ELSEVIER 0 9 6 0 - 8 5 2 4 ( 9 5 ) 0 0 0 5 7 - 7

Bioresource Technology 53 (1995) 105-111 © 1995 Elsevier Science Limited

Printed in Great Britain. All rights reserved 0960-8524/95/$9.50

IMPACT OF DEAD BIRD DISPOSAL PITS ON GROUND- WATER QUALITY ON THE DELMARVA PENINSULA

W. F. Ritter & A. E. M. Chirnside

Agricultural Engineering Department, University of Delaware, Newark, DE 19717, USA

(Received 6 September 1994; revised version received 4 April 1995: accepted 12 April 1995)

Abstract Ground-water quality around six existing dead bird dis- posal pits was monitored for ammonia, nitrates, chlorides, fecal coliforms and fecal streptococci. The disposal pits were located on Evesboro loamy sand, Sassafras sandy loam, Fallsington sandy loam and Klej loamy sand soils.

Elevated ammonia concentrations were detected in the ground-water at three of the six existing disposal pits. Ammonia concentrations as high as 366 mg/l N were measured. Fecal coliform and fecal streptococcus concentrations were low. Over 70% of the sample did not contain fecal coliforms or fecal streptococci. Chlo- ride concentrations were above normal levels in only one monitoring well at one of the disposal pits.

Disposal pits that handle the normal mortality of a broiler grower should not cause any more ground-water contamination than an individual septic tank and soil absorption bed. If disposal pits are to be used in the future on the Delmarva Peninsula, they should be regu- lated.

Key words: Ground-water, poultry, dead birds, nitro- gen, bacteria.

INTRODUCTION

In 1993, over 573 million broilers were raised on the Delmarva Peninsula with a value of 1.26 billion dol- lars. Delaware has over 1200 poultry growers. Poultry production and the associated crops pro- duced for feed for the poultry industry account for approximately 70% of Delaware's agricultural income (DDA, 1993). Mortality rates for broilers average 4-5%. Disposal of dead birds has been a major problem for the industry. Most of the dead birds are disposed of on the grower's farm, because of fear of spreading diseases if the dead birds are transported off the property. Some of the methods that are being used today or have been used in the past to dispose of dead birds are direct animal feed- ing, without rendering; surface and subsurface land disposal; incineration and composting. Incineration is an,expensive method for disposing of dead birds

because of the energy costs. Subsurface disposal has been the most common method of disposing of dead birds in the past. Today, composting is being widely accepted as a dead bird disposal method. A recent industry survey found approximately 40% of the growers are using composting to dispose of dead birds on the Delmarva Peninsula (DPI, 1994). Most of the research on the composting technique was conducted at the University of Maryland (Murphy, 1988). Other methods that have been investigated for dead bird disposal are aerobic digestion, acid preservation, extrusion and lactic fermentation (Mal- one, 1988; Vandepopuliere, 1990; Murphy & Silbert, 1990).

In many poultry-growing areas, many burial pits that are used have open bottoms. On the Delmarva Peninsula, the most common type of burial pits are old, metal, feed bins with the bottom cut out of them. Because of the high water table on the Del- marva Peninsula, the bottoms of many of the disposal pits are located in the ground-water during part or most of the year. There is a concern that these disposal pits may be contaminating the ground-water or that the residue remaining after years of use may contaminate the ground-water in the future. A project was initiated at the University of Delaware to evaluate the impact of existing dead bird disposal pits on ground-water quality.

105

METHODS

Disposal pit monitoring A total of six disposal pits were monitored. One of the pits was on Farm R (pit A) located near Lewes, while a second pit was located on Farm W (pit B) near Greenwood. Four pits on the University of Delaware Research and Education Center near Georgetown were also being monitored. Pit A on Farm R was located in a Sassafras sandy loam soil (fine-loamy, silicaceous, mesic, typic hapludults), while pit B was located in a Fallsington sandy loam soil (fine-loamy, silicaceous, mesic, typic ochra- quults). Two pits (E and F) at the University of Delaware were located on Evesboro loamy sand soil

106 W.. E Ritter, A. E. M. Chirnside

Table 1. Hydrologic properties of soils of disposal pit locations

Soil Depth to seasonal Permeability a Available moisture high-water table (cm/h) capacity

(cm) (cm/cm)

Sassafras > 152 1.6-5-1 Fallsington 0-30 1.6-5.1 Evesbro > 152 1.6-5-1 Klej 60 1.6-5.1

0"12-0.24 0"10-0.18 0-06-0-10 0-06-0.10

a Permeability of most restrictive horizon.

(mesic, coated, typic quartzipssaments) and two pits were located in a Klej loamy sand soil (mesic, coated, aquic quartzipssaments). Some of the hydro- logic properties of the soils are presented in Table 1 (USDA, 1974). Pit C had the bottom lined with bentonite. Pits C and D were not loaded as heavily as pits E and F.

Two or three monitoring wells were placed around each pit at a distance of 3 and 6 m from the pit. Monitoring wells were constructed from 32.5 mm PVC pipe. The wells were installed by the hol- low-stem auger drilling method by the Delaware Geological Survey. The bottom 0.75 m of the wells were screened with 2.5 mm slot size PVC screen. The annulus around all the wells was sealed with bentonite. All wells were installed to a depth of 4.5 m.

All monitoring wells were sampled every 4-8 weeks and analyzed for ammonia, nitrates, chlorides, fecal coliforms and fecal streptococci. The wells were pumped dry and allowed to recharge before a sample was taken with a peristaltic pump. Water- table depths were also measured at each sampling. Ammonia was analyzed by steam distillation and nesslerization (APHA, 1985) and nitrates were ana- lyzed by the Devarda's Alloy method (APHA, 1985). Chlorides were analyzed by the titrimetric method (EPA, 1979). Fecal coliforms and fecal streptococci were analyzed by the membrane filter method (APHA, 1985). A quality assurance plan was devel- oped and was used for all laboratory analysis and field sampling.

Geology and hydrology The disposal pits are located in the Atlantic Coastal Plain and the sediments are of the Pleistocene age. The principal aquifer in southern Delaware, where the disposal pits are located, is the water-table aqui- fer. The estimated average transmissivity of the aquifer is 465 m2/day. The average annual recharge is 360 mm (Johnston, 1973).

At the Research and Education Center, all mon- itoring well logs indicated the subsurface profile consisted of medium to coarse sand with traces of gravel to a depth of 4.5 m. At Farm R the strata consisted of medium to coarse sand with traces of gravel from 0.2 to 1.8 m, orange and brown sandy clay from 1.8 to 3.5 m and coarse sand and gravel

from 3"5 to 4.5 m. The strata at Farm W consisted of fine to medium sandy clay from 0.2 to 1.1 m, fine sandy clay from 1.1 to 2.0 m and fine to medium sand with traces of gravel from 2.0 to 4.5 m.

During the study, water-table depths varied from 1.2 to 2.1 m on the Fallsington sandy loam soil and from 2.1 to 4.3 m on the Sassafras sandy loam soil. At the Research and Education Center the water- table depths varied from 2.1 to 4.5 m.

RESULTS AND DISCUSSION

Precipitation Ground-water was monitored from May, 1987, to March, 1990. In 1987 precipitation was below nor- mal from May to December for all months except November. The annual precipitation in 1987 was 99.1 cm, while normal precipitation is 109 cm. Pre- cipitation in 1988 was below normal with an annual rainfall of 94.1 cm. The months of June and Decem- ber were extremely dry, while precipitation was normal for the rest of the months. The year 1989 was extremely wet, with precipitation totaling 160.4 cm. Most months had above normal precipitation. Precipitation for the first three months of 1990 was near normal.

Ground-water quality Ground-water monitoring on Farm R was conducted from May, 1987, to March, 1990, and on Farm W from November, 1987, to March, 1990. At the Research and Education Center, the four disposal pits were monitored from July, 1987, to March, 1990. Ground-water quality data are summarized in Tables 2-4.

Ammonia concentrations were high in a number of monitoring wells around disposal pits B, D and E. Both pits D and E were located in loamy sand soils with cation-exchange capacities of 3.0 meq/100 g or less. Pit B was located in a Fallsington sandy loam soil with a typical cation-exchange capacity of 5 meq/ 100 g (USDA, 1974). Ammonia concentrations in well No. 1 of pit B ranged from 14.6 to 60-1 mg/l N with an average concentration of 32.5 mg/l N. Ammonia concentrations in wells #2 and #3 ranged from <0.05 to 1-51 mg/1 N. As indicated by Fig. 1, there is very little slope to the ground-water. The monitoring well locations in relationship to disposal

Impact of dead bird disposal pits on ground-water quality

Table 2. Summary of ground-water quality data for disposal pits A and B

107

Parameter Pit m a Pit B b

1 2 3 1 2 3

NH3-N No. of samples 29 29 29 25 25 25 Avg. conc. (mg/1 N) 0-15 0-09 0-21 32.5 0.12 0.17 Max. conc. (mg/1 N) 1.03 0.66 2.09 60.1 0.71 1-51 Min. conc. (mg/l N) < 0.05 < 0.05 < 0.05 14.6 < 0.05 < 0.05 Std. dev. (mg/1 N) 0.29 0.18 0.45 17.1 0.22 0.32 NO3-N No. of samples 29 29 25 25 25 25 Avg. conc. (mg/1 N) 18.3 16.6 14.0 0.46 3.88 4.69 Max. conc. (mg/l N) 48.2 36.2 25.0 1.37 7.01 8.71 Min. conc. (mg/1 N) 9.36 7.10 6.89 <0.05 <0.05 0.20 Std. dev. (mg/l N) 7.41 5.87 3.63 0.42 2.21 2.59 CI No. of samples 29 29 29 25 25 25 Avg. conc. (mg/1) 9.10 17.7 18.8 104.3 7.0 6.8 Max. conc. (mg/l) 18.6 48.4 27.1 208.8 9.6 10.3 Min. conc. (mg/l) 4.5 6.7 6.4 12.2 4.7 4.9 Std. dev. (mg/1) 2-90 12.0 5.6 61.5 1.4 1.0 Fecal coliforms No. of samples 28 29 26 25 25 25 Avg. conc. (#/100 ml) 28 5 8 1 5 6 Max. conc. (#/100 ml) 500 100 169 17 100 100 Min. conc. (#/100 ml) 0 0 0 0 0 0 Std. dev. (#/100 ml) 98 19 33 4 20 20 Fecal streptococci No. of samples 26 27 24 25 25 25 Avg. conc. (#/100 ml) 5 10 8 1 2 4 Max. conc. (#/100 ml) 56 209 92 18 54 46 Min. conc. (#/100 ml) 0 0 0 0 0 0 Std. dev. (#/100 ml) 18 40 23 4 11 11

a Sassafras - - well-drained soil. b Fallsington - - poorly-drained soil.

B were similar for the other disposal pits. In some cases, only two wells were installed because of the location of the disposal pit. There was only 20 mm between the elevations of the ground-water in wells #1, #2 and #3, so pollutants could move in all directions from the pit if the aquifer material was homogeneous. The well logs indicated that there was gray, fine to medium, sand with traces of gravel from the borings from 3.0-4.5 m of well #1, while wells #2 and #3 had tan, fine to medium, sand with less gravel.

For pit D, well #1 had ammonia concentrations that ranged from <0-05 to 73"9 mg/1, with an aver- age concentration of 10.8 mg/1 N. Pit C, which was loaded at approximately the same rate as pit D, had low ammonia concentrations in the ground-water. The bentonite lining appears to be restricting the movement of ammonia out of the pit. It is estimated that both pits C and D were loaded at < 1.0 kg dead birds per week.

Pit E had the highest ammonia concentrations in the ground-water around it. Well #2 had an average ammonia concentration of 120.0 mg/1 N. There was a large fluctuation in the ammonia concentration of

all three wells, as indicated by Fig. 2. Ammonia concentrations ranged from 9.03 to 168 mg/1 N in well #3 and from 29.5 to 366 mg/1 N in well #2. Ammonia concentrations were above 1.0 mg/l N in well #1 four times and ranged from <0.05 to 65-0 mg/1. The general direction of ground-water flow is from well #1 towards wells #2 and #3 (Fig. 3). The slope of the ground-water is approximately 0.12 m per 100 m. The highest ammonia concentrations occurred during the summer and fall of 1988 and the winter of 1990. The ammonia may have been diluted to some extent during 1989 when rainfall was excessive. It is difficult to estimate what was the loading rate of pit E, but given the normal broiler mortality of 5%, the loading rate was probably in the range of 15-25 kg of dead birds per week.

Pit F had very low ammonia concentrations in wells #1 and #2, but higher concentrations in well #3. Well #3 was only sampled in the first year, before it was broken off by a mower and destroyed. Ammonia concentrations in well #3 ranged from 7.81 to 21.3 mg/1 N. Wells #1 and #2 were located up the gradient from the disposal pit in the direction of the ground-water flow, which may explain why the

108 W. E Ritter, A. E. M. Chirnside

Table 3. Summary of ground-water quality data for disposal pits C and D

Parameter Pit C a Pit D

Well no. Well no. 1 2 1 2

NH3-N No. of samples 26 26 26 26 Avg. conc. (mg/1 N) 0.40 0-09 18.8 0.63 Max. conc. (mg/1 N) 2.84 0-55 73.9 10.8 Min. conc. (mg/l N) < 0.05 < 0-05 < 0.05 < 0.05 Std. dev. (mg/1 N) 0.92 0-14 23.6 2.09 NO3-N No. of samples 26 26 26 26 Avg. conc. (mg/l N) 5.96 5.78 3.19 6.39 Max. conc. (mg/1 N) 14.0 11.4 15.9 17-0 Min. conc. (mg/l N) 1.41 0.59 <0.05 <0.19 Std. dev. (mg/l N) 3-83 3-41 3.53 3.60 CI No. of samples 26 26 26 26 Avg. conc. (mg/1 N) 4.5 4-8 8.3 6.3 Max. conc. (mg/1) 9.7 10.0 14.5 12.4 Min. conc. (mg/1) 2.6 1.6 4.5 3.3 Std. dev. (mg/1) 2.90 12.0 5.6 61.5 Fecal coliforms No. of samples 26 26 26 26 Avg. conc. (#/100 ml) 97 3 2 1 Max. conc. (#/100 ml) 2500 35 15 7 Min. conc. (#/100 ml) 0 0 0 0 Std. dev. (#/100 ml) 490 8 4 2 Fecal streptococci No. of samples 23 23 23 23 Avg. conc. (#/100 ml) < 1 < 1 2 < 1 Max. conc. (#/100 ml) 1 3 40 2 Min. conc. (#/100 ml) 0 0 0 0 Std. dev. (#/100 ml) < 1 1 8 < 1

a Klej - - moderately well-drained soil.

ammonia concentrations were low in these wells. The direction of ground-water flow was from wells #1 and # 2 towards well #3. Well #3 was located near a poultry house, which may also have had an influence on the ammonia concentrations in the ground-water. Recent research indicates that ammo- nia and nitrate concentrations under older poultry houses are extremely high (Ritter et al., 1994).

Ammonia concentrations around pit A were low in all of the monitoring wells. The well logs indi- cated that the profile from 1.8 to 4.0 m consisted of orange and brown silt, sand and clay. The cation- exchange capacity of the subsurface was probably greater than the other disposal pits, where the well logs indicated the profile below 1-0 m consisted of fine to medium sand. With a higher cation-exchange capacity, ammonia would not move as readily in the ground-water. The loading rate for pit A was prob- ably below 10 kg of dead birds per week and would be in the same range as the loading rate for pit B. The University of Delaware Poultry Diagnostic Lab- oratory used pit F, so it is difficult to determine the loading rate of that pit.

All pits except A and C had average ammonia concentrations in some of the monitoring wells that were higher than ammonia concentrations found in the ground-water under cultivated fields (Ritter et a/., 1993). Ammonia concentrations in the ground- water under irrigated corn are generally below 1-0 mg/1 N.

All monitoring wells around pit A had nitrate con- centrations above 10 mg/1. Other monitoring wells on Farm R, which were part of a stockpiled manure project, also had nitrate concentrations above 10 mg/ 1, along with the Farm's water-supply well. High nitrate concentrations in the ground-water in poul- try-producing areas of Sussex County, Delaware, are common (Ritter & Chirnside, 1982). The high nitrate concentrations are probably caused by exces- sive applications of poultry manure to cropland or stockpiling of poultry manure on bare soil without the manure being covered.

Nitrate concentrations were lower in the ground- water around pit B than some of the other pits. Pit B was located in a Fallsington soil which is poorly drained. All of the other pits were located in soils

Impact of dead bird disposal pits on ground-water quality

Table 4. Summary of ground-water quality data for disposal pits E and F

109

Parameter Pit E" Pit F

Well no. Well no. 1 2 3 1 2 3

NH3-N No. of samples 26 26 26 24 16 9 Avg. conc. (mg/l N) 4.36 120.0 65.9 0.15 0-17 7-81 Max. conc. (mg/l N) 65.0 365.7 167.5 0.44 0.55 21.3 Min. conc. (mg/1 N) 0-05 29.5 9.03 0.05 0.05 1.35 Std. dev. (mg/l N) 13-6 98.2 59-0 0.14 0.17 5.79

N O 3 - N No. of samples 26 26 26 25 16 8 Avg. conc. (mg/1 N) 6.09 2-84 1.85 9-29 2.34 38.3 Max. conc. (mg/l N) 9.69 38.1 6-23 30.4 110.5 77.6 Min. conc. (mg/l N) 0.81 < 0.05 < 0-05 0.26 0.08 14.1 Std. dev. (mg/l N) 2-14 8.39 1.61 7.11 3.37 26.1

C1 No. of samples 25 25 26 25 17 9 Avg. conc. (mg/1) 9.5 12.7 10.9 9-5 6-8 15-8 Max. conc. (mg/1) 20.1 26.1 26.3 20-1 21.3 28.4 Min. conc. (mg/1) 4-1 1.0 1.2 4.1 2-1 4.9 Std. dev. (mg/1) 4-8 1.0 1.9 4.8 4.9 1-0

Fecal coliforms No. of samples 26 26 26 24 16 7 Avg. conc. (#/100 ml) 13 21 78 1 1 0 Max. conc. (#/100 ml) 150 306 1740 26 5 0 Min. conc. (#/100 ml) 0 0 0 0 0 0 Std. dev. (#/100 ml) 32 61 340 5 1 0

Fecal streptococci No. of samples 23 23 23 24 17 7 Avg. conc. (#/100 ml) 8 2 1 0 8 1 Max. conc. (#/100 ml) 121 2 1 0 9 2 Min. conc. (#/100 ml) 0 0 0 0 0 0 Std. dev. (#/100 ml) 26 3 1 0 24 1

"Evesboro - - excessively-drained soil.

#3 #2 -¢- ÷

12.31m 12.31m

Fig. 1.

GROUND-WATER FLOW

MONITORING WELL

#i SCALE

" ~ 0 1 2 3

12.33m METERS

Water-table elevations around pit B on 20 June 1989.

that were moderate ly well drained (Klej), well drained (Sassafras) or excessively drained (Eves- boro). For pit F, well # 3 had excessively high nitrate concentrat ions before the well was destroyed, as pre- viously mentioned. Nitrate concentrat ions ranged from 74"1 to 77"8 mg/1 N. The high nitrates may have been caused by the disposal pit, since the well was

4°° t Z -- 3 0 0

' A ' ', : / \ : ; ', ',...

i: ,, ,i,

.... i i~ '., :! , , / \ ,' 1 i ' / ,¢ ~,,

i,

J , . ¢ ,

, j ............. ;,,,/ ,," \. ,,/ ',/ ........ ,, ~: ,,:

Jul-87 Jan-88 Jul-88 Jan-89 Jul-89 Jan-90 Sampling Date

E

,~ 200

.-- g E E <

100

Fig. 2. Ammonia

I -- Well #1 -- Well #2 ... W e l l ~

concentrations in monitoring wells around pit E.

located approximately 6 m from the pit in the direc- tion of the ground-water flow. Well #1 also had nitrate concentrat ions above 10 mg/l during the falls of 1987 and 1988 and the winter of 1989. Well # 2

110 W. E Ritter, A. E. M. Chirnside

~3

11.76m

Fig. 3.

#2

+ 11,77rn

GROUND-WATER FLOW

~- MONITORING WELL

#1 SCALE

" ~ 0 1 2 3

11.7gm METERS

Water-table elevations around pit E on 28 June 1989.

20

15

E

10

5

0 Jul-87 Jan-88 Jul-88 Jan-89 Jul-89 Jan-90

Sampling Date

around pit F had nitrate concentrations below 10 mg/1 N, except for one sample. Both wells #1 and #2 were up-gradient from the disposal pit in the direction of ground-water flow at a distance of 3 m from the pit. The water-supply well for the office of the Research and Education Center is also located in the general vicinity of wells #1 and #2 and has had nitrate concentrations in the 10-15 mg/l N range during a number of samplings. The well is approximately 20 m deep. There is a possibility that the higher nitrate concentrations in well #1 could be caused by other sources besides the disposal pit, such as nitrogen fertilizer applied to the office lawn or nearby fields. The average nitrate concentrations in the ground-water around the other disposal pits (C, D and E) were below 10 mg/l N. Most of the monitoring wells around pits C, D and E had nitrate concentrations above 10 mg/l N at least once. There was some seasonal variation to nitrate concentra- tions, as indicated by Fig. 4. In general, nitrate concentrations were lower during 1989, which was extremely wet, than 1987 or 1988. The highest nitrate concentrations generally occurred during the late fall or early winter. Some of the ammonia in the upper levels of the aquifer may have nitrified during the summer as the water table levels decreased and the zone became more aerobic. The nitrates could have been leached to the ground-water. Probably, at depths of 4.5 m, very little of the ammonia coming from the disposal pits would be nitrified, because no aerobic zone would exist for nitrification to occur.

Chloride concentrations were low in most of the monitoring wells. It appears that well #1 around pit B is the only monitoring well with above normal chloride concentrations. The chloride concentrations in well #1 ranged from 12"2 to 209 mg/l. In all other monitoring wells, chloride concentrations were below 30 mg/l. Chloride concentrations under culti- vated fields in Delaware are generally under 30 mg/l (Ritter et al., 1993).

Fecal coliform and fecal streptococcus concentra- tions were low in all of the monitoring wells. They were detected more frequently in the ground-water around pits A and E than the other pits. Fecal coli- form were detected in 10 out of 26 samples in wells

Fig. 4. I - Pit E - Well #1 --- Pit D - Well #2 I

Nitrate concentrations in ground-water around pits D and E.

#2 and #3 of pit E and in 8 out of 26 samples in well #1 of pit E. For some sampling dates the fecal coliform were only detected in one well. Fecal coli- form were detected a total of 19 times in one well or more out of a total of 26 sampling dates. Sixty per- cent of the samples did not contain fecal coliforms from the ground-water around pit E. Fecal coliforms were detected more frequently and in higher con- centrations than fecal streptococci.

Fecal coliforms were detected less frequently in the ground-water around pit A than pit E. Twenty- seven percent of the samples had fecal coliforms, with wells #1 and #2 having fecal coliforms detec- ted the most frequently. Fecal streptococci were detected in 25% of the ground-water samples around pit A. Over 80% of the ground-water sam- ples from the other pits did not contain fecal coliforms or fecal streptococci. Ritter et al. (1990) found that in monitoring ground-water around eight alternative on-site wastewater systems over a 2 year period, over 80% of the samples did not contain fecal coliforms or fecal streptococci. Fecal coliform concentrations for the on-site wastewater study for most samples were generally < 20/100 ml, which was in the same range as fecal coliform concentrations detected around the disposal pits. Bacteria generally do not move very far in soils, so widespread bacteria contamination around disposal pits should not be expected. Bell et al. (1978) found that all fecal coli- forms were removed in the top 69 cm of a sandy loam soil under a spray irrigation site. Reed (1979) reported that all fecal coliforms were removed in 152 cm in silt loam and loamy sand soils in a 5 year study in New Hampshire on applying primary- and secondary-treatment municipal wastewater to two soil types.

Only three of the existing disposal pits have had an impact on ground-water quality. Nitrogen is more of a problem than bacteria contamination. Ritter (1990) also found this was true for septic tanks and soil absorption systems. In general, nitrate concen-

Impact of dead bird disposal pits on ground-water quality 111

trations were higher in the ground-water around the eight alternative on-site wastewater systems moni- tored by Ritter (1990) than the disposal pits but the ammonia concentrations were much higher around the disposal pits. Based upon the research, it appears many existing disposal pits will probably cause no more ground-water contamination than an individual septic tank and soil absorption bed. Seri- ous ground-water contamination may occur if a grower has a large number of birds killed and has to bury them. Ammonia contamination of ground- water is the greatest concern around disposal pits. Based upon nitrate, chloride and fecal coliform con- centrations, most of the samples collected around the disposal pits had concentrations below the EPA drinking-water standards. Around several of the dis- posal pits, ammonia concentrations were much higher than the EPA drinking-water standard of 10 mg/1 for nitrate. There is no drinking-water standard for ammonia, although it is undesirable to have ammonia present in drinking-water supplies at any concentration.

There is the question as to what impact aban- doned disposal pits are having on ground-water quality. These pits should probably be pumped-out and filled with soil to minimize the impact on ground-water quality. If subsurface disposal for dead birds is to be used in the future on the Delmarva Peninsula, it should probably be regulated. Regula- tions should be similar to on-site wastewater regulations in Delaware. A soil survey would be required by a certified soil scientist to determine the suitability of the site for subsurface disposal. After a soil survey is conducted, the applicant would submit an application to the Delaware Department of Natu- ral Resources and Environmental Control for a permit. Only certain types of disposal pits, such as concrete tanks, should be allowed. With an approved permit the site would meet certain condi- tions, as to soil type and water-table depth for subsurface disposal pits.

REFERENCES

15th edn. American Public Health Association, Wash- ington, DC.

Bell, R. G. & Bole, J. B. (1978). Elimination of fecal coliform bacteria from soil irrigated with municipal sew- age lagoon effluent. J. Environ. Qual., 71, 193-6.

Delaware Department of Agriculture (1993). Delaware Agricultural Statistics, 1992. Delaware Department of Agriculture, Dover, DE.

Delmarva Poultry Industry (1994). DPI dead-bird com- poster survey, May, 1994. Delmarva Poultry Industry, Georgetown, DE. Unpublished data.

Johnston, R. H. (1973). Hydrology of the Columbia (Pleistocene) deposits of Delaware. Delaware Geolog- ical Survey, Newark. DE Bull., 14.

Malone, G. (1988). Dead bird and hatchery waste disposal and utilization. Proc. National Poultry Waste Management Symp., 18-19 April 1988, Columbus, Ohio, pp. 73-5.

Murphy, D. (1988). Preliminary investigations of compost- ing as a method of dead bird disposal. Proc. National Poultry Waste Management Syrup., 18-19 April 1988, Columbus, Ohio, pp. 65-72.

Murphy, D. W. & Silbert, S. A. (1990). Carcass preserva- tion systems - - lactic fermentation. Proc. 1990 National Poultry Waste Management Syrup., 3-4 October 1990, Raleigh, North Carolina, pp. 56-63.

Reed, S. C. (1979). Health Aspects of Land Treatment. EPA, Washington, DC, 1979-657-093/7086.

Ritter, W. F. & Chirnside, A. E. M. (1982). Ground-water quality in selected areas of Kent and Sussex counties, Delaware. Technical Report. Delaware Department of Natural Resources and Environmental Control, Dover, DE.

Ritter, W. F. (1990). Impact of alternative on-site waste- water systems on ground-water quality in Delaware. Technical Report. Delaware Department of Natural Resources and Environmental Control, Dover, DE.

Ritter, W. F., Scarborough, R. W. & Chirnside, A. E. M. (1993). Nitrate leaching under irrigated corn. J. Irriga- tion Drainage Engng, 119, 544-53.

Ritter, W. F., Chirnside, A. E. M. & Scarborough, R. W. (1994). Nitrogen movement in poultry houses and under stockpiled manure. Paper No. 94-4057. American Soci- ety of Agricultural Engineers, St Joseph, MI.

U.S. Department of Agriculture (1974). Soil survey of Sus- sex County, Delaware. SCS, Washington, DC.

U.S. Environmental Protection Agency (1979). Methods for Chemical Analysis of Water and Wastes. Environmen- tal Monitoring and Support Laboratory, Cincinnati, OH, EPA-600/4-79-020.

Vandepopuliere, J. M. (1990). Carcass preservation sys- tems - - extrusion. Proc. 1990 National Poultry Waste Management Syrup., 3-4 October 1994, Raleigh, North Carolina, pp. 64-8.

American Public Health Association (1985). Standard Methods for the Examination of Water and Wastewater,