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Conventional Storm Water ManagementConventional Storm Water Management
Does not view water as a resource
Moves water quickly from Point A – Point B
The problem with “Hydraulic Efficiency”Connection to the piped system, gutters, etc. quickly
transports water, sediment and other pollutants to our streams and ocean
Development practices, impervious surfaces, detention ponds, don’t replace nature’s ability to attenuate pollution or infiltrate water
Dealing with water but not the impacts to resources
Benefits of LIRBenefits of LIRPollution reductionProtect groundwater resourcesReduce impacts to natural stream channelsReduce impacts to in-stream biotiaReduce impacts to nearshore marine environmentCapture and reduce pollutantsRegulatory requirements & new incentivesAesthetics
In Kāne‘ohe, ~ 41 gals of water annually can be infiltrated for every 1 sq. ft. of impervious surface removed
Case study:Case study:KoKoʻ̒olaupoko Retrofitsolaupoko RetrofitsLow-Impact Retrofits (LIR)
D: defined as landscape featured which use green infrastructure principles and ideas to manage storm water within a confined urban space.
Address conventional development practicesGain some pre-development hydrologyPollution reductionEducation
Needle in a Haystack:Needle in a Haystack:AKA Watershed StatisticsAKA Watershed Statistics
~45,000 acres is size21 contemporary watersheds11 traditional ahupuaʻa Minimum of 11 different streams listed on
EPA’s 303 (d)41.56” – 74.30” annual rainfall in urban areas
of Koʻolaupoko.25% impervious surface(Waikane) – 56.99%
(Keaʻahala)
Urban Sub-basin Action PlanUrban Sub-basin Action PlanGoal
Assess urban areas and other developed land that contribute to non-point source pollution in Koʻolaupoko using ecologically-based metrics to identify and prioritized opportunities for LIR implementation.
ObjectiveUSBAP shall inform and guide the
implementation of projects to restore to the fullest extent possible a site’s pre-development hydrology and address pollutants by using design techniques that infiltrate, filter, store, evaporate and detain runoff as close to its source as possible
Identification of LIRIdentification of LIRHow to find projects, which ones should be implemented?
Development of Methods • Technical Advisory Committee• Literature Review, limited documents on completed urban assessments
Center for Watershed ProtectionUrban Storm Water Retrofit Practices:
Manual 3 & Appendices (August 2007)
Development of Methods con’t.Partnered with NOAA’s Pacific Services Center to develop new GIS toolsUtilized Habitat Priority Planner (HPP) to
assess watershed including % imperviousness
Used Data Explorer to search for…Percent ImperviousnessTMK Parcel SizeZoning District Classification
•How do you search 27,323 TMK parcels?•What factors can be used to identify potential LIR project sites?
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Identification of LIR Methods
% Imperviousness% Imperviousness
19,886 = No. of TMK parcels between 50% - 100% Imperviousness
TMK Parcel SizeTMK Parcel Size
1,432 = No. of TMK parcels between 0.03 – 10 acres
Zoning District ClassificationZoning District Classification
197 = No. of parcels in the ZDC focus group (Business & Industrial)
Total Potential Project SitesTotal Potential Project Sites
220 = No. of parcels identified by HOK using GIS analysis and professional judgment of field observations.
From 27,323 TMK parcels
19,886 TMK parcels
1,432 TMK parcels
197 TMK parcels
220 TMK parcels
From 220 TMK parcels
192 TMK parcels
53 Potential LIR Projects
Potential LIR Project Site
Provides further detail not immediately apparent form the digital analyses.
Identify site specific factors which either inhibit or encourage on site LIR.
28 = No. of potential project sites excluded due to limited access beyond an external visual survey.
192 = No. of potential project sites groundtruthed
Fieldwork: What were we looking for?
Simple LIR Schematic
RSI Data SheetsRSI Data SheetsRetrofit Site Investigation
Current site conditionsLocation of storm
drainsLocation of
downspoutsWhere is runoff
originating and flowingSite conflicts
UtilitiesRight-of-way (ROW)
Opportunities for LIRSpace availability
Space Availability Space Availability
Based on physical site observations
Able to retrofit a site with minimal impact/conflicts to pre-existing requirements of a site.
53= No. of potential project sites out of 192 with space available for a physical retrofit.
High VisibilityHigh Visibility
Passive education and outreach
High traffic areasPedestrian and Vehicular
Potential project sites with higher visual access would be preferred.Raises watershed and
water quality awarenessSponsorship/Partnership
Opportunities
Hotspot Data SheetsHotspot Data Sheets
Hotspot/Pollution Prevention Current site
conditionsVehicle OperationsOutdoor materialsWaste ManagementPhysical StateLandscaping Stormwater
Structure
Prioritization parameters are established to clearly order projects according to characteristics identified as leading to successful LIR implementation.
Allows for the projects which are most easily implemented with the greatest possible impact i.e. “low hanging fruit” to be given a higher priority.
Each project might in its own right have value to overall watershed health. A lower priority project does not necessarily denote a lower possible positive impact.
Every project identified qualifies for occupant education and outreach.
NPS Pollution Retrofit Calculations NPS Pollution Retrofit Calculations
Adapted from the Center for Watershed Protection
Excel based spread sheet which automates computations for NPS pollution removal, runoff reduction, and costs based on site specific data and industry standards.
Then what?Landowner approval?Conduct soils testInfiltration testDesign
Bio-swaleRain GardenUnder drainsOther design considerationsPermitting
Start digging and dozing
ConclusionUse the watershed restoration
paradigm: Protect the best and restore the restImplement LID on new
development (protect the best) Implement LIR on the rest,
previously develop landscapes (restore the rest)
Place-based design In Kāne‘ohe, ~ 41 gals of water
annually can be infiltrated for every 1 sq. ft. of impervious surface removed
Thanks toHarold K.L. Castle FoundationCenter for Watershed ProtectionHorsley-Witten GroupNOAASierra ClubHawaiʻi’s Thousand Friends
