Lisa Gardner - The killing hour

“Any information is helpful,” Mac said grimly.

Knowles opened a drawer. He pulled out a small plastic box with a well-worn label that read Field Kit. He popped open the container and started pulling out handheld meters complete with long metal probes. “Salinity first,” he murmured to himself, fiddled around, then stuck the probe in the water.

He didn’t say anything right away. Just grunted a few times.

“What does a salinity test measure?” Kimberly asked. “If it’s freshwater or salt water?”

“It can.” Knowles glanced up at her. “Basically, I’m measuring the amount of microsiemens per centimeter in the water, which gives me an idea of the dissolved content. Water on its own has no electrical conductivity. But water that has a lot of salt or other dissolved minerals in it will have a higher level of conductivity. More microsiemens per centimeter. So, in a roundabout way, we’re trying to tell where this water has been.”

He looked at the meter, then pulled the probe from the sample. “All right. According to my handy dandy salinity meter, this water has a reading of fifteen thousand microsiemens per centimeter. So, bearing in mind all my earlier caveats, what does that tell us?”

They all looked at him blankly, and he generously filled in. “The water has good conductivity. Not high enough to be salt water, but there’s a fair amount of dissolved content in this sample. Maybe minerals or ions. Something that conducts electricity better than water alone.”

“The water is contaminated?” Mac asked hesitantly.

“The water is high in dissolved content,” Knowles reiterated stubbornly. “At this moment, we can’t conclude anything more than that. Now, the logical thing would be to run tests for various minerals, which might answer your question. But we can’t do that, so let’s try pH.”

He set aside the first meter and inserted a second. He watched the meter, then frowned at it, then pulled out the tip and muttered, “Goddamn probe. Hang on a sec.”

He wiped the tip. Blew on the tip. Then gave the whole thing a small whack with his hand. With a grunt of satisfaction, he finally returned the probe to the water. The second time didn’t make him any happier.

“Well, shit on a stick, this is no good.”

“What’s wrong?” Kimberly asked.

“Sample must be too small for the probe, or my meter’s out of whack. To believe this thing, the pH is three-point-eight, and that just ain’t happening.”

This time, he banged the probe twice against the desk. Then he tried again.

“What does three-point-eight mean?” Mac asked.

“Acidic. Very acidic. Eat-holes-in-your-clothes level of acidic. Basic is a perfect seven-point-oh. Most fish and algae need at least six-point-five to survive; snails, clams, and mussels require seven-point-oh; while insects, suckers, and carp can go as low as six. So when we’re testing ponds and streams with any sort of aquatic life, generally we’re at least in the sixes. Now, in Virginia, rainfall has a pH of four-point-two to four-point-five, so pure rainwater would test low, but we know this isn’t pure rainwater thanks to the salinity test. Three-point-eight,” he was still shaking his head. “That’s ridiculous.”

He glanced at the meter again, gave a final growl of disgust, and yanked out the probe.

“What’s it saying?” Mac asked intently.

“Same garbage as before, three-point-eight. I’m sorry, but the sample has got to be too small. That’s all there is to it.”

“You’re three for three.” Kimberly spoke up quietly. “Three tests, three similar results. Maybe the water is that acidic.”

“It doesn’t make any sense, especially when you consider that any pH reading we’re getting now is actually higher than the original pH at the source. Frankly, we just don’t see pH readings below four-point-five. It doesn’t happen. Well, except maybe in cases of acid mine drainage.”

Mac straightened immediately. “Tell us about acid mine drainage.”

“Not much to tell. Water spills out of the mine or goes through tailings of the mine, getting contaminated as it goes. The pH ends up extremely low, possibly in the twos.”

“And that would be extremely rare? Something unusual in this state?”

Knowles gave Mac a look. “Buddy, there aren’t many places in the world that have pH readings in the twos, let alone in the state of Virginia.”

“Where is this mine?” Kimberly said urgently.

“You mean mines, s as in plural, as in coal mines. We’re loaded with them.”

“Where?”

“Southwestern Virginia mostly. There’s a good seven counties, I think.” Knowles was looking at Ray for confirmation. “Let’s see… Dickenson, Lee, Russell, Scott. Hell, I’m never going to be able to do this off the top of my head; let me look ’ em up.” He pushed back toward his filing cabinet, gave Ray’s legs a prodding shove, then rifled through some manila files.

“How big is the area?” Kimberly pressed him.

Knowles shrugged, then looked again at Ray. “Most of the southwestern corner of the state,” Ray offered up. “It’s not small, if that’s what you mean.”

“But the water probably came from there,” Mac asserted.

“I will not say that,” Knowles warned him. “Sample too small, results too subjective, too many variables beyond my control.”

“But it is a strong possibility.”

“ If you accept that reading of three-point-eight to be correct, then yes, a mine would be a good place to look for this kind of contaminated water supply. The only other possible theory…” He stopped, chewed on his lower lip. “It’s gotta be contamination of some kind,” he muttered at last. “That’s the only thing that could reduce the pH level so dramatically. Now, it could be from a mine. It could also be pollution from organic wastes. Basically, a large dose of biodegradable organic material gets in the water. Bacteria feed off the waste, bacterial population explodes, and now the bacteria consume oxygen faster than the algae or aquatic plants can replace it. Badda bing, badda boom: anything that needs oxygen to live-say, fish, insects, plants-dies, and anaerobic bacteria take over the water source; they’re about the only thing that can live at pH that low.”

“But you can’t test it for bacteria, can you?” Kimberly quizzed him.

“Nah, sample’s too small.”

“Is… is there anything else you can do?”

“Well, I could try testing for minerals. We got a guy around here who’s been squeezing water out of core samples going back thousands of years and running that stuff through the equipment. I know those water samples have gotta be small, but he’s gotten some results. I don’t know how good-”

“We’ll take anything,” Mac interrupted him.

“It’s very important,” Kimberly reiterated. “We need to narrow down this water to the smallest geographic region possible. Seven counties is a start, but seven miles would be better.”

“Seven miles huh?” Knowles gave her a doubtful look. “Even if I did get lucky and identify a bunch of minerals… Well,” he caught himself. “Then again, there are some key physiographic differences among the mine counties. A lot of sandstone and shale in some areas. Karst in others. So mineral results might help. Not seven miles, mind you, but I might be able to get you down to a county or two. I guess we’ll find out.”

“How long?” Mac pressed him.

“First I’m going to have to talk to the guy, figure out how to set up the equipment… I’d say give me a couple of days.”

“I’ll give you two hours.”

“Say what?”

“Listen to me. Two women are missing. It’s been nearly forty-eight hours now, and one woman is somewhere around that water. We either find her soon, or it won’t much matter anymore.”