A REFERENCE STUDY OF THE IMPACT OF THE PROPOSED CAMPO LANDFILL
ON THE HYDROLOGY OF THE TIERRA DEL SOL WATERSHED

Victor M. Ponce

1. INTRODUCTION

There is a perceived need to study the impact of the proposed Campo landfill on the hydrology of the adjacent watershed, near the community of Tierra del Sol, in San Diego County, California. The local aquifer has been identified as a sole-source aquifer. There is concern that the close proximity of the proposed Campo landfill to the adjacent watershed may eventually lead to contamination of the aquifer, placing at substantial risk the health of the population.

This concern is heightened by the fact that the landfill site overlays a fractured rock aquifer, and that most of the fractures have been documented to run in the West-East direction, providing a hydraulic connection between the proposed landfill site and the Tierra del Sol community.

2. OBJECTIVE

The objective is to study the impact that postulated contamination from the proposed Campo landfill will have on the hydrology of the watershed immediately East of it, near the community of Tierra del Sol.

The study will review the existing conditions, including hydrology, hydrogeology, hydroecology, and stream morphology. The objective is to perform an assessment of the consequences of a possible failure of the landfill liner, in terms of the impact on the neighboring watershed. Considering the local conditions, the risk of aquifer contamination, the response time, and the effectiveness of monitoring and remediation, will be assessed.

3. SCOPE OF WORK

The study is divided into four parts:

  • Hydrologic study.

    The existing precipitation and well data will be compiled and analyzed to determine relations between rainfall and recharge, including quantity and response time of recharge. A map will be prepared showing the well data and historical record. Estimates of response time between precipitation and recharge will be sought from the data. The analysis will test the hypothesis that there is an active link between surface water and groundwater, and that the predominant path for the recharge of groundwater are the fractures in the underlying rock.

  • Hydrogeologic study.

    Data on the existing fractures will be compiled and analyzed. A map will be prepared showing the fractures that connect landfill site and watershed. The analysis will test the hypothesis that the existing fractures connect the proposed Campo landfill site and the neighboring watershed to the East of it, and that the prevailing hydraulic gradient is from West (the landfill) to East (the watershed).

  • Hydroecologic study.

    Data on existing vegetation and its relation to the existing fractures will be compiled and analyzed. Particular attention will be placed on the vegetation (trees) that habitually feed on groundwater (the phreatophytes). A map will be prepared showing the existing vegetation and its spatial relation to the fractures. The analysis will test the hypothesis that the existing trees are drawing their water primarily from the fractures.

  • Stream morphology study.

    Data on the existing stream genesis and morphology will be compiled and analyzed. Specific attention will be placed to the existing springs and other evidence of active surface-groundwater connectivity. A map will be prepared showing the location of springs and channel inceptions. The analysis will test the hypothesis that the local groundwater flow is actively and effectively connected to the surface flow.

4. DELIVERABLES

The report will summarize the work performed and provide recommendations regarding the impact of the proposed Campo landfill on the Tierra del Sol watershed.

5. WARRANTY

The Consultant will respond in writing, to formal written inquiries from third parties, in regard to the technical content of the report, for up to one year from the date of its release, with no additional cost to Backcountry.

6. TIMELINE

The Consultant agrees to deliver the product subject of this agreement no later than May 31, 2006.

If requested by Backcountry in writing, the Consultant will deliver the completed product no later than April 30, 2006, provided there is an elapsed time of 90 days from date of project approval to date of project completion.

7. HONORARIUM

The sole honorarium for the work subject of this agreement is $ 8,000.

8. PAYMENT SCHEDULE

50% at the time of project approval, and 50% at the time of project completion and delivery of the product subject of this agreement.

9. ASSIGNMENT OF COPYRIGHT

The Consultant retains the exclusive rights to the technical content of the document subject of this agreement. To publish the work openly, on the web or in the literature, the Consultant will seek prior approval of Backcountry. Backcountry can make fair use of the document, provided proper acknowledgement is made of the Consultant as author of the document.

Victor M. Ponce
Consultant

January 27, 2006