(From a preliminary US290 Task Force draft)
Temporary Controls
(to contain silt erosion during highway construction)* More upland controls designed to contain silt erosion at its source.
* Installation of detention ponds to capture silt prior to any grading of
soil.
* Better phasing of construction to reduce exposure of erodable material.
* Better training of engineers and inspectors on reducing silt runoff.
Permanent Controls
(to filter oil and grease from highway runoffafter road is in
use)
* Set measurable water quality standards for stormwater runoff.
* Identify and protect major aquifer recharge features from runoff.
* Set up a permanent maintenance program for water quality control devices,
budgeted from the inception of highway planning, and overseen by a Water
Quality Specialist.
* Minimize runoff volume from impervious cover by more use of infiltration
devices to ensure slow ground percolation to maintain creek baseflows.
Retrofitting Inadequate Water Quality Controls
* Construction of water quality ponds on parts of Loop 360 and MoPac thatcurrently lack them.
* Find an alternative to the vertical sand filters used in ponds on MoPac and
the Outer Loop that malfunction or perform poorly.
* Possible retrofit of the TxDOT Regional Water Quality Pond at Loop 360,
because of its proximity to Barton Springs, if monitoring shows that it fails
to protect Barton Creek.
Monitoring and Studies
* Groundwater tracing study to determine groundwater flow rates and velocity. * Study to determine baseline water quality in the Edwards Aquifer, to be
continuously monitored as urbanization increases.
* Permanent monitoring of effectiveness of water quality devices, to be
included in the budgets of highway projects from their inception.
* TxDOT should maintain records of water quality pond maintenance and
inspection.
* TxDOT should collect turbidity measurements during rain events to assess
effectiveness of sediment and erosion control. — N.E.
This article appears in December 13 • 1996 and December 13 • 1996 (Cover).