1. What is a french drain and what is it designed to do?

A french drain is a near-surface drainage system that is designed to increase the overall infiltration rate of the surrounding area and is used primarily to fix wet yard problems. The system consists of an excavation approximately 8 to 16 inches deep, a filter fabric lining, a 2-inch base of gravel, a 4-inch perforated pipe with protective fabric, and gravel surrounding the perforated pipe.

The french drain can be topped with gravel for a high infiltration rate or with sod to hide it beneath the lawn.

The higher the clay content in the soil, the lower the general infiltration rate. Wet yard problems are commonly caused by a combination of clayey soil, a level ground surface, and a high groundwater table.

French drains are not meant to handle and are not designed for stormwater drainage.

2. What’s the best way to handle stormwater drainage?

Preferably with a series of swales and/or berms. A swale is a relatively shallow linear depression in the ground surface designed to direct stormwater away from structures. A berm is a relatively small rise in the ground surface that protects a structure by preventing stormwater from flowing towards it.

3. My foundation walls appear to be water-stained. What causes this?

Excess moisture in foundation walls is generally cause by one of three things: (1) surface water infiltration, (2) groundwater infiltration, and (3) a broken exterior pipe.

Moist walls caused by surface water infiltration can be spotted fairly easily by the staining pattern. In most cases, the water infiltrating down along the foundation wall is coming from a gutter downspout that is dumping water right next to the foundation. The stain pattern in this case is typically a 45-degree downward angle from the water source.

The most common misdiagnosed problem is the surface water infiltration problem. Very often we are asked by homeowners to inspect their basement or crawl space after a “waterproofing contractor” has provided them a quote for the installation of an interior perimeter drainage system (sometimes referred to as a “french drain”). In the case of a surface water infiltration problem, this type of solution is not the correct one for many reasons, but mostly due to the lack of understanding of the source of the water and how to deal with it.

4. My basement flooded, why did this happen?

A flooded basement is typically caused by a rising groundwater table, severe negative drainage conditions, a clogged or inadequate drain next to a basement door, or a combination of these three.

The solutions for each of these are very different and a design professional should analyze your particular situation and prepare a remedial design that takes into account the various water infiltration sources.

5. What is Stormwater Runoff?

Stormwater runoff occurs when rain or melted snow flows over the ground and is not readily absorbed. Impervious surfaces like driveways, sidewalks, and streets prevent stormwater from naturally soaking into the ground. Instead, the water is channeled into our storm drain system; from there, it is carried directly to streams, ponds, lakes and rivers.

6. Why is Stormwater Runoff a Problem?

So, stormwater runoff is carried through the storm drain system—it gets treated before it’s released into our water resources, right? WRONG! Sanitary sewer systems carry household water to large facilities where it is treated. Water that flows into storm drains and sewers flows UNTREATED, directly to streams, ponds, lakes and rivers. This runoff carries with it pollutants that damage our natural environment and can be harmful to humans, plants and animals.

7. What Are the Effects of Stormwater Runoff?

Stormwater runoff can have many adverse effects on plants, animals, fish and people.

• Sediment (soil particles) can cloud water and make it difficult or impossible for plants and fish to survive.
• Debris and trash can entangle animals, birds and fish causing serious injury or death!
• Excessive nutrients from fertilizer and animal waste can cause algae blooms. When the algae die, they decompose in a process that removes oxygen essential to the survival of fish and plants.
• Waste such as oil, grease and chemicals from lawns and auto care get washed into recreational swimming areas and can make humans and animals sick!
• Pet waste that is not picked up washes bacteria (even parasites such as various types of worms!) into our recreational and drinking water and can cause serious illnesses in humans & animals!

8. What Are Some of the Typical Pollutants That End up in Storm Drains?

• Antifreeze, motor oil and gasoline
• Paint, stains and solvents
• Fertilizer, pesticides, insecticides & herbicides
• Pet waste
• Trash and debris
• Dirt, leaves and grass
• Soil and sediment from bare land
• Household chemicals, such as every-day cleaning supplies

9. Why is this My Problem?

Keeping pollution out of storm drains not only helps the environment, but saves YOU money. Cleanup efforts are big strains on tax dollars. Minimizing pollution means minimizing cleanup costs and saving your tax dollars for other programs in the community.

10. What Can I Do?

By making a few small changes, YOU can help reduce stormwater pollution!

• Prevent sediment loss from your property with proper drainage systems and vegetation.
• Don’t hose down sidewalks and driveways—sweep up with a broom instead.
• Pick up after your pet—bag waste and put it in the trash or flush it down the toilet.
• Use fertilizer only as needed—avoid fertilizing right before a rainy day.
• If you work on your car, clean up spills immediately with rags and dispose of contaminated materials properly.
• Don’t rinse paint brushes outside where leftover paint can flow into drains.
• Use car washes that recycle used water.
• Repair auto fluid leaks immediately!
• Report illegal dumping—only rain belongs in the drain! Dumping of paint, motor oil, yard waste and other items in storm drains harms our water resources and is illegal!
Drainage & Erosion Solutions LLC
2755  Greenway Blvd
Falls Church, VA  22042