Berkeley: What the Next Foot of Dredging Buys

Dredging depth and shoreline access

Berkeley's South Cove Sailing Basin presents two connected investment decisions: restore safe access across a deteriorating shoreline, and choose how much additional sailing time to buy through dredging. The city's current seawall programme needs construction funding identified by December to target the June or July 2027 in-water window. Its earlier dredging study tests the depth choice by comparing the extra excavation cost with the extra hours of access. [1, 2]

A funded design still needs a construction season

High tides breached the degraded seawall in June 2026, according to the city. A surface hole about six inches across opened near the middle dock, above a larger cavity whose extent remained uncertain. Vehicle access was prohibited; boats could be carried to the hoists. Continued loss of material beneath the surface threatens access to the hoists, docks and Bay Trail. ^[1]

The city has funding for design development and permitting. Construction funding remains unidentified. Its normal in-water work window runs from mid-June to November, and it needs the funding decision by December 2026 to organise a June or July 2027 start. A later funding decision can push construction into a subsequent year's window. ^[1]

That sequence affects the value of a dredging investment. Extra depth supports use of the basin only while users can reach it safely. A funding appraisal should therefore show the dredging benefit alongside the seawall access programme, with the periods of restricted access visible in the operating assumptions.

The city's depth comparison

The November 2024 community study compared three dredging options across Areas A, B and C. The example applied hourly observed tides from NOAA station 9414750 near Oakland, using 2022 as a representative year. It assumed a three-foot water-depth requirement at the launch area and a sailing day of 08:00-17:00 in November-April and 07:00-19:00 in May-October. Those assumptions define the hours below. [2, slide 13]

The figures are the city's 2024 illustrative estimates. Its lower and higher unit rates represent the study's maintenance-work and new-work classifications. The Dredged Material Management Office's determination and sediment assessment govern the disposal requirements. The table is an option comparison, with its original price basis retained. [2, slides 11-13]

The marginal hour becomes more expensive

The -2 ft option captures 962 of the example's 1,592 hours initially unavailable for sailing. Moving to -3 ft adds 60,000 cubic yards and gains another 366 hours. Moving from -3 to -4 ft adds 85,000 cubic yards for a further 245 hours. Dividing each cost increment by its additional hours gives a sharper funding test:

IMWO calculations use the differences between the published options, rounded to the nearest dollar per modelled hour. The ratio compares a capital-cost increment with the additional access in one representative tide year. In either price case, the final increment costs about 2.12 times as much per additional hour as the preceding increment. The deepest option has the greatest modelled availability; the shallower options buy the first increments of access more cheaply.

The choice depends on who can use those extra hours. A club with demand concentrated near low tide may value the final 245 hours highly. A programme whose operating hours, staffing or accessible launch facilities limit use may capture fewer of them. The next appraisal should assign the recovered hours to actual operating periods and user groups, then test the funding requirement against that use.

Reprice the material route and the access programme together

The city's dredging page records completed sediment sampling and submission of the results to DMMO in December 2025. It says the team is awaiting a determination on post-dredge requirements, which will substantially affect costs. Its announced agenda for the 28 October 2026 meeting included the sampling results and seawall repairs. [3, 4]

The published hydrographic drawings use bed data collected on 7-8 March 2024, with elevations in US survey feet relative to mean lower low water. Their vertical control uses NOAA station 9414816 and the YACHT 1947 benchmark. The option model's 2022 hourly tide series comes from a different station, 9414750. An updated appraisal needs to carry the bed survey date and vertical reference through its quantity calculation, alongside the tide series used to value access. ^[5]

For a preferred depth, the appraisal should carry a current excavation quantity, the applicable handling and disposal route, and the cost of mobilisation and repeat campaigns. The 2024 unit-rate sensitivity already shows how strongly classification changes the funding requirement. A current estimate must also account for the timing and cost of maintaining the chosen depth.

The immediate funding decision is the seawall construction window. The dredging decision should follow a depth-by-depth account of usable hours, material costs and access availability. Keeping those quantities in the same appraisal allows Berkeley to buy an operating improvement that its shoreline facilities can actually support.