SIMULATION OF CONTAMINATED SEDIMENT TRANSPORT IN WHITE OAK CREEK BASIN

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1 SMULATON OF CONTAMNATED SEDMENT TRANSPORT N WHTE OAK CREEK BASN Yixing Bao, Reearch Scientit, Roger B. Clapp, Reearch Scientit, and Antoinette L. Brenkert, Reearch Scientit, Environmental Science Diviion, Oak Ridge National Laboratory, Oak Ridge, Tenneee; Telena D. Mmre, Reearch Aociate, Department of Civil and Environmental Engineering, The Univerity of Tenneee, Knoxville, Tenneee; and Thoma A. Fontaine, Aitant Profeor, Department of Civil and Environmental Engineering, South Dakota School of Mine and Technology, Rapid City, South Dakota Abtract. Thi paper preent a ytematic approach to management of the contaminated ediment in the White Oak Creek waterhed at Oak Ridge National Laboratory near Oak Ridge, Tenneee. The primary contaminant of concern i radioactive ceium-37 (3 C), which bind to oil and ediment particle. The key component in the approach include an intenive ampling and monitoring ytem for flood event; modeling of hydrological procee, ediment tranport, and contaminant flux movement; and a deciion framework with a detailed human health rik analyi. Emphai i placed on modeling of waterhed rainfall-runoff and contaminated ediment tranport during flooding period uing the Hydrologic Simulation Program-Fortran (HSPF) model. Becaue a large number of parameter are required in HSPF modeling, the major effort in the modeling proce i the calibration of model parameter to make imulation reult and meaured value agree a cloely a poible. An optimization model incorporating the concept of an expert ytem wa developed to improve calibration reult and efficiency. Over a five-year imulation period, the imulated flow match the oberved value well. Simulated total amount of ediment load at variou location during torm match with the oberved value within a factor of.5. Simulated annual releae of 37Coff-ite location match the data within a factor of 2 for the five-year period. The comprehenive modeling approach can provide a valuable tool for deciion maker to quantitatively analyze ediment eroion, depoition, and tranport; expoure rik related to radionuclide in contaminated ediment; and variou management trategie. NTRODUCTON Backmound. The U.S. Department of Energy Oak Ridge National Laboratory (ORNL) i located in the White Oak Creek bain near Oak Ridge, Tenneee. Over a period of 50 year, the operation of and wate dipoal activitie at ORNL have reulted in an accumulation of 3 C and other radionuclide contaminant that are bound to ediment ditributed in the White Oak Creek bain. The contaminated ediment are primarily located along the floodplain and in White Oak Lake near the bain outlet (Clapp et al. 994 and Oake et al. 982). To ae the long-term potential rik to human population downtream of White Oak Creek becaue of expoure to 37 C from local flood event, a predictive model i critically important for imulating contaminated-ediment eroion, depoition, and tranport in the White Oak Creek bain. The model i a key component within an overall rik aement ytem, hown in Figure. Currently, available information ugget that no appreciable off-ite rik exit, but the effect of extreme flood mut be etimated and documented. Furthermore, management option (e.g., leaving the contaminated ediment a they are, tabilizing tream bank and the lake bed, building ediment-the - wkruned m a a p t ha authored by a contractq of u Govwmant uda contract No DEAC05-&uwZ400 AcCaanlv. the u

2 Monitoring and Data Collection Modeling L HSPFHydrologic Modeling to imulate tream flow Bain Characteritic Survey Channel and White Oak Lake bathymetry, Soil propertie and ediment compoition, Meteorological data, Monitoring Stream flow, Supended ediment [], and 37C Contaminant Monitoring Waterhed contaminant inventory, Change in channel bed 3 profile, Bed ediment core, and Contaminant concentration Precipitation, Evaporation, and Temperature m i a t i o n and Management )eciion Calibration & Validation to match oberved tream-flow by adjuting parameter uch a: Lower zone torage, nfiltrationcapacity, Groundwater receion rate, Upper zone torage, nterflow parameter, nterflow receion parameter, Lower zone ET parameter, nterception torage capacity, & Baeflow potential ET. Precipitation and Stream Storm Sampling t Generation of Time Serie ' Off-ite Tranport - HEC-6 to imulate patial and temporal C concentration Sediment Tranport HSPF to imulate ediment load, upended ediment concentration and bed elevation Prediction for future ediment and contaminant tranport under extreme flood condition Waterhed eroion parameter, Critical hear tree, and Sand tranport parameter. T Calibration, B Contaminant concentrationon upended and channel bed material Figure. Flowchart of Contaminated Sediment Tranport Modeling and Expoure Rik Aement i

3 retention check dam) mut be aeed. Poible change in the waterhed from future development mut alo be aeed. However, the management iue and rik aement are beyond the cope of thi paper. Punme. The purpoe of thi paper i to decribe the waterhed model ued in the project and an advancement in model calibration that we developed. Thi paper pertain to the modeling component that are hown in the bold boxe in Figure. Other part of the project are intenive torm ampling, eroion tudie, and rik-aement modeling. METHOD A comprehenive, continuou waterhed model, Hydrologic Simulation Program-Fortran (HSPF) (Bicknell et al. 993), wa applied to the White Oak Creek bain to imulate variou hydrological procee, ediment tranport, and the movement of 3 C. The imulated tream flow and contaminant releae at White Oak Dam from HSPF are input to HEC-6 (Hydrologic Engineering Center 993) for imulation of off-ite contaminated ediment tranport in the Clinch River a place where the public can be expoed to water and ediment. We have modified HEC-6to account for variable contamination layer in the ediment in tream channel. A rik aement model ue HEC-6 output information of contaminant concentration to ae long-term human expoure rik. Bain Decrintion. The White Oak Creek bain area i about 6 km2 (Figure2) with 80% foret, 0% riparian, and 0% developed area uch a building, road, and parking lot. Slope of the primary channel i in a range from /000 to 4/000. Average annual precipitation i 37 cm. Rainfall data were collected from ix rain gauge within or near the boundary of White Oak Creek bain. Phvical Reoreentation n the HSPF modeling approach, a land egment i a ubdiviion of the waterhed, and reache or reervoir link the land egment together (Bicknell et al. 993). A hown in Figure 2 and 3, White Oak Creek bain i repreented by four perviou land egment (PLS to PLS4) that are connected through even channel reache (reache 2 to 8). The drainage area, channel reach length, location of the end of reach, and tream-flow gage tation correponding to each PLS are lited in Table. New ADDroach to Hvdrolopic Calibration. The purpoe of hydrologic model calibration i to adjut model parameter in a ytematic fahion o that computed and oberved value (e.g., water urface elevation, total flow rate, velocitie) agree a cloely a poible. A large number of parameter are required in the HSPF model; thu, calibration i a key component in the modeling procee. A calibration methodology wa developed by combining an expert ytem and a nonlinear-optimization model. The expert ytem incorporate calibration trategie (Donigian et al. 984) with direct obervation of the waterhed hydrologic behavior (Oake et al. 982) and determine the equence in which to calibrate parameter. The nonlinearoptimization model (Ladon and Waren 989) determine the value of the parameter by minimizing the abolute difference between the computed and oberved tream flow at the outlet of each perviou land egment. The fut three-year period of a five-year record of flow wa ued

4 for model calibration and the lat two year of data were ued for model validation (without changing in model parameter for validation run). Each ubcatchment (i.e., PLS) wa calibrated independently..e$ Mctm 000 Figure 2. White Oak Creek Waterhed Map and Rain Gauge with Theien Polygon for Etimation of Rainfall Ditribution R# =Reachnumber PLSl PLS = Perviou Land Segment... *. R6 R5 R Bridge -* Figure 3. Schematic Sketch of the Model Element Repreenting White Oak Creek Waterhed Calibration Strategv for Sediment TranDort model in^. A three-tep approach wa taken for calibrating the contaminated-ediment tranport model. Firt, the model wa calibrated to match

5 the ediment concentration and load at each reach with data collected during five torm. The primary calibration paiameter ued are coefficient in a waterhed gully eroion equation; coefficient in and tranport equation; and critical hear tree for ilt and clay. Next, the imulated change in channel depth were compared with the meaured channel cro-ectional profile to determine the change in ediment depoition and reupenion at a particular reach; thi led to refinement in the critical hear tree for clay and ilt, channel grain ize, and ediment compoition. Third, the contaminant releae from the bain wa calibrated by adjuting potency factor for contaminant concentration on upended and channel bed. Table. Perviou Land Segment and ChanneYLake Reache for White Oak Creek Waterhed WOC Lake WOD RESULTS Overall, the imulated flow match the oberved value for a five-year imulation period well. Figure 4 how an example of the flow imulation reult at the White Oak Dam. The average difference in annual water balance between the imulated and oberved value i 2.08%. The preliminary calibration reult at preent indicate that () the imulated total amount of ediment load at variou location match the oberved value within a factor of.5 for five torm that occurred in (2) the pattern of imulated channel bed (cro-ectional profile) change due to depoition andor eroion doe not match the oberved data at ome location. (3) the imulated annual releae of 3 C to off-ite location match data within a factor of 2 for CONCLUSONS The comprehenive modeling approach can provide a valuable tool for deciion maker to quantitatively analyze () ediment eroion, depoition, and tranport; (2) expoure rik related to radionuclide in contaminated ediment; and (3) variou management trategie. Thi approach to modeling can, for example, ait engineer and manager wherever indutrie have left a legacy of widepread contaminated ediment.

6 400 UJ rc i i 250 U & E a =. 8 EET Simulated t F 5 z 5 Day tart from // ; 6 F2 ; ~$ ~ Figure 4. Simulated v. Oberved Flow at White Oak Creek Dam REFERENCES Bicknell, B.R., J.C. mhoff, J.L. Kittle, Jr., A.S. Donigian, Jr., and R.C. Johanon, 993, Hydrological Simulation Program - FORTRAN Uer Manual for Releae 0. EPA/600/R-93/74. Environmental Reearch Laboratory, oftice of Reearch and Development, U.S. Environmental Protection Agency, Athen, Georgia. Clapp, R.B., J.A. Watt, and M.A.S. Guth, (ed.),994, Third Annual Environmental Retoration Monitoring and Aement Report for FY 994 of the Oak Ridge National Laboratory. DOE/OR/Ol290&D and ORNLER-250. Oak Ridge National Laboratory, Oak Ridge, Tenneee. Donigian, AS., Jr., J.C. mhoff, B.R. Bichnell, and J.L. Kittle, Jr., 984, Application Guide for Hydrological Simulation Program- FORTRAN (HSPF). EPA-600/ Environmental Reearch Laboratory, Office of Reearch and Development, U.S. Environmental Protection Agency, Athen, Georgia. Hydrologic Engineering Center, 993, HEC-6: Scour and Depoition in River and Reervoir- Uer Manual. U.S. Army Corp of Engineer, HEC. Ladon, L.S. and A.D. Waren, 989, GRG2 Uer Guide. Department of General Buine, The Univerity of Texa, Autin, Texa. Oake, T.W., B.A. Kelly, W.F. Ohneorge, J.S., Eldridge, J.C. Bird, CE. Shank, and F.S. Fakere, 982, Technical Background nformation for the Environmental and Safety Report, Vol. 4: White Oak Lake and Dam. ORNL-568. Oak Ridge National Laboratory, Oak Ridge, Tenneee. ACKNOWLEDGMENTS The reearch wa ponored by the office of Environmental Retoration and Wate Management, U.S. Department of Energy, under contract DE-AC05-840R2400with Lockheed Martin Energy Sytem, nc. 7

7 DSCLAMER Thi report wa prepared a an account of work ponored by an agency of the United State Government. Neither the United State Government nor any agency thzreof, nor any of their employee, make any warranty, expre or implied, or aume any legal liability or reponibility for the accuracy, completene, or uefulne of any information. apparatu, product, or proce dicloe$, or repreent that it ue would not mfringe privately owned right. Reference herein to any pecific commercial product, proce, or ervice by trade name, trademark, manufacturer, or otherwie doe not necearily contitute or imply it endorement, recommendation, or favoring by the United State Government or any agency thereof. The view and opinion of author expreed herein do not necearily tate or reflect thoe of the United State Government or any agency thereof.