20241106-002: Colorado River Protections Staff Presentation — original pdf

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Colorado River Protections Ordinance E n v i r o n m e n t a l C o m m i s s i o n N o v e m b e r 6 , 2 0 2 4 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 2-Minute Summary Video C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 3 Ordinance Youtube video link Council Resolution Community members asked Council to strengthen Colorado River protections; Council thereafter included in their June 2022 Council resolution: “… evaluate the effectiveness of existing Critical Water Quality Zone and Erosion Hazard Zone buffers on the Colorado River downstream of the Longhorn Dam and to propose protections that will provide adequate protections to the river that will ensure a healthy riparian corridor to stabilize the riverbank and protect property from erosion” C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 4 East Austin Longhorn Dam J. Trevino Metro Park Lady Bird Lake Roy Guerrero Park “Dog’s Head” Austin’s Colony Hornsby Bend Biosolids Plant Tesla SHEC/SAR WWTP Southeast Austin Parcel Count Acres Juris- diction Type CWQZ Buffer Acres 400ft Buffer Acres Acres 400ft minus CWQZ FULL ETJ Totals FULL ETJ Totals 241 243 484 50% 50% 100% 1,054 14,896 15,950 7% 93% 100% 281 1,929 2,211 13% 87% 100% 391 2,184 2,575 15% 85% 100% 109 255 ABIA 364 30% 70% 100% Travis County Colorado River City Limits & ETJ 6 Single-Family Residential Parks & Open Space Industrial Parks & Open Space Agriculture / Undeveloped Parks & Open Space Mining Single-Family Residential Utilities C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T Colorado River Land Uses 7 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T Colorado River Geology 8 Erosion Threats  Unique, highly erosive alluvial soils  River massively larger than creeks  Seeing major erosion problems  Erosion Hazard Zone (EHZ) code requirements designed for creeks  Tens of millions of dollars in damage and counting… C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 9 $1.9M Tillery St. Outfall Repair Erosion Threats  Unique, highly erosive alluvial soils  River massively larger than creeks  Seeing major erosion problems  Erosion Hazard Zone (EHZ) code requirements designed for creeks  Tens of millions of dollars in damage and counting… Road is sole access to two critical infrastructure facilities C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 11 Fallwell Lane: $11.4M needed to stabilize bank Erosion Threats  Unique, highly erosive alluvial soils  River massively larger than creeks  Seeing major erosion problems  Erosion Hazard Zone (EHZ) code requirements designed for creeks  Tens of millions of dollars in damage and counting… C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 13 Home threatened after 20ft bank failure, May 2015 Erosion Threats  Unique, highly erosive alluvial soils  River massively larger than creeks  Seeing major erosion problems  Erosion Hazard Zone (EHZ) code requirements designed for creeks  Tens of millions of dollars in damage and counting… C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 19 Roy Guerrero Park: Bridge destroyed Austin’s Colony Phase 2: No Stable Channel Original ground level 25ft canyon C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 22 Failing outf alls, insuf ficient armoring f or outf all creek or along drainage path to creek C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 23 Water Quality Threats, Historical Context  Riparian zone long compromised  Initial transformation by agriculture  Then by sand and gravel mining  And by upstream Highland Lakes dams altering flow and sediment regimes  River water quality primarily affected by upstream flows; secondarily by large creek tributaries  Direct drainage (buffers) less influential C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 1940 2021 24 Water Quality Threats & Historical Context Travis County’s existing 400ft buffer  200-400ft Critical Water Quality Zone buffer in 1986*  Buffer improved by 2008 ordinance to ensure full expected buffer width  Buffer remained unchanged with the 2013 Watershed Protection Ordinance  Current buffer narrower than 400ft Travis County river and City of Austin Barton buffers * By the 1986 Comprehensive Watershed Ordinance (CWO) C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 25 Draft Ordinance Proposal Recommended 1 2 200ft Erosion Hazard Zone (EHZ) buffer (except trails) New technical specifications for stormwater discharges to the river Evaluated but Not Recommended 3 400ft Critical Water Quality Zone (CWQZ) buffer C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 26 1 200ft Erosion Hazard Zone (EHZ) buffer Existing: EHZ review buffer width is 100ft L a d y B i r d L a k e Erosion Hazard Zones: Regulatory protection to ensure that new buildings and infrastructure built near waterways are located at a safe distance and/or designed with protective works to help prevent future damage to these resources from creek and river erosion. C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 27 1 200ft Erosion Hazard Zone (EHZ) buffer Existing: EHZ review buffer width is 100ft L a d y B i r d L a k e Proposed: Expand review buffer to 200ft Erosion Hazard Zones have NO IMPACT on existing structures or properties. They ONLY apply to newly proposed buildings and infrastructure. C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 28 Proposal: Erosion Protections 1 200ft Erosion Hazard Zone (EHZ) review buffer • Expanded from current 100ft review buffer width • Only applies to new “habitable space” and infrastructure • No change for hard-surfaced trails (100ft EHZ remains the same) • Does not extend beyond parallel public roads • NO IMPACT on existing structures or new driveways, decks, etc. • NO IMPACT on new subdivision or commercial projects • Potential impact on redeveloping commercial projects C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 29 Level 1 EHZ Diagram: Existing 100ft EHZ Review Buffer Protective works or Engineer Level II required Protective works not required Outside EHZ 100ft EHZ Review Buffer Water surface Starting point = lowest surface contour line Outside of critical slope C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 31 Level 1 EHZ Diagram: Proposed 200ft EHZ Review Buffer Protective works or Engineer Level II required Protective works not required Outside EHZ 200ft EHZ Review Buffer Water surface Starting point = lowest surface contour line Can use topo contour in Property Profile web tool Outside of critical slope C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 32 Level 1 EHZ Diagram: Proposed 200ft EHZ Review Buffer Protective works or Engineer Level II required Protective works not required Outside EHZ 200ft EHZ Review Buffer Water surface 20ft Place subsurface utilities min. 20ft below channel bottom (if less must demonstrate via Level 2 analysis) C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 33 Level 1 EHZ Diagram: Proposed End EHZ Review Buffer at ROW edge Protective works not required Protective works or Engineer Level II required Protective works not required Outside EHZ Existing public road right-of-way 200ft EHZ Review Buffer Water surface 20ft C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 36 2 New technical specifications for stormwater discharges to the river Existing: Storm drainage systems causing severe erosion $$$ Proposed: Build non-erosive structures to curb damage Armored stormwater discharge infrastructure: engineering solutions designed to reduce the erosive energy from stormwater flows from developed areas to reduce erosion and related property damage and loss. 37 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T C o l o r a d o R i v e r C o l o r a d o R i v e r Proposal: Non-Erosive Stormwater Discharges 2 New technical criteria and specifications for outfalls to river 40ft. 66" pipe C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 38 Tillery Street Storm Drain Outfall Repair Example Drop Structure for Outfall Water from surface runoff Non-erosive passage to river Armoring Col. River C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 39 Water from storm drainage system Energy of flowing and falling water entirely contained within structure Tillery St. Outfall Structure Diagram Austin’s Colony Phase 2: No Stable Channel 40 Austin’s Colony Phase 4: Stable Channel 41 Austin’s Colony Phase 4: Stable Channel 42 3 400ft Critical Water Quality Zone (CWQZ) buffer Existing: CWQZ buffer width varies from 200 to 400ft L a d y B i r d L a k e Critical Water Quality Zones: Regulatory buffers to reduce the intensity of new development directly adjacent to waterways to protect natural riparian soils and vegetation that protect water quality and flows; low-intensity uses are P u r p l e a r e a s s h o w 1 0 0 - y e a r f l o o d p l a i n s permitted; high-intensity uses are restricted. C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 43 3 400ft Critical Water Quality Zone (CWQZ) buffer Existing: CWQZ buffer width varies from 200 to 400ft L a d y B i r d L a k e *** NOT RECOMMENDED *** Existing buffers provide good protection, best fit the terrain P u r p l e a r e a s s h o w 1 0 0 - y e a r f l o o d p l a i n s C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 44 Studied: Fixed 400ft buffer width Overview of Staff Ordinance Proposal 1. 200ft Erosion Hazard Zone (EHZ) review buffer  RECOMMENDED  More accurate recognition of erosion risk  Most properties along river not impacted; not applied to hard-surfaced trails 2. New technical specifications for stormwater discharges to river  RECOMMENDED  Low-cost solution relative to much higher damage/costs 3. 400ft Critical Water Quality Zone (CWQZ) buffer  NOT RECOMMENDED  High impact on some properties; high banks not where protection needed; water quality protection more in upstream flows and larger tributaries C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 45 Schedule Since 2023 Sep./Oct. Oct. 28 Oct./Nov./Dec. Oct. 16 Nov. 6 Nov. 12 Dec. 12 Dec./Jan./Feb. Develop staff recommended ordinance Gather stakeholder input on ordinance In-Person WPD outreach meeting (Montopolis Rec. Center) Present ordinance to Commissions and Council Codes & Ordinances Joint Committee Environmental Commission Planning Commission City Council Develop/solicit stakeholder feedback on Criteria Changes Interactive map of Erosion Ordinance C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 46 Discussion C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 47