Section 319
NDNPDINT SOURCE PRPGRAK SUCCESS STORY
Watershed Restoration Efforts Improve Dissolved Oxygen Levels
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Excess nutrients from urban and agricultural runoff in the Chorro Creek
watershed contributed to the growth of nuisance algae. The break-
down of the algae caused dissolved oxygen levels in Chorro Creek to decline, preventing the creek from
supporting its cold freshwater habitat designated use. As a result, California's Central Coast Regional
Water Quality Control Board (CCRWQCB) added 14 miles of Chorro Creek to California's 1998 Clean
Water Act (CWA) section 303(d) list of impaired waters for dissolved oxygen. Public and private landown-
ers implemented a variety of water quality restoration efforts to reduce nutrients, including upgrading a
wastewater treatment plant, restoring wetlands and stream channels, removing livestock grazing from
riparian areas, and controlling erosion. Water quality improved, and the CCRWQCB has proposed removal
of Chorro Creek from the state's 2008 CWA section 303 (d) list of impaired waters for dissolved oxygen.
Problem
Chorro Creek drains into the Morro Bay Estuary (an
estuary of national significance) and is on central
California's coast in northern San Luis Obispo
County, northwest of the city of San Luis Obispo.
Chorro Creek is designated as a critical coastal
area along the central coast of California: for more
information, see www.coastal.ca.gov/nps/Web/
cca _ morro.htm.
Nutrients (nitrogen and phosphorus) and elevated
temperatures in Chorro Creek fuel the growth of
nuisance algae, which decrease dissolved oxygen
levels. Sources of nutrients in the creek include
land-based nonpoint source runoff, point source
discharge and animal waste. The 27,670-acre
Chorro Creek watershed is composed mostly of val-
ley grassland, coastal scrub and oak savanna, along
with mixed conifer forest and oak woodlands in the
upper elevations (Figure 1). The watershed supports
agricultural uses, with some low-density residential
and commercial areas.
The CCRWQCB first added Chorro Creek to the CWA
section 303(d) list in 1998 and identified it as being
impaired by nutrients. In 2004/2006 the CCRWQCB
also listed Chorro Creek as impaired because of low
dissolved oxygen levels. Data show that the water
quality objective for the cold freshwater habitat des-
ignated use was not being met. The numeric target
used to protect the cold freshwater habitat desig-
nated use is a minimum concentration of at least
7.0 parts per million (ppm) of dissolved oxygen. This
concentration is thought to be adequate to protect
the creek's steelhead trout populations.
Figure 1. This fencing and revegetation project occurred
along a tributary in Chorro Creek's valley grassland area.
Chorro Creek stakeholders have a long history of
actively addressing water quality and ecosystem
health in Chorro Creek. The stakeholders' coordi-
nated efforts to monitor and restore the waterway
prompted the CCRWQCB and other agencies and
organizations to nominate the watershed for the
National Estuary Program.
The U.S. Environmental Protection Agency approved
the Chorro Creek Nutrients and Dissolved Oxygen
TMDL and Implementation Plan on July 19, 2007.
The TMDL identifies the main factors influencing
dissolved oxygen levels in Chorro Creek as respira-
tion of benthic algae, lack of turbulent flow, loading
of nutrients and increases in water temperature.
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Project Highlights
Efforts to restore and monitor Chorro Creek have
been ongoing since the early 1990s. An estimated
40 to 60 percent of managed public and private
lands in the watershed are now operated with water
quality management prac-
tices in place. Key projects
include restoring Chorro
Flats floodplain, which is
designed to reestablish
riparian habitat and trap
sediment upstream of Morro
Bay. In this project, partners
converted approximately
100 acres of agricultural land
to a floodplain by realigning
the Chorro Creek channel
(i.e., removing levees and
planting appropriate native
riparian vegetation to trap
sediments). The project
restored approximately 67
acres of riparian and wetland
habitat (Figures 2 and 3).
Figure 2. A view of the Chorro
Flats floodplain before the
restoration.
Figure 3. After restoration,
Chorro Flats' channel sinuosity
and riparian vegetation has been
reestablished. For additional
photos, see www.pwa-ltd.com/
projects/pr _ res _ chorro _ flats.
html.
Figure 4. Building this new
wastewater treatment plant
helped remove point source
discharges from Chorro Creek.
Other projects included
switching from conventional
(i.e., free roaming) grazing to
intensive rotational grazing
with offchannel watering
facilities; excluding cattle
from the riparian corridor
adjacent to upper Chorro
Creek and Dairy Creek; and
replacing an aging waste-
water treatment plant at
the California Men's Colony
Prison (Figure 4). In addi-
tion, the CCRWQCB and the
California State Polytechnic
University implemented a
study comparing Chumash
and Walters creeks (tribu-
taries to Chorro Creek) to
evaluate and demonstrate
how erosion control practices
can improve water quality.
Actions implemented in the Chorro Creek
watershed are consistent with Morro Bay's
Comprehensive Conservation and Management
Plan (CCMP). The CCMP is a state- and federally-
approved plan that guides the work for the Morro
Bay National Estuary Program (MBNEP).
Results
California's Central Coast Ambient Monitoring
Program and MBNEP have collected and analyzed
water quality samples in Chorro Creek. Data
collected since 2002 show that water quality has
improved. Dissolved oxygen levels have stabilized
above 7.0 ppm and now consistently support the
creek's cold freshwater habitat designated use.
On the basis of these data, the CCRWQCB proposed
to remove 14 miles of Chorro Creek from California's
2008 CWA section 303(d) list for its dissolved oxy-
gen impairment. While data demonstrate that resto-
ration efforts have restored dissolved oxygen levels,
stakeholders will continue to implement practices to
address the remaining nutrient impairment.
Partners and Funding
Partners involved in protecting and enhancing
the Chorro Creek watershed include the Natural
Resources Conservation Service, Coastal San
Luis Resource Conservation District, California
Coastal Conservancy, MBNEP, Farm Bureau, Bay
Foundation of Morro Bay, San Luis Obispo County,
California Men's Colony Prison Water Treatment
Plant, Camp San Luis Obispo, U.S. Environmental
Protection Agency, CCRWQCB, California State
Water Resources Control Board and numerous
private landowners.
Over the past 15 years, stakeholders have spent
more than $10 million (local, state and federal
dollars) to restore the Chorro Creek watershed.
Approximately $4 million in CWA section 319 funds
have supported planning ($300,000), monitoring
($1 million) and implementation ($2.7 million) activi-
ties. Additionally, CWA section 319 funds supported
one half-time CCRWQCB staff position to support
the Chumash and Walters Paired Watershed Study
and the Chorro Flats floodplain and riparian corridor
restoration projects.
I
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-09-001R
August 2009
For additional information contact:
Howard Kolb
Water Resources Control Engineer
Central Coast Regional Water Quality Control Board
805-549-3332 • Hkolb@waterboards.ca.gov
Katie McNeill
Central Coast Regional Water Quality Control Board
805-549-3147 • Kmcneill@waterboards.ca.gov
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