Drainage

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Soils

Soils mainly composed of clay or silt have a higher water-holding capacity. Their larger surface areas make it easier for the soil to hold onto water. If your backyard has clay or silt soil, you will have a higher chance of ponding and pooling. Increasing organic matter will help your soil retain water. The United States Department of Agriculture maintains an online Soil Survey that you can access to find out more about the soils where you live. How well-drained are they? How deep or shallow is the seasonally high water table? Is it prone to ponding or flooding?

Adding compost and manure and using native landscaping are all healthy ways to add organic matter to your soil. Please contact the University of Minnesota Soil Testing Laboratory if you want your soil tested. It is a great way to ensure fertile soil without excess fertilizer pollution and runoff.

What is a Drainage and Utility Easement?

Nearly every residential property contains a drainage and utility easement around the lot's perimeter. In many cases, there may be a drainage and utility easement elsewhere on the property. The homeowner owns the property within this easement; however, the city and utility companies are permitted to use the easement for drainage swales, storm sewers, water lines, or any other utility such as telephone, cable TV, gas, and electric lines.

Generally, the easement runs along the property line and is five feet wide on the sides and ten feet wide in the front and rear. The city recommends landscaping outside the easement. You cannot change the grade or place structures within the drainage and utility easement unless you have applied for and been granted an encroachment agreement. Remember that your plantings or any other improvements made within the easement could be damaged or removed if work needs to be done, and the landowner will bear any replacement costs.

Additionally, unless suited to wet conditions, trees and shrubs usually don’t do well in drainage swales and could create drainage problems if they impede the natural flow of water. Other easements could be located on your property.

If you need more clarification, call the City Engineering Department before planting a tree or shrub or grading your yard. Any grading in excess of 50 cubic yards or 5,000 square feet will require an earthwork permit.

Historic Maps

Historic Topographic Map

See what type of land your backyard is historically!

Historic Aerial Map

Carver County has developed several interactive GIS mapping applications that are available to the public. Their property information application has unique tools to allow you to compare your property currently to what it was like in 1979! Was it wooded, in agricultural production, or was it a wetland area? All you have to do is open the historic photography application and select the year you want to compare.

Backyard Drainage

Poor drainage could be caused by various sources that we have little or no control over, including but not limited to gradual grades or low-lying areas, clay or other tight soils, or shallow groundwater. In other cases, controllable causes may also contribute to drainage from impervious areas such as roofs, driveways, sidewalks or irrigation systems, pools, and sump pumps.

Tips to Improve Drainage Issues

View a printable version of these tips.

Position Runoff Appropriately

Make sure downspouts, pool drains, and sump pumps are directed away from structures like houses and garages and preferably toward vegetated areas that can quickly absorb runoff. Adjust your irrigation system for minimum run-time, and check for leaks or malfunctions.

Landscape Improvements

If you have a low-lying area in your yard that collects water that is only present for short periods (less than 10% of the growing season) and is at least ten feet from any structural foundations (basements, etc.), try turning this area into a garden or landscape feature with flood-tolerant plants. It may also be possible to capture the water higher up on the landscape and infiltrate it in a rain garden, thereby keeping the lower-lying area drier. The city does have small grants available to assist landowners who wish to install a rain garden on their property. Often, the watershed district does as well.

Amend Soils

Soils with high clay content cannot absorb water (infiltrate) quickly, leaving puddles that last for hours. If your soil is high in clay content, add organic matter to your soil. This will help water absorb into the ground more quickly. Covering areas with high clay content with organic materials such as compost or ground wood chips as mulch will also increase organic matter content over the years and soften the soil, allowing for increased infiltration.

Suitable Plants

Plants such as typical turf grass and many ornamentals normally do not thrive in poor drainage areas. However, numerous trees, shrubs, grasses, and flowering plants thrive in poorly drained areas. Some of these include swamp white oak, river birch, American larch, red-osier dogwood, black choke cherry, buttonbush, high bush cranberry, several varieties of aster, butterfly milkweed, prairie cord grass, little blue stem, and many more. Look for rain garden workshops hosted by the city or Watershed District and presented by Metro Blooms. Some sources for suitable plants include Plants for Stormwater Design and WSB Guide to Rain Gardens.

Flooding

The National Weather Service regularly issues an updated spring flood outlook for locations across the upper Midwest, including Carver County. Above-normal rainfall and snowfall may lead to potential flooding along many rivers, including the Minnesota River.

Flood Insurance

Carver County Emergency Management reminds residents and businesses in Carver County that flood insurance is available in the primary flood-prone areas of the county.

Flood insurance becomes effective 30 days after it is purchased. Contact your insurance agent for details or information on the National Flood Insurance Program. For tips on flood preparation, visit the FloodSmart National Flood Insurance website.

Contact Carver County Emergency Management at (952)361-1528 if you have questions or need further assistance.

Federal Emergency Management Agency

The Federal Emergency Management Agency (FEMA) coordinates the federal government's role in preparing for, preventing, mitigating the effects of, responding to, and recovering from all domestic disasters, whether natural or artificial, including acts of terror. FEMA’s mission is to build, sustain, and improve the Nation’s capability to prepare for, protect against, respond to, recover from, and mitigate all hazards. FEMA also administers the National Flood Insurance Program (NFIP), which works with private insurance companies to offer flood insurance to property owners and renters if their community participates in the NFIP. As a participating community, the City of Chanhassen has agreed to adopt and enforce ordinances that meet or exceed FEMA requirements. These ordinances can be found in Chapter 20, Article 5 of the City Code.

Chanhassen Floodplain Map

FEMA offers an interactive map that you create yourself online. Flood Insurance Rate Map (FIRM) allows you to print at the comfort of your home. FIRMette maps are free to create and print.

Flooding Resources

Sump Pumps

Connections

Sump pumps are not allowed to be discharged directly or indirectly into the sanitary sewer system. Sump pumps also may not be discharged into any public right-of-way. All discharge piping shall be installed in accordance with Section 19-44 of the Chanhassen City Code for more information.

Connecting French drains, roof gutter drains, or foundation drains to your sanitary sewer is also illegal. Consult a plumber to correct any illegal connections.

Improperly connected sump pumps cause a significant problem because clean water goes to the wrong place. Rainwater can be directed into the sanitary sewer line if your sump pump is improperly connected. When rainwater, groundwater, or snow melt enters the wastewater treatment system, it is known as inflow/infiltration. When this clear water enters the sanitary sewer system, it overloads the capacity and can create backflow, flooding basements or causing maintenance holes to pop open.

For connection questions, contact:

Brett Martinson, Sewer/Water Maintenance Foreman

(952) 227-1311
Email

Discharge

If you are experiencing drainage issues, the location of your sump pump discharge may be a contributing factor. Make sure sump pumps are directed away from structures like houses and garages and preferably toward vegetated areas that can quickly absorb discharge. Consider neighboring property when directing discharge as well. Use existing drainage patterns to carry the water away.

A sump pump may not be discharged such that it creates a nuisance condition or a public safety concern, such as when it is discharged in a manner that will result in icy conditions.

For discharge questions, contact:

Joe Seidl, Water Resources Engineer

(952) 227-1168
Email

Drainage Issues

If you are experiencing issues with drainage, please follow the link to Tips to Improve Drainage Issues.

Typical Designs for Drain Tile and Sump Pumps

In many cases, the city has installed drain tile at the back of the curb of city streets. Chanhassen residents can make a “soft” connection to the drain tile, as shown in the Typical Sump Pump Drain Connection below (if available in your neighborhood). Details can be found on the City’s Standard Specification and Detail Plates page.