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discharge from the aquifer include Hueco, San Pedro, San Antonio, and Leona springs (Ogden, Quick,
<br />Rothermel, 1986).
<br />In addition to overlying sections of the recharge and contributing zones, the large -scale Paso Robles
<br />housing development and associated golf course will occur near two wells that supply water to the San
<br />Marcos National Fish Hatchery and Technology Center. This facility maintains captive populations of
<br />most of the associated Edwards Aquifer listed species. The construction of the housing development,
<br />subsequent chemical treatment of lawns, and application of wastewater effluent on the golf course
<br />could have adverse effects on the contributing and recharge zones, and ultimately on the quality of
<br />groundwater consumed in surrounding areas. Severity of these effects is unknown unless adequate
<br />analysis is performed.
<br />Contamination of the underlying groundwater could occur through the introduction of endocrine-
<br />disrupting compounds associated with some herbicides and insecticides, excess nutrients, and
<br />compounds that have been found to remain in reclaimed wastewater. For instance, a previous study
<br />assessing the efficiency of the San Marcos Wastewater treatment Plant found that more than 90% of
<br />compounds found initially in untreated influent that are known health risks are removed. However,
<br />some potentially harmful residuals, including known or suspected endocrine disruptors, were
<br />frequently detected, more than 60 percent, in the city's treated effluent, or reuse water. These included
<br />carbamazepine, triethyl citrate, tris (2- chloroethyl) phosphate (TCEP), triclosan, and caffeine. Other
<br />known or suspected endocrine - disrupting compounds that were detected in less than 60 percent of the
<br />City's effluent samples included sulfamethoxazole, coprostanol, NN- diethyl - meta- toluamide (DEET),
<br />nonylphenol, diltiazem, and estradiol. Many of these compounds are associated with pharmaceuticals,
<br />and some are classified as insecticides or flame retardants (Foster, 2007).
<br />Endocrine disruptors can interfere with the production and function of natural hormones produced in
<br />organisms, including humans. The recycling of wastewater onto the Paso Robles golf course and the
<br />residential use of herbicides and insecticides could allow such compounds to contaminate the near-
<br />surface environment and ultimately the groundwater. Prolonged exposure to these compounds could
<br />detrimentally affect groundwater fauna. The effects of such exposure on people are not sufficiently
<br />understood or adequately studied (Foster, 2007).
<br />In addition, studies have found reductions in groundwater quality as a result of the land application of
<br />treated municipal wastewater. For instance, Katz et al. found evidence of increased nitrate -N, boron,
<br />and chloride concentrations in an effluent spray field reservoir and nearby monitoring wells associated
<br />with a karstic spring basin in northern Florida. The pharmaceutical anti - convulsive drug,
<br />carbamazepine, was also detected in groundwater from the monitoring wells (Katz, Griffin, Davis,
<br />2009).
<br />Another study conducted by Drewes et al. examined the effects of two wastewater treatment facilities'
<br />use of surface spreading basins to use reuse water, or effluent, as a means to stimulate groundwater
<br />recharge in the southwestern United States. One facility sat atop an upper alluvial unconfined aquifer,
<br />primarily composed of silt and gravel sands, a middle confined alluvial unit of clay, mudstone, and silt;
<br />and a lower confined aquifer unit primarily of gravel. The other site, however, sat over recent
<br />alluvium consisting of gravel, sand, and silt. Regardless of each locations' subsurface differences,
<br />systematic analysis of groundwater from down gradient monitoring wells near both sites detected
<br />concentrations of the pharmaceutical compounds carbamazepine and primidine, anit- convulsive drugs,
<br />and thus revealed that not all compounds remaining in treated effluent were removed from the
<br />environment during ground water recharge events ( Drewes et al., 2003).
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