Department of Public Works - Highways
Welcome to the Department of Public Works Rain Garden Resource Page. We have assembled the following material to assist you with your rain garden project.
Imitating Nature with Rain Gardens
Leaving or creating depressions in the landscape promotes stormwater infiltration and reduces stormwater runoff. Take a walk through a forested area and you'll notice knolls and swales. Shaping the land in this fashion imitates nature by creating contours throughout the landscape, which allows rainwater to soak into the ground—as nature intended. The human tendency is to level the landscape, unaware of the environmental impact of this type of grading.
Rain gardens are simply low-lying, vegetated depressions--generally 3 to 6 inches deep--which have absorbent soils that temporarily collect stormwater runoff from impervious surfaces and allow the runoff to slowly percolate into the soil. Rain gardens are attractive landscaping features that function like a natural moist garden, moist meadow, or light forest ecosystem. They can look as informal or as formal as you like. While rain garden dimensions vary, remember, any size rain garden is better than no rain garden.
Rain gardens provide flood control, groundwater recharge, and water-cooling benefits, while the plants, soils, and associated microorganisms remove many types of pollutants—such as excess nutrients, pesticides, oils, metals, and other contaminants—from stormwater runoff. Stormwater pouring off hot roofs, pavement, and other impervious surfaces is temporarily captured, cooled, and allowed to percolate into the ground. Nutrients such as nitrogen and phosphorus, which would otherwise contribute to algae blooms and other problems in the Bay, are instead put to beneficial use by being taken up by the plants in the garden. Some studies show that about 50 percent of such pollution comes from individuals and homeowners, through yard care, yard waste, and chemical pollution from household activities.
Native plant rain gardens also become wildlife oases with colors, fragrances, and the sights and sounds of songbirds and butterflies regularly visiting. Additionally, rain gardens increase groundwater supplies, significant because many people get their water from underground aquifers. The replenishment of groundwater—which is particularly important in times of drought—depends on the absorption of rainwater into the ground.
By creating rain gardens and keeping most of the rain that falls on your site contained on site--the way nature intended—you can help improve water quality in local streams and rivers and ultimately the Chesapeake Bay. Native trees, shrubs, and herbaceous perennials improve the ability of water to filter down and recharge groundwater supplies, unlike turf grass, which tends to form a partially impervious barrier to water infiltration.
Notably, a rain garden is a type of bioretention installation, however, "bioretention" often refers to installations that are designed and engineered to be more complex than home rain gardens in order to mitigate larger amounts of runoff. They are deeper and typically incorporate underdrains.
CHECKLIST FOR RAIN GARDEN INSTALLATIONS IN ANNE ARUNDEL COUNTY
ITEM 1: Determine If Your Rain Garden Will Be On Private Or Public Property
* You may not need to perform this investigation if you are clearly working within your lot lines*
- Review your property survey
- Information Counter - Second Floor, 2662 Riva Road, Heritage Office Complex, Annapolis, MD 21401
Hours 7:30 a.m. to 3:45 p.m. Monday - Friday
Phone (410) 222-7049, Fax (410) 222-4579
Additional sources of information:
- Rights-of-Way: “Right-of-way” means the area across, along, beneath, in, on, over, under, upon, or within the dedicated alleys, boulevards, lanes, roads, sidewalks, and streets owned or maintained by the County. The “right-of-way” is used by many stakeholders and includes water, sewer, electric, gas, phone, catv, fiber, liquid petroleum, and storm water facilities. Driveways, inlets, sidewalks, gatehouses, mailboxes, telephone poles, switch boxes, community signs, and other surface structures also occupy the right-of-way. New development, utility upgrades, and road reconstruction mean the right-of-way is an ever changing environment. It is not possible for the County to guarantee the future use of the right-of-way.
Easements: In some cases storm drain inlets or other storm water infrastructure are located on private property but within an easement granted to Anne Arundel County. If a project will affect County infrastructure, review and approval needs to be obtained from the Department of Public Works. The right-of-way permit process is to be used to accomplish this review and approval.
ITEM 2: Determine Site Feasibility
- Rain gardens must be a minimum of 10 feet away from dwelling foundations and 50 feet from wells
- Rain gardens are not to be placed in a septic drain field, under a large tree, or on slopes of 12% or greater
- Rain gardens should be a minimum of 2 feet from the water table at their lowest point.
- Determine the Hydrologic Soils Group (A,B,C,D) at the site. If your soil is Group A or B, then take the next step and conduct a field percolation test. If your soil is Group C or D, select another site or consult with a landscape professional. Alternatively, you might consider other types of stormwater management controls such as installing a rain barrel or removing impervious coverage.
ITEM 3: Marking For Underground Utility Lines
- Miss Utility must be notified to mark any proposed project location. It is recommended to mark out the proposed project location in white paint to assist marking personnel. When possible, locate projects in areas that have no evidence of marked underground facilities. In cases where project site locations are in close proximity to underground facilities, caution is advised. Markings are not always accurate and actual depth varies. A hand dig zone extends 18” to either side of a marked facility in order to minimize damage and enhance safety. Individuals need to be especially cautious when working around electric and gas facilities. For further information on Miss Utility and the uniform color code use to identify facility types, please visit http://www.missutility.net/homeowners
ITEM 4: Assemble Permit Package (Duration For Approval: 5 to 6 weeks)
If in a County right-of-way, easement, or accepting public drainage, submit the following additional documents:
Permit Package Submission:
If your rain garden is on private property, deliver package to 2664 Riva Road, 1st Floor, Permit Application Center, Annapolis, MD 21401. If your rain garden is on or connects to public property, deliver package to 2662 Riva Road, 3rd Floor, Suite 310, Annapolis, MD 21401
ITEM 5: Rain Garden Installation (Following Permit Approval)
- Notify the Department of Public Works daily as work proceeds at 410-222-7344 (if in a County right-of-way, easement, or accepting public drainage)
Rain Garden Installation Guides:
ITEM 6: Stormwater Management Tax Credit
Include with your application the following materials:
- All Invoices for material and labor
- Photographs of the completed installation
- Signed tax credit application
- Copy of County permit(s)
Estimated processing time is four weeks. Depending on the date of submittal, a property owner will either recieve an adjusted property tax bill or a refund check via US Mail. Please submit all materials t Anne Arundel County, Office of Finance, Attention: Sales Tax Accountant, PO Box 427, Annapolis, Maryland 21404
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