There is no detailed map available for TA-20

PRS Erosion Matrix Score Assessment Date Structure Mesa Top Bench Canyon Floor Channel Topography Explanation Ground Explanation Slope Explanation Runoff Evidence Channelized Channel Description Runoff Wetland Runoff Other Terminus Explanation Runoff Explanation Structure Run-On Structure Explanation NPDES Run-On NPDES Explanation Natural Run-On Natural Run-On Explanation ESH-18 Representative BMP Prescription BMP Description Not BMPs Sediment Comments
20-002(d) 20.8 7/29/1998 20-29 NO NO YES NO Abandoned firing site in Sandia Canyon floor, south of the point where west bound east Jemez Road begins its ascent to South Mesa, near "LASL Survey Marker B.C. No. 926".  Photo taken from roadway Close to 75% vegetative cover.  Some bushes. Slopes gradually toward Sandia Canyon watercourse which is 150 feet to the north of this PRS. NO NO           NO   NO   NO   D. Mays     NO  
20-003(b) 27.8 7/29/1998 20-13 NO NO YES NO Former 20 mm gun firing site at north end of 300+/- yard tributary to Sandia Canyon.  East of arroyo which has cut 4+/- foot bed.  About 30 foot south of structure 7-53 "Moisture Test Well Lysimeter". Bare spot isolated in center of area, near two former concrete foundation components.  Otherwise, well covered with grass etc. Area fairly level.  Approximately 30-40 feet east of arroyo. NO NO           NO   NO   YES Some run-on likely from steep slope east of PRS but most run-on channelized by nearly arroyo. D. Mays     NO Portions of concrete foundation remain but this is not "trash/debris".  Suspect TA-20 operations eliminated in 1950s to 1960s since site is difficult to locate and tree growth appears mature.
20-003(c) 57.4 7/31/1998 20-16 NO NO YES NO Abandoned "Navy Gun Firing Site", located north of East Jemez Road about 0.5 miles west of guard house 72-8, just north of a black-on-yellow sign warning westbound motorists of a right curve. Approximately 70-80% in area south of PRS, less on former gun site. Steep slopes around former gun site lead to central rill, at which point slopes are nearly flat in floor of Sandia Canyon. YES YES Small channel runs south from site.   Meadow Evidence that runoff dissipates and infiltrates in well-vegetated meadow north of East Jemez Road which is on an earth fill at this point.  No culvert under road in this area so no direct surface water runoff. Rill approximately 6 inches deep at worst. NO   NO   YES Surrounding area drains to rill, which leads south. D. Mays     NO Since runoff terminates in a meadow.  This PRS may (or may not) be a groundwater concern, like PRS 20-005, which is across the road and 0.25 miles east.
20-004 20.8 7/29/1998 72-8 NO NO YES NO Former location of septic tank, removed in 1980s, located northeast of Guard station 72-8.  Location shown on OU 1100 RFI Report 3/19/91 p 1-4 is erroneous. Well tended grass with some weeds.  There is a flat firing range about 50 yards long between old septic site and main watercourse of Sandia Canyon, discussed in  erosion assessment 72-001 Slopes toward northwest of Building 72-39. NO NO           NO   NO   NO   D. Mays     NO  
20-005 27.8 7/29/1998 20-27 NO NO YES NO Former location of septic tank leach field.  About 0.5 miles west of old guard house 72-8, then on south side of 15 foot earth berm with power poles on top, which is south of East Jemez Road and main Sandia Canyon channel. Generally good grassy cover.  However, site is filling in with fresh mud and sand which washes from Sandia Canyon watercourse, round east end of 16 foot berm, and into PRS area which is lower than the watercourse. Nearly flat. NO NO PRS is in low spot so there is zero surface water runoff.  However, this site may (or may not) represent a groundwater concern, since surface water is flowing into the old leach field, possibly mobilizing constituents.         NO   NO   YES Remarkable fan structure formed by run-on from Sandia Canyon (please consult photograph 20-005). D. Mays   Massive earth berm north of PRS which prevents direct run-on from Sandia Canyon watercourse.  However, run-on flows around berm's east end. NO Notably, the watercourse is often the highest point in the floor of Sandia Canyon, partly due to channelization efforts such as the culvert under East Jemez Road, the earth dike north of PRS 20-005, and the sand/Jersey barrier dikes at PRS 72-001.  Since the flow can no longer meander across the historical floodplain all sediment deposits in the stream bed, raising the watercourse elevation.  Evidence of this 1) run-on to PRS 20-005, 2) sand fans at firing range, 3) culvert under road nearly full (see photo).  The lesson learned is that, in the long run, channelization efforts may complicate the control of sediments and flood hazards in streams.  Channelize with caution!