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Home My WebLink AboutNC0069841_Rocky River_Monitoring_Modeling Plan_20220728 Monitoring and Modeling Plan NPDES Permitting Support for the Water and Sewer Authority of Cabarrus County Rocky River, North Carolina Revised July 28, 2022 PREPARED FOR PREPARED BY North Carolina Department of Tetra Tech, Inc. Environmental Quality (DEQ) 4000 Park Drive, Suite 200 Division of Water Resources (DWR) Durham, NC 27703 512 North Salisbury Street P.O. Box 14409 1617 Mail Service Center Durham, NC 27709 Raleigh, NC 27699-1617 Black & Veatch Water and Sewer Authority of 10925 David Taylor Drive, Suite 280 Cabarrus County (WSACC) Charlotte, NC 28262 232 Davidson Highway Concord, NC 28027 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan TABLE OF CONTENTS 1.0 INTRODUCTION...........................................................................................................................................1 2.0 PROJECT GOALS AND OBJECTIVES.......................................................................................................3 3.0 AVAILABLE DATA REVIEW........................................................................................................................5 3.1 WWTP Discharge Data...........................................................................................................................7 3.2 Flow Records and Low-Flow Calculations..............................................................................................8 3.3 Stream Water Quality Data.....................................................................................................................9 3.4 Weather Data....................................................................................................................................... 10 3.5 Existing QUAL2 Models....................................................................................................................... 10 3.6 Exisiting HEC-RAS Models.................................................................................................................. 11 4.0 MODELING APPROACH........................................................................................................................... 13 4.1 Model Description ................................................................................................................................ 13 4.2 Model Development............................................................................................................................. 13 4.3 Model Calibration and Corroboration................................................................................................... 15 4.4 Model Application................................................................................................................................. 15 4.5 Modeling QA/QC Approach ................................................................................................................. 15 5.0 MONITORING APPROACH....................................................................................................................... 16 5.1 Study Objective.................................................................................................................................... 16 5.2 Monitoring Data Collection................................................................................................................... 16 5.3 Monitoring Locations............................................................................................................................ 20 5.4 Pre-Field Study Planning ..................................................................................................................... 23 5.5 Field Deployment Protocols................................................................................................................. 23 5.6 Quality Assurance................................................................................................................................ 24 5.7 Custody Documentation....................................................................................................................... 25 5.8 Health and Safety Plan ........................................................................................................................ 25 5.9 Post-Monitoring Data Management..................................................................................................... 25 6.0 ANTICIPATED DELIVERABLES............................................................................................................... 26 OTETRA TECH ii July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 1.0 INTRODUCTION This Monitoring and Modeling Plan was prepared to support the Water and Sewer Authority of Cabarrus County (WSACC) in seeking approval for the expansion of discharge capacity associated with wastewater treatment plant (WWTP) effluent discharge from the Rocky River Regional WWTP (RRRWWTP) and/or the Muddy Creek WWTP (MCWWTP). These two WWTPs are owned and operated by WSACC and are permitted under the National Pollutant Discharge Elimination System (NPDES) as ID NCO036269 (RRRWWTP) and NCO081621 (MCWWTP). These facilities are permitted to discharge a mix of treated domestic and industrial wastewater with maximum flow rates of 26.5 million gallons per day (MGD) for RRRWWTP and 0.3 MGD for MCWWTP into the Rocky River. WSACC seeks overall treatment capacity expansion, although the precise numeric increase will be determined later in summer 2022 as part of a larger Master Planning effort for WSACC by Black&Veatch. The environmental modeling and monitoring assessment described in this plan is required to inform speculative limits for a wasteload allocation (WLA)that is protective of receiving water quality of the Rocky River. The Rocky River is approximately 95 miles long and is a major tributary to the Pee Dee River. The Rocky River flows generally southeast from Iredell County, along the northernmost border of Mecklenburg and Cabarrus Counties, through Cabarrus County, and forms the county line between Stanly, Union, and Anson Counties, with additional headwater drainage area in Rowan County. The Rocky River watershed (hydrologic unit code 03040105) includes impaired streams which appear on the most recent version of the North Carolina 303(d) list (2022 draft list), largely for degradation of the aquatic life beneficial use. The Rocky River mainstem is impaired due to turbidity and benthos, with some areas impaired for copper and zinc. Turbidity impairments are identified based on observed water quality of>50 Nephelometric Turbidity Units (NTU), and benthos impairment is a narrative criterion based on protecting aquatic life in freshwater streams. Most direct tributaries to the Rocky River are impaired for benthos. Other impairments in various tributaries include the following: turbidity, dissolved oxygen, fish, pH, and heavy metals. The Rocky River is home to expanding urban environments and like all waterways, has limited capacity to assimilate waste streams from various dischargers. The Rocky River watershed is home to some 8 major WWTPs and 45 minor WWTPs which discharge effluent to local waterways with varying levels of treatment. The watershed is also home to at least one endangered species, the Carolina Heelsplitter mussel which can be found in the Goose Creek tributary. There are four interbasin transfer(IBT)certificates regulated within the watershed, where water is withdrawn from adjacent major basins and discharged into the Rocky River basin, with the following maximum daily allowances: 1. Charlotte Water(formerly Charlotte-Mecklenburg Utility Department): 33 MGD from the Catawba River 2. Union County and Town of Wingate: 23 MGD from the Yadkin River 3. Concord/Kannapolis: 10 MGD from the Catawba River 4. Concord/Kannapolis: 10 MGD from the Yadkin River There are some additional smaller and grandfathered IBTs in the watershed (e.g., Union County draws five (5) MGD from the Catawba River, Concord/Kannapolis draws six (6) MGD from Second Creek in the South Yadkin River Basin). Major urban area extents, key WWTPs, county boundaries, and primary waterways are shown in Figure 1. Note that the RRRWWTP, Muddy Creek WWTP, and West Stanly WWTPs discharge from outfalls directly to the mainstem of the Rocky River, while the Mooresville WWTP discharges to Dye Creek, and all other facilities discharge to nearby tributaries which drain to the Rocky River. Generally speaking, smaller municipal facilities are not critical to simulation of DO and nutrient conditions instream, however at DWR request, the inclusion of the Norwood WWTP will be incorporated in the modeling of Rocky River as a direct discharger to the mainstem. aTETRA TECH 1 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan Mooresville 4hr - WWTP ' � Rowan Davidson � County County a d Montgomery o A x Cabarrus ,' County County Rocky River Regional WWTP 0 Long Creek Mallard Creek , i WWTP otanly County Mallard Creek West Stanly WWTP WWTP `.� Muddy Creek WWTP Jlecklenburg �� Rocky River 1 County GreeK 0 Ked Crooked Creek ►� G(00 e� to 1 WWTP #2 atayooc j /Norwood WWTP Union Coll Legend j Anson Key WWTPs Monroe County WWTP River/Stream Watershed Lanes creek, County Line 5- NORTH CAROLINA Urban Area - ' SOUTH CAROLINA Rocky River Key WWTP Facilities N o 325 65 13 Kilometers O TETRA TECH Map produced by H.Yonce,7-26-2022 0 325 6.5 13 Miles WGS_1984_Web_Mercator_Auxiliary_Sphere Figure 1. Location of the WSACC and other key WWTP NPDES facilities in the Rocky River watershed aTETRA TECH 2 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 2.0 PROJECT GOALS AND OBJECTIVES A line of communication was opened between WSACC and the North Carolina Division of Water Resources (DWR)via consultants Black &Veatch and Tetra Tech on January 11, 2022, on the topic of modeling requirements and expectations of DWR for potential permit expansion for WSACC facilities in the Rocky River watershed. In a memorandum prepared by the DWR Modeling and Assessment Branch provided on January 18, 2022, DWR identified explicit criteria to meet and consider for NPDES expansion projects along the Rocky River. These requirements were established to ensure new and expanding WWTPs in the basin are assessing the systemwide impact of their combined discharges on the Rocky River. For the proposed WSACC capacity expansion to the Rocky River, model evaluations may consider flows beyond current limits for major municipal WWTPs planning on expanding. There is a substantial history of QUAL model development in the watershed in support of various WWTP permit expansions which is expanded upon in Section 3.0. However, these modeling applications are built upon datasets that are too old to be reliable without sufficient field verification and additional robust monitoring. It is important that evaluation of NPDES expansions continue to be based on the full spatial domain of the Rocky River mainstem because rapid regional growth and the combined impact of multiple permitted discharges must be assessed in tandem. Existing and historic models of the Rocky River mainstem and its tributaries will be leveraged to the extent possible in model development for this new application, but it will be robust new datasets to be collected in 2022 that will form the foundation of the model dataset, particularly for model calibration. As requested by DWR, monitoring will occur at multiple points along the Rocky River mainstem full extent, and water quality monitoring will be conducted as close to 7Q10 conditions as it becomes available during the summer and fall of 2022. Proper simulation of the mainstem will be paired with up-to-date simulation of both tributaries and point sources based on recent and new datasets. DWR also requested that a detailed analysis of available data be prepared as part of this monitoring and modeling plan. The modeling analysis with QUAL2K will allow DWR, WSACC, and Black &Veatch to comprehensively determine the environmental impacts of the proposed permitted effluent discharge expansion on the Rocky River. The overall project goal is to develop speculative limits (i.e., a potential updated WLA)for the RRRWWTP and/or MCWWTP that protects the designated uses of Rocky River under the proposed net increase in waste flow discharge. It is important for DWR that the modeling results provide assurance that the expanded facility speculative effluent limits result in the attainment of water quality standards when considered in tandem with other potential future impacts related to expanding permitted dischargers throughout the Rocky River basin. To meet this project goal, a modeling framework was developed based on the project objective to simulate impacts of the expanded discharge capacity from WSACC on dissolved oxygen (DO)dynamics of Rocky River to support speculative limits. This Monitoring and Modeling Plan was developed with the aid of a field reconnaissance trip conducted on April 11 — 12, 2022 during which Tetra Tech field teams visited every road crossing of the Rocky River and near the mouths of major tributaries to assess opportunities for site access, channel substrate, and visualization of flow conditions (Figure 2). aTETRA TECH 3 July 28, 2022 Scoping W tl a, : e op laser r gefind ng f' tip ` ' i ra n �ieEce:i .. 'kr Locating appropriate channel Measuring water depth and access at road crossing = -identifying substrate t Identifying potential site Georeferencing candidate sites -impacts-due to construction for future field sampling WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 3.0 AVAILABLE DATA REVIEW The Rocky River watershed has many existing datasets and historical hydrology and hydraulic (H&H) modeling applications that can be leveraged in constructing the monitoring and modeling plan for the proposed WSACC expansion. Existing monitoring data, sources, models, and available data across the watershed are summarized in Table 1 and detailed in the following subsections. The most significant data gap present with existing datasets and modeling applications is the lack of spatially comprehensive, robust datasets representative of recent conditions. Tetra Tech intends to address this data gap by performing intensive field monitoring during summer and potentially the early fall of 2022 if needed as detailed further in Section 4.0. Key existing monitoring sites from the United States Geological Survey (USGS) and the Yadkin Pee Dee River Basin Association (YPDRBA) across the watershed are shown in Figure 3. Table 1. Available data, sources, and descriptions of Rocky River watershed datasets Data Source • • WWTP EPA ICIS Publicly available Discharge Monitoring Report (DMR) records for all major Discharge ECHO and NPDES dischargers in the watershed for consideration and incorporation Data WSACC into the model as available through the Environmental Protection Agency's Integrated Compliance Information System web platform Enforcement and Compliance History Online. Additional information about WWTP discharge which may be monitored but not required for reporting in DMRs will be obtained directly from WSACC for their RRRWWTP and MCWWTP facilities. Flow Records USGS USGS surface water monitoring sites across the watershed with several and Low-Flow sites on the mainstem and many tributaries. Coordination with Curtis Weaver Calculations on updated and historic low-flow statistics for streams within the model extent. Stream Water Various Water quality sampling data at various locations around the area as Quality Data available through the National Water Quality Monitoring Council "Water Quality Portal". Records available online include sampling sites from the STORET and NWIS databases which include data from USGS, YPDRBA, and the various NC DEQ DWR current and historical sampling efforts and associations (e.g., Ambient Monitoring System (AMS), Monitoring Coalition Program, and Water Quality Exchange (WQX)). Weather Data Various Meteorological data are readily available in both gridded formats (e.g., North American Land Data Assimilation System Version 2 [NLDAS-2]), and at individual local weather stations across the watershed, particularly at major and regional airports. Existing NC DWR NC DWR provided the most recent QUAL models which were most recently QUAL2 applied during the Charlotte Water expansion of Mallard Creek WWTP. Models Tetra Tech Tetra Tech developed the existing QUAL model for Crooked Creek which will be incorporated to the extent possible in this modeling effort. Existing HEC- NC FRIS NC Flood Risk Information System (FRIS) maintains publicly available HEC RAS Models models with surveyed and composite channel and floodplain cross-sections. aTETRA TECH 5 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan Mooresville Q7330000 Mallard Creek WWTP WWTP 02124080 / Q7700000 0212419274 Q8200000 Q7780000 Rocky River Regional WWTP 0212433550 J m Q8210000 JJJ Q8220000 c+ oar m Q x %� Long Creek WWTP �o ; West Stanly I WWTP Mall rd Creek Q8720000 0212393300 Q91200 0 0212414900 Norwood Q7450000 WWTP 02124269 0212427947 Q7600000 ock ver 0212430293 GreeK 0212430653 GOO Kea 02126000 0212466000 Gtee Q8480000 Q8342000 gas Q8355000 0212467451 era < Q8360000 Muddy Creek WWTP Q8385000 Q8374000 Legend Q8388000 Key WWTP Q8917000 Q WQ Site 0212467595 Q9021300 Q8820000 USGS Site Q8386200 Lanes ( Monroe WWTP River/Stream Q8800000 Watershed Q8386000 Crooked Creek WWTP#2 Rocky River Existing Monitoring v 0 325 65 13 Kilometers O TETRA TECH Map produced by H.Yonce,7-26-2022 0 325 65 13 Miles WG S_1984_Web_Mercator_Aux i liary_S ph a re Figure 3. Existing key flow and water quality monitoring sites in the Rocky River watershed aTETRA TECH 6 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 3.1 WWTP DISCHARGE DATA The NPDES-permitted dischargers of interest for this project are significant municipal WWTPs which discharge directly to or near the Rocky River mainstem or several key tributaries (Table 2). DMR datasets from the EPA can be used to parameterize point source WWTP discharges. DMR records include permitted parameter results which vary by parameter and frequency for each permittee. Data gaps for parameters required for QUAL2K modeling not available from DMRs will be obtained via direct request from dischargers, via grab sample and field probe observations during intensive summer monitoring, or based on accepted literature references. Key WWTPs have relevant wasteflow limits for flow, DO, ammonia (NH3), and either five-day biochemical oxygen demand (BODs) or carbonaceous BOD (CBOD5). All facilities are required to monitor total nitrogen and total phosphorus with the exception of MCWWTP. Additional parameters of interest which are monitored or permitted (or both) include parameters such as total suspended solids, water temperature, pH, and hardness. Table 2. Discharge monitoring report(DMR) data for key municipal NPDES permittees in the Rocky River watershed I Significant Permit Limits (Flow in MGD, all else in mg/L) Facility Owner NPDES ID Receiving Facility Permit Monthly Daily Water Type Year Mean Mean Flow ®®®® D• Rocky River Town of NCO046728 Dye Creek Grade IV 2019 7.5 5.0 10.0 1.0 2.0 6.0 WWTP Mooresville Rocky River WSACC NCO036269 Rocky Grade IV 2021 34.0 10.0 20.0 1.6 3.5 6.0 Regional WWTP' River (CBOD5) (CBOD5) Muddy Creek WSACC NCO081621 Rocky Grade II 20 WWTP 2 River (202121) 0.3 (1.0) ( ) ( ) ( )10.0 5.0 20.0 10.0 4.0 (1.0) 8.0 2.0 5.0 Mallard Creek City of NC0030210 Mallard Grade IV 2019 16.0 4.2 8.3 1.0 2.0 6.0 WRF ' Charlotte Creek (CBOD5) (CBOD5) Monroe WWTP City of NCO024333 Richardson Grade IV 2020 12.5 5.0 10.0 1.0 2.0 5.0 Monroe Creek Crooked Creek#2 Union Crooked 2018 WWTP 2 County NC0069841 Creek Grade III (2021) 1.9(8.2) 5.0 (5.0) 10.0 (5.0) 2.0 (1.0) 4.0 (1.9) 6.0 (6.0) West Stanly Stanly NCO043532 Rocky Grade III 2018 1.2 (2.5) 9.0 (5.0) 18.0 (5.0) 3.0 (1.8) 6.0 (1.8) 5.0 (5.0) WWTP 2 County River (2020) Long Creek City of NCO024244 Long Creek Grade IV 2018 16.0 10.0 20.0 1.1 2.4 5.0 WWTP Albemarle Norwood WWTP Town of Norwood NCO021628 Rocky River Grade III 2018 0.75 30.0 (annual) No limit No limit No limit WWTP has a permit limit for CBOD5 as a substitute for BOD5 as permitted by EPA to provide more complete picture of oxygen-demanding substances. 2 WWTP has submitted a proposed capacity increase,with speculative limits shown in parentheses. For Crooked Creek#2 WWTP, a new discharge location with expanded capacity and name change (Lower Crooked Creek Water Reclamation Facility)while absorbing capacity from Grassy Branch WWTP(NC0085812). NTETRA TECH 7 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 3.2 FLOW RECORDS AND LOW-FLOW CALCULATIONS There are numerous active USGS flow gages in the Rocky River watershed that can be used for monitoring flow conditions before field work, to parameterize flow conditions around monitoring events and develop reasonable critical low flow statistics (Table 3). There are two gages active on the mainstem, with 11 other gages throughout the watershed on various tributaries. To establish model parameterization for seasonal critical low flow conditions, a line of communication has been initiated with Curtis Weaver of the USGS and Klaus Albertin of NC DWR via the DWR web portal for low flow requests and subsequent emails. Curtis Weaver has authored several low flow studies on the Rocky River watershed and statewide (Weaver and Fine, 2012 3, Weaver, 2016 4). As recommended by Curtis Weaver, low flow statistics for the Rocky River and its tributaries will be estimated as a function of updated statistics associated with the two mainstem USGS gages, and relative changes between those values and the most recent developed from the USGS reports for the watershed will be used to scale low flow calculations across the watershed. Changes in low flow statistics as provided by Curtis Weaver will represent provisional updates at one or two anchor points. Table 3. Active USGS gages across Rocky River watershed Gage Name Drainage Flow Data Period RecordM, Area (Mi2) of 0212393300 West Branch Rocky River below mouth of South Prong River 20.8 2004-Present near Cornelius, NC 02124080 Clarke Creek near Harrisburg, NC 21.9 2003-Present 0212414900 Mallard Creek below Stony Creek near Harrisburg, NC 34.6 1994-Present 02124269 Back Creek at SR1173 near Harrisburg, NC 7.45 2009-Present 0212433550 Rocky River above Irish Buffalo Creek near Rocky River, NC 278 2000-Present 0212466000 Clear Creek at SR3181 near Mint Hill, NC 12.6 2002-Present 0212467595 Goose Creek at SR1525 near Indian Trail, NC 11.0 2002-Present 0212467451 Goose Creek at SR1524 near Indian Trail, NC 8.5 2009-Present 02126000 Rocky River near Norwood, NC 1,380 1986-Present 0212430653 McKee Creek at SR2804 near Wilgrove, NC 5.76 2007-Present 0212430293 Reedy Creek below 1-485 near Pine Ridge, NC 12.6 2007-Present 0212427947 Reedy Creek at SR2803 near Charlotte, NC 2.5 2001-Present 0212419274 Coddle Creek at SR1612 near Davidson, NC 22.7 2002-Present 3 Weaver, J.C., and Fine, J.M., 2003, Low-flow characteristics and profiles for the Rocky River in the Yadkin-Pee Dee River basin, North Carolina, through 2002: U.S. Geological Survey Water-Resources Investigations Report 03-4147,47 p. 4 Weaver, J.C., 2016 (revised). Low-flow characteristics and flow-duration statistics for selected USGS continuous-record stream gaging stations in North Carolina through 2012 (ver. 1.1, March 2016): U.S. Geological Survey Scientific Investigations Report 2015-5001, 89 p., http://dx.doi.org/l0.3133/sir20155001. OTETRA TECH 8 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 3.3 STREAM WATER QUALITY DATA Water quality data throughout the Rocky River watershed are available through the Water Quality Portal (WQP), a product of the USGS and EPA. The WQP houses all available water data for the eight-digit hydrologic unit code (HUC8) 03040105 for the Rocky River watershed. Data sources include NWIS (USGS), STEWARDS (ARS), and WQX (EPA). The period of record for data within the HUC8 includes some 286,247 sample results from approximately 352 sites via NWIS and STORET, from 1955 through 2020. Surface water data most relevant to the proposed Rocky River modeling include some 47 various parameter types including various nitrogen and phosphorus species, dissolved oxygen, conductivity, alkalinity, hardness, pH, water temperature, and algae concentrations. Key water quality sampling in the region is conducted by the Ambient Monitoring System (AMS) and regionally by the YPDRBA (Table 4). Table 4. Active Ambient Monitoring System and YPDRBA sampling sites across the Rocky River watershed PeriodStation ID Station Name . Record Q8342000 Clear Creek at US601 near Brief Road i 1998-Present Q7700000 Coddle Creek at SR1304 (Roberta Road) near Roberta Mill 2003-Present Q8200000 Cold Water Creek at SR1132 (Miami Church Road) near Concord 1998-Present Q8388000 Crooked Creek at NC218 near Fairview Crossroads 1998-Present Q8360000 Goose Creek at SR1524 (Stevens Mill Road) near Mint Hill 1998-Present Q8374000 tse Creek at SR1547 near Brief Rd 2007-Present Q8090000 Irish Buffalo Creek at SR1132 near Faggarts 1970s-Present Q9021300 Lanes Creek at SR1005 (Landsford Road) near Marshville 1998-Present Q8720000 Long Creek at SR1917 near Rocky River Springs 1970s-Present Q8386200 North Fork Crooked Creek at SR1514 (Rocky River Road) near Monroe 1998-Present Q8386000 North Fork Crooked Creek at SR1520 (Indian Trail-Fairview Road) near Monroe 1998-Present Q8820000 Richardson Creek at SR1006 (Olie Branch Road) near Monroe 1998-Present Q8800000 Richardson Creek at SR1751 (Walkup Avenue) at Monroe 1998-Present Q8917000 Richardson Creek at SR1649 near Fairfield 1980s-Present Q8480000 Rocky River at NC 205 near Stanfield 2013-Present Q8355000 Rocky River at SR1114 (Garmon Mill Road) near Midland 1998-Present Q7780000 Rocky River at SR1132 (Flowes Store Road) near Harrisburg 1998-Present Q7600000 Rocky River at SR1304 (Roberta Road) near Harrisburg 1998-Present Q8385000 Rocky River at SR1606 (Sykes Mill Road) near Fairview Crossroads 1998-Present Q7330000 Rocky River at SR2420 (East Rocky River Road) near Davidson 1998-Present Q7450000 Rocky River at US29 near Harrisburg 1998-Present Q8210000 Rocky River at US601 near Concord 1998-Present Q8220000 Rocky River at SR1006 (Mt Pleasant Road) near Concord 2005-Present Q9120000 Rocky River at SR1935 near Norwood 1970s-Present OTETRA TECH 9 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 3.4 WEATHER DATA Meteorological data is available through nationwide gridded formats such as NLDAS-2, as well as individual local weather stations across the watershed. Model input hourly parameters include hourly air and dew point temperatures, cloud cover, and wind speed. Which data sources that will be applied to the modeling environment will be selected after review and analysis relative to observed field conditions. NLDAS-2 provides continuous hourly gridded meteorological data from 1979 to present with 1/8-degree resolution. NLDAS-2 provides air temperature, specific humidity, surface pressure, solar radiation, and wind speed at 10 meters. Variables provided by NLDAS-2 can be used to calculate dew point temperature. Local meteorological stations can also be used to parameterize air and dew point temperatures, wind speed, and cloud cover. Datasets can be pulled through online resources such as Weather Underground at locations throughout the region or sites available through the National Climatic Data Center(NCDC) and the State Climate Office of North Carolina which can be accessed via the National Weather Service (NWS) and/or the National Oceanic Atmospheric Administration (NOAA). Local Climatological Data sites via NOAA include five sites surrounding the Rocky River watershed area: Concord Regional Airport, Charlotte Douglas International Airport, Monroe Regional Airport, Anson County Airport, and Stanly County Airport. There is also one monitoring site available through the NC Environment and Climate Observing Network (ECONet) in the watershed in Stanly County (NEWL-New London, NC). 3.5 EXISTING QUAL2 MODELS The mainstem Rocky River has been simulated with receiving water models since at least the 1980s. In 1988 and 1992 small-scale QUAL2E-UNCAS platform models were developed separately in support of WWTP permit limit expansions for the Mooresville WWTP (now Rocky River WWTP discharging to Dye Creek), the Mallard Creek WWTP (operated by the former Charlotte-Mecklenburg Utility District, now Charlotte Water), and the Rocky River Regional WWTP operated by WSACC. In 1993, a QUAL2E-UNCAS model was developed for the upper Rocky River and Mallard Creek, simulating 47.6 miles in support of the Mallard Creek WWTP discharge expansion from 3 to 6 MGD. This effort involved integrating the three existing model extents, and application scenarios based on critical low flow conditions. Simulation of model inputs such as oxygen demanding substances were based on best available information for parameters such as SOD, CBOD, etc. In 2001, an additional QUAL2E model was developed for the lower Rocky River mainstem, with simulation extent extending some 31 miles downstream of the existing QUAL2E model from above the Muddy Creek WWTP to the USGS gage at Norwood. This new QUAL2E model did not change parameterization of the upstream 1993 QUAL2E model but provided new simulation with recent observations to the new lower Rocky River simulation extent. CBOD decay rates were improved based on new observed water quality data, and time of travel (TOT) studies were conducted under mid-flow conditions (458-504 cfs at the USGS Norwood gage) in March 2000 and low-flow conditions in May 2000 for the entire new lower Rocky River model extent with rhodamine dye to provide robust simulation of instream velocities. From 2018 to 2021, the combined lower and upper QUAL2E model was transformed and updated to the newer more robust QUAL2K model in support of a high permitted discharge limit for the Mallard Creek WWTP (now Water Reclamation Facility or WRF)from 12 to 14.9 to 16 MGD. Critical low flow conditions were simulated seasonally for summer and winter, while additional model updates included refined nitrification rates and other kinetics, improved reaeration simulation with the Churchill formula, single pool CBOD simulation (fast CBOD), etc. Tetra Tech developed a QUAL2K model for Crooked Creek in recent years in support of speculative expansion limits for a modified Crooked Creek WWTP#2 and/or Grassy Branch WWTP both for Union County. Monitoring and modeling results associated with that project will be incorporated and linked to this updated Rocky River. aTETRA TECH 10 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan Existing QUAL models across the watershed provide insight and a baseline on which future monitoring and modeling may be built upon to both help close data gaps, decrease uncertainty, and refine temporal and spatial resolution of the simulations. 3.6 EXISITING HEC-RAS MODELS There are six Hydrologic Engineering Center River Analysis System (HEC-RAS) one-dimensional flood models publicly available through the North Carolina Flood Risk Information System (FRIS) program covering the mainstem Rocky River. Publicly available engineering models for the mainstem together cover the entire mainstem spatial extent (Figure 4). All of these models are detailed studies with the exception of the Rocky River model along the Mecklenburg/Cabarrus County boundary which is a limited detail study. The available models are listed below from headwaters to confluence with the Pee Dee River: • Rocky River(detailed study) in Iredell County, approximately 8 miles from eastern Mooresville to the Iredell/Mecklenburg County boundary • Rocky River(limited detail study) along the Mecklenburg/Cabarrus County boundary from the Iredell/Mecklenburg County boundary approximately 5 miles to the West Branch Rocky River confluence • Rocky River(detailed study) across Cabarrus County from confluence of the West Branch Rocky River for approximately 50 miles to the Stanley/Cabarrus County boundary • Rocky River(detailed study)along the Stanly/Cabarrus County boundary to the Union/Stanly/Cabarrus County boundary, approximately 4 miles • Rocky River(detailed study)from the Union/Stanly/Cabarrus County boundary approximately 22 miles along the Union/Stanly County boundary to the Union/Stanly/Anson County boundary. • Rocky River(detailed study)from the Union/Stanly/Anson County boundary to the confluence with the Pee Dee River, approximately 27 miles There are additional HEC-RAS models available across the Rocky River watershed, however, those of primary interest are those for simulated receiving waters. This will likely include Mallard Creek and Long Creek, for which there are several additional HEC models available: • Long Creek (limited detail study) approximately 8 miles of the headwaters in Stanly County near the Cabarrus/Stanly County boundary • Long Creek (detailed study) approximately 8 miles from the upper model downstream extent to Long Creek WWTP in Albemarle • Long Creek (limited detail study) approximately 13 miles from the Long Creek WWTP to the confluence with the Rocky River. • Mallard Creek (detailed study) approximately 12 miles in Mecklenburg County from the headwaters north of Charlotte to the Cabarrus County line • Mallard Creek (detailed study) approximately 3 miles in Cabarrus County from the Mecklenburg County line to the confluence with the Rocky River HEC-RAS models can be utilized for developing rating curve formulas for channel hydraulics in QUAL2K based both on field-measured and simulated cross-sections from the HEC-RAS platform. aTETRA TECH 11 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan Iredell County Rowan County Davidson County 1 Cabarrus County o, Stanly Mallard Creek County Montgomery County Mecklenburg Rocky River County Union County Anson County Legend HEC-RAS Models Mallard:Cabarrus RR: Cabarrus/Stanly River/Stream Long Creek:IDS Mallard: Mecklenburg RR:Iredell County Watershed Long Creek:Middle RR:Anson/Stanly RR: Mecklenburg/Cab... RR:Cabarrus County Long Creek:US � RR:Union/Stanly Rocky River Existing HEC Models N o 325 6.5 13 Kilometers O TETRA TECH Map produced by H.Yonce,4-26-2022 0 3.25 6.5 13 Mlles WGS_1984_Web_Mercator_Auxiliary_Sphere Figure 4. Existing HEC-RAS model spatial extents on the Rocky River, Long Creek, and Mallard Creek aTETRA TECH 12 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 4.0 MODELING APPROACH To answer the study question of whether the Rocky River has capacity to assimilate an increased effluent discharge from WSACC, the quasi-steady state receiving water model QUAL2K is proposed for application. The QUAL2K model is a useful tool to answer the specific elements of the NPDES permitting impact analysis, particularly related to dissolved oxygen kinetics. The proposed modeling framework consists of the application of the QUAL2K receiving water modeling platform chosen specifically based on its capabilities and efficiency to answer the project objective from a scientifically backed regulatory standpoint. 4.1 MODEL DESCRIPTION QUAL2K 5 is a quasi-steady state water quality model that is an updated version of USEPA's QUAL2E model, the "Enhanced Stream Water Quality Model", employed for conventional pollutant simulation in streams and rivers. QUAL2K can be used to study the impacts of waste loads on water quality and allows the user to simulate a suite of physical and chemical conditions including model segmentation, various forms of carbonaceous BOD, particulate organic matter simulation, anoxia and denitrification modeling, sediment-water DO and nutrient fluxes, explicit simulation of attached bottom algae, and light and heat inputs and daily cycling. QUAL2K offers comprehensive hydraulic functions, diel heat budget and thermal dynamics, and dynamic water quality kinetics and is often applied for the evaluation of nutrient control strategies, such as water temperature and DO total maximum daily load (TMDL) analyses. The empirical equations in QUAL2K for DO simulation can predict the Streeter-Phelps DO sag curve downstream of effluent outfalls as the balance between oxygen-demanding and oxygen-producing substances interact kinetically. The types of oxygen-demanding and producing parameters simulated within QUAL2K include biotic photosynthesis and respiration, denitrification, decay of CBOD, SOD, and physical properties of the waterbody related to reaeration. 4.2 MODEL DEVELOPMENT A QUAL2K model will be developed for the entire mainstem of the Rocky River and along significant portions of Mallard Creek and Long Creek (Figure 5). The spatial extent of the model will be comprehensive to capture the DO sag point downstream of the major NPDES dischargers that occur in response to the loads of nutrients and oxygen-demanding substances present in the effluent. A separate QUAL2K model recently developed for Crooked Creek is available now for Union County, and the City of Monroe is planning to develop a QUAL2K model for Richardson Creek. Therefore, expansion of Union County and Monroe effluents can be linked to the proposed new modeling framework being developed for WSACC. Key model inputs for the proposed new QUAL2K project include channel hydraulic geometry, meteorological conditions, boundary inflows for headwaters, tributaries, diffuse flows, and point sources. Significant existing data sources, historical QUAL models, and a substantial summer 2022 monitoring effort will provide enough information to develop, calibrate, and corroborate a robust QUAL2K model for the Rocky River. The following WWTPs will be simulated explicitly based on the combined impacts directly on simulated waterways: • Town of Mooresville: Rocky River WWTP (NC0046728) discharging to Dye Creek • WSACC: RRRWWTP (NC0081621) and Muddy Creek WWTP (NC0036269) discharging to Rocky River • Town of NorwoodL Norwood WWTP (NC0021628) discharge to Rocky River • Charlotte Water: Mallard Creek WRF (NC0030210) discharging to Mallard Creek • City of Albemarle: Long Creek WWTP (NC0024244) discharging to Long Creek • Stanly County: West Stanly WWTP (NC0043532) discharging to Rocky River 5 Chapra, S.C., Pelletier, G.J.,Tao, H.2012. QUAL2K:A Modeling Framework for Simulating River and Stream Water Quality, Version 2.12: Documentation and User's Manual. Civil and Environmental Engineering Dept., Tufts University, Medford, MA. aTETRA TECH 13 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan Mooresville WWTP Rocky River Regional WWTP +_ v o4io 1 Q a n m A creel, Long Creek Mallard WWTP e West Stanly WWTP Mallard Creek WWTP t Rocky River Muddy Creek WWTP k Ked Gree Gr°° e* Gta o� ay at Crooked Creek WWTP#2 Legend 1 Proposed Monroe WWTP Model Extent Lanes Creek River/Stream Watershed Rocky River Proposed Model Extent N o 325 135 13 Kilometers O TETRA TECH Map produced by H.Yonce,4-26-2022 0 325 65 13 Miles WGS_1984_Web_Me rcator_Auxi liary_Sph a re Figure 5. Proposed spatial extent of the Rocky River QUAL2K model and significant WWTP facilities aTETRA TECH 14 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 4.3 MODEL CALIBRATION AND CORROBORATION After initial QUAL2K model setup and parameterization based on the best available information including direct monitoring data and literature information, various model inputs may be adjusted within acceptable limits (i.e., calibrated) and based on sound scientific rationale until the resulting predictions provide good correlation with observed data. Model corroboration is the subsequent process of testing the calibrated model to ensure that it is acceptable for application to new NPDES discharge scenarios. In the corroboration process, the calibrated model is run with input from a separate monitoring event for comparison with observed values for key model output parameters. Model corroboration is the task of determining whether the developed model accurately represents the real system under a different suite of conditions while maintaining model parameterization from calibration. 4.4 MODEL APPLICATION Following model calibration and corroboration, QUAL2K will be used to conduct a fate and transport analysis for the Rocky River by simulating instream response to speculative permit limits from expanded WSACC effluent discharge, particularly related to nutrient and DO concentrations. This application will be conducted under seasonally low-flow(i.e., summer and winter lowest seven-day average flow that occurs once every ten years [7Q10]) and elevated temperature conditions, considering the combined impacts of all key NPDES dischargers at existing and potential future maximum allowable permit limits. This model application will be used to develop speculative limits for WSACC that maintain numeric water quality criteria in the Rocky River. Results will be presented for both existing and proposed permit limits associated with all major WWTPs in the watershed to determine the relative impacts of the expansion on the entire mainstem. It is unlikely or very infrequent that these critical conditions co-occur and due to this margin of safety it can be assumed that water quality achieved will be better under more typical conditions. Tetra Tech will deliver all final model files and report describing the fate and transport analysis to WSACC, Black &Veatch, and DWR for review and approval. 4.5 MODELING QA/QC APPROACH Tetra Tech will perform QA/QC checks throughout the modeling process, including the following procedures: 1. Effective data organization. This task will involve acquiring the data needed to set up the QUAL2K model and archiving all data and recording all data sources. 2. Data transformation. This task is key in the model setup. After acquiring and archiving original data, data will be transformed or processed for model setup. QA checks will be performed on the effluent and ambient characteristics. Checks will be performed to ensure the reasonability and accuracy of the inputs. 3. Tracking data transformations.A data tracking sheet will be used for these modeling analyses. The sheet will be updated throughout the modeling process. The sheet will contain information on the source of data for modeling inputs, how the data was manipulated and transformed, and the location of the final data sets. This will provide documentation throughout the entire modeling process that can be provided to clients or other modelers who assist on the project. Following completion of modeling, the tracking sheet will be reviewed by a reviewer not directly involved in the modeling project if time and resources allow. 4. Model review. Information on data assumptions, model set-up, calibration parameters, and calibration results at the completion of major calibration benchmarks will be discussed internally with input from senior modelers. aTETRA TECH 15 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 5.0 MONITORING APPROACH This monitoring plan was developed to help ensure that the Rocky River QUAL2K model is set up, calibrated, corroborated, and applied in a way that is representative of the sampled environment and scientifically defensible to answer the study questions. While available data described in Section 3.0 have been sufficient to support model development for previous applications in the watershed, significant additional data collection is required to support the development of an updated model, with associated calibration and corroboration. This section describes the objective and strategy for the extensive field monitoring proposed to support the model update. Project complexity for the approach to field monitoring is based on the scale of the work which includes 95 miles of mainstem Rocky River with additional locations on tributaries, particularly Mallard Creek and Long Creek. The vast monitoring extent will require time to conduct field observations, collect and analyze water chemistry samples, and conduct studies related to TOT, SOD, and reaeration rates. To the extent possible, the most comprehensive water chemistry sampling events to be conducted in support of model calibration and corroboration will occur at least one month apart in time to reflect separate and substantially different steady state low flow conditions to support corroborating the model under conditions not identical to the data used for model calibration. 5.1 STUDY OBJECTIVE The primary study objective associated with the proposed monitoring approach is to collect robust hydraulic and water quality field data to support updated QUAL2K model development, calibration, and corroboration. The monitoring data is the foundation on which the model is built and will be conducted in a manner that is both reasonable to the financial constraints of WSACC in seeking permit expansion and scientifically rigorous to meet the expectations of DWR to feel confident in the results for NPDES limit decision making. 5.2 MONITORING DATA COLLECTION To establish a robust dataset for QUAL2K model development, calibration, and corroboration, the following monitoring will be conducted, targeted to be accomplished from May—October 2022: 1. Cross-Section Surveys Channel cross-sectional surveys will be conducted at up to 50 locations (mostly along the mainstem Rocky River) to enhance resolution of existing survey datasets for development of model reach hydraulic formulae (Figure 6). Cross-sectional measurements will include a suite of physical measurements which may vary between sites, including photography, channel width, water depth, channel shape, bed composition, and flow velocity measurements. Flow measurements will be conducted with a high-precision SonTek FlowTracker 2 handheld Acoustic Doppler Velocimeter(ADV) mounted to a top-set wading rod. These observations will be conducted throughout summer 2022 under a variety of flow conditions on the mainstem and tributaries. ,i c l: • + _��7Yc+'� r v'' "4!.�4 Figure 6. Channel cross-section setup with long retractable measuring tape aTETRA TECH 16 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 2. Reaeration Studies Channel reaeration will be measured using diffusion dome deployment at approximately six locations along the Rocky River mainstem where adequate conditions for observations can be found for ease of access, adequate flow volume, and appropriate water depth for instrumentation (Figure 7). Effort will be made to conduct reaeration measurements with spatial distribution throughout the Rocky River mainstem. These observations will ideally be conducted under steady state low flow conditions. 1' Figure 7. Image of floating dome apparatus showing nitrogen purge, vent, ambient DO probe, and pump to circulate water over the dome to control dome temperature to measure reaeration 3. Sediment Oxygen Demand Studies In-situ SOD chambers to measure both water column oxygen demand and SOD will be deployed at up to six locations where adequate conditions for observations can be found for ease of access, adequate substrate, and appropriate water depth for instrumentation (Figure 8). Chamber incubation periods are run to detect a stable oxygen depletion rate, typically for several hours. Effort will be made to conduct SOD chamber measurements with spatial distribution throughout the Rocky River mainstem. These observations will ideally be conducted under steady state low flow conditions. uo (are"l ron 1a.wr.tor�w aco. r �".- S1moa+ T.ew tye-> Npp�.(us Para d.dw ( E : n.eo(OV OC 1EOp..) .�.. air con(e y. (X7 4'1 W.IINMMI 44—V(I.p 2e-v+Io.p a-•yr.!� , I dlrnWr ever ''�� u.!aq b,PLAIAW AIM CM) rr19. j ev""ID69 O.WI 'Uft. T W M) 2e pu aq OL909 WV u99wuo C".62 1 X...pm..V N O bl.0 roan!: ID.21'(0,cm) M:9 V2"(24 1<n) Ca.n'(77*cm1. - -'3/4" Y Y.•' GtWlp - c2@.Gcw4r ` 1 N.cwcvQ�•) 6.L6lI.r. ''.�Y, Figure 8. Schematic of SOD chamber(left), photo of SOD chamber(top right), typical deployment (bottom right) NTETRA TECH 17 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 4. Time of Travel Studies Understanding flow velocity dynamics throughout the entire Rocky River mainstem will be improved through conducting TOT studies with inert Rhodamine WT (water tracer) dye (Figure 9). Continuously monitoring fluorometers (Cyclops-7F Submersible Sensors by Turner Designs) will be placed throughout the mainstem downstream of various locations where dye slugs will be injected to capture the TOT and stream flow velocity across stream reaches. Fluorometers will be secured in PVC housing fixed to the channel bed with rebar and/or cinderblock housing as detailed in the Physical Water Parameter Observations section below. The dye studies conducted in March and May 2000 were under mid-flow and low-flow conditions, therefore we will endeavor to perform TOT studies under various mid and low flow steady state conditions as the summer of 2022 allows. Dye studies will be conducted at different times across the watershed to capture as much of the mainstem as possible to support establishing flow-velocity relationships, leveraging existing studies to the extent possible. Coordination with various local emergency management and response entities will occur to ensure the general public and officials understand the nature of the monitoring work and that the bright red, fluorescent dye may be visible during that period. Figure 9. Example of inert fluorescent pink Rhodamine WT dye deployment 5. Physical Water Parameter Observations Physical parameters to be measured throughout the study area and continuously by sonde at multiple sites include water temperature, DO, pH, and conductivity. These measurements will occur in the field using a handheld probe (YSI ProQuatro Portable Multiparameter Water Quality Meter)whenever other sampling is being undertaken at a wide variety of locations and times over summer 2022. Sonde (YSI EXO Multiparameter Water Quality Sonde) deployment will occur at spatially discrete locations to measure continuous trends in physical water parameters at key locations during two key monitoring efforts when generating robust datasets for model calibration and corroboration, ideally under low-flow conditions (Figure 10). Figure 10. Constructed secure housing for a continuously logging sonde (bottom left)and instream deployment of continuously logging sonde (right) TETRA TECH 18 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 6. Water Chemistry Sampling Grab samples for water chemistry will be conducted twice daily during two large sampling efforts to collect data in support of model calibration and corroboration, ideally under low-flow conditions. Thirty sites will be sampled, including six (6)WWTP effluent sites, eleven (11) mainstem Rocky River sites, and thirteen (13)sites on major tributaries (see Section 5.3). The fifteen (15)water quality constituents to be monitored at many sites include nutrient species, BOD parameters, and various other parameters (Table 5, Figure 11). Table 5. Water quality sampling parameters, methodologies, and reporting limits' MethodParameter Reporting Limit(mg/L) BOD 5-day SM 5210B 2.0 CBOD 5-day SM 5210B 2.0 BOD 20-day SM 5210C 2.0 CBOD 20-day SM 5210C 2.0 Total Dissolved Solids SM2540C 10 Total Suspended Solids SM 2540D 2.5 Ammonia Nitrogen EPA 350.1 0.1 Total Kjeldahl Nitrogen EPA 351.2 0.2 Nitrate/Nitrite Nitrogen EPA 353.2 0.10 Total Phosphorus EPA 200.8 2 0.020 Orthophosphate SM 4500P E 0.020 Hardness SM 2340C 1 Total Organic Carbon SM 5310C 1 Turbidity EPA 180.1 1.0 NTU Chlorophyll-a EPA 445 0.001 'Practical quantification limit(PQL)will be the same for these parameters unless sample requires dilution during analysis 2 Method selected due to available laboratory equipment, results not for regulatory purposes. r Figure 11. Example of collection of water quality grab samples in sample bottles aTETRA TECH 19 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 5.3 MONITORING LOCATIONS The various monitoring data parameters will be collected at a suite of strategic sites along the Rocky River mainstem and its immediate vicinity to ensure development of a robust dataset with reasonable spatial resolution. Proposed monitoring sites for the various data types were established based on the historical field and modeling data available, and field reconnaissance efforts conducted April 11 — 12, 2022. In addition to these planned discrete sampling locations for twice-daily water quality grab sampling during two intensive field studies for calibration and corroboration data, cross-sections and synoptic data of physical water parameters will be collected systemwide during the entire summer. The scope of the project includes plans to conduct water chemistry sampling at thirty (30)total locations twice daily under two different flow conditions. Sites will include eleven (11) mainstem locations, thirteen (13)tributary locations, and six (6)treated effluent discharges from key WWTPs (Table 6, Figure 12). Sites where YPDRBA or the NC Ambient Monitoring System have conducted long-term sampling will be prioritized due to historical data for comparison and known access points at road crossings. Sites for sonde deployment will be prioritized where equipment can be anchored with rebar to the channel bed in relatively low-traffic areas to avoid theft or vandalism. Where anchoring to the substrate using rebar is not possible due to hard substrate, sondes may be attached to anchors and placed underwater before securing to a stationary object with a cable. SOD study sites require sufficient bed sediment in which observation equipment can be embedded in the channel. Reaeration studies require sufficient water depth to float diffusion chambers in representative areas throughout the watershed. As the Rocky River channel has increasingly rocky bed sediment moving downstream, it may be possible that the number of SOD sites may be transitioned to more readily available reaeration sites given specific site conditions, however, both measurements can be highly valuable in parameterizing the dissolve oxygen cycling instream. The final list of sites identified for water chemistry grab sampling, sonde deployment, TOT analyses, SOD measurements, and reaeration studies are subject to change based on additional field reconnaissance conducted during the summer, avoidance of potential field obstacles such as active construction, confirming suitable bed sediment and water depth where necessary, and with the expert opinions of Gantzer Water for specifically suitable SOD and reaeration study sites. During reconnaissance, it was observed that road crossings of the Rocky River at NC-205 and US-52 were undergoing active construction in the waterway with noted flow diversions; that activity will be tracked throughout the summer. Where possible, water chemistry sampling may be conducted from bridge crossings over waterways. The precise locations of where the TOT studies will be conducted with discharge of Rhodamine dye slugs and deployment of fluorometers will be determined based on field observations and comparison to existing dye studies. Dye studies can be quite costly, therefore strategic decisions will be made to cross-check existing conditions in summer 2022 to previous studies conducted in the lower Rocky River from Garmon Mill Road above the Muddy Creek WWTP to Plank Road (location of USGS gage 02126000) during 2000. If the velocities captured in 2000 can be field-verified, dye studies may be strategically conducted in the vicinity of the RRRWWTP, the upper Rocky River, or potentially along Long and/or Mallard Creeks. Table 6. Proposed monitoring sites identified by data collection type # Type Site ID Location Note E 0 1 WWTP WWTP-Moores Mooresville WWTP Discharges to Dye X 2 WWTP WWTP-RRR Rocky River Regional WWTP Near 0212433550 X 3 WWTP WWTP-Muddy Muddy Creek WWTP X 4 WWTP WWTP-Mallard Mallard Creek WWTP Discharges to Mallard X aTETRA TECH 20 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan Site ID Location • 5 WWTP WWTP-WS Stanly WWTP Discharges to Rocky River X 6 WWTP WWTP-LC Long Creek WWTP Discharge to Long Creek X 7 Mainstem RR-Johnson Rocky River at Johnson Dairy Upstream of Dye Creek X Rd (SR-1142) 8 Mainstem RR-Davidson Rocky River at Davidson Rd Q7330000 X (SR-2420) 9 Mainstem RR-US29 Rocky River at US-29 Q7450000 X X X X 10 Mainstem RR-Flowes Rocky River at Flowes Store Q7780000 X X X X Rd (SR-1132) 11 Mainstem RR-US601 Rocky River at US-601 Q8210000 X X X 12 Mainstem RR-MtPleasant Rocky River at Mt Pleasant Rd Q8220000 X (SR-1006) Rocky River at Garmon Mill Q8355000, 13 Mainstem RR-Garmon Rd (SR-1114) 1999 SOD site,2001 TOT study X X I 14 Mainstem RR-Sikes Rocky River at Sikes Mill Rd TOT study(2001) X (SR-1606) 15 Mainstem RR-NC205 Rocky River at NC-205 Q8480000,2001 TOT study X X X 16 Mainstem RR-Plank Rocky River at Plank Rd (SR- 02126000,2001 TOT study X X 1621) 17 Mainstem RR-US52 Rocky River at US-52 1999 SOD site 2 X X X 18 Tributary Long-Kingsley Long Creek at Kingsley Rd Upstream of Long Creek WWTP X 19 Tributary Long-NC138 Long Creek at NC-138 Near Q8720000 X X X 20 TributaryMallard- Mallard Creek at Morehead Rd Q7570000 X X Morehead 21 Tributary Mallard-Pavilion Mallard Creek at Pavilion Blvd Q7550000, 0212414900 X X 22 Tributary Dye-Johnson Dye Creek at Johnson Dairy Downstream of Mooresville X Rd WWTP 23 Tributary Irish-RRRWWTP Irish Buffalo Creek via X easement 24 Tributary Dutch-NC200 Dutch Buffalo at NC-200 X 25 Tributary Lanes-Randall Lanes Creek at Randall Rd X 26 Tributary Richardson- Richardson Creek at Rocky X Rocky Mount Church Rd 27 Tributary Goose-Brief Goose Creek at Brief Rd X 28 Tributary Crooked-Brief Crooked Creek at Brief Rd X 29 Tributary Coddle-NC49 Coddle Creek at NC-49 Q7700000 X 30 Tributary Reedy-LRR Reedy Creek at Lower Rocky X River Rd OTETRA TECH 21 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan WWTP-Moores RR-US29 Dye-Johnson Coddle-NC49 RR-Johnson Reedy-LRR RR-Davidson RR-Flowes WWTP-RRR Irish-RRRWWTP RR-US601 RR-MtPleasant Dutch-NC200 f � � RR-Riverbend 0 WWTP-Muddy n x Long-Kingsley `D 1 WWTP-LC Mahard Creek � - 1 WWTP-WS Long-NC138 'Mallard-Morehead 'WWTP-Mallard Rocky River ti 'Mallard-Pavilion A�° dc�e r G °Ke Legend RR-US52 Proposed Y ti°ra�a � � � RR-Plank O Monitoring Sites Lanes-Randall Proposed _ Richardson-Rocky Model Extent s�r RR-NC205 River/Stream RR-Sikes Crooked-Brief Watershed Goose-Brief lanes Creek Rocky River Proposed Monitoring N o 325 e5 13 Kdomn te,s a TETRA TECH Map produced by H.Yonce,7-27-2022 o 325 6 s 13 hides WGS 1984_Web_Mercator Auxiliary_Sphere Figure 12. Proposed primary monitoring sites to support the updated Rocky River QUAL2K model OTETRA TECH 22 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 5.4 PRE-FIELD STUDY PLANNING Upon acceptance of this Monitoring and Modeling Plan by DWR, a study plan will be finalized to coordinate logistics and methodologies to be used for the intensive field sampling effort. The study plan will include the following: • Equipment procurement, including chest waders, possibly a canoe, field logbooks, sampling collection and storage equipment, GPS Unit, extra batteries for GPS unit and other equipment, camera, site map, first aid kit, and other needed items • Arrangements with NCDEQ-certified laboratories for water quality analyses. Due to the number of sampling sites and parameters requiring analysis simultaneously, multiple labs will be utilized to ensure adequate storage and processing space. • Field sampling methodology plan based on requirements specified for the analytical methods • Advance notification of appropriate contacts before planned fieldwork events (e.g., local emergency management services prior to dye studies, regional DEQ office) • Checking the weather to ensure safe and reasonable conditions for the sampling event day • Reviewing nearby USGS flow gages to determine targeted sample collection times and dates based on observed flow conditions. The sampling team will coordinate with regional WWTP staff as needed when access in or around the treatment facility is required, as well as coordination for grab sampling of treated effluent. 5.5 FIELD DEPLOYMENT PROTOCOLS Water quality sampling will be conducted on two separate days approximately one or two months apart to provide appropriate datasets for conducting QUAL2K model calibration and corroboration. The two sampling events are targeted to be performed sometime between June 1 and October 31, 2022. Two sets of samples (morning and afternoon)will be collected for each of the sampling events. Sampling will be dependent on weather and flow conditions. Precipitation and flow will be monitored online at nearby gages to ensure that there is no appreciable precipitation seven days prior to sampling and longer if gages indicate that runoff has not receded to approximately baseflow (steady state) levels. Field sampling teams and laboratory services will be on-call for these periods and sampling go/no-go decisions will be made approximately 72 hours before scheduled deployment. WSACC project contacts will be notified of sampling "go" decisions to be aware that the sampling teams will be in the field. Field sampling will be conducted by at least two groups of at least two personnel. The field persons will be responsible for collecting, documenting, and properly storing samples. Sampling techniques will be conducted using approved methodologies endorsed by NCDEQ for surface waters. Detection limits and quantification levels need to be appropriate for the applicable North Carolina surface water quality standards. The associated Standard Operating Procedures (SOPs) are to be followed. Samples must be collected with new, verified, and certified-clean equipment. Filtering and/or acid preservation using clean hands and equipment will be conducted onsite as required by the analytical method. One or more waterproof field logbooks must be maintained for recording data collection activities performed during the study. The general principle of information recording is that all entries be sufficient to reconstruct the site investigation without reliance on memory. All field measurements from samples collected will be recorded. Wherever a sample is collected, at a minimum, the following will be recorded: • Sample collection location (narrative description, coordinates) • Field observations (weather conditions, treefalls) • Date and time • Sampling challenges or quality assurance issues • Sampling team member names aTETRA TECH 23 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan To ensure consistency, a standardized form will be developed by the monitoring team prior to the sampling effort and applied throughout the project duration. Each section of the form will be completed with an ink pen. Any information not applicable to a certain site will be flagged as "NA". Additionally, digital photographs documenting the sampling locations (i.e., showing the orientation to the surrounding area and nearby objects) should be taken and included in the documentation. Each photograph documentation in the logbook should include the assigned photograph number, field date, and subject. Physical parameters (water temperature, pH, DO, conductivity, and turbidity)will be measured in the field using a handheld sonde throughout the Rocky River model extent while other sampling and measurements are conducted. Additionally, sondes will be deployed at various locations throughout the model extent measuring continuous physical parameters, approximately one foot below the water surface for the duration of each major sampling event for the calibration and corroboration datasets. Grab sampling of water quality constituents at the thirty (30) identified key locations will be conducted twice per day (morning and afternoon) during the two intensive field monitoring periods. Sampling conducted at WWTP facilities will be conducted by WWTP staff at prescribed times and locations in the treated effluent pipeline. 5.6 QUALITY ASSURANCE The Tetra Tech Water Division maintains scientifically sound and reputable practices for QA/QC. Tetra Tech provides QA for its clients using a QC system of reviews developed and implemented to produce measurements and deliverables of required quality. Examples include independent checks of calculations, proofreading and technical editing, instrument calibrations, and independent checks of data entries. QA is an integrated system of management procedures and activities used to verify that the quality system is operating and reflective of quality practices. Examples include project planning, standard operating procedures (SOPs), analytical chemistry data validation, and project and program reviews. Tetra Tech views QA not as just a series of requirements and procedures, but also as a management discipline that results in validated, verifiable, and documented information. Moreover, QA is a discipline that begins with effective and conscientious work planning and ends with a carefully constructed set of checks and balances designed to ensure that uncertainty has been reduced to a known and practical minimum. • Develop, incorporate into each work plan, and implement an acceptable, appropriate, and cost-effective program of QA and QC activities at the onset of each project effort involving data collection and deliverable preparation to ensure the adequacy of the technical product specified by the client. • Ensure that technical work products generated for each project are complete, accurate, and delivered on time and that the work products are focused, are suitable for the intended purpose, and meet the client's standards of quality, as well as professional standards established by technical and scientific disciplines. • Identify deficiencies, coordinate expeditious resolutions, and revise QA/QC procedures in a timely and systematic manner, as needed. • Ensure that the written and graphical quality of deliverables submitted to clients meets or exceeds professional standards through careful preparation and review. • Use the results of QA/QC reviews to identify and implement quality improvement for future work products. Tetra Tech recognizes that technical problems might occur at any point during the planning, execution, review, and reporting phases of a project. Potential problems can often be avoided or minimized by carefully planning and scheduling the work; assigning the most qualified and appropriate staff; and, most important, clearly communicating objectives and monitoring the progress of the required effort. Tracking of compliance with client- specified and state-required QA requirements is the responsible of the Project Manager, who coordinates and communicates QA/QC review with appropriate staff and the client. Laboratory instruments and equipment will be maintained according to the schedule and procedures established by the analytical method. Maintenance of field instruments will be based on manufacturer instructions and the amount of use that the instruments receive. Maintenance records will be maintained in the logbook for the study. aTETRA TECH 24 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan The project team will review and organize the results provided by laboratories. The data must be reviewed for outliers/anomalies and such findings documented. Duplicate samples will also be reviewed after receipt of the laboratory results. Duplicate samples with a relative percent difference greater than ten percent will initiate a corrective action sequence that may involve the collection of additional samples or refinements to the methodologies employed. Quality assurance measures implemented in the study will be described in the modeling report documenting monitoring and modeling results. This will include an assessment of measurement data accuracy, precision, and completeness, and any significant QA problems and recommended solutions. The modeling report will ultimately be provided to DWR for use in NPDES permit limit development. 5.7 CUSTODY DOCUMENTATION Chain-of-custody forms need to be maintained as the normal procedure to ensure samples are traceable from collection to receipt at the analyzing laboratory. The custody forms will include the name and the person delivering the samples, the date and time of delivery, project number, collection location, sample ID, and date and time of collection. Chain-of-custody documentation will accompany samples and laboratory results. 5.8 HEALTH AND SAFETY PLAN The sampling team developed a Health & Safety Plan (HASP)for initial field reconnaissance in April 2022 and will update that plan for any future planned field sampling events. The purpose of the HASP is to guide appropriate actions while conducting the water quality assessments. It includes emergency contact information, local hospital and emergency room information, and daily health and safety checklists to be completed before fieldwork begins. It is the responsibility of each staff member participating in the field work to know and implement the HASP. Tetra Tech will also prepare a separate HASP to ensure that field sample collection by Tetra Tech personnel complies with all applicable Occupational Safety and Health Administration (OSHA) standards, as well as Tetra Tech health and safety policies 5.9 POST-MONITORING DATA MANAGEMENT Data collected in the field will be properly managed and organized to ensure quality and availability for use to support the modeling portion of the study. In cases in which Tetra Tech enters data from hardcopy reports or data sheets into a standard database, the Tetra Tech QC officer(or designee) compares twenty (20) percent of data entries to the original hardcopy data sheets. The percentage of incorrectly entered data should not exceed 1 percent. If the percentage of incorrectly entered data exceeds 1 percent for a single staff member, the Tetra Tech QC officer(or designee)will review an additional 20 percent of the data entry performed by that staff member to determine whether that staff member is performing at an acceptable level. If the percentage of incorrect data entries for the additional sources evaluated exceeds 1 percent, the Tetra Tech QC officer(or designee) might evaluate one hundred (100) percent of the data entries performed by that staff member to ensure accuracy of the information. The Tetra Tech QC officer resolves any discrepancies in data entries with the technical staff members who originally performed the transfers during the review process to ensure one hundred (100) percent agreement in data entries for the sources. When compiling existing data, Tetra Tech will independently check transferred data by independently checking each different file type (i.e., a file with different structure or legacy), confirming the first, last, and a selected middle portion of the data were transferred correctly. More files (up to ten (10) percent)will be reviewed if files are processed individually while fewer checks (no less than 2 data files of each type)will be used for automated to semi-automated procedures. All identified data transfer errors will be corrected, and the Tetra Tech QC officer(or designee)will perform a follow-up review of the corrected components to ensure that the errors have been corrected. aTETRA TECH 25 July 28, 2022 WSACC Permitting Support Revised Rocky River Monitoring and Modeling Plan 6.0 ANTICIPATED DELIVERABLES A draft monitoring and modeling report will be delivered including documentation of all data sources and final results. Modeling assumptions and elements of uncertainty will be clearly documented to support use by Black& Veatch, WSACC, and DWR in establishing the basis for permit conditions. As needed, a meeting will be conducted with all parties to review results and discuss any potential concerns or needed model/report modifications. A final report and final modeling files will be submitted for use by all parties. OTETRA TECH 26 July 28, 2022