Photo Credit: WSDOT

Catch Basin Effectiveness Study

Jenée Colton, King County Stormwater Work Group meeting

November 14, 2018

How can we use WW catch basin I&M records to inform inspection frequency needs?

Steps

RecommendationsID DriversAnalysisCompile Info

SurveysAnsweredSupplied Data

Thurston and Whatcom County submitted surveys

Loaded in Database

Survey Highlights

Less Frequent Circuit 100% CleaningStandard

Catch Basin Inspection Schedules

Uncommon

Catch Basin Definitions

Data Analysis

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Photo Credit: Oregon DOTPhoto: Dhs Commtech at English Wikimedia

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Kalama, WAPhoto Credit: Joe Mabel

• Sump dimensions• Contributing areas

• GIS delineation• Land acreage

Grate

Inlet

OutletInvert – Outlet Pipe

Top of Solids

Bottom of Sump

SUMP

Drainage Area for CB 1

Drainage Area for CB 2

Drainage Area for CB 3

Steps

RecommendationsID DriversAnalysisCompile Info

Detour

CB Z

Data Quality Issues

• C Y

Things that make you go hmmm…..

-50

-30

-10

10

30

50

70

90

110

130

150

0 500 1000 1500 2000 2500

% o

f Sum

p

Days

EverettKing CountyTacoma

0

20

40

60

80

100

120

Jan-10 Aug-10 Feb-11 Sep-11 Apr-12 Oct-12 May-13 Nov-13 Jun-14

Perc

ent F

ull

Inspection Dates

Each color is different CB

CB Z

Confidence TiersLow – less confidence

High – more confidence

• C Y

5%

7.5%

18%

14%

4%

34%

22%

Everett

Kent

King County

SPU MS4

SPU CSO

Tacoma

WSDOT

0 5 10 15 20 25 30 35 40

9.7%

9.2%

51%

0 10 20 30 40 50 60

Everett

King County

Tacoma

Percent of CBs Failing Within 2 Years: Low Confidence Tier Data

High Confidence

CB Z

Clarifications on Alternative Schedules

• C Y

CB Z

Definition of a Circuit

• CB Y • CB Z

• CB X• CB W

100% Cleaning Less Frequent andCircuit Approach

CB ZCB YCB X

CB Z

Less Frequent

• CB Z

• CB X• CB W

• No Ecology approval necessary• Documentation of proposed schedule

based on 2 x # years• Circuits based on land use, traffic density,

etc…similar maintenance needs

Marysville Circuits

• Implement/tighten data quality control (QC) protocols

Recommendations to Permittees

• Implement/tighten data quality control (QC) protocols • Migrate data collection and management to integrated digital system.

Recommendations to Permittees

• Implement/tighten data quality control (QC) protocols • Migrate data collection and management to integrated digital system. • Consider less frequent inspection schedule with own data.

Recommendations to Permittees

• Implement/tighten data quality control (QC) protocols • Migrate data collection and management to integrated digital system. • Consider less frequent inspection schedule with inspection data. • Revisit the definitions of a circuit.

Recommendations to Permittees

Recommendations to Ecology and SWG

• Standardize the definition of a catch basin to improve use of inspection data.

Recommendations to Ecology and SWG

• Standardize the definition of a catch basin to improve use of inspection data.

• Conduct field study of CB dynamics to allow for long-term, science-based prediction of CB sediment accumulation.

Acknowledgements

King County Blair ScottMark Preszler Nick HetrickBrent DhooreDoug Navetski

Osborn Consulting Inc. Diana HaseganLaura Ruppert

Technical Advisory CommitteeAngela Gallardo (Kitsap County)Laura Haren (City of Kent)Grant Moen (City of Everett)Kate Rhoads (City of Seattle)

CardnoJonathan Ambrose

SAM CoordinatorBrandi Lubliner

-20

0

20

40

60

80

100

120

140

160

0 500 1000 1500 2000

% S

ump

Full

Days Since Cleaning

Everett

King County

Tacoma

Log. (Everett)

Log. (King County)

Log. (Tacoma)

0

20

40

60

80

100

120

140

0 500 1000 1500 2000 2500

% S

ump

Full

Days Since Cleaning

Everett

King County

Tacoma

Log. (Everett)

Log. (King County)

Log. (Tacoma)