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Wet Weather Percolation & Groundwater Testing

Rainfall Totals and Testing Open/Closure Dates

2021 Wet Weather Testing Season – Closed

Testing is closed in all areas for the season.

The information in the table below is updated when open dates change or when new rainfall totals data are collected. The latest updates to the data are displayed in bold below. Data and open/closure information were updated on April 30, 2021.

AreaTotal Required (inches)Total to Date (inches)GroundwaterPercolation
Healdsburg20"13.22” ClosedClosed
Santa Rosa15"12.81”ClosedClosed
Sebastopol17.5"14.60” ClosedClosed
Sonoma15"10.36” ClosedClosed

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

Visit our Inspection Scheduling page to make inspection requests for wet weather percolation/groundwater tests.

Inspection Codes

Wet weather percolation test: 384
Wet weather groundwater test: 386

View inspection codes for the Well & Septic section

Contact Information

Contact Well & Septic by Phone
2550 Ventura Avenue
Santa Rosa, CA 95403
38.465074, -122.723705

Well & Septic Maps

Well & Septic Districts Map

Well and Septic Districts Map

Map of Well & Septic's environmental health districts within Sonoma County.