Maintaining Rain Gardens, Swales, and Stormwater Planters

Gail Shaloum, PLA BuildRight Conference April 2021

Agenda1. What is stormwater/why

manage it?

2. Legal background and local requirements

3. Understanding types of facilities and their components

4. Preparation, access, & safety

5. Maintenance:• Trash

• VegetationEffective plant choices

Weeds

Pruning

Replacement

• Irrigation

• Soils, erosion and sedimentation

• Structures

• Spills

6. Take-home messages

What is stormwaterand why manage it?

Image credit: https://www.hemetca.gov/898/Stormwater-Program

Stormwater impacts• Degrades stream

habitat

• Flooding

• Carries pollutants• Sediments

• Nutrients

• Metals

• Oils & Grease

• Pesticides

• Temperature

Why care about water quality?

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Rain gardens, swales, stormwater plantersWhat’s the point?

1. Manage runoff at the source

2. Plants and soil slow, filter, infiltrate

3. Simple, low-cost, aesthetic

How do they work?

Legal background

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Local requirements

• Maintenance agreements

• Inspections

• Reporting

Types of facilities and their componentsWATER INFLOW SLOWS,

POLLUTION FILTERED,SEDIMENT DROPS OUT

WATER OUT(or not)

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Rain Garden with and without underdrain

-a bowl-shaped, generally flat-bottomed garden bed that collects and treats

stormwater runoff from impervious surfaces.

Rain Garden-Residential

Photo: East Multnomah Soil & Water Conservation District

Rain Garden-Municipal

Planted landscape facility designed to collect and absorb runoff and filter out

pollutants.

Swales (aka Bioswales)

Vegetated, open channel that carries, slows stormwater and filters out pollutants.

Photo: East Multnomah Soil & Water Conservation District

Stormwater Planter

“rain garden in a box”

Structural landscape reservoir

designed to filter out pollutants,

and in some cases, infiltrate

stormwater.

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Anatomy of an infiltration planter

Graphic: Clean Water Services,

LIDA Manual

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Anatomy of a flow-through planter

Graphic: Clean Water Services,

LIDA Manual

Stormwater Planter-forebay

RIP RAP

FOREBAY

Preparation-before you go

• O&M manual

• Maintenance plan or agreement

• As-built drawings/report

• Records from past maintenance visits

• Know what to expect

When you arrive: access

• How will you access?

• Flat or evenly sloped

• If fenced, trim fenceline for 3 feet if space allows

• Consider safety before you begin (do not enter flooded facility)

Safety

Personal Protective Equipment (PPE)

• Sturdy boots

• Gloves, puncture resistant gloves

• Ear plugs/earmuffs if operating power equipment

• Eye protection when “weed wacking” or mechanical trimming, handling large branches

• Long sleeved shirts and pants

• Hard hat if cutting

overhead

• *NEW FOR PANDEMIC: Face covering!

Maintenance: Trash and Debris Removal

• Remove trash and dispose appropriately.

• Remove accumulated debris.

Clogged inlets

City of Portland Environmental Services

Clogged outlets

City of Portland Environmental Services

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Vegetation

Planting Zones

Different plants will thrive in different areas of the facility.

• Characteristics of suitable plants:• Not invasive

• Native vs. Non-native

• Water needs

• Potential for growth

• Refer to the jurisdiction’s list of recommended plants

Recommended Plants

Rushes & Sedges

WES SWML

Herbaceous - Plant ID

• Great for Bottom of Basin• Grass-like, but not...

Rushes are Round - Sedges have Edges

Rush (Juncus) Sedge (Carex)

Gerry Carr botany.hawaii.edu/Gerry Carr botany.hawaii.edu/

Rush: Solid, round stem

Sedge: Solid, triangular stem

Grass: Hollow, round, jointed stem

EMSWCD emswcd.org

John Ruter, University of Georgia, Bugwood.org

Effective plant choices-need another class!

Blossom

Weed Control

• What is a weed?

• Control strategies:• Least impact on

environment

• Prevent seeding

• Manual

• Herbicides

• PNW Weed Management Handbook:

http://pnwhandbooks.org/weedBlossom

Weed Control

• Pay attention to the roots & seeds

• Timing is important! Know when they can be best controlled

• Proper disposal

Blossom

Herbicide Use

• Use only as a last resort

• When is it necessary?

• What are the local regulations?• May be site and

plant specific

Yellow Flag Iris in a facility

Clackamas SWCD

Weed i.d. & treatment-need another class!

Vegetation: how much pruning?

Vegetation: replanting

Irrigation

• Plants are critical to the function of these facilities

• Irrigation essential for plant establishment & health

• At least 2 years, longer for high exposure areas

• Water a little less each year until plants established

How to irrigate

• Water should percolate into the soils and not run off the surface.

• Hand watering- Put as much down as possible until water begins to migrate along surface. Then go to the next plant.

• Don’t over-water.

• Drip irrigation is very effective.

Soils, Erosion and sedimentation

• Healthy soils hold water

• Plants, soils, microbes work together to capture pollutants

• Too much sediment will clog the system

• Compaction will clog the system

City of Portland Environmental ServicesExample of forebay doing its job

Erosion

Maria Cahill

When do You Need to Remove Sediment ?

• 2-3 inches of sediment• draw-down rates exceed about 36 hours• Don’t let things get out of control

City of Portland Environmental ServicesCity of Portland Environmental Services

Structures-Remove sediment & debris

Structures-check & clean, repair, or replace

• Underdrains

• Retaining walls

• Culverts

• Curbs

• Check dams

• Etc.

Spills

• Determine what type of material has spilled

• Block stormwater inlets

• Use absorbent material to contain the spill

• Remove contaminated soil from facility

• Protective gear for workers

• Contact owner, local emergency response, & OR Emergency Response 800-452-0311

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Take-home messages

• These recommendations are general guidelines

• Check with the local jurisdiction for specific guidance

• Consult the Field Guide that was developed for our region https://emswcd.org/wp-content/uploads/2013/10/FieldGuideFinal.pdf

• For more information, contact: Gail Shaloum gshaloum@clackamas.us