GSI_MX_Guide_v1_2022.pdf

Green Stormwater Infrastructure (GSI)

Maintenance

Published by the City of Tucson Storm to Shade Program

First Edition: August 2022 A Pocket Guide

Contents Intro to GSI / what is it and why is it important?

The Structure of GSI / what’s in your basin?

GSI Maintenance / common tools, quick GSI maintenance guide

Plant Care for GSI / plant care checklist, common weeds

Soil and Mulch / benefits and guidelines

Tree Care for GSI / basic tree pruning guide

GSI Maintenance by the Season / checklist

Common GSI Features:

The Storm to Shade Program administered by Tucson Water funds and oversees the maintenance of GSI features located on public property in the City of Tucson. This manual provides an overview of best practices for maintaining GSI features and is a guide for landscape professionals and anyone else working in GSI.

Chicane / Curb Extension Traffic Median

So what is green stormwater infrastructure (GSI) and why is it important?

GSI refers to landscape features designed to capture and use stormwater runoff from hardscape to support healthy soil, vegetation, and biodiversity.

GSI includes inlets, outlets, and overflows as well as earthworks such as basins, berms, and swales to capture, contain, and direct the flow of water into vegetated areas. GSI provides a variety of benefits including...

Reducing stormwater pollution and improving water quality

Shading and cooling streets, sidewalks, bikeways, and parking areas

Mitigating minor flooding

Creating wildlife habitat and supporting biodiversity

Beautifying the urban environment

Providing a nature based complement to gray infrastructure

Decreasing reliance on potable water for landscape irrigation

Right-of-Way BasinTraffic Circle

The structural elements of GSI

INFILTRATION BASIN

CURB CORE

INLETS/OUTLETS

PLANTING SHELF

SEDIMENT TRAP

CURB CUT

Depression within a GSI feature that allows stormwater to infiltrate the soil

Circular core drilled through curbing that serves as an inlet or outlet

Conveyance allowing stormwater to flow into or out of a GSI feature

Elevated planting area within a GSI feature ph ot o:

T uc so n Cl ea n

B ea ut ifu l ph ot o:

W at er sh ed

M gm t G ro up

Rough area at inlet that allows sediment to settle before water enters a basin

Removed section of curbing that serves as an inlet or outlet

GSI Maintenance the tools of the trade plant ID appsbypass pruners plant ID guides tool disinfectant tree pruning handsaw flat shovel round shovel digging barleaf rake pitchfork push broom trash grabber geologist hammer gloves safety glasses

Cues to Care... quick GSI maintenance guide

Can stormwater easily enter and collect in the

GSI?

1. 2.

Is vegetation obstructing signage or visibility or impeding pedestrian or vehicle traffic?

YES NO

YES

YES

NO

no action required no action required

Remove obstructions (debris, rocks, sediment, vegetation) and dispose of or redistribute appropriately*.

no action required

Remove sediment from the bottom of the infiltration basin.

Dispose of/redistribute removed material appropriately. Mulch exposed soil whenever possible.

Are there obstructions to the inlet and/or sediment trap?

Perform the minimum pruning necessary to remove obstructive or dangerous vegetation. Do not perform significant pruning or tree removal without consulting an ISA certified arborist.

See GSI Pruning Guide

Is the ground/soil level at the bottom of the infiltration basin lower than the level of the inlet?

NO YES

NO

* Redistribute excess sediment to high points of GSI or carry off site.

3. 4.

Is the GSI feature free of trash?

YES YESno action required no action required

Remove weeds, invasive plants, and volunteer trees** See Plant Care for GSI

Remove trash and dispose of it appropriately.

Reference Common Weeds or preferred plant guide

NO NO

UNSURE

Less is More: GSI uses natural processes to perform ecosystem services. Minimal interventions that ensure the function of the asset are often most appropriate for routine maintenance. Routine maintenance of GSI assets includes:

• Removing obstructions from inlets and outlets

• Removing accumulated sediment

• Removing weeds, invasive or unwanted plants, and trash

• Pruning for safety

• Minor rockwork repair, securing/replacing loose rock

• Leaving organic material onsite (no raking for aesthetic purposes)

** Volunteer trees that do not obstruct inlets or site visibility may remain

Is the GSI feature free of weeds, invasive plants, and unwanted volunteer trees?

Plant Care for GSI Plants are an integral part of GSI and offer a number of services and benefits including:

providing evaporative cooling through transpiration filtering and breaking down contaminants in stormwater runoff improving soil structure to facilitate infiltration and percolation providing habitat for wildlife providing shade, screening, and natural beauty

Plant health is crucial to the function of GSI features. Supporting plant health during routine GSI maintenance involves:

ensuring irrigation is functioning / plants are receiving water replacing dead plants minimizing pruning maintaining a mulch layer to conserve soil moisture

Remove weeds, invasive plant species, and unwanted volunteer trees by pulling or digging them out

Remove unnecessary tree stakes/nursery stakes, and girdling ties

Assess irrigation

still running Move irrigation away from established tree or shrub trunks to the edge of canopy

Clear rocks, sediment, and deep mulch away from the base of trunks

Expose buried root flares

Practice the “Chop and Drop” method, leaving leaf litter, seed-free weeds, and trimmings less than 1” diameter and 3” length in basin bottom as mulch

Trim back shrubs and other low-lying vegetation from walkways/roadways

GSI Plant Care Checklist

Chop Free Mulch!& Drop

Sustaining Soil Maintaining healthy soil is also crucial to plant health and GSI feature functionality. Consider the following best practices while performing GSI maintenance:

minimize soil disturbance, avoid raking for aesthetic purposes keep soil mulched (wood chips, leaves, trimmings, other aggregates) avoid activities that can lead to soil compaction - i.e. driving, parking, walking in or on GSI features or plant root zones minimize erosion - ensure earthworks, rockwork and other grade controls are in place and functioning avoid the use of herbicides and pesticides*

Magical Mulch preserves soil moisture adds organic matter to soil reduces weeds and erosion supports microbial activity keeps soil cool

Covering the soil surface with 2” - 4” of mulch can provide these benefits and more.

* Herbicides/pesticides may be applied by AZ State Certified Applicators with formal approval from COT S2S program’s maintenance leadership.

Common Weeds

Stinknet fire risk fire risk fire risk fire risk fire risk

BuffelgrassBuffelgrass Fountain Grass

Goat Head

Russian Thistle London Rocket Cheeseweed

Bermuda Grass

GSI Tree Pruning Guide

Tree Pruning should only be done if there is a safety concern, clearance issue, or if the health of the tree is at stake. A certified arborist should perform any significant pruning. Every pruning cut is a wound the tree must seal and improper cuts or too many cuts endanger the life of the tree.

Sight Visibility Triangle (SVT) Clearance - At crosswalks and intersections, an unobstructed and continuous view of both the intersection and the intersecting roadway helps pedestrians, cyclists, and drivers avoid conflicts. Trees should be pruned to 7’ for SVT clearance and shrubs should not exceed 30” in height.

Right Tree Right Place - When planting or replacing trees, consider the tree’s mature size and growth form as it relates to the planting location. Selecting an appropriate tree can help to minimize pruning needs, clearance concerns, and damage to adjacent infrastructure.

30” sh ru b

SV

T cl ea ra nc e at i nt er se ct io ns ensure visibility of roadway signs

Pruning for Safety

• pedestrian clearance

• vehicle clearance

• visibility of roadway signage

• site visibility triangles

• to remove broken or hazardous limbs

Pruning for Tree Health

• removing dead wood

• removing rubbing or crossing branches

• removing codominant branching

• remedial pruning for improper pruning such as stub cuts

15’

7’ ve hi cl e cl ea ra nc e pe de st ria n

SV

T cl ea ra nc e clear tree limbs from bike lanes

Basic Tree Pruning the DOs cut 1 final cut cut 2

Prune as minimally as possible

Use the right tools - bypass pruners, tree pruning handsaw

Use clean tools - disinfect tools between each tree or shrub

Use proper pruning techniques :

Reduction Cuts (right) Trim back to the nearest lateral branch or to main trunk, ensure that the remaining lateral is at least 1/3 the diameter of the cut branch.

The 3 Cut Method (left) for large or heavy branches:

Cut 1 - Make an undercut through 1/3 of branch Cut 2 - Make the top cut slightly farther on the limb than the undercut to remove the branch Cut 3 - Make final cut just outside branch collar/branch bark ridge to remove the stub lateral branch

1/3 diameter of cut branch cut branch

Proper pruning techniques can prevent injuries to trees that make them susceptible to decay or infestation, or lead to a loss of photosynthetic function.

the DON’Ts stub flush cut

Don’t remove more than 1/3 of the canopy at once

Never ‘Top’ trees/shrubs or prune them into artificial shapes

No Stub Cuts

No ‘Topping’

No Flush Cuts

No ‘Lion Tailing’

Don’t remove anything that does not present a safety or visibility issue

Don’t prune trees that appear to be less than 2 yrs old

*Refer to City of Tucson Landscape Maintenance Manual (Nov 2020) for more detail

SPRING / PRE-MONSOON april 1 - may 31

SUMMER / MONSOON jun 1 - aug 31

FALL / POST-MONSOON sep 1 - nov 30

GSI Maintenance... a seasonal checklist

Clear inlets and outlets

Remove excess sediment

Prune for safety

Remove trash

Clear inlets and outlets

Remove excess sediment

Pull invasive weeds

Leave native annuals

Light pruning as necessary

Remove trash

Clear inlets and outlets

Remove excess sediment

Pull invasive weeds

Leave native annuals

Light pruning as necessary

Remove trash

LATE WINTER / EARLY SPRING feb 16 - mar 31 Clear inlets and outlets

Remove excess sediment

Trim back bunch grasses

Deadhead spent wildflowers and disperse seeds

Trim back frost damaged foliage

Pull invasive weeds

Leave native annuals

Light or structural pruning if necessary

Remove trash

WINTER dec 1 - feb 15 Pull invasive weeds

Leave native annuals

Deadhead spent wildflowers and disperse seeds

Trim back frost damaged foliage

Turn irrigation off (generally November-March)

Remove trash

GSI Contacts :

City of Tucson Storm to Shade Program www.climateaction.tucsonaz.gov/pages/gsi www.tucsonaz.gov/gsi

Other GSI Partners:

Tucson Clean & Beautiful: GSI Mini-Grants Program tucsoncleanandbeautiful.org/trees-for-tucson/gsi-mini-grants/

Pima County Flood Control District webcms.pima.gov/government/flood_control/