Minnehaha Creek Mystery Solved!
Park board archivist Angela Salisbury writes:
I believe we’ve solved our mystery. In The Story of the W.P.A. in the Minneapolis Parks, Parkways and Playgrounds volume for 1940 (dated Jan 1, 1941), page 24, regarding the Minnehaha Parkway:
“A small limestone shelter was built north of Minnehaha Creek and west of Xerxes Avenue to house the meter for measuring the amount of sewage entering the city sewer system from the Village of Edina. The village supplied the material for this construction and the work was done by a Park Board W.P.A. crew.”
There is an image of the structure on page 25.
These W.P.A. books are really wonderful, and I’m happy to report they are digitized and available online via the Minnesota Digital Library. This volume is here: https://collection.mndigital.org/catalog/p16022coll55:910#?c=&m=&s=&cv=&xywh=-1177%2C0%2C5267%2C3692
Many wonderful images in these volumes!
Thanks, Angela!
David Carpentier Smith
Minneapolis Park History 
The photography in these WPA annuals is extensive and very good. I noticed a number of images of the limestone quarry and I had no idea it was as large an operation and the size it was. In the narrative area of one year it was mentioned that it was near the incinerator. My wife and I had seen that in the past and from it a series of long and high quality stairways went about half way down the side of the hill. The stairs were in very good shape and probably rarely used over the years. Anyway, there was nothing but hillside near there and that doesn’t match with the images. The question is, where exactly was the quarry? Thanks-Dan.