Page 484 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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442 Chapter 12 Urban Runoff and Combined Sewer Overflow Management

expenses are covered through a drainage utility fund that consists of monthly service
charges to the residents in the utility service area.
2. Urban Watersheds Ordinance. In 1991, the city council approved task force recommenda-
tions to include urban area watersheds among those covered by development ordinances.
This ordinance, created in response to increased pollution in Town Lake due to urban
runoff discharges, focuses on the urban watersheds not previously covered by the CWO. It
requires the implementation of structural controls in new developments undergoing site
plan review. All new residential, multifamily, commercial, industrial, and civic develop-
ment in the urban watersheds is required to construct water quality basins (either sedimen-
tation or filtration basins) or provide a cash payment to the city for use in an Urban
Watersheds Structural Control Fund. Structural controls must be used to capture the first
0.5 in. (13 mm) of runoff from all contributing areas. The Urban Watersheds Structural
Control Fund is used to retrofit and maintain structural controls where required in the
urban watersheds. In addition to this requirement, new developments in the urban water-
sheds are required to provide for removal of floating materials from stormwater runoff
through the use of oil/water separators or other practices. Redevelopment projects in the
urban watersheds are also included in this ordinance, where structural controls and the re-
moval of floatable materials are required. For redevelopment projects, the city has devel-
oped a Cost Recovery Program Fund to provide 75% of the cost of structural controls.
These funds are allocated through the drainage utility fund.
In urban watersheds, the critical WQ zone is the boundary of the 100-year floodplain
and is generally located 50 to 400 ft (15 to 120 m) from the waterway. As with the
Comprehensive Watersheds Ordinance, no development is allowed in the critical WQ
zone.
3. Other nonpoint source control programs. In addition to the CWO and the Urban
Watersheds Ordinance, Austin has developed other ordinances designed to reduce NPS
pollution from new developments and redevelopments. One of these, the Barton Springs
Zone Ordinance, provides special protection to watersheds contributing to Barton Springs,
a widely visited and used natural spring bathing area in Austin. This ordinance, created to
be a nondegradation ordinance with specific performance requirements, includes defini-
tions of waterways and development limits similar to those specified in the CWO. Only
one- or two-family residential development with a density of 1 unit per 3 acres (1.21 ha) is
allowed in the Barton Springs watershed transition zone, which extends up to 300 ft (90 m)
from the water body. In addition, new developments in the Barton Springs watershed must
comply with the following requirements: reduced pollutant concentrations compared with
the undeveloped conditions and discharge no greater than a specific maximum pollutant
concentration after development. The city measures these requirements quarterly on each
development through a developer-funded monitoring program. Additional NPS control
programs in Austin include:
• Land Development Code: Enforces landscaping regulations and protects trees and
natural areas.
• Underground Storage Tank Program: Develops guidelines for underground storage of
hazardous materials, permitting and inspection of these underground storage tanks, and
investigation of problems and response to emergency situations.
• Water Quality Retrofit Program: Involves engineering and building, with private
sector participants, permanent controls for already developed areas and those that
are producing stormwater runoff pollution problems for the city’s key receiving
waters.
• Water Quality Monitoring Program: Monitors and characterizes pollutants from
various land uses and structural controls, monitors surface and groundwater quality,
and develops water quality models and databases; also conducts specific studies on
known nonpoint source problems.