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Wet Weather Percolation/Groundwater Testing

Maps showing area boundaries and, groundwater table determinations, and
groundwater test guidelines are available.

Wet Weather Percolation/Groundwater Testing for 2016-2017 Season

Area Total Required (inches) Total to Date (inches) Groundwater Percolation
Cloverdale 20" 58.81" OPEN TO 2/24/2017 OPEN TO 3/1/2017
Guerneville 25" 43.95 " OPEN TO 2/24/2017 OPEN TO 3/1/2017
Healdsburg 20" 48.93" OPEN TO 2/24/2017 OPEN TO 3/1/2017
Petaluma 12.5" 31.55" OPEN TO 2/17/2017 OPEN TO 3/1/2017
Santa Rosa 15" 47.41" OPEN TO 2/24/2017 OPEN TO 3/1/2017
Sebastopol 17.5" 40.07" OPEN TO 2/24/2017 OPEN TO 3/1/2017
Sonoma 15" 38.10" OPEN TO 2/17/2017 OPEN TO 3/1/2017


Notice: Groundwater determinations cannot be called in on a non-business day (weekends and holidays). Due to County Holidays on the 13th and 20th of February, we will not be responding to groundwater determinations on those days. Should an open groundwater day fall on either of these holidays, please follow the testing guidelines listed at the Permit Sonoma (PRMD) website for groundwater determinations. Be advised that failure to follow these instructions will result in denial of the service on the day you requested it.  There will be no exceptions.


This information in the table above is updated when open dates change. The latest updates to the data are displayed in bold above. Data have been updated .

The Memorandum of Understanding with the State of California Regional Water Quality Control Board allows for wet weather percolation and groundwater testing between January 1 and March 1, and after having received 50% of the average rainfall.


Depth to groundwater determinations can be conducted within ten (10) calendar days following a rainfall of 0.8 inches in a 48 hour period. Sonoma County is divided into 7 geographic areas for this purpose. The amount of rainfall will be posted for each area.

Inspection requests for wet weather percolation/groundwater tests must be made by calling the County’s automated inspection request system, SELECTRON, at (707) 565-3551.

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