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Burnsville Rainwater Garden (RWG) Efficacy Monitoring and Cost Evaluation

Burnsville Rainwater Garden (RWG) Efficacy Monitoring and Cost Evaluation. West Metro Water Alliance May 31, 2011 Greg Wilson, Barr Engineering Company. Project background and objectives. Burnsville Retrofit (previous) Study—paired watershed study of RWG implementation

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Burnsville Rainwater Garden (RWG) Efficacy Monitoring and Cost Evaluation

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  1. Burnsville Rainwater Garden (RWG) Efficacy Monitoring and Cost Evaluation West Metro Water Alliance May 31, 2011 Greg Wilson, Barr Engineering Company

  2. Project background and objectives • Burnsville Retrofit (previous) Study—paired watershed study of RWG implementation • Estimated volume reduction ~90% • Follow-up effectiveness monitoring • Document maintenance • Life-cycle cost-benefits compared for BMPs • Recommendations for optimizing performance

  3. Burnsville retrofit study area characteristics Treatment area—5.3 acres, 25 homes • High homeowner participation—17 RWGs Control watershed—7.5 acres, 36 lots Both watersheds • Sandy soils • Gradual slopes • Few trees, existing landscaping • 15’ from back of curb to ROW

  4. Paired watershed study

  5. Rainwater garden layout

  6. Before and After

  7. Before and After

  8. Paired watershed schedule of BMP implementation

  9. Monitoring results

  10. Pretreatment configuration for optimum performance

  11. Conclusions and recommendations • Optimum performance of RWGs reduced runoff volumes by 90% • Current treatment level cut in half by grass filter sediment • Infiltration capacity has not been compromised • RWG implementation is • 20-30% more cost-effective in new development vs. retrofit • More cost-effective (5-15%) in front-yard ROW • Recommend pretreatment structures to improve • Cost and ease of maintenance • Long-term efficacy—10-20% more cost-effective • RWGs w/ pre-treatment are most cost-effective BMP in residential setting for long-term improvements

  12. Thank you! Questions?Funding provided by MCWD and MWMO Joint Watershed Research Grant Program Greg Wilson, PE Barr Engineering 952-832-2672 gwilson@barr.com

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