Analysis of a Partial Blowout in the Leadville Mine Drainage Tunnel, Leadville, CO. Brianna Svoboda Colorado School of Mines 4/24/14

Transcription

1 Analysis of a Partial Blowout in the Leadville Mine Drainage Tunnel, Leadville, CO Brianna Svoboda Colorado School of Mines 4/24/14

2 1.0 Introduction The United States Bureau of Reclamation requested a study to evaluate the effects of a partial failure of the Leadville Mine Drainage Tunnel (LMDT) that would release increased concentrations of zinc into the Arkansas River. The drainage tunnel is approximately two miles long and connects with the East Fork of the Arkansas River (US Department of the Interior Bureau of Reclamation, 2008) (refer to Figure 1). The blockage of interest, where partial failure may occur, is located near the Pendery Fault (refer to Figure 2). The tunnel likely experienced roof collapse near the faulted area creating the blockage (Wireman et al., 2006). A partial failure of the blocked area has several factors of uncertainty, including the unknown dimensions of the failure area. Other factors of uncertainty include the volume of water behind the blockage, the flow rates through the tunnel, and the depth and velocity of the Arkansas River when the partial blowout occurs. To help reduce the uncertainties of a partial failure the acknowledged uncertainties were evaluated and the zinc contamination of the Arkansas River was modeled. The scope of work performed to evaluate the effects of a partial blowout of the LMDT included the following: 1. Estimated the volume of contaminated water held behind and above the tunnel blockage 2. Estimated the flow rates and time durations it takes for the water to move through the tunnel 3. Analyzed the transport of zinc contamination at three downstream locations including determining the time and distance that the concentration levels will be toxic to fish in the area The input parameters of the model and the model results are discussed along with a brief error assessment. Recommendations for the future and conclusions based on the effects of a partial failure of the LMDT are made regarding the impact of elevated zinc concentrations in the Arkansas River on the local fish population. 2.0 Methods 2.1 Literature Review of Previous Work A review of the following documents of prior studies completed on the LMDT and evaluation of potential failures was completed before developing a model to evaluate the impact of elevated zinc concentrations in the Arkansas River: 1. Reclamation- Managing Water in the West by the US Department of the Interior Bureau of Reclamation, Leadville Mine Drainage Tunnel Overview by the US Department of the Interior Bureau of Reclamation, Colorado Streamflows by All About Rivers Staff, Manning s n Value by Chow, Hydrogeologic Characterization of Ground Waters, Mine Pools, and the Leadville Mine Drainage Tunnel, Leadville, CO by Wireman et al., Hydrogeologic Setting and Simulation of Ground Water Flow near the Canterbury and Leadville Mine Drainage Tunnels, Leadville, CO by Wellman et al., Leadville, CO Mine Drainage Response by the Environmental Protection Agency, EPA Letter to Energy Commerce by Biley, Final Leadville Mine Drainage Tunnel Risk Assessment Review Memo by Bailey, 2008

3 2.2 Model Development The model development was motivated by the need to reduce uncertainties surrounding the parameters and effects of a partial tunnel blowout. The model was also motivated by the need to evaluate the movement of the zinc contamination plume downstream from the LMDT to determine the impact of elevated zinc concentrations on the local fish populations in the Arkansas River. To better define the parameters surrounding the partial blowout, the literature review offered information and values from previous studies on the LMDT. Values were obtained for the diameter of the tunnel, volume of mine drainage water, Manning s n number, friction factor in the tunnel, length of the blowout, and initial head behind the blocked area (refer to Table 1 for parameter inputs). A range of zinc concentrations and discharge in the Arkansas River were also obtained (refer to Table 1). Using the estimated input parameters, a model was developed using the Mathcad15 software to evaluate the tunnel blowout discharge through time. The depth and velocity of the Arkansas River after the blowout were also determined. After defining some of the partial blowout uncertainties, a Monte Carlo simulation (randomized input parameters to address remaining parameter uncertainties) was performed to assess contamination levels and error bounds of the zinc contamination plume in the Arkansas River on the fish population. In order to analyze contamination levels, a convolution was performed. A convolution is a method where the contamination source was modeled as additive unit impulses through time that were altered by the river using the Green s function (Benson, 2014). The unit impulses were from a continuous source and represented additive advection- disperison equations summed at different time shifts to produce the continuous signal (Benson, 2014). Error bounds were modeled to further address the remaining uncertainties in the parameter inputs by determining plus or minus one standard deviation from the mean contamination levels produced by the Monte Carlo simulation.

4 Table 1. Parameter Inputs Parameter Estimated Initial Input Value Information used to Estimate Parameter Input Value Partial Failure 5 ft. Tunnel opening ranges from 7.5 ft. to 8 ft. Dimensions: wide and 8 ft. to 11 ft. tall (US Department of Diameter the Interior Bureau of Reclamation, 2008) If only partial failure of the opening is assumed, then 5ft wide is an approximate average width for the diameter of the tunnel (this value is variable) Partial Failure Dimensions: Length 200 ft. Assumed 200ft of failure length for modeling (this value may be larger or smaller than the estimated 200ft) Friction in Tunnel 0.20 The LMDT is a rough tunnel (value obtained from the Moody Diagram) (Elger et al., 2013) (refer to Figure 3) Initial Hydraulic Head behind the blockage Volume of Water behind the blockage Zinc Concentrations in Discharged Water 119 ft. Variations in reported hydraulic heads behind the blockage (Bailey, 2008) Hydraulic head values range from 119 ft. to 163 ft. (Bailey, 2008 and Wellman et. al, 2011) Other estimations of hydraulic head values are 150 ft. (Biley, 2008) 1.5 billion gallons 2.68 ppm 11.9 ppm EPA estimated the volume of mine pool water above the LMDT to range between 0.54 to 1.47 billion gallons (Wireman et al., 2006) Dissolved zinc concentrations range from approximately 2.68 to 11.9 ppm in discharged water (Wireman et al., 2006) Manning s n Value 0.05 Manning s number is based on the information that the Arkansas River is a mountain stream, which is a mixture of gravel, cobble, and boulders (Chow, 1959) Slope 0.01 Using measured dimension of the change in elevation and the length of the Arkansas River between Leadville and Buena Vista, the slope of the Arkansas River was estimated Measurements and elevations were obtained using Google Earth Discharge of Arkansas River Spring: 856 cfs Summer: 503 cfs Discharge obtained from USGS gauge # ARKANSAS RIVER BELOW GRANITE, CO Used average monthly values to find a mean value for spring and summer flow rates near Granite, CO for the Arkansas River Dispersion 400 ft/s The dispersion value is not realistic for the system and was chosen based on the need to create smoother graphical curves for the model output Assumptions Assumed a general circular failure of the blowout area to estimate the diameter of the blowout Unknown length of blocked area, so assumed a partial failure length Pipe- flow assumption: Used the Darcy and Weisbach method for assessing head loss due to friction through the tunnel (Elger et al., 2013) The most commonly referenced hydraulic head value is 119 ft., so this value was used for modeling (Bailey, 2008) Assumed a high and low concentration value to evaluate the range of possible zinc concentrations in the Arkansas River Flow in the Arkansas varies greatly with elevation and season (McCord, 2003)

5 3.0 Results 3.1 Estimation of the Volume of Water held behind the Tunnel Blockage The EPA estimated the volume of mine pool water above the LMDT to range between 0.54 to 1.47 billion gallons (Wireman et al., 2006). To evaluate the worst case scenario, a mine drainage volume of 1.5 billion gallons was used in the model. 3.2 Estimation of the discharge of the blowout and time duration of the water through the tunnel The discharge of the blowout was estimated to be 190 cubic feet per day (refer to Figure 4). With an initial head of 119 ft. behind the blocked area, the discharge required approximately 7.5 days to dissipate into the Arkansas River. For comparison, if an initial head of 163 ft. was used, the discharge required approximately 6.5 days to dissipate into the Arkansas River. Also, if the initial head was 163 ft. behind the blockage, the discharge of the blowout was estimated to be approximately 230 cubic feet per day (refer to Figure 5). 3.3 Estimation of the Depth of the Arkansas River and the Velocity of the Arkansas River with respect to the blowout The depth and velocity of the Arkansas River, taking into account the partial blowout contributions to the river, varied seasonally. If the blowout were to occur in the spring, then the river depth increased to about 5 ft. and returned to a constant depth of approximately 4.5 ft. over a period of 7.5 days (refer to Figure 6). The spring- time velocity increased initially to 8.7 ft 2 /day. Over a period of approximately 8 days, the velocity decreased and leveled out at about 8 ft 2 /day (refer to Figure 6). If the blowout were to occur in the summer, then the river depth increased to approximately 3.8 ft. and leveled off just below 3.2 ft. over a period of approximately 8 days (refer to Figure 7). The velocity during the summer increased to 7.3 ft 2 /day and decreased over a period of 8 days to 6.4 ft 2 /day (refer to Figure 7). 3.4 Analysis of the transport of zinc contamination at three downstream locations including determining the time and distance that the concentration levels will be toxic to fish in the area The threshold used to evaluate toxicity to the fish population in the Arkansas River was based off of a 1.3 parts per million (ppm) threshold (US Department of the Interior Bureau of Reclamation, 1998). Anything greater than 1.3 ppm was considered toxic to the fish population. Three popular locations for fishing were analyzed for zinc concentration levels after the partial blowout (ArkAnglers, 2014 and McCord, 2003). The three downstream locations from the LMDT included the following: Granite, CO (Approximately 87,536 ft. from the LMDT (Near The Numbers )) Between Granite and Buena Vista, CO (Approximately 131,442 ft. from the LMDT) Buena Vista, CO (Approximately 175,348 ft. from the LMDT (Near the recreation fields downtown)) A range of contamination levels and the length of toxic periods to fish in the Arkansas River are presented in Tables 2-4 below for each of the three locations (refer to Figures 8-10 for graphical representations of the data in Tables 2-4). Variations between spring and summer are also represented.

6 Table 2. Location: Granite, CO Zinc Concentration Levels Spring 2.68 ppm Zinc levels below 1.3 ppm threshold No concern to fish population 11.9 ppm Max Concentration (+1 std. deviation): ~5.55 ppm Above 1.3 ppm threshold level for approximately 6 days Summer Max Concentration (+1 std. deviation): ~1.45 ppm Above 1.3 ppm threshold level for approximately 1.2 days Max Concentration (+1 std. deviation): ~6.9 ppm Above 1.3 ppm threshold level for approximately 8.5 days Table 3. Location: Between Granite and Buena Vista, CO Zinc Concentration Levels Spring 2.68 ppm Zinc levels below 1.3 ppm threshold No concern to fish population 11.9 ppm Max Concentration (+1 std deviation): ~5.35 ppm Above 1.3 ppm threshold level for approximately 6 days Summer Max Concentration (+1 std. deviation): ~1.4 ppm Above 1.3 ppm threshold level for approximately 1.1 days Max Concentration (+1 std. deviation): ~6.8 ppm Above 1.3 ppm threshold level for approximately 8.5 days Table 4. Location: Buena Vista, CO Zinc Concentration Levels Spring 2.68 ppm Zinc levels below 1.3 ppm threshold No concern to fish population 11.9 ppm Max Concentration (+1 std. deviation): ~5.35 ppm Above 1.3 ppm threshold level for approximately 5.1 days Summer Max Concentration (+1 std. deviation): ~1.35 ppm Above 1.3 ppm threshold level for approximately 1 day Max Concentration (+1 std. deviation): ~6.7 ppm Above 1.3 ppm threshold level for approximately 8.5 days

7 4.0 Error Assessment The convolution analysis of the contamination source through time used plus and minus one standard deviation from the mean to account for uncertainties in the parameter inputs. Input values were randomized for the following variables: Blowout diameter Friction coefficient of the tunnel Length of the blowout Discharge of the Arkansas River Area of the blowout The intent of the error assessment was to better define and account for inherent errors in the input parameters. These errors are due to lack of information, inconsistencies in reported data such as the initial head behind the blocked area, and in measurements for obtaining changes in elevation, distances, and the slope of the river. 5.0 Conclusions The section of the Arkansas River between Leadville and Buena Vista, CO is located in a semi- arid environment (Watts, 2000). In a semi- arid environment, seasonal variability in the flow of the Arkansas River is expected to significantly impact the zinc concentration levels and periods of toxicity to the fish population. The results of the modeling work suggests that seasonal variability in flow rates contributes greatly to the outputs of the model. For example, in the spring, the depth of the Arkansas River is increased to 5 ft. on the first day of the partial blowout (refer to Figure 6). However, in the summer, the depth of the Arkansas River is only increased to approximately 3.8 ft. on the first day (refer to Figure 7). Similarly, the spring velocity of the Arkansas River is increased on the first day of the blowout to 8.7 ft 2 /day where the summer velocity is increased to 7.3 ft 2 /day (refer to Figures 6 and 7). In general, the spring time depths and velocities are greater than those expected in the summer. Thus, several of the parameter inputs, such as the flow rate of the Arkansas River, are more sensitive than others in evaluating the effects of the blowout and movement of the contaminant plume downstream. One of the more sensitive parameters in evaluating the discharge of the blowout, as well as the depth and velocity, is the friction coefficient. The friction coefficient impacts the max zinc concentrations downstream, but does not significantly impact the length of time required for the contaminant plume to pass a specified location. The initial head behind the blocked area is also sensitive in modeling the effects of the blowout. The initial head impacts the length of time required for the discharge of the blowout to dissipate. The larger the initial head, the shorter the time period required for dissipation of the discharge of the blowout into the Arkansas River. Due to the uncertainty in many of the parameter inputs, a Monte Carlo simulation was run and the plus one standard deviation was used to analyze the zinc concentration levels and length of time required for the threshold level of the contaminant plume to pass specified locations downstream from the LMDT. General trends from the simulation suggest that the threshold levels of the zinc contamination plume will pass critical locations two to three days faster in the spring than in the summer due to seasonal variability in the Arkansas River flow rate (refer to Tables 2-4). Max zinc concentrations passing the specified locations are also higher in the summer than in the spring by approximately 1.45 ppm. Max concentration levels in the summer and spring are greatest at Granite and decrease downstream to Buena Vista (refer to Tables 2-4). The max concentration modeled at the Granite site during the summer was approximately 6.9 ppm, which was about a 5 ppm decrease from the initial 11.9 ppm that entered the Arkansas River from the LMDT. If the blowout occurred in the spring and zinc concentration levels were at a best case scenario of 2.68 ppm discharged from the LMDT, then zinc levels would be below the threshold level of 1.3 ppm. Zinc levels below 1.3 ppm

8 would not threaten the fish population between Granite and Buena Vista. However, if the blowout occurred in the summer time, then even the lower range of zinc concentrations discharged from the LMDT would be a concern to the fish population between Granite and Buena Vista. The threshold levels of zinc that would threaten the health of the fish population would pass the specified locations within one day if initial concentrations were at 2.68 ppm, but could take up to 8.5 days to pass the specified sites if initial concentrations were at 11.9 ppm (refer to Tables 2-4). Therefore, although there is still some uncertainty in the input parameters, general trends suggest that a partial blowout during the summer would be a greater threat to the fish population between Granite and Buena Vista than if it occurred in the spring. The duration of exposure to toxic zinc levels would also be longer in the summer than in the spring. The higher flow rates due to spring runoff would aid in the reduction and dilution of elevated zinc concentrations after the occurrence of a partial blowout. 6.0 Recommendations For future studies and refinement of the model for evaluating the effects of a partial blowout and the elevated zinc concentration levels at specified locations downstream from the LMDT, the following recommendations are suggested: 1. Conduct further investigation to better define the initial head located behind the blocked area in the LMDT 2. Perform additional sensitivity analysis on all parameters to evaluate which have the greatest and least impact on the blowout discharge, the zinc concentrations, and the time period for threshold levels of zinc concentrations to pass critical locations 3. Refine results by using a numerical modeling method the need for numerical modeling is emphasized by the unrealistic dispersivity value of 400 ft./sec. used in the model to smooth out the curves in the graphs produced

9 Figure 1. Portal of Leadville Mine Drainage Tunnel Connecting to the East Fork Arkansas River (US Department of the Interior, 2008)

10 Figure 2. Blockage near Pendery Fault that has potential for a partial blowout (US Department of the Interior, 2013)

11 Figure 3. Moody Diagram for evaluating the friction factor in the Dacry- Weisbach Equation (Elger et al, 2013) Note: Darcy- Weisbach Equation for Head Loss Due to Friction (h f ) h! = f!!!!!! f is the resistance coefficient (Obtained from the Moody Diagram above) L is the length of the pipe D is the diameter of the pipe V is the velocity that fluid moves through the pipe

12 Figure 4. Estimated Discharge of the Partial Blowout based on Head Loss through Time Head Loss through time: Constants Used in Equations below to model head loss through time: Initial Head, ho: 119ft Roughness coefficient, f: 0.2 Diameter, D: 5 ft. Length, L: 200 ft. Gravity, g: 32.2 ft/s 2 Estimated Volume of Mine Drainage, volmine: 1.5 billion gallons (Worst Case Scenario) Equations Used: Velocity through the Tunnel, K Area of the top of the blocked area, Atop Area of the blowout, Ablow Head through time, h(t)

13 Figure 4 Continued. Estimated Discharge of the Partial Blowout based on Head Loss through Time From the estimated head loss through time, the discharge of the blowout through the tunnel was modeled. Estimated Flow Rates through Time in the tunnel: Note: Q is in ft 3 /day Equations used: Discharge of the partial blowout varying with time, Qblowout(t) Head through time, hreal(t)

14 Figure 5. Estimated Discharge of the Partial Blowout based on Initial Head at 163 ft. If Initial Head, ho: 163 ft. Head Loss through time: Estimated Flow Rates through Time in the tunnel: Note: When the initial head value is at 163 ft., the discharge of the blowout is greater than the discharge of the blowout when the initial head value is at 119 ft. The length of time it takes for the discharge to enter the Arkansas River is also shorter when the initial head is at 163 ft. when compared to the length of time in Figure 4 it takes the discharge to enter the Arkansas River. All equations in Figure 4 for calculating the head loss and estimated flow rates through time were used in Figure 5, with the exception of the initial starting head value.

15 Figure 6. Estimation of the Depth of the Arkansas River with respect to the Partial Blowout during Spring Spring variables used in modeling the depth and velocity of the river Flow rate of the Arkansas River, Q1river: 856cfs Width River, w: 25 ft. Slope, s: 0.01 Manning s Number, n: 0.05 Depth varying with time, b(t) (ft.) Discharge of the blowout, Qblowout(t) (ft 3 /day) Depth of the Arkansas River (ft.): Equations Used: Velocity of the Arkansas River (ft 2 /day): Equations Used:

16 Figure 7. Estimation of the Depth of the Arkansas River with respect to the Partial Blowout during Summer Summer variables used in modeling the depth and velocity of the river Flow rate of the Arkansas River, Q2river=503cfs Width River, w: 25 ft. Slope, s: 0.01 Manning s Number, n: 0.05 Depth varying with time, b(t) (ft.) Discharge of the blowout, Qblowout(t) (ft 3 /day) Depth of the Arkansas River (ft.): Equations Used: Velocity of the Arkansas River (ft 2 /day): Equations Used:

17 Figure 8. Zinc Concentration Analysis Location 1: Granite, CO Best Case Scenario: Min. Zinc Concentration, Spring Worst Case Scenario: Max. Zinc Concentration, Spring Note: Min Zinc Concentration: 2.68 ppm, Max Zinc Concentration: 11.9 ppm, Toxic Threshold Concentration to Fish: 1.3 ppm, Dotted Line: Plus 1 Standard Deviation, Red Line: Mean Concentration, Green Dashed Line: Minus 1 Standard Deviation, x- axis measured in days, y- axis measured in ppm Best Case Scenario: Min. Zinc Concentration, Summer Worst Case Scenario: Max. Zinc Concentration, Summer Note: Min Zinc Concentration: 2.68 ppm, Max Zinc Concentration: 11.9 ppm, Toxic Threshold Concentration to Fish: 1.3 ppm, Dotted Line: Plus 1 Standard Deviation, Red Line: Mean Concentration, Green Dashed Line: Minus 1 Standard Deviation, x- axis measured in days, y- axis measured in ppm

18 Figure 9. Zinc Concentration Analysis Location 2: Between Granite and Buena Vista, CO Best Case Scenario: Min. Zinc Concentration, Spring Worst Case Scenario: Max. Zinc Concentration, Spring Note: Min Zinc Concentration: 2.68 ppm, Max Zinc Concentration: 11.9 ppm, Toxic Threshold Concentration to Fish: 1.3 ppm, Dotted Line: Plus 1 Standard Deviation, Red Line: Mean Concentration, Green Dashed Line: Minus 1 Standard Deviation, x- axis measured in days, y- axis measured in ppm Best Case Scenario: Min. Zinc Concentration, Summer Worst Case Scenario: Max. Zinc Concentration, Summer Note: Min Zinc Concentration: 2.68 ppm, Max Zinc Concentration: 11.9 ppm, Toxic Threshold Concentration to Fish: 1.3 ppm, Dotted Line: Plus 1 Standard Deviation, Red Line: Mean Concentration, Green Dashed Line: Minus 1 Standard Deviation, x- axis measured in days, y- axis measured in ppm

19 Figure 10. Zinc Concentration Analysis Location 3: Buena Vista, CO Best Case Scenario: Min. Zinc Concentration, Spring Worst Case Scenario: Max. Zinc Concentration, Spring Note: Min Zinc Concentration: 2.68 ppm, Max Zinc Concentration: 11.9 ppm, Toxic Threshold Concentration to Fish: 1.3 ppm, Dotted Line: Plus 1 Standard Deviation, Red Line: Mean Concentration, Green Dashed Line: Minus 1 Standard Deviation, x- axis measured in days, y- axis measured in ppm Best Case Scenario: Min. Zinc Concentration, Summer Worst Case Scenario: Max. Zinc Concentration, Summer Note: Min Zinc Concentration: 2.68 ppm, Max Zinc Concentration: 11.9 ppm, Toxic Threshold Concentration to Fish: 1.3 ppm, Dotted Line: Plus 1 Standard Deviation, Red Line: Mean Concentration, Green Dashed Line: Minus 1 Standard Deviation, x- axis measured in days, y- axis measured in ppm 7.0 References

20 AllAboutRivers Staff (2014) Colorado Streamflows. Accessed online at flow.allaboutrivers.com/colorado/river_flow- sco.html on April 21, ArkAnglers (2014) Fishing Conditions Upper Basin: Leadville to Buena Vista. Accessed online at basin on April 20, Arkansas River, Leadville, CO N and W. Google Earth. 9/27/2013. Accessed April 20, Bailey, B. (2008) Final Leadville Mine Drainage Tunnel Risk Assessment Review Memo. Department of the Army. Accessed online at on April 20, Benson, D. (2014) Groundwater Senior Design Lecture Notes for the Leadville Mine Drainage Tunnel. Colorado School of Mines. Spring Biley, C. (2008) EPA Letter to Energy Commerce. EPA. Accessed online at on April 20, Chow (1959) Manning s n Value. Accessed online at on April 19, Elger, D., Williams, B., Crowe, C., Roberson, J. (2013) Engineering Fluid Mechanics, 10 th Edition. John Wiley and Sons, Inc. McCord, M. (2003) Arkansas River- Granite to Buena Vista. Southwest Paddler. Accessed online at on April 18, US Department of the Interior Bureau of Reclamation (2008) Reclamation- Managing Water in the West- Leadville Mine Drainage Tunnel Risk Assessment. Accessed online on April 21, US Department of the Interior Bureau of Reclamation (2013) Leadville Mine Drainage Tunnel Overview. Accessed online at on April 20, US Department of the Interior (1998), Guidelines for Interpretation of Biological Effects of Selected Constituents in Biota, Water, and Sediment, Zinc. Bureau of Reclamation, US Fish and Wildlife Service, USGS, and Bureau of Indian Affairs. National Irrigation Water Quality Program Information Report No. 3. Accessed online at on April 18, Watts, K. (2000) Hydrogeology and Quality of Ground Water in the Upper Arkansas River Basin from Buena Vista to Salida, CO, US Department of the Interior and US Geologic Survey. Scientific Investigation Report Accessed online at on April 18, Wellman, T., Paschke, S., Minsley, B., and Dupree, J. (2011) Hydrogeologic Setting and Simulation of the Ground Water Flow near the Canterbury and Leadville Mine Drainage Tunnels, Leadville, CO. US Department of the Interior and US Geologic Survey. Scientific Investigation Report Accessed online at on April 18, Wireman, M., Gertson, J., and Williams, M. (2006) Hydrogeologic Characterization of Ground Waters, Mine Pools, and the Leadville Mine Drainage Tunnel, Leadville, CO. Accessed online at Wireman- CO.pdf on April 18, USGS Staff, (2014), USGS gauge # ARKANSAS RIVER BELOW GRANITE, CO. Accessed online at on April 20, 2014.