Implementation and Start-Up of a Multi-Benefit Urban Lake - The Echo Park Lake Rehabilitation Project
Historic Echo Park Lake is one of the City of Los Angeles’ crown jewels of parks and a major component of the City’s Proposition O Program. The main objectives of the rehabilitation project are to improve water quality in the lake; help the City meet current and future TMDL requirements; and comply with the Regional Water Quality Control Board's intent to restore the lake to its existing and potential beneficial uses. To accomplish these objectives, the improvements were categorized in three major elements: in-lake improvements; vegetation, habitat and parkland improvements; and parkland structural Best Management Practices (BMPs) for improving water quality in the lake. The in-lake improvements include draining the lake, removing the top layer of sediments, replacing the lake liner with a bentonite-enhanced clay liner; reconfiguring the outlet structure; providing a lake water recirculation system; and installation of an earthen fill partition berm to comply with Dam Safety regulations. The vegetation, habitat and parkland improvements include Lotus bed restoration, lake edging improvements, and installation of porous paving in a perimeter path. The BMPs include installation of hydrodynamic separators, constructed wetlands, rain gardens, grassy swales, and implementation of an integrated irrigation system.
The objective of this presentation is to describe the evaluation and design efforts as well as the innovative manner in which key project challenges were addressed though stakeholder outreach while maintaining a focus on water quality objectives, water conservation, and stakeholder input on the Project. In addition, the project opened to the public in late spring of 2013, so valuable information on the start-up operation will be shared.
Public and stakeholder outreach meetings were held throughout the early phases of the preliminary design efforts to garner public input. Feedback from the public that has significantly shaped subsequent development of water quality features of Project includes the following:
• Birds are embraced at the lake and the Park, so nutrient loadings will be accommodated.
• Constructed wetlands within the lake are acceptable to achieve water quality goals.
• Restoration of the existing Lotus Beds is an important feature of the Project.
Evaluations were conducted to determine the treatment capacity and costs for the following options:
Option 1 – Constructed wetlands to treat the mean daily dry season flow and WQE
Option 2 – Constructed wetlands to treat 50 percent of the mean daily dry season flow
Option 3 – Constructed wetlands to treat 50 percent of both the dry season flow and the WQE.
Option 4 – A mechanical treatment system to treat the mean dry season flows and the WQE.
The recommended project will consist of approximately 4.2 acres of constructed wetlands with a 600 gallon per minute recirculation system that is operated continuously. The recirculation system will offer the flexibility to selectively direct flows to wetland areas located around the lake, as well as the Lotus Beds. An aeration system and other features were incorporated into the design to allow for enhanced management, maintenance and operational flexibility.
The project opened to the public in late spring of 2013. Since that time the City has taken over operations and maintenance from the construction contractor. This presentation will share evaluation and design results, and lessons learned during implementation, and start-up. The presentation will also provide valuable information for other agencies who are considering lake restoration as a means of achieving water quality results.