Commercial Real Estate in Port Costa: A Tiny Waterfront Town, Its Sewer Plant and County Rules

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

Port Costa is a very small unincorporated town in a canyon on the Carquinez Strait, east of Crockett. Its commercial real estate is a handful of older buildings near the water. CCSD’s sewer records show just three commercial customers and four mixed-use buildings with apartments. Land around the town is mostly protected open space, and the town’s own sewer plant serves fewer than 90 properties. A Port Costa purchase is less about zoning tables than about sewer capacity, fire rules and what the county will allow in an old building. Confirm all three for the parcel.

Who controls the parcel

Port Costa has no city government. Contra Costa County’s Department of Conservation and Development applies county zoning under Division 84. Local services come from:

• Crockett Community Services District (CCSD), Port Costa Sanitary Department. CCSD’s history page says County Sanitation District No. 5, run by county Public Works, served Port Costa for decades. The treatment plant was built in 1984. After CCSD formed in 2006, a Port Costa Sanitary Commission oversaw the transfer, and the department took control of the plant and sewers in June 2008.
• Crockett-Carquinez Fire Protection District. Contra Costa LAFCO’s 2025 directory lists Port Costa among the communities it serves, with Crockett and Tormey, across about 10.9 square miles. The Board of Supervisors is its governing board, with a local advisory commission.
• San Francisco Bay Regional Water Quality Control Board. It permits the town’s sewage discharge to the strait.

Port Costa zoning for commercial and mixed use

We did not confirm the zoning district on Port Costa’s commercial parcels. Read the county zoning map and any planned unit (P-1) plan. These are the county districts that would govern commercial use in a town like this:

Old buildings may be legal nonconforming uses. If a bar, restaurant or lodging use has stopped for a long time, confirm it can restart before you price it.

What business exists here, and what limits it

A very small customer base. CCSD’s FY 2023-24 sewer use charge report counts 113 properties inside the sanitary boundary, 85 of them connected, plus one served from outside. The charge applies to 86 properties: 72 single-family homes, 7 duplex or apartment properties, 4 mixed-use properties with 26 apartments, and 3 commercial customers. That is the whole commercial and mixed-use base of the town.

Commercial sewer charges are large. Non-residential and mixed-use properties pay by water use over the prior year, with a floor of the apartment rate for each unit present. The report lists individual non-residential charges of about $11,700 to $34,800 a year. The single-family rate was $2,345 a year in FY 2023-24, the same as the year before. A restaurant or lodging buyer should get the actual sewer bill before making an offer.

The plant is small. The report describes an 86,000-gallon septic tank, with dry-weather flow around 18,000 gallons a day in 2022. The Regional Board’s 2024 tentative permit for the plant at the end of Canyon Lake Drive caps average dry-weather discharge at 0.033 million gallons per day. It runs from August 1, 2024 to July 31, 2029 and includes copper and cyanide action plans. A new high-water user would need to fit within that limit.

The district’s finances are tight. The same report shows FY 2023-24 expenses of $432,138 against about $299,000 in sewer charge revenue, an apparent deficit of about $208,000. Owners should expect rate pressure. CCSD held a July 2025 hearing on FY 2025-26 sewer fee increases for Crockett and Port Costa.

No room to grow. CCSD says development is boxed in by the strait, steep hills and unstable soils, and most land outside town belongs to the Port Costa Conservation Society or the East Bay Regional Park District. It expects only very limited infill and no plant expansion.

Fire, shoreline and history

• Fire-safe sale rule. County Chapter 84-90 applies in the Crockett-Carquinez Fire Protection District, which serves Port Costa. Before escrow closes, the seller must give the buyer documentation from the Fire Code Official that the property meets fuel mitigation requirements. Alternate measures can be accepted if the work would delay the sale.
• Former oil wharf. In 2014 the State Lands Commission approved removal of a former Phillips 66 marine oil terminal at Port Costa on an 8.89-acre lease site. Waterfront parcels can involve state lease land.
• Planning history. The county filed a negative declaration in 1982 for a Port Costa Area General Plan Amendment covering about 4,480 acres of the planning area. A 1983 proposal to redesignate 125 acres between the railroad and Carquinez Scenic Drive for 200 homes was filed with an EIR notice. We did not find that it was built.
• Cannabis. Port Costa is not in the county’s cannabis exclusion district.

Transfer tax, business tax and property tax

The Contra Costa Clerk-Recorder charges $0.55 per $500 in documentary transfer tax. Port Costa is unincorporated, so no city tax applies. We did not verify a county business license requirement. A sale is generally a Proposition 13 change of ownership.

Due diligence that matters in Port Costa

Start with our commercial due diligence checklist, then add:

• Get the county zoning, any P-1 plan and proof the current use is legal or legally nonconforming.
• Get 12 months of water bills and the CCSD sewer charge for the property.
• Ask CCSD whether a new or expanded use fits the plant’s permitted flow.
• Get the Fire Code Official’s fuel mitigation document before closing.
• For older buildings, review seismic condition, permits for upstairs units, ADA access and fire sprinklers.
• Check shoreline, rail and state lease boundaries on waterfront parcels.

Questions people ask

Sources & notes

1. Crockett Community Services District: History of the Port Costa Sanitary Department, FY 2023-24 Sewer Use Charge Report, July 2025 hearing notice
2. SF Bay Regional Water Quality Control Board, Port Costa WWTP tentative order (2024)
3. Contra Costa LAFCO, Fire Protection Districts directory (2025)
4. CEQAnet: Port Costa Wharf Deconstruction (SCH 2013112033), Port Costa Area GPA (SCH 1982030915), Hivest GPA (SCH 1983012504)
5. County Ordinance Code (GoCodebook): Division 84, Chapters 84-50, 84-52, 84-66, 84-86, 84-90
6. Contra Costa Clerk-Recorder, Documentary Transfer Tax

Note: Parcel zoning, current sewer rates after FY 2023-24, the final adoption of the 2024 discharge permit, and water service details were not verified.

This page is general information, not legal or tax advice. Last reviewed October 2026 by Matthew Martinez.

Related: Port Costa real estate guide · Multifamily property in Port Costa · Commercial real estate services