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 Inflow
Report 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,

Rich
Rich,

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