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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