1 / 16

Implementation in the Falls Watershed SNAP Tool v4.1

This training session explores common problems and challenges in the implementation of the Falls Watershed SNAP Tool v4.1, including working through difficult submissions, exploring project alternatives, and development tracking.

swalker
Download Presentation

Implementation in the Falls Watershed SNAP Tool v4.1

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Implementation in the Falls Watershed SNAP Tool v4.1 – Working Through Difficult Submissions Department of Environmental Quality Trish D’Arconte Falls Local Government SNAP training | March 5, 2019

  2. In This Section • Common problems and challenges • Exploring project alternatives, working through iterated project variations • Development tracking Department of Environmental Quality

  3. Common Problems and Challenges • Hydrologic Soil Group D • Dry Detention • Catchment and SCM treatment trains • Custom Land Covers • Expansions • Expansions with existing SCMs • Off-site run-on • Alternative sizing Department of Environmental Quality

  4. Identifying Development Activity Type • Use Development – New on “greenfield” sites or in cases where previous land use is not being accounted for • Use Development – Expansion on sites with existing BUA where you will have a net increase in BUA – regardless of whether you are doing a complete tear-down or not • Use Existing Development – Retrofit when you are not building anything new except stormwater management or reforestation • Use Redevelopment with rebuilds/changes when there is no net increase in BUA Department of Environmental Quality

  5. Catchments and SCMs in Series/Parallel • Up to 6 separate parallel “catchments” that don’t have to drain to each other (but they can if you want) • Up to 3 SCMs in series in each catchment • Route SCM in one catchment to another for complex “treatment trains” • Use Catchment IDs, SCM IDs, and “Drains to SCM ID” to help you map out catchments and treatment trains Department of Environmental Quality

  6. Site With Three Catchments, No SCMs

  7. Site With 3 Catchments, Each With an SCM

  8. Site with 2 Catchments, 3 SCMs

  9. Custom Land Covers • Set aside for uncommon land cover types (e.g. dog parks) • Require values for imperviousness (0 to 1), and EMCs for nitrogen and phosphorus • Exclude jurisdictional open water from project area (perennial waterbodies, wide streams) • Include non-jurisdictional open water as CUSTOM: • Impervious value = 1, TN EMC = 1.42mg/L, TP EMC = 0.18mg/L • Contact DWR-Nonpoint Source Planning for more exotic land covers, we may have data for you Department of Environmental Quality

  10. Existing Development Retrofit • No increase in BUA, possible decrease • Project Area = area draining to SCM (including SCM) • Disturbed Area usually equals SCM Area • Unless you are reforesting, pre- and post-project will have nearly the same land cover • Land Taken Up By SCM (post-project) comes out of one of the other land covers Department of Environmental Quality

  11. Nutrient Management Strategy Rules – Thresholds Department of Environmental Quality

  12. Off-Site Run-On • Do not try to use different values for Project Area, total pre-project, or total post-project • If only interested in treatment for your site: • Design SCM to handle max off-site buildout • Model only onsite drainage area • If interested in total treatment – run model twice: • Offsite + Onsite areas together • Onsite area only • Subtract onsite only results from total area results Department of Environmental Quality

  13. Example – Expansion with SCM Enlargement • Project Objective: add a parking lot • Issues: • Disturbance threshold  more stormwater treatment • Did not want to add more SCMs • Wanted to expand existing dry detention • Wanted to offset with existing large grassy area • Dry detention is really not good for nutrient treatment Department of Environmental Quality

  14. Look at Church Development Examples Department of Environmental Quality

  15. Development Tracking • Recommend using CSV exports • No recommendations yet on formal Falls reporting • Export format has all data in rows rather than columns • Transpose data to prep data to import to a database: • Copy the columns of cells that include all field names and data. Because some parts, such as the catchment information, have more than two columns, it may be easiest to do this in groups of cells. • In another sheet select the upper-leftmost cell. Right-click and select the Transpose paste command, or access the Transpose command through Paste Special.

  16. Questions? Department of Environmental Quality

More Related