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HomeMy WebLinkAboutSUB202000190 Study 2020-12-09 South Fork Rivanna River TMDL Study First Technical Advisory Committee Meeting December 9, 2020 Al 4x _ AoMMwrir - J 1\\ N ` _ Dr le EP L ,*-- ' i q� my Augusta County -`�� Y wri.�UInk _ J a.n�� N.t.1".1 [.arty,.ill-ill- CI t t,e.--- - Y.', ' t' ' Y N.` 1 ,Chailotteswille ,n:svme I 14.A ull Run Legend % . `— / f- "t �i Impaired streams 1 • Streams \ - North Gaanlen Watershed boundaries \ well...) Q 1.25 2.5 5 75 1% h fp My Sea.ln'N.CQErpe.em,.MEMi inerore VCary.GEHG0 USGS i*U OPS NUC/W Ga0Beee . a." eGJJ.F.duw•Fmneax.a.InaEms.LWnMET,.EMCHmIMagIfagl.MSIEPa,uwmNM.G�P pp./r n�.4MP ramaNua,ryare.Uus U..r Gammrnr Figure 1. Location of South Fork Rivanna River watershed and associated impairments. 1. Summary of Impairments The 267 mi2 South Fork Rivanna River(SF Rivanna) watershed is located in Albemarle County. Thirteen impaired streams within the watershed are to be included in this study (Table 1). These streams have been listed on the 303(d) Impaired Waters List with a biological impairment. Monitoring data collected by both the Virginia Department of Environmental Quality(DEQ) and the Rivanna Conservation Alliance (RCA) has shown that the aquatic macroinvertebrate community has been negatively impacted by pollution in the watershed. These data indicate that the streams do not support the aquatic life use designation,resulting in their impairment listing. Table 1.Impairments to be included in the South Fork Rivanna River TMDL study. Waterbody Name Impairment Description Length Initial Listing (Miles) Date 1 Broad Axe Run Headwaters to confluence with Mechums River 8.31 2004 Waterbody Name Impairment Description Length Initial Listing (Miles) Date Lickinghole Creek Headwaters to confluence with Mechums River 8.93 2010 Confluence with Stockton to Lickinghole confluence 2.07 2004 Mechums River Headwaters to confluence with Stockton Creek 13.09 2004 Spring Creek Headwaters to upper end of Lake Albemarle 3.48 2012 Slabtown Branch Headwaters to confluence with Lickinghole Creek 4.92 2010 Parrott Branch X-trib Headwaters to confluence with Parrott Creek 1.15 2010 Fishing Creek Headwaters to confluence with SF Rivanna River 12.53 2012 Reservoir 5 mile upper limit of PWS designation to confluence with 2,56 2008 SF Rivanna Reservoir Ivy Creek Little Ivy Creek confluence to 5 mile upper limit of PWS 4.02 2008 designation Headwaters to confluence with Little Ivy Creek 5.49 2010 Little Ivy Creek X-trib Headwaters to confluence with Ivy Creek 4.44 2016 Naked Creek Headwaters to confluence with SF Rivanna River 9.82 2010 Powell Creek Headwaters to confluence with SF Rivanna River 10.36 2010 SF Rivanna RWSA public water intake to confluence with Rivanna 3.47 2010 River SF Rivanna X-trib Headwaters to confluence with SF Rivanna River 3.2 2010 2. Stressor Analysis Approach The goal of the Stressor Analysis is to identify the pollutant(s) responsible for the benthic impairment. This is accomplished by assembling all available data on potential stressors to the aquatic community and weighing the likelihood that each pollutant may be a stressor to aquatic macroinvertebrates in each stream. Table 2 shows the pollutants evaluated as stressors in the SF Rivanna River watershed. Each potential stressor is assigned to one of three categories: non- stressor,possible stressor and probable stressor through this process. Table 2. Candidate stressors evaluated in the stressor analysis. Pollutants pH Dissolved Sulfate Ammonia Dissolved Oxygen Total Dissolved Ions Dissolved Metals Temperature Suspended Solids Sediment Toxics Conductivity Deposited Sediment Sediment Metals Dissolved Chloride Organic Matter Pesticides Dissolved Sodium Nitrogen Polycyclic Aromatic Hydrocarbons(PAHs) Dissolved Potassium Phosphorus Polychlorinated Biphenyls(PCBs) Additional Contributing Factors Habitat Historic Land Use Practices and Existing Dams and Impoundments Dams Legacy Sediment Current Land Use Practices DEQ used a decision making tool developed by EPA, known as CADDIS (Causal Analysis Diagnosis Decision Information System), to weigh the likelihood that each pollutant was a probable stressor to aquatic macroinvertebrates in each stream. The CADDIS approach evaluates 14 lines of evidence that support or refute each potential stressor as the cause of impairment. In each stream, each candidate stressor is scored from-3 to+3 based on each line of evidence. Total scores across all lines of evidence are then summed and those with scores greater than 3 are classified as probable stressors(Table 3). Table 3. CADDIS scoring system and classification framework for stressors. Total Score Classification <-2 -1 Non-Stressor 0 +1 +2 Possible Stressor +3 +4 +5 Probable Stressor 3. Data Used for Stressor Analysis A large and comprehensive data set was available and used for the SF Rivanna stressor analysis (Table 4). Benthic data were available from 16 Virginia Department of Environmental Quality (DEQ) stations and 22 Rivanna Conservation Alliance (RCA) stations. Historic water quality information was available from 18 DEQ monitoring sites between 2005 and 2020. James Madison University(JMU) supplemented this data set with continuous (15-minute interval) monitoring of conventional water quality parameters over 1-2 week periods at four sites (Fishing Creek, Ivy Creek,Mechums River and SF Rivanna River)in summer 2020.Physical measurements of habitat, relative bed stability, and land use were also made throughout the watershed. Results from other published studies in the watershed were also consulted to corroborate the findings of the stressor analysis. Table 4.Data used for SF Rivanna stressor analysis. Data Type Source Locations Timeframe Description Analysis Performed Family -spatial trends DEQ 16 sites 2005-2019 or -temporal trends Benthic organism counts,8 metric -individual metric analysis scores, 1 multi-metric(SCI RCA 22 sites 2004-2019 -community composition score) -functional feeding guilds Water quality parameters -spatial trends DEQ 18 sites 2005-2020 measured at various times -temporal trends at various locations -regression with benthic data Water Quality -comparison to water quality Data Continuous water quality standards JMU 4 sites Summer monitoring(15-minute -comparison to regional 2020 interval)of 5 parameters references over 1-2 week period -comparison to effect thresholds -regression with benthic data Visual habitat assessment -comparison to regional Habitat DEQ 16 sites 2005-2019 including 10 metrics and 1 references multi-metric score -comparison to effect thresholds -individual metric analysis Measurements of channel -regression with benthic data Geomorphic structure,dimension,bed -comparison to effect (Relative Bed DEQ 9 sites 2009-2019 substrate,woody debris, thresholds Stability) and estimated stability of the channel bed 1-m resolution spatial land -spatial analysis by Land Use VGIN State-wide 2016 use data based on 2011- subwatershed 2014 orthophotography -regression with benthic data -primary model input StreamWatch Land use Study(Murphy,J. 2010.Land Use and Stream Health in the Rivanna Basin, 2007-2009.Stream Watch,Charlottesville,VA.) RCA Biennial Stream Health Reports VCU Instar Study(Garman,G.,S.Mclninch, D. Hopler,and W.Shuart.2010.Stream Health Ecological Assessment for the Rivanna River Basin,Virginia.) Other RRBC Healthy Waters Project Report(Rivanna River Basin Commission.2011. Final Report: Corroborating 319BAY-2007-21PT. Rivanna Healthy Waters Pilot Project.RRBC,Charlottesville,VA.) Studies RWSA South Fork Rivanna River Reservoir Study(Rivanna Water and Sewer Authority.2018. Reservoir Water Quality and Management Assessment,Charlottesville,VA.) Streambed Permeability Study(May,C.2008.Streambed Permeability and Substrate JMU Sampling in Selected Tributaries to the Rivanna River.James Madison University, Harrisonburg,VA.) Other academic and scientific references 4. Preliminary Stressor Analysis Findings The stressor analysis is still ongoing, and not all data have been incorporated yet. However, the bulk of the analysis conducted to date does provide preliminary evidence of probable stressors. A summary of total scores assigned to each stream through the CADDIS process is provided in Table 5. Table 5.Total causal analysis scores by stream and by candidate stressor.Green indicates non-stressors,orange indicates possible stressors, and red indicates probable stressors. Y . 42 a) C 17 U17 `) a) ~ Q a) X N m m ca Candidate Stressor x o Y T 2 m C = = 2 a rn ate) rn > v — 3 MI "0 C C m c a� o > > 2 m >, U .".. aai CD co Y co A o LL LL O- m it > J J Z a. d to N to fn pH -14 -14 -17 -16 -17 -14 -15 -12 -15 -13 -14 -14 -17 Temperature -8 -10 -7 -4 -8 -13 -12 -8 -8 -3 0 -5 -10 Conductivity/Total Dissolved Solids -14 -20 -14 -15 -14 -19 -16 -3 -14 -18 -15 -15 -19 Dissolved Sodium and Sulfate 0 -12 -10 -6 -8 -7 -10 0 -7 -10 -6 -3 -6 Ammonia -3 -3 -6 -6 -3 -6 -3 -1 -3 -3 -3 -3 -3 Dissolved Metals -4 -4 -4 -4 -4 -8 -4 -4 -4 -4 -8 -4 -4 Sediment Toxics -3 -3 -3 -3 -3 -12 -3 -2 -2 -3 -12 -2 -4 Dissolved Chloride and Potassium -3 -8 -9 -10 -9 -8 -11 -3 -3 -10 -6 -6 -10 Organic Matter -4 -4 -4 -4 -4 -3 -4 -4 -4 -4 0 -4 -5 Nitrogen -7 -1 -5 -8 -6 -11 -4 9 -4 -7 -3 -3 -10 Phosphorus -9 -1 -8 -6 -6 -4 -1 -2 -8 -6 5 -3 -7 Dissolved Oxygen -13 0 -9 -14 -11 -15 -8 -10 -6 -10 4 -4 -16 Sediment 23 25 23 15 17 19 20 18 24 17 22 19 4 Dam - - - - - - - - - - 3 - - Sediment Preliminary findings point to sediment as a likely stressor in each of the impaired watersheds. Some lines of evidence supporting this preliminary finding include: • Taxonomic community structure indicated shifts to Dipteran-dominated communities that prefer sediment and away from Ephemeroptera, Plecoptera, and Trichoptera, which generally prefer clean substrate. Trichoptera present in impaired streams were predominantly Hydropsychidae,which is also indicative of excess sediment in the stream. Hydropsychidae is a family of net-spinning caddisflies, which spin nets of silk to trap particles as a food source. The Hydropsychidae are more pollution tolerant than most other Trichopteran families and can thrive in enriched and sediment laden environments. The example below from Powell Creek in Forest Lakes (downstream of the Ashwood Blvd. bridge) demonstrates the typical community structure observed in the impaired streams in the watershed. Long Island Creek:Small Reference Stream Powell Creek 4 4et- •Gastropoda • Pelecypoda • Lumbriculida •Plecoptera •Coleoptera • Ephemeroptera •Trichoptera (Hydro) •Trichoptera minus Hydro • Diptera •Other • Functional feeding group analysis indicated shifts to filterers and collectors that prefer sediment conditions and away from shredders and scrapers that prefer clean substrate. The example from Lickinghole Creek at the Route 680 Bridge in Crozet demonstrates this shift in community composition. •Collector it Filterer Predator ■Scraper ■Shredder 100% 90% 0 80% N 70% a 60% v 50% "c 40% £ 30% u 20% 10% 0% Lickinghole Creek Long Island • Habitat metrics that indicate excess sediment and substrate embeddedness (SEDIMENT and EMBED) were low compared to reference conditions. Additionally, streambank stability and vegetation metrics (BANKS and BANKVEG) were typically lower than reference conditions,suggesting bank erosion is an issue of concern in the impaired streams (example below from the Fishing Creek monitoring station off of Willwood Drive in Earlysville). •Fishing Creek ■Long Island Creek 25 20 * * * * OIidiiIIiiJJii � c 15 1to /1!_' 10 to 5 0 0P y�0\ Jr � • Relative bed stability measurements indicated that bottom substrates in the impaired streams were dominated by sand and fine material when compared to a similar reference stream where bottom substrates were predominantly gravel, cobble and bedrock. The example below shows bottom substrate composition along a 150 meter reach in Broad Axe Run upstream of Route 682 just above Interstate 64. Broad Axe Run 100 90 80 70 60 50 40 30 20 10 0 Broad Axe Run Long Island •Bedrock •Cobble ■Coarse Gravel ■Fine Gravel •Sand ■Fines ■Other • Visual evidence of incised stream channels, steep and unstable streambanks, and sand- dominated bed substrate are all indicative of a sediment stressor. Phosphorus For the impaired segment of the South Fork Rivanna River below the reservoir, preliminary findings point to phosphorus as a likely stressor in addition to sediment. Some lines of evidence supporting this preliminary finding include: • Dissolved oxygen periodically dipped into the range of high probability for stressor effects and frequently approached the water quality standard (WQS) of 5 mg/L during diurnal monitoring in July 2020. SF Rivanna River J 12 None E 10 [Lo C 8 Me um O 8 d 4 High o 2 —2-RRS001.8 I y p 0 —WQS 0 0 0 0 0 0 0 0 NNN NNNNNN CO - OO Q) 0 N N NNN ti N- I- • Over 40%of total phosphorus data points fell within the medium probability of stressor effects category and 10% of points fell within the high probability category at the South Fork Rivanna River monitoring station below the reservoir. 0.26 0.24 0.22 0.2 0.0 E 0.18 High `; 0.16 s 0.14 a p 0.12 a 0.1 0.08 Medium 0.06 0.04 Low11111 0.02 None 1 1 0 Mechums SF Rivanna Reference • RWSA study of the reservoir showed average TP concentration between 2015 and 2017 was 0.054 mg/L, with a maximum value of 0.191 mg/L. Monitoring of chlorophyll a (a measure of phytoplankton) in the reservoir provides further evidence of nutrient enrichment. Secchi depths recorded between 2015 and 2017 indicated that the reservoir is eutrophic, with a mean depth of 1.64 m between 2015-2017 at the deeper of the two monitoring stations, and a mean depth of 1.3 m at the shallower station. Typically, secchi depths of less than 2 m are indicative of a eutrophic state. • Nitrogen to phosphorus ratios in SF Rivanna streams indicate that phosphorus is the limiting nutrient that would control algal growth and subsequent dissolved oxygen levels. Nitrogen In addition to sediment, nitrogen was identified as a probable stressor in X-Trib Parrott Branch. Some lines of evidence supporting this preliminary finding include: • Total nitrogen concentrations fell within the medium probability of stressor effects range, with multiple excursions into the high probability range. 3 2.5 High 2 TS E v1.5 Medium 00 0 y 2 1 ST 0.5 Low 1 oil None 1 i 0 G`ee aP+e (�e0- °.c 2��°� C�e� (�¢- Gre Ci `.DQa �e ,x4> yea° ry .`mob ` Q° � �a ‹.r c,Q • Considerable shifts in the benthic community to pollution tolerant organisms including Lumbriculida (aquatic worms), which comprised nearly 40% of the population and are highly tolerant of low dissolved oxygen concentrations. Additionally, sensitive EPT taxa were entirely absent from the stream. Parrott Branch X-Trib Long Island Creek:Small Reference Stream \ / •Gastropoda • Pelecypoda • Lumbriculida •Plecoptera • Coleoptera • Ephemeroptera •Trichoptera (Hydro) •Trichoptera minus Hydro • Diptera •Other Additional Contributing Factors In addition to the probable stressors identified above, there are several contributing factors that also influence these watersheds. • Historic Land Disturbance -The widespread deforestation and intensive agriculture of the 1820-1930s in the piedmont region have produced a legacy of accumulated sediment in valley bottoms that characterize present-day piedmont streams. This legacy contributes to current sediment loads, channel morphology, and stream habitat conditions. • Historic Dams - In addition to historic forest clearing and intensive agriculture in the piedmont region,Walter and Merritts(2008)suggest that the presence of historic mill dams significantly contributed to the present morphology of streams in the region and resulting sediment loads. • Imperviousness — The most significant land use correlation with benthic health was the percentage of imperviousness within SF Rivanna watersheds (r2 = 0.86). As the imperviousness of the watershed increased, benthic scores decreased. Based on the regression relationship developed for the SF Rivanna,impaired stream conditions with SCI scores <60 were predicted at levels of watershed imperviousness above 3.8%. 70 • 60 : • • • 50 • ... - - - - • v 0 40 - V) 30 • • • 20 10 1 0 0% 10% 20% 30% 40% 50% %Impervious Cover in Watershed • Existing Impoundments-There are a number of existing impoundments throughout the SF Rivanna River drainage, most notably the SF Rivanna River Reservoir. Diurnal dissolved oxygen patterns in Fishing Creek also suggest that the four impoundments upstream of the monitoring station may be impacting nutrient cycling in the creek. The process of damming a river and creating a lake inherently alters the ecology of the stream by changing flow regimes, temperature regimes, and nutrient and organic matter dynamics.