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HomeMy WebLinkAbout20170359 Ver 2_NOV Response_20200819H z n Hazen and Sawyer a e 4011 WestChase Boulevard Suite 500 Raleigh, NC 27607 • 919.833.7152 August 21, 2020 Mr. Andrew Moore North Carolina Department of Environmental Quality Division of Water Resources Asheville Regional Office 2090 U.S. Highway 70 Swannanoa, NC 28778 Re: Response to NOV-2020-SS-0015 DWR Project No. 20170359 v2 Dear Mr. Moore: On August 5, 2020, the Division of Water Resources (DWR) issued a Notice of Violation (NOV) and recommendation for enforcement to Grandfather Golf and Country Club (GGCC) for violations of the stream standard for turbidity and the 401 water quality certification (WQC) conditions of the Loch Dornie dredging project. The NOV was issued based on observations during a July 30, 2020 site inspection by Andrew Moore, representing the Asheville Regional Office of DWR. GGCC hereby responds to the NOV and recommendation for enforcement. Explanation of the Turbidity Violation. GGCC believes the turbidity measured downstream of the Loch Dornie spillway on the 30th was the result of increased turbidity in the lake due to recent, large, and unanticipated rainfall events in the Linville River watershed. On July 22, 2020 GGCC accepted the Loch Dornie dredge work as substantially complete. Thereafter, the upper watershed bypass system was removed on July 23. At the time of removal, the lake was still drawn down approximately 8 feet below normal pool elevation, and all activities were complete below the normal pool elevation of the lake. The intent was to let the lake continue to serve as its own settling basin. It was expected to take two weeks or more for normal base flow and occasional thunderstorms to fill the lake. A significant rain event occurred on the afternoon of July 23 that dropped 2.5 inches of rain, which immediately flooded the lake. We do not have a reading of the turbidity of contributing runoff into the lake at that time. However, qualitatively, GGCC staff noted that the stormwater entering the lake from offsite and upstream of Station A was muddy. Additional storms followed, and 5.3 inches of rain were recorded from July 23 through July 26, including an additional 2.5 inches of rain in approximately one hour on July 26. After the intense storm event of July 26, the spillway was overflowing. GGCC partially opened the release valve on July 28. It was evident that the turbidity of flows from the valve were not improving downstream water quality and were more turbid than flows over the spillway. The valve was closed fully four hours later. Turbidity at Station B was 62 NTU on the morning of July 29. Another significant rain event occurred the afternoon hazenandsawyer.com Hazen Mr. Moore, DWR August 21, 2020 of July 29 (1.5 inches). Photos were taken of obviously turbid flows upstream of Station A (see attached photos). The next day, Andrew Moore conducted his site inspection and collected water samples. By the time of the site inspection, turbidity at Station A had dropped back down to 2.4 NTU's, but Station B below the dam had increased from 62 to 75 NTU's. GGCC representatives have historically observed muddy water in the upstream segments of the Linville River entering Loch Dornie via culverts conveying flows from offsite lands. Subsequent to Mr. Moore's site visit, GGCC has documented turbidity flows into Loch Dornie, and the August 12 measurements after 2.25-inch rainfall are indicative of the rainfall events leading up to July 30 (see attached chart). As can be seen, there were turbidity readings in excess of 200 NTUs in Linville River upstream of the Station A. The same storm event resulted in stormwater flows from the west side of Highway 105 that exceeded 300 NTUs prior to entering Loch Dornie. As the chart demonstrates, upstream waters appear to clear their sediment load and return to baseline turbidity levels within a matter of hours after the end of a rain event. Therefore, upstream turbidity measurements or observations that occur more than a few hours after the end of a rainfall do not reflect the turbidity during and immediately after storm conditions. The suspended sediment load from the portion of the watershed that is offsite and upstream of Loch Dornie collects in the lake, which acts a sink to protect downstream water quality. When the water surface elevation of Loch Dornie reaches or exceeds the spillway elevation, the turbid water flows freely over the spillway and on downstream in Linville River without the time necessary for settling having elapsed. While a portion of the sediment load probably does originate from the work just completed in Loch Dornie, it is also clear that a significant amount, if not the substantial majority, of sediment is transported to the lake via stormwater flows that originate offsite. 2. GGCC Corrective Actions. GGCC initiated corrective actions after discussions with Mr. Moore on July 30. Corrective actions include expediting preparation of the disturbed areas for seeding and sod installation, installation of silt fencing on the bare soil islands, and ordering a new turbidity curtain. By August 3, bare soils along the lake shore and islands were stabilized either by sodding or installing silt fence until sod or other stabilization could be established. A turbidity curtain was ordered by GGCC for placement above the spillway channel. Also, by August 3, turbidity at Station B had been reduced to 50 NTU (33 percent reduction). Over the course of the week, the Station B turbidity was reduced by half to 25 NTU on August 10. The turbidity curtain was delivered and installed on August 13, and the turbidity readings continue to decline, with a reading of 8.93 NTU's at station B on August 19. Moderate fluctuations and continued overall reductions in turbidity measurements at Station B suggest that the high turbidity peaks from repeated storm events are being absorbed by and settling in the lake. The lake is again protecting water quality in Linville River downstream of the lake. In addition, GGCC has measured significant turbid water contributions that are coming into the Linville River below the dam/Station B during storm events. This should be considered with respect to downstream (Linville) observations, complaints, and measurements. As an example, on August 8, Station B was recorded as 43.2 NTU while 128 NTU was recorded further downstream following a 2-inch rain event on August 7. Therefore, a significant portion of the flow and the turbidity in the Linville River at Page 2 of 3 hazenandsawyer.com Hazen Mr. Moore, DWR August 21, 2020 this location originates offsite below Station B and are conveyed via culverts under Highway 105 directly into the river. 3. Turbidity Measurements. Daily turbidity readings at station B have been reported to DWR since July 30. A summary of the readings from July 30 through August 19 is attached for reference. Daily readings will continue to be collected and reported until five days in a row are in compliance, as stated in the NOV letter. In summary, the events leading up to July 30, 2020 turbidity release over the Lake Dorme spillway were 1) unexpected and 2) substantially the result of sediment entering the Linville River upstream of Lake Dornie and not within the control of GGCC. However, GGCC has acted quickly in implementing measures trying to minimize future turbidity exceedences. If you have any questions, please reach out to Alan Shuping at (828) 898-4531, ext. 127 or by email at ashuping@grandfatherclubnc.com. Very truly yours, Keven Arrance Senior Principal Scientist cc: Amanda Jones — US Army Corps of Engineers Andrea Leslie — North Carolina Wildlife Resources Commission Stan Aiken — Division of Energy, Mineral and Land Resources Avery County Planning Alan Shuping — Grandfather Golf and Country Club Page 3 of 3 hazenandsawyer.com Daily Turbidity Log (2020) Grandfather Golf and Country Club Date I Station B I Leaving Property 31-Jul 68.8 46.1 1-Aug 65 2-Aug 55 38 3-Aug 50 35 4-Aug 46 34 5-Aug 39 27 6-Aug 36 24 7-Aug 33 23 8-Aug 31 22 9-Aug 29 17 10-Aug 25 15 11-Aug 22 14 12-Aug 18.9 12.7 13-Aug 20.9 11.7 14-Aug 20.9 10.5 15-Aug 19.2 9.3 16-Aug 17-Aug 13.3 9.75 18-Aug 11.4 7.23 19-Aug 8.93 5.4 * - No reading taken. Rainfall -Related Turbidity Readings Grandfather Golf and Country Club Date 8/12/2020 Rainfall Total 2.25 in Immediately After Rain Before Rain Downstream Property Boundary - 12.7 Station B 28.4 18.9 Station A 248 4.5 Upstream Property Boundary 229 - Hwy 105 Culvert Outlet 327 - GG&CC - 7/29 Rain Event Aju I 00 ft"., a9 F' Linville River crossing fwy 17 above lake Grassy Creek above lake �I •rr l k• L: trr , i !�"ti ;'3'�.4`t •ram ,� ` �' "� '�_ �,�r"!. GG&CC - 7/29 Rain Event Turbid flows above lake