INLAND EMPIRE ASCE & APWAINLAND EMPIRE ASCE & APWALOW IMPACT DEVELOPMENT LOW IMPACT DEVELOPMENT

(LID) SEMINAR(LID) SEMINAR

LID FACILITY DESIGN

Prepared by Eric Prepared by Eric Mosolgo

October 14, 2009October 14, 2009

Riverside, CaliforniaRiverside, California

BackgroundBackground

Contra Costa ApproachContra Costa Approach Stormwater treatment and flow controlStormwater treatment and flow control Minimize directly connected impervious areasMinimize directly connected impervious areas Avoid standing water / vector issuesAvoid standing water / vector issues

BackgroundBackground

San Diego HMP and Model SUSMP San Diego HMP and Model SUSMP UpdateUpdate

Sacramento HMPSacramento HMP

BackgroundBackground

Watershed and Stream ScaleWatershed and Stream Scale Site scaleSite scale

Reduce peak flowsReduce peak flows Detain runoff on siteDetain runoff on site

Increase time of concentrationIncrease time of concentration Slow runoff from leaving siteSlow runoff from leaving site

No runoff from small stormsNo runoff from small storms Infiltrate and evapotranspirate Infiltrate and evapotranspirate

Reduce duration of moderate flowsReduce duration of moderate flows Let runoff seep away very slowlyLet runoff seep away very slowly

Reduce runoff volumeReduce runoff volume Infiltrate where possibleInfiltrate where possible

Reduce runoff energyReduce runoff energy Detain and slow flowsDetain and slow flows

Increase groundwater storage and Increase groundwater storage and stream base flowsstream base flows

Facilitate infiltrationFacilitate infiltration

Reduce pollutants in runoffReduce pollutants in runoff Detain and filter runoffDetain and filter runoff

Protect against spills and dumpingProtect against spills and dumping Disconnect drainage and filter runoffDisconnect drainage and filter runoff

Presentation OverviewPresentation Overview

Design Design ConsiderationsConsiderations Urban Retrofit Urban Retrofit

ChallengesChallenges Arid Climate Design Arid Climate Design

AdjustmentsAdjustments Hydromodification Hydromodification

Mitigation with LIDMitigation with LID

Presentation OverviewPresentation Overview

Modeling Approaches and Summary of Modeling Approaches and Summary of Existing SoftwareExisting Software Single-Event ModelingSingle-Event Modeling Continuous Simulation ModelingContinuous Simulation Modeling

Presentation OverviewPresentation Overview

Hydrologic and Hydraulic AnalysisHydrologic and Hydraulic Analysis Single Event Model ExampleSingle Event Model Example Continuous Simulation Model ExampleContinuous Simulation Model Example

Presentation OverviewPresentation Overview

Maintenance and Monitoring RequirementsMaintenance and Monitoring Requirements

Design ConsiderationsDesign ConsiderationsUrban Retrofit ChallengesUrban Retrofit Challenges

Bioretention basinsBioretention basins

Rain gardensRain gardens

Bioretention swalesBioretention swales

Bioretention in Bioretention in combination with vaultscombination with vaults

Flow-through planter Flow-through planter boxesboxes

Porous pavementPorous pavement

Rainwater collection Rainwater collection systemssystems

Design ConsiderationsDesign ConsiderationsUrban Retrofit ChallengesUrban Retrofit Challenges

Lateral migration of Lateral migration of infiltrated runoffinfiltrated runoff

Downstream ponding Downstream ponding problemsproblems

Infiltrated runoff to Infiltrated runoff to joint trenchjoint trench

LID options for LID options for roadway designroadway design

Design ConsiderationsDesign ConsiderationsUrban Retrofit ChallengesUrban Retrofit Challenges

WQ Storage in voids of sub-surface soil WQ Storage in voids of sub-surface soil layerlayerAmended soils; minimize soil compactionAmended soils; minimize soil compactionSoil infiltration rate should exceed 1.5 in/hrSoil infiltration rate should exceed 1.5 in/hr50% sand, 25% compost, 25% planting 50% sand, 25% compost, 25% planting soilsoil30% voids30% voidsSoil depth of 4 feet recommended for Soil depth of 4 feet recommended for bioretention areas with treesbioretention areas with trees

Design ConsiderationsDesign ConsiderationsArid Climate AdjustmentsArid Climate Adjustments

Native and drought-Native and drought-tolerant plantstolerant plants

Varying pollutant loading Varying pollutant loading and ponding levelsand ponding levels

Conflict with water Conflict with water conservation goalsconservation goals

BMPs used in arid BMPs used in arid environments will require environments will require monitoring to assess monitoring to assess performanceperformance

Rainfall analysis methodsRainfall analysis methods

Design ConsiderationsDesign ConsiderationsLID Hydromodification MitigationLID Hydromodification MitigationRainfall adjustmentsRainfall adjustmentsLocate LID in areas of Locate LID in areas of pervious (A or B) soilspervious (A or B) soilsSurface reservoir must fillSurface reservoir must fillDrawdown time Drawdown time requirementrequirementOffsite area restrictionsOffsite area restrictionsVarying lower flow Varying lower flow thresholdsthresholdsMinimum orifice size Minimum orifice size criteriacriteria

Design ConsiderationsDesign ConsiderationsLID Hydromodification MitigationLID Hydromodification Mitigation

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 1 2 3 4 5 6 7 8 9 10

Recurrence Interval (years)

Pea

k F

low

(cf

s)

ImperviousMitigated Post-Project SitePre-Project Site0.5Q2

IMP Reduces Impervious Runoff to Less Than Pre-Project Levels

Design ConsiderationsDesign ConsiderationsLID Hydromodification MitigationLID Hydromodification Mitigation

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

% Time Exceeded

Flo

w (

cfs

)

ImperviousMitigated Post-Project SitePre-Project SiteQ100.1Q2

IMP Reduces Impervious Runoff to Less Than Pre-Project Levels

LID Modeling ApproachesLID Modeling Approaches

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

Limit contributing Limit contributing watershed area watershed area (dispersed facilities)(dispersed facilities)

Fast-draining soils Fast-draining soils (amended soils)(amended soils)

Summary of Existing Summary of Existing LID Modeling SoftwareLID Modeling Software

Single-Event ModelsSingle-Event Models

Continuous Simulation ModelsContinuous Simulation Models HSPFHSPF HEC-HMSHEC-HMS SWMMSWMM Contra Costa LID Sizing CalculatorContra Costa LID Sizing Calculator San Diego HMP / LID Sizing CalculatorSan Diego HMP / LID Sizing Calculator

Summary of Existing LID SoftwareSummary of Existing LID SoftwareContra Costa Sizing CalculatorContra Costa Sizing Calculator

Sizing Factor Sizing Factor DevelopmentDevelopmentSoil GroupSoil GroupLand UseLand UseTreatment / Mitigation Treatment / Mitigation ApproachApproachSoil Physics at BMP Soil Physics at BMP Layer InterfacesLayer InterfacesWQ only sizing factorsWQ only sizing factorsWQ + Flow Control Sizing WQ + Flow Control Sizing FactorsFactors

Varying Conditions Soils (NRCS A, B, C, D) Land Cover Precipitation

Non-Structural Measures Pervious Pavement Self-Retaining Areas

Summary of LID Modeling Software Summary of LID Modeling Software

San Diego HMP / LID CalculatorSan Diego HMP / LID CalculatorDetention Basin Calculator (low flow orifice Detention Basin Calculator (low flow orifice and overflow weir)and overflow weir)

Pond configuration and outlet structure Pond configuration and outlet structure criteriacriteria

LID credit to reduce pond sizingLID credit to reduce pond sizing

Graphical Output of Peak Flow Frequency Graphical Output of Peak Flow Frequency and Flow Duration Responseand Flow Duration Response

Automated Rainfall Gage SelectionAutomated Rainfall Gage Selection

Summary of LID Modeling SoftwareSummary of LID Modeling SoftwareSan Diego HMP / LID CalculatorSan Diego HMP / LID CalculatorInfiltration Devices for Parking Infiltration Devices for Parking Lots (scaling factor that varies Lots (scaling factor that varies with depth / bottom area ratio)with depth / bottom area ratio)Infiltration strips and tree wellsInfiltration strips and tree wellsTreatment only option for Treatment only option for vegetated swalesvegetated swalesExtended detention basin Extended detention basin optionoptionIncorporation of generic LID Incorporation of generic LID options for BMP manufacturersoptions for BMP manufacturersPervious pavementPervious pavement

Water Quality Only Flow Control Bioretention Cistern + Bioretention Bioretention + Vault Flow-Through Planter Dry Well Detention Basins Vegetated Swales Extended Detention Basins

Regulatory Levels Varying Lower Control Threshold

Performance and Output Summary Output for Plan Reviewers Performance Curves for Pond Sizing Integrated Help System

Summary of ExistingSummary of ExistingLID Modeling SoftwareLID Modeling Software

Treatment & Flow ControlTreatment & Flow Control NRCS Soil GroupNRCS Soil GroupAA BB CC DD

Bioretention FacilityBioretention FacilityAA 0.070.07 0.110.11 0.060.06 0.050.05VV11 0.0580.058 0.0920.092 0.0500.050 0.0420.042VV22 N/AN/A N/AN/A 0.0660.066 0.0550.055Flow-through PlanterFlow-through PlanterAA N/AN/A N/AN/A 0.060.06 0.050.05VV11 N/AN/A N/AN/A 0.0500.050 0.0420.042VV22 N/AN/A N/AN/A 0.0660.066 0.0550.055Dry WellDry WellAA 0.050.05 0.060.06 N/AN/A N/AN/AVV 0.1300.130 0.2040.204 N/AN/A N/AN/ACistern + bioretention facilityCistern + bioretention facilityA (bioretention facility)A (bioretention facility) 0.040.04 0.040.04 0.040.04 0.040.04V (cistern)V (cistern) 0.1930.193 0.2280.228 0.0880.088 0.0600.060

Hydrologic and Hydraulic AnalysisHydrologic and Hydraulic Analysis

Single-Event ExampleSingle-Event Example

0.2 inches/hour

BMP Area/Impervious Area =0.2/5 = 0.04

Planting mediumi = 5 inches/hour

Hydrologic and Hydraulic AnalysisHydrologic and Hydraulic Analysis

Continuous simulation Continuous simulation model examplemodel example

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

Peak flow frequency Peak flow frequency statistics based on partial statistics based on partial duration calculationsduration calculations

Parameter estimation Parameter estimation (infiltration, evaporation)(infiltration, evaporation)

Hydrologic and Hydraulic AnalysisHydrologic and Hydraulic AnalysisInput SummaryInput Summary

Hydrologic and Hydraulic AnalysisHydrologic and Hydraulic AnalysisOutput SummaryOutput Summary

Maintenance RequirementsMaintenance Requirements

HOA maintenanceHOA maintenanceRegular inspections to verify Regular inspections to verify vegetative establishment and vegetative establishment and prevent invasive vegetationprevent invasive vegetationRemoval of accumulated Removal of accumulated sediment sediment Replacement of dead Replacement of dead vegetation, erosion repair at vegetation, erosion repair at inflow, unclogging the inflow, unclogging the underdrainunderdrainChecks for standing waterChecks for standing waterVector controlVector control

Monitoring RequirementsMonitoring Requirements

Collect data for minimum of 2 rainy seasonsCollect data for minimum of 2 rainy seasons

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

Obtain facility inflows and outflowsObtain facility inflows and outflows

Compare collected data to predicted dataCompare collected data to predicted data

Questions?Questions?

Eric Mosolgo, PEEric Mosolgo, PE

Brown and CaldwellBrown and Caldwell

(858) 571-6736(858) 571-6736

emosolgo@brwncald.comemosolgo@brwncald.com