It wasn’t until I started writing this story that I realized a celebration would be in order in a few months. Protecting the city of York from the destruction of flooding is a quiet giant that will soon turn 70 years old:

Indian Rock Dam

Aerial image above courtesy of Bing Maps

There’s something that has always fascinated me about Indian Rock Dam. Found in North Codorus Township along Markle Road, I remember  peering over the edge as a child and being mesmerized as I gazed into the concrete spillway.

I won’t lie to you. I’m still in awe as I drive across it as an adult.

Last month I was fortunate enough to receive construction photographs of the dam from Bruce Hengst Sr. Bruce found these treasures while looking through the contents of an old shoebox belonging to his grandmother and was happy to share them with me.

Built In The 1940s – York’s Protector Is Born

It’s difficult to determine where the photograph above was taken, but I believe it was directed towards the spillway of the dam. If I’m correct, Markle Road would be to the left just out of view in this photo.

According to the U.S. Army Corps of Engineers – Baltimore District website:

The protective works for York, Pennsylvania, consist of Indian Rock Dam about 3 miles upstream from York, and channel improvements on Codorus Creek in the city itself. Indian Rock Dam is an earth and rock structure 1,000 feet long rising 83 feet above the streambed, with a side-channel spillway and gated outlet conduit in the right abutment. The normally dry reservoir area has a storage capacity of 28,000 acre-feet (9.1 billion gallons) at spillway crest and controls a drainage area of 94 square miles, equivalent to 41 percent of the watershed upstream from York. The Codorus Creek project consists chiefly of 22,969 feet of channel improvement including channel widening and deepening, flood walls, levees, protection of bank slopes, and removal of a mill dam which increased channel capacity to 24,000 cubic feet per second. The two components protect the community against flood discharges about 33 percent greater than the record flood of August 1933. Tropical Storm Agnes (June 1972) filled the flood control reservoir and produced spillway flow.

The photograph above gives us a great perspective of just how large the dam would be after it was completed. The concrete feature shown in the center is the flood gate which is used to control the amount of water contained in the dam. During a flood event the gate can be closed in order to relieve pressure on the Codorus Creek as it flows through the city of York. When the flooding threat has been reduced, the gates can slowly be opened to release water back into the system.

If you look closely, there are people standing to the left of the spillway which are overshadowed by the size of this project. Also note the interesting building at the upper right, and what appears to be small bridge across a small gap. That would probably be where the spillway is located today.

A brief look at the numbers…

The highest pool ever recorded at the dam was during Hurricane Agnes on June 23, 1972. At that time the elevation of water was 436.44 feet and the dam was at 61.7% capacity. The floodgates were last closed during Hurricane Lee in September 2011.

If you think the height of water shown above seems excessively high, it may appear that way because the amount is based on sea level, which I’m only assuming.

When the project was completed in September 1942, the cost was $5,060,000.

The estimated damages that have been prevented by Indian Rock Dam are $54,618,000 as of the 2011 fiscal year.

And let’s not forget Sweigart’s…

The photographs shared by Bruce were processed by Sweigart’s Photo Service Shop, once found at 278-280 W. Market Street in York. The stamp above was found on the back of the photographs he shared. You can learn more about this business from one of my earlier stories: “A Look At Sweigart’s Photo Service Shop In York, PA“.

Let’s not forget to say thanks…

Without the construction of Indian Rock Dam, there’s no telling how much destruction could have been done during Hurricane Agnes in 1972. The flood waters during that disaster were the third highest in York’s history, but would surely have been much worse without the dam’s existence.

The next time you drive across the dam or peer into the Codorus Creek from its banks in York, tip your hat in appreciation to the city’s guardian, found just a few miles upstream from York.

If you have memories of the dam or photographs showing it when the floodgates were closed, I’d love to hear from you.

 NOTES:

1. I was unable to find a complete listing that shows when the floodgates have been closed.
2. Several photographs were shared with the Preserving York group on Facebook that show York during the 1933 flood.