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4.2.7 Ground Water Orthophosphate and Nitrite <br />' Charts 34 and 35 show orthophosphate and nitrite concentrations for the monitoring wells TR- <br />1.5, TR-3, TR-4, WR-1 and TCS-1 for the period of record. Historically, orthophosphate and <br />' nitrite values obtained over the period of record have been low with most being below detection <br />limits. Elevated orthophosphate readings occurred in the summers of 1998 through 2000, at up- <br />gradient well TR-1.5, possibly due to nearby agricultural activity. In 2001, concentrations of <br />' orthophosphate returned to historically low levels. Site TR-4 had a slight rise in orthophosphate <br />concentration during the 2005 monitoring period, but decreased to levels similar to previous <br />sampling events during the past few years. Nitrite concentrations were again elevated at TR-1.5 <br />' in May 2000 and May 2001 and at WR-1 in May 2001, but decreased to historical levels as the <br />year progressed. Nitrite levels remained at historical levels in the 2009 monitoring period. The <br />lowest orthophosphate concentration in 2009 was recorded at monitoring well WR-1 with a value <br />0.01 mg/L and the high was recorded at monitoring well TR-4 in August with a value of 0.07 <br />mg/L. The lowest nitrite concentration in 2009 was recorded at numerous monitoring wells <br />during numerous events with a value of <0.01 mg/Land the high was recorded at monitoring <br />' well TR-4 in August with a value of 0.13 mg/L. <br />1 4.2.8 Ground Water Chloride and Potassium <br />' Charts 36 and 37 show chloride and potassium concentrations for the monitoring wells TR-1.5, <br />TR-3, TR-4, WR-1 and TCS-1 for the period of record. Chloride and Potassium were added to <br />the parameters list in 1994. Potassium levels increased in TR-4 over the course of 2003, but <br />' have leveled off over the last few years. Chloride at TIt-4 spiked in both October 2004 and May <br />2005, however concentrations returned to historical levels over the past few monitoring periods. <br />Chloride has risen over the past 5 monitoring seasons at TCS-1. The lowest chloride <br />concentration in 2009 was recorded at monitoring wells TR-3 and WR-1 in May with a value of <br />2 mg/L and the high was recorded at monitoring well TCS-1 in May with a value of 70 mg/L. <br />The lowest potassium concentration in 2009 was recorded at monitoring well TR-3 in May with a <br />' value of 1.1 mg/L and the high was recorded at monitoring well WR-1 in May with a value of <br />11.3 mg/L. <br />??^wWCENGINEERING Page 15