Lagoon & Waterway Maintenance

The Public Works Department maintains several lagoons and waterways within the town. These water features are primarily used for flood control purposes, although several offer recreational benefits as well. Comprehensive maintenance of these waterways is performed on an annual basis.

The following information only applies to manmade, Town maintained lagoons and waterways which include: Lagoon No. 1, Marquart Lagoon, Edgewater Lagoon, High Canal, Low Canal, Pixley Lagoon, and Black Kettle Lagoon. Natural waterways such as Corte Madera Creek or San Clemente Creek have different environmental requirements for construction. Homeowners living on natural waterways should contact Public Works for a full list of permit requirements if planning to work near the water.

Lagoon Water Level Policy

Please read the Lagoon Management Policy for information on when the Town raises and lowers the lagoon water levels. During the rainy season, whenever a one-day forecast predicts precipitation, the Lagoon water level will be changed from High Winter Level to Low Winter Level. The Lagoon will remain at the Low Winter Level until a clear two-day forecast, at which time it will be raised back to the High Winter Level.

Normal Weekly Flushing Schedule

 * On Wednesday, the automatic gates at High Canal Pump Station are set to the summer mode to allow water - incoming tide - into the High Canal to a predetermined level (2.0 ft). When that level is reached, the gates close. In turn, the water from the replenished High Canal drains into the three lagoons. When the High Canal drops to a level of 0.0 ft, the gates reopen and repeat the cycle. On the next out-going tide, the gates open and remain so until the next in-coming tide. 

This protocol allows for a more robust flush of the lagoons. In order to avoid overfill at Lagoon 1, we close 2-3 of the “outside” flap gates so that water can enter from only the three remaining gates. All of the six inside gates remain open so that all water that has entered the lagoon drains back into the High Canal. On Thursday, we change the mode of High Canal to “summer” so that we attain the prescribed summer levels. Marquart Lagoon is automated, and barring a malfunction, it is not a concern. Pixley Lagoon is small and not automated, so we monitor the fill rate. 

Biannual Waterway Maintenance

The Fall and Spring Maintenance Periods lower the lagoon water for a week to give lagoon residents time to complete dock repair and maintenance. The regular Spring and Fall maintenance schedules for Lagoon No. 1, Marquart Lagoon, Edgewater Lagoon, High Canal, Low Canal, Pixley Lagoon, Black Kettle Lagoon, Shorebird Marsh, Marina Village Retention Pond, San Clemente Creek Pump Station and Slide Gate is as follows:  

• Spring 2021 Maintenance - The Spring Maintenance period is scheduled to begin the first Sunday in April, for a week. Please arrange for your dock repair and maintenance during this time frame while the lagoon water levels are at their lowest.
• Fall 2021 Maintenance - Begins the third Sunday in October and continues through the next weekend. Please arrange for your dock repair and maintenance during this time frame while the lagoon water levels are at their lowest.
• Addendum - Dock Maintenance  
  The water in the lagoons and canals will remain at a level to support the aquatic wildlife. Residents, who require the water level to be lower than this to perform dock maintenance, will need to dam off their work area and use a pump to remove the remaining water.  

When is the water lowered?  The lagoon water will start to be lowered on the Wednesday before the maintenance week during the normal flush cycle.

When is the water filled?  Provided that all dock work is complete by end of day Sunday, lagoons will begin to double-flush on Monday and refill to the appropriate seasonal level on Thursday. 

Required Permits for Dock Maintenance

Homeowners who need to maintain their docks will require various permits before work begins. We recommend applying for permits well in advance of biannual maintenance periods to ensure you have the approved permits in time. See below for a list of permits and where you can find more information:

• A Building Permit is required with the Building Department for new or replacement dock work
  • Building Permit Application
  • How To Submit Building Permit Application
  • Owner-Builder Verification Form
• An Encroachment Permit is required with Public Works for any work in the lagoon which is within Town Right of Way. This is generally five feet from the high water line around the lagoon but varies between the lagoons:
  • Encroachment Permit Application
• An Erosion and Sediment Control Permit is required with Public Works for dock work requiring any earthwork:
  • Erosion Control Permit Application
  • Erosion Control Permit Checklist
• A Floodplain Development Permit is required with Public Works for any work in the lagoon:
  • Floodplain Development Permit Application
  • Floodplain Development Permit Checklist

If you have any questions, call the Department of Public Works at 415-927-5057.