N 40.14122 W 77.67008
Take a look on Acmemapper. The topo map shows that there was a reservoir. The current imagery shows that it's been drained.
Is there a place to park then walk in on public land?
Yes. You can park on Trout Run Rd. which intersects 641 from the north in Gunther Valley. Trout Run Rd. is gated shortly north of there and it’s a lengthy walk up to the old reservoir.
I did it a few Winters ago. I’m a Turnpike history buff, and it was a fun history/fishing hike type of day. Pack a lunch, as it will take all day. Stay on the road grade/trail as you get near the existing TPike Tunnels, from what I understand they don’t like you getting too close to them. But in Winter, there are cool photo opportunities of the tunnels from the grade. The stream itself runs through the narrow valley (Gunther Valley) between Blue Mountain and Kittatinny Tunnels, and flows under the TPike in the short couple hundred yard stretch between them.
The fishing was poor. The best habitat is in the very lowest stretch by the mouth at the Connie. I caught a few Brookies, but it was fun day nonetheless with the history aspects of the TPike and the old drained reservoir. I didn’t fish the reservoir section. That’s where I stopped fishing and just finished the hike up to check out the views of the tunnels. IIRC it was February and getting on 4:00 by the time I reached the tunnels and I wanted to complete the hike out (several miles) in daylight.
It would likely fish better in warmer conditions obviously, and the longer the reservoir is gone the better. I suspect it may get some run ups from the Connie too. It’s up your alley Dwight, you’d like it.
The whole bit is in Tuscarora SF, except for right around the tunnels. Check the SF maps to be certain of where you can and can’t be around the tunnels.
Edit: Just checked the map myself. There is also a short, few hundred yard stretch, about 2/3 of the way to the old reservoir that is posted by a hunting club. Had forgotten that in the meantime. It’s well posted and you’ll know when you hit it. When you get there, just get back on the grade and walk up around it and in a 1/4 mile or so you’re back in SF.