Degraded condition: frequent beach postings, State 303d i

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Prepared By City of Long Beach Public Works
Department And
The Little Lagoon That Could !
Colorado Lagoon Restoration
Feasibility Study
Presentation to Clean Beach Initiative Enclosed
Beach Symposium
August 17, 2005
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BackgroundThe Beach EnvironmentResponsesConclus
ion
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Colorado Lagoon
Underground Culvert
San Gabriel River
Marine Stadium
City of Long Beach
Alamitos Bay
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Background

• History
• Once part of historic Los Cerritos Wetlands.
• Dredged in 1923 to form Colorado Lagoon,
  connected directly to Marine Stadium.
• In late 1960s, area between Lagoon and M.Stadium
  filled and underground culvert installed.
• Current
• Multi-use lagoon recreation (swimming,
  picnicking), habitat, and storm drain basin.
• Degraded condition frequent beach postings,
  State 303(d) impaired water bodies list

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Circa 2004
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X Major System Storm Drain X Other (Local)
Drains
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X
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X
X
X
X
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X
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Work Status Tasks Complete in July
Colorado Lagoon Bathymetry

• Hydrograph

Elevation, Feet (MSL)
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Water Quality Problem Definition

• Bacteria Sampling 2000 - 2005
• Average 27 days per year of beach advisories
• During both dry and wet seasons
• Exceedances usually due to total coliform or
  E.coli / total coliform ratios
• Aug. 2004 sampling - storm drain concentrations
  order of magnitude higher than receiving waters

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Bacteria Water Quality Sampling Locations
B-25
B-26
B-24
City of Long Beach Sample Locations - Weekly MN
Sample Locations One Time Only Storm drain
outlet Knee-high water at 6 inch water depth
from surface From kayak at 6 inch water depth
from surface
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Colorado Lagoon Beach Advisories

2005 Dry Season Data Not Yet Available
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BackgroundThe Beach EnvironmentResponsesConclus
ion
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Circulation / Hydraulics

• Tidal range 4.5 feet versus 6.5 feet in
  M.Stadium.
• Lagoons low tides cut off by 2 feet
• Tidal residence times at least 1-2 weeks longer
  than for M.Stadium.
• Potential reasons for different tidal conditions
• Marine growth and sediment build-up inside
  culvert
• Structural sill inside culvert
• Rock basin at M.Stadium-end of culvert

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Work Status Tasks Complete in July

• Hydrology Study

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Work Status Tasks Complete in July

• Hydrograph

RMA4
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BackgroundThe Beach EnvironmentResponsesConclus
ion
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Alternatives

• Remediation
• Clean the culvert / remove structural impedances
• Open channel between lagoon and M. Stadium
• Storm drain diversions and treatment systems
• Bio-swales to treat dry weather runoff into the
  lagoon
• Dredge the lagoon to remove contaminated
  sediments
• Restoration
• Recontour side slopes to increase intertidal
  habitat area
• Remove non-native vegetation and plant native
  vegetation
• Recreational elements such as interpretative
  kiosks and a perimeter trail

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Storm Drain Treatments
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BackgroundThe Beach EnvironmentResponsesConclus
ion
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Lessons Learned

• Tidal gauge measurements provided invaluable
  data.
• For diverse urban watershed, very difficult to
  pinpoint pollutant sources instead, utilize
  regions diversion capability.
• Shopping list / pick-and-choose alternatives
  development approach.
• It is possible to develop restoration plan for
  multi-(competing)-uses waterbody.

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