### RE: Data Request Ladwig, Ken to: Richard Kinch 01/18/2010 04:39 PM Cc: Alexander Livnat, Steve Souders

Rich,
As I mentioned, we have not done a systematic or detailed evaluation of the percentage of different outflows from ash ponds. I dug around and found a few reports where some form of pond flow balance was done. In most cases, these were one time calculations; in one case, three calculations were made. These were generally very crude flow balance calculations, and provide gross estimates at best.
Below I have broken the estimates out into two types. Type 1 (Comanagement Reports): inflows from various plant sources were taken from NPDES reports and/or estimated using pipe calculations or similar means, annual rainfall, estimated runoff (into the basin), and estimated groundwater inflows (if any). Outflows were generally determined as measured or estimated pond effluent discharge, calculated recharge to groundwater using Darcy equation (based on one or two nested well pairs and pond elevations), and regional evaporation estimates. Type 2 (PISCES Reports): inflows were calculated as described above, and effluent discharge was measured by flow meter or staff gauge method. In this case, no other outflows were measured or estimated.
I included the report numbers, you should be able to go to epri.com and download these reports if you would like to. Enter the report number in the search box.

TYPE ONE CALCULATION (ESTIMATED INFLOWS AND OUTFLOWS)
Report TR-108242, CL-Site Comanagement Report Effluent Discharge: 93% Groundwater Recharge: 5% Evaporation: 2%
Report TR-108242, SX-Site Comanagement Report Effluent Discharge: 86% Groundwater Recharge: 14% Evaporation: <1%
Report EN-7545, L-Site Comanagement Report Effluent Discharge: 61% Groundwater Recharge: 28% Toe Drains: 6% Evaporation: 5%
Report 100955, C-Site Comanagement Report (multiple ponds) Effluent Discharge: 6% (visual estimate, not measured) Groundwater Recharge: 89% (Inflow-Effluent Discharge, not Darcy calculated) Evaporation: 6%

TYPE TWO CALCULATION (ESTIMATED INFLOWS AND EFFLUENT DISCHARGE)
Report TR-108890 V1, A-Site Pisces Report Effluent Discharge: 78% of InflowReport TR-108890 V1, B-Site Pisces Report Effluent Discharge: 93% of Inflow
Report TR-108891 V1, C-Site Pisces Report Effluent Discharge: 84% if Inflow
Report TR-108892 V1, D-Site Pisces Report Effluent Discharge: 96%, 76%, and 97% of Inflow
Report TR-112433 V1, E-Site Pisces Report (multiple ponds) Effluent Discharge: 76% of Inflow
Note that in at least two of the above cases the estimates incorporated more than one pond.
I am not sure if this helps you much. Let me know if there is any other information I can provide.

Ken

_______________________ Ken Ladwig EPRI 262-754-2744 262-385-7820 (cell)
-----Original Message----- From: Kinch.Richard@epamail.epa.gov [mailto:Kinch.Richard@epamail.epa.gov] Sent: Thursday, January 14, 2010 6:23 AM To: Ladwig, Ken Cc: Livnat.Alexander@epamail.epa.gov; Souders.Steve@epamail.epa.gov Subject: RE: Data Request

Ken
An unlined surface impoundment would best fit my needs. I am just looking for a rough estimate. The inflow/outflow studies would be interesting and possibly fairly rapid (in rough terms I might look at the difference being the leakage rate -- as you mention, there are evaporative losses, but there are also rainfall gains -- knowing the location, and pond area, an estimate of the net gain or loss from evaportation/rainfall could be calculated, but I sense that is an unnecessary refinement to illustrate the rough magnitude differences between the discharge and leakage. Hopefully some of your pond studies involve unlined ponds.)
A sample case or two from modeling results might also work, but if you don't have the outflow rates, that will not work -- maybe it is possible to pull those values off EPA's NPDES database, PCS which is accessible online (but you would need to know the facility and which discharge belonged to the pond in question).
I sense the inflow/outflow studies would be easiest and would meet my needs.

Thanks, RichRich,
We have not done a systematic evaluation of relative water volumes released through an impoundment NPDES outfall versus leakage through the bottom on an industry-wide basis. I would agree with you that the volumes discharged through the NPDES outfall are generally much greater. The amount of bottom leakage will depend on a number of factors as you are aware, such as liner type (if any), underlying geology, thickness of ash layer, and relative height of the pond water surface.
We have modeled bottom leakage at several ponds over the years using a variety of methods: simple Darcy calculations, HELP, groundwater flow model calibration, and water balance. I am not sure which, if any, of these ponds would be representative of typical circumstances though. They were usually done as part of a broader site investigation, not necessarily to establish typical leakage rates from ponds. We don't always have NPDES outflow rates as part of those studies, because we were not doing a water balance. I can go back and look through these studies if that information would be helpful.
We also have several pond studies where inflows and outflows were quantified, but leakage rates and evaporation rates were not estimated. These may provide some ballpark information on leakage if you assume that the net difference between inflow and outflow is accounted for by combined evaporation and leakage.
Let me know if any of this information would be useful to you and I will look into it a little more thoroughly.

Ken

_______________________ Ken Ladwig EPRI 262-754-2744 262-385-7820 (cell)
-----Original Message----- From: Kinch.Richard@epamail.epa.gov [mailto:Kinch.Richard@epamail.epa.gov] Sent: Tuesday, January 12, 2010 8:27 AM To: Ladwig, Ken Cc: Livnat.Alexander@epamail.epa.gov; Souders.Steve@epamail.epa.gov Subject: Data Request

Ken,
I have been thinking about various issues associated with coal ash surface impoundments, including trying to quantify the relative release to the environment from the impoundment's surface water discharge versus leachate. As a general matter, I assume the surface water discharge (regulated through the NPDES permits) is far larger than the amount of leachate that is released through the bottom of the impoundment. Do you have any data that would quantify a typical circumstance? I assume the surface water discharge figures would be direct measurements and the leachate generation would be either modeled.

Thanks, Rich Kinch 703-308-8214% Effluent Discharge % Leachate 0.93 0.07 0.86 0.14 0.61 0.39 0.06 0.94 0.78 0.22 0.93 0.07 0.84 0.16 0.96 0.04 0.76 0.24 0.97 0.03 0.76 0.24

Max 0.97 0.94 Min 0.06 0.03 Mean 0.769 0.231 Median 0.84 0.16