The Stormwater Issues

 

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The proposed Takoma Junction development plan is now going through the County approval process. But the City must still approve the tree plan, and the stormwater plan. So, stormwater experts with Community Vision for Takoma (CVT) analyzed the developer’s stormwater plan, and wrote this one-page summary of the many flaws in the plan.

 

TAKOMA JUNCTION DEVELOPMENT STORMWATER ISSUES

  • The City of Takoma Park has not reviewed stormwater aspects of the current proposal; the City’s approval letter in the record is based on the defunct April 2018 plan.
  • The City review of the older plan was incomplete; it did not consider many aspects of the proposal.
  • Neither the plan nor the City’s review considered the fact that nearby residents are already experiencing water management problems.
  • Currently most of the stormwater at the site flows from the City-owned parking lot to Carroll Avenue where it eventually enters City storm drains.  The developer’s plan would divert this water to a storm drain on Columbia Avenue.
  • Neither the City nor the developer conducted necessary studies including geotechnical, hydrogeological or storm sewer capacity studies.
  • Neither the soils at the construction site nor the soils on the wooded slope have been well characterized.  Clay layers in soil can make water management much more difficult; the limited studies available show clay layers on the site.
  • Stormwater can either run off over the surface or infiltrate the soil to become groundwater. This has implications for both surface drainage management and the ability of subsurface water to enter basements.  Neither the City nor the developer has studied groundwater at the site.
  • Neither the City nor the developer has assessed the potential impact of this additional stormwater on the downstream storm water management system.  It is not known if this system has enough capacity or what the potential impacts could be.
  • The proposed stormwater plan is under-designed given recent rainfall patterns and the anticipated effects of climate change in the future. The design, operation, and efficacy of the proposed stormwater management system is unclear.  The overall efficiency of the proposed green roofs has not been determined.
  • There is no analysis of water containing sediment that can accumulate in the large excavation proposed for this site.
  • In summary, it is difficult to see how this proposal meets the Maryland State guidance of controlling stormwater to the maximum extent practicable.
  • Based on all this, it is recommended that a refined comprehensive analysis, that (1) includes stormwater, groundwater and construction water and (2) is based on geotechnical and hydrogeological data, be undertaken by an independent competent authority with complete transparency.
  • This is a summary of a longer report linked here.