Conodoguinet Creek - Part 1

River of the month #106

author: Pat Reilly

Finally getting around to writing up the Conodoguinet. It's still there, flowing quietly along through Cumberland County, waiting to be talked about while every creek, large or small, paddle-worthy or not, within a hundred miles of it has been the subject of a ROM column. Why did it take do long for the Conodoguinet to make it to ROM? Well, try as you might, you'll probably find it hard to get excited over this one. Oh, it has its nice rural sections, and even a not-so-well-known whitewater section. But most of the time it drags along, a big slow slug oozing through the suburbs.

Now hold on, I can't do this! All streams have their worth. The Conodoguinet can't be that bad. It's a big creek (small river, actually), meaning it has a fairly long season. It's close to Harrisburg and Carlisle. It has a designated water trail, which means plenty of access. Shuttles are a breeze, if you don't mind the Carlise Pike. So hey, lets explore the Conodoguinet. Like it's Cumberland Valley neighbor, the Yellow Breeches, there's a lot to talk about. So we'll split the discussion into two monthly columns.

It's hard to talk about the Conodoguinet without talking about the Great Valley. I used to hear folks say that the Great Valley's northern border in this area, Blue Mountain, is a continuous ridge running from New England to the southern states, broken only by water gaps. Nope! The ridge ends abruptly just north of route 30 west of Chambersburg. It's called Broad Mountain down there and it's the location of the Conodoguinet's headwaters.

The Conodoguinet lies mostly within the Great Valley, a large wide valley that does run uninterrupted from Canada to Alabama. Also known as the Great Appalachian Valley or Great Valley Region, it is one of the major landform features of the Appalachian Mountain system. Know locally as the Cumberland and Lebanon Valleys, it is not that well defined in central Pa without a significant southern boundary. However, going west the valley soon picks up South Mountain as its southern side and turns south crossing the Maryland and Virginia borders and becomes the Shenandoah Valley and eventually the Tennessee Valley. Heading the other way, the Great Valley takes in the Kittatinny area of the Delaware River valley, becomes the Hudson Valley and eventually encompasses Lake Champlain!

So it turns out that the 'ole Conodoguinet is right in the middle of something big, geologically speaking. Previous River-of-the-month creeks, the Conococheague and the Yellow Breeches, also lie within the Great Valley. So when comparing these 3 creeks we find similarities. First, all 3 are flatwater creeks as the Great Valley, actually a chain of valley lowlands, is quite broad and flat. And we find that these 3 creeks are limestone based as the underlying rock defining the Great Valley consists of limestone and shale.

Way back in 2000 we talked about a Conodoguinet tributary, Big Springs, a limestone spring big enough to paddle right where it flows from the earth. So one might wonder if the Conodoguinet is like the Yellow Breeches and can be boated year around relying on limestone spring water instead of rain. Sorry, no go! The Conodoguinet is no easier to find up than most Pennsylvania streams of similar size. I used to measure the amount of dissolved lime, in the form of parts per million of calcium carbonate, in both the Conodoguinet and Yellow Breeches as part of a stream monitoring project for Dickison College's ALARM group. We were surprised to note that the Conodoguinet's waters consistently measured higher in lime than the Breeches. So while it has more limestone dissolved in it, apparently the Conodoguinet lacks the big underground aquifers that keep the Yellow Breeches flowing at a consistent boatable level. Bummer!

Anyway, lets get to the boating. The Conodoguinet begins life as a mountain stream in a narrow little mountain valley west of Roxbury, in Franklin County. How narrow? Well, this is the same valley that you get about two seconds to glimpse while driving through the double tunnel on the Pa turnpike, the first tunnel going west from Harrisburg. As you emerge from the Blue Mountain tunnel and quickly enter the Kittatinny Mountain tunnel you blast through little Horse Valley.

The Conodoguinet begins at the other end of this skinny valley and flows swiftly through pretty hemlock woods and past small farms. The gradient is a respectable 30 feet per mile up here, way more than you'll find on the creek once out in the Great Valley. Continuous riffles and little rapids make for a lively trip. The rapids build a bit just before the creek pools up in the Letterkenny Army depot's water supply lake. Carry the 30-foot dam for this impoundment on the right. You'll need lots of water to run the Conodoguinet up in Horse Valley. The lower creek will need to be bank full, about 5 or 6 feet on the Hogestown gauge. But keep in mind that the gauge is so far below this upper section that the water will likely be gone up here by the time the gauge spikes. While this upper 8.5-mile section is quite pretty, keep in mind that strainers are bound to be a problem up here. I carried 5 in 2 miles on one trip.

There are only 2 bridges to access the creek above the Letterkenny impoundment but a road runs to the base of the dam. Below the big dam, the creek cuts a gap through Blue Mountain. The gradient and rapids in the gap remain pretty much the same level as up in the mountain valley but now many other obstacles and features add to the challenge of the little creek. Just below the dam there are two low water bridges that must be carried and a concrete ford to clunk over. Then the creek twists and turns a good bit making for some tree root undercuts. My paddling partner in a December 1992 trip managed to stuff her boat up under some of these roots causing anxious moments and a cold swim. As you emerge from the mountain gap another dam comes up quickly – a sloping 4-footer in the middle of the woods. We managed to boof over this dam once but it can have a nasty hydraulic. Beware! Then the creek splits forming 2 long braids before route 997, with both choices tight and likely to be strainered up.

After 997 as the braids re-connect the Conodoguinet has finished spilling into the Great Valley and so begins a transformation to a very different stream. But it is a gradual transformation and the Conodoguinet remains lively and quick to and below Orrstown for a few miles. It's still a small stream up here and won't be easy to find up. If you come you'll find a decent gradient on this12-mile stretch, although the sometimes steep riffles are now formed mostly of cobble. This section will have a mix of woods and fields so strainers may still be a problem. At the Burnt Mill Bridge, 5 miles below Orrstown, the creek is pretty much out of the woods. Farms now dominate the scenery and you can forget about rapids, even riffles are rare. But there is still 70 miles of creek to go and thus much more to talk about. So we'll pick it up here next month.

Pat Reilly

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