GREEN CASTLE as a public park will soon be 40 years old. To help celebrate, you all are welcome to join in activities, good food, visit with friends, go hiking, fishing, paddle around the 16 acre lake in a canoe or kayak, play volleyball at a newly installed deep sand court, and listen to music. The date is Aug. 5 beginning mid afternoon until after dark. This is one of many Marshall County Conservation Board managed areas but it is undoubtedly a major site for people who love outdoor activities, fresh air, good views and a bit of native wildlife. A hike around the lake is about one mile long, good exercise indeed to those who want a natural site for walking.

It was during 1967 that the details of a pending land sale were worked out with the Zesch family. On January 1, 1977, possession of the 116.5 acre land parcel became Marshall County property. A 16-acre lake was already present. What was envisioned was a long range plan to make facilities, park access roadways and silt retention ponds as starters in the development process. It took a long time, many budget years, and slow steady progress to bring the land, lake, its dam and wildlife viewing areas available for the public.

Three open air shelter houses were built and they were named North Bay, Gander Lookout and Handicove. Several years ago Gander Lookout was rebuilt and remodeled to enclose its walls from the weather and add improvements to the its outside deck. The interior is now paneled in native wood from salvaged Marshall County forests. Gander Lookout will the focus point for the 40th anniversary celebration. This shelter house may be reserved for family functions, graduations, weddings or reunions. Call 641-752-5490 for details.

The dam holding back the waters of the 16 surface acre lake was renovated in the 1980s. This very detailed engineering project was required to bring the dam into compliance with safety standards by adding substantial amounts of carefully compacted soil to its backslope and to raise the height of the dam, not the water in the lake, but just the amount of extra strength to allow for a stronger structure. A new 36-inch diameter overflow spillway tube was installed that begins at the base of a large diameter vertical drop tube. The size of these large pipes were sized to be able to handle heavier than normal rainfall events, infrequent as they are, as insurance against too much water being held back with in the lake basin. In addition, a special draw down tube device is in place that allows for a bronze control gate to be opened for water release at times when lake draw downs are necessary.

One of the unseen special engineering features is a bentonite clay filled trench at the base of the dam. This trench dug through a somewhat sandy loam soil that previously had a ‘slow leak’ factor. Bentonite clay from Wyoming has a special quality in that when it absorbs water, it swells to over ten times its original volume. In so doing, it forces itself into all surrounding underground pore spaces and seals it against ground water pass through.

In 2014, a major water draw down took place. Water from the lake was allowed to exit so that only a very low level and much reduced volume remained. This concentrated the remaining fish including common carp which had ruined the existing fishery. In consult with DNR fisheries biologists, at the right time, rotenone poison was added to kill all remaining fish. This periodic ‘start over’ tactic is sometimes the best solution for a lake with fish populations so out of balance that no one benefits.

While the lake water was extremely low, a huge undertaking of silt removal took place. Shorelines were steepened, islands built, a whole lot of new fish habitat structures were installed and built along every exposed shoreline. New jetties were built and stone added to their outlines to break up wave action from wind. Once this work was finished, the control valve on the spillway tube was closed. Slowly over the fall and winter, snow melt and new rains brought new water back into the lake basin. Now all the fish habitat structures are submerged and holding new stockings of bass, bluegill, crappie and catfish. To assist the fishermen and ladies to gain access for fishing, a policy change allowed canoes/kayaks or other non-powered water craft via a concrete boat ramp located near the Handicove shelter house.

Three small ponds, called silt catch basins, were constructed over the decades. Two of them are integral to the park roadway system. Water trying to enter the main lake has to first pass into a catch basin pond. Then its waters can more slowly filter out into the main lake. Any silt is deposited into the catch basin. One of these ponds to the south end of the park is home to a Trumpeter Swan pair. In the past, several broods of cygnets have been raised here. They eventually became free flying birds to travel wherever they so desired.

Next to this pond is an enclosed pasture that holds a small herd of bison. A new and improved fence keeps the bison inside their territory. Public viewing opportunities are easily found near the bison hay barn or around and close to the observatory. The observatory was built by Amateur Astronomers of Central Iowa. There project needed a place far away from city lights. A dark night-time sky was available at the hill top at Green Castle. Numerous programs for watching stars or other celestial events have been conducted at the observatory.

Any park is going to have trees and bushes. Lots of them were already at the site in 1977. More were planted over time. And native prairie grass seed mixes were also planted into former crop fields. Part of these open grassland zones have been regraded into large terrace complexes for future RV camping development. This feature is part of Green Castle’s long range plans.

You are invited to come to Green Castle on Aug. 5, beginning at 2 p.m. or whenever your arrive later that afternoon. Good people, good food, good music, good times and a day spent outside will be your gain during the 40th anniversary celebration of this very nice park. See you there.

——–

Garry Brandenburg is a graduate of Iowa State University with BS degree in Fish & Wildlife Biology. He is the retired director of the Marshall County Conservation Board. Contact him at P.O. Box 96, Albion, IA 50005.