Raul M. Rojas, Director, Public Works
cartoon pathogens

As well as being a countywide issue, Richardson Bay in East Marin and Tomales Bay in West Marin are both regulated under TMDLs for excessive levels of pathogens that cause water quality impairments.

Read more about what pathogens are, the potential sources, and what can be done to improve water quality.


What are Pathogens?

So what are pathogens? Simply put, they are parasitic organisms capable of causing disease in their hosts.

The waterborne pathogens that are causing the impairments in our bays are of fecal origin and made up of 3 groups of microorganisms:

  • Viruses - (Poliovirus, Hepatitis A)
  • Bacteria - (E.coli, Salmonella, Brucella)
  • Protozoa - (Cryptosporidium, Giardia)

Potential Pathogen Sources

There are many potential sources of waterborne pathogens, but here in Marin they can generally be broken down into two categories.

Human Sources

  • Failing septic systems
  • Faulty or clogged sewer laterals
  • Boat discharges
  • Sewage treatment facility overflows

Animal Sources

  • Animal agriculture - dairies, grazing lands, horse facilities
  • Municipal runoff - pet waste
  • Wildlife

Horse Owners

Stewardship on horse property is a major opportunity and responsibility. Topics on caring for the land, managing manure, and giving practical solutions to horse owners on what can be done to help protect the environment can be found on our main Horse Owners page. Whether an owner has one horse or operates a boarding facility, all equestrians play an important role in assuring that our watersheds are healthy and our creeks clean.

Pet Waste

Whether you gaze at Richardson Bay, play in the surf at Stinson Beach, hike to the heights of Mt. Tam, or stroll along Corte Madera Creek, the beauty of Marin will captivate you and keep you coming back for more. But when pet waste is improperly disposed, it can be picked up by water and washed into storm drains or directly into local creeks, bays or the ocean. Once in the water, pet waste contributes pathogens and nutrients that can negatively impact water quality. One of the ways that state and local agencies are working together to reduce the amount of pathogens found in our waterways is by eliminating the urban sources from the surrounding land.

Dog Waste

Did you know there are more than nineteen thousand licensed dogs with the Marin Humane Society? That's more than fourteen thousand pounds of dog poop a day! To protect the water quality in our creeks, bays and ocean, and the health of our families it is important for all dog owners to pick up after their pets!

  • Always bag your dog's waste and throw it away in the trash (NOT the green bin)
  • Pick it up and pack it out when enjoying one of Marin's dog-friendly hikes or walks around your neighborhood
  • Pick up pet waste in your yard - pathogens will stay for months to years and put you, your family, and the environment at risk
  • Don't use pet waste for fertilizer or bury it where food will be grown

Cat Litter

Dispose of kitty litter and cat waste properly by bagging the used litter and place it in the trash. Sanitary Districts do not allow flushing cat litter down the toilet. Even kitty litter made from pine or other natural materials cannot be placed in vegetable gardens or compost piles. If the cat waste carries pathogens, the temperatures in sewage treatment plants, composters, and digesters may not reach the high temperatures needed to kill the pathogens.

Rabbit, Tortoise and Small Animal Litter

Like kitty litter, soiled small animal litter and bedding material should be put in the garbage. The waste can also carry pathogens.