There have been various early attempts to clean up the river.  Front Street prior to 1866 was the original “Main Street,” but couldn’t expand below Soquel Avenue because of apple orchards blocking the way.  So the downtown businesses moved to Pacific Avenue, leaving the old Front Street without a modern plumbing system, in which human waste flowed directly into the San Lorenzo.  Upper Front Street became Chinatown on the riverbank side of the street, and at low tide, a stench sometimes spread over Pacific Avenue.  Chinatown burned down in 1894, and in rebuilding, the plumbing was modernized.

At one time, there was a dump north of the Soquel Avenue bridge, and the City Council began restricting tin-can dumping, which could float down river, leaving sharp knife-like debris for barefoot swimmers.   

Tannery vats emptied into the river could make it run red, or foam, even though the outfall of Pogonip Creek was a popular boys swimming hole.  The tannery was quite conscientious in developing the most non-polluting methods, making it a leader in the industry nationwide.

Another problem was the dumping of sawdust in the river.  This non-toxic substance was lethal in fish kills, by making it difficult for gills to extract oxygen from the water.  Fred Swanton had become interested in tourism, and the San Lorenzo River drew in the anglers, so the fish population needed to be protected.  Anti-pollution laws were passed, and in 1905 a Fish Hatchery was built in Brookdale to increase the fish population.  The May 1st opening of fishing season brought a surge of fishermen to town, filling all the hotels (most within a block of the river), and the three riverside campgrounds within city limits.  By 1955, the San Lorenzo had become “the most fished river in the state of California.”

After the 1955 Christmas Flood, a radical redesign of the river was undertaken, clear-cutting all the trees and foliage, straightening and narrowing the river to produce new real estate opportunities, and installing levees.  Without overhanging trees, there were no cool places for the fish to congregate, and the fish population plummeted. 

Remaking a river into a concrete drainage basin without foliage, may serve certain purposes, but river health is not one of them.  The health of the river is measured not just by the cleanliness of the water, but by flow, depth, composition of the river bottom, percolatrix (seepage zone), aquatic creatures, and riparian plantings.