About the author: Calvin Patterson, Ph.D., P.E., is a consulting engineer. Patterson can be reached at 512.343.7375 or by e-mail at [email protected].
Robert P. Callegari, P.E., is principal with CMA Eng., Inc. Callegari can be reached at 512.894.3230 or by e-mail at [email protected].
Calvin Patterson & Robert P. Callegari
undefinedRelated search terms from www.waterinfolink.com: MBRs, reuse, surface water
In 2005, Belterra, Texas, a residential development in Hays County, southwest of Austin, applied to the Texas Commission on Environmental Quality (TCEQ) for a surface water discharge permit. Hays County Water Control & Improvement District No. 1 provides water and wastewater service to the development and is responsible for the permitting. The point of discharge is in the Barton Springs segment of the Edwards Aquifer. Barton Springs provides year-round recreational swimming in the heart of Austin and is home to the endangered Barton Springs Salamander.
Obtaining the discharge permit was a process that put development interests in Hays County against environmental interests in the region. Entities in opposition include Austin, Hays County, the Barton Springs Edwards Aquifer Conservation District, Hays Trinity Groundwater Conservation District, Lower Colorado River Authority (LCRA), Save Our Springs Alliance and Bear Creek Home Owners Association.
Planning for Growth
Belterra began development in 2001, and the district retained CMA Eng., Dripping Springs, Texas, to provide engineering services, wastewater permitting and facility design. CMA applied for and received a TCEQ permit for wastewater facilities that included a conventional activated sludge treatment plant and a 35-acre subsurface drip irrigation system for effluent disposal.
This permit was for 150,000 gal per day (gpd) and was intended to serve the early phases of the development. Further, the initial permit would allow the district to determine whether subsurface drip irrigation was a workable alternative for wastewater disposal for full buildout (approximately 2,400 living unit equivalents).
As the population of Belterra continued to grow, it became clear that additional wastewater treatment capacity would be needed and that drip irrigation could not reasonably satisfy the needs. Planning began to increase the capacity of the treatment plants to 500,000 gpd, with an intermittent discharge of 350,000 gpd into Bear Creek. Meetings were held with the TCEQ permitting team to discuss probable effluent standards. The phosphorous limit is a major issue in permitting.
Permitting Objections
The district’s counsel, Barrett & Smith, Austin, Texas, and its engineer both counseled that given the size of the development, it would be in the district’s interest to look at alternatives such as increasing the subsurface drip application rate or direct discharge with a combined beneficial reuse option. The district’s goal was to reuse the treated effluent on the development’s open space and then have the option to discharge directly into the creek when reuse is not possible (wet periods, frozen ground, etc.). This was a creative and novel approach in this area of Texas.
When TCEQ judges an application to be administratively complete, adjacent landowners are notified and the notice is published in local newspapers. As the notices were received, the opposition filed protest letters demanding that TCEQ not issue the permit and if necessary, be restrained from issuing the permit. The protestors retained lawyers, scientists and engineers to bolster their case. Their protests cited decisions on similar matters and invoked the usual calamitous scenarios of algae blooms and the dangers associated with wastewaters contaminated by pharmaceuticals and personal care products.
One landowner’s property, close to Belterra, included a pond in Bear Creek that provided contact recreation and fishing opportunities. Further downstream, concerns over the Barton Springs Salamander and the water quality in Barton Springs Pool were raised by the protestors. Records from a U.S. Geological Survey gauging station at the discharge of Barton Springs measured the minimum flow as 9 million gal per day (mgd). The average flow is more than 30 mgd, and the maximum recorded flow is 85 mgd.
The district’s counsel, litigators, engineer and other retained scientists and engineers prepared for legal proceedings and to counter protestor claims. The technical team consisted of groundwater and surface water hydrologists, a stream modeler and treatment process and design engineers.
The Mediation Process
The probable effluent standards and capacity of the plant strongly indicated that the emerging technology of MBRs would be the best treatment process for the proposed treatment plant. Enhanced biological phosphorous removal (EBPR) would be employed in the plant to control total phosphorus (TP).
A letter was sent to TCEQ requesting a TP limit of 0.5 mg/L. A draft permit was issued by TCEQ in April 2007, with the following limits on the daily concentration of:
- Carbonaceous BOD: 5 mg/L
- TSS: 5 mg/L
- Ammonia: 2 mg/L
- TP: 0.15 mg/L
Belterra requested that the permit application be sent to the State Office of Administrative Hearings (SOAH). SOAH steps in when there is sufficient public protest of a state agency’s proposed action to essentially take the direct responsibility for decision making out of the hands of the agency. The operating rules of SOAH are similar to those of a law court. There are two administrative law judges. If negotiations fail to resolve the issues, SOAH will conduct an evidentiary hearing.
All the members of the opposing technical teams submitted direct testimony in the form of a written report on their expertise and analysis of the issues. There are depositions of all persons to be witnesses and/or offer direct testimony. Discovery is involved, in which all relevant documents assembled by witnesses are copied and made available to the opposition.
Mediation negotiations between the opposing sides began in June 2008. An evidentiary hearing was scheduled for July. The hearing would be canceled if the negotiations were successful. The negotiations did not resolve all of the issues; however, a consent agreement was reached between the applicants and some of the opposition protestors.
The evidentiary hearing took place during the week of July 13, 2008. About 30 people participated in and observed the proceedings for five days.
In the aftermath of the hearing, both administrative law judges recommended to the TCEQ commissioners that the permit be issued. The commissioners agreed to issue the permit with the proviso that the entire consent agreement be incorporated into the permit.
Final Agreement & Outcome
The agreement included the following 10 points:
- A wastewater treatment plant with MBR technology;
- Total nitrogen in the effluent limited to 6 mg/L;
- The applicant will continue to dispose of 150,000 gpd via drip irrigation;
- The applicant will apply for a Chapter 201 Beneficial Use Authorization to irrigate 201 acres in Belterra;
- The applicant shall construct 5,250,000 gal of effluent holding ponds;
- The daily discharge shall not exceed 350,000 gpd, limited to times when the irrigated acreage is saturated and the holding pond is full and/or Bear Creek is flowing at or above 14 cu ft per second;
- The treatment system be limited to Belterra;
- Class A operator;
- An exhaustive stream survey conducted for 12 months prior to any discharge and 18 months thereafter; and
- The applicant shall use ultra violet light for disinfection of the treated effluent.
Both parties agreed to the first item in the consent agreement, which makes MBRs an absolute necessity in Hays County. Proposals for supplying the membrane equipment were accepted from three bidders in 2009. The winning proposal of $1,425,000 is roughly equal to Belterra’s legal and administrative cost of obtaining the permit.
The water quality downstream of Belterra is protected in full measure by the most stringent surface water discharge permit limits in Texas. The permit ensures beneficial reuse and water conservation in Belterra.
