PA Class A Streams - Identifing Limestoners

[UncleShorty]

I'm trying to develop a list of Class A spring fed limestone creeks in several counties.

Looking at the PA Class A Waters posted on the DCNR website I see the last column in the data for each stream designated, "T_Alk", for Total Alkalinity of that stream.

My question is this: How do I identify spring fed limestoners?

My default method has been to include any water with a T_Alk of 100 or greater.

Is that a legit way to identify the streams in which I am interested?

What would be the "Low" cutoff, vis-à-vis T_Alk for a spring fed limestone creek?

Is my method sound? How do/would YOU identify limestone creeks?

Any guidance would be appreciated. Thanks and best regards.

 

[Dave_W]

There's a book by Joe Armstrong: Guide to PA Limestone Streams (or something similar). It would be a handy reference for what you're trying to do.

 

[Mike]

70 mg/l (70 ppm) is what is used by the PFBC

 

[UncleShorty]

Dave, thanks for the reply. I have Armstrong's book. My copy has a 2000 copyright. It's OK but far from up to date, especially for small streams.

Take Cambria County for instance. Armstrong shows no limestone streams, (there isn't a Cambria County section in his book). But in the DCNR's data there are 3 or 4 streams over 100 T_Alk. Now, they are all near Barnesboro, so perhaps they are mine drainage mitigation streams. But how does one tell?

 

[UncleShorty]

thanks, Mike

 

[Jessed]

cacoosing cream that runs into the Tully is over 100 I haven't seen the whole stream but the first 50 Doesn't look like a limestone stream. But I'm not sure.

 

[salmonoid]

UncleShorty wrote:
Dave, thanks for the reply. I have Armstrong's book. My copy has a 2000 copyright. It's OK but far from up to date, especially for small streams.

Take Cambria County for instance. Armstrong shows no limestone streams, (there isn't a Cambria County section in his book). But in the DCNR's data there are 3 or 4 streams over 100 T_Alk. Now, they are all near Barnesboro, so perhaps they are mine drainage mitigation streams. But how does one tell?

Look at the underlying bedrock geology. And even that generality may not capture pockets of calcareous beds within an otherwise non-limestone bedrock which will boost alkalinity. I don't think mitigation alone would generate that high of alkalinity.

 

[UncleShorty]

salmonoid:

Great suggestion. I found a DCNR mapping site that has a library of geological data maps.

http://www.dcnr.state.pa.us/topogeo/publications/pgspub/map/index.htm

I've located a general map that shows the large formations in PA and a map with oodles and scads of geologic information. That map will be quite handy in locating smaller formations.

Thanks for the tip.

 

[DaveKile]

Great topic UncleShorty and would really enjoy hearing what you find out.

 

[pcray1231]

My default method has been to include any water with a T_Alk of 100 or greater.

It's not a bad way. I think your number may be a bit high, but it would only matter in but a handful of cases.

Generally "pure" freestoners are well under 50, often considerably less than that. And "pure" limestoners are generally well over 100. So those that fall in the middle are sort of half and half. "Limestone influenced". So it just depends where you wanna draw the line. Personally, I consider "significantly limestone influenced" and "limestone" to be one and the same. The truth is that there aren't very many out there that are "pure" limestoners, and for those that are, it's only for a short distance before you start getting a bit of freestone influence. So it's really gauging to what degree it's limestone.

But I'd nod in support of any number between 50 and 100 I think. It's an arbitrary line.

The only real "exceptions" I'm aware of are in NW PA. Warren/Erie county boundary area, near Corry. There's a little driftless area there (for one ice age, anyway). There's not limestone bedrock nor super large limestone like springs, but there are T_Alk's of well over 100. Limestone water chemistry, freestone spring nature.

Jessed, Cacoosing IS a limestoner. Many streams in the Reading region are, including the Tully itself, Wyomissing Creek, and others.

 

[Chaz]

The topic of whether a stream is "pure limestone" has always caused me to gnash teeth. If it's fed by limestone springs it is a limestone stream, examples are Penns, Spring, Fishing, Peters, LJ below Altoona. These all have large springs that maintain flows. Some even have dry streams, Fishing Creek, being one of them. The other Fishing Creek, Benton, is limestone influenced. There are limestone spring near rt. 118 that feed it, and make it cold for a long way down and very fertile.
There are many more limestone streams that start as freestone streams, but the summer flows are maintained by big springs, Willow Creek is one of these types of limestone streams, so once it reaches the valley from the top of the Reading Prong, it is a limestone stream.

 

[salmonoid]

UncleShorty wrote:
salmonoid:

Great suggestion. I found a DCNR mapping site that has a library of geological data maps.

http://www.dcnr.state.pa.us/topogeo/publications/pgspub/map/index.htm

I've located a general map that shows the large formations in PA and a map with oodles and scads of geologic information. That map will be quite handy in locating smaller formations.

Thanks for the tip.

This is useful too:

http://www.gis.dcnr.state.pa.us/geology/index.html

An example of how mixed up a formation may be:

The Glenshaw Formation consists of repeated sequences of sandstone, siltstone, shale, claystone (including red beds), limestone, and coal. It contains four major marine zones that are, from lowest to highest in stratigraphic position, the Brush Creek, Pine Creek, Woods Run, and Ames. The coal beds in the Glenshaw Formation are sporadically mined. The formation increases in thickness from about 280 feet in the southwest to about 410 feet in the northeast (Geyer and Wilshusen, 1982; McElroy, 2001).

Or:
The Allegheny Formation is composed primarily of cyclic sequences of clay shale, claystone, siltstone, sandstone, limestone, and coal. Freshwater limestone beds (commonly less than 5 feet thick) or calcareous claystone with limestone nodules commonly underlie the coal beds in the upper third of the formation. The Allegheny is characterized by the presence of economically significant coal beds (the Upper and Lower Freeport coals, the Upper, Middle, and Lower Kittanning coals, the Clarion coal, and the Brookville coal). These coal beds (or coal horizons where there is underclay but no coal) occur on average at 50-foot intervals. The Johnstown limestone underlies the Upper Kittanning coal. The sandstones are fine to medium grained, sometimes conglomeratic, lenticular fluvial channel deposits that average 10 to 30 feet in thickness but that can coalesce to 100-foot-thick sequences. The Allegheny Formation ranges from about 280 to 320 feet in thickness (McElroy, 2001).

So locally, if this is a thicker sequence of limestone, one stream might be limestone influenced. But that bed of limestone may pinch out in any direction and simply be non-existent or an inch thick just a few miles away.

 

[pcray1231]

The topic of whether a stream is "pure limestone" has always caused me to gnash teeth.

Sort of agree, but mostly for an opposite reason.

It's real hard to be "pure" limestoner or freestoner. As you said, many limestoners start off as freestoners and pick up a limestone spring. Many more start as limestoners and pick up freestone tribs and springs. About the only case you have a "pure" limestoner is if it starts off that way and you are very close to the source. Penns Creek at Penns Cave is an example. But you don't have to go too far before it picks up freestone tribs. And then more limestone tribs. And then more freestone tribs....

Likewise, freestoners almost always have some limestone present. The primary bedrock may not be limestone, hence you don't get the big springs. But typically there is a limestone layer down there somewhere, and the stream may pass through a small portion, or at least have limestone mixed in with the overburden or soil. You can find particles or veins of limestone in sandstone, for instance. This is why T_Alk is almost never zero.

Hence, limestone vs. freestone isn't something that's this or that. It's a continuum. It's us humans that have to draw arbitrary lines to categorize and put them in a certain shoebox. This whole bit about what T_Alk number indicates limestone vs. freestone is thus subjective and unanswerable. Where do YOU want to draw the line between a particularly rich freestoner vs. a particularly diluted limestoner? Cause that's what that T_Alk of 50-100 range gets you.

But yes, higher numbers indicate more limestone influence, and lower numbers indicate less.

 

[Jessed]

Pcray, that's pretty cool! I've only been up to the water fall on that creek. I hope the springs enter after the water fall because that's a lot of still water at the top to warm up.

 

[pcray1231]

Jessed, as a rule of thumb with Cacoosing, there are smallish limestone springs throughout it's length and that of Little Cacoosing. But most of the extreme headwaters are freestone in nature.

Looking at google terrain view can tell you a lot. There's a little depression area that roughly follows 422. Sinking Spring to Robesonia, widest around Sinking Spring. The valley is kind of U shaped though 422 cuts a straighter line. That depression is limestone bedrock. The eastern portion drains Wyommissing Creek, the central portion drains to Cacoosing and Little Cacoosing, and the western portion all the tribs of Spring Creek (hint hint, see name). This includes Hospital Creek, Manor Creek, Furnace Creek, etc. All of the above are limestoners once they hit that valley and pick up limestone springs.

Along the streams are the telltell signs of a bunch of little ponds and such. Those are limestone springs. Yes, in most cases they have been dammed or at least heavily altered by man to make a small impoundment, but it's the location of an original spring nonetheless.

To the north and south are some higher lands with little rivlets flowing down off of them in narrow, water formed V shaped valleys (some of which are the upper portions of the same streams). Those are freestone till they hit that valley, and then they turn limestone.

Zooming WAY out you can see that Reading lies just to the South of the Great Valley, the same valley that includes Carlisle and Chambersburg and Lebanon farther west, and Kutztown, Allentown and Bethlehem to the East. The entire valley has large portions of limestone bedrock underlying it, and many of the streams within it are limestoners. There's a little extension of that valley south to Reading.

 

[Chaz]

That Spring Creek starts at a huge limestone spring, and it holds a good population of wild trout, but it's all on private property. I don't know if any of it's tributaries have enough flow to be called limestone stream or even limestone influenced.
Beware of using total Akl as a measure, Perkiomen Creek and the WB Perkiomen start as freestone streams but in a short time they are heavily impacted by a large number of farm ponds. Starting out at a little less than neutral, high 6's, they 46 and 47 total alk and have limestone springs feeding them and some very small tributaries. They never get higher than what PFBC shows on the Class A list as far as I know. The hitch is that the ponds have a much greater influence than the limestone springs, raising the PH to around 8, but do not raise T Akl very much.

 

[troutbert]

I'm not sure what your goals are.

If your goal is simply to fish good limestone streams, there a number of those that are well known, that have been written about in books, magazines, websites, etc.

Just drive to those streams and fish them.

If the goal is to find good limestone streams that are little known, that's a more difficult thing.

 

[UncleShorty]

troutbert,

Yeah, it's the smaller ones I'm interest in.

I'm looking in Cambria, Blair, Centre, Huntington, Bedford, Clearfield, Somerset, Juniata & Mifflin counties. (All within 1-1/2 hr drive from the Old Home Place, on top of Cresson Mountain.)

I know there are many "top of the line" limestoners in some of those counties. I'm looking for the "lesser knowns".

 

[pcray1231]

Some of those counties have none. Get westward or northward of the ridge and valley region and onto the plateau, and there's only freestoners.

So look southeast of the Allegheny front in your searches. Pretty much knocks out Somerset, Cambria, Clearfield, etc. That's not to say there isn't good trout fishing there. Just not limestone.

 

[UncleShorty]

Pcray, yeah I understand that. But why are the T_alk numbers over 150 in those creeks near Barnesboro in Cambria County?

Are they just freestoners with limestone influence? I'll take a ride over there in Nov.

If I'd known 45 years ago I was gonna take up fly fishin' I would have studied geology instead of electrical engineering...