In a region that lauds itself as a bastion of environmental progress, the 100 billion gallons of polluted runoff that flows out of storm drains annually is Los Angeles’ dirty secret.

When rain water hits L.A.’s largely impervious landscape it drains into run-off channels that criss-cross through the county accumulating a toxic slew of chemicals, oil, fertilizer, trash, hard metals, and bacteria before entering a storm drain and spewing out into the ocean.

Over 30 billion gallons of this polluted mixture exits through 200 drains into the Santa Monica Bay each year, according to LA Sanitation & Environment. This watershed incorporates 55 miles of coastline, but several key drains are located in the City of Santa Monica, including the Pico-Kenter Storm Drain and the Pier Storm Drain.

When significant rain events flush polluted run-off into the ocean, the environmental impacts can be devastating. It can lead to fish die-offs, marine life ingesting plastic, spread of E. coli infections, and permanent reproductive harm to aquatic life. These impacts are also felt on ecosystems around the L.A. River and the Ballona Wetlands.

Although many initiatives are underway to mitigate the amount of polluted runoff entering L.A.’s waterways, both representatives from L.A.

Waterkeeper and Heal the Bay Foundation said that the situation has not significantly improved over the past decade.

Stormwater runoff is difficult to address for two key reasons: responsibility for the issue is widely diffused and a vast range of pollutants contribute to the problem.

The first reason, diffusion of responsibility, an issue of geography and of governance.

The Los Angeles County Flood District encompasses a vast area of 2,700 square miles and approximately 2.1 million land parcels within six major watersheds.

The storm-water runoff that winds up on Santa Monica’s beaches passes through several dozen different municipalities, spanning potentially hundreds of miles and picking up numerous pollutants on its journey to the sea. However, the MS4 permits that are required to release stormwater runoff are only issued to the entities in charge of the point of release.

“Having a law that says you as the owner of that pipe that sticks into ocean are responsible for the water quality that comes out of it makes sense legally, but practically it is a much more difficult problem to wrap your arms around because the folks that are actually creating the pollution are not the ones who own the system,” said Dan Lafferty, deputy director for water resources, L.A. County Public Works.

As a result of these geographic and governing challenges, very few MS4 storm drain permits are in compliance with the water quality standards set by the EPA’s landmark Clean Water Act.

“We have estimated the cost for compliance for the region to meet the standards within the MS4 permit everywhere is roughly $20 billion over 20 years and that is all money that has to be raised at the municipal level,” said Lafferty.

L.A. County residents voted to pass Measure W in 2018, a parcel tax providing sorely needed municipal funds for stormwater mitigation efforts, however Lafferty said this only amounts to 20 percent of the funding needed to bring drain systems to EPA compliance.

The management of stormwater run-off in Santa Monica is a complex affair. Although individual upstream municipalities that contribute pollutants are not directly involved, a web of City and County departments are.

The Department of Public Works maintains Santa Monica’s storm drains and manage the beach areas around the runoff. The City of L.A. Department of Sanitation conducts water quality monitoring and the County Department of Public Health issues warnings when swimming is dangerous at certain beaches. The City of Santa Monica conducts runoff mitigation efforts in coordination with the City of El Segundo, City of L.A., the County and the County Flood Control District.

In addition to the challenges posed by the spread of responsibility and the vast area of land that drains stormwater into the ocean, run-off is difficult to deal with because of the wide variety of pollutants it carries.

“Storm pollution is 1,000 different things and so it needs 1,000 different bandaids to fix it,” said Melanie Rivera, staff scientist at L.A. Waterkeeper.

Common pollutants carried in stormwater include E.coli, streptococci, PCBs, nitrates, phosphates, heavy metals, pesticides, fertilizers and plastic particles, which all originate from different sources.

“The cumulative effect of all of these contaminants can either directly cause a fish kill with acute toxicity or can have long-term effects like reducing their ability to reproduce and metabolize food, disrupting the resilience of these ecosystems,” said Annelisa Moe, water quality scientist at Heal the Bay Foundation.

Even when targeted efforts are made to stop the spread of certain pollutants, their harmful effects can persist for a long-time in local ecosystems.

According to Moe, Heal the Bay still finds high DDT levels in the Ballona Creek, even though the chemical is banned, because DDT takes years to break down.

“There are studies that show a huge impact of DDT on our ecosystems in the Bay, including sea lions who are having issues with reproduction and even experiencing death because of DDT levels,” said Moe.

In addition to the damage wreaked by chemicals and bacteria, the particulate matter swept into the water can have a series of deleterious effects. Environmental organizations track the impact of this by measuring the TTS, or Total Suspended Solids, present in stormwater runoff.

“When water is discharging with high amounts of TSS it can cause the water to be very turbid, which will prevent light from penetrating into the ocean and make it difficult for aquatic plants or phytoplankton to produce food,” said Rivera. “When those suspended solids settle on a substrate, those particles completely cover bottom dwelling fish and organisms, which essentially suffocates them.”

Stormwater runoff also makes the ocean dangerous for humans to swim in and it is recommended that people stay out of the water, and especially away from storm drains, for 72 hours following a significant rain event.

Not all cities experience the environmental and health impacts of stormwater runoff as acutely as Los Angeles.

Most cities on the East Coast, and notably San Francisco on the West Coast, have a combined sewer system, meaning that wastewater and stormwater are drained together.

The benefit of this is that most stormwater is processed at sewage facilities and is not released into waterways. The great risk of this system, and the reason it is no longer used in constructing new sewers, is that a significant rain event can overwhelm the system and result in a large discharge of raw sewage.

L.A. County began building its stormwater drainage system in 1915. Prior to the construction of a flood management system, stormwater would routinely take different run-off directions and this high level of unpredictability caused massive property damage.

L.A.’s storm water drainage system was constructed to concentrate drainage in central waterways, leaving the rest of the County open for construction. As a result, the area became highly developed with impervious surfaces such as concrete and asphalt, and the amount of green area available for natural drainage was greatly diminished.

“The choices we would make today are different from the choices that were made 100 years ago,” said Lafferty. “The driver back then was two-fold: I want certainty from flooding and I want to maximize developable space. There was a lot that was lost when that decision was made in terms of green space, in terms of habitat, in terms of recreation.”

Editor’s note: This article is the first in a two-part series. To learn about the ongoing efforts to mitigate the effects of stormwater run-off pollution read part two here.