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HomeMy WebLinkAbout2020.11.18_CCOA.p1_Outfall002MassLoadingProtocolSITE CONVEYANCE NETWORK AND OUTFALL 002 PFAS MASS LOADING CALCULATION PROTOCOL Chemours Fayetteville Works Prepared for The Chemours Company FC, LLC 22828 NC Highway 87 Fayetteville, NC 28306 Prepared by Geosyntec Consultants of NC, PC 2501 Blue Ridge Road, Suite 430 Raleigh, NC 27607 Project Number TR0795 Version 1: August 31, 2020 Version 2: November 2020 DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 11/18/2020 Geosyntec Consultants NC P.C. RESPONSES TO NCDEQ COMMENTS Chemours Fayetteville Works TR0795 November 2020 On October 5, 2020, Chemours received comments from the North Carolina Department of Environmental Quality (NCDEQ) on the protocol document “Site Conveyance Network and Outfall 002 PFAS Mass Loading Calculation Protocol (Version 1)” submitted by Chemours on August 31, 2020 as required under Paragraph 1 (c)(ii) of the Addendum to Consent Order Paragraph 12. The table below summarizes the comments received by NCDEQ, Chemours’ responses to those comments, and the subsequent changes made in this second version of the protocol document. Comment # Protocol Document Comment Description Response Section Edit 1 Outfall 002 For the Site Conveyance Network, the facility suggests the use of 3.5 days composite samples and 24-hour composite sampling. The 3.5 days sampling is inconsistent with our regulations and underestimates the load, only 24-hour composite data should be used in the calculations. The protocol will specify using 24-hour composite samples collected from Outfall 002. The protocol calculation will still retain the ability to consider 3.5-day composite samples in calculations for historical data sets where in the past only 3.5-day composite samples were collected. Section 3.4 2 Outfall 002 The document mentions the phrase “estimated PFAS concentration” several times. Please clarify the use of that term and note that measured PFAS concentrations are expected to be used in the calculations. For example, k = is the measured or estimated total PFAS concentration. All mass loading quantities will be determined based on measured concentration values. The word document has been edited accordingly to provide clarity. Across Document 3 Outfall 002 The protocol states how PFAS concentrations from the site-conveyance network may be estimated if there are data gaps, and for the intake, estimated concentrations will be determined from Transport pathways 1 (upstream at mile 76), 2 (Willis Creek estimated modeled load), and 3 (aerial deposition). Actual concentrations will also be measured monthly with a 24hr composite sample at the intake. It would be better to take weekly 24hr composite samples at the intake to determine loading from the site-conveyance network. This would also provide more data comparison to refine the loading as estimated from Pathways 1-3 since two of those inputs are modeled loading and not actual measurements. The last sentence of 2.4 says; For the purposes of these calculations, flows at the river intake are assumed to be equal to dry weather Outfall 002 flows. This seems to indicate there is no consumptive loss from the variety of processes used at the industrial site. Shouldn't the water balance include water lost from hauling process wastewater and evaporative loss from various processes? 1. Intake sampling described in the original protocol text outlined usage of existing samplingprograms as Site NPDES permit has not yet been renewed. Chemours agrees as part of thisprotocol to specify weekly 24-hour composite samples be collected at the Intake in assessingloading from the site-conveyance network at Outfall 002. To avoid duplicative sampling, Chemours will modify this protocol to incorporate and be consistent with intake samplingfrequency requirements at such time as the NPDES permit for Outfall 002 is renewed. 2. Determinations of PFAS mass loading from the river water intake will be calculated usingmeasured intake flows from the transfer pipe between the river water pumps and the facility.This will more accurately reflect PFAS loads entering the Site via the intake. The document previously had assumed that intake flows were equal to measured Outfall 002 flows. Sections 2.2 and 2.4 4 Outfall 002 The document suggests the use of a 60-day rolling average. This is inconsistent with our standard procedures, a 30-day rolling average should be used. The protocol has been modified to specify a 30-day rolling average. Sections 3.4 and 3.5 5 Outfall 002 The list of PFAS parameters that will be analyzed should match the list contained in the recently issued NPDES permit – NC0089915 and as comprised during CO negotiations. The sampling described in this protocol document is being implemented pursuant to paragraph 1(c) of the Consent Order Addendum entered into court on August 13, 2020. The Consent Order Addendum requires analysis for PFAS compounds listed in Attachment C of the Consent Order (CO) (February 25, 2019). -- 6 Outfall 002 The CO states that for Outfall 002, Chemours shall also conduct 24-hour composite sampling within 24 hours of any rain event predicted two days before with at least a 70% likelihood to be of 1 inch or greater over a 24-hour period. The weather service used for the precipitation prediction should be stated and approved by the department. National Oceanic and Atmospheric Administration (NOAA) National Weather Service hourly forecasts (for the Fayetteville Regional Airport) will be used to track rainfall predictions at the site. A link to this weather station is included in the document. Section 2.3 11 Outfall 002 Section 3.1. The variables “j” and “k” are not defined in Section 3.1. The document has been revised to include definitions for “j” and “k”. Section 3.1 12 Outfall 002 Section 3.2 provides Equation #2 and has a variable “F” that needs further explanation. Is the factor a constant or will it change each time? The factor is constant; the text has been revised. Section 3.2 DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load ii November 2020 TABLE OF CONTENTS 1 INTRODUCTION ................................................................................................ 1 2 OUTFALL 002 AND RIVER INTAKE SAMPLING ......................................... 2 2.1 Outfall 002 Sample Types ........................................................................... 2 2.2 River Intake Samples ................................................................................... 2 2.3 Consent Order Addendum Sampling Requirements ................................... 2 2.4 Flow Measurement Methods ....................................................................... 3 3 PFAS MASS LOADING CALCULATION METHODOLOGY ........................ 4 3.1 Total Mass Load Calculation Methodology ................................................ 4 3.2 Loading at Outfall 002 ................................................................................. 5 3.3 Loading from River Water Intake ............................................................... 6 3.4 Concentrations at Outfall 002 ...................................................................... 7 3.5 Concentrations in Site River Water Intake .................................................. 7 3.6 Potential Adjustments .................................................................................. 8 LIST OF TABLES Table 1: PFAS Analytical Methods and Analyte List LIST OF FIGURES Figure 1: Outfall 002 Sampling Locations Figure 2: Flowchart for Determining the Concentrations for Loading at Outfall 002 Figure 3: Flowchart for Determining the Concentrations for Loading at the River Water Intake DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load iii November 2020 LIST OF ABBREVIATIONS CO Consent Order hr hour mL milliliter ng/L nanograms per liter NOAA National Oceanic and Atmospheric Administration PFAS per- and polyfluoroalkyl substances DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load 1 November 2020 1 INTRODUCTION Geosyntec Consultants of NC, PC (Geosyntec) has prepared this Protocol for establishing current mass loading from Outfall 002 to the Cape Fear River (“Outfall 002 Trendline”) on behalf of The Chemours Company FC, LLC (Chemours) pursuant to the requirements of Paragraph 1(c)(ii) of the Addendum to Consent Order Paragraph 12 (CO Addendum). The objective of this document is to describe the sampling activities and calculation methods associated with per- and polyfluoroalkyl substances (PFAS) mass loading at Outfall 002. The CO Addendum specifies that PFAS mass loading calculations use the PFAS compounds listed in Attachment C of the Consent Order (CO) (February 25, 2019). Table 1 lists the Attachment C PFAS compounds and the associated analytical methods. Specifically, this protocol describes how the PFAS loads reaching the river at Outfall 002 from the Site conveyance network are calculated by estimating the PFAS load in river water intake water and the PFAS load at Outfall 002. The remainder of this document is organized as follows: •Section 2 – Outfall 002 and River Intake Sampling, which describes the background and protocols for sampling and flow measurements at Outfall 002; and •Section 3 – PFAS Mass Loading Calculation Method, which describes the methods used to calculate loading using composite samples collected at Outfall 002. DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load 2 November 2020 2 OUTFALL 002 AND RIVER INTAKE SAMPLING This section provides an overview of the types of sampling and flow measurements conducted at Outfall 002 and the River Intake. 2.1 Outfall 002 Sample Types PFAS mass loading at Outfall 002 can be assessed by sampling the discharge at Outfall 002 using 24-hour (hr) composite samples, collected as flow-weighted samples. Samples have been collected using an auto-sampler set to collect 150-mL aliquots for every 200,000 gallons of flow. The location of the autosampler is shown in Figure 1. 2.2 River Intake Samples The site draws water from the Cape Fear River which at the River Water intake already contains PFAS from upstream sources. This water, after use at the Site, is then discharged at Outfall 002. As part of the Cape Fear River PFAS Mass Loading Calculation Protocol (Geosyntec, 2020), the River Water Intake at Facility location will be sampled as a 24-hr composite sample once per week. The River Water Intake at the Facility location represents water drawn in by the facility through the intake piping. To avoid potential future duplicative sampling, Chemours will modify this protocol to incorporate and be consistent with intake sampling frequency requirements per the renewed NPDES permit for Outfall 002. 2.3 Consent Order Addendum Sampling Requirements The CO Addendum requirements for the PFAS sampling program at Outfall 002, as detailed in Paragraph 1(c)(i) of the CO Addendum, are as follows: c.Outfall 002 Trendline: i.Starting no later than August 31, 2020, Chemours shall, each week for at least twelve consecutive weeks, take a 24-hour composite sample from Outfall 002 and analyze for the PFAS listed in Attachment C to the Consent Order. Chemours shall also conduct 24-hour composite sampling within 24 hours of any rain event predicted two days before with at least a 70% likelihood to be of 1 inch or greater over a 24-hour period. Chemours shall record the flow through Outfall 002 for each sampling event. To fulfill these requirements, 24-hr composite samples will be collected weekly for at least twelve weeks, in addition to within 24 hours of a rain event that meets the criteria specified in the CO Addendum. National Oceanic and Atmospheric Administration (NOAA) National Weather Service hourly forecasts will be used to track rainfall DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load 3 November 2020 predictions at the site.1 Samples will be sent to an approved external laboratory for analysis. The PFAS analyte list to be used (Table 1) includes all Consent Order Attachment C PFAS. 2.4 Flow Measurement Methods The flow at Outfall 002 will be measured using a flowmeter to record flow readings from a 60-inch Parshall flume (Figure 1). Flow measurements will be translated into a flow per time unit, such as gallons per hour. If flow measurements are unable to be collected based on temporary equipment malfunction or other unforeseen circumstances, flow at Outfall 002 will be calculated for purposes of these calculations. For dry weather flow data gaps, dry weather flow measurements close in time to the data gap along with facility water usage records will be used to estimate dry weather flows at Outfall 002. If the data gaps in flow measurement occur during wet weather, the Site hydrologic model will be used to estimate stormwater flows at Outfall 002, and these estimates will be summed with an estimate of the dry weather flow for that same time period. For the purposes of these calculations, flows at the river intake will be obtained from the Site flow measurement devices.2 1 Hourly weather forecast graphs for Fayetteville Regional Airport, North Carolina can be found here: https://forecast.weather.gov/MapClick.php?lat=34.99&lon=-78.88&lg=english&FcstType=graphical 2 Located in the pipe between the river water pumps and the facility. DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load 4 November 2020 3 PFAS MASS LOADING CALCULATION METHODOLOGY This section presents the methodology to calculate PFAS mass loading at Outfall 002. The mass loading at Outfall 002 is calculated using measured PFAS concentrations and flows at Outfall 002. The mass loading in river water at the intake is also calculated using measured PFAS concentrations, as well as measured flows, from river water at the intake. The mass loading in river water at the intake is then subtracted from the mass loading at Outfall 002 to determine the mass load reaching the river at Outfall 002 from the Site conveyance network. The calculations presented here are suitable for evaluating the mass loads of any given set of selected PFAS. For the purposes of calculations and reporting for Paragraph 1 of the CO Addendum, the set of PFAS will be those listed in Attachment C of the Consent Order and listed here as Table 1. 3.1 Total Mass Load Calculation Methodology This sub-section describes the methodology for calculating PFAS mass loading over a given time period. The mass loads over the given time intervals will be summed, as shown in Equation 1 below: Equation 1: Total Mass Loading at Outfall 002 𝑀𝑁𝐹002 =∑𝑚𝑁𝐹002,𝑛 𝑁 𝑛=1 −𝑚𝑖𝑛𝑡𝑎𝑖𝑒,𝑛 where, •𝑀𝑁𝐹002 = is the total PFAS mass load at Outfall 002 for a given number of time periods “N”, as mass per time, typically pounds per day, that originated from the Site conveyance network; •𝑚𝑁𝐹002,𝑛 = is the total PFAS mass load at Outfall 002 for a given time interval “n” (mass per time), calculated by summing (or subdividing) the appropriate values of 𝑚𝑁𝐹002,𝑖; •𝑚𝑖𝑛𝑡𝑎𝑖𝑒,𝑛 = is the total PFAS mass load in river water from the intake for a given time interval “n” (mass per time), calculated by summing (or subdividing) the appropriate values of 𝑚𝑖𝑛𝑡𝑎𝑖𝑒,𝑖; •𝑖= is time interval, applicable to the total PFAS load at Outfall 002 (represents either the 24-hr composite period, or time interval of data gap [i.e., no 24-hr composite sample collection], described further in Section 3.4); DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load 5 November 2020 •𝑚= represents individual time intervals in a time period to assess mass loading at Outfall 002; •𝑀= is the total number of time intervals in a time period to assess mass loading at Outfall 002; •𝑖= is time interval, applicable to the total PFAS load in river water from the intake (represents either the 24-hr composite period, or time interval of data gap [i.e., no composite sample collection], described further in Section 3.5). 3.2 Loading at Outfall 002 Measured concentrations, as well as measured flows at Outfall 002, are used to calculate mass loading at Outfall 002, as shown in Equation 2 below: Equation 2: Outfall 002 Mass Loading 𝑚𝑁𝐹002,j = 𝐶𝑁𝐹002,𝑖 × 𝑄𝑁𝐹002,𝑖 × 𝐹 =∑𝑐𝑁𝐹002,j,iI𝑖=1 × 𝑄𝑁𝐹002,j × 𝐹 where, •𝑚𝑁𝐹002,𝑖 = is the total PFAS mass load at Outfall 002 as measured in mass for a given time interval, “j”; •𝑖= is time interval (represents either the 24-hr composite period, or time interval of data gap [i.e., no 24-hr composite sample collection], described further in Section 3.4); •𝐶𝑁𝐹002,𝑖 = is the measured or calculated total PFAS concentration at Outfall 002 for a given time interval, “j” (described further in Section 3.4); •𝑄𝑁𝐹002,𝑖 = is the total measured flow at Outfall 002 in a given time interval “j”; •𝐹 = is a conversion factor (to convert from concentrations in nanograms per liter (ng/L) multiplied by flow in gallons per time unit to load in pounds per time unit; this conversion factor is constant assuming the same units of time for flow and loading3); 3 For example, to convert from concentration in ng/L multiplied by flow in gallons per day to load in pounds per day, a conversation factor of 8.35 x 10-12 is consistently used. To convert from concentration in ng/L multiplied by flow in gallons per hour to load in pounds per hour, the conversation factor of 8.35 x 10-12 is still used. DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load 6 November 2020 •c𝑁𝐹002,j,i = is the measured or calculated concentration of the ith PFAS compound based on samples collected from Outfall 002; 𝑖= represents each of the PFAS compounds being evaluated; and 𝐼= represents total number of PFAS compounds included in the summation of total PFAS concentrations. 3.3 Loading from River Water Intake Measured concentrations, as well as measured flows from river water at the intake, are used to calculate mass loading in river water at the intake, as shown in Equation 3 below: Equation 3: River Intake Mass Loading 𝑚𝑖𝑛𝑡𝑎𝑖𝑒,k = 𝐶𝑖𝑛𝑡𝑎𝑖𝑒,𝑖 × 𝑄𝑖𝑛𝑡𝑎𝑖𝑒,𝑖 × 𝐹 =∑𝑐𝑖𝑛𝑡𝑎𝑖𝑒,𝑖,𝑖I𝑖=1 × 𝑄𝑖𝑛𝑡𝑎𝑖𝑒,𝑖 × 𝐹 where, •𝑚𝑖𝑛𝑡𝑎𝑖𝑒,𝑖 = is the total PFAS mass load in the river water at the intake as measured in mass for a given time interval, “k”; •𝑖= is time interval for calculating the mass loading (represents either the 24-hr composite period, or time interval of data gap [i.e., no composite sample collection], described further in Section 3.5); •𝐶𝑖𝑛𝑡𝑎𝑖𝑒,𝑖 = is the measured or calculated total PFAS concentration in the river water at the intake for a given time interval, “k” (described further in Section 3.5); •𝑄𝑖𝑛𝑡𝑎𝑖𝑒,𝑖 = is the total measured flow at the intake in a given time interval “k”; •𝐹 = is a conversion factor (to convert from concentrations in ng/L multiplied by flow in gallons per time unit to load in pounds per time unit; this conversion factor is constant assuming the same units of time for flow and loading); •c𝑖𝑛𝑡𝑎𝑖𝑒,k,i = is the measured or calculated concentration of the ith PFAS compound based on samples collected from the river water at the intake; •𝑖= represents each of the PFAS compounds being evaluated; and •𝐼= represents total number of PFAS compounds included in the summation of total PFAS concentrations. DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load 7 November 2020 3.4 Concentrations at Outfall 002 This section describes the methodology for calculating PFAS concentrations at Outfall 002 to be used in calculating mass loads. The methodology is also illustrated in Figure 2. The calculation methodology outlined here considers all collected 24-hr composite samples in a given time period, including cases where composite sample collection events do not occur successively (i.e., there could potentially be time gaps where a composite sample is not being collected). Historically, 3.5-day composite samples (i.e., 84-hr) were collected from Outfall 002. If this method is applied to past data sets, then 3.5-day composite samples will also be considered in the analysis. If any 24-hr and 3.5-day composite samples have overlapping durations, then only the 24-hr composite sample value will be considered for the overlapping duration time period. Sample concentrations will be assigned to the corresponding time period over which the composite sample was collected (24-hr composite samples). If there are data gaps (i.e., there are time gaps where a composite sample is not being collected), the time period will be assessed for whether it is considered “wet” or “dry”. Each time period with data gaps will be considered wet or dry based on the total precipitation depth measured in the preceding 72 hours, with “wet” defined as greater than 0.2 inches of precipitation in the preceding 72 hours (below this approximate rainfall threshold, minimal stormwater runoff generation is expected). A 30-day rolling average wet or dry concentration will be applied to the time periods with data gaps based on the wet or dry designation. To calculate the 30-day rolling wet and dry concentrations, each 24-hr composite sample result at Outfall 002 will be assigned wet or dry based on the definition noted above (where samples with greater than 0.2 inches of precipitation in the preceding 72 hours, based on the end of the composite sample collection period, are considered wet). The 30-day rolling wet and dry average sample concentrations will be calculated based on the sample dates reported for each composite sample (which represent the end of the composite sample collection period), and each sample result in the rolling 30-day period will be counted as one result in the calculation of the average (i.e., weighted evenly). 3.5 Concentrations in Site River Water Intake This section describes the methodology for calculating PFAS concentrations in river water at the intake to be used in calculating mass loads. The methodology is also illustrated in Figure 3. The calculation methodology outlined here considers all collected samples in a given time period (24-hr composites) and cases where composite sample collection events do not occur successively (i.e., there are time gaps where a composite sample is not being collected). DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Outfall 002 Mass Load 8 November 2020 Sample concentrations will be assigned to the corresponding 24-hr time period over which the composite sample was collected. Where there are data gaps (i.e., where no 24- hr composite sample is collected during a period of time), the 30-day rolling average river water intake sample concentrations will be calculated. 3.6 Potential Adjustments The calculation methodologies described in this section have been outlined based on the present understanding of Site conditions. If conditions or methods change, modifications may need to be made to this protocol. Modifications to the calculation methodologies will be described in future submitted reports. DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 TABLES DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 TABLE 1 PFAS ANALYTICAL METHODS AND ANALYTE LIST Chemours Fayetteville Works, North Carolina Geosyntec Consultants NC P.C. Analytical Method Common Name Chemical Name CASN Chemical Formula HFPO-DA*Hexafluoropropylene oxide dimer acid 13252-13-6 C6HF11O3 PEPA Perfluoro-2-ethoxypropionic acid (Formerly Perfluoroethoxypropyl carboxylic acid)267239-61-2 C5HF9O3 PFECA-G Perfluoro-4-isopropoxybutanoic acid 801212-59-9 C12H9F9O3S PFMOAA Perfluoro-2-methoxyacetic acid 674-13-5 C3HF5O3 PFO2HxA Perfluoro-3,5-dioxahexanoic acid (Formerly Perfluoro(3,5-dioxahexanoic) acid)39492-88-1 C4HF7O4 PFO3OA Perfluoro-3,5,7-trioxaoctanoic acid (Formerly Perfluoro(3,5,7-trioxaoctanoic) acid)39492-89-2 C5HF9O5 PFO4DA Perfluoro-3,5,7,9-tetraoxadecanoic acid (Formerly Perfluoro(3,5,7,9-tetraoxadecanoic) acid)39492-90-5 C6HF11O6 PMPA Perfluoro-2-methoxypropionic acid (Formerly 2,3,3,3-Tetrafluoro-2-(trifluoromethoxy)propanoic)13140-29-9 C4HF7O3 PFO5DA Perfluoro-3,5,7,9,11-pentaoxadodecanoic acid 39492-91-6 C7HF13O7 PS Acid (Formerly PFESA-BP1)Ethanesulfonic acid, 2-[1-[difluoro[(1,2,2-trifluoroethenyl)oxy]methyl]-1,2,2,2-tetrafluoroethoxy]-1,1,2,2- tetrafluoro- (Formerly PFESA-BP)29311-67-9 C7HF13O5S Hydro-PS Acid (Formerly PFESA-BP2)Ethanesulfonic acid, 2-[1-[difluoro(1,2,2,2-tetrafluoroethoxy)methyl]-1,2,2,2-tetrafluoroethoxy]-1,1,2,2- tetrafluoro- (Formerly PFESA-BP2)749836-20-2 C7H2F14O5S PFHpA*Perfluoroheptanoic acid 375-85-9 C7HF13O2 Notes: * - HFPO-DA and PFHpA are also analyzed by EPA Method 537 Mod. EPA - Environmental Protection Agency PFAS - Per- and Polyfluoroalkyl substances SOP - Standard Operating Procedure Table 3+ Lab SOP TR0795 Page 1 of 1 November 2020 DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 FIGURES DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3 Legend C:\Users\treeder\AppData\Roaming\Microsoft\Excel\[Charts%20and%20Tables_20201007 (version 1).xlsb]Table of Field Notes_TargOutfall 002 Sampling Locations Chemours Fayetteville Works, North CarolinaSampling Location Figure 1 Raleigh November 2020 River Water Intake at Facility 24-hr Composite and ContinuousFlow DocuSign Envelope ID: B3DB74C3-5B16-4298-9008-2BF4A9264DF3