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impact of the proposed action on groundwater quality would be low and short-term during <br />construction and low and long term during mining operations. <br />Proposed Action -Residual impacts from the proposed action are that some soil would be lost to <br />surface erosion during heavy precipitation events. Some alteration in ephemeral stream flow <br />characteristics would result from construction of the mine site and stockpiles. The magnitude of <br />such changes would be of low to moderate significance. <br />Using a 10 year recurrence interval, 24 hour duration design storm to determine the volume of <br />runoff storage facilities would result in insufficient water transmission and storage capacity <br />design, since the most significant runoff events result from summer monsoonal storms which <br />have much shorter duration, and higher precipitation intensity. <br />The proposed action does not specify whether water runoff retention facilities would be removed <br />and the site(s) reclaimed as part of the final site reclamation. If these structures remained on site <br />after the mine life without receiving periodic maintenance, they would eventually fill to capacity <br />with sediment, and possibly breach, releasing stored sediment into the local surface water <br />systems. <br />Preferred Action Alternative -- The preferred alternative includes BMP's that change or are <br />additive to the proposed action to minimize impacts to water quality. They include designing <br />flood water retention facilities using the 25-year recurrence interval, 6-hour precipitation event to <br />provide for adequate storage for expected flows from monsoonal events; gravelling and/or water <br />barring the used road network, if required by the authorizing officer; and requiring the applicant <br />to remove and reclaim all water diversion and storage facilities after successful surface <br />reclamation has been completed. <br />Finding on the Public Land Health Standard for water quality: The Preferred Alternative with <br />BMPs would provide adequate protection to both surface and ground water quality that would <br />meet Public Land health Standard #5. <br />No Action Alternative -There would be no impacts to surface water or ground water. <br />WETLANDS & RIPARIAN ZONES (includes a finding on Standazd 2) <br />Affected Environment: No wetlands and riparian zones are in the vicinity of the <br />proposed project, therefore there would be no effect. <br />Environmental Consequences/Mitigation <br />Proposed Action -None <br />Preferred Action Alternative -None <br />No Action Alternative -There would be no impacts to wetlands or riparian zones. <br />17 <br />