Perchlorate and Nitrate

As part of the Pesticide Monitoring Program, groundwater samples were also collected for inorganic chemical analyses. Of particular interest were the Nitrate and Perchlorate concentrations.

Perchlorate

Nine of the 60 (15%) public supply wells sampled in Nassau County exhibited perchlorate detections. The detections ranged from 2 ug/L to 6 ug/L, well below the New York State Department of Health (NYSDOH) Action Level for this compound of 18 ug/L. All detections occurred in the Magothy aquifer, with depths ranging from 298 to 682 feet. Perchlorate was found in the public supply wells from 7 different water systems and 2 water systems, Hicksville Water District and The Town of Hempstead W.S. had detections in two of their wells. Table 2 summarizes the perchlorate detections in Nassau County's public supply wells.

Table 2 - Summary of Perchlorate Detections in Nassau County Public Supply Wells
WATER SYSTEM LOCAL
WELL NO		 NYSDEC
WELL NO.		 AQUIFER WELL
DEPTH		 SAMPLE
DATE		 PERCHLORATE(UG/L)
Bethpage Water District BDG1 N-9561 Magothy 682 ft. 9/26/01 3
Garden City Village 13 N-7058 Magothy 440 ft. 9/25/01 3
Glen Cove City Kelly N-9334 Magothy 298 ft. 8/6/01 3
Hicksville Water District 6-2 N-3878 Magothy 428 ft. 10/15/01 5
Hicksville Water District 9-1 N-8778 Magothy 590 ft. 10/31/01 2
Jericho Water District 13 N-6093 Magothy 606 ft. 10/15/01 2
Roslyn Water District 8 N-8010 Magothy 448 ft. 8/14/01 2
Town of Hempstead W.S. B.G.#1 N-8956 Magothy 530 ft. 1/9/02 6
Town of Hempstead W.S. B.G.#2 N-8957 Magothy 584 ft. 1/9/02 2

Nitrate

The average nitrate concentration found in the 61 public supply wells sampled in 2001 was 2.5 mg/L and no wells exceeded the nitrate MCL of 10.0 mg/L. Well N-3523, "Munsey Park # 8", from the Manhasset-Lakeville Water District had the highest nitrate concentration of 9.8 mg/L. The range of nitrate detections is summarized below.

NO3 Detection Range >10 mg/L 5-10 mg/L 0-5 mg/L ND
# PSW Detected 0 15 28 21