Cosumnes power plant (01-afc-19) data response, set 1A
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APPLICANT’S CLARIFICATION TO BACKGROUND STATEMENTThis Background section of the Data Requests incorrectly characterizes the effect of SMUD’s use of water for the CPP on the CVP. It is true that “water that is not used by SMUD is made available for other Central Valley Project (CVP) uses.” However, as a practical matter, water not used by SMUD is made available only for irrigation uses. While USBR has obligations to make water available for fish and wildlife and refuge and wetland uses, these obligations are co-extensive with USBR’s obligation to make water available to SMUD. As such, the amount of water made available for these uses is determined by the hydrology of the water year, and not by SMUD’s usage of water under its contract. In other words, these uses receive water whether or not SMUD takes its water. The only effect (from SMUD taking its water) is on irrigation uses, and as noted below in the response to the data requests, the effect is so small as to be literally immeasurable. DATA REQUESTS
Response: As stated in our letter filed December 20, 2001, SMUD objects to this Data Request as being burdensome. Yearly water use, based on billing and payments between USBR and SMUD are available for 1973 to 1997 are presented here in graphical format in the attached Figure W&SR-151.
Response: USBR manages its upstream storage in both the American and Sacramento watersheds to meet multiple agreements for minimum flows and water deliveries. As a result of these and other factors (including hydrology) that affect flows in the American River, an assessment of the diversion of an additional 9,000 AF cannot realistically be provided. As noted elsewhere, 9,000 AFY represents much less than one percent of the flows in the American River, and this amount is generally too small to measure, let alone evaluate independently. In addition, as noted above, the only impacts that may occur as a result of this diversion is an unmeasurable effect on irrigation. Minimum stream flows and water for refuges and wetlands are the responsibility of the USBR and are met irrespective of SMUD’s diversion of water. Last, it is worth noting that the vast majority of diversions by SMUD are considered non-consumptive, and are discharged back into water systems which eventually flow to the Delta. Thus, to the extent that any of these flows might have been used for irrigation south of the Delta, or for environmental purposes in the Delta, SMUD’s method of discharge continues to make them available. BACKGROUND Table 2.2-1 shows the average and peak water demand as 8,000 and 12,431 AF/Y, respectively. Chapter 1 defines the maximum rate as 9,000 AF/Y, and Table 7.1-1 shows the 4 peak months to have a demand equivalent to 9,600 AF/Y. Section 2.2.6 indicates that the maximum natural gas requirement is 170,000 MMBtuh (LHV basis) for each gas turbine, which is 100x the heat input of comparable combined cycle turbines. No other mass & heat balance information was provided to show the sink for this large heat input or to provide a basis to better understand water consumption during average and peak conditions. DATA REQUESTS
Response: The maximum natural gas requirement value in AFC Section 2.2.6 is incorrect and should be 1,700 MMBtuh. AFC Table 7.1-1 provides estimates of monthly water use associated with monthly weather conditions. Peak water use could occur in any of the summer months, but would never occur at the same rate in all months. Therefore, the peak summer monthly values in Table 7.1-1 are not representative of winter months. Peak conditions are provided to calculate an instantaneous flow rate for the purpose of equipment sizing. The instantaneous flowrate provided in Table 2.2-1 is not sustained, and occurs only on the hottest days for a few hours. The number of hours of operation, and water use will depend on temporal power demands and to a lesser extent water quality that cannot be predicted with precision. ISO conditions of 61 degrees result in an annual average use of 8,000 AFY. Since this is an average condition, the Applicant developed peak annual water use estimates using conservative operational scenarios that total, on an annual basis, 9,000 AFY. Over the life of the plant, the District would expect an average use of 8,000 AFY. Onsite water storage is used for fire protection and to maintain a 16-hour supply (based on average conditions) in the event that flow is temporarily interrupted. Onsite water supply could also be used to buffer peak demands.
Response: Condenser performance will be measured by monitoring condenser vacuum, LP turbine back pressure and temperature rise across the condenser. AFC Section 2.2.7.4.1 describes the methods used to reduce scale formation, corrosion and biosolids. In addition the cooling tower basin is periodically drained and solids are removed from the basin and disposed by a qualified and licensed waste hauler. The project, as proposed, can cycle cooling water up to 10 times as shown in AFC Table 7.1-3. Actual water cycling will be determined by our NPDES permit conditions. During the detail design phase of the project, the plant’s NPDES discharge requirements will be used to establish the cycling requirements and options for the design of the cooling tower and associated systems. After issuance of the NPDES permit, the cooling tower cycle limiting parameter can be established. Design particulars regarding non-clog fill, side-stream filtering, and/or basin mixers will be reviewed to determine the best system to meet NPDES requirements and provide for efficient plant operation.
Response: The condenser will be cleaned on an as needed basis. Cleaning intervals can range from weekly to annually depending on water quality. Tube cleaning methods include both plastic and metal scrapers and brushes. Scrapers and brushes are forced through the tubes with a combination of plant service water and compressed air. The tubesheet is cleaned using either pressurized plant service water or by hand with a pick or rake. The cleaning water is returned to the cooling tower basin. BACKGROUND Section 7.2 indicates that potable water will pass through an ultra-filter before being stored in a 2,500-gallon bulk tank and then used to replenish a chlorinated 250 gallon pressure tank. A US Filter Water Boy® package plant is said to employ microfiltration and UV disinfection, but it is unclear how this package plant will interface with the ultrafiltration and chlorination system. DATA REQUEST
Response: Below is the potable water system for the CPP. Depending upon the final selection of an Ultra Fine (UF) filter system a potable water packaged system such as the US Filter Water Boy © potable water system may (or may not) be required. There are UF systems that produce permeate which meet all the bacteria and virus removal requirements for the California Department of Health Services drinking water standards and would therefore not require additional treatment. Chlorination dosing would be regulated depending upon the analysis of the UF permeate (or a “Water Boy” system) and the potable water use rate to determine the proper dosage amount for the amount of contact time available.  Potable Water System In order to ensure adequate supply to emergency shower/eye wash stations during a power loss situation, the pressurized water tank will be sized to provide the necessary pressure and flow to the stations at the lowest operating level of the pressurized tank. Final tank volume and flow requirements will be established in the detail design phase of the project to address these issues as they relate to the final plant potable water requirements under all operating modes and conditions. BACKGROUND Table 8.14-3 estimates effluent quality at 10 cycles of concentration and shows that silica, iron, copper, lead, manganese, mercury, silver, selenium, zinc, and other constituents could exceed the estimated effluent discharge limits. Temperature, trihalomethanes, chlorine, and biocide toxicity are other discharge concerns. Section 7.1.5 describes the blowdown treatment as a clarifier where some of the metals are removed, with a final gravity sand separator used to reduce turbidity to less than 1 NTU before discharge. In similar applications, achieving low metals and turbidity has required different unit processes. DATA REQUESTS
Response: After the NPDES limits have been established, the requirement for additional treatment of clarifier effluent can be reviewed. If it is established that additional reduction in NTU is required, then a sand filter is one of the optional methods available to achieve additional NTU reduction in clarifier effluent.
Response: Clay Creek is a relatively shallow stream with a broad surface area. As a result, the temperature in the stream is primarily a function of air temperature. The stream is cold during winter and hot during summer. Absent any controls, effluent in Clay Creek is estimated to equilibrate according to air and ground temperatures within approximately a mile. Substantial flow from the RSP discharge would also equilibrate instream temperatures. As noted in Section 8.14.3.1 of the AFC, Clay Creek is an ephemeral stream. Natural flows occur primarily as a result of winter rainfall events from November through March. As a result, mixing zones, diffusers and in-stream dilution are not likely to be permitted by RWQCB. The RWQCB currently requires that discharges meet a temperature of + 5 degrees compared to ambient conditions when flow is present. SMUD believes the notched weir design will provide the necessary temperature and water quality benefits, and therefore is not seeking more effective cooling designs.
Response: SMUD generally relied on data available from EBMUD to determine that water quality was suitable for this use. The min/ave/max values as available are provided in Attachment W&SR-159. In addition to these data, SMUD collected an additional grab sample that is reported in Table 7.1-2 of the AFC. These are the best data available to our knowledge. The amount of algae detected in FSC water is not sufficient to cause impacts to the proposed plant. Were algae to become a problem, there are adequate technologies for screening algae from entering the plant.
Response: The numerical criteria listed in Table 8.14-3 were extracted from (RWQCB, 2000) referenced in Chapter 8.14. This source describes for each constituent whether the criterion is for total or dissolved, which is equivalent for all practical purposes to “soluble.” Generally criteria for metals are enforced by the dissolved fraction, but for practical purposes dischargers generally report “total.” The sampling data in Table 8.14-3 are “total” concentrations. If the CPP can meet all discharge requirements without active treatment such as chemical treatments or filtration, it will do so. At present, it appears that water quality is good enough to allow use without additional treatments. However if it is determined that additional treatment is necessary, it would be evaluated and implemented when required. An example would be arsenic removal through adsorption to ferric sulfate, leaving a solid residue that can be disposed in municipal landfill. However, no additional treatments are considered necessary at this time, based on water quality data presented here.
Response: Each of these technologies could be implemented in the event that discharge criteria could not be met by reducing cooling cycles. However, there is a cost in efficiency, heat, and increased waste generation to each of these technologies that is opposite to the goals of SMUD in producing clean, reliable power at the least cost to the district ratepayers. Because these alternatives are not necessary, nor do current data indicate they will become necessary over the life of the plant, and because they do not meet the District objectives for efficiency, they were not further evaluated.
Response: SMUD does not know if and to what extent these streams may contribute to impairment of the San Joaquin River at Antioch for the listed constituents. However, the approximate flow of the Delta near Antioch is approximately 130,000 cfs. The outflow from CPP would be approximately 4 cfs (1,638 gpm * 2.228 x 10 –3 = 3.7 cfs). or 0.003% of the Delta outflow. Aldrin, heptachlor, hexachlorcyclohexane, toxaphene, chlorpyrifos, dieldrin, heptachlor epoxide, DDT, diazinon, endrin, chlordane and endosulfan are pesticides that are thought to originate primarily from agricultural practices which are not anticipated on the CPP site. Low dissolved oxygen is not a likely result of CPP as the water is cascaded through a cooling tower prior to discharge and therefore highly aerated. No organic materials would be introduced by the process, and the water originates from a generally low-organic source (American River). Therefore, organic enrichment is not anticipated. Mercury primarily comes from natural outcrops of cinnabar and inactive mines or mine tailings, which are not part of the anticipated uses of the CPP site. Electrical conductivity is a measure of dissolved ions in water, including salt. All waters contain some dissolved ions, so the named creeks probably do contain these materials, but the San Joaquin River at Antioch is heavily influenced by agricultural tailwater flows from the San Joaquin. CPP is reducing the impacts of electrical conductivity by monitoring and controlling the quality of its discharge through a stringent RWQCB permit. The additional flows in Clay Creek and the Cosumnes River from the CPP may have beneficial impacts for the aquatic life of these rivers.
Response: Final engineering design for this project has not been completed. However, it would be typical to monitor electrical conductivity using continuous monitoring devices to track electrical conductivity in the cooling tower, and adjust blowdown according to the quantity of solids implied by the conductivity. Chlorine residual is generally monitored with continuous monitoring devices linked in-line with the discharge. Chlorine is generally controlled by injecting bisulfite or SO2 to dechlorinate prior to discharge. Trihalomethanes are produced in trace amounts when waters high in humic acids (organic substances) are heavily chlorinated. Trihalomethanes have been identified as at least a theoretical concern in proposals to chlorinate waters drawn from the Delta that are high in suspended peat and other organic substances. The proposed water supply is very low in organic substrate and is unlikely to produce measureable trihalomethanes. The RWQCB as part of its NPDES permit generally requires at least annual monitoring and reporting for a long list of California Toxics Rule and National Toxics Rule-listed chemicals, including trihalomethanes. SMUD anticipates this will apply to CPP also. BACKGROUND Recent RWQCB meetings with the applicant have shown that effluent discharge criteria will likely be more stringent than assumed in the AFC. Data Requests
Response: SMUD believes Table 8.14-3 reflects the most recent estimate of effluent criteria. It is important to recognize that authority to implement effluent criteria is the responsibility and authority of the RWQCB and EPA. SMUD has used current guidance from the RWQCB and recent NPDES permits to estimate these values, but the RWQCB could apply higher or lower concentration limits than those listed. With respect to inconsistencies, CEC staff has incorrectly attempted to directly link data from two different tables in Section 7 and Section 8.14. The purposes and uses of each table are different although the water quality data used to derive this information is the same. Table 7.1-1 represents combined data from EBMUD and a grab sample collected from Folsom South Canal. These data are estimates of the water quality in Folsom South Canal. Table 8.14-3 presents these same water quality data, and the estimated effluent criteria that would be applied by the RWQCB. CPP estimates that the towers would operate between 3 and 10 cycles of concentration, with the highest concentration.
Response: Cooling tower treatment chemicals are generally long-chain polymers that contain no heavy metals or substances that would be toxic to aquatic organisms. Two frequently used vendors are Betz and Nalco. Several Nalco products are listed in the AFC in Table 8.12-2. Toxicity thresholds are reported to be very high by these companies. The intended use if for water that will be discharged, and therefore, they are required to be non-toxic. Effluent and monitoring requirements are the responsibility and authority of the RWQCB, who determine required tests after evaluating the potential for toxicity and adverse effects to beneficial uses. No permit has been issued at this time, and the Applicant is not the appropriate party to advise CEC on why certain tests are included. The RWQCB generally requires 3-species acute or chronic toxicity testing as part of an NPDES permit. |