Aquifer interests will likely clash with City’s density plans
Between (karst) rock and hard place: Rice discusses state of our water.
If the Edwards Aquifer Authority survives its fourth round before the Texas Supreme Court (see “Rule of Fracture
”), that won’t be the end of its fight to protect the sea of near-pristine water beneath us. The Authority must still do battle with the developers and planners whose attraction to the rolling hills and trickling creeks of Northwest Bexar threaten to continue contaminating the city’s primary drinking-water source.
Toward that end, the Authority has prepared a “concept memorandum” examining the potential impact tougher rules would have on decreasing contamination by decreasing the amount of asphalt and concrete that could be poured over the recharge zone in the west and northwest portions of Bexar County. Authority officials are also considering setting, for the first time, defined water-quality standards, EAA spokesperson Roland Ruiz said today.
While the contaminants traced so far have been well below any federal drinking water act restrictions, there are concerns about the cumulative impact of ingesting low-levels of pesticides like atrazine, hydrocarbons from diesel spills and automotive runoff, and the variety of pharmaceuticals that have started to show up in waterways across the country.
“When we find pesticides or chlorinated solvents in the water, we know they’re coming from human activity,” George Rice, a groundwater hydrologist and EAA board member, said at a presentation last week. “Just as with surface water, groundwater degradation is tied to urbanization.”
It’s important to remember that one of the reasons our aquifer has remained so clean (apart from one well-known Superfund site
beneath Leon Springs) is that for most of the city’s history San Antonio developed outside the recharge zone. We’ve lived and worked atop what is called the “artesian zone,” where the aquifer pops up through the rock and soil in the form of springs and creeks.
The recharge zone is 1,250 square miles of permeable rock pocked with caves and sinkholes running from Kinney County more than 100 miles to western San Antonio before curving away to the northeast just beyond New Braunfels.
But something began to happen in the middle of the last century that is well illustrated in this aerial photo series of the intersection of 410 and San Pedro in North San Antonio. This is not a recharge area, but it is illustrative of development occurring further west that is.
Impermeable roadways and rooftops that help flush rainwater down the aquifer chute (along with the dribbled gasoline, antifreeze, metallic brakepad “fluff,” pet waste, etc.) grew from around 4 percent to about 90 percent in 50 years.
By examining research from the U.S. Geological Survey, Rice and others have determined a “strong correlation” between impermeable surfaces and water contamination exists, appearing to hit a threshold between 10 and 20 percent impervious cover after which the amount of contamination begins to increase exponentially. But my attention sharpened with the following chart.
Those red dots represent all the public water wells (SAWS, mostly) where industrial solvents were detected between 1982 and 1998. That mass of redness in southwest San Anto? That’d be toxic Kelly AFB, fast becoming the Port of San Antonio.
If contaminants have an easy time getting into the Edwards Aquifer through the recharge zone, the system of transport within it is extremely complex. Some water flows through from the west to east at a rate of several miles a day. Other pockets may only shift by inches during the same period.
Even so-called Best Management Practices, fancy pollution-control efforts mandated by federal and state regulators in the hopes of reducing the amount of pollution that can reach a water body, fail to stop even half of many contaminants headed for nearby waterways.
But the needed debate between increasing regulation versus a future of multi-million dollar bond elections for the construction of water treatment plants in San Antonio hasn’t quite picked up yet. Water quality is a long way from registering in San Antonio’s hive mind. Another chart — this one from the EAA — suggests this ignorance can’t long continue much longer.
Rice’s prescription for interrupting the trend lines above? “We need to stop urbanizing the vulnerable parts of the aquifer.”
Expect to hear more about impermeable-cover limits and water quality in August when the EAA board gets together for their annual work session. When an official proposal finally rolls out, likely suggesting an across-the-board 20-percent impermeable cover limit for the recharge area, it will be followed by a lengthy public comment period, Spokesman Ruiz said. That likely won’t be till winter.
But on Friday, the City of San Antonio unveils its development goals
for North San Antonio, launching its own round of public meetings. Many eyes will be looking at the recharge zone, I know. And there’ll be plenty of noise to follow should the City’s plan suggest high- to middlin-density over it, as some are suggesting.
Plan to be there.* Oh, and thank Rice for all the nifty graphics when you see him.
Posted by gharman on 6/9/2010 6:50:02 PM
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