Appendix C Surface Water and Groundwater Interaction Memorandum

Transcription

1 Texas Custodial Trust 2301 West Paisano Drive El Paso, Texas Appendix C Surface Water and Groundwater Interaction Memorandum

2 Malcolm Pirnie, Inc. 410 N. 44 th Street, Suite 1000 Phoenix, AZ T: F: September 9, 2013 Re: Subject: Texas Custodial Trust Former ASARCO Smelter Site, El Paso, Texas Surface Water and Groundwater Interaction INTRODUCTION Understanding the interaction of groundwater and surface water at the former El Paso Smelter (Site) in El Paso, TX is a key element of the Site Conceptual Site Model (CSM) and critical to remedy selection and design. Surface water on the Site includes stormwater, the Rio Grande, and the American Canal; this memorandum focuses on the two primary surface water features, the Rio Grande and the American Canal, which are downgradient receptors relative to the Site. The Remedial Action Work Plan identified the data gap of inconsistent surface water survey data preventing the comparison of groundwater and surface water elevations (Malcolm Pirnie, 2011). A more thorough evaluation of groundwater and surface water interaction will be incorporated into the Site CSM to be presented under separate cover, once the Supplemental Remedial Investigation is complete. This memorandum describes the two primary surface water features, activities conducted to address the data gap, results, and a preliminary evaluation of the hydraulic interaction of groundwater and surface water. BACKGROUND The American Canal is used to divert the United States allotment of water from the Rio Grande via the American Dam. Daily average flows are monitored at two stations by the International Boundary and Water Commission (IBWC) and used for Site evaluation: 1) Rio Grande below American Dam This station monitors the discharges from the American Dam that are not diverted into the American Canal. 2) American Canal This station monitors the flow that is diverted at the American Dam into the American Canal. Data from these stations are available to the public and can be obtained at The daily average flows, in cubic feet per second (cfs), for these two stations from 1996 through 2012 are presented in Figure 1. Figure 2 presents the daily average flows from 2008 through In general, there is minimal surface water flow (<10 cfs) from November to February in Solutions for Life TM

3 September 9, 2013 Page 2 of 5 the Rio Grande; flow is generally <100 cfs in the American Canal during this time. Seasonal operation of American Dam results in increased flows from approximately March through October with the annual peak flow generally occurring in July. The following observations were made based on these surface water flows: Flows in the American Canal during the seasonal operation range from approximately 250 to 1,100 cfs. The average flow in the Rio Grande below the American Dam during the seasonal operation is approximately 175 cfs. There are rare but significant high flows in the Rio Grande below the American Dam caused by precipitation events during the monsoon season (e.g. 2,624 cfs on August 24, 1999 and 3,779 cfs on August 1, 2006). Surface water conditions along the Site boundary are controlled by the seasonal operation of the American Dam and, to a lesser extent, precipitation events during the monsoon season. These conditions are critical to understanding the groundwater-surface water interactions at the Site. DATA COLLECTION AND RESULTS Malcolm Pirnie contracted a Texas-licensed surveyor, Land-Mark Professional Surveying, Inc. (Land-Mark), to survey Site features and establish a consistent datum for future Site activities (Attachment A). A primary objective of this survey was to collect accurate survey data on the American Canal and establish a consistent datum so that groundwater and surface water elevations could be compared and used to evaluate groundwater and surface water interactions in the vicinity of the American Canal. In April 2011, Land-Mark conducted a survey of all groundwater monitoring wells at the Site and a survey of the American Canal and the water elevation in the American Canal. The survey was conducted and reported in Texas State Plane, Central Zone (North American Datum of 1983) coordinates. This datum will be used for future Site activities conducted by Malcolm Pirnie; where possible, historical information from previous Site activities has been adjusted to this new datum including historical site topographic contours and groundwater elevations. The survey included multiple points along the American Canal as shown on Figure 3. The cluster of survey points 1052, 1054, 1055 and 1066 were collected in the vicinity of the IBWC American Canal gauging station. Survey point 1054 was the instantaneous water elevation in the American Canal ( feet above mean sea level [amsl]) which was compared to the elevation reported by the IBWC. This comparison yielded a correction factor of feet to adjust all IBWC-reported American Canal surface water stages to the same elevation datum as Site groundwater elevations.

4 September 9, 2013 Page 3 of 5 Following the surveying, an Interim Site Monitoring Event was performed in February 2012 and a high-resolution pressure transducer study of groundwater and surface water levels was conducted from March 27 through April 18, Figure 4 presents the potentiometric surface contours reflecting the February monitoring event and the groundwater wells selected for the high-resolution water level study. The study involved four monitoring wells (EP-119, EP-66, EP-32, and EP-20) all within 100 feet of the American Canal. Groundwater levels were collected every 30 minutes from down-well pressure transducers. Groundwater levels collected from the pressure transducers were corrected for the effects of barometric pressure assuming 100% efficiency. Surface water elevations reported by the IBWC were corrected to account for their upgradient or downgradient distance from the IBWC gauging location based on assumed constant flow depth and a canal slope of feet per foot (ft/ft) (MWH, 2002). The following are American Canal surface water corrections for locations adjacent to each groundwater monitoring well: Adjacent to EP-119 correction = feet Adjacent to EP-66 correction = feet Adjacent to EP-32 correction = feet Adjacent to EP-20 correction = feet RESULTS The Rio Grande River serves as the discharge point for site groundwater, as is indicated by the groundwater potentiometric surface map (Figure 4). American Canal surface water elevations were corrected for comparison to groundwater elevations within the floodplain. Graphical comparisons of the groundwater elevations in EP- 119, EP-66, EP-32, and EP-20 to the surface water elevations of the American Canal throughout the pressure transducer study are presented in Figure 5. The results indicate that when the American Dam is not operating (i.e., water is not being diverted to the American Canal), the groundwater elevation in the floodplain is higher than the surface water elevation in the American Canal and the canal bottom. When the American Dam diverted water to the American Canal during the study period, water levels in the American Canal increased by a maximum of approximately 5.1 feet and groundwater elevations increased by approximately 2 to 4 feet. The water elevation in the American Canal during operation is approximately 1 to 3 feet above that of adjacent groundwater, resulting in losing conditions.

5 September 9, 2013 Page 4 of 5 CONCLUSIONS An evaluation of the groundwater potentiometric surface indicates that the Rio Grande River is a gaining stream that is recharged by site groundwater. These data confirm a strong hydraulic connection between the surface water and Site groundwater in the floodplain. Specifically, the American Canal is under gaining conditions during the fall and winter months (November through March) when the American Dam is not operating. During the spring and summer months (March through November), as water is being diverted into it, the American Canal is under losing conditions. As the American Canal surface water elevation increases, groundwater elevations increase as a result of leakage from the American Canal recharging nearby groundwater. This evidence of hydraulic connection between groundwater and the American Canal also suggests that the American Canal is under gaining conditions during the fall and winter months. This is likely the result of deterioration of the American Canal channel and observed weeps (MWH, 2002).

6 September 9, 2013 Page 5 of 5 REFERENCES Malcolm Pirnie Final Remedial Action Work Plan (RAWP). Former Asarco Smelter, El Paso, TX. March Montgomery Watson Harza (MWH) Conceptual Design Report American Canal Lining Replacement Study. International Boundary and Water Commission. June 7. ATTACHMENTS Figure 1 Surface Water Flows ( ) Figure 2 Surface Water Flows ( ) Figure 3 American Canal Survey Elevations Figure 4 Sitewide Groundwater Potentiometric Surface Map February 2012 Figure 5 Appendix A Transducer Study Results Survey Report

7 CITY: Highlands Ranch DIV/GROUP: GIS DB: BG Project (Project #) Path: I:\ASARCO_ElPaso\GIS\MXD\Misc\Fig 1 SurfaceWaterFlow_1996to2012.mxd Date: 10/17/2013 Time: 1:26:50 PM 0 Dec-12 Dec-11 Dec-10 3,779 cfs; 8/1/2006 American Canal Monthly Precipitation 1,750 1, , , Precipitation, inches Rio Grande Below American Dam Dec-09 2,500 Dec-08 Dec-07 Dec-06 Dec-05 Dec-04 Dec-03 2,000 Dec-02 2,624 cfs; 8/24/1999 Dec-01 Dec-00 Dec-99 Dec-98 Dec-97 2,250 Dec-96 Dec-95 Flow, cfs Figure 1 - Surface Water Flows ( ) FORMER EL PASO SMELTER SITE EL PASO, TEXAS SURFACE WATER FLOWS ( ) FIGURE 1

8 CITY: Highlands Ranch DIV/GROUP: GIS DB: BG Project (Project #) Path: I:\ASARCO_ElPaso\GIS\MXD\Misc\Fig 2 SurfaceWaterFlow_2008to2012.mxd Date: 10/17/2013 Time: 1:44:28 PM 0 Jul-12 Dec-11 Jun-11 2,000 Rio Grande Below American Dam American Canal Monthly Precipitation 1, , Precipitation, inches 1,500 Nov-10 1,750 May-10 Oct-09 Mar-09 Sep-08 Feb-08 Flow, cfs Figure 2 - Surface Water Flows ( ) FORMER EL PASO SMELTER SITE EL PASO, TEXAS SURFACE WATER FLOWS ( ) FIGURE 2

9 CITY: Highlands Ranch DIV/GROUP: GIS DB: BG Document Path: I:\ASARCO_ElPaso\GIS\MXD\Misc\Fig 3 AmericanCanalSurveyElevations.mxd Date: 10/17/2013 Time: 1:19:27 PM LEGEND: Survey Points Arroyo Trace Lines Property Boundary Historical Drainage Divide Rio Grande American Canal ,200 GRAPHIC SCALE Feet Rio Grande American Canal FORMER EL PASO SMELTER SITE EL PASO, TEXAS AMERICAN CANAL SURVEY ELEVATIONS FIGURE 3

10 EP EP EP CITY: Highlands Ranch DIV/GROUP: GIS DB: BG Project (Project #) Path: I:\ASARCO_ElPaso\GIS\MXD\Misc\Fig 4 SitewideGWPotSurface_Feb2012.mxd Date: 10/17/2013 Time: 2:20:19 PM LEGEND: Monitoring Wells Water Level Contour (ft) Historic Arroyo Trace Lines Property Boundary 3805 Transducer Study - Monitoring Well EP EP EP EP EP Note: *Wells not used to construct contour 3735 EP EP EP EP EP Rio Grande EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP *EP EP EP *EP *EP EP EP EP EP EP EP ,200 GRAPHIC SCALE American Canal Feet 3750 EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP EP Rio Grande EP EP EP EP EP EP EP EP EP *EP EP EP EP EP EP EP EP EP EP EP American Canal EP FORMER EL PASO SMELTER SITE EL PASO, TEXAS SITEWIDE GROUNDWATER POTENTIOMETRIC SURFACE MAP FEBRUARY 2012 FIGURE 4

11 3724 EP EP Elevation (ft amsl, NADV 88) Elevation (ft amsl, NADV 88) EP EP CITY: Highlands Ranch DIV/GROUP: GIS DB: BG Project (Project #) Path: I:\ASARCO_ElPaso\GIS\MXD\Misc\Fig 5 TransducerStudyResults.mxd Date: 11/7/2013 Time: 1:33:07 PM Elevation (ft amsl, NADV 88) Elevation (ft amsl, NADV 88) FORMER EL PASO SMELTER SITE EL PASO, TEXAS TRANSDUCER STUDY RESULTS FIGURE 5

12 ATTACHMENT 1 SURVEY REPORT

13 Land - ill ark Inc. May 20, 2011 Ms. Alicia Fogg Malcolm Pimie, fnc. 2ll N. Florence Street, Suite 202 EI Paso, Texas 7990 I Ref Project: Former ASARO) property, EI Paso, Texas. Ms. Fogg, Tabulated below is the point data for the above referenced project. Coordinates are Texas State Plane, Central Zone (NAD 83 Datum) and are in U.S. Survey Feet. Elevations are based on NGS Vertical Control Monument Q460. Record Elevation is (NAVD 88 Datum) NO. NORTH (sft) 3879A : Bessemer El Fax:

14 , EP-62 /N. TOPCASING

15 ELEVATION G

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19 LAND-MARK)?ROFE~IONAL SURV~ ~ INC. \. I L. Drewes, R.P.L.S. Texas License No Date of Survey: April 26, 20 II Job# 28053

20 Sheet 1 Point # Northing Easting Elevation Description Misc. Data WATER ELEV RIVER WATER ELEV CANAL WATER ELEV S.DAM TC END CANAL N.lBWC TC@GAGING BRIDGE WATER ELEV WATER ELEV TC@GAGING BRIDGE TC@MAIN ENTRANCE TC@MAIN ENTRANCE TC CANAL E.PAISANO TC CANAL E.PAISANO TC CANAL E.PAISANO Well Data EP-49rrG EP-49rrOp N.CASING EP-49rrOp MO~ EP-92rrG \ EP-92rrOp N.CASING \ EP-92rrOp MON ~~, EP-126rr A EP-126rrOp N.CASING EP-126rrOp MON EP-19rrG EP-19rrOp CASING EP-19rrOp MON EP-36rrG EP-36rrOp CASING EP-36rrOp MON EP-57rrG EP-57/N.TOP CASING EP-57rrOp MON EP-5rrG EP-5/N.TOP CASING EP-5rrOp MON EP-134rrG EP-134/N.TOP CASING EP-134rrOp MON EP-25rrG ~ EP-25/N.TOP CASIN \ EP-25rrOp MON v> EP-52lfA ~ EP-52/N.TOP CASING EP-52rrOp MON EP-100rrC EP-100/N.TOP CASING EP-100rrOp MON EP-51 rrc EP-51/N.TOP CASING EP-51rrOp MON Page 1