Assessing Potential Impacts of the Tulla Transfer Application

To address concerns regarding groundwater/surface-water interactions and potential Rio Grande Project Supply impacts, SSP&A was retained by the State of New Mexico to provide expert hydrogeologic support in the evaluation of the Tulla Resources application (Application No. LRG 3150-E into LRG-17825) and to develop possible strategies for offsetting any potential impacts.

SSP&A evaluated the Tulla Resources application and associated numerical groundwater model, and reviewed the local hydrology, geology, and hydrogeology. Based on these reviews, SSP&A developed a conceptual site model of flow in the area between the Copper Flats Mine and Caballo Reservoir and then compared the applicant’s numerical model to the site conceptual model. The comparison included assessing model construction, features, methods of representation, hydraulic parameterization, and model calibration methods and datasets.

SSP&A identified a range of issues with the Applicant’s hydrogeologic assessment. These included inconsistencies between site hydrogeology and their model’s representation, inconsistency in water budget depletion components, and disconnects between observations used to constrain calibration (water levels near the production wells) and predictions for which the model was used (depletions at the reservoir).

To explore these inconsistencies and their potential repercussions, SSP&A evaluated sensitivity of the model predictions numerical model construction deficiencies by developing a series of alternative model parameterizations. Variability in the alternative model depletion predictions provided insight to anticipated depletion-prediction uncertainty. Results of SSP&A’s evaluation raise substantial questions regarding uncertainty of the Applicant’s model depletion predictions. Based on model inconsistencies and uncertainty, SSP&A recommended significant model revisions to produce a model consistent with the best available site data.

SSP&A also provided expert support during depositions, and hearings, assessing testimony and all technical exhibits. Expert testimony provided by SSP&A during the hearing summarized conceptual model, numerical modeling and depletion prediction issues.