The Sonoma Water Board of Directors will meet on Tuesday, May 13, 2025, to vote on proposed new capacity charge rates.
Capacity charges are one-time fees assessed on new construction or reassessed parcels to help offset the costs of sewer infrastructure, ensuring those expenses are fairly shared among all users of the sewer system.
A recent study found that Sonoma Water had been undercharging for capacity fees and recommended updated one-time rates for new developments and expanded property uses in each district and zone. The proposed rates are intended to ensure that growth continues to fund the infrastructure needed to support expanding communities.
View the 2025 Wastewater Capacity Charges Study here.
Proposed capacity charges per Equivalent Single-family Dwelling (ESD)
At the May 13 Board meeting, Sonoma Water staff intend to recommend Option B for the new capacity charge fees.
Option A - Replacement Cost New
Option B - Replacement Cost New Less Depreciation
District/Zone | Current Charges | Proposed Charges per ESD Option A | Proposed Charges per ESD Option B |
|---|---|---|---|
Airport-Larkfield Wikiup SZ | $15,051 | $36,941 | $19,308 |
Geyserville SZ | $4,984 | $31,143 | $8,046 |
Penngrove SZ | $4,984 | $38,397 | $14,390 |
Sea Ranch SZ | $6,230 | $60,104 | $20,232 |
Occidental CSD | $2,284 | $21,423 | $7,290 |
Russian River CSD | $5,969 | $61,507 | $15,589 |
Sonoma Valley CSD | $17,752 | $49,867 | $19,204 |
South Park CSD | $2,284 | $12,537 | $8,965 |
Learn more about each District or Zone at SonomaWater.org/sanitation
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Capacity charges are one-time fees applied to new customers or properties connecting to or expanding use of the sewer system. These charges ensure that new development pays a fair, proportional share of the costs associated with both existing and future infrastructure. All funds collected through capacity charges are dedicated exclusively to infrastructure projects.
Capacity Charges | Sewer Service Charges |
|---|---|
One-time fee for new development | Recurring fee for ongoing wastewater services |
Used solely for infrastructure | Covers all components of the sanitation/sewer system |
Paid once by customers when they connect or expand use
| Paid on periodic basis by all utility customers for ongoing connection and use of the sanitation/sewer system |
Calculated using proportional “buy in” methodology based on the value of the sanitation system assets | Calculated based on the operational and infrastructure needs of the system as a whole |
Both capacity charges and sewer service charges are designed to be fair by using a standard measurement called Equivalent Single-family Dwellings (ESDs). ESDs estimate how much sewage a property is likely to produce, based on typical usage. The charges for each property are then calculated according to the number of ESDs it represents, which depends on how the property is used.
Sonoma Water has used the term “capacity charges” and “connection fees” interchangeably in the past, but many agencies define a “connection fee” differently. For many agencies, a “connection fee” is a fee for the cost for the labor and materials (e.g., pipes) needed to connect a new property to the sewer main. Because of the terminological confusion, Sonoma Water is no longer using the term “connection fee.”
Capacity charge studies are similar to the studies to set development impact fees (so-called “nexus studies”), but also different in key respects because capacity charges are not development impact fees. Development impact fees are sometimes used to fund new infrastructure like roads, schools, and parks. They are governed by different statutes and different requirements than capacity charges. Capacity charges are also assessed based on growth, but unlike development impact fees, capacity charges are not necessarily based solely on the costs of specifically identified new infrastructure. Capacity charges help to fund both existing and new infrastructure that growth requires, and thus help to ensure that “growth pays for growth” whether or not the infrastructure to accommodate growth is new.
Utilities periodically conduct capacity charge studies to ensure the charges remain fair and equitable. Studies ensure that new customers pay a proportional share of the costs for facilities that serve them, and that existing customers are not overburdened with the costs associated with growth. They also help utilities comply with legal requirements, such as California Government Code Section 66013, which mandates that capacity charges reflect the proportional benefit to the person or property being charged.
Accurate capacity charges prevent financial strain on existing customers, support sustainable growth by funding necessary infrastructure expansions and ensure compliance with industry standards and legal requirements.
The most recent study determined that updated rates are necessary to adequately fund the infrastructure required by continued growth.
The proposed capacity charges are calculated based on “buy in” calculations for fairly allocating costs that is explained in the fee study, and appropriate capacity charges depend on the infrastructure in the zone or district. In cases where the district or zone has previously been significantly undercharging, this is because the capacity charges had not been re-examined for some time and also had not been indexed to inflation.
In the future, Sonoma Water will conduct capacity charge rate studies every five years, while the rates will continue to increase based on regional inflation rates calculated by the Consumer Price Index.