In 2025, staff completed their third year of conducting soil assessments across the District. This year, we focused on greatly increasing the amount of residential lawn assessments conducted.  Thank you to the 16 residents who participated in our Residential Lawn Program this year!

As we review the data, we will determine if there’s a need for more residential lawn assessments. Keep an eye out for future opportunities to collaborate with the District on soil health!

Learn more about the District's Soil Health Study.

The Importance of Assessing Lawns

Lawns comprise approximately 40 percent of land area in the District. These lawns used to be native forests, prairies, and savannas - undisturbed by humans. Over time, humans have influenced the landscape through development. Turf grass has replaced native plants in many developed residential areas. Heavy construction equipment used in development compacts and mixes soil.  This causes lawns to have an altered hydrology. Altered hydrology is the change in how water moves in the watershed due to human influence.

Lawns have an altered hydrology. This can lead to negative impacts on our ecosystem, including increased runoff into our waterbodies and decreased water storage capacity. All our small, individual lawns add up to a lot of turf, potentially yielding more than five times the amount of runoff produced by the natural ecosystems once in the landscape. Additionally, lawns consume significant resources such as water via irrigation, and fuel for mowing and other maintenance. Lawn fertilizers add an excess of nutrients such as phosphorus and nitrogen to the landscape. This negatively impacts the lakes and streams receiving that runoff.

The District is exploring ways we can improve soil health in lawns. Lawns have potential for stormwater capture and runoff reduction. The soils underneath lawns play a large role in that. Little research exists on lawn soil function and management. The District is conducting the Residential Lawn Program to bridge that research gap. We will use results from this study to provide solutions and improve lawn soil health.

Data Collection Procedures

Soil assessments of your lawn can be completed within 1-2 workdays. They are free, minimally invasive, and completed entirely by District staff. After completing our sign-up form, we will decide if your property is a suitable candidate for assessment. Suitability is determined by the accessibility and amount of lawn on your property. This might involve assessing your property in person.

We will notify you within a week of submission via email whether we can assess your property or not. If we can assess your property, we will provide a proposed map of sample points and set up a date and time to visit your property. Additionally, staff will contact Gopher State One Call on your behalf to mark underground utilities. Please let staff know about other utilities Gopher State One Call might not mark (ex. sprinkler systems) via email or during the on-site visit. District soil assessments consist of two main components: infiltration testing and soil sampling. Below is more information about our specific data collection procedures for these components.

Infiltration Testing

Staff conduct infiltration testing using a Modified Philip Dunne (MPD) infiltrometer. This device automatically measures and records infiltration rates and hydraulic conductivity. Hydraulic conductivity is the infiltration rate once the soil is 100% saturated and the infiltration rate is constant. This data helps identify areas with more capacity for capturing and storing stormwater.

At each sample point, three 4-inch diameter cylinders are pounded into the ground at a 3-foot radius of a center point. Depending on the focus of the assessment, they will be driven into the ground just below the surface, or 12 inches from the surface.  After each cylinder is in the ground, staff turn on a sample head fitted with a pressure sensor that will sit on top of the cylinder and collect data. These cylinder heads connect to a wireless tablet which records the hydraulic conductivity data measured by the sensor in the head. Each cylinder is filled with a minimum of 30cm of water and the head is placed onto the cylinder. Once the head is in place, the test must be immediately started manually using the tablet. Automatic measurements are then taken as the water drains from the cylinder.  Once the cylinders are completely drained, or 30 minutes have passed, staff stop the tests. They remove and clean the cylinders, data is saved, and staff replace the soil and sod.

Soil Sampling

Soil sample data helps staff identify how soil functions differ across different land uses. This includes measuring and comparing the soil’s biological, chemical and physical properties across these land uses. These measurements show us how well the soil is functioning. Greater soil function leads to better stormwater capture, and healthier vegetative communities.

Soil sampling consists of collecting several 6" x 6” x 2" subsamples from below the surface. This can either be 8" below the surface or 18" below the surface. 

At each point, two sub-samples are taken within a 15-foot radius. The distance between pairs of subsample points depends on the size of the assessment area. Staff also take penetrometer readings at different depths for each of these subsamples. Penetrometer readings measure how compacted soil is. After staff collect sub-samples, they mix them to form a composite sample. These composite samples are sent to the Cornell University Soils Lab for analysis.  

At Cornell, scientists analyze samples for different properties. Soil texture composition, the proportion of sand, silt, and clay particles within the sample, is also measured.

Resources

For more information about District soil monitoring, read the report:

Check out the District's basic guide to soil health:

FAQs