Apache, a Houston oil and gas company, announced almost a year ago that it had discovered 15 billion barrels of oil and gas under 350,000 acres here in West Texas. Many worried: Visitors from near and far flock to the famous spring-fed pool at nearby Balmorhea State Park. If oil and gas drilling and hydraulic fracturing broke into the springs and ruined the pool, what, they asked, would become of this 500-person town, already struggling to make ends meet?