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Last Edited: 9/5/2008

Santa Cruz Harbor, Santa Cruz - Public Health Activities

The Environmental Health Investigations Branch, of the California Department of Health Services (CDHS), conducted an evaluation of possible exposure to hydrogen sulfide that is emitted into the air as a result of the placement of dredging material on the beach near the Santa Cruz Harbor. This evaluation and its findings are presented in a report called a health consultation. While hydrogen sulfide emissions resulting form the harborís dredging activities appear to pose no apparent public health hazard, CDHS is making several recommendations to protect public health.

The Santa Cruz harbor is located in the City and County of Santa Cruz, and has been involved with the dredging program since 1964. Dredging is conducted annually and usually begins in early November, continuing through the storm months, and into April. The dredged material is a combination of sand, natural organic plant life (seaweed), and seawater.

Aerial photo of the undredged opening of the harbor (Photo taken in 1976)

Dredge operation demarcated to beach visitors (Photo taken on March 28, 2005)

Dredging of the Lower Harbor starts in November and ends in April. The debris from dredging the Lower Harbor is typically used as beach replenishment.

Beginning in the 1980s, nearby residents voiced their concerns about odor and health issues related to the dredging. In 2006, the Santa Cruz County Environmental Health Services requested assistance from the Environmental Health Investigations Branch of CDHS in evaluating neighborhood exposure and health concerns telated to hydrogen sulfide that results from the Santa Cruz port district's dredging. 

Click to view the full document Santa Cruz Harbor Health Consultation (6/6/07) 

Note: CDHS conducted this health consultation through a cooperative agreement with the federal Agency for Toxic Substances and Disease Registry

Findings and Recommendations of CDHSís Review

CDHS reviewed the port districtís protocols and found the non-emergency action levels to be adequate in protecting the residents and beach visitors while the beach disposal is occurring. CDHS found that 97.7% of the time when dredging occurred on the beach over the past three years, the levels of hydrogen sulfide were below screening levels that would not be expected to cause health concerns.

On several occasions in late 2005 and early 2006, the levels averaged above the screening levels for periods of time greater than one hour. Also, during certain monitoring periods, hydrogen sulfide levels were very high for short periods of time, greatly exceeding the screening value. Case studies and ongoing research suggests respiratory, neurological, and even cardiac effects may be possible from lower levels of hydrogen sulfide over intermittent or longer exposure periods.

However, given the limited time that these high emissions occurred and the dilution that would occur from the monitoring station to the nearest beach visitor or neighbor, it is not possible to connect health effects to the observed hydrogen sulfide emissions with the Santa Cruz harbor beach disposal site.

In order to ensure the publicís health, CDHS made the following recommendations:

  • the port district should comply with the hydrogen sulfide protocol and establish a clear understanding with their dredging contractors that the dredging should stop for the day when the action levels are exceeded;
  • the port district should continue the hydrogen sulfide sampling for the upcoming dredging seasons;
  • the port district, with the assistance of the other regulatory agencies, ensure the dredging is performed off shore and under water as much as possible to dissipate the hydrogen sulfide;
  • the harbor should post additional signs on the beaches, warning of possible health implications during dredging;
  • the port district should create a better delineation around the discharge area;
  • the air district should start a policy where they archive their inspector notes; and
  • the dredging crew should indicate on their field notes when the operations on the beach are being conducted under emergency conditions or emergency variance.

Related Topics


Project Location

  • CA Counties: Santa Cruz