Table 3. Infiltration gallery discharge monitoring

Table 3. Infiltration gallery discharge monitoring.

several times because of high concentrations of

NO3 measured in the monitoring wells. Prob-

Benzene

Btex

NO3

lems were also encountered when the nutrient

(g/L)

(mg/L)

feed pump clogged several times.

Date

1 Dec 2 Dec

1 Dec

2 Dec

a. 1991

Parameters monitored at the infiltration gal-

23 Aug

--

lery included soil and groundwater temperatures

26 Aug

--

0.05

0.28

to a depth of 20 ft (6.1 m), nutrient feed rate and

03 Sep

<DL

0.43

0.45

concentrations, pumping well flow rate, and

10 Sep

--

2.10

4.10

groundwater elevation in and outside the gallery.

17 Sep

<DL

3.83

7.08

23 Sep

--

7.30

7.85

Groundwater chemistry monitoring included

01 Oct

<DL

2.10

6.78

concentrations of Cl, NO3, PO4, SO4, Ca, Mg, Na,

04 Oct

--

K, Fe, Br, F, Pb, O2, nitrate, TPH, and aromatic

07 Oct

--

0.80

6.50

hydrocarbons for samples extracted from the six

b. 1992

monitoring wells surrounding the gallery and

19 Jun

<DL

0.7

1.1

the pumping well. The numbers of hydrocarbon

26 Jun

--

degrading microorganisms and microbial miner-

01 Jul

--

1.7

1.8

alization potential for groundwater samples ex-

06 Jul

--

tracted from several of the infiltration gallery

09 Jul

0.2

<DL

0.6

<DL

8.6

6.9

monitoring wells were also measured during both

16 Jul

--

6.5

5.1

operating seasons. The locations of the wells and

17 Jul

--

points used to monitor the infiltration gallery

23 Jul

<DL

2.8

operation are shown in Figure 6.

30 Jul

--

0.7

Frequent monitoring of benzene, BTEX, and

06 Aug

<DL

2.8

1.2

nitrate in the groundwater at monitoring wells

06 Aug

--

DEC1 and DEC2 was required for compliance

13 Aug

--

5.38

5.59

with the State Waste Treatment/Disposal Permit

18 Aug

--

necessary to operate the infiltration gallery. Table

20 Aug

<DL

6.6

3 shows the results of this monitoring for 1991

24 Aug

--

and 1992. If nitrate concentrations exceeded 5

28 Aug

--

4.2

3.5

ppm (mg/kg), the permit required action be taken

03 Sep

<DL

0.5

0.8

to reduce the concentration; if concentrations

11 Sep

--

<DL

0.6

exceeded 10 ppm (mg/kg) (federal MCL), the

16 Sep

<DL

0.55

0.8

permit required that the system be shut off. The

01 Oct

--

<DL

concentration of nitrate was found to rise quickly

* Below detection limits.

at the monitoring wells, reaching action levels

within 23 weeks of startup. The measured con-

Operation

centrations never exceeded 10 ppm (mg/kg). Ben-

The infiltration gallery operation consists of

zene and BTEX were detected only once in these

pumping groundwater at a rate of approximately

wells after initial startup in 1991. These mea-

40 gal/min (151 L/min) from the pumping well

sured levels of BTEX were substantially below

and infiltrating the water through petroleum-

the federal MCL.

contaminated soils surrounding the gallery. A

Before the system began operating in 1991,

fertilizer solution is prepared in the mix tank,

benzene was detected at concentrations of less

such that when it is injected into the stream of

than 1 ppb (g/kg) in the monitoring wells

water to be infiltrated, the final concentration of

sampled. After the system had operated for 10

nitrogen is 40 ppm (mg/kg). The N:P:K ratio

days, benzene and BTEX were no longer detected

used in the nutrient solution is 10:1:1.

in the monitoring wells. After 3 days of opera-

On 23 August 1991, the system was activated

tion, benzene levels in the pumping well were

and operated continuously until 7 October. Phos-

measured at 12 ppb (g/kg). This well was not

phate fertilizer was not added during 1991. The

sampled before startup. The levels of benzene in

system was also operated from 23 June through 1

the pumping well remained near 10 ppb (g/kg)

October 1992. During this time, the concentra-

throughout the 1991 operating season. Benzene

tion of ammonium nitrate input was reduced

13