Proposed Storm Water and Grading

Policies and StandardsJanuary 13, 2011

Don McChesney

Workshop Agenda

8:30 Welcome and Overview of proposed changes: Don McChesney

9:00 TCEQ construction runoff regulations: Rebecca Scott, SECA

10:00 Break10:15 Construction runoff enforcement and support:

Derek Senter 10:30 Construction best practices: J. W. Lemons,

SECA11:20 Lake Worth Case Studies: Paul Bounds; Scott

Berman, FNI11:40 Wrap-up: Don McChesney

Workshop Goals

• Inform public of current and proposed regulations affecting storm water design and construction runoff

• Receive feedback on proposed changes and how they can be effectively implemented

iSWM—what is it?

integrated Storm Water Management is:

Managing all aspects of stormwater• collection• conveyance• storage• treatment

to achieve City goals for• protecting people and property from flooding• reducing erosion • protecting water quality of streams

iSWM—what is it?

by integrating

• Development with natural hydrology stormwater with other community needs, where mutually beneficial

• public and private stormwater systems• all phases of development from planning through

design, construction and maintenance• plan review and inspection processes

Current Stormwater Issues

• Not all development subject to review– Infill development– Single family construction– Private property grading

• Construction runoff practices inconsistent with TCEQ standards

• City Design Manual needs updating

Construction Runoff Concerns

– Lack of locally adopted, current standards – Inadequate review of erosion control plans– Change of custody by developer/builder– Monitoring of controls – Removal of controls after stabilization – Staff resources

Weaknesses in current Design Manual

– Construction and post-construction treated independently

– Local flooding failures since 2006 – Not “user-friendly”– No longer supported by regional iSWM

Strategy for addressing needs

• Adopt “Grading Permit” tying stormwater to land disturbance and building permits.

• Update standards and review requirements as part of adapting iSWM 2010

• Involve development community• Emphasize erosion control plans and SWPPP

in project review and inspections • Educate staff and public

How can we gain compliance with new standards?

• Standards must be accepted as “reasonable”

• Focus on a few key, simple to understand standards

• Challenge non-compliance • Hold individuals to account

Proposed Grading Permit• Required for land disturbances of 0.1 acres

or more• Cursory review for commercial projects

disturbing under 0.5 acres• Engineered drainage plan for disturbances of

0.5 acres or more• Final Grading Certificate required for

commercial projects prior to C.O. • Single family building permits tied to

subdivision grading plan and standard HUD drainage patterns

iSWM requiredDrainage and

FloodplainReview

How muchland is

disturbed?

Is 1 acreor more

disturbed?

Storm WaterPollution Prevention

Plan (SWPPP)required

Final GradingCertificate

Construction andgrading activities

Grading Permit

Check Urban Forestry,Land Filling and other

City requirements

0.1 – 0.5 acres

0.5 acres or more

Grading Permit Requirements for Land Disturbance Activities

Yes

No

No Grading Permitrequired

less than 0.1 acres

Grading Permit

• Commercial building permits must have approved iSWM Plan – For site or part of larger area– Adopted since May 2006– Review by Stormwater staff

Simplified Drainage Review for Small Building Permits

• iSWM by PE not required• Contractor submits site plan showing

topography, runoff arrows and nearby stormwater infrastructure

• Stormwater staff check for floodplain or other “known” problems

Grading Certificate

• At end of construction, Engineer or Contractor certifies construction completed per Grading Permit– iSWM– Urban Forestry– SWPPP

• Required prior to commercial building C.O.’s

Early (Rough) Grading Permit

• Requires approval of iSWM Conceptual Plan and Urban Forestry Phase 1 submittal

• Allowed prior to completion of detailed construction plans

• Rough grading plan can be schematic• Contractor proceeds “at risk”• Final Grading Permit still required.

Residential Drainage

• Contractor completes application for building permit

- conformance to Subdivision Grading Plan

-Standard HUD lot drainage pattern• Exceptions review by Stormwater staff• Runoff from 3 lots or more must be

contained within drainage easement

Erosion Control Plan

– Required as part of Final iSWM Plan– Engineer must certify compliance with City

and TCEQ regulations

Design standard changes

• Thermoplastic pipe usage expanded• Revised runoff coefficients for large SFR lots• Sump Inlets require structural overflow • Area inlets limited to 25 acres; must have

drainage easements for collection area • Headwalls required for 25acres drainage area• Low flow pilot channel & culvert encouraged

CFW iSWM Criteria Manual for Site Development and Construction

Major changes in 2010 iSWM

Format• Policies (“criteria) separated from

Technical Standards • Construction and post-construction

control integratedTechnical• Major update of Construction Runoff

Standards

Contents of CFW iSWM Manual

CFW definitions1.0 Overview of iSWM Criteria Manual2.0 integrated Development Process3.0 integrated Design Criteria4.0 integrated Construction Criteria5.0 Local RequirementsAppendix A – CFW Detailed Checklists and FormsAppendix B – CFW Computer ModelsAppendix C – CFW Miscellaneous Details and SpecsAppendix E – Single Family Residential Lot Drainage

iSWM 2010 Technical Standards

• Planning• Water Quality• Hydrology• Hydraulics• Site Development Controls• Construction Controls• Landscaping

Definitions

8. Grading Permit – The approval by the CFW to proceed with the disturbance of 0.1 acres or more….

9. iSWM Construction Plan – An erosion and sediment control plan prepared with the design of permanent improvements in accordance with … this Manual.

10. iSWM Plan or iSWM Site Plan – A stormwater management plan that conforms to… this Manual.

11. Stormwater Fee Credits – An incentive …to encourage the voluntary use of BMPs

17. SWPPP –… plan required by … TCEQ…. The iSWM Construction Plan covers much of the [SWPPP] site design requirements…

iSWM 2010 Format

• Common regional criteria incorporated as general text

• “Local Provisions” boxes used for

exceptions, clarifications or additions by local agency

iSWMText

Example of 2010 Format

COFW Local ProvisionsIn Box.

Step 4 – Prepare Final iSWM Plans and iSWM Construction Plan

6. An iSWM Construction Plan must be … submitted as an integral part of the final engineering documents.

7. …SWPPP must be prepared by… qualified professional…. The iSWM Construction Plan… should normally be incorporated into the SWPPP...

8. If a stormwater facility is provided which qualifies for a Stormwater Fee Credit, the engineer must submit an application.. along with a supporting documentation.

Section 3.6.3 Hydraulic Design Criteria for Structures - Culverts

For multiple barrel culverts the CFW encourages the placement of one of the barrels at the flowline… with the other barrels at a higher elevation… reduce sediment and debris accumulation. Where practical the low-flow portion of the low barrel(s) should convey 2% of the design 100-year discharge.

3.7 Easements, Plats, and Maintenance Agreements

…limited perpetual maintenance may be provided by the CFW for riparian areas preserved in their natural state, subject to the approval of the CFW.

4.3 Criteria for BMP’s During Construction

CFW allows flexibility in use of BMP's not listed in the Construction Controls Technical Manual with approval of D-TPW.

4.3.1 Erosion Controls Temporary Stabilization

Portions of a site that have been disturbed but where no work will occur for more than 21 days shall be temporarily stabilized as soon as possible, and no later than 14 days, except when precluded by seasonal arid conditions or prolonged drought.

4.3.1 Erosion ControlsNotice of Termination (NOT)

All parties that submitted a NOI shall submit a NOT within 30 days after final stabilization is established. When the owner of a residential subdivision transfers ownership … the SWPPP shall include controls for each individual lot…. Additionally, the builder must submit a valid NOI….

4.3.2 Sediment Controls

Special approval is required by CFW regarding location and design of any inlet controls. Where permitted, the operator will be expected to diligently monitor storm conditions and to remove them when there is a risk of flooding.

Implementation Schedule

Detailed discussions with area engineers and DAC

Council ITC briefed November 9 Workshops 12/8-17 & 1/13/11 Adoption by Council: January Effective date for changes: March

Resources

• Draft CFW iSWM Manual and adopted Stormwater Credit Manual are posted on Buzzsaw: Resources/20 - PM and Consultant Tools/Storm Water folder

• iSWM Technical Standards are posted at: http://iswm.nctcog.org/technical_manual.asp

Grading Permit

• New review emphasis– Type– Size

• New review starting point– Using existing design standards– Additional review

• New review end point

iSWM requiredDrainage and

FloodplainReview

How muchland is

disturbed?

Is 1 acreor more

disturbed?

Storm WaterPollution Prevention

Plan (SWPPP)required

Final GradingCertificate

Construction andgrading activities

Grading Permit

Check Urban Forestry,Land Filling and other

City requirements

0.1 – 0.5 acres

0.5 acres or more

Grading Permit Requirements for Land Disturbance Activities

Yes

No

No Grading Permitrequired

less than 0.1 acres

Final Grading Permit

Final Grading Permit, Continued

Early Grading Permit

Final Grading Certificate

Final Grading Certificate, Continued

FHA/HUD Grading

5.11 Grading Requirements Next to Building Foundation

5.5 Storm Water Facility Maintenance Agreements

Exhibit A – Legal Description

Exhibit B – Design Plan and Specifications• Design Data and Calculations• Schematic Plan• Landscaping

Exhibit C – Operations and Maintenance Plan

Exhibit D – Maintenance Checklist

Figure 5.9 Example Schematic for Dry Detention Basins

Engineer’s Checklist for iSWM Plan, Continued

7. iSWM Construction PlanA. Existing and post-development topography and

drainage featuresB. Limits of disturbanceC. BMP designD. Location, details, calculations for sediment controlsE. Location, details, calculations for waste controlsF. Sequence of construction phasesG. Phasing of temporary and permanent stabilizationH. Temporary control structures that will be converted

to permanent structuresI. Sediment TrapsJ. Top soils banked on-site

Questions?