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Home My WebLink AboutNC0082376_Report_20060206Division of Water Quality Biological Assessment Unit February 6, 2006 MEMORANDUM To: Jimmie Overton Through: Trish MacPherson From: Bill Crouch Subject: Benthic Macroinvertebrate survey of Unnamed Tributary of Falls Lake (Honeycutt Creek) associated with discharge points from Raleigh's E.M. Johnson WTP, Wake County, Neuse River Subbasin 01. BACKGROUND Susan Massengale (DWQ Office of Public Information) requested a resampling of the Unnamed Tributary (UT) of Falls Lake (Honeycutt Creek) to assess current conditions in the stream. This waterbody receives the discharge water from the City of Raleigh's E.M. Johnson Water Treatment Plant. Two previous investigations at the site (August 2002 and August 2005) utilized paired sampling locations, upstream and downstream of the Plant outfall. The 2002 study concluded that the pollution tolerant community downstream indicated lower water quality than above the Plant outfall. The August 2005 sampling revealed that conditions downstream of the outfall had improved, due to the collection of eight aquatic taxa that were absent in 2002. Essentially, the pollution tolerance of the aquatic macroinvertebrate community downstream of the outfall in August 2005 was the same as the one found at the control site (upstream). Differences in species composition between the upstream and downstream sites in August 2005 can be accounted for by the increase in water flow between the two sites (B- 050929). Neither site was assigned a bioclassification in 2002 or 2005 due to the small size of the watershed at both locations (<3 mi2). .E� / 1 EMJMmm Wfr \ /� Figure 1: Map of study area. SITE DESCRIPTIONS UT Falls Lake at Bentham Drive This site is located above the confluence of UT Falls Lake and the UT that receives the discharges from outfalls 2 and 3 from the Johnson WTP. This section of stream is very shallow (averaging 0.1 meter) and narrow (two meters). The watershed area at this point is only 0.98 square miles. Benthic substrate consisted mostly of sand (50%) and gravel (20%) with some rubble (10%) and silt (20%). The flow was low to moderate, but typical for this size of Figure 2• UT Falls Lake at Bentham Drive Piedmont stream in winter (Figure 2). As would be expected, flow was noticeably greater though in January 2006 than in August 2005. The water was clear, not slightly turbid as in August 2005. Riffles were infrequent. Sediment from eroding banks filled the channel. There was a high degree of embeddedness (50%) and a limited amount of in -stream habitat. Several residences bordering the stream have had the riparian vegetation removed or altered (western bank) allowing runoff to easily reach the stream. Alteration of the riparian zone may have contributed to the sedimentation problems seen at this site. A nearly complete canopy existed over most the stream and the riparian zone appeared generally healthy on the east bank. The specific conductance measured 91 µmhos/cm. UT Falls Lake at SR 2002 This sampling location is downstream of the discharges of Outfalls 2 and 3 from the Johnson WTP and is 1.5 miles downstream of the Bentham Drive site. The site at SR 2002 was deeper (averaging 0.3 meters), wider (three meters) and had increased flow 1 consistent with the larger drainage area of 1.35 square miles (and the additional flow from the WTP itself). This stream section contained a heterogeneous mix of benthic substrate, composed of rubble (20%), gravel (400/o), sand (30%), some silt (101/o) and a Figure 3: UT Falls Lake at SR 2002 trace of boulders. The banks appeared more stable here and riparian vegetation was healthy (Figure 3). Breaks in both the canopy and in the riparian vegetation were rare. A greater diversity of in -stream habitat was found here compared to the Bentham Drive site. Riffle areas were also more common here than upstream at Bentham Drive. The specific conductance measured 158 µmhos/cm. 2 METHODS Benthic Sampling The Qual4 method was used for the two samples collected in this investigation. This method is currently intended to compare small streams (drainage areas of <3 square miles) to one another and not intended to assign a bioclassification (i.e. water quality rating). Current DWQ assessment techniques do not permit assigning a bioclassification to Piedmont streams with a drainage area of < 3 square miles (other than Not Impaired or Not Rated). The Qual4 method is an abbreviated technique of the Standard Qualitative samples (i.e. Full Scale, which includes 10 composite samples). The Qual4 method composites one kick sample, one leafpack sample, one bank sweep and three visual surveys into a single sample. All organisms are removed from the sample in the field. When this site was sampled in 2002, another method, the Qual-5, was employed. This method is the same as the Qual4 but includes a log/rock wash in the composite sampling. The Qual-5 method is no longer is used by DWQ since data collected from this method are statistically similar to data from Qual4 collections. The purpose of these collections is to inventory the aquatic fauna and to determine the relative abundance for each taxon. Organisms were classified as Rare (1-2 specimens), Common (3-9 specimens), or Abundant (>10 specimens). Data -analysis summaries (metrics) are calculated from Qual-4 samples collected. These metrics are based on the principle that unstressed streams and rivers have many invertebrate taxa and are dominated by intolerant species. Conversely, polluted streams have fewer numbers of invertebrate taxa and are dominated by tolerant species. The diversity of the invertebrate fauna is evaluated using taxa richness counts; the tolerance of the stream community is evaluated using a biotic index. The EPT taxa richness (EPT S) is used to compare the two sampling locations in this study. "EPT" is an abbreviation for Ephemeroptera + Plecoptera + Trichoptera, insect groups that are generally intolerant of many kinds of pollution. Higher EPT taxa richness values usually indicate better water quality. Comparisons were made of the relative tolerance of the macroinvertebrate community as summarized by the North Carolina Biotic Index (NCBi) for the two sampling locations. Both tolerance values for individual species and the final biotic index values have a range of 0-10, with higher numbers indicating more tolerant species or more polluted conditions. EPT abundance (EPT N) and total taxa richness calculations also are used to help examine between -site differences in water quality. Typically, these water quality ratings (assigned with the biotic index numbers) are combined with EPT taxa richness ratings to produce a final bioclassification. In this case, however, only Not Rated or Not Impaired bioclassifications are permitted due to the small size of the watersheds (< 3 square miles). A Not Impaired rating is given if the stream would receive a bioclassification of Good -Fair or better using DWQ EPT criteria developed for larger streams. Small streams that would have a bioclassification of Fair or Poor continue to be Not Rated. For example, the two sampling locations in this study would need at least 14 EPT taxa to rate Not Impaired. Habitat Analysis Habitat assessments were performed at each sampling location using DWQ's Mountain/Piedmont Habitat Evaluation Form. This evaluation quantifies eight habitat metrics including four measures of in -stream habitat, one concerning streambank stability, two regarding the riparian zones, and an analysis of channel modification. The scores for each of the eight metrics are totaled, with a possible overall score of 100. C Habitat analyses are important when investigating aquatic communities as streams essentially flow through a terrestrial landscape. The physical features of a stream are largely influenced by geology and the areas immediately adjacent to the water body (i.e. riparian zone). Documentation of the habitat characteristics of a site can identify factors that could limit or enhance a stream's ability to support a diverse macroinvertebrate community. The habitat analysis also provides a baseline from which future changes in the physical conditions of the stream or riparian zone can be measured, since these changes can result in an altered macroinvertebrate assemblage in the stream. Physical -Chemical Field measurements were taken at the time of sampling for temperature, dissolved oxygen, conductivity, and pH using a YSI 85 meter and an Accumet pH meter. RESULTS and DISCUSSION Table 1: Data summary of benthic samples The January 2006 resampling of two sites on UT Falls Lake collected 51 total taxa; 42 taxa at Bentham Drive, the control site, and 16 taxa at SR 2002, the downstream location (Table 1). Habitat scores for both sites indicate some level of disturbance (65 at Bentham Drive, 76 at SR 2002) consistent with a suburban environment. Both sites were Not Rated. UT Falls Lake at Bentham Drive A total of 42 taxa including 12 EPT taxa were collected here in January 2006 (Table 1, Appendix A). This was the highest number of total taxa and EPT taxa found here during any of the three sampling efforts (Figures 4, 5). Abundant taxa found in January 2006 include the mayfly Stenonema modestum, the caddisfly Cheumatopsyche sp. and the damselfly Calopteryx sp.; all three were also abundant in the August 2005 collection. The seasonal chironomidae Sympotthastia sp., the crane fly Tipula sp. and the snail Micromenetus dilatus were also abundant in 2006. Twenty-three species were collected in January 2006 that had not been found at this site previously. Some of these taxa, such as the stonefly Allocapnia and the chironomidae Sympotthastia are seasonally collected species, but most were present due to the increase flow found here in winter as compared with summer when the previous two samples were taken. UT FALLS LAKE UT FALLS LAKE Bentham Drive SR 2002 1/20/2006 1/20/2006 Ephemeroptera 4 0 Plecoptera 2 0 Trichoptera 6 0 Coleoptera 5 1 Odonata 3 4 Megaloptera 0 0 Diptera: Chironomidae 11 2 Misc. Diptera 3 2 Ofigochaeta 1 3 Crustacea 2 2 Moilusca 3 2 Other 2 0 Total Taxa Richness 42 16 EPT Abundance 36 0 EPT Richness 12 0 Biotic Index 6.40 7.55 Bloclassit3cation Not Rated Not Rated Drainage area (sq mi.) 0.98 1.35 Habitat Score (of 100) 65 76 Width (m) 2 3 Depth (m) Average 0.1 0.3 Maximum 0.3 0.5 Canopy (%) 90 90 Aufwuchs none none Bank Erosion moderate low Substrate (°�) Boulder 0 trace Rubble 10 10 Gravel 50 50 Sand 20 30 Silt 20 10 Water Temp (°C) 8.1 9.0 Diss. Oxygen (mg/1) 12.0 11.9 Cond. (µmhos/cm) 91 156 pH 6.2 6.2 County WAKE WAKE Latitude 355455 355528 Longitude 783642 783614 The biotic index changed little among the three sampling dates (6.3 in 2002, 6.1 in 2005, and 6.4 in 2006; Figure 6), suggesting a stable, though somewhat pollution -tolerant, macroinvertebrate community at this site. 4 UT Falls Lake at SR 2002 Sixteen total taxa were collected here in January 2006, a decrease of 19 taxa from August 2005 (Figure 4), which was similar to 2002 when 17 total taxa were collected. None of the taxa collected in 2006 were abundant whereas in August 2005, five taxa were abundant. Extremely low densities of aquatic macroinvertebrates were observed here in 2006 (only 37 individual macroinvertebrates were collected in the sampling reach versus over 250 from the upstream location). The biotic index increased from 6.13 in August 2005 to 7.55 in January 2006, the highest biotic index recorded here. However, this is similar to the biotic index of the 2002 sample (7.4, Figure 6). The aquatic community at the SR 2002 site is one that is much more pollution tolerant than the community found there in August 2005. CONCLUSIONS Conditions downstream of Raleigh's Johnson WTP (on UT Falls Lake) have declined considerably in the past five months, and are similar to those seen in 2002. The remnant aquatic community found downstream of the Plant is less diverse, much less dense and more pollution tolerant than both the August 2005 sampling below the Plant, and to current conditions at an upstream control site. Cc: Susan Massengale Susan A. Wilson, NPDES Program Darlene Kucken, Planning Section Ken Schuster, RRO Figure 4: Total Taxa at two sites in UT Falls Lake (2002-2006). Figure 5: EPT Taxa at two sites in UT Falls Lake (2002-2006). 16 O Bentham Drive (upstream) ■SR 2002 (dovmstream) 10 x a � w 0 `m E 0 August2002 Au0ust2005 January 2006 Figure 6: Biotic Index at two sites in UT Falls Lake (2002-2006). ,6 s OBentham Drive (upstream) 6 ■SR 2002 (downsVeam) 7 x d a6 c 0 'm 2 , 6 Auguat2002 August2005 Jenuary2006 Taxon EPHEMEROPTERA BAETIS FLAVISTRIGA BAETIS PLUTO PSEUDOCLOEON PROPINQUUM CAENIS SPP CENTROPTILUM SPP EURYLOPHELLA SPP ISONYCHIA SPP STENONEMA MODESTUM STENACRONINTERPUNCTATUM PLECOPTERA ALLOCAPNIA SPP ECCOPTURA XANTHENES PERLIDAE TRICHOPTERA CHEUMATOPSYCHE SPP CHIMARRA SPP DIPLECTRONA MODESTA HYDROPSYCHE BETTENI IRONOQUTA PUNCTATISSIMA NEOPHYLAX CONSIMILIS OECETIS PERSIMILIS TRIAENODES SPP TRIAENODES IGNITUS COLEOPTERA ANCYRONYX VARIEGATUS DUBIRAPHIA SPP DUBIRAPHIA VITTATA HELICHUS SPP HELICHUS FASTIGIATUS HYDROPORUS SPP MACRONYCHUS GLABRATUS NEOPORUS SPP OULIMNIUS SPP PSEPHENUS HERRICKI ODONATA ARGIA SPP BOYERIA SPP BOYERIA VINOSA CALOPTERYX SPP CORDULEGASTER SPP DROMOGOMPHUS SPP ENALLAGMA SPP GOMPHUS SPP ISCHNURA SPP LIBELLULA SPP MACROMIA SPP PROGOMPHUS OBSCURUS STYLOGOMPHUS ALBISTYLUS MEGALOPTERA CORYDALUS CORNUTUS NIGRONIA SERRICORNIS DIPTERA: CHIRONOMIDAE ABLABESMYIA MALLOCHI CRICOTOPUS BICINCTUS CONCHAPELOPIA GROUP CORYNONEURA SPP DICROTENDIPES NEOMODESTUS Appendix A UT FALLS LAKE Bentham Or (upstream/control site) 8/29/2002 8/15/2005 1/20/2006 R - - - R - R R - C - - - - R - - R C A A - - R - - C - R R A A A R C R - R C - A C - - R R - - - - R A A R R - - A C R C - - A A R - - C R - R R R C - R - R A A - R - - R - - - R R - - R R R R C R - - R - R UT FALLS LAKE SR 2002 (downstream site) 8/29/2002 8/15/2005 1/2012006 A - C - R - A - R C R R R R R R R R A R R - R R R A C R C C R C C R A R R A R C R R R R R R C R R C Taxon (continued) EUKIEFFERIELLA BREHMI GR - EUKIEFFERIELLA BREVICALCAR GYMNOMETRIOCNEMUS SPP MICROTENDIPES SPP POLYPEDILUM FLAVUM POLYPEDILUM FALLAX POLYPEDILUM ILLINOENSE GR PARAMETRIOCNEMUS LUNDBECKI PARATANYTARSUS SPP PARATENDIPES SPP PHAENOPSECTRA FLAVIPES TRIBELOS JUCUNDUM PROCLADIUS SPP RHEOTANYTARSUS SPP SYMPOTTHASTIA SPP TRIBELOS SPP MISC. DIPTERA CHRYSOPS SPP DICRANOTA SPP EMPIDIDAE LIMONIA SPP MOLOPHILUS SPP SIMULIUM SPP TIPULA SPP HEMIPTERA LETHOCERUS SPP OLIGOCHAETA ENCHYTRAEIDAE LUMBRICULIDAE MEGADRILE OLIGOCHAETE STYLARIA LACUSTRIS CRUSTACEA CAECIDOTEA SPP (STREAMS) CAMBARUS (P.) HOBBSORUM CAMBARIDAE CAMBARUS SPP CRANGONYX SPP GASTROPODA FERRISSIA SPP MICROMENETUS DILATATUS PHYSELLA SPP PSEUDOSUCCINEA COLUMELLA OTHER HYDRACARINA Appendix A UT FALLS LAKE Bentham Dr (upstream/control site) 8/29/2002 8/15/2005 1/20/2006 - - R - - R - R - R - - - C - R - C C - - - - C - R - - R - R - C C - - - - R - - A R - - - - C R - - - - R R - A - - R C C C - R - - C R - C C - - R - - A R - R R - R R UT FALLS LAKE SR 2002 (downstream site) 8/29/2002 8/15/2005 1/20/2006 R - R - R R - R - - R - R R R R - R R C C C C C R C R R C R