Project Water Quality

Transcription

1 Project Water Quality Yadkin-Pee Dee Hydroelectric Project No Water Resources Working Group May 7, 2003

2 Surveys of Existing Resources! Reservoirs (monthly sampling) " Lake Tillery (2000, 2002) " Blewett Falls Lake (1999, 2001)! Tailwaters (monthly sampling) " Tillery Dam to Blewett Falls Lake (1999, 2000, 2002) " Blewett Falls Dam to Johnsonville,SC (1999, 2001)! Special surveys " Onset TIDBIT continuous temperature data # Highway 109 and Highway 74 Bridges ( ) # Tillery Dam to Johnsonville, SC (January-August 2002) " Biweekly water quality surveys of tailwaters (migratory fish surveys)! Historical surveys " Lake Tillery and tailwaters (1992) " Blewett Falls Lake and tailwaters (1993)

3 Lake Tillery D2 B2 F2 K2 Morrow Mountain State Park Falls Dam Pee Dee Power Plant N H2 Hwy Hwy 24/27 Kilometers Uwharrie Miles

4 Lake Tillery Characteristics! Mesotrophic Lake (moderate biological productivity with good water clarity). " Moderate nutrient and solids concentrations. " NCDWQ Classification WS-IV & B CA Drinking Water Supplies. # Montgomery County and City of Norwood.! Fully supporting NCDWQ designated uses. " DO levels were always above N.C. water quality standard of 5 ppm. in surface waters throughout the lake during surveys. " No water quality problems noted. " Some spatial patterns were noted for solids, nutrients, and turbidity.! Lake dynamics influenced by inflows and outflows, hydraulic retention time is 8.3 days.

5 NC 731 Pee Dee below Tillery Hydroelectric Plant Lake Tillery Creek Clarks 1B Plant Power RR N Kilometers Miles US 52 Rocky Pee Dee National Wildlife Refuge Pee Dee NC B

6 Pee Dee Characteristics Reach from Tillery Plant to Blewett Falls Lake! Water quality in this river reach influenced by Rocky inflows below confluence " Solids, nutrient, ions, hardness, and COD loading from Rocky. " Turbidity levels can exceed N.C. water quality standard of 50 NTU below Rocky confluence after storm events. " Copper loading source in Rocky watershed.! Temperature and dissolved oxygen (DO) regime influenced by Tillery hypolimnetic discharge, particularly during summer. " Occasional DO concentrations below N.C. water quality standard of 5.0 mg/l in summer months with plant startup. " Temperature difference of 1-2 C from tailwaters to Highway 109 Bridge.! NCDWQ Water Classification is WS-V & B and partially supporting designated uses: " Low DO levels below the power plant (Tillery Dam to mouth of Turkey Top Creek including Blewett Falls Lake). " ph fluctuations from agriculture (Turkey Top Creek to Savannah Creek).

7 Pee Dee Tailwaters Temperature Regime-Jan-Aug 2002 Mean Water Temperatures o C Johnsonville, SC Florence, SC Society Hill, SC Cheraw,SC Highway 74 Blewett tailrace Highway 109 Tillery tailrace Location

8 Blewett Falls Reservoir SR 1748 US 74 Blewett Hydroelectric Plant Pee Dee B Kilometers Miles F2 N NC B Pee Dee H2 Little

9 Blewett Falls Characteristics! Shallow, eutrophic lake (high biological productivity with turbid water). " Elevated nutrients and solids, owing to inputs from Rocky. " Occasional elevated chlorophyll a, DO concentrations, and ph levels from algae blooms in summer. " Short hydraulic retention time influences intensity and duration of algal blooms and temperature/do stratification patterns.! NCDWQ Classification WS-IV & B Drinking Water Supplies. # Stanly and Richmond counties.! Fully supporting NCDWQ designated uses.! Lake water quality is relatively homogeneous due to shallow depth and short hydraulic retention time of 1.9 days. " Total nitrogen and nitrate+nitrite-n were greater in reservoir headwaters. " Chlorophyll a concentrations exhibited a converse spatial pattern.

10 Black Black Pee Dee, NC-SC South Carolina North Carolina Blewett Falls Lake Little Pee Dee Winyah Bay Atlantic Ocean Lynches Transect 5 Transect 2 Transect 3 Transect 1 Transect 4 W accam aw Miles Johnsonville Georgetown N SC 15/401 Cheraw Society Hill Florence US 1 US 76/301 US 74 SC SC W accam aw

11 Pee Dee Characteristics Reach below Blewett Plant! Water quality closely resembled Blewett Falls characteristics in immediate tailwaters.! With increasing distance from the power plant, water quality was more related to physiographic region, watershed inflow, natural inputs of organic matter, and point/nonpoint discharges. " Waters near neutral to slightly acidic, moderately soft with low buffering capacity. Ions, specific conductance, and TOC increased in Coastal Plain region. " Nutrients and solids increased significantly with distance downstream.! NCDWQ listed N.C. reach as support threatened for designated use due to low DO levels in summer. " DO levels below 5 ppm were recorded at Highway 74 Bridge on two occasions during summers of 1999 and 2000 ( mg/l). " Exact distance of affected area unknown, but most likely re-aerated in shoal areas just downstream of the bridge; no low DO levels were noted at US 1 Bridge at Cheraw, SC. " Naturally occurring DO sags were noted in 1998 with draining of swamp waters in Coastal Plain region after El Nino event.! Sources of impairment in S.C. waters were elevated fecal coliform and copper and low DO levels.