Green Renovation Case Study No. 1

By Paul Campbell, Superintendent, Cottonwood Creek Golf Course and James Francis Moore, USGA Green Section, Construction Education Program
Submitted Feb. 13, 1998

The greens at the Cottonwood Creek Golf Course in Waco, Texas had been in poor condition for years. This was due to a combination of problems including:
  • less than ideal construction, resulting in poor internal drainage rates
  • irrigation with poor quality water
  • greens that were planted to bentgrass in a climate better suited to bermudagrass
  • a marginal maintenance budget which provided inadequate staffing for the maintenance of bentgrass in central Texas
  • greens that had shrunk over the years, greatly reducing the area available for hole locations
  • severe layering in the upper four inches of the soil profile as a result of topdressing practices and poor quality water
  • severe bermudagrass contamination (resulting from the lack of fumigation when the greens were converted to bentgrass years before)
Given the problems with the rootzone, the ideal fix would have been to completely reconstruct the greens to USGA guidelines. However, this option was judged economically infeasible by the staff and guidance committee. The next step was to investigate renovation.

First we needed to accurately determine the make-up of the rootzone in the existing greens. Core samples were collected and submitted to a physical soil testing laboratory for analysis. The test results confirmed our visual assessment that the upper four inches of the rootzone had become severely layered and contaminated with very fine particles (including silt and clay). As a result of the layering, the upper four inches of the greens were retaining a high percentage of water, resulting in a poor balance between air-filled and water-filled porosity. This also explained the very slow infiltration rates noticed during irrigation and rainfall events.

Fortunately, the make-up of the rootzone below the upper four inches was more favorable. Although it did not meet USGA guidelines and the sand was highly calcareous, we were hopeful we could modify the original material to make it more supportive of turf by blending it with a properly sized, silica sand. To determine if this was possible, we first removed a section of turf (about 1 foot square). We then removed the upper four inches of the rootzone. Next, we removed four inches more of the the rootzone, now drawing from the the original rootzone material that had not been affected by the layering. We then mixed one gallon of this original rootzone material with one gallon of a properly sized, silica sand that we could obtain locally. This sample was submitted for analysis to the laboratory.

This sampling procedure was a means to simulate the renovation effort we were considering. In lieu of complete reconstruction, we hoped to accomplish the following procedure.
  1. Remove the existing bentgrass sod.
  2. Remove the upper four inches of the existing rootzone.
  3. Add four inches of a properly sized silica sand.
  4. Thoroughly rototill the greens to a depth of eight inches.
  5. Compact and lightly contour the new rootzone to ensure surface drainage.
  6. Fumigate the greens to sterilize the rootzone.
  7. Reestablish the greens to Tifdwarf bermudagrass.
After studying the results of the laboratory analysis we realized that although the renovation procedure would not provide a rootzone that met the USGA's guidelines for green construction, we would be able to significantly improve the internal drainage of the existing greens.

In addition to modifying the rootzone, we planned to accomplish the following changes as well.
  • Recapture almost 40,000 square feet of putting surface that had been lost over the years as the greens shrunk due to mowing.
  • Change our water supply to reduce salt, sodium, and suspended solids contamination of the greens.
  • Improve surface drainage by some minor recontouring of a number of low, green areas.
  • Reposition irrigation heads to provide better coverage and install a new control system to allow better control.
  • Convert from bentgrass to bermudagrass, a much hardier turf for our area.
We felt that while it was unlikely any one of these improvements could give us the greens we wanted, the combination of all the improvements should allow us to reach our goal - greens that the citizenship of Waco could enjoy and afford to maintain.

The project was successfully completed by midsummer. Fourteen weeks after planting, the greens were reopened to play. Four weeks later, we held the Waco City Championship on the same greens. Thanks to a combination of a thoroughly researched plan, a conscientious contractor, a dedicated maintenance staff, and a supportive leadership, the project has been a success.

It is important for all who read this to realize that we would have much rather completely reconstructed our greens. This would have allowed us to construct a much better draining rootzone and make greater architectural changes to the green contouring. However, since this option was simply not available to us, we feel we took the next best step for our particular situation.

The following pictures and descriptions illustrate the step-by-step process as it was accomplished.

(1) One of the most important steps was to prepare good temporary putting surfaces. With Tifway 419 hybrid bermudagrass in the fairways, the combination of low cutting, plenty of topdressing and vertical mowing, and near daily mowing, allowed our players to enjoy the game during the renovation project.

(2) The edges of the existing greens were probed to determine how much they had grown in over the years. Next, a marking gun was used to outline the area to be renovated. Sod was then removed using a sod cutter. A box blade and a front-end loader were used to finish cleaning off the surface.

(3) The old rootzone was then excavated to a depth of four inches. While the box blade and loader combination was used to remove most of the mix and load it into a waiting truck, the edges of the green had to be excavated by hand.

(4) With the cavity cleared to the four-inch depth and the bottom smoothed, the new silica sand was brought in.

(5) A small track loader spread the sand to a uniform, four-inch depth. Notice the man checking sand depth with the probe.

(6) The new sand was then incorporated into the next four inches of the existing rootzone by tilling.The tiller went over the greens numerous times until the upper eight inches of the soil profile was as uniform as possible.

(7) The new rootzone mixture then repeatedly bladed to smooth and firm the surface.

(8) To reduce future settling as much as possible, the rootzone was irrigated and rolled.

(9) Surface contours were re-checked to ensure positive surface drainage and to maintain the original contours as much as possible.

(10) Final grading was accomplished using a modified mechanical sand rake and a steel drag mat.

(11) The next step was fumigation to eliminate weeds, insects, and foreign grasses. Methyl bromide was injected beneath plastic. The plastic was removed after 48 hours.

(12) Since the greens were to be replanted to Tifdwarf bermudagrass (a hybrid that does not produce viable seed), they had to be hand-sprigged. After spreading, the sprigs were pressed into the upper 1/2 inch of the rootzone using a small disk.

(13) Although very few weeds surfaced during grow-in, a close eye was kept for contamination from wind-blown sources. The first mowing took place about two weeks after sprigging, with the height set at 5/16 inch. The cut was lowered to 1/4 inch until complete coverage of the sprigs was obtained - approximately ten weeks following planting.

Cutting heights were lowered further to 3/16 inch and then to 5/32 inch just prior to the City Championship - 18 weeks after planting.

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