Arlington Documents

Table of Contents:

1. 2018 Arlington Staff Presentation
2. 2021 Budget Proposal
3. Feb 25 Update (County Board Briefing) 
4. Summary of County Board Stormwater Meeting
5. Torreyson Capacity Study

1. 2018 Arlington Staff Presentation: In 2018,  Arlington experienced two major storms which caused significant flooding. In October of that year, County staff provided a briefing to the County Board which gave a broad overview of the flooding issue, including explanations of policy reforms they were then pursuing. In particular, slides 21-28 provide a clear explanation of the role that residential development plays in increasing the demands placed on a stormwater pipe system that is already overloaded. Slide 35 also provides interesting data on how rainfall rates are increasing in the region. Link: 2018 Arlington Staff Presentation.pdf
2. 2021 Budget Proposal: This document is the County staff's proposal to the Board for its 2021 budget, which begins on July 1, 2020. The discussion of stormwater issues is found primarily on pp. 26-41. Note that the specific budgetary proposals deal primarily with operating costs for the Department of Environmental Services. The major investments in stormwater infrastructure will be determined through the capital budgeting process (including the CIP priorities) that takes place later in the year. Of particular note in this presentation is slide 40, which compares the investment Arlington has been making in stormwater management, on a per household basis, to other communities in our region. Despite its strong resource base, Arlington has one of the lowest investment rates in the region for protection against stormwater flooding. Link: 2021 Budget Presentation.pdf
3. Feb 25 Update (County Board Briefing): This document is the County staff's proposal to the Board for its 2021 budget, which begins on July 1, 2020. The discussion of stormwater issues is found primarily on pp. 26-41. Note that the specific budgetary proposals deal primarily with operating costs for the Department of Environmental Services. The major investments in stormwater infrastructure will be determined through the capital budgeting process (including the CIP priorities) that takes place later in the year. Of particular note in this presentation is slide 40, which compares the investment Arlington has been making in stormwater management, on a per household basis, to other communities in our region. Despite its strong resource base, Arlington has one of the lowest investment rates in the region for protection against stormwater flooding. Link: Feb 25 Update.pdf
4. Summary County Board Stormwater Meeting 10_17_19.pdf
5. Torreyson Capacity Study:  (LINK) This document, completed by a County contractor in October 2015, provides the best available technical analysis of the stormwater management deficiencies in the Torreyson Run watershed. The document analyzes the ability of the current pipe system to handle two modeled storms - the conditions that occurred in the 2006 flooding incident in Arlington, and the conditions that would apply in what is called the "10-year, 24 hour" storm. (A 10-year storm is a rain event that has a 10% chance of occurring in any single year.) Based on this analysis, the contractor "identified design solutions to eliminate flooding" for the two modeled storms. It concluded that to prevent flooding from the 2006 storm, the County would need to add 1,210 linear feet of new pipes to 10% of the stormwater system in the Torreyson Run watershed. To prevent flooding from the "10-year" storm, the County would need to add 4,061 linear feet of new pipes to 34% of the stormwater system. Of particular interest is the map presented on p. 47 of this document, which shows where additional pipe capacity would be needed to prevent flooding from a modeled 10-year storm. This map essentially provides a blueprint of the flooding problem that occurred on July 8, 2019 in the Westover area. The overall watershed pipe system is "Y-shaped". The document shows that pipe capacity is overwhelmed at the juncture point where the two arms of this Y-shaped pipe system meet. In Torreyson Run, this juncture point occurs under the parking lot behind Westover Market and Ayers Variety and Hardware. The document also shows that additional capacity is needed in virtually all of the pipe system south of Washington Boulevard leading to Four Mile Run, an area that experienced major flooding of homes and yards during the 2019 storm.