Section 319
NONPOINT SOORGE PROGRAM SOGGESS STORY
Texfo
Adopting Conservation Tillage and Repairing Septic Systems Improves
Water Quality in Oso Bay
Waterbodies Improved
Low levels of dissolved oxygen (DO) in Texas' Oso Bay
caused by high nutrient and organic loading prompted the
Texas Commission on Environmental Quality (TCEQ) to add the bay to the Clean Water Act
(CWA) section 303(d) list of impaired waters for failure to support its aquatic life designated
use. Extensive implementation of cropland best management practices (BMPs), repair and
replacement of failing septic systems, trash cleanups, and education and outreach took place in
the watershed and around the bay, leading to decreased nutrient and organic loading and higher
DO levels in the bay. As a result, in 2010 TCEQ removed Upper and Lower Oso Bay (segments
2485_01 and 2485_03, respectively) from the CWA section 303(d) list.
Problem
The combined watersheds of Oso Creek and Oso
Bay drain an area of approximately 235 square
miles in Nueces County, Texas (Figure 1). Oso Bay
is a shallow tertiary bay of about 2,963 acres that
empties into Corpus Christ! Bay. The watershed is
dominated by cropland in the western portion and
developed residential areas in the eastern portion.
Other activities in the watershed include petro-
leum exploration and refining, manufacturing, and
tourism.
Oso Bay is classified as having an exceptional aquat-
ic life designated use. To meet state water quality
standards, the bay must maintain a 24-hour average
for DO above 5.0 milligrams per liter (mg/L), and the
daily minimum grab sample may not be below 4.0
mg/L. Portions of Oso Bay were first placed on the
CWA section 303(d) list in 1996 for failing to meet
the state's DO criteria. Water quality sampling con-
ducted by Texas A&M University-Corpus Christ! in
2001 indicated that the lowest recorded DO values
in the bay were 1.9 mg/L (in segment 2485_01) and
0.45 mg/L (in segment 2485_03). On the basis of
these and other similar data, TCEQ added the entire
bay to the CWA section 303(d) list for low DO in
2004.
Low DO levels can be caused by elevated nutri-
ent levels, which result in algal blooms and other
oxygen-demanding materials decomposing in
water. Litter, failing septic systems, and runoff from
cropland and urban areas were identified as poten-
tial sources of nonpoint source pollution contribut-
ing to Oso Bay's impairment.
Figure 1. Oso Creek and Oso Bay are in southeast Texas.
Project Highlights
In September 2002 the Texas State Soil and Water
Conservation Board (TSSWCB) partnered with the
Nueces Soil and Water Conservation District (SWCD)
and local landowners to voluntarily implement BMPs
on agricultural land in the Oso Bay watershed.
Conservation tillage (Figure 2) was one of the main
practices used to reduce soil erosion. Through this
effort, 56 water quality management plans were
developed and implemented on 14,501 acres. The
U.S. Department of Agriculture's Natural Resources
Conservation Service (NRCS) also developed conser-
vation plans on more than 35,000 acres of agricul-
tural land in the watershed. Education and outreach
were provided by the SWCD, TSSWCB, and NRCS
through technical assistance to the landowners.
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Figure 2. Landowners adopted conservation tillage in the
Oso Bay watershed.
TSSWCB also partnered with Texas A&M AgriLife
Research and the U.S. Geological Survey to collect
and analyze water quality data in the watershed's
agricultural areas. These data were collected
pre-and post-implementation to determine the
effectiveness of BMPs. The Coastal Bend Bays and
Estuaries Program, Nueces County, and TCEQ part-
nered to repair, replace, or install septic systems
in the watershed from 2007 to 2009. The primary
area of focus was Tierra Grande colonia (an unin-
corporated subdivision) and nearby households.
Partners helped to install 21 new septic systems on
properties with no existing systems or with failed
systems. Additionally, 10 systems that were not
functioning at optimal capacity were repaired.
The Coastal Bend Council of Governments partnered
with Nueces County, Texas A&M-Corpus Christi, and
TCEQ Region 14 to address illegal dumping. As part
of an education campaign about illegal dumping, the
partners conducted 97 presentations at local schools
and community events from 2006 through 2010. In
addition, three public service announcements were
aired over a six-month period in 2006. The partners
also performed litter cleanups, including two events
(November 6, 2009, and July 23, 2010) at the State
Highway 348 bridge over Oso Bay. The cleanup
efforts removed more than four tons of trash and
debris. The partners installed four trash cans along
the bridge to encourage proper trash disposal. An
additional cleanup was conducted in the Tierra
Grande colonia on November 3, 2007.
Results
- D024-HourMinimum mg/L(2485_03)
- DO 24-Hour Average mg/L (2485_03)
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Figure 3. Twenty-four-hour DO monitoring data showed
improved DO levels in Lower Oso Bay.
tion 303(d) list showed that the daily minimum grab
sample and 24-hour average for DO levels in Upper
and Lower Oso Bay (Figure 3) complied with the
state's water quality standards. As a result, TCEQ
removed the Upper and Lower Oso Bay segments
from the state's CWA section 303(d) list of impaired
waters for DO. The success of this effort is attrib-
uted to the voluntary implementation of BMPs by
landowners and the use of education and outreach
through technical assistance. Landowners contin-
ued to implement agricultural BMPs with assistance
from TSSWCB, Nueces SWCD, and NRCS after the
assessment period, along with continued septic sys-
tem implementation, trash cleanup, and outreach.
Partners and Funding
Water quality monitoring data that were assessed
for the 2010 Texas Integrated Report and CWA sec-
Over $761,100 in CWA section 319 funds and over
$27,700 in state funds from TSSWCB, paired with
over $385,600 in non-federal matching funds from
Texas A&M AgriLife Research and local landown-
ers, supported efforts to collect and analyze
water samples and provide technical and financial
assistance for voluntary BMP implementation by
agricultural producers in the Oso Bay watershed.
Additionally, NRCS provided over $90,900 in Farm
Bill funding for technical and financial assistance to
develop watershed conservation plans.
More than $180,000 in CWA section 319 funds
from TCEQ, combined with $120,000 in non-federal
matching funds from the Coastal Bend Bays and
Estuaries Program, the Coastal Bend Council of
Governments, and Nueces County, was used to
install, replace, or repair septic systems, perform
litter cleanups, and provide outreach and education
in the Oso Bay watershed.
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-14-001HH
June 2014
For additional information contact:
Brian Koch
Texas State Soil and Water Conservation Board
979-532-9496 • bkoch@tsswcb.texas.gov
Tim Cawthon
Texas Commission on Environmental Quality
512-239-0845 • tim.cawthon@tceq.texas.gov
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