Stormwater Treatment and Flow-Control Requirements

inPhase I and Phase II Municipal NPDES Permits Dan Cloak, PrincipalDan Cloak Environmental Consulting

Outline

20-year evolution of NPDES treatment and flow-control requirements

Requirements in a nutshell●Developers●Municipalities

Phase I/Phase II differences Current trends in California Current issues in stormwater

treatment and flow control

Comprehensive Program

The California Regional Water Quality Control Board issued a permit…

…requiring municipal governments to implement a comprehensive program to control stormwater pollutants.

Municipal Maintenance

Program Elements

Illicit Discharge Prohibition

Industrial InspectionsConstruction Site Inspections

Public Outreach

Permit Provision “C.3” requires municipalities to mandate runoff controls as part of their development review procedures.

Effects of New Development

1987-1994: The Early Years

1987 Clean Water Act Amendments

1990 Phase I Stormwater Regulations

1990 First California Municipal Stormwater NPDES Permits

1992-1993

Focus on impracticability of “end of pipe” treatment

1994 Start at the Source“Do what you can where you can”

1994-1999: Experimentation

The Importance of Imperviousness

Examining barriers to better site design

Engineering criteria for treatment systems

Specification of source control BMPs

Low Impact Development

2000-Now: Getting Serious

2000 Bellflower decision

2001 Santa Clara permit reissued

2003 California Phase II permit

2006 Beginning implementation of flow-control (HMP) facilities

2007 San Diego permit mandates Low Impact Development

In a nutshell

Project designs must: Minimize imperviousness Control potential pollutant sources Treat stormwater before discharge Match runoff peaks/durations to

pre-project conditions Maintain treatment and flow-control

facilities in perpetuity

Minimize Imperviousness

Control Pollutant Sources

Material and refuse storage●Cover●Berm●Drain to sanitary sewer

Restaurant mat wash areas Vehicle wash areas Spas, pools, and fountains Landscaping

Treat Stormwater

Match Pre-project flows

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Recurrence Interval (years)

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IMP OutflowPervious Area Runoff0.5Q2Q10

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Maintain Facilities

Operation & Maintenance Plan●Responsibilities●Resources●Procedures

Conduct and document preventative & corrective maintenance

ReportsInspections

In a nutshell

All permitted municipalities must: Incorporate requirements into

development review process Review development projects for

compliance Report applicable projects

approved and measures required Verify on-site treatment devices

are maintained

Contra Costa’s Process

Stormwater Control Plan Accompanies application for planning

and zoning approval Exhibit (1 sheet)

● Site divided into drainage areas● Locations of stormwater facilities

Report (6-10 pp.)● Opportunities and constraints● Narrative explaining drainage areas and

facilities● Table of source controls● Maintenance requirements &

responsibility● Table of items to check at plan review

Stormwater C.3 Guidebook

Guidance in four formats:ChecklistStep-by-step instructionsExample outlineExample reports and

exhibitshttp://www.cccleanwater.org

Development Review

Pre-ApplicationMeeting

StormwaterControl PlanaccompaniesApplication

“DeemedComplete”

SectionReview

CEQAReview

Conditions ofApproval

Planning Planning CommissionCommission

DetailedDesign

Plan CheckPermits

toBuild

Staff Staff identifies identifies

general C.3 general C.3 requirementrequirement

ss

Staff Staff determinesdetermines

whether Plan whether Plan is adequateis adequate

Stormwater Stormwater Control Plan Control Plan attached to attached to ConditionsConditions Staff reviews Staff reviews

implementation implementation of items in Planof items in Plan

Operation & Maintenance

1. Determine ultimate ownership and maintenance responsibility

2. Identify maintenance requirements

3. Prepare a detailed Operation and Maintenance Plan

4. Operate and maintain facilities during construction

5. Formally transfer responsibilities6. Maintain facilities in perpetuity

Phase I and Phase II

Phase I—over 100,000 population● “…develop, implement and enforce

controls to reduce the discharge of pollutants… …from areas of new development and significant redevelopment.” (40 CFR 122.26)

● In California, municipalities must apply for an NPDES permit issued by Regional Board

Phase II—other urbanized areas.● “Develop and implement strategies which

include a combination of structural and/or non-structural best management practices.”

● In California, municipalities apply for coverage under a single statewide permit

Phase I/II--Requirements California Phase I permits

● Hydraulic criteria for treatment facilities● Control of peak flows and volumes● Enhanced source control measures ● Thresholds for treatment and flow-control

requirements vary from region to region California Phase II permit

● Hydraulic criteria for treatment facilities● Control of peak flows● “Design criteria” require source controls

and treatment facilities for specific land uses

Regulatory Trends

Project size thresholdsFlow control

(HMP) requirementsTreatment

Facility EffectivenessLow Impact DevelopmentExtending requirements to

smaller communities

Current issues

Consistent Implementation● Every applicable site● All impervious areas

Selecting Treatment Facilities● Targeting Pollutants● Treatment Effectiveness● Allowable loading rates for filters● Practicability on small or sloped sites

Details & Specifications● Inlet, underdrain, and overflow● Engineered soils for filtration

Facility Construction Inspection

Current issues

Operation and Maintenance●Who owns and maintains treatment

& flow-control facilities?●Financing the inspection program●Enforcing maintenance requirements●Remediation and cost-recovery●Reporting

Options●Maintenance agreements●Enforcement of stormwater

ordinance●Assign to homeowner or HOA●Benefit Assessment Districts

Current issues

Hydrograph Modification Management and:●Flood control requirements●Flood control assessments●Stream restoration programs