A Tale of Two Fields

A Tale of Two Fields: Getting the drainage right in athletic fields

By Emily Weckman

A hole in the soccer field to monitor water infiltration.

An example infiltration hole to show stratification of soil layers.

To test or not to test? That is the question.

When it comes to athletic field drainage, however, there is only one answer—yes, always test! During the early investigative and conceptual stages of field design, infiltration testing of the soils and subsoils is often neglected. A thorough, early understanding of existing soils—through the use of “infiltration holes”—can heavily inform future design and budget decisions. Infiltration holes allow the designer to observe and record the depths of the various soil layers and also record the infiltration rates of each. When executed correctly, infiltration holes minimally impact a field while at the same time providing a tremendous amount of insight into the existing soil conditions. In fact, most fields can be played on the next day. The findings from these tests help the design team determine if a sports field’s cross section needs to include a costly underdrain system or if the existing material can perform as needed.

To get more background on this concept, let’s compare two recent field-renovation projects that involved varying design approaches based on early soil investigations.

Scenario #1: A Surface-Level Issue

The first scenario involves a field-renovation and realignment design for a heavily used baseball field. From the outset of the project, local stakeholders expressed concern regarding the way the field drained, raising an immediate red flag. Were the drainage issues strictly superficial or was the cause rooted in the composition of the soil and subgrade? The design team reviewed historical plans for drainage patterns, assessed the updated survey and contours, and identified several areas for the investigative infiltration holes.

An employee taking a soil sample in a sport field to test infiltration.

Team member executing a double ring infiltrometer field test to investigate infiltration at the topsoil layer.

The team then set out to complete six infiltration holes in various locations within the boundary of the proposed realigned field. Since the proposed design included shifting the field 60 feet to the northeast, it was imperative to identify infiltration-hole locations that would accurately represent conditions in each area of the new field location, such as the grassed diamond and outfield and the infield and outfield skins.

At each location, the team recorded infiltration rates at each soil strata to see if there were any restrictive layers. The team discovered 6-12 inches of topsoil followed by 2-17 inches of sand and then a gravel layer. Based on the different soil layers, the infiltration rates at two inches into the sand layer and at 30 inches deep in the gravel subgrade were observed. Testing of the sand and gravel subgrade layers yielded free draining results. The surface-soil layer was tested using a double-ring infiltrometer, which showed varying infiltration rates, ranging from 0.25 inch/ hour to over 8 inches/hour depending on the location. Low infiltration rates at the surface could be due to compaction, inadequate topsoil, or a combination of the two.

Based on these findings, the design team determined that, given the existing free draining sand and gravel subgrade layers, underdrains were not needed, and drainage improvements should be focused on improving the rootzone mixture and surface drainage. Based on field-performance expectations and maintenance budgets, targeted soil-performance criteria were determined by the ASTM F3339-20 “Standard Guide for Construction or Renovation of Native-soil Athletic Fields.” The soil tests showed the topsoil consisted of angular to sub-angular to sub-rounded fine sands that make the topsoil prone to compaction and reduced drainage rates. Blending the existing topsoil with 2-millimeter spec sand and performing standard cultural-maintenance practices should reduce susceptibility to compaction and provide better porosity for root growth, increased infiltration, and a quality surface for years to come.

Scenario #2: Deep-Rooted Problems

The second scenario involves the renovation of multipurpose baseball and softball fields with a multi-use overlay. Similar to scenario #1, the design team performed soil exploration during the early site-inventory phases after learning the existing field had exhibited frequent drainage issues that impacted its use.

A soil testing hole and pit that showed water was not draining properly.

Scenario #2: Infiltration hole (left) that showed restrictive layers, requiring the team to dig larger test pits (right).

However, unlike the first scenario, in which members of the team discovered a free-draining subgrade, they consistently encountered a restrictive layer under the topsoil down to 30 inches while digging investigative infiltration holes. Due to these findings, a contractor was enlisted to dig larger test pits to allow the team to better visualize, classify, and observe the soils and restrictive layers, such as groundwater, ledge, or hardpan.

The infiltration test holes and test pits revealed impermeable soil layers at depths ranging from one to six feet below grade. Existing topsoil tests also revealed very silty topsoil with very low permeability rates. Based on these results, the design team recommended both an underdrain system and an amended (or new) rootzone mix were necessary to provide the required drainage for the field to perform as desired. Based on field-performance expectations and maintenance budgets, targeted soil-performance criteria were determined by the ASTM F2396-11 “Standard Guide for Construction of High Performance Sand-Based Rootzones for Athletic Fields.”

Three years after installation, the performance and drainage of the fields are still exceeding designer and client expectations.

Topsoil Testing

A diagram showing an athletic field cross section with underdrain system.

This cross section illustrates a necessary but costly underdrain system that is needed when restrictive subsoils are discovered, like Scenario #2.

Following an evaluation of infiltration holes, topsoil should be collected and tested to determine if the existing topsoil/rootzone meets the recommended criteria. Soil testing for athletic fields goes beyond simply testing for organic matter and pH. Recommended soil testing for athletic fields provides an in-depth analysis of both physical and chemical properties of the existing soil. This information allows the design team to determine if the existing topsoil can be reused as is or reused if amended to meet performance specifications, or if an entirely new rootzone mix needs to be imported.

If the design calls for imported sand-based rootzone, then the “Athletic Field Rootzone” performance criteria are outlined in ASTM F2396-11 “High Performance Sand Based Rootzones for Athletic Fields.” If the existing topsoil can be reused, or if a true sand-based rootzone is not desired, then the guidance is outlined in ASTM F3339- 20 “Standard Guide for Construction or Renovation of Native-soil Athletic Fields.”

Recommended ASTM testing includes the following:

  • Physical Properties: ASTM F1815-11 for particle density and water holding.
  • Proctor Test with Percolation Rate: ASTM F1815-11 modified for compaction level per ASTM D 698-12 for the percolation rate of a soil that contains silt and clay without over-compacting it.
  • Particle Size Analysis: ASTM F1632- 03 for the textural components of sand, silt, and clay, but more importantly the sand distribution size.

Understanding Maintenance and Performance

A diagram showing an athletic field cross section with native soil.

This cross section can be explored when a sand subgrade and free-draining base are present, like Scenario #1.

Another crucial step to take in the inventory and investigative stages is to have a conversation with the client regarding the level of maintenance and irrigation that that can be supported and how that aligns with desired field-performance expectations. This conversation is paramount in order to avoid proposing an athletic field design that cannot be maintained. A sand-based rootzone athletic field provides superior performance, but this comes at a cost as it requires a high level of maintenance and irrigation.

In comparison, a native-soil rootzone typically has better water and nutrient-holding capacity, which requires less irrigation and is a great option to balance budget and performance if the soil can meet performance criteria.

While infiltration testing and maintenance conversations are imperative, they are two of many factors that are considered when designing athletic fields. It is recommended that an athletic field design professional be consulted to meet the needs of the site and performance expectations.

Get Out There and Get Dirty!

In conclusion, the best advice is to step away from the computer and get dirty digging infiltration holes. One day of determined field work has the potential to inform the team as to whether (and how much) costly new infrastructure may be needed for the proposed field to drain and perform.

Lessons Learned

It is imperative to perform infiltration-hole testing of topsoil and subgrades during the initial stages of design.

Data on the existing soil and subgrades will inform design decisions and their impacts on associated costs. This will relieve much consternation on the client’s part by minimizing the chances for future design changes.

Favorable soils can yield cost savings. However, unfavorable soils can inform the design team at an early stage about whether to budget for solutions like a costly underdrainage system and amended soil.

Discuss maintenance costs and capabilities with the client to determine if a sand-based or natural soil-based rootzone is desired.

  • A true sand-based rootzone will drain more than 10 inches per hour, which requires heavy field maintenance and watering.
  • Benefits: Turf roots can penetrate deep into the soil and provide superior durability and stability of the athletic turf.
  • Limitations: There are higher costs to import a sand-based rootzone mix and higher monthly irrigation costs.

A natural soil-based rootzone should drain two to four inches per hour depending on the subgrade.

  • Benefits: A natural soil-based rootzone allows for cost savings through the reuse of existing soil and requires less watering
  • Limitations: When compared to a sand-based rootzone, water does not infiltrate as quickly, which can lead to postponed games and higher risks of field damage.

Not all soil testing labs perform the required ASTM testing services. Make sure to specify the correct ASTM testing for the field conditions!


Emily Weckman, RLA, is a Senior Project Landscape Architect at Weston & Sampson’s Design Studio in Rocky Hill, Connecticut. She can be reached at weckman.emily@wseinc.com.

Published in PRB+ Magazine, April 2024.

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