Inland empire asce apwa low impact development lid seminar lid facility design
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INLAND EMPIRE ASCE & APWA LOW IMPACT DEVELOPMENT (LID) SEMINAR LID FACILITY DESIGN. Prepared by Eric Mosolgo October 14, 2009 Riverside, California. Background. Contra Costa Approach Stormwater treatment and flow control Minimize directly connected impervious areas

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Inland empire asce apwa low impact development lid seminar lid facility design


Prepared by Eric Mosolgo

October 14, 2009

Riverside, California



  • Contra Costa Approach

    • Stormwater treatment and flow control

    • Minimize directly connected impervious areas

    • Avoid standing water / vector issues



  • San Diego HMP and Model SUSMP Update

  • Sacramento HMP



Presentation overview

Presentation Overview

  • Design Considerations

    • Urban Retrofit Challenges

    • Arid Climate Design Adjustments

    • Hydromodification Mitigation with LID

Presentation overview1

Presentation Overview

  • Modeling Approaches and Summary of Existing Software

    • Single-Event Modeling

    • Continuous Simulation Modeling

Presentation overview2

Presentation Overview

  • Hydrologic and Hydraulic Analysis

    • Single Event Model Example

    • Continuous Simulation Model Example

Presentation overview3

Presentation Overview

  • Maintenance and Monitoring Requirements

Design considerations urban retrofit challenges

Design ConsiderationsUrban Retrofit Challenges

  • Bioretention basins

  • Rain gardens

  • Bioretention swales

  • Bioretention in combination with vaults

  • Flow-through planter boxes

  • Porous pavement

  • Rainwater collection systems

Design considerations urban retrofit challenges1

Design ConsiderationsUrban Retrofit Challenges

  • Lateral migration of infiltrated runoff

  • Downstream ponding problems

  • Infiltrated runoff to joint trench

  • LID options for roadway design

Design considerations urban retrofit challenges2

Design ConsiderationsUrban Retrofit Challenges

  • WQ Storage in voids of sub-surface soil layer

  • Amended soils; minimize soil compaction

  • Soil infiltration rate should exceed 1.5 in/hr

  • 50% sand, 25% compost, 25% planting soil

  • 30% voids

  • Soil depth of 4 feet recommended for bioretention areas with trees

Design considerations arid climate adjustments

Design ConsiderationsArid Climate Adjustments

  • Native and drought-tolerant plants

  • Varying pollutant loading and ponding levels

  • Conflict with water conservation goals

  • BMPs used in arid environments will require monitoring to assess performance

  • Rainfall analysis methods

Design considerations lid hydromodification mitigation

Design ConsiderationsLID Hydromodification Mitigation

  • Rainfall adjustments

  • Locate LID in areas of pervious (A or B) soils

  • Surface reservoir must fill

  • Drawdown time requirement

  • Offsite area restrictions

  • Varying lower flow thresholds

  • Minimum orifice size criteria

Design considerations lid hydromodification mitigation1

Design ConsiderationsLID Hydromodification Mitigation

Design considerations lid hydromodification mitigation2

Design ConsiderationsLID Hydromodification Mitigation

Lid modeling approaches

LID Modeling Approaches

  • General sizing approach for bioretention basins, bioretention swales and rain gardens

  • Limit contributing watershed area (dispersed facilities)

  • Fast-draining soils (amended soils)

Summary of existing lid modeling software

Summary of Existing LID Modeling Software

  • Single-Event Models

  • Continuous Simulation Models

    • HSPF

    • HEC-HMS

    • SWMM

    • Contra Costa LID Sizing Calculator

    • San Diego HMP / LID Sizing Calculator

Summary of existing lid software contra costa sizing calculator

Summary of Existing LID SoftwareContra Costa Sizing Calculator

  • Sizing Factor Development

  • Soil Group

  • Land Use

  • Treatment / Mitigation Approach

  • Soil Physics at BMP Layer Interfaces

  • WQ only sizing factors

  • WQ + Flow Control Sizing Factors

Summary of lid modeling software san diego hmp lid calculator

Summary of LID Modeling Software San Diego HMP / LID Calculator

  • Detention Basin Calculator (low flow orifice and overflow weir)

  • Pond configuration and outlet structure criteria

  • LID credit to reduce pond sizing

  • Graphical Output of Peak Flow Frequency and Flow Duration Response

  • Automated Rainfall Gage Selection

Summary of lid modeling software san diego hmp lid calculator1

Summary of LID Modeling SoftwareSan Diego HMP / LID Calculator

  • Infiltration Devices for Parking Lots (scaling factor that varies with depth / bottom area ratio)

  • Infiltration strips and tree wells

  • Treatment only option for vegetated swales

  • Extended detention basin option

  • Incorporation of generic LID options for BMP manufacturers

  • Pervious pavement

Summary of existing lid modeling software1

Summary of ExistingLID Modeling Software

Hydrologic and hydraulic analysis

Hydrologic and Hydraulic Analysis

  • Single-Event Example

0.2 inches/hour

BMP Area/Impervious Area =

0.2/5 = 0.04

Planting medium

i = 5 inches/hour

Hydrologic and hydraulic analysis1

Hydrologic and Hydraulic Analysis

  • Continuous simulation model example

  • Match pre-project flows and durations in the geomorphically significant flow range

  • Peak flow frequency statistics based on partial duration calculations

  • Parameter estimation (infiltration, evaporation)

Hydrologic and hydraulic analysis input summary

Hydrologic and Hydraulic AnalysisInput Summary

Hydrologic and hydraulic analysis output summary

Hydrologic and Hydraulic AnalysisOutput Summary

Maintenance requirements

Maintenance Requirements

  • HOA maintenance

  • Regular inspections to verify vegetative establishment and prevent invasive vegetation

  • Removal of accumulated sediment

  • Replacement of dead vegetation, erosion repair at inflow, unclogging the underdrain

  • Checks for standing water

  • Vector control

Monitoring requirements

Monitoring Requirements

  • Collect data for minimum of 2 rainy seasons

  • Monitoring sites should cover range of development types, have applicable rain gage data, be located in headwaters of watersheds, be located upstream of variety of receiving channel types.

  • Obtain facility inflows and outflows

  • Compare collected data to predicted data



Eric Mosolgo, PE

Brown and Caldwell

(858) 571-6736

[email protected]

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