TO: ARTHUR TALLEY, WALT SEARS, GEORGE WARD, 0258 FILE
FROM: PAUL PRICE
RE: TASK 15: TECHNICAL SUPPORT FOR PREPARATION OF IMPLEMENTATION PLANS
This memorandum is intended to provide technical support to the TCEQ in the development of an implementation plan for controlling pollution sources in the Lake O' the Pines watershed to achieve the water quality endpoint during the TMDL project. Here we focus on the three primary aspects of Implementation Planning set forth in Task 15; evaluation of alternative management scenarios, development of monitoring strategies and schedules, and identification of parties responsible for implementing management practices.
1) Assist TCEQ in making evaluations of the effectiveness of alternative regulatory and non-regulatory management scenarios.
The Lake O' the Pines TMDL project has shown annual loads of total phosphorus and total nitrogen to average 142,877 and 533,000 kg, respectively. Phosphorus control provides the better opportunity for controlling plant growth, as nitrogen is present in excess quantities relative to the growth demands of algal populations, and is much more difficult to control due to its relatively greater mobility as a result of metabolic transformations.
While the largest volume discharges are for industrial cooling water, those generally have limited effects on water quality, and little or no effect on Lake O' the Pines as they are discharged into tributary reservoirs specifically constructed for that purpose (i.e., Johnson Creek, Ellison Creek, Welsh, and Monticello Reservoirs). The remaining discharges are primarily effluents from municipal or domestic wastewater treatment plants, and most are small (<0.2 MGD). The largest permitted dischargers in the Lake O' the Pines watershed, by far, are located in Mount Pleasant, with the Southwest Plant, which receives effluent from the Pilgrims' Pride Corporation poultry processing and rendering plant discharging nutrient loads an order of magnitude greater than all the others combined.
Big Cypress Creek was shown to carry most of the nutrient load entering Lake O' the Pines, and to be the source of nutrients resulting in adverse water quality conditions in the upper portion of the reservoir. Of the total loading, point sources account for about 21% of the phosphorus load entering Lake O' the Pines from Big Cypress Creek, or 29,877 kg/year. The data for nitrogen is somewhat more difficult to interpret. While the annual point source nitrogen load of 336,000 kg is only about 16% of the monitored load at Station 10308, it is 63% of the load monitored at Station 13631, which represents the load entering Lake O' the Pines. While we may safely assume that all of the phosphorus discharged into the Big Cypress Creek drainage will eventually enter Lake O' the Pines, the same cannot be assumed for nitrogen, particularly during baseflow conditions when the point source loads experience maximum travel times to Lake O' the Pines. The very large (91%) average loss rate of nitrogen between Stations 10308 and 13631 is not expected to hold for non point source inputs as travel times are much shorter for runoff events, at least the larger ones, and dissolved oxygen conditions at the sediment-water interface are less likely to favor denitrification.
During much of the data collection period for the TMDL project, the Mount Pleasant Southwest Plant has been operating without nutrient limits, since permit renewal for this plant has been pending since 1995. That draft permit contains a nitrogen limitation of 15 mg/l (daily average), as opposed to the 73 mg/l daily average recorded during the August, 1998 intensive survey. Pilgrims' Pride Corporation is constructing a new processing plant near Pittsburg that will inject some of its treated, recycled effluent into a deep well, and will discharge some to Big Cypress Creek through Walker Creek. Concomitantly, Pilgrims' Pride Corporation plans to abandon a major portion of the capacity of the Mount Pleasant Southwest Plant that they currently use, freeing that capacity for domestic wastewater from the City of Mount Pleasant. The net effect of those changes should be a reduction in phosphorus loading to Big Cypress Creek of 50%, and of nitrogen loading by 90%.
In order to adequately monitor point source nutrient loading, we recommend that total phosphorus and nitrogen (not just ammonia-nitrogen) limits be imposed on all wastewater dischargers larger than 0.2 MGD, and that their self reporting should include ortho and total phosphorus, nitrite, nitrate, ammonia and TKN. Effluent monitoring should be based on 24-hour composites and monitoring frequencies should be at least once/week for the largest plants.
NON POINT SOURCES
Intensive survey and monitoring results, the results of wet weather sampling, the distribution of litter application areas, and the SWAT modeling all point to the Big Cypress Creek reach between Fort Sherman Dam and Highway 11 receiving most of the nutrient load. Figures 1 and 2 show the the distribution of phosphorus and nitrogen along the length of Big Cypress Creek and Lake O' the Pines during late summer 1998 and 1999. Implementation of best management practices (BMP) at Pilgrims' Pride Corporation operations, and their contract growers, was initiated during the TMDL project. The BMPs include structural and litter management features designed to impede runoff of sediments and dissolved nutrients, and nutrient management planning intended to reduce the amount of nutrients passed through the chicken-litter system. There is some evidence in the monitoring data that nutrient levels (and loadings) in Big Cypress Creek reached a peak in the 1997-2000 period. Use of BMPs in the Lake O' the Pines watershed should be encouraged among independent growers. There is also a need to monitor representative facilities and litter application areas to determine directly the effectiveness of imposed BMPs.
Other activities that may be important to nutrient management are large timber harvest areas and fertilized row crops and pastures. Edge of field studies examining selected activities and environmental conditions will permit evaluation of the magnitude and relative importance of various types of non-point sources and identification of specific major sources of nutrients and oxygen demand from land use data. Edge of field studies to directly evaluate effectiveness of alternative BMP installations under local conditions will be critical to water quality management as long as the poultry production industry continues to produce and apply large quantities of soiled litter in the Lake O' the Pines watershed. Sample sites, with replication, should include common land uses (e.g., pasture, woodland) used for litter application, and those suspected of contributing disproportionate amounts of sediment, nutrient, or oxygen demanding material (CAFOs, timber harvest areas, row crop agriculture).
2) Develop implementation schedules and long-term monitoring strategies:
Our experience in the Cypress Creek Basin has shown that routine monitoring tends to under-sample rainfall-runoff events due to their relative rarity and the generally coarse time resolution of the monitoring schedule, and that wet weather monitoring difficulty and expense tends to be maximized in mid-sized streams due to extreme flow variability relative to channel sizes and access during runoff events. Mainstem stations on Big Cypress Creek (e.g., SH11, US259) offer better access to monitor seasonal variation and long-term water quality trends characteristic of both baseflow conditions and runoff events. Water quality impacts as a result of nutrients and oxygen demand originating from wet weather events are not manifest in Big Cypress Creek and its tributaries, but are realized in Lake O' the Pines during conditions of summer stratification. The results from wet weather (and routine) monitoring concentrated at two mainstem stations will be directly applicable to management of Lake O' the Pines as Big Cypress Creek is the primary source of nutrient and oxygen demand loads to that reservoir.
Point sources in the Lake O' the Pines watershed appear to exert only localized effects as a result of oxygen demand deposition (e.g., Tankersley Creek below the wastewater outfall at FM127). Although some assimilation of the nutrient component of the baseflow load appears to occur during passage down Big Cypress Creek, we believe that essentially all of the phosphorus entering the Big Cypress Creek drainage below Fort Sherman Dam is eventually deposited in Lake O' the Pines. Trends in baseflow water quality can be adequately monitored at two fixed, mainstem stations.
Although NPS pollutants are not confined to particular watersheds in the Cypress Creek Basin, the western watersheds that drain into Big Cypress Creek below Fort Sherman Dam (impounding Lake Bob Sandlin) are the primary sources of nutrients and oxygen demand entering Lake O' the Pines. Continued monitoring of streams draining directly into Lake O' the Pines is not recommended unless there is specific reason to believe that a problem source has been introduced into one of these watersheds.
Monitoring in the main body of Lake O' the Pines should be increased, at least during the critical summer period, while the frequency of sampling in cove stations can be substantially reduced or eliminated given current land use patterns in the Lake O' the Pines watershed. Monitoring stations should be chosen to represent the upper, middle and lower portions of the reservoir. The current upper Lake O' the Pines station (10300, Lone Star Boat Ramp) does not provide a representative sample of water quality conditions in the upper reservoir. It is a narrow segment of the old Big Cypress Creek channel surrounded by extensive wooded wetlands that are major sinks for suspended material entering the reservoir, support large macrophyte populations and shelter the channel from wind stress. The upper reservoir station should occupy a more open location above SH155, such as 16868 or 17087. Installation of permanently emplaced dissolved oxygen/temperature monitors at the dam (10296), the NETMWD intake (10297), and in the upper reservoir, above SH155 (16868), would greatly benefit management efforts.
At a minimum, sufficient data must be obtained to track nutrient loading from Big Cypress Creek, and the nutrient/dissolved oxygen climate during critical periods in Lake O' the Pines. Nutrient discharges from major point sources should be monitored to evaluate the effectiveness of permit limits and more precisely relate point source loading to the loads entering Lake O' the Pines.
For a minimum program, basic parameters to be sampled in streams would be TOC, TP (ND < 0.01 mg/l), NH3, NO2+NO3, TKN, plus field parameters, and discharge. Minimum stream stations to monitor loading, accumulation and loss from the reservoir would be 10308, 13631 and 15135. Reservoir monitoring would follow the selected stream monitoring schedule. The basic parameter set would be collected from TOP AND BOTTOM of the water column, plus chlorophyll a, and pheophytin a. Diurnal dissolved oxygen measurements would be made at each station during the sample period unless permanent dissolved oxygen sensor stations have been established and are functioning properly.
Extend USGS gage 07344500 (BIG CYPRESS CREEK NEAR PITTSBURG, TX) at TCEQ Station 10308 to full range permanently. This gage presently reports only flows above 2,500 cfs, although gage heights are collected and reported. It will cost about $7,000/year to have the gage rating maintained for lower flows. This gage is situated above the flood pool elevation of Lake O' the Pines, so it can produce useful flow information at all times, and is located below the mouths of Tankersley and Walker Creeks (the present and future carriers of Pilgrim's Pride point source effluents), and has the most extensive historical data set in this reach of Big Cypress Creek.
Other gage locations Utilize one of the stream gages obtained for the TMDL program (without the ISCO automated sampler) to record flows at 13631 (or 15257). This gage would only be effective when Lake O' the Pines in near or below conservation elevation, but would provide direct information on hydraulic loading from Big Cypress Creek into the reservoir during that condition.
Initiate nutrient (TP, OP, NH3, NO2+NO3, TKN) sampling consisting of 24-h composites collected weekly at major source locations. Detection limits should be consistent with any permitted nutrient limitation, but in no case be greater than 0.05 mg/l. The major sources are located in Mount Pleasant and Pittsburg. Smaller sources, particularly those discharging to Lake O' the Pines, could be included, but might have less frequent sampling and reporting requirements.
3) Identify parties responsible for implementing management measures.
TCEQ is uniquely qualified to implement management measures on the permitted dischargers through the imposition of nutrient limits and self-reporting requirements. Northeast Texas Municipal Water District, a major regional water supply entity, can provide assistance with monitoring and managing non point sources through its "Joint Agreement" with Pilgrims' Pride Corporation and management of the existing Cypress Creek Basin Clean Rivers Program. Pilgrims' Pride Corporation has made significant commitments in that agreement to accomplish effective management of poultry operations and litter application aimed at ameliorating existing problems and in avoiding future problems due to anticipated growth in the poultry production industry.