Urban Home*A*Syst - Site Assessment

Is your soil sandy or gravelly? Does it drain quickly? Does storm water runoff from your property flow into a nearby lake or pond? Do you store hazardous chemicals on your homesite?

This chapter will help you become familiar with your homesite and how you manage it so you can identify risks to water resources. Completing the chapter will provide background information you can use throughout this book. This chapter covers two areas:

Examples of characteristics include soil type; depth to bedrock; depth to the water table; and location of storm drains, creeks, streams or other pathways to surface water.

A map of your homesite showing buildings, roads and other constructed or natural features can help you identify potential sources of trouble.

What you do in and around your home can affect water quality both below the ground and in nearby lakes and streams. This chapter will help you identify some important characteristics of your homesite such as soil type, geology, depth to groundwater and nearness to surface water.

It also invites you to draw a simple "aerial view" map of your homesite. Your completed map will show the locations of important features and help you identify activities in and around your home that may pose risks to your health and the environment. Remember – this assessment is a starting point. It is meant to encourage you to complete some, or all, of the other Urban Home*A*Syst chapters. To begin thinking about how your activities and site conditions can harm water quality, see the figure on page 11 for some examples of practices that can lead to water pollution.

The water from your tap and in nearby lakes or streams is part of a much larger water system. While not everyone lives next to a pond or stream, we all live in a watershed — the land area that contributes water to a specific surface water body, such as a pond, lake, wetland or river. The landscape’s hills and valleys define the watershed, or "catchment" area.

A watershed is like a bathtub. The watershed outlet – the mouth of a pond, lake or river – is the tub’s drain. The watershed boundary is the tub’s rim. The watershed’s drainage system consists of a network of rivers, streams, constructed channels and storm drains, wetlands and the underlying groundwater.

Common activities like fertilizing your lawn and garden can affect water quality, even when you do these things far from any water bodies. By paying careful attention to how you manage activities in and around your home, you can protect your watershed and the water you drink.

Understanding the site characteristics of your residence and the location of potential contamination sources are important first steps in safeguarding your water. In the hydrologic cycle, water moves through the air, over land and through the soil. Activities in the watershed can affect groundwater, stream and lake quality at lower elevations in the watershed.

Physical characteristics, like soil type, depth to groundwater and distance to surface water, may hasten or limit a contaminant’s affect on water quality.

Water quality is also affected by many activities such as the use and storage of household chemicals, fertilizers, pesticides and automotive fluids, waste disposal methods and soil erosion. Animal wastes can be another threat to water quality, particularly if large amounts from dogs or other animals are allowed to accumulate on your property. To protect your water, all of these factors need to be considered.

Every home comes with its own unique set of physical site conditions such as soil type, depth to the water table (groundwater) and depth to bedrock. These physical conditions cannot be changed, but once aware of them, homeowners can better understand risks that may result from activities that can be changed.

Soil plays an important role in determining where contaminants go and how water moves. Chemicals applied to a lawn, for example, can flow across the land into storm drains and reach surface water supplies. On the other hand, the same lawn chemicals may soak into the ground and move down through the soil into groundwater supplies. It becomes easy to see how typical household activities can produce problems that go beyond property boundaries as pollutants can be transported through surface runoff and leaching.

It is also important to recognize that groundwater and surface water are interconnected. Groundwater generally flows downhill, following the same path as surface water, and eventually discharges into rivers, lakes, springs and wetlands. If you keep pollutants out of surface water, but do not protect groundwater – or vice versa – contamination may occur where you least expect.

To better understand how water contamination can occur, let’s examine some physical site conditions which can affect the risk for ground and surface water quality.

Soil is composed of mineral particles, organic matter (decomposed plants and animals), microorganisms (bacteria, protozoans, fungi and worms), water and air. Typically, soils are classified by the relative amounts of the three mineral particle sizes – sand, silt and clay. Fine soils (clays, silty clays and sandy clays) have a high percentage of the tiniest mineral particles – clay. Medium soil types (loams, clay loams, silt loams and sandy loams) are composed of a mixture of small (clay), medium (silt) and large (sand) mineral particle sizes. A coarse soil type (loamy sands and sands) is predominantly composed of sand, the largest particles. You can get a good idea about your soil type by rubbing a moist sample between your fingers. Is it sticky like clay, gritty and crumbly like sand or somewhere in between like one of the loams?

Nearly all soils are permeable – which means water and other fluids can percolate or seep through them.

Soil particle size influences which pollutants are able to reach groundwater. Some soils are better at trapping pollutants than others. Clay soils, which are made of tiny particles, slow down the movement of water and in some cases can impede water movement completely. Sandy soils pose the greatest risk because water seeps downward through them readily without filtering out or decomposing pollutants. The ideal soil is a mix of large and mid-sized particles to allow infiltration and tiny particles, like clay or organic matter, to slow water movement and filter pollutants.

Soil type can also affect surface water contamination. Although runoff can occur on all soil types, clay soils (which are least permeable) are more likely to cause surface water runoff. During a storm or flood, or even when watering your lawn, this runoff can wash contaminants from the land’s surface into nearby surface waters. Eroding soil is also considered a water pollutant. Bare soil, especially on sloping land, can be carried in runoff and be deposited in streams, rivers and lakes.

Bedrock depth varies; it can be at the land’s surface, just below the surface or hundreds of feet down. The type of bedrock influences pollution risks. Shale, granites and other impermeable types of rock make an effective barrier that blocks the downward movement of water contaminants. In Northwest Arkansas, our limestone geology weathers easily and forms cracks, fractures, caves and sinkholes, allowing water to move freely into our groundwater. When bedrock is split or fractures, water can move through it unpredictably, spreading pollutants rapidly over long distances.

If you dig a hole, you will eventually reach soil saturated with water. This water table marks the boundary between the unsaturated soil (where pore spaces between soil or rock contain air, roots, soil organisms and some water) and the saturated soil (where water fills all the pore spaces). In a wetland, the water table is at or just below the surface.

Your local water table fluctuates throughout the year but is usually highest in the wet months of spring and in late fall. In general, the closer the water table is to the land’s surface, the more the groundwater is susceptible to contamination. Deep soils offer a better chance of filtering or breaking down pollutants before they reach groundwater. Usually, a water table that is less than 10 feet from the surface presents a higher risk for groundwater contamination. Generally, soils that are less than 3 feet deep present the highest risk for groundwater. Groundwater is the water below the surface of the earth that, from the water table down, saturates the spaces between soil particles or fills in the cracks in underlying bedrock.

The table on page 15 is similar to the assessment tables in the other Urban Home*A*Syst chapters. For each question, three choices are given that describe situations or activities that could lead to high, medium and low risks to human or environmental health. Do the best you can. Some choices may not exactly fit your situation, so mark the best response that fits. Mark your risk level (low, medium or high) in the right-hand column.

Assessing Environmental Risk Based on Physical Site Conditions
	Low Risk	Medium Risk	High Risk	Your Risk
Soil type and risks to surface water (creeks, river, lakes) from runoff	Sand / gravel (large particles)	Silt / loam (mid-size particles)	Clay (very tiny particles)	Low Medium High
Soil type and risks to groundwater from infiltration	Clay (very tiny particles)	Silt / loam (mid-size particles)	Sand / gravel (large/particles)	Low Medium High
Soil depth	Deep (over 12 feet)	Moderately deep (3 - 12 feet)	Shallow (less than 3 feet)	Low Medium High
Bedrock	Solid, not permeable or fractured	Solid limestone or sandstone	Fractured bedrock (any kind)	Low Medium High
Depth to water table	Over 20 feet	10 - 20 feet	Less than 10 feet	Low Medium High
Proximity to surface water	Over 100 feet	25 - 100 feet	Less than 25 feet	Low Medium High

Do not depend solely on the physical characteristics of your soil, bedrock or other site features to protect water quality. You must take informed steps to prevent polluttion. Although you cannot change your soil type or the depth to bedrock, you can account for these factors when choosing home management practices that are better for preventing environmental problems. Especially note the medium and high risks you identified. Keep them in mind as you complete your homesite map and work on other Urban Home*A*Syst chapters.

By drawing a map of your homesite, you will take another step toward more fully understanding your pollution risks. Although your property has physical features you cannot change, there are many things that you can do to minimize risks.

Your map will identify areas where you can focus your efforts. It will also help you complete other Urban Home*A*Syst chapters. And if you involve children as you make your map and conduct the assessment, you will help teach them the importance of having clean water.

The materials you need to make your map are readily available: a measuring tape, a clipboard, a pencil and grid (page 18). The map you create will be an aerial view—the way your property would look if you took a photo of it from the air. A sample map is provided on page 17 and grid on page 18. Several home management practices and home site characteristics could have major effects on water quality. As you survey your property to make your map, be especially watchful for the following:

On your map, note the areas where you store and use chemicals and other potential hazards by using letter codes. Make up your own code letters or symbols as needed. Examples are:

For larger-view maps, add landscape features such as hills, rivers and ponds and human-built features such as runoff drainways, roads and bridges. Note potential sources of contamination beyond the boundaries of your property such as farm fields, dumps and gas stations. Indicate seasonal changes at your homesite. For example, are there wet areas in the spring? Such areas might indicate a high water table.

Inquire about previous or current industrial or agricultural activities in the area. Check with your town or city hall for information. Old landfills and buried fuel tanks are just a few examples of what you might find. Determine if any underground fuel tanks exist on neighboring properties.

The final step is to put both pieces of your assessment together – the assessment table results and map – so you can identify potential problem areas on your property. If you have rated any of the items in the table as medium or high risks and have identified potential contamination sources, then you should be concerned.

If you identify potentially hazardous or unsafe situations, what should you do? There are six other chapters in this Home*A*Syst handbook that address specific concerns. For example, Chapter 5 on automotive products contains information on the safe management of gasoline, heating oil, diesel and other fuels. These chapters and others will help you identify problems and develop an action plan for protecting your family’s health and the local environment.

This Urban Home*A*Syst handbook covers a variety of topics to help homeowners examine and address their most important environmental concerns. See the complete list of chapters in the table of contents at the beginning of this handbook. For more information about topics covered in Urban Home*A*Syst, Home*A*Syst and Farm*A*Syst, or for information about laws and regulations specific to your area, contact the Washington County Extension office 444-1755.

Sample Map

– Property boundaries

– House and garage

– Outbuildings, sheds

– Gutter down spouts

– Nearest surface water

– Roads, driveways

– Drainage ditches

– Impervious surfaces (such as patios or sidewalks)

– Lawn areas

– Vegetable and flower gardens

– Animal waste storage areas

– Nearest storm drain

– Slope/drainage direction

30 feet

Property boundary

A = automotive products

P = pesticides, herbicides

H = hazardous products

F = liquid fuel

W = Animal waste

/// = impervious surface

‡ = slope/drainage direction

O = downspout from gutters

Pictures of chickens, flowers, wheat, a boy looking through a magnifying glass, irrigation pipe, soybean pods, and fruits and vegetables.	Cooperative Extension Service





Cooperative Extension Service	Agricultural Experiment Station
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Washington County Urban Home*A*Syst Site Assessment

Washington County
Urban HomeASyst
Site Assessment