Construction and Maintenance Presented by: The Low Impact Development Center, Inc. A non-profit water resources and sustainable design organization .

Construction and Maintenance

Presented by:

The Low Impact Development Center, Inc. A non-profit water resources and sustainable design organizationwww.lowimpactdevelopment.org

Presented by:

The Low Impact Development Center, Inc. A non-profit water resources and sustainable design organizationwww.lowimpactdevelopment.org

The Low Impact Development Center, Inc. has met the standards and requirements of the Registered Continuing Education Program. Credit earned on completion of this program will be reported to RCEP at RCEP.net. A certificate of completion will be issued to each participant. As such, it does not include content that may be deemed or construed to be an approval or endorsement by RCEP.

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© Low Impact Development Center, 2012

The purpose of this presentation is to describe the importance of proper construction and maintenance to the success of LID

At the end of this presentation, you will be able to:• Explain the importance of construction oversight• Discuss maintenance requirements of bioretention

and permeable pavers• Describe how to repair or restore failed systems

Purpose and Learning Objectives

Key Points

• Construction Observation• Maintenance for Bioretention and Pavers (Softscape

and Hardscape)• Corrective Actions• General Environmental Monitoring

Permeable Paving Types

• Concrete or plastic grid pavers

• Permeable interlocking concrete pavers

• Porous asphalt• Pervious concrete

PICP Concrete pavers

Open-graded subbase reservoir

Uncompacted subgrade soil

Open-graded base reservoir

Underdrain(as required)

Optional geotextileunder the subbase

Permeable joint materialOpen-gradedbedding course

System Components

Construction: Subbase & Base Preparation

• 3.5” - 4” pervious Bituminous asphalt placed directly on stone base

• Rolled to a finished depth of 2.5” - 3”• 1 ½” Open Graded Friction Course (OGFC)• 3” Asphalt Treated Permeable Bases (ATPB)

Installation of Porous Asphalt

Source: CA Coastal Commission

Installation of Porous Concrete

Jointing

• Roughly ½ the shrinkage of normal concrete

• Joints are typically placed every 20’

• Best practice is to tool jointso Sawing can cause raveling

• Curing pervious concrete is critical due to the porosity and low W/C ratio

• Without curing, surface will dry out and deteriorate easily• Moist cure (7 days preferred)

Curing

Permeable Paver Installation

PICP Joint Aggregate Installation

Bioretention

Bioretention: Media Placement

• Add media in 6” lifts• Thoroughly wet and

allow soil to drain• Make sure the media is

at specified height below overflow

High Rate

Bio-filtration

Inadequate Erosion Control or Protection of BMP Areas

Keep Erosion Controls in Place Until Drainage Area is Stabilized

Slide 19

Irving St Images

P5240081 &

P4260061

Unapproved Material Substitutions

Irving St Image (DSCN3901)

Unapproved Material Substitutions

Plant Density

Plant Location

Isolation of Hazards

• Regulatory requirement o NPDES MS4 permito Other State storm water regulations (new)o Documentation may be required

• Necessary to continue function as designed• Proper maintenance lowers long term costs • Less costly to maintain than repair or replace

Maintenance Drivers

Maintenance – Bioretention

• Primary maintenance requirement - regular inspection and repair / replacement of damaged components

• Can be incorporated into regular landscaping maintenance contract, as the routine periodic

maintenance for bioretention areas is similar to what is required of any landscaped area

Maintenance – Bioretention

Planting Maintenance

• Routine maintenance should include a biannual health evaluation of the plantings, and removal and replacement of any dead or diseased vegetation.

• The use of native plant species in the bioretention cell will reduce fertilizer, pesticide, water, and overall maintenance requirements.

• Level of pollutants in the soil can become toxic, impair plant growth

Maintenance – Bioretention

Planting maintenance• Immediately after installation, water plant material for 14 consecutive days

(unless sufficient natural rainfall).• When trees have taken root, or at least by 6 months, remove stakes and wires• Visually inspect vegetation for disease or pest problems at least once in the

spring, once in the fall, and more frequently in the summer. If treatment is warranted, use the least toxic approach

• During extended drought, look for physical signs of stress (unrevived wilting; yellow, spotted or brown leaves; loss of leaves, etc.). Water in the early morning if needed

• Prune excess growth annually in the spring and throughout the growing season if desired. Trimmed materials may be recycled back in with replenished mulch or landfilled if there is a concern of heavy metals accumulation.

• Weed regularly, as necessary

Maintenance – Bioretention

Requirements Testing Remediation

Soil pH should reflect local plant materials

Obtain a kit and instructions from the State Cooperative Extension Office.

Apply the necessary amount of limestone or compost to get the pH in the correct range.

Soils• Visually inspect and repair erosion at inflow points once in the spring and

once in the fall, at a minimum. • Use small stones to stabilize erosion along drainage paths.• Check the soil’s pH once or twice a year. • Apply an alkaline product, such as limestone, if needed.

Maintenance – Bioretention

Soils - Maintain Infiltration Rates• Runoff from impervious surfaces is directed to bioretention cells

to infiltrate through the soil medium• Once the infiltration

capacity of the soil medium is exceeded, storm water begins to pool at the soil’s surface

• Ponding should only last 4-6 hours

• Mosquitoes larva need 4+ days of standing water

Maintenance – BioretentionSoils – Corrective Action• Depending on pollutant loads, soils may need to be replaced within 5-30 years

of construction.• If standing water consistently over 4-6 hrs:

o Clear the underdrain of potential clogso Check filter fabric above the underdraino Remove mulch and rake surface to remove surface blockages o Last resort - remove the soil mixture

• Before removing soil mixture, analyze for clay content and hazardous content• If greater than 15% clay content, then:

o Temporarily block end of discharge pipe, install appropriate E&S controlso Carefully dig up plants so that root systems are maintained (and return to

cell following soil replacement)o Remove soil and dispose appropriately as clean fill or in an approved landfill o Inspect pipe and gravel layer, if pipe is clogged, then wash the gravel layer

with a high-pressure hose – this should clean the pipeo Place new soil in the cell and replant vegetation

Maintenance – Bioretention

Mulch Layer

• Uniformly applied approximately 2 to 3 inches deep. Do not pile the mulch around trees or other plantings

• Fresh redwood bark mulch. Make sure it is free from weed seeds, soil, roots or any other substance not consisting of bole, branch wood, or bark Do not use grass clippings as mulch

• Typically, every 6 months, in the spring and fall, add a fresh mulch layer. Once every 2 to 3 years, in the spring, remove the old mulch layer before applying the new one

Description Frequency

1. Soil

a) Inspect and Repair Erosion Spring and fall

b) Check pH Once a year

2. Organic Layer

a) Re-mulch any void areas As needed

b) Add new mulch layer Spring and fall

c) Remove old mulch layer Three (3) years

3. Plants

a) Water plant material for fourteen consecutive days after planting has been completed unless there is sufficient natural rainfall

Immediately afterCompletion ofproject

b) Remove stakes and wires after six months After rooting

c) Inspect for disease/pest problems Spring/summer/fall

d) Treatment of diseases As needed, refer tomanufacturer

Maintenance Schedule – Bioretention

3. Plants (continued)

e) Removal and replacement of all dead and diseased vegetation considered beyond treatment Spring and fall

f) During times of extended drought, look for signs of stress Water as needed. Summer

g) Weed and prune excess growth Spring/summer

h) Fertilize As needed, refer to manufacturer

i) Remove tags After warranty

4. General

a) After major rainstorms, inspect site and make sure drainage paths are clear and that ponding water dissipates over time. Clear the drainage path of any accumulated sediment or debris. Seek remediation if drawdown times are consistently much longer than 4-6 hours

After major rainstorms

Maintenance Schedule – Bioretention

Tree box filter plant maintenance

Maintenance – Permeable Pavers

• Primary maintenance requirement - clean the surface drainage voids

• Can be incorporated into regular street sweeping program

• Annual inspections

After 10 years

Some localized clogging and repairs

• Inspections • Routine maintenance is key:

o Conventional street sweepers equipped with vacuum sweepers and high-pressure water can used to restore permeability

o Street sweeping frequency varies depending on drainage area inputs (leaf debris, erosion, etc.). An active street sweeping program in the site’s drainage area will also help to prolong the functional life of the pavement

o If necessary, add additional gravel chips to fill pore spaces after vacuum sweeping

• In case of localized settling, individual paver blocks can be removed, new gravel added, and the blocks replaced

Maintenance – Permeable Pavers

• Restrict use by heavy vehicles

• Limit use of de-icing chemicals and sand

• Implement stringent sediment control plan

• Failure of systems:o poor designo inadequate construction

techniqueso low permeability soilso heavy vehicular traffico resurfacing with nonporous

materials

Maintenance – Permeable Pavers

Maintenance Schedule Permeable Pavers

Description Frequency

Initial Inspections Monthly for first several months following construction

Vacuum sweeping and highpressure hosing

4 times/year

Encourage active street cleaningin the site’s area

Regularly

Annual inspections Yearly, after large storms

Fill potholes and cracks As needed

Address spot-clogging problemsby drilling holes

As needed

Maintenance – Permeable Pavement

Routine Maintenance• Similar to permeable pavers • Recommended: Vacuum

sweep twice per year

Maintenance – Permeable Pavement

Corrective Action• Fill potholes and cracks with

permeable patching mixes• Fix spot clogging by drilling

~0.5-inch holes through the porous pavement layer every few feet

Courtesy Cahill

Monitoring Programs

• Not typically a regulatory requirement (unimpaired)• Potential requirement for discharges to sensitive or impaired

waters• Monitoring plan shaped by regulatory requirements, site

characteristics, parameter(s) of concern, and use of the data

Water Quantity MonitoringMonitor the effectiveness of LID features either on a small scale (individual features) or large scale (stream flow):

Small Scale Manual or automatic sampling methods can be used to calculate flow rates upstream and downstream of a LID feature, based on the depth measured using a weir or a rate of flow measured using a conveyance device.

Large ScaleWhere LID features are being installed as retrofits in already developed areas, the effectiveness of the retrofits can be assessed by comparing pre-LID and post-LID flow rates downstream.

Thank you for your time.

QUESTIONS?

Low Impact Development Center, Inc.www.lowimpactdevelopment.org

301.982.5559