Environmental Services

Citizen Monitoring on Four Mile Run


Four Mile Run is the largest stream flowing through Arlington, draining approximately two-thirds of the County. Four Mile Run flows through residential areas as well as urban corridors in the southern part of the County. Four Mile Run is listed on Virginia’s 303(d) list as an impaired waterway due to bacterial contamination (fecal coliform).  A study by the Northern Virginia Regional 
Photo of barcroft four mile run monitoring site
Barcroft monitoring site on Four Mile Run
Damselflies are found in abundance at Barcroft.
The above map shows the drainage area upstream of the Barcroft monitoring site. This map also encompasses the other Four Mile Run monitoring locations of Banneker, Bluemont, and Glencarlyn. Click on the map to view a larger, PDF version.

 Commission examined the sources of the bacteria, showing that the major sources of the identifiable bacteria were urban wildlife (waterfowl and raccoons), humans, and dogs.  A Total Maximum Daily Load (TMDL) has been created for Four Mile Run, and a management strategy for controlling anthropogenic sources of bacteria to the stream has been created. The Northern Virginia Regional Commission has more information about the Four Mile Run TMDL.

The County's urban subwatersheds have been classified as 'least impacted', 'more impacted', or 'most impacted,' in the Watershed Management Plan based on the amount of impervious cover and the results of a detailed stream inventory. Four Mile Run has been classified as a 'most impacted' watershed in the County. Lower, Middle, and Upper Four Mile Run subwatersheds have significant portions of their drainage outside the County but the impervious cover estimates for the portion of these three subwatersheds within the County appear representative of the subwatersheds as a whole. The mainstem of Four Mile Run is almost entirely within the County. In the stream inventory, Upper Four Mile Run scored 26 out of 56 on the Rapid Stream Assessment Technique (RSAT) scale, which is described as “fair.” Middle Four Mile Run scored 26 out of 56 on the Rapid Stream Assessment Technique (RSAT) scale, which is described as “fair.” Lower Four Mile Run scored 23 out of 56 on the stream inventory Rapid Stream Assessment Technique (RSAT) scale, which is described as “fair.” Watershed retrofit studies have been completed for Four Mile Run

In the fall of 2011 and spring of 2012, the County contracted a professional monitoring group to collect family/genus-level macroinvertebrate data at each of our volunteer monitoring sites. The macroinvertebrate data for each of Four Mile Run's sites are located here: Banneker ParkBarcroft Park, and Bluemont Park. Also during the fall of 2011, the fish at each of our volunteer monitoring sites were sampled. Fish data are found at the bottom of each of these documents: Banneker Park, Barcroft Park, and Bluemont Park



Four Mile Run SegmentMonitoring SitesDrainage Area MapDrainage Area, square miles
Four Mile Run, Lower MainstemBarcroft ParkBarcroft site3.1
Four Mile Run, Middle MainstemGlencarlyn ParkUpper Long Branch site (a subwatershed of Four Mile Run)4.7
Four Mile Run, Upper MainstemBanneker, Bluemont Park, Lubber Run

Banneker site

Bluemont site

Lubber Run site (a subwatershed of Four Mile Run)


















 Macroinvertebrate Monitoring

Since 2001, there have been two monitoring sites located on Four Mile Run.

  • Bluemont Park, south of Wilson Blvd, located in the upper mainstem.
  • Banneker Park, slightly downstream of the Arlington County/Falls Church City line, located in the upper mainstem.

Barcroft Park, located on the lower mainstem, was added and monitored for a short time in 2005. The site was reinstated in 2009 with new volunteer support. 

Small minnow mayflies, netspinning caddisflies, and midges are commonly found across the Four Mile Run sites. The graphs below provide greater detail for each site. The monitoring date with an asterisk (*) indicates the implementation of an updated monitoring protocol.

 Click on the graphs for a larger image. 

* indicates Arlington monitoring protocol was updated.




























































Arlington Citizen Monitoring Pages
Citizen Monitoring HomeFour Mile Run SitesDonaldson Run
Gulf Branch Little Pimmit Run Lubber Run
Windy RunMacroinvertebratesFish
Upper Long Branch  

Last Modified: December 03, 2013
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