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Home My WebLink AboutNC0063096_Meeting Notes_20080821NPDES DOCUNENT SCANNING COVER SHEET NPDES Permit: NC0063096 Holly Springs WWTP Document Type: Permit Issuance Wasteload Allocation Authorization to Construct (AtC) Permit Modification Complete File - Historical Engineering Alternatives (EAA) Correspondence Owner Name Change Meeting Notes Instream Assessment (67b) Speculative Limits Environmental Assessment (EA) Document Date: August 21, 2008 Vies docurnerit is printed on reuse paper - igm.ore any content on tine reYerese'side Meeting to Discuss Harris Lake Modeling and Monitoring August 21, 2008 @ 2:30-4:00 PM Archdale Building,14th Floor, Conference Room No. 3 1. Introduction and Purpose of the Meeting 2. Model development process 3. Overview of model calibration 4. Preliminary results of discharge sensitivity 5. Information to present to EMC Water Allocation Committee in September 6. Discussion/Next Steps Modeling Review Meeting Western Wake Regional Wastewater Management Facilities Harris Lake Model Update lu;ust 21, 200$ Review Topics ♦ Model development process ♦ Calibration Status ♦ Preliminary results for discharge sensitivity ♦ Information to present EMC Water Allocation Committee in September ♦ Discussion/Next Steps Review Topics ♦ Model development process ♦ Calibration Status ♦ Preliminary results for discharge sensitivity ♦ Information to present EMC Water Allocation Committee in September ♦ Discussion/Next Steps 1 Overall Modeling Process • Modeling approach- Complete • Modification of monitoring program - Complete • Development of watershed and lake models - Complete • Screening with BathTuh model — Complete • Model Calibration - 2ntl Draft Complete • Draft TM submitted — DWQ review meeting August 11 • Comments received on August 19 • Model Sensitivity to Discharge - July -August 08 • Preliminary model report - August -Sep 08 • EMC Update on Harris Lake - Sep 08 • 2008 Monitoring data available - Nov 08 • Updated model analyses and reports - Jan 09 Model Development • Preliminary Scenario Analysis based on BatliTub • Watershed Model • Adapted Utley Creek Generalized Watershed Loading Function (GWLF) model to estimate nonpoint source loading to Harris Lake • CE-DUAL-W2 Model of the Lake • Based on Jan. 08 detailed bathymetric data • Divided lake into segments with similar characteristics • Processed GWLF and point source nutrient loadings for the period from 2001 - 2007 • Doveloped meteorological inputs based local Progross data 2 Review Topics • Model development process • Calibration Status • Preliminary results for discharge sensitivity • Information to present EMC Water Allocation Committee in September • Discussion/Next Steps Se16 /{( PisU f- 3 Lake Model Calibration Steps • Check flow balance • Calibrate temperature to profiles • Evaluate balance of organic and inorganic nitrogen species (TKN, NH4, NO3) • Calibrate total nitrogen and total phosphorus • Calibrate chlorophyll a • Calibrate dissolved oxygen to profiles Calibration Status • Preliminary Calibration Completed • Based on Quarterly data at 4 stations - Used 2006 for calibration 8 2007 for verification Examined predictions versus results for 2002 through 2007 • Draft TM submitted to Partners and DWQ • Review meeting held on August 11 • Comments received on August 19 • Next Steps • Address comments • Complete preliminary discharge sensitivity analysis • Update model based on 2008 monitoring - 2 additional stations - Increased collection frequency Harris Lake Monitoring Locations 'r�- tticv 5 i nv ro 4 Calibration Observations • NPS Nitrogen species are underestimated • Not critical because TN/TP ratios high • Focused on NPS TP • Temperature and DO predictions are generally very good • Chlorophyll a simulation captures range and expected pattern of algal growth • Underestimates levels during non -growing season • Can be refined using temperature parameters Review Topics • Model development process • Calibration Status • Preliminary results for discharge sensitivity • Information to present EMC Water Allocation Committee in September • Discussion/Next Steps Evaluation of Potential Scenarios • Baseline - existing conditions • Phase 1 - Initial WRF discharge • 220' lake elevation • Western Wake WRF discharge rate of 18 mgd • HS discharge rate of G mgd • Existing Landuse • Combined discharge and separate discharge • Phase 2 - Long term WRF discharge • 220' and 240' lake elevation • WRF discharge rate of 30 mgd • HS discharge rate of 8 mgd • Future Landuse with BMPs 5 Comparison of chlorophyll a concentrations above the Main Dam a? 220' Baseline and 24 mgd at 2 mg1L TP Comparison of WRF $c.nYba al la mad ■ICI i','1■Irl I. Comparison of chlorophyll a concentrations above the Main Dam E; 220' Baseline and 24 mgd at 2 & 0.5 mg/L TP Commie. of WRF MonWpa M 7A mei Comparison of chlorophyll a concentrations above the Main Dam @ 220' Baseline and 24 mgd at 2, 0.5, & 0.25 mg/L TP CanpeYena1WRF Scenario* at 24 aqd —WNW—+..••.f. —.aM•a. n'—..w..n' • ■•1I■11M111111•41■IY1',11 ■YI■'i�■��,■WI■il'I■i'� ■■I■EMIIIIIMS j.111111M1 �, 7i�1,�■,111t1■y��kl�l�ttt� ni riletf,loy - (4- s .„1(L bkit 6 Comparison of chlorophyll a concentrations above the Main Dam `d 220' Baseline and24 mgd at 2, 0.5, 0.25, & 0,1 mg/L TP Comparison of chlorophyll a concentrations at discharge location « 220' Baseline and,24 mgd at 2, 0.5, 0.25, & 0.1 mg/L TP 0V'—awM.vv Comparison of chlorophyll a Concentrations in Utley Creek Combined Discharge vs Separate WRF and Holly Springs Discharge 5U w m Co..,Mn. OW. a.. WPM On„ar,m — :a.ca oossr> — ,a.s.@oasrw,e - uow E. ,111=111MIIN 10 b. ( ,tti (d62. 7 Dynamic Simulation of Chlorophyll a 24 mgd Combined Discharge at 2 mg/L TP MI 140.261• i' i Dynamic Simulation of Chlorophyll a 18 mgd WW Discharge Plus 6 mgd Holly Springs at 2 mgiL TP Comparison of Current and Future Landuse Baseline Results at the Main Dam Comparison of Existing and Foto . Bastogne NI • — Cupp — ru..erpp,e,n 8 Comparison of Current and Future Landuse Baseline Results in the Utley Creek Arm Lerrplemd 6f10y.116n �J+Rrb IYrygrW Ann Eislrp — f RanroW BAN — rJn ennenowtsH t 5 as • f u w II I,rl1 . IT= All 'W I I it Comparison of chlorophyll a concentrations above the Main Dam rah 220' Baseline and 38 mgd at 2. 0.5, 0.25, & 0.1 mg/L TP Comparison of chlorophyll a concentrations at Discharge Location @ 220' Baseline and 38 mgd at 2, 0.5, 0.25, & 0.1 mg/L TP 9 Comparison of chlorophyll a concentrations at 220' and 240' Elevation Above the Main Dam Baseline and, 38 mgd discharge @ 0.25 mg/L TP Comparison of la mad WRr wnvIo. n 220' an xis' LY. L.v.l 240' Lake Level Caveats • Current 240' Lake Level Run Assumptions • Future urban landuse meets Jordan Lake rules for TP - Stormwator controls on new development - Prirnadly impacts high densely development and commerclil landusos - Reduces NPS TP loading by approximately 10% • No assumption for Increase In cooling water discharge volume - Expansion of the nuclear plant would Include a higher discharge volume - Plant currently uses polyorlhophosphato for anticorrosion measures • No additional changes in water balance - Minimum release from darn not Included - Pumping from Cape Fear River not Included Prelijninary Conclusions from Scenarios • Exceedances of chlorophyll a standard likely at discharge TP concentrations above 0.25 mg!L • Removal of Holly Springs WWTP from Utley Creek provides little benefit to Harris Lake • Model includes TP removal in Thomas Millpond 10 Preliminary Conclusions (Continued) ♦ Increase to 38 mgd has minimal impact at the 0.25 mg/L TP level • Increased flushing and reduced residence time outweighs higher TP load ♦ Higher lake level (240 elevation) provides significant buffering capacity • Scenario assumes NPS controls and no increase in TP from cooling water Review Topics ♦ Model development process ♦ Calibration Status ♦ Preliminary results for discharge sensitivity ♦ Information to present EMC Water Allocation Committee in September ♦ Discussion/Next Steps Topics for EMC Discussion ♦ Status of modeling • Brief highlights of earlier slides • Preliminary sensitivity • Schedule ♦ Potential IBT related issues • Downstream concerns (moving discharge from CF River) • Impacts on WRF Schedule 11 Comparison of Discharge from the Harris Lake Main Dam under sting and WRF Scenarios Sao 453 403 350 303 353 1m IEo Com y.rlon of M.In D. m e1rhmIgo — Etlbp oWwlal — 14 5030S lal —Hmpe PYe.lal — 34 0I25..3104w1 Iii -'_ •iimulmium AmtRwitil=N ■;t"m MiWitANtigaii Mlle= as Lake Outflow Predictions Flow Existing Information Outflow Aluage Flow for 2001• 2007 - ds I019d1 32.0 (20.6] Average Summer Flow for 2001.2007 - ds (nrgdJ 12.7 (8.2] Median Summer Flow for 2001-2007 - ds (mgd) 1.4 (0.9] Total Days below 7010 [2001.2007) 406 I'.... r. r 1. .. ..l Outflow with 24 mgd WRF 68.6 (43.0] 35.9123.1] 26.8 (17.3] 45 Outflow with 38 mgd WRF 87.2 [56.3) 55.0[35.51 46.2 (29.81 Outflow with 38 mgd WRF - 240' 75.3148.61 34.4 (22.2] 29.0 (18.7) 0 Review Topics • Model development process • Calibration Status • Preliminary results For discharge sensitivity • Information to present EMC Water Allocation Committee in September • Discussion/Next Steps 12