Wastewater Discharges to the Barton/Onion Creek Watersheds

Barton Springs/Edwards Aquifer Conservation District

OutlineRecharge of the Edwards Aquifer

Potential Impacts to Groundwater

Supporting Evidence for Discharge Prohibition

Summary

Spring

Contributing Zone Recharge Zone

Artesian Zone

Relatively ImpermeableYounger FormationsEdwards Limestones

Relatively ImpermeableOlder Formations

Artesian Spring Artesian Well

BalconesFault Zone

EdwardsArtesian Aquifer

Typical Cross-Section of the Edwards Aquifer Region

Land Surface

Edwards Aquifer

Graphic courtesy of Gregg A. Eckhardt

Evidence The contributing streams above the recharge zone are no flow or

low flow most of the time thus effluent discharges would dominate recharge most of the time.

Hill country streams are nutrient poor with very low assimilative capacity, sensitive to any nutrient inputs.

Studies confirm degradation (change in trophic status) would occur from a single permitted discharge under some conditions

The BS segment of the aquifer has limited ability to assimilate pollutants.

The BS segment is much smaller in size and by volume than the SA segment offering reduced opportunity for dilution of pollutants

Dye trace studies confirm direct connections of recharge from contributing watersheds to the Aquifer, public supply wells, and Barton Springs

Rapid transport of nutrient enriched recharge water would have undesirable effects on Barton Springs and its endangered species habitat.

Summary All existing developments successfully manage wastewater with

alternative disposal methods (TLAP, 210) Not intended to be an obstacle to development Promotes reuse of water via a properly sited and designed Land

Application System §311 and §213 currently do not provide adequate protection. Should be in §311 to protect both contributing-zone stream quality

and downstream recharge water quality Needed to prevent cumulative impacts in the aquifer from multiple

discharges and to preserve pristine hill country streams Contributing Zone should be treated as an extension of the

Recharge Zone for water quality protection. Needed to preserve recharge water quality, protect public supply

wells, the Barton Springs pool, and the endangered species habitat Supported by the local political jurisdictions over essentially all of

these watersheds (Travis Co., Hays Co., BSEACD, CoA, CoDS, others)