Colorado Lagoon is one of Long Beach’s most familiar, and most misunderstood, water bodies. To some, it looks like a quiet, enclosed lagoon. To others, it’s a place that has long struggled with water quality challenges. What’s often missing from the conversation is the deeper story: Colorado Lagoon is not a naturally occurring system in its current form, and the conditions we see today are the result of more than a century of human decisions about land use, circulation, and infrastructure.
With construction actively underway on the current phase of restoration, this is a good moment to pause and look at the full picture. Understanding how Colorado Lagoon came to be, and why the current work is happening now, helps explain not only what’s changing at the lagoon itself, but why these changes matter for connected waters like Alamitos Bay.
This update walks through that history and explores what the current restoration effort aims to do, and why long-term monitoring is essential as the system adjusts.
Pre-1900s | Tidal wetlands and estuary
Before urban development, the area now known as Colorado Lagoon was part of a broader tidal wetland and estuarine system connected to Alamitos Bay. These wetlands experienced regular tidal exchange and supported diverse plant and animal life.
Early 1900s | Dredging and land creation
As Long Beach developed, wetlands throughout the area were dredged and filled to support recreation, boating, and housing. Colorado Lagoon emerged during this period as a human-made waterbody, shaped by dredging rather than preserved as a natural lagoon.
1925 | Construction of Marine Stadium
Marine Stadium was built to host rowing events for the 1932 Olympics. Its construction and associated infrastructure significantly reduced tidal circulation between Colorado Lagoon and Alamitos Bay, limiting flushing and altering natural water movement.
Mid-1900s | Declining water quality
With reduced tidal exchange and increasing urban runoff, Colorado Lagoon experienced stagnation, sediment accumulation, nutrient loading, algal blooms, and fish kills. These conditions were not natural but resulted from altered hydrology and surrounding development.
Early 2000s | Restoration planning begins
Community advocates and the City of Long Beach began formal restoration planning, recognizing that long-term water quality improvement would require restoring circulation, managing sediments, and rebuilding habitat.
2008–2012 | Initial restoration phases
Early phases focused on dredging contaminated sediments, rerouting storm drains, improving shoreline habitat, and creating wetlands to reduce pollution inputs and improve ecological conditions.
2019 | Port of Long Beach funding approved
The Port of Long Beach approved major funding for the Colorado Lagoon Open Channel Project as part of environmental mitigation efforts, helping finance the final phase of restoration focused on hydrologic reconnection.
2023–present | Open Channel Project construction
Construction is underway on the Open Channel Project, designed to reopen and stabilize a tidal connection between Colorado Lagoon and Marine Stadium. This phase aims to improve flushing, water quality, and habitat function as part of a decades-long restoration effort.
Before sharing where to find current construction information, it’s important to acknowledge that this moment didn’t happen on its own. The restoration of Colorado Lagoon is the result of years of sustained community advocacy, led in large part by Friends of Colorado Lagoon. For more than two decades, this group has worked alongside residents, scientists, and the City of Long Beach to push for science-based restoration, improved water quality, and long-term ecological health at the lagoon. Their efforts helped move the project from vision to reality, keeping attention focused on circulation, habitat, and water quality even when progress was slow. We strongly encourage folks to follow their work and community updates at www.coloradolagoon.org.
For those looking for official construction timelines, progress updates, and notices, the City of Long Beach is maintaining a dedicated project page here.
As folks follow along with construction updates, it’s natural to wonder what all of this work means for the future of Colorado Lagoon itself. Colorado Lagoon will remain its own place, a lagoon with its own character, shoreline, and rhythms. The restoration work isn’t about turning it into open bay, but about restoring a healthier connection so water can move in and out more naturally. In coastal systems, separation and connection can exist at the same time, and that balance is what helps lagoons thrive.
Sources:
http://www.coloradolagoon.org/
https://longbeachize.com/articles/a-look-inside-long-beachs-largest-infrastructure-project-connecting-colorado-lagoon-to-marine-stadium/
https://www.coloradolagoon.org/restoration.html
https://www.longbeach.gov/citymanager/tidelands/colorado-lagoon-restoration/
https://polb.com/port-info/news-and-press/port-agrees-to-fund-colorado-lagoon-upgrades-07-11-2019/
https://www.longbeach.gov/pw/projects/colorado-lagoon-project/