Caltrans Long Range Strategy

1
Urban Hydrology
2
Construction Impacts

• Disturbed areas allow erosion to occur
• High concentrations of sediment can impact creeks
  and ponds
• Construction General Permit
• Storm Water Pollution Prevention Plan (SWPPP)
  must be prepared for project
• Plan specifies measures to reduce discharge of
  sediment

3
Silt Fence
4
Hydromulch
5
Control Failure
6
Degradation of Hill Country Streams
Green Hole on Lick Creek, west Travis County,
Summer 2003
Green Hole on July 27, 2004, after rainfall
caused overflow from the West Cypress Hills
subdivision detention pond for development
construction
7
Degradation of Hill Country Streams (cont.)
Dead Mans Hole on Dead Mans Creek, east Hays
County, before construction of a small dam in the
watershed
Dead Mans Hole after construction of the dam
8
Degradation of Hill Country Streams (cont.)
Road cut for land development in Hamilton Creek
basin began June, 2007
Hamilton Pool prior to June 2007
9
Degradation of Hill Country Streams (cont.)
Road cut along Hamilton Creek
Hamilton Pool--first rain after road cut
construction began
10
Bee Creek
Bee Creek near Hwy 71, West Travis County, prior
to development in basin
Bee Creek, August 2007, immediately after
development began in basin
11
Austin Rainfall/Runoff
12
Channel Degradation
Bear Creek
Fort Branch
ShoalCreek
Boggy Creek
13
More of the Same
Little Walnut Creek
E. Bouldin Creek
Shoal Creek
Walnut Creek
Tannehill Branch
14
Shoal Creek
15
(No Transcript)
16
Types of Pollution

• Point Sources
• Conventionally industrial or wastewater treatment
• Any discharge from a pipe or ditch
• Non-Point Source
• Agriculture

17
Constituents in Urban Runoff

• Bacteria
• Nutrients
• Insecticides
• Herbicides
• Metals zinc, copper, lead
• Hydrocarbons PAHs
• Sediment

18
Sources of Pollutants

• Vehicles Tires, Brake pads, Fluids, Tracking
• Atmospheric Deposition
• Fertilizers
• Pesticides
• Pets
• Pavement abrasion
• Channel Erosion

19
Buildup of Pollutants
20
First Flush of Pollutants
21
Zinc vs. Impervious Cover
22
Copper vs. Impervious Cover
23
TSS vs. Impervious Cover
24
Runoff Concentrations
Constituent Avg. C Standard Exceedance
Gross Solids ??? 0 100
Lead 49 mg/L 0.66 97
Copper 39 mg/L 3.2 97
Zinc 207 mg/L 41 52
Fecal C. 1415 400 42
25
Runoff Concentrations
Constituent Avg. C
Sediment 100 mg/L
Nitrate 0.93 mg/L
TKN 2.1 mg/L
Total P 0.11 mg/L
Diss. P 1415
26
Other Sources of Pollutants
Sealants reapplied every few years. About 600,000
gallons of sealant are applied annually in
Austin.
coal-tar-emulsion-sealed
asphalt-emulsion-sealed
unsealed asphalt or concrete
27
Sewer Lines in Creeks Tannehill Branch
28
Barton Creek Wastewater Leak
Algae blooms March 2, 2002
29
Regulatory Strategies

• Do nothing
• Do something (structural)
• Meet a performance standard
• Meet water quality standards

30
Local Requirements

• Austin Achieve pollutant reduction comparable
  to a sand filter system, or no discharge of
  stormwater.
• LCRA Reduce TSS, TP, and OG by 75
• TCEQ Reduce the increase in TSS discharged by
  80.
• Houston Do something

31
Filter System Lamar Loop 360
32
Uniform Distributed Small-scale Controls
Maintaining Natural Hydrology Functions