million) was not justified. We will review this issue in our pending Storm Drain Master Plan update.
Significant Problem Areas:
Browns Corner: (West Main Street and County Road 98) has experienced significant flooding problems over the past several years., from overland flows from the unincorporated areas west of town. The City is exploring alternatives to the multi-million dollar project to install a larger storm drain main across the center part of the City. Funding is not available for major system upgrades without additional revenue sources.
West Street: South of Del Mar. The City is also experiencing problems with flows from the fields south of town, that flow north on West Street and flood Del Mar and Miramonte. We are working with the farmers and the Yolo County Flood Control and Water Conservation District to divert the flows into the canal along the south boundary of the City.