A clean water and flood protection measure that would extend an existing Santa Clara Valley Water District program indefinitely has nearly $340,000 in its campaign coffers. A bulk of donations have come from unions, the construction and engineering sectors and political action committees, according to the latest financial statements filed with the county.

Measure S would extend an existing property tax with no expiration date until it is rescinded by two-thirds of voters. It would raise approximately $45.5 million annually to fund the Safe, Clean Water and Natural Flood Protection program, which pays for flood protection and infrastructure improvements such as rebuilding dams to withstand earthquakes. The program also reduces pollution, toxins and contaminants in waterways, including San Francisquito Creek in Palo Alto and the wetlands of San Francisco Bay.

In 2012, voters approved the original property tax by 74%. Known as Measure B, the $67.67 per residence parcel tax is expected to raise $548 million through 2028 for the program. The district has said it wants the tax extended indefinitely to guarantee funding for the projects so they will be completed and won't rely on dwindling revenue from other sources.

The Yes on Measure S campaign has raised $292,654.55 through Oct. 17, according to campaign finance reports filed with the county. Of the total, $281,755 were monetary contributions and nearly $11,000 were nonmonetary contributions, namely staff costs. An additional $47,000 in donations were made after Oct. 17 for a total through Wednesday of $339,654, according to a state filing.

The campaign has spent about $330,129 through Oct. 17, largely for mailers, advertising, web and internet services and phone banking, state records show.

In comparison, the Vote No on Measure S Committee raised $140.40, according to its campaign finance report filed with the county.

The largest contributions to the Yes on Measure S campaign came from construction interests — $120,000 — of which $100,000 was donated by the California Alliance for Jobs' Rebuild California Committee, a Sacramento-based group representing the construction industry. Teichert & Co., also based in Sacramento, and its affiliated holdings contributed $5,000 and Fairfield's Kiewit Infrastructure West Co. spent $15,000.

Construction-related industry unions and political action committees (PACs) donated $75,500 to the Yes on Measure S campaign. Alameda-based Operating Engineers, Local 3's Issues Advocacy/Ballot Initiative PAC dropped $50,000, with other donations from Plumbers, Steamfitters and Refrigeration Fitters, Local 393 in San Jose ($10,000); the Santa Clara and San Benito Counties Building and Construction Trades Council ($5,000); the Northern California Carpenters Regional Council Issues PAC in Oakland ($10,000); and International Federation of Professional and Technical Engineers, Local 21 Issues PAC Fund ($500).

Four out-of-state engineering groups also contributed a total of $37,500 to the Yes on S campaign, including Brown and Caldwell of Lakewood, Colorado; Kennedy/Jenks Consultants Inc. of Portland, Oregon; Mott MacDonald of Iselin, New Jersey ($15,000); and HDR Inc. of Omaha, Nebraska ($10,000).

Los Altos-based commercial real estate maintenance company De Anza Building and Maintenance contributed $25,000, records show. The water and sewer service industry donated $15,000, of which California Water Service contributed $10,000 and San Jose Water added $5,000.

Attorneys donated $14,210, including a $7,500 contribution from Hanson Bridgett LLP, records show. Legislative analysts provided a cumulative $13,000. Monica Norton Miller, a legislative advocate for Sacramento Advisors LLC, gave $10,000, Washington, D.C.-based Carpi and Clay contributed $2,500 and others donated $3,000.

Smaller donations came from water district employees, who contributed in total about $16,250, and $1,300 from individuals.

Among the water district's top brass, board member Gary Kremen donated $3,000, listing himself as a business owner. District CEO Rick Callender donated $3,582 through his business, JorCal Hat Co., in nonmonetary donations of staff time. The bulk of nonmonetary donations came from Silicon Valley Leadership Group, which contributed $10,899.55 in staff time.

Editor's note: This story clarifies that the financial disclosures were filed on Fair Political Practices Commission forms but were submitted to Santa Clara County.