Eric Strecker, PE Geosyntec Consultants Portland, OR USA.

Transcription

1 Eric Strecker, PE Geosyntec Consultants Portland, OR USA 1 estrecker@geosyntec.com

2 New Development and Re-Development Most larger Cities have requirements for new and redevelopment SUDs. US Terms: BMPs = Best Management Practices LID = Low Impact Development Retrofitting Most retrofitting has been completed due to specific watershed requirements ( distributed CSO control, Lake Tahoe, etc.) Very little separated stormwater system applications (usually grant projects) Regional vs. localized SUDs Retrofits 2 2

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5 5 About $1,000,000 for one block 98% runoff reduction Mostly infiltration losses Natural groundwater recharge level?

6 Before After 6

7 7 About $30,000 per block Less effective per block But how many blocks?

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12 Orange San Diego Creek Watershed Boundary Tustin Irvine Peters Canyon Wash Santa Ana/Santa Fe Channel Upper Newport Bay San Creek Diego San Diego Creek Peters Canyon Wash near Edinger Avenue. Lake Forest Newport Beach N Miles 12

13 N San Diego Creek Watershed Boundary Upper Newport Bay San 45 Newport Beach Miles Tustin A Creek Diego Orange Peters Canyon Wash Irvine San 7 9 Diego Creek Lake Forest 25 Type 1- Offline Water Quality Wetlands Type 2 - Inline Water Quality Wetlands Type 3 - Water Quality Wetlands within Existing or Proposed Detention Basin Sites excluded from selected NTS Plan More than 70 sites considered Many sites modified or eliminated for: feasibility or political constraints wildlife or habitat impacts flood control impacts 31 NTS facilities in current Plan Plan has mechanism for adding or deleting sites

14 City of Orange After Before 14 14

15 CSO Control Primary Driver TMDLs Total Maximum Daily Loads Driver in some locations NPDES Permit Requirements Typically no specific requirements

16 CSO Control has resulted in extensive analysis of retrofitting (Portland Example) Separated areas, much fewer examples: SBPAT Heal the Bay, City/County of LA Available from City Lake Tahoe BMP Retrofit Tool US Army Corps Under development Sustain EPA In limited beta testing not available

17 Specific Objectives of Methodology and Tool To maximize water quality benefits of constructed controls in watersheds (based on best available information). To use methodical and disciplined, science-based analyses to break-down large areas, and then prioritize and build-up suites of targeted activities in manageable sizes which results in measureable progress to achieving water quality goals. To understand and quantify potential benefits with suites of BMP activities. 17

18 18 Develop water quality goals for each watershed to be evaluated based upon: TMDLs 303D listings Typical Urban Pollutants of Concern Hydromodification Issues (wet and dry weather)

19 Catchment Prioritization Index (CPI) Determination Begin Area Screening (GIS) Step 1 Catchment Prioritization Account for downstream impairments (303d listed or completed TMDLs) Compute Normal CPI Scores es2 Compute Nodal CPI Scores Compile GIS Themes Result: Set of High CPI Score Catchments Estimate Pollutant Loads or Concentrations Step 2 Project Area Screening 19 Normalize Pollutant Loads (LCPI) or Concentrations (CCPI)

20 Project Area Screening for BMPs Regional/Subregional BMPs Distributed BMPs Step 2 Project Area Screening Overlay BMP Opportunities with High CPI Catchments From STEP 1 Compile GIS Themes Result: Set of High CPI Score Catchments with BMP Opportunity Catchments Identified Regional BMP Opportunity Identification Distributed BMP Opportunity Identification Begin BMP Screening 20 Compute Regional and Distributed BMP Scores and Prepare BMP Opportunity Maps Step 3 General BMP Screening

21 Effectiveness Other Benefits es3 Ease of Implementation Cost 21

22 Critical Step in process A. GIS- Level B. Desktop- Level C. Field- Level Step 4 Site Specific BMP Evaluation Compile GIS Themes GIS-Level Screening Desktop-Level Screening Fill in GIS-Screening Section of Fatal Flaw Matrix Completed BMP Fatal Flaw Matrix Complete Field Summary Table and Recommended Projects List Complete BMP Comparison Matrices (update values entered in Step 3) Field-Level Screening Fill in Desktop-Screening Section of Fatal Flaw Matrix Result: Set of Priority Catchments with Ranked BMP Options (Fatally Flawed BMPs Eliminated) Select Highest Priority Projects for Further Evaluation (END) Fill in Field Data Sheet & Field-Screening Section of Fatal Flaw Matrix 22

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24 User Input Source Controls Hydrologic Simulation Pollutant Load Generation Storm Water Treatment Pollutant Load 24

25 Unit processes and BMP Performance Based International BMP Database + Tahoe BMP information Unit Processes based modeling of hydrology/hydraulics and particle settling 25

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27 Gaining popularity as a method to address runoff where infiltration is difficult or not wise Challenge is being able to use the water to recover storage before next storm arrives In areas where storms tend to be back-to-back and colder climates, use for irrigation is limited Must look at toilet flushing or other consumptive uses Density of toilet flushers to impervious area ratio (TFIA) needs to be higher to make re-use feasible as a viable approach (or other uses besides normal irrigation) 27

28 Importance of water balance: Runoff, evapotranspiration (ET), deeper infiltration Much of LID focuses on surface hydrology (runoff) and could potentially impact water balance Pre-development ET is a significant component of water balance. In dense urban areas very hard to match predevelopment ET Therefore, one may over-infiltrate to achieve surface hydrology goals Over-infiltration can be a problem (or not) Pay attention to unit processes 28

29 Ready, Aim, Aim, Aim or (Planning to death) Ready, Fire, Aim or (Forget Planning just implement) Or Ready, Aim, Fire? (Just right)