TECHNICAL BULLETIN NO. 675 MARCH 1939

UNITED STATES DEPARTMENT OF AGRICULTURE WASHINGTON, D. C.

SEWAGE IRRIGATION AS PRACTICED IN THE WESTERN STATES '

By WELLS A. HUTCHINS, Irrigation economist^ Division of Irrigation, Bureau of Agricultural Engineering

CONTENTS

Page Page Introduction Safeguards and regulations of public-health Doflnitions of terms _ authorities—continued. C haraoter of the problem State poUcies concerning sewage irrigation - 28 Sewage as a source of irrigation water supply_. _ Sanitary and acsthciic basis of high stand- Differentiation between uses of sewaiîc be- ards - 30 töre and after discharge into stream Possibility of polluting ground waters by channels sewage irrigation 34 Extent of current uses .__ __. Sanitary considerations in the use of Reasons for adopting or discontinuing sludge - 37 sewage irrigation Character of public regulation 37 Potential uses Salts in sewage effluents 39 Use of water Boron 40 Supply and demand-- Effluents in southern California 40 Irrigated acreages Possible effect of chlorination upon chemi- Present uses by individuals primarily sup- cal quality of effluent for irrigation. 41 plemental Sewage water rights 43 Methods of distributing and applying Economic feasibility of sewage irrigation 44 water Effect and value of past and present prac- Irrigable lands tices -- _ *45 Character and use of lands Economic aspects of extending present Ownership of lands., .- practices 4C IVlunicipal sewage farms Ability of farm lands to pay for sewage 49 Crops Returns from municipal sewage farms 52 Experimental data Use and sale of sludge 53 Crops irrigated with sewage in western Summary 64 areas Literature ci ted 56 Safeguards and regulations of public-health Appendix 06 authorities - List of areas included in siudy in which W hat the public welfare requires _ sewage was being used for crop irriga- Character of sewage used in current irriga- tionin 1934 or 1937 or both 60 tion practices - - -

INTRODUCTION Many western communities, in the face of limited supplies of irriga- tion water, have resorted to the use of sewage as a supplemental sup- ply. Because many cities in the West are surrounded by farm lands inadequately supplied with water, it is to be expected that the trend toward tliis practice will increase. There is small probability that this will enlarge irrigated areas, since in most of the localities now using sewage for this purpose it is used on farms that have too meager supplies of water and the need for better supplies is evident in most

1 Sul>mitted for publication April 4, 1938. n;in72°—39 1 2 TECHNICAL BUI.LKTIN 675, U. S. DEPT. OF AGRICULTURE places where usable supplies would be available. Eepeated droughts in recent years have emphasized the need and, as a result, there has been much careful canvassing of potential sources of supplemental water supply. Sewage irrigation is not new, not even in this country, but it pre- sents problems which differ in important respects from those involved in the use of water from streams and from ground-water sources. There are decided conflicts in thought as to some of these problems. Much has been written on various phases of the general subject, but comprehensive discussions, based upon field investigations and ap- proached from the primary standpoint of agriculture, are lacking. The first purpose of sewage disposal, of course, is protection of the public health, but if after the health factors have been amply safe- guarded to the satisfaction of the State and local authorities the water can still be made available for supplemental irrigation use, it is natural in the West to look upon it as an economic asset. So far the economic aspects of this use have not been much explored either by the cities themselves or by other users of this water, although many cities irri- gate witli sewage or sell it or give it to Irrigators. The question of economic feasibility is discussed in a special section. The present inquiry was undertaken to gather information on what constitutes adequate safeguards, according to the standards of public- health officials, the actual safeguards now applied through State and local laws and regulations, and present practices as to use of sewage for supplemental irrigation of crops in the West for the use of respon- sible public officers, landowners, and users who wish to determine the safety and economic effects of using sewage as a supplemental supply of water for irrigation. To this end a survey was made in the Western States in 1934 and 1935 and largely rechecked in 1937. Studies were made of 125 locali- ties in 15 States; sewage irrigation of crops is practiced in 113 of these places,^ and was formerly practiced and discontinued or reduced to a fraction of an acre in the remaining 12. Several other areas were included in which there were prospects for sewage irrigation, or in which sewage was applied to uncropped land, or where sludge was used for fertilizer. Nearly all examinations included personal visits. In addition, literature in the field of sanitary engineering bearing directly upon the irrigation factors, was examined and the implica- tions were weighed carefully. As a result of this study, the present bulletin has been prepared to report (1) what is now being done in the utilization of sewage in agriculture, (2) what authorities in the public sanitation field recommend by way of precautions, and what State and local laws and regulations prescribe, and (3) the economic effects of the present practices and the probable effects of their exten- sion so far as it is safe.^

' These 113 locaUties are listed In the Appendix. 3 The field work was done by or under the direction of the author. The larger part of the Texas work was done by Harry G. Nlckle, assistant Irrigation engineer, and the New Mexico work by Harry P. Blaney, irrigation engineer. Karl Harris, associate agri- cultural engineer, assisted in Arizona. Informal cooperation was eflfected with the com- mittee on salvage of sewage, sanitary and irrigation divisions, American Society of Civil Engineers, and with the departments of sanitary engineering of the several Western states. SEWAGE IRRIGATION IN WESTERN STATES 3

DEFINITIONS OF TERMS Certain terms used frequently in this bulletin are defined as follows, the definitions being largely those adopted by the American Society of Civil Engineers and the American Public Health Association." Sewage.—The liquid wastes flowing in a sewer from residences, business build- ings, institutions, and industrial establishments, with such ground, surface, and storm water as may be admitted to or And its way into the sewers. Crude sewage or raw sewage.—Sewage that has received no treatment. Effluent or sewage effluent.—Sewage, partly or completely treated, flowing out of any sewage-treatment device. Disinfected sewage.—Oude sewage, or a sewage-plant effluent, that has been treated with a disinfecting agent, commonly chlorine or "bleach", resulting in the destruction of bacteria sufficiently to reduce materially the danger of in- fection. Stable effluent.—A treated sewage that contains enough oxygen to satisfy its oxygen demand. Stability.—The ability of any substance, such as sewage, effluent, or digested sludge, to resist putrefaction. (Antonym, putrescibility.) Relative stability.—The ratio, expressed in percentage, of available oxygen in waste waters, sewage, effluent, or diluted sewage to that required to provide complete biochemical oxidation of the organic matters contained therein. Sewage irrigation.—The application of untreated or treated sewage to land for irrigation and fertilization purposes in the raising of crops, as distinguished from sewage disposal on land. Sewage disposal on land.—Tlie application of sewage to uncropped land for the sole purpose of disposing of the sewage by absorption. Sewage farming.—The raising of crops where sewage is applied to the land for irrigation and fertilization purposes. Sewage farm.—A farm where sewage or sewage effluents are used in whole or in part for irrigation and fertilization purposes in the raising of crops. It should be noted, therefore, that the term "sewage" is used in this bulletin irrespective of the state of its treatment or disposal, and that "sewage irrigation" includes the use of both raw sewage and effluents. Where a differentiation between untreated and treated sewage is in- tended, the specific terms "raw sewage" and "effluent" are used. CHARACTER OF THE PROBLEM Sewage irrigation in the West is not to be confused with sewage disposal. The terms are not synonymous ; on the contrary, sewage ir- rigation is a corollary of sewage disposal. Several decades ago, it is true, irrigation was primarily a convenient and relatively inexpensive method of disposing of sewage, but times and standards have changed. Authorities consider that water not safe enough to discharge into stream channels is not safe for general irrigation use, where it may be applied promiscuously to crops and may become a health hazard. Therefore sewage for general irrigation use requires pretreatment, such as commonly given before returning it to streams, m which case

< While these definitions are largely those published in (2),° there are important excep- tions : First, the definition oí "sewage" published in (2) is more detailed than required ior the purpose of the present discussion. Likewise, the term "broad irrigation" given in (2) implies only incidental benefit to crops, the primary purpose being the disposal of sewage, thus differing in this primary purpose from "sewage farming." As the present discussion deals with the possibility of using sewage as a supplemental water supply for crops, and not with methods of sewage disposal, the term "broad irrigation" is omitted and "sewage irrigation" is used regardless of its primary or incidental relationship to sewage disposal. To this end, a different definition of sewage irrigation is given, as well as a definition of sewage disposal on land. ^ Italic figures in parentheses refer to Literature Cited, p. 56. 4 TECHNICAL BULLETIN 675, U. S. DEPT. OF AÜKICULTU11E

use is being made of sewage which the city to all intents and purposes has already disposed of. Sewage irrigation, then, is still in some places a part of the city's sewage-disposal problem, but these places are becoming fewer. Else- where it is more properly an agricultural problem^—sometimes that of the individual farmer who wants a water supply safe and suitable for use on his own farm, sometimes that of the city in using the sewage efficiently to produce crops for revenue—and the problem of utilizing sewage by farmers generally, either as a permanent or a supplemental water supply in times of shortage, is distinctly in the field of agricul- tural engineering. SEWAGE AS A SOURCE OF IRRIGATION WATER SUPPLY DIFFERENTIATION BETWEEN USES OF SEWAGE BEFORE AND AFTER DISCHARGE INTO STREAM CHANNELS At various places in the present discussion, a differentiation is made between utilization of sewage taken directly from outfall lines or treatment plants, and that diverted from stream channels into which it is discharged by the municipality producing the sewage. This is done for several reasons. In the first place, the point of diver- sion has a bearing upon the question of water rights, as indicated under the section entitled "Sewage Water Eights" (p. 43). Again, control by a city over practices of using sewage for irrigation is usually lost after the sew'age has gone into a public watercourse, and the character of public regulation is correspondingly altered. Like- wise, the character of sewage after its discharge into a flowing stream becomes altered to whatever extent it is thereby diluted and subse- quently purified by natural processes prior to diversion into irriga- tion ditches. Streams from which western communities derive their irrigation water supplies carry, in various cases, raw sewage or efflu- ents in varying stages of treatment or subsequent natural purification. Whether the subsequent use of such stream water for irrigation in a given case is or is not sewage irrigation may involve some very fine distinctions. Where waters are so heavily charged with sewage as to render crops dangerous for human consumi)tion, (juite obviously their use denotes sewage irriga- tion. * * * Dilute sewage and gross stream pollution are practically synonymous, and the fine demarcation that differentiates between some water works plants and some sewage plants is not readily distinguishable (SJf, p. 472). The present study includes 95 communities in which the only sewage used for irrigation is that taken directly from outfalls or treat- ment plants, 11 conmiunities in which no use is made of sewage until after its discharge into and diversion from a stream channel, and 7 communities in which some sewage is used directly from outfalls or treatment plants and the balance is discharged into watercourses from which diversions are made shortly for irrigation. EXTENT OF CURRENT USES

DIRBX3T DIVERSIONS I'BOM SEWEK AND EFFLUENT CONDUITS Sewage is being used for the irrigation of crops directly from out- fall lines or treatment plants in 102 western communities included in the present study. Of these 47 are in California, 32 in Texas, and from 1 to 4 each in Arizona, Colorado, Idaho, Kansas, Montana, SEWAGE IRRIGATION IN WESTERN STATES 5

New Mexico, Oregon, Utah, Washington, and Wyoming. State sani- tary officials report that sewage irrigation is practiced in some areas not included in the study, but it is believed that the canvass covered a large percentage of the total number of areas in the West. Sewage from large cities, generally speaking, is not used directly from outfalls or treatment plants for irrigation. Important excep- tions are Salt Lake City, Utah, and Helena, Mont., from each of which a substantial part of the sewage is customarily applied to crops before being discharged into a stream channel. Considering cities with popu- lations exceeding 10,000, the practice is being followed by about one- fourth of those in California, led by Pasadena (the eighth city in size), and by about one-fifth of those in Texas, led by San Antonio (the third largest city). The geographical location of large cities in this connection is discussed further under Potential uses (pp. 8 and 15). The recheck in 1937 indicated that while major or minor changes had taken place in various communities, including in some cases the installation of sewage-treatment plants, the general situation then was substantially the same as it had been several years earlier.

DrVEESlONS FROM STREAMS INTO WHIOH SEW AGB HAS BEEN DISCHAKGED Use of sewage for irrigation is also madt after its discharge into a public stream channel, as well as directly from the outfall lines, and therefore after the city's control over the flow has ceased. The present study includes 18 communities in Arizona, California, Colorado, Ne- braska, Nevada, New Mexico, Oregon, South Dakota, Texas, Utah, Washington, and Wyoming in which this is done. In seven of these communities, in addition to diversions from watercourses, some of the sewage supjily is taken directly from outfalls or treatment plants be- fore being discharged into the watercourse. The disposal of sewage in stream channels, rather than upon land, is practiced extensively in the West. In some cases the sewage is un- treated. The channels range in character from small washes which are dry most of the time, to rivers which flow continually. The relation of the sewage to the total stream flow depends, of course, upon the size and location of the contributing municipalities with reference to the natural run-off in the stream plus return flow from^ irrigation. As a consequence, in streams of intermittent natural flow, sewage may constitute most or all of the flow at certain places during part of the year, and may be only a small fraction of the total now at those same places during periods of high run-off. Therefore, in irrigated sections lying below cities and towns, irrigation ditches diverting from these stream channels may be, and in many ciises actually are, carrying sewage in varynig degrees of initial treatment and stream dilution, the presence of sewage being obvious in some cases, and the dilution and clarification being so great in other cases as to leave no apparent trace. A few examples will illustrate a condition existing in a rather large number of irrigated valleys. Yakima River, Washington, serving large areas of highly developed land, carries sewage from several cities, some of which is treated sewage. Boise and Snake Rivers, Idaho, likewise carry sewage, much of which is not pre- treated. A reservoir on Crow Creek, Wyoming, impounds untreated ß TECHNICAL BULLETIN 675, U. S. DEPT. OF AGRICULTURE sewage from Cheyenne in addition to natural flow (fig. 1). The sewage from Denver is an important part of the flow of the South Platte Kiver, which serves an extensive irrigated area. Sewage added 38 percent to the flow at Denver during the extremely de- ficient irrigation season of 1934; a treatment plant was installed in 1937. Tlie Ogden sewage, discharged untreated into Ogden Kiver, Utah, represented more than one-half of the water being pumped by two irrigation companies when visited in 1934. Effluent from the treatment plant at Rapid City, S. Dak., is an important part of the water supply for the lower irrigated area along Rapid Creek during periods of low stream flow.

FIGURE 1.—Reservoir used for storing water of Crow Creek and sewage from Cheyenne, Wyo.

REASONS FOR ADOPTING OK DISCONTINUING SEWAGE IRRIGATION One of the points of inquiry in each locality was why sewage irrigation was being or had been practiced, and why it had been discontinued if that was the case. Such information, it was felt, should throw light upon the likelihood of further use of sewage supplies for crop production. These factors may be summarized as follows :

Disposal of the sewage has been the ]irimary consideration on the part of the cities. Disposal upon land has appealed to many com- munities as the most convenient and economical method; in many places where this has been done the opportunity has been taken of offsetting a part of the cost of sewage disposal by revenue from crop production or from sale of the sewage to individuals for private use in crop production. In practically three-fourths of the cases in- cluded in the study, crop irrigation was subordinate to sewage dis- posal while in the other cases crop irrigation was a definite part of the l)lan of disposal. Typical of localities in which irrigation is or has been practiced but has no direct bearing on the matter of sewage disposal are Kingsburg, Calif., Meridian, Idaho, and Hastings, Nebr. Permis- sion to take the effluent has been a matter of accommodation to SEWAGE lURIGAÏION IN WESTERN STATES 7 farmers in the first two places; the water was filed on after entering a creek in the third. Munday, Tex., is typical of a large number of communities in which sewage irrigation has been a secondary consid- eration but of some economic importance, in that land disposal of the sewage effluent appeared to be the only practical method. A good example of cities to which use of effluent for irrigation has been an important fiscal consideration is Pomona, Calif. In 1926, after hav- ing operated a sewage farm for about 25 years, the city installed a treatment plant with the specific intention of selling the effluent for irrigation and has done so regularly. According to the city engineer— * * * we had an idea of conserving water and selling it for irrigation purposes before we decided npon the type of sewage treatment plant which we would build (!*, p. 39). Cities committed to sewage irrigation as the result of early con- tracts are represented by Greeley, Colo., and San Antonio, Tex.

DEVELOPMENT OF PLAN In certain communities raw sewage was formerly used for the irri- gation of cropland in the summer and bare land in the dorrnant season, because that seemed less objectionable than to discharge it into streams. Subsequently, in these localities, with the construction of treatment plants, irrigation came to be restricted to crop use during the growing season, the effluent being turned into streams in the win- ter. Objections to the discharge of raw, untreated sewage upon cropped land or into streams used for domestic, irrigation, or recrea- tional purposes have grown considerably within the past 25 or 30 years, and sanitary engineering has developed correspondingly. The result has been, in many instances, a substantial improvement in the quality of sewage effluents and an inclination to continue the use of improved effluents for irrigation purposes under the higher stand- ards then affecting such use. Pasadena's experience illustrates this. Raw sewage was disposed of on the city farm for many years, crop irrigation being adopted in order to secure revenue from the farm. Objectionable odors led to sewage treatment and to improvement of methods (31), eventually resulting in a plant which is the property of Pasadena, South Pasa- dena, and Alhambra, and which serves San Marino as well, with a total connected population of 130,000 in 1937. This plant is located in the midst of a growing residential section. Only a small part of the effluent is now used for irrigation.

DISCONTINUANCE

Irrigation of crops with sewage taken directly from outfalls or treat- ment plants had been practiced and subsequently discontinued in 11 of the localities visited, and had been reduced in another case to a small fraction of an acre. Discontinuance was due in several instances to un- suitability oí soil or water or insufficiency of available land. For ex- ample, the land in two cases proved too tight and poorly drained, and in another, too heavily impregnated with alkali. The high salt content of the water supply of one municipality is locally considered to have been the cause of crop failures and killing of orchard trees irrigated g TECHNICAL BULLETIN 675, U. S. DBPT. OF AGRICULTURE with the sewage effliTent. Two tracts proved to be too small, with no additional areas available. Other factors included changes in location of treatment plants, with resulting changes from direct use of the effluent at the old loca- tion to use after diversion from stream channels, or no demand for the water at the new location; substitution of dry farming for irri- gation farming; availability of substitute water supplies, owing to new development or dislike of the irrigator for continued use of sewage; unsatisfactory experience of the city with the lessee; un- jirofitableness ; and new State regulations forbidding the use of sew- age in irrigating certain crops. In these various instances the practice was followed thereafter of discharging the effluent from existing plants continuously into stream channels, or of building new plants for the purpose of pro- ducing effluents suitable for discharge into streams. Substitute ir- rigable areas were either not available, or were not sought. POTENTIAL USES The quantities of sewage produced in the Western States are small in comparison with the total quantities of water used in irrigation in the West. So far as existing uses are concerned, there are decided possibilities in improving the quality of effluents before attempting to use them. Otherwise the greatest potentialities are as supplemental water supplies, and as partial offsets against the increasing quanti- ties of water required by growing cities which sometimes decrease the water supplies available for agriculture." The sewage return from Denver over the 10-year period 1927-36 represents 70 percent of the city water consumption over the same period ^ ; the return at Los Angeles is in the order of two-thirds of domestic water used*; that at Pasadena in 1926, 1927, and 1930-31 ranged from 44 to 47.8 percent.* The question of utilizing Los Angeles sewage has been studied and discussed at various times in recent years, including operation of an experimental sewage-reclamation plant; but plans have not been carried further because of considerations of cost and other factors involved in the complicated water situation in southern California

USE OF WATER SUPPLY AND DEMAND The sewage output in many communities is measured regularly (fig. 2), in others only occasionally, and in still others not at all. The population contributing to sewage is only a rough indicator of

« Ise of water by municipalities is sometimes estimated as approximately the same as the irrigation nso on e<¡uivalent land areas (25, p. SI), ' Data furnished the writer by the chief engineer, Denver Board of Water Commis- sioners, show that the combined discharge of sanitary sewers, expressed as a percentage of total city water consumption, varied from 62 to 77 per annum and averaged 70 for the 10-year period 1027-:ití. * Data turnislied by the sanitary engineer, Los Angeles Department of Water and Power, show that domestic water used over the period 1926—'16, in average gallons per capita per day for each of the years, ranged from 112 to 135, the mean of the yearly aver- ages being 121 gallons. The average sewage flow for a 6-year period is 80 gallons per capita per day, the yearly averages varying from 78 to 83. Based upon these figures, the sewage return is approximately 66 percent of domestic water consumption. * Data provided by Pasadena Water Department. ^* For a number of years irrigation with untreated sewage "was practiced at Los Angeles (SS, p. 82), but the practice was discontinued in 1905 (11, p. U). SEWAGE IRRIGATION IN WESTERN STATES 9 the available sewage supply, owing to the marked variations in avail- able per capita quantities of municipal water supplies and in the degree to which these quantities are utilized without contributing to the sewage. For example, in hot climates water is evaporated in connection with cooling systems of certain types. Again, there may be little or no infiltration into sewers from irrigation of extensive parking areas and lawns, or in other cases there may be considerable. The high flow at Yakima, Wash., reaching a peak of 18,000,000 gallons per day for a population of 22,000, is attributed to infiltration re- sulting from a liigh ground-water level produced by irrigation. How- ever, where sewage is not measured but the approximate municipal use of water is known, the sewage discharge may be estimated with fair accuracy.

FiGiTRE 2.—Meiisureinent of sewage effluent prior to Irrigiition, Tiicson, Ariz. Sewage supplies are continually available even during general water shortages. While the flow of sewage is continuous, the quan- tity fluctuates from hour to hour and throughout the year, depending upon the use of municipal water supplies by the inhabitants. The discharge is normally greater in summer than in winter, which is advantageous for irrigation purposes. The irrigation season in the Soutliwest is long. It extends in some areas tliroughout most or all of the year, but considering the West as a whole, this is exceptional. In most sections the season lasts ordinarily 5 to 7 months. There are periods, therefore, in which sewage effluents in most areas cannot be applied to crops. Tempo- rary storage is being resorted to successfully in several cases, but no instances of long-time storage were observed in the course of the study. IRRIGATED ACREAGES Areas now irrigated with sewage taken directly from outfalls or treatment plants range from 1 or 2 acres to several thousand. In 113972°—39 2 10 TECHNICAL BULLETIN 675, U. S. DEPT. OF AGIUCULTUllE three-fourths of tlie cases the acreages are less than 100, although in some of these the possibilities are suDstantially greater. The greatest area of such direct use is that at San Antonio, Tex., where an esti- mated 2,600 to 2,700 acres are irrigated solely with effluent or with effluent supplemented by natural drainage into Lake Mitchell. At Anaconda, Mont., some 3,000 to 4,000 acres are reported as irrigated variously with sewage, slag water from the smelting works, and natural flow in Warmsprings Creek. Sewage dischai'ged into streams contributes, in several areas, to the water supplies of extensive irrigated areas, sometimes constituting a substantial portion of such supplies.

PRESENT USES BY INDIVIDUALS PRIMARILY SUPPLEMENTAL Sewage in 44 localities constitutes only a part of tlie usual water supply of individual farmers wlio use it (fig. 3), as against 22 locali-

FliiUiiE S.—Puiupiiifi l]l;iut discharging water Into ditcli carrying sewage effluent from Corcoran, Calif. ties in which it is their entire water supply for irrigation. This indicates that present uses of sewage, so far as individuals are con- cerned, are primarily supplemental. It is true that in some of the 44 comnninities in question there are certain individuals who have no other source of supply, but the general condition is as stated. Sewage in more than two-thirds of these areas in which it is a partial water supply is being used directly for irrigation from outfalls or treatment plants. Only a few mimicipal sewage farms use water other than sewage for irrigation. The motives, of course, are different; farming in case of cities is incidental to the problem of sewage disposal, whereas the problem of individual farmers is to secure water with which to grow crops. METHODS OF DISTRIBUTING AND APPLYING WATER Methods of distributing sewage for irrigation and practices in apjîlying it to cropped land conform generally to prevalent local standards (figs. 4 and 5). Methods of cultivation likewise are much SEWAGE IRRIGATION IN WESTERN STATES 11

FIGURE 4.—A, flow of sewage in one oí Uie outfalls from Salt Lake City, Utah ; 15, ditch carrying effluent from Visalia, Calif. ; C, concrete drop in distribu- tiou system on city sewage farm, Midland, Tex. ; D, sewage irrigation of walnut and peach trees on city sewage farm, Ontario, Calif. FIGURE 5.—A, irrigation of new alfalfa land with sewage effluent, Madera, Calif. ; B, border irrigation of alfalfa with chlorinated effluent from ImhofC tanks, Whittier, Calif. ; C, furrow irrigation of winter barley with effluent from ImhofC tank on city sewage farm, Lubbock, ïex. ; D, furrow-irrigated cotton on Casa Grande, Ariz., sewage farm. 12 SEWAGE IRRIGATION IN WESTERN STATES I3 the same as on other irrigated lands in the neighborhood, with the exception that in some places sewage-irrigated lands receive some- what more thorough cultivation in order to overcome the sealing effect of settleable solids.

FMUKE Ü.—Pm-row irrigation of oranges witli sewage effluent from Brea, Calif. Thus in southern California the use of underground pipe and the furrow irrigation of orchards are general in case of sewage-irrigated tracts (fig. 6). In northern California open flumes and earth ditches are the rule; alfalfa is irrigated in border checks, row crops in fur- rows, and pasture lands are often roughly flooded. In some of the

FIGURE 7.—Earthen storage reservoir at Lubbock, Tex., to hold effluent from Imholï tanks for use on city sewage farm. mountain States flooding from field ditches prevails, and elsewhere crops are irrigated in rills. Pumping plants are used in various cases, also field reservoirs for temporary storage or for accumulating irri- gating heads, as in case of other irrigated lands (fig. 7). A few in- stances of subirrigation were noted. 14 TECHNICAI^ BULLETIN 675, U. S. DEPT. OF AGEICULTURE

It is clearly dangerous to use open ditches for carrying effluents that are not completely disinfected, from one farm to another, par- ticularly along or across public roadways. There is always the pos- sibility that uninformed or careless persons may use the ditch water for drinking or laundering purposes. Some protection to the public is afforded Dy giving adequate warning, by signs, that the water is not suitable for domestic use; but the fact remains that the only assurance of safety lies in conveying the sewage in pipe, or at least in covered surface conduits. Independent distribution systems for effluents and for unpolluted water, without faulty cross-connections, are recommended by health authorities for localities in which the sewage constitutes only a part of the water supply for the entire locality, whether a single farm or a group of farms is involved; unless of course the entire district is designated as a sewage-irrigated district and crop selections are gov- erned accordingly. This is important in view of the primary use of sewage by individuals as a supplemental water supply. Otherwise wehere the farm program includes crops such as strawberries on which the use of ordinary effluents is prohibited by public authority, some part of the effluent-distribution system may be used to carry the originally unpolluted water to the strawberries. The California State sanitary engineers have encountered just such situations. They have also found, in some cases in which an unstable effluent was being diluted with unpolluted water to render it less offensive, an incorrect gradient at the point from which the clear water could be taken in one direction for the irrigation of high-grade crops and the sewage in another, resulting in an unintended reversal of sewage flow into the clear water. They therefore insist that the arrangement be such as to prevent absolutely the reversal of flow of sewage into the water used for the high-grade crops. This can be insured only bj^ the use of a channel from the clear-water system to the effluent system of such length and gradient as to eliminate any possibility of backflow of sewage through the channel into the unpolluted water. Tlie mosquito problem is important in a sewage-irrigation com- munity, for it is reported that mosquitoes of many kinds thrive upon sewage. Therefore, inasmuch as weed-grown irrigation ditches may become a source of propagation of mosquitoes, it is particularly nec- essary that ditches used to convey effluents be kept cleared of weed growth. Underground-pipe distribution systems are economically feasible for the irrigation of many high-priced crops; their use naturally obviates much of this trouble. Preparation of the land for sewage irrigation requires even more care than for irrigation with unpolluted water. In addition to the necessity for avoiding the accumulation of any kind of water on an irrigated field long enough to become stagnant or to injure vegetation, low spots may encourage the sealing efl'ect of settleable solids, with consequent jjonding of the effluent and creation of an unnecessary odor nuisance and an almost certain mosquito problem. Furthermore, it is necessary to confine the sewage water to the lands on which its use is approved by the health autliorities, and avoid the escape of any por- tion of the liquid to adjoining lands, particularly lands planted to crops which shoidd not be irrigated w^ith that effluent. Careless use in a number of instances has led to this result. The lower margins of SEWAGE IRRIGATION IN WESTERN STATES 15 the sewage-irrigated lands should therefore have levees to prevent any overflow. Kates of application of effluents to the soil are generally in line with those of water from other sources in the same area, although the total quantities applied in some cases exceed the usual local prac- tice on account of the continued availability of the effluent and the fact that the supply frequently exceeds the demand. It is only where there is competition for the use of the effluent, or where the cost of acquiring it is an important item to the Irrigator, that he has a real incentive to regulate his use of water per acre to the actual require- ments of the crops. In many of the sewage-irrigation areas these limiting factors have been absent. In line with this, some examples of poor sewage-irrigation practice were noted. There may have been a more or less unconscious tendency to disregard high standards in utilizing a waste product obtained at little or no cost, for the cost has visually been small. Lavish use is made of the sewage on a num- ber of municipal sewage farms, where there is no demand for use by individual fai-mers and absorption of the sewage is the primary objective. However, these conditions are not universal. Generally speaking, efficient types of irrigation conduits and methods of distributing and applying water from wells or natural streams have proved equally applicable to stable, reliably disinfected sewage effluents. Unstable effluents have become septic, with result- ing unpleasant odors, when allowed to remain in pipe lines following iiTÍgation. And effluents not reliably disinfected or adequately ñltered require particular care as to just where they are spread over the ground, as well as personal caution on the part of the Irrigators, and are not advisable for general irrigation use. IRRIGABLE LANDS There are many areas throughout the West in which sewage is not now being salvaged and utilized notwithstanding the availability of irrigable lands. This is the case particularly in the areas east of the ranges of mountains bordering the Pacific Ocean. There is of course considerable range in ability of the lands to pay for water and there- fore to carry the cost of so treating sewage before irrigation uwe as to accord with the standards of public-health authorities. (See Eco- nomic feasibility of sewage irrigation, p. 49.) The possibilities of economical use are naturally greater where the lands can be reached by gravity flow than where pumping is necessary. The practicable utilization, for irrigation, of sewage produced in communities close to the Pacific Ocean presents greater problems, for the largest cities are on the sea or on bays connected with it, and necessarily discharge their sewage practically at sea level and gener- ally at considerable distances from large bodies of irrigable land. Here the question goes beyond the use of sewage as a supplemental water supply. Eectifying these large quantities of sewage to con- form to standards of public sanitation and distributing them to points of use involve large-scale planning—educational campaigns, public organizations of water users, and heavy capital investments, as well as solution of the controversial problem of extending the ir- rigated area. The demand for irrigation water, great as it is along IQ TECHNICAL BULLETIN 675, U. S. DEPÏ. OP AGRICULTURE the southern Pacific coast, has not yet brought about definite planning of large sewage-irrigation developpients.

CHARACTER AND USE OF LANDS Coarse-textured lands, loose in structure, have proved better adapted to irrigation of crops with sewage effluents than have the heavier lands ; but that such physical characteristics are not essential is definitely indicated by the present study. Many tracts irrigated with effluents consist of clay loams and clays and therefore are com- paratively heavy; they re(iuire judgment and care in handling the sewage, but the same requisites also apply to irrigation with stream water. Overirrigation with any kind of water—applications in excess of the capacity of the land to accommodate it—leads to ponding and -waterlogging and consequently to impairment of productive capac- ity and to the creation of a mosquito nuisance.

CLASSES OF SOIL NOW IKEIGATBU WITH SEWAGE The soils on the tracts included in the canvass cover a wide range in texture, structure, natural drainage, and suitability for sewage irrigation. Many of the areas are covered by soil surveys; in ad(li- tion, in the course of the present study, soil samples were taken in most of the Texas areas and were examined at the agricultural exper- iment station at College Station. The prevailing textura! classes are as follows: Coarser textured, lighter soils: rercent Gravelly loams 5 Sands, sandy loams, and fine sandy loams 44 Loams and silt loams 16 Finer textured, heavier soils : Silty clay loams and clay loams 26 Heavy clay loams and clays of adobe structure 9 In arriving at the above classification, the number of textural classes of soil, rather than of soil types, was determined for each sewage-irrigation community. For example, the lands irrigated with sewage from Fresno, Calif., fall info tliree textural classes—sand, sandy loam, and fine sandy loam—although the soil survey of the Fresno area {48) maps such lands as Madera sand, Madera sandy loam, Fresno sandy loam, and Fresno fine sandy loam. The above per- centages are based upon the total number of textural classes on all the sewage-irrigated lands included in the study, taking each com- munity as a unit. They do not refer to areas of land. The coarser-textured, lighter soils, then, comprise 65 percent of the total, and the heavier finer-textured soils with preponderance of clay, 35 percent. In California the three groups of lighter soils constitute 84 percent; in Texas, on the contrary, the two groups of heavier soils are 70 percent of the total. Soils in some of the groups of coarser texture are underlain with tight subsoils or with hardpan, but generally the natural underdrain- age is reported to be good. Troubles on account of ponding and waterlogging have been encountered on some of the tighter soils. Alkali was apparent in greater or less degree in some of the areas. SEWAGE IRRIGATION IN WESTERN STATES 17

ALTERNATIVE USES OF THE LANDS Again taking the sewage-irrigation community as the unit, the results of the survey disclosed that the lands being irrigated with sewage would probably be put to the following uses if the sewage were not available for irrigation: Communities Irrigated farm or orchard land, good value 51 Dry-farm land 33 Farm and pasture land, low value 12 Residential, business, or municipal purposes 2 Idle 8 Total 106 Nearly three-fourths of the cases in California are in the first- named group, and three-fourths of those in Texas are in the second group (dry-farmed land). The cases designated "idle" are so classed because of the scarcity of water and the necessity of irrigating to produce crops in the localities involved.

PROXIMITY OK DWELIJNQS In about half the cases under consideration, and exclusive of the homes of farm operators, there are farm dwellings or residence areas very close to the irrigated lands. In seven of these instances the irri- gated areas are practically adjacent to cities or are included within city limits. In the other cases there are no dwellings very close, aside from operators' headquarters, the distances to the nearest ones ranging mainly from about y^ to 1 mile or more.

KESITLTS OF THE USB OF SEWAGE The observation of most of those who have used sewage for irriga- tion on lands included in the study is that, where any change at all has been noted, the soil structure has shown improvement rather than otherwise. Definite improvement has resulted particularly in case of soils of coarse or fairly coarse texture, deficient in organic content. This result is not at all surprising, in view of the fact that many sewage-treatment plants remove only a portion of the solids. Efflu- ents used in irrigation are commonly found to carry finely divided solids in suspension. (See Irrigation with treated sewage, p. 27.) Tendency of the topsoil to seal has been encountered in some areas. This has been successfully checked by plowing or disking the bare soil, and in case of growing alfalfa, by renovating annually with a harrow. Cumulative injury of this character has not resulted where the land has been properly cultivated, according to the experience of those who have followed this method of overcoming the difficulty. In this connection, attention is called to the discussion of salts in sewage effluents beginning on page 39. Thin layers of sludge were observed along the bottoms and sides of some ditches which carry effluents containing large percentages of settleable solids. This is of course objectionable, and often causes odors; it requires scraping or cultivating the surface area. 113972°—39 3 lg TECHNICAL BULLETIN 675, U. S. DEPT. OF AGRICULTURE

On the whole, the inquiry disclosed few specific cases of injury to the land—that is, impairment of fertility—which were not considered to be due to liarmful ingredients in the city water or to industrial wastes unsuitable for irrigation. Sewage resulting from the use of municipal water supplies high in alkali content, or otherwise unsuit- able for irrigation use on certain lands, cannot be expected to give good results/^ In a very few cases, for which the causes were not apparent or ascertained, poor crops resulted after several seasons of sewage irrigation.

CONTINUKD ABIIJTY OF LANDS TO PRODUCK CROPS WITH SKWAGE Tlie results of the present investigation indicate that many tracts have continued to produce crops with sewage irrigation year after year for long periods. While most of the sewage irrigation observed was with effluents, several long-time continuous uses of raw sewage were noted. On 85 separate areas, the maximum period of substan- tially continuous use of sewage (treated or untreated) is approxi- mately 49 years, the minimum 1 year (first season), and the average 15 years. Tlie average of 35 cases in California is 19 years, and of 29 cases in Texas 11 years.^^ Experimental data are not available to afford comparisons of the capacity of given tracts for sewage effluents and for clear water, and of their long-time reactions in producing crops. How^ever, no fac- tors have yet been called to the writer's attention which indicate more limited periods of usefulness in irrigating with sewage efflu- ents than with stream or well water in the same community, provided the same care is used in each case and the sewage is free from injuri- ous industrial wastes. OWNERSHIP OF LANDS In 46 of the areas included in the study the sole use of sewage for crop irrigation is by individual farmers. In 10 of these areas the sewage so used is taken wholly from outfalls or disposal plants; in 12 others it is wholly discharged into stream channels, and diversions for irrigation are made therefrom ; in the 24 remaining areas indi- viduals use a part of the direct sewage flow and in 3 such cases they also divert from streams into which the remainder of the sewage has been discharged. In the other 67 areas included in the study there are municipal sewage farms on which sewage is used for irrigation; but surplus effluent above the needs of 25 of these sewage farms is used by neigh- boring farmers who receive it directly from the plant or sewage farm, and in 3 additional cases diversions by individuals are made from streams into which the surplus effluent has been discharged. Individual use of sewage is therefore important in the areas in which sewage irrigation is practiced. Many private users pay noth- ing for this service : in fact, two cities pay the farmers to take the effluent. Some individuals have obtained perpetual rights as a part

"The riuiility of spwage is discussed eLiowlierp (p. ."50). 12 At BorliTi. Gernmny, irrijiation nt tlie first of the sewase farms to be purchased was commenced durini; the'winter of 1875-76 (.«, p. 8; W, p. 8). It was reported in 1928 tliat no changes liad been made in this first (Osdorf) field except to increase the size of the settling jtonds. I'rior to commencing the sewage-irriçation program, experimental Irrigation was begun on 5 acres (part of the Tempelhofer Field) in 1870 (-iö, p. 3), For other comments on the Berlin sewage farms (20, 2~, iS). SEWAGE IKRIGAÏION IN WESTERN STATES 19 of the consideration for sales of land or riglits-of-way. Only a few annual rentals or original purchases of effluent involve substantial compensation. MUNICIPAL SEWAGE FARMS Thirty-six of the 67 operating sewage farms controlled by the organizations in charge of sewage disposal are in California and 24 in Texas. In all excepting five cases cities control and have title to the fiirms. The exceptions are cases in which municipalities are served by commercial sewer companies, or in which institutions are in charge of sewage disposal. The city farm had its inception in the need for disposing of sewage upon land. The installation of treatment plants has made it permis- sible for many cities to discharge their effluents into public streams and thus to discontinue their farms; not h withstanding this, many of tlie fai-ms have been continued in operation as a source of revenue. The citj' farm is less of a factor in utilization of sewage than formerly but is of some ini])ortance from an agricuhvtral standpoint.

FiGUKE 8.—Portion of city sewage farm, Fresno, Calif.

LOCATION AND APPEARAXCE The location of the municipal sewage farm is governed by the location of the disposal plant, which in turn is normally at a low elevation with respect to the city. In most cases the farms are close to the city limits and in a few instances within them. Criticisms liave been directed at various sewage farms on the grounds of odors, unsightliness, and depreciation of land values, in some instances with good cause; but these objections tend to decrease or disappear if the anticipated unpleasant experiences of neighbors do not materialize. Experience shows that it is practicable to main- tain such farms in an unobjectionable manner; for example, the Pasadena city farm now is flanked on two sides by built-up resi- dential subdivisions and is close to the older business district of San Gabriel. Other farms make a good appearance (fig. 8). 20 TECHNICAL BULLETIN 675, U. S. DBPT. OF AGRICULTURE

The largest city sewage farm included in the study is that owned by Fresno, Calif., consisting of 812 acres; the smallest covers about 5 acres, and the average is 129 acres. Effluent outfall from /mhofftank--^^"^ Manhole OM.H. Irrigation ditches. . Direction of flow in furrows ^ Division lines between furrows running in different directions. Prams Contours ^^70- fences —«—►

FIGURE 9.—Lay-out of fields on city sewage farm at Kerrville, Xex. SKWAGE IKIUGATION IN WESTERN STATES 21

Figure 9 shows a sketch of the municipally owned and operated farm at Kerrville, Tex., based upon a contour map in the office of the city manager. The entire city farm contains approximately 210 acres, of which some 52 are cleared and 48 irrigated. Much of the adjoining higher ground is range land. Excess effluent not needed for irrigation is disposed of in a low area on the farm outside the southeastern corner of the irrigated fields. The sewage production is reported as averaging 212,000 gallons per day in the summer, or approximately 20 acre-feet per month. This flow has not proved adequate to irrigate the entire area properly. Generally speaking, the gross areas of sewage farms are con- siderably larger than the net areas capable of using the sewage for crop irrigation. Tliis has resulted in some cases from the necessity

FiGuiiK 10.—Sijriiikliiig filter at Madera, Calif., ou city sewage farm, with municipal airport in background. or desirability of having a fringe of unirrigated land around the irrigated portion,'^' or from the inclusion of areas for stock-range purposes, for winter disposal of the effluent, and for other municipal purposes such as garbage disposal, athletic fields, or municipal airport (fig. 10). On the other hand, some of the larger cities have sewage farms with irrigable areas considerably smaller than the areas which it would be possible to irrigate efficiently with the quantities of sewage available. Population increases and development of the character of sewage treatment have reduced the importance of some of these farms. For example, San Antonio, Tex., w^th a population only a small fraction of what it is now, purchased 630 acres in 1895 for a sewage farm {33, p. 7ß) ; the present irrigated area on this farm is a very small per- centage of the total area irrigated with San Antonio sewage. The

1^ Experience of sanitary engineers in the California State Department of Health indicates that where settled or clarified sewase, not oxidized, is used for irrigation on sew- age farms under current methods of handling, a buffer strip of at least one-fourth mile around the farm should be provided, and if this strip is to be farmed, it should be irrigated (if at all) with water other than the settled sewage. It is further stated that careful handling of sewage effluent in pipe-distribution systems and provision for de- odorizing at critical times would allow narrower buffer strips (K, p. i). 22 TECHNICAL BULLETIN 675, U. S. DEPÏ. OF AGRICULTURE

Pasadena farm has been reduced considerably in size and now has 218 acres with irrigation facilities, yet the annual production of effluent from the disposal plant is about 9,400 acre-feet, most of which is dis- charged into a stream channel the waters of which are subsequently used for irrigation by others. The quantity of effluent available on the Fresno city farm during the irrigation season is sufficient to ir- rigate an area much larger than the city farm area and has been used in recent years on neighboring lands as well as city-owned lands. Twenty-five of the cities having sewage farms in operation are delivering surplus effluent directly to private users nearby.

OPKRATIOX Twenty-eight of the municipal farms are wholly operated by the organizations controlling the sewage disposal, 34 are wholly leased or contracted to individual operators, and 5 are partly operated by the municipalities and partly leased or contracted to individuals. The term "contracted" refers to arrangements under which individuals undertake to perform designated acts in consideration for the use of the land and effluent, as distinguished from formal leases. More than two-thirds of the leasing or other arrangements with individuals involve cash rentals, usually with an obligation on the part of the lessee to dispose of all the eíHuent. The cash considerations are small, very few exceeding $10 per acre. Where the city operates the farm, at least one regular employee usually devotes his entire time to this duty, and on the smaller farms he cares for the disposal plant as well. The large farms naturally require correspondingly larger staffs. In some cases a city employee who has other duties—such as the city marshal—also looks after the farm. The degree to which leasing, as a general policy, proves satisfactory appears to depend principally upon the ability of the city to find a good lessee. In sev- eral cases included in the study the municipalities have had unsatis- factory experiences with lessees. CROPS Crops irrigated with sewage in western areas are those commonly grown under irrigation in the locality. The yields are reported to compare favorably with those produced with surface and underground water; in fact, the reports generally indicate higher yields with sew- age effluents than with other water applied under comparable physical conditions and with equal care (fig. 11). EXPERIMENTAL DATA Unfortunately, little experimental work to determine differences in yields of crops grown under sewage irrigation and those grown under irrigation with other water has come to the writer's attention.^* Experiments at the Florida Agricultural Experiment Station, car- ried on in cooperation with the Bureau of Agricultural Engineering,

'* Sewage irrigation experiments at tlie Iowa Agricultural Experiment Station (Summary of Six Years Experimentation in Sewage Irrigation, not publislied, tiiree typewritten pages in addition ot tables and cliarts, Apr. 1, 11)14), applied to plots irrigated with sewage and tliose not irrigated at all ; tliey allowed favorable results on yields of barley, beets, and grasses, but not alfalfa and clover. Experiments at Vineland, N. J., carried on by local people with the cooperation of the Bureau of Agricultural Engineering, likewise compared results from sewage irrigation and no irrigation ; they showed substantial increases in yields of corn with sewage irrigation (28). SEWAGE IKllIGAÏION IN WESTERN STATES 23

'■m-wmm-

FIGURE 11.—A, Walnut trees irrigated vvitli eliloriiiiited effluent, I'omona, Calif.; B, vineyard irrigiited solely with sewage effluent, Kingsbury, Calif. ; C, alfalfa on sewage farm, Visalia, Calif. 24 TECHNICAL BULLETIN 675, U. S. DBPT. OB^ AGRICULTURE compared yields of Napier grass and Japanese cane from plots irri- gated with septic-tank effluent and those not irrigated, and during a portion of the time, yields of Japanese cane from a plot irrigated with city water (47)- Concerning the results, the report states (47, pp. ^-^) : There was a marked increase in tonnage of silage of Napier grass and Japanese cane from the plats irrigated with sewage over that from those not irrigated during 1922-25, inclusive. There was no marked increase in yield of silage of Napier grass from the plat irrigated with city water over that from plats receiving no irrigation. Since the yields from the plat irrigated witli city water showed only a slight increase over those from the nonirrigated plats, then the greatly increased yields from the sewage-irrigated plats must not be due to an increased water supply alone. The plant nutrient materials supplied by the sewage effluent together with the increased water supply were apparently eiïective in bringing about the increased yields during the period that the plants were irrigated with this effluent. Results of irrigation with effluent at Poona, India {i9), as sum- marized in the Experiment Station Record, indicate that much heavier yields of sugarcane were obtained than by "water" irriga- tion. Under continuous irrigation with moderate quantities of sew- age the electrolytes tend to increase, though the organic matter does not persist. Even before reaching the stage of sewage sickness, it was found that the soil attained a condition when either irrigation with water or rain or fallowing became necessary prior to the resumption of cultivation operations. Whatever fertilizing value the sewage may contain is important economically. However, in much of the West, the water supply it- self, if of good quality, is one of the most important factors in crop production. No factors have come to attention which would indicate lower yields from sewage effluents, properly applied to the land, than from clean water.

CROPS IRRIGATED WITH SEWAGE IN WESTERN AREAS Table 1 shows the character of crops found to be irrigated with sewage in the course of the present study. This includes all kinds of municipal sewage, and includes diversions directly from outfalls and treatment plants and diversions from watercourses into which the sewage had been discharged.

TABLE 1. -Crops irrigated with sewage in 112 western areas in 1934 or 1937 or both years'

Localities in-

Crop Califor- Other nia States

Number Number Number Number Small grain and field corn. 25 18 18 61 Alfalfa 24 8 19 51 Orchard and vineyard 23 6 4 33 Berries 1 0 2 3 Vegetables 4 16 11 31 other harvested crops 15 14 10 39 Pasture 16 32

' Includes 95 communities in which the sole use of sewage is directly from outfalls or treatment plants, 10 in which sewage is used only after discharge into a stream channel and rediversion for irrigation, and 7 in which part of the supply is taken for irrigation before discharge into a stream channel and part after such discharge. SEWAGK IRRIGATION IN WESTERN STATES 25

Orchards include both citrus and deciduous trees; berries are busli fruits. The list of vegetables is extensive. In the order of number of places in which found, the most widely distributed being listed first, they include : Tomatoes, beans, onions, peas, cabbage, beets, cucum- bers, sweet corn, carrots, pumpkins, radishes, squash, lettuce, okra, peppers, spinach, eggplant, chard, celery, parsnips, rutabagas, tur- nips, asparagus, Jerusalem-artichokes, parsley, and rhubarb. These vegetable ai'eas range from small gardens cultivated by the sewer- plant opei'ator for his own use to large commercial plantinç;s. The "other harvested crops" comprise, in the same order of number of places in which noted : Grasses, cotton, potatoes, melons, sugar beets, hegari, nursery, popcorn, hops, flowers and shrubs, beet seed, and peanuts. CROPS IRRIGATED WITH UNTREATED SEWAGE

The recheck in 1937 disclosed eases of irrigation of the following crops with raw or untreated sewage, shown in table 2.

TAHLE 2,—Crops irrii/ated with iiiitrcuted Hfiruov in IÍIS7 in 7.T wfKtrrn urcan

liocalities where sewage was diverted—•

Crop From Directly stream frnni channel Total outfall into which discharged

Small grain and corn Alfalfa ------Orchard - Vegetables --- - - Other harvested crops (potatoes, cotton, grasses, sugar beets, hegari) Pasture — - —

The 15 areas to which table 2 relates include 3 in which the sew- age was diverted from watercourses into which it had been dis- charged by the city producing it. In one of these cases sewage con- stituted most of the stream flow throughout most of the irrigation season ; in another case it was a substantial percentage of the total ; and in the third case irrigation diversions were made immediately below the outfalls. SAFEGUARDS AND REGULATIONS OF PUBLIC-HEALTH AUTHORITIES

WHAT THE PUBLIC WELFARE REQUIRES The interests of the public in sewage irrigation are twofold—the efficient utilization of supplemental water supplies to the extent needed for crop production, particularly in time of drought, and above all the maintenance of health. To coordinate these aims it is necessary that the requirements of sanitary authorities be strictly followed; and it is further believed, on the basis of present knowl- edge, that adequate protection to the public is afforded by nothing 113972°—.39 4 26 TKCHNICAL BULLETIN 675, U. S. DEPT. OF AGRICULTURE short of the highest standards adopted by public-health authorities who work in this field. CHARACTER OF SEWAGE USED IN CURRENT IRRIGATION PRACTICES The priiicii)al methods of treating sewage in the 113 localities included in the study in which sewage is used for irrigation, as of 1937, are summarized in the following tabulation : Treatment plant Localities linhoff tanks 1 ^^ 34 Inihoff tanks and filters ''■ 13 Septic tanks ' 27 Activated-sludge plants * 9 Mechanical clarifiers 5 Mechanical clarifiers and filters 3 Other devices ' 7 Subtotal 98 No treatment 15 Total 113 1 In 1 case, combined with a sei)tic tanli. 'In several cases, effluent not filtered when being used for irrigation. 3 In a few cases, followed by filtration or clarification. ^ In 1 case, combined with an ImholT tanii. « Principally sedimentation basins and lagoons. It will be noted that the Imlioft' tank, used alone or in conjunction with a filtei'. is the most common treatment device in tliese sewage- irrigation areas (fig. 12).

FIGURE 12,—Imhoff tank, Yreka, Calif. In only a few cases did the effluents from these plants receive chemical disinfection prior to irrigation use; a few were chlorinated only wlien discharged into stream channels. Likewise, in several com- nnmities in wliicli sprinkling fihers supplement otlier devices, sucli as Imhotf tanks, the effluents are customarily bypassed around the filters when intended for irrigation. SKWAGK lltUlGATION IN WESTERN STATES 27

IBRIOAnON WITH RAW SKWAGK TAKKN DlKWírLV FROM <>UTfAU.S

Irrigation of cultivated crops with raw sewage taken directly from outfall lines was being practiced, in 1934 or 1937, or both years, in 16 localities. Treatment plants liad been installed in several of these places between 1934 and 1937, but the majority of the group were continuing the use of raw sewage for irrigation, at least in part, in 1937. Furthermore, such use had been begun in two comnnmities in the meantime. In another case (not included in the above total) creamery waste alone was so used; and in two additional areas raw sewage was taken from outfalls and applied (o uncultivated i)asture lands. It may be noted that in four instances in 1934 and at least three in 1937, raw sewage was being diverted for irrigation directly from out- fall lines above treatment plants. In two of these cases in 1937, the law sewage was used for irrigating vegetables, some of the character generally eaten uncooked. The city officials in both cases were cog- nizant of the situation, and apjiarently did not approve of it, but considered that such diversion of the untreated sewage Avas legal. I)is])osition of the vegetables so produced was left to public-health officials.

IltUIGA'nON WITH tJNTHEATEl) SEWAGE AFrER DISCHARGE INTO S'luEAM CHANNELS

The use of water from a stream carrying large quantities of fresh sewage is necessarily a use of sewage. Natural purifying processes are at work, so that tlie sewage becomes less offensive with increasing distance from the outfall. The amount of dilution with stream water is also an important factor. Various diversions for irrigation are made from stream channels that are dry dui-ing part of the summer excepting for the sewage discharged into them. Subsidence and oxidation take i)lace here also, but the diversion and use of untreated sewage from a dry channel close to the outfall is liot far removed from the use of raw sewage. In five cases included in the study, use was being made of untreated sewage in varying degrees of dilution with stream water and oppor- tunity for oxidation and settlement of the solids.

IKHIGATION" WITH TREL4TEDI SKWAGE

The sewage used for irrigation in nine-tenths of the 113 localities received (in 1937) some kind of pretreatment; although as noted else- where, in several places equij^ped with treatment plants the diversion of some raw sewage for crop use was observed from the outfall lines above the disposal plants. Well-treated effluents, aside from the health factor, are less un- pleasant to handle than the unstable ones. Furthermore, the less the proportion of settleable solids in an effluent, the less noticeable are the depositions of sludge in irrigation ditches and fields. A wide variation was found, as would be expected, in the appear- ance of the sewage effluents used for irrigation. Some wei-e clear and sparkling; some, from ¡jonds or lagoons, were green in color; some were cloucly, with more or less odor; and some carried large quantities of visible solid matter. Tests of settleable solids in effluents being 2g -rECHNICAT. BUT-T.ETIX 675, U. S. TiKPT. OF AGRICULTrRE used for irrij^ation were made with an Imhoiï cone in 17 localities in California and 11 in Texas, allowing a liter sample to settle for 2 hours. The readings ranged from a trace to 4.0 ml, the median being 0.525. Seventeen of the effluents so tested were from Imhoff tanks and 6 from ordinary septic tanks; of the 14 effluents in the upper half of the range, that is, showing the highest proportions of settleahle solids, 13 were from Imliofï tanks. It should be noted that only one sample was tested from each effluent; hence the results of the sampling sim2)ly indicate its condition at the one time.

STATE POLICIKS CONCERNING SEWAGE IRRIGATION Several of the Western States, particularly those in wliich sewage irrigation is important, have formulated policies for the regulation or guidance of such practices. The basic statutes vary widely. State departments or boards of health have certain powers in the matter of maintenance of public health, disposal of sewage, abatement of nuisances, and prevention of pollution of streams and other sources of water supply. Regulations formulated by such bodies affecting sewage irrigation are generally based u])on their control over sewage dÍH])osal or upon their ])ower to prevent the sale of food products determined to be dangerous to the ])ublic health. Policies ai)plying to ai'eas included in tlie ])resent study are mainly as follows :

A permit must be obtained from the State superintendent of public health before land is irrigated with sewage effluent for the produc- tion of crops to be used for human consumption. The permit is for a limited period and specifies the crop and the period of growth and inaturity. No permit is to be issued if the produce is of such nature tluit it can be used witliout processing to destroy disease organisms. The State superintendent of public health is authorized to seize and destroy any jiroduce offered for sale, raised by the use of sewage effluent for irrigation, that is capable of being used Avithout being j)r()cessed by heat. CALIFORNIA

A permit from the State Dei)artment of Public Health must be obtained before sewage is disposed of for iixigation. The regula- tions i)rohibit the use of untreated sewage containing human excre- ment for irrigating growing crops. Effluents of settling tanks, or other partially tlisinfected effluents, shall not be used to water grow- ing vegetables (except those grown exclusively for seed purposes) or low-growing fruits in contact with tlie gi'ound, or vineyards or orchards wlien the windfalls or fruit lie on the ground ; but nursery stock, cotton, and such field crops as hay, grain, rice, alfalfa, sugar beets, fodder corn, cow beets, and fodder carrots may be so watered. Milk cows shall not be ])astured on land moist with sewage or have access to ditches carrying sucii sewage. The foregoing restrictions do not apply against the use of well oxidized nonputrescible and reliably disinfected or filtered effluents which always meet a specified bacterial standard. SEWAGE IRRIGATION IN WESTERN STATES 29

No domestic sewage or water containing domestic sewage in amount and condition such that bacteria of the coli-aerogenes group are present in quantities of 10 or more per cubic centimeter, shall be used to irrigate or be permitted to overflow any fruits or vegetables for human consumption, the edible portions of which grow in the ground or above it within 1 foot of tlie surface, except with the writ- ten permission of the State Board of Health granted after an investi- gation of the ]>articular case. The request for permission is required to state full details supporting a claim that there is no reasonable possibility of impairing the public health.

The State Board of Health has police powers, but prefers to work with the municipalities. The preference is that the effluent used for irrigating any crop be chlorinated prior to ii-rigation to protect the Held workers. It is considered that irrigation of vegetables with sewage not disinfected involves a hazard.

MONTANA The sale of all vegetables grown on farms irrigated with human sewage is j^i'obibited, due to the possible transmission of typhoid fever. NEW MEXICO The Department of Public Welfare is empowered to pass necessary regiilations. It is believed that treated sewage should not be used to irrigate vegetables, but the department has sjjonsored the use of treated sewage for the irrigation of forage crops.

The State Board of Health does not approve of the use of sewage for irrigation of any crops which may be eaten raw. Completely treated or well oxydized sewage effluents, which are disinfected with chlorine, may be used for some kinds of crops without apparent dan- ger to public health. Sewage irrigation of crops uj)on which milk cows are pastured is disapproved.

The Department of Heahh acts In an advisory capacity only. The de])artnient is strongly opposed to the use of sewage for irrigat- ing any vegetables, berries, or foodstuffs which may be eaten raw, and believes that there is an aesthetic undesirability and some hazard In irrigating with sewage effluent any foodstuffs intended for human consumption. Pasturing of milk cows on lands iiTÍgated with sewage is not recommended. UTAH There are no regulations governing sewage irrigation, but the board of health endeavors to maintain sufficient supervision OTer the practice to prevent any great menace to the public health. 30 TECHNICAL BULLETIN 675, U. S. DEPT. üF AGKICULTUKE

WASHINGTON The use of sewage or effluents for irrigating growing crops is pro- liibited without prior written approval from the State director of health. The approval specifies the kind of crops, quality of the effluent, and any other essential requirements for protection of the public health.

SANITARY AND AESTHETIC BASIS OF HIGH STANDARDS State policies governing the use of sewage for irrigation are based for tlie most part obviously on sanitary grounds. However, aesthetic considerations are economically important so far as they affect the sale of food products from large areas and in some cases have un- doubtedly influenced the formulation of high standards of use.

U«E OF KAW NhWAUE GENEKALLY FBOWNEl) UPON Notwithstanding the fact tliat raw sewage was being applied to crops in some localities in 1937, the practice has little support among ])ublic-health authorities. It is genei-ally considered hazardous, and therefoi'e is either definitely prohibited or at least discouraged by State officials. Sewage at a given time may or may not contain pathogenic oi'- ganisms.''^ In case of illness among the inhabitants contributing to the flow, particularly in epidemic form, the sewage may carry large quantifies of such organisms not otherwise disposed of by direction of the public-health authorities. The ever-present possibility of such occurrence is considered by health authorities to render untreated sewage a possible source of infection. It is appi'eciated that irrigation with raw sewage has been carried on for many years in many places, both in this country and abroad,^" and that evidences of ill results are generally absent or not conclu- sive. Nevertheless, if the hazard exists, its perpetuation is not in the public interest.

fIBCUMSTANCES UNDEli WHICH THE USE OK EFFLUENTS IS APPROVED BY HEALTH AUTHORITIES Effluents from some treatment plants are chlorinated or filtered in order to meet the requirement of health authorities that they be made innocuous. Obviously, the degree to which an effluent is continuously stabilized and disinfected is the measure of its safety to the public. From the standpoint of use in irrigation, the fertilizing value of sewage in a given state, important though it may be in crop produc- tion, is secondary in public importance to the freedom of the sewage from injurious quantities of disease-producing organisms.

^^ In experimental work at Stanford University, Calif., in 19ÍÍ7, samples of raw .sewaiie were collected from a clarifier influent channel. According to the report (16) : "Snc- cessful isolations of K. typhi in one ml. iwrtions of raw Palo Alto sewage were made in several instairces. The isolation of viable typhoid organisms in the sewage of a city having a high standard of sanitation and without having had an outbreak of typhoid fever in :-!0 years emphasizes the need for constant vigilance if effective barriers are to be maintained between infectious material and susceptible hosts." "As to sanitary conditions on the Berlin sewage farms, see (,58, pp. U)- See also (40, )». »). SKWAUK lUIUÜATlUN IN WESTERN STATES 31

Investijiators have, demonstrated the survival of certain disease- prochicinj; oro;anisnis in sewage and surface water and in soil for a|)i)r(HMul)l(' periods of time. For example, typhoid bacilli have been found to decrease rapidly in sewage during the first few days, the remnant persisting for wee]septic tank; (2) reduction of 90 to 99 percent during 6 liours aeration in an activated-sliRlge j)rocess; and (3) removal of 95 percent in trickling filters at constant dosage rates up to 12 million pillons per acre per (lay and 9(1 to 99 jiercent at (S.ti million gallons daily, and 99.9 percent wlien operating intermittently at effective rates up to 2.8 million gallons daily 1" (fig. i;i). Further reduction of disease organisms takes place in the soil, de- ])ending on th(> character of organism, character of soil, moisture- retaining capacity of the soil, moisture, and temi)erature (3, .%'). The fact that sewage has passed through some kind of treatment- plant therefore does not necessarily mean that it is innocuous. Some kinds of treatment are directed primarily to stabilizing the sewage— removing suspended solids and ]neparing the effluent to resist putre- faction—with accompanying destruction of disease-producing organ- isms in greater or less degree. Unless the treatment process, in addi- tion to sinlimentation of solids and oxidation of organic matter, accomplishes a high degree of bacterial removal, there is apparently no assurance that the effluent may not still contain pathogenic organ- isms in sufficient numbers to constitute a potential source of infection under favorable circumstances. Some sewage treatments include chemical disinfection of the effluent, usually by clilorination ; others include filtration for bacteria removal. From a sanitary standpoint, it is theoretically true that any kind of irrigation water that does not meet the recognized bacterial stand- ards for clomestic water is a potential source of danger. As a matter of fact, however, in no instances in the present studv have epidemics been traced definitely to irrigation with sewage in which the Bacillus coll content has been substantially reduced, even though the standard of drinking water was not attained; and in only a few cases have indi- vidual cases of illness been suspected of coming from such sources. Considerable investigational work has been done to determine the survival of pathogenic organisms, and apparently much has yet to be learned ; furthermore, new problems arise from time to time.

"The Eenernl siibiecl has been discussed .niul literature cited in an unpniilished manu- script ■ UriiKKTY, M 'K. SF.WAIiH WATKR AS A SOnil'K OF IIUtlCATION W.4TER. March 1934. 1» I'or other recent worl;, .see {IX, 1», -l')- For survival in sea water, see (i). 32 TECHNICAL BULLETIN 675, U. S. DEPT. OF AGRICULTURE

Objections commonly raised to sewage-irrigation practices are based on aesthetic as well as sanitary grounds. Aesthetic considera- tions are important in that they may and sometimes do affect the market for produce from sewage-irrigated farms.

FIGURE i;!.—.1, ac-tivatod-sludse pliiiit, Medford, Oreg. ; It. clariflcation and Kpi'iiikliiif; filter plant at Kapid City, S. Dali.

\'EOETABLES AND SMALL FRUITS The direct application of polluted water to vegetables which may be eaten uncooked is not only objected to by sanitary authorities but i.s obviously repugnant from an aesthetic standpoint. In case of veg- etables always eaten cooked, regardless of whether the danger of in- fection is minimized or entirely removed by the cooking, aesthetic objections to the bringing of such foodstuffs into the kitchen remain on the part of many people. The same considerations apply to low- SKWACK lUFíKJATION IX WESTKIÍX STATES 33 growiiijí small fruits such as strawberries, which remain close to or in contact witli the firound. If many consumers in a given area have such olijcctious, the marketability of vegetables grown commercially may be impaired, and the result may extend to many food products fi'om the siime general locality.

I'TcrnE 14. A. iiriKalioii oí puiiipkiiis willi parlúiüy tivateil íscwajíe, a practice that is iiol nT(jiuiuciuled ; II, í'urnnv-irriKatiou ol' uuionti gruwu for sued, using scwase clfluciil. Hence, a rule, such as that of California, that vegetables (unless orown for seed) and low-gi'owing fruits sliall not be irrigated with eiUuents unless highly disinfected or otherwise treated for bacterial removal, in addition to the high sanitary standard which it sets ap- pears sound from an economic standpoint and otherwise entirely reasonable (fig. 14). 34 TECHNICAL UULLETIN 675, U. S. DEPT. OF AGRICULÏUUE

OTHER FOODSTXJPTS AND rEïa)STDrFS Aesthetic considerations have less bearing in case of food products which commonly do not come to the kitchen directly from the truck •rarden, and even less with feed foi- livestock. Sanitary considera- tions nevertheless are highly important. Where the circumstances are such that the probable danger of com- municating infection to tlie public is remote, health authorities do not prohibit sewage irrigation. For example, it is considered by c-ompetent authoi'ities that the use of sewage effluents at least par- tially disinfected, or so treated as to reduce substantially the maxi- nuiin quantity of pathogenic organisms carried in the sewage, is not l)articidarly liazardous in irrigating grain or sugar beets, or alfalfa necessarily cut after the ground has dried, or vine and tree fruits ])icked a sufficient length of time after irrigation to insure thorough drying of the topsoil, or seed crops, or textde crops. It is true that avian tubercle bacilli have been found to survive for considerable periods of time in sewage, stream water, and sterile soil {36, 37), but the criterion of these authorities is the probable danger involved.

PA8TÜKAGB Pasturing of livestock on sewage-irrigated fields raises questions as to the danger of conmiunicating infection to the animals and thonce to consumers. Discovery of infestation with cysticercus bovis. or tai)P- worni, in beef cattle [)astured on an Arizona field irrigated with i)ar- tially settled sewage suggested the [¡ossibility that the worms had been transmitted through the sewage. It appeared that the cattle, in addi- tion to grazing on the irrigated land, persisted in drinking effluent in the ditch in preference to fresh water. The State sanitary authorities thereupon reconnriended that no cattle be fed on sewage-irrigated land, and adopted the policy that if forage crops were raised on such land they be harvested on a dry field and fed from the bin. Pasturage of dairy cows on sewage-irrigated fields involves the pos- sibility that the cows' udders may come in contact with sewage flowing in a ditch or recently applied to the land. It will be noted that the California regulations prohibit the pasturing of milk cows on land moist with settled or undisinfected or partially disinfected sewage effluents or across which ditches are carrying such sewage.

POSSIBILITY OF POLLUTING GROUND WATERS BY SEWAGE IRRIGATION The extensive use of sewage for irrigation in an area in which un- derground waters are available, particularly for domestic purposes, raises a question as to the possibility of so polluting such waters as to render them dangerous for use. In view of the reports of diseases held attributable to pollution of ground-water supplies, this potential hazard cannot be lightly dismissed."

1» Fifty-seven outbreaks of typhoid fever and dysentery during the decade 192()-i;ii. üttributable to pollution of ground-water supplies, were reported in various parts of the United States. Surface pollution of shallow wells accounted for .52.n percent of the out- breaks; but undergiound polhllinn of wells or sjiriufis in creviced limestone accounted lor 1!).."! i)ercent, and wells oi- spriniis, source unknown, 7.0 iwrcent {12). Dui-ing the |)eriod IftSO—:«; there were 170

Certain kinds of soil, particularly fine sands, have natural purifying properties; it is for this reason that sand filters are used in some sew- ■dge treatments to effect bacteria removal. If the soil structure is so porous that the effluent passes through rapidly, as would be true in l)roken or dissolved rock formations and in coarse gravel, the effect is correspondingly reduced. 'ITie character of the soil therefore is a factor in the ])roblem. Studies at Rockville Centre, N. Y., showed effective removal of bacteria from an activated-sludge effluent (dis- charged upon natural sand beds and thence seeping into the natural ground waters of the locality) after passing through less than 400 feet of soil consisting principally of fine sand, although chemical pollution in the seepage was traced more tlian 1,500 feet (6). Studies in various portions of South Carolina, involving compact red clay, sand clay, and sandy soil on a sandstone bed, indicated that the spread of pollution from a focal point is limited in scope; that typhoid and dysentery bacilli may survive in soil for appreciable periods varying with moisture, I'eaction, and temperature conditions, but do not spread either laterally or otherwise unless carried mechanically by water, the direction of penetration being in the direc- tion of How of the water. Penetration in relatively porous soil was limited to 2 to :5 feet, and in compact soil less than 9 inches. How- evei', the conclusion was emphasized that any form of subsoil dis- l)osal should be designed with a knowledge of the character of the soil and particularly with due regard to the ground-water level; the vertical distance between the source of pollution and the ground water being the significant factor, and the horizontal distance hetw^een soui'ce of ])ollntion and water well being of relatively slight im- j)ortance except when there ai-e underground channels or cracks in the soil (24). A definite relationship between the spread of pollution and the flow of gi'ound water was established in experimental work at Fort Caswell, N. C. in fine sandy soil (average porosity 48 percent, effec- tive size of grain 0.14 mm) through which ground water was moving slowly (0.975 foot per day). Bacilhis coli were recovered from the ground water at distances ranging from 1 to 232 feet from the point of application; uranin up to 450 feet. Both uranin and B. coli traveled in only one direction—that of the ground-water flow. It was found that pollution in travel did not appear to expand laterally, but rather to contract laterally in the path of travel ; hence if the direc- tion of flow were unknown, distance would be the chief factor in safety. Experimental B. coli infection had remained alive for 2 years 8 months w^hen last examined, but died in soil when dry a sufficient length of time (4^). With a more porous soil and a more rapid underground flow than encountered in the foregoing experiments, it is possible that different limits upon the spread of pollution would be found {30). A portion of the water applied to soil in crop irrigation percolates downward beyond the reach of plant roots and eventually may aug- ment an underground water supply. The portion that so escapes is

wells; 7 l>y raulty construction; 2. pi)lltition of well« froiii a»l.i;t<'i'iii ri\cis oi- I.tkos ; 11, pollution of wells from adjacent sewers oi- se\vai;e tanks: 5. tindei-^'rotiiid pollmioii of wells in creviced limestone or fissured rock; 1, underground pollution of well by surface con^ taniinntion tlirough an iibancloncd well ; 4. overflow of sewer or flood water into top of weii ca.sing ; and 12. undtirsround pollution of well or spring from source tiiiUnowu (J.-i). 36 TE(^HNI('AL BULLETIN fi7r>, I!. S. DEPT. OF AGRirT'I/rrRK usually less with careful than with poor irrigation methods. It is this portion of an effluent that is of principal concern from the stand- point of pollution of ground-water supplies, ahhough rains are effec- tive in carrying pollution downward (24). Obviously, the more highly stabilized and disinfected an effluent is when applied to the soil, and the more careful the methods of application, the less should be the likelihood of its carrying substantial quantities of pathogens into the ground water. Character' of the soil and location and direction of flow of the gi-ound water appear from the foregoing data to be the important fac- toi-s in limiting the spread of pollution fr(mi an effluent not disin- fected before being applied to the soil. It seems hardly likely that enough ])atliogenic organisms will survive a long soil-filtration proc- ess to pollute seriously a water table deep beneath the surface. On the other hand, the op])()rtunities for pollution may be considerable in limestone or other broken or porous water-bearing formations readily accessible to recently ai)plied sewage. The survival of various organisms for various periods of time has been demonstrated. There- fore, unless an effluent has been disinfected or otherwise treated for bacterial i-emoval, its safe use for irrigation over a large area within which ground waters are withdrawn for domestic purposes appears to require knowledge of both soil and ground-water conditions. The danger lies in uncertainty as to these conditions. Where effluents have been so treated as to be rendered innocuous, not oidy is Ihe danger of polluting underground water supplies re- moved, but the effluents become available for augmenting these sup- plies for subsequent use. For sproadiiii; on Kravols In nn nttempt to raiso the water table at points down i-trcMni, an oxidized effluent at least would seem desirable, and it may be that disinfection with chlorine would also be advantageous In avoiding algal growths which might conceivably reduce the rate at which the sewage effluent could be applied to land. * * * i assume, however, that such border line cases as sewage effliu'ut discharged to coarse gravels with ground water near the surface and diversions within a few hundred yards down stream will not be tolerated. Washes having mixed materials, varying from boulders to tine sand with ground water hundreds of feet below afford ample opportunity for the influences of natural purification factors. * * * Drying is an effective means of purification. .\s ground water falls, both natural liltration through the soil and capillarity play an important part in removing pollution. This consideration indicates the advisability of intermittent dosing on spreading areas, at intervals, depending on the character of the ground (.!.-,, p. .7). Storage of water underground is an important feature of water conservation in southern California (.^.9). Nitrates in irrigation watei's were rei^orted upon in connection with the South Coastal Basin investigation in California hereinafter referred to in discussing salts in sewage effluents (p._40), one of the reasons being that nitrate is sometimes used as an indication of the contamination of water supplies by sewage effluents. The report states {il, p. 24) : It is to be ¡noted that nitrate occurs in relatively high concentrations in some of the underground waters of the South Coastal Basin. It is the writer's view that these high ccuicentrations should not be generally Interpreted as evidence of sewage contamination, or as the result of the accumulation of fertilizer residues from cultivated lands. Botli these sources may have contributed to some extent to the present condition but it is highly probable that they are both subordinate to other and natural conditicras not yet fully understood. SEWAGE IRRIGATION IN WESTERN STATES 37

SANITARY CONSIDERATIONS IN THE USE OF SLUDGE The use of sewage sludge for purposes of fertilization is incidental to the main question of sewage irrigation. However, it may have some effect upon the cost of sewage to farmers, as discussed herein- after (p. 53) ; therefore the sanitary features should be briefly indicated. A recent report of the committee on sewage disposal, American Public Health Association reviews the literature and current prac- tices in using sewage sludge as fertilizer alid advances the following conclusion as to the sanitary consideration {32, j>p. 908-909) : 17. From the hygienic standpoint, heat-dried activated sludge and heat-dried digested sludge appear safe for any reasonable use in agriculture or horticul- ture. Digested sludge, air-dried, appears safe for such purposes if used like manure and plowed In, when preparing for a crop, and if care is taken not to apply such sludge thereafter on root crops or low-lying leafy vegetables which are eaten uncooked. Thorough digestion and air-drying, as well as storage of the air-dried sludge, afford a sufficient protection. The Committee knows of no case of sickness traceable to the use of digested sludge or activated sludge. Fresh sludge should be regarded as only one degree removed from night soil and treated as such, being used only on forage crops and then applied and plowed in promptly thereafter. In making its recommendations, however, the committee stated that laboratory workers might well continue investigations toward ascer- taining more definitely the life history of pathogenic bacteria during sludge digestion alid the bacterial flora of various sludges.

CHARACTER OF PUBLIC REGULATION

INTEBSTATE QUARANTINE REGULATIONS Regulations promulgated by the Secretary of the Treasury pro- hibit the movement in interstate commerce of articles known to have been exposed to infection by certain disease organisms {■52). The Congressional act on which the regulations are based provides for enforcement by State and municipal authorities willing to undertake enforcement; otherwise by the President (t5ö). In at least one in- stance the United States Public Health Service has cooperated with State and local atithorities in correcting a situation in which vegetables shipped outside the State were being irrigated with water containing large quantities of untreated sewage. A treatment plant has since been installed in this community.

REGULATION BY STATE BODIES From the standpoint of the State, the primary function of the public-health bodies is to protect the public health—among other things, to control the processes of sewage disposal to that end. Regu- lation of sewage irrigation is a phase of this function. Where_ water is needed for crop irrigation, the concern of the State authorities is that the utilization of sewage in agriculture, while accomplishing dis- posal of the sewage, be carried out with full consideration for the public health. It will be noted from the summary hj States beginning on page 28, that the policies applying to sewage irrigation in some States involve public control by State officials, and elsewhere educational and ad- visory action but without enforcement of specific regulations. Many 38 TECHNICAL BULLETIN 675, U. S. DEPÏ. OF AGlilCULTURE

State officials in dealing with municipal authorities, even though possessing police power to stop a particular practice, prefer to use conciliatory methods if they can accomplish the desired result in that way. In certain instances State officials have found it necessary to step in and require the alteration or cessation of a particular sewage- irrigation practice that had been countenanced for years but that did not conform to standards which had come to be recognized as proper. With due regard for the economic consequences following an abrupt cessation of sewage irrigation in a particular community, and for the cost of treatment plants necessary for a continuance of irrigation, the State authorities on occasion have granted time within which to make the change. Insistence upon a new standard has re- sulted in certain cases in the construction of treatment plants from -which effluents meeting the State requirements are now available for irrigation. BEGULATION BY LOCAL AUTHORITIES City and county officials charged with maintenance of public health are close to the field of sewage-irrigation operations and are often in a better position to know what is going on than are the State authori- ties. In addition to their own police powers, the possibilities of cooperation with the State in regulating sewage-irrigation practices are important. The city is naturally the unit through which much of the control over sewage irrigation is eíTected. For example, the city has com- plete control over the use of sewage on its own sewage farm and can impose proper standards of use there at all times. The municipality retains indirect control over sewage farms or sewage effluents leased to individuals, through insertion in the leases of clauses providing for cancellation in the event designated practices are not followed. In either event it is the city with which State officials deal in case of noncompliance with State regulations. However, the municipality has no control over effluents released into public stream channels, excepting where the channel is used as a carrier for waters to which the city can retain legal title. The city's responsibility then is to produce an effluent conforming to the public standards for that type of sewage disposal; neither respon- sibility nor control extends to subsequent diversion and use of the effluent by individuals.

PK-i^OTICAL ACCOMPLISHMENT OF PITBLIC CONTROL A regulation promulgated by competent authority has a definite psychological value so long as kept before the attention of those whom it concerns. Beyond this, obviously, its value is limitedby the degree in which the regulation is enforced. Effective regulation, particularly where effluents are used by the general public, may require frequent inspections. This means adequate funds and per- sonnel in a State in which the practice is extensive. Where effluents not highly disinfected or otherwise treated for bacterial removal are to be released for general irrigation use, the practical problem of regulating the use naturally grows with extension of the irrigated area and increase in the number of individual irrigators. Coopera- SEWAGK IRRIGATION IX WESTERN STATES 39 tion between local and State authorities is distinctly valuable in such cases. The purpose of such inspections, of course, is to satisfy the health officer that the ii-riji;ation project is beinj; operated on a proper sani- tary basis. If, on a given project, the vulnerable points to which the inspector culls attention are promptly corrected, and it is obvious that o])eiiitions are being carried on properly, the need for frequent in- si)ections is minimized and the cost of supervision is correspondingly reduced. The chief of the California Bureau of Sanitary Engineer- ing has pointed out in a letter to the author the value of keeping certain records that would make available to the inspector and project management the history of operations. Such records would include information as to "the areas watered on given days, the crops irri- gated, (he use of other irrigation water and the different elements that go to make or break the project on sanitary grounds." Continuous chemical disinfection of an effluent released for irriga- tion of vegetables has its problems. Interruptions may occur in the chlorine suj)ply, and in operation of the chlorination apparatus; but tlie flow of sewage to the treatment plant continues. The California regulations provide that the apparatus and reserve supply of disin- fectant for each nuichine be in duplicate, where the effluent is to be used for such purpose. Should the interrujjtion be complete, the only ade- quate safeguard is to dispose of the effluent temporarily in such nianner as to cause no harm. In any event, it would appear that a continuous requisite is trained and conscientious operating personnel, not only at the start of a prograni when enthusiasm nnis high, but throughout the following years when operation has developed into a routine.^" What this meansis tliat complete reclamation of sewage—treatment to a point at which the effluent is approved by the State for use on any and all crops—reduces the need for control over sewage-irrigation practices, but increases the necessity for supervision over operation of the treat- ment plant which produces the effluent. Beyond all this, it is clearly to the interest of the user of effluent that the sewage treatment be continuously reliable and his own operations above suspicion, not only for the protection of his own health and that of the public, but to safeguard the market for his crops. If lapses occur and the ])ublic-health authorities find it necessary to take action, the economic basis of the project becomes precarious. SALTS IN SEWAGE EFFLUENTS The suitability of sewage effluents for irrigation, aside from patho- logical coTisiderations, depends on the chemical constituents of the mu- nicii)ality's water supply as affected by the addition of dissolved salts particularly those in industrial wastes entering the sewer system. Excessive salinity affects the growth of sensitive plants ; excessive pro- portions of sodium produce mifavorable soil conditions. Where the propoT'tions of salts in domestic sewage are increased as a result of in-

=" Snnitarv encineers have eriticizpd the inadequacy of operating attention received by iiian'v sowiiKe-ticatment plants. "DisiM>sal by irrigation or by spreading should be roiis'idi'rcd lust as important as any unit of the treatment plant. Too much attention hns lïeen given in the past to minute details of plant design and proposed quality of effluent under an assumed 100 percent efflcient operation, and too little to the fact that n many instances there may he times all too frequent when the plant fails to perform a part and in some cases all of its intended functions" (35, p. 6). See also W, p. Hi). 40 TECHNICAL BULLETIN 675, U. S. DEPT. OF AGRICULTURE dustrial wastes to a point at which the water becomes hazardous for irrigation use, there is no alternative other than to arrange for separate disposal of the industrial wastes if the effluent is to be devoted suc- cessfully to agricultural use. Analysis of the water supply of a Texas city which was forced to abandon sewage irrigation showed a high alkali content, rendering it unfit for agriculture in that locality; a better water supply has since been secured. The general subject of quality of water has been investigated and reported upon from time to time by technical workers of the United States Department of Agriculture and the University of California {7,21,23, 41, Jß, Iß, U). BORON Boron has been given particular attention in the California studies. This element, which is found in irrigation waters in some sections, is essential in some quantities "to the growth of many if not all plants," but "is extremely toxic to a large number of plants if present in the soil solution in concentrations above a few parts per million" {7,p. 1). Furthermore, according to the same authority, the amount of boron that different plants can withstand is widely variable; "irrigation water relatively high in boron may sometimes be used profitably for tolerant crops and be entirely unsuited for crops that are sensitive" (7, p. 8). Citrus trees, particularly lemons, and walnut trees are sensitive to boron. In the South Coastal Basin of California, experi- ence has shown that under existing climatic conditions the critical concentration of boron in irrigation water used for lemons and w^alnuts lies between 0.5 and 1.0 p.p.m. {41, p. 22). Waste from packing houses in which borax is used for washing fruit is a matter for inquiry if the boron content of the effluent runs high. Leaves of citrus trees irrigated with water contaminated with waste from packing houses showed more boron than the leaves of healthy trees {23). The sewage at Pomona several years ago was found to contain boron, attributed to packing-house waste. As the Pomona effluent is valuable for irrigation purposes, arrangements were made to dispose of this waste elsewhere than into the city sewer system. EFFLUENTS IN SOUTHERN CALIFORNIA Analyses of effluents from 10 sewage-treatment plants were made by the Bureau of Plant Industry, United States Department of Agri- culture, in cooperation with the Division of Water Kesources, Cali- fornia Department of Public Works, in connection with the South Coastal Basin investigation in California {J^l, 4^). There were in- cluded five cities from which the effluents are used for irrigation, four of the five being cases of irrigation directly from treatment plants at least in part. From 9 to 16 samples of effluent taken at different times were analyzed from each of four of these cities and 1 sample from the fifth city. The detailed analyses show specific electrical con- ductance, boron, percent sodium, bicarbonate radicle, chloride radicle, sulphate radicle, nitrate radicle, calcium, magnesium, and sodium. Referring solely to these fivii effluents, some of the results of particular interest m a discussion of sewage irrigation in that area are as follows : SEWAGE IRRIGATION IN WESTERN STATES 41

Most of the samples indicated boron concentrations well below the range of 0.5 to 1.0 p. p. m. considered critical for the more sensitive plants such as lemons and walnuts (.^7, f. 22) ; several were considerably higher. As to percent sodium (the quality of irrigation water taking into account the ratio of the sodium content to the sum of the calcium, magnesium, and sodium, the concentrations of all three constituents being expressed in terms of milligram equivalents per liter), the results from one city showed half the samples containing 60 percent or more and most of the remainder above 50 percent; the critical ratio is considered to lie between 50 and 60 percent (4^, V- 23). Samples from two other eflluents were largely at the critical range; in case of the two remaining cities, the effluent from one of which is used directly for irrigation and the other after discharge into a stream channel, the percentages were mostly on the safe side. Chlorides were well on the safe side. The sample of highest concentration showed 146 p. p. m. and the second highest 135 p. p. m. In respect to this constituent, it is stated that irrigation water in the South Coastal Basin has come to be accepted as safe if it con- tains less than 142 p. p. m., becoming increasingly hazardous as it approaches 355 p. p. m. {J^l, p. 23). The report of a study of avocado diseases by the University of California, in discussing tip- burUj says that in growing avocados about 100 p. p. m. of chlorine (equivalent to 165 p. p. m. of common salt) in irrigation water may be considered a danger line; but it also states that other conditions have much to do with tree injury by a specific concentration, tip- burn having appeared in some cases of the use of water with about 50 p. p. m. of chlorine, while in other cases good trees have been grown with water containing as much as 200 p. p. m. {21., p. 11). Specific electrical conductances (aggregate quantities of dissolved electrolytes) in nearly all cases were well below 100, only two sam- ples out of nine from one city exceeding this figure. Waters in this general area having conductances less than 100, if the boron concentration is below the limit of tolerance and the sodium per- centage less than CO, are considered safe for general use {U, p. 22). As the value exceeds 200 the water becomes increasingly hazardous for crop use. Concerning these relatively few analyses, as well as those of the other five effluents, it is stated : Such data as are available indicate tiiat tiie concentration and composition of the dissolved salts in sewage effluents are different not only from season to season throughout the year hut from hour to hour throughout the day (W

POSSIBLE EFFECT OF CHLORINATION UPON CHEMICAL QUALITY OF EFFLUENT FOR IRRIGATION Chlorine is the chemical commonly used to disinfect sewage efflu- ents. Not only does a high chloride concentration render water un- safe for irrigation use, as indicated heretofore, but free chlorine in even small quantities is well known to be toxic to plants with which it comes in contact. Inasmuch as the use of effluents unless highly dis- infected or filtered to a comparable degree does not meet the highest standards for vegetable irrigation, a question may be raised as to the 42 TECHNICAL BULLETIN 675, U. S. DEPT. OF AGRICULTURE effect of clilorination upon the chloride and chlorine content of the irrigation effluent. A few parts per million of free chlorine are commonly used to disinfect sewage effluents. The quantity of chlorine required for disinfection— is Influenced by the soluhTe organic and oxidiüable inorganic matter in the sewage. As the oxygen demand of the sewage increases, the chlorine demand likewise increases. The chlorine demand of the sewage must be satisfied before the slight excess (i. e., residual chlorine) becomes available to destroy the pathogenic organisms (8, p. 162^). The same authority states that with the appearance of the color in- dicative of residual chlorine by theorthotolidine test, the killing of 99.5 percent or more of the total bacteria and Bacillus coli is almost instantaneous {8, p. .1025). The quantities of available chlorine found necessary to secure effective disinfection (99 percent reduction of bacteria growing on gelatin) in fresh concentrated domestic .sew- age, not yet decomposed to any appreciable extent, in the Emscher district, Germany, in 1925, were 25 to 30 p. p. m. for crude, unclarified sewage, 15 to 2Ô p. p. m. for partially clarified sewage, and 10 to 15 p. p. m. for well clarified sewage {10, p. ,359). Quantities used in actual practice in case of effluents of high relative stability are often considerably lower. Concerning the chlorine residue, it has been stated that in general 0.5 to 1 p. p. m. residual chlorine after 10 minutes contact will give dependable disinfection, although lesser amounts may frequently suffice {10,f.35!i). CHLORIDES Chlorination of an effluent necessarily results, in satisfying the chlorine demand, in an addition to the chlorine compounds already present in the effluent, including the chlorides; however, the addi- tion is slight in case of an effluent of high relative stability, owing to the comparatively small quantities of chlorine required to satisfy (he chlorine demand. It follows that disinfection of such an effluent with chlorine might be hazardous from an agricultural standpoint if the effluent prior to chlorination already contained chlorides in concentrations closely approaching the danger line. The range be- tween the minimum and maximum concentrations of chloride con- stituting the danger zone is so broad, however, that the comparatively small addition resulting from chlorination would appear to be a minor consideration in appraising the hazard to agriculture from the standpoint of chlorides in the irrigation water. The effluents used for sewage irrigation which were sampled in the course of the South Coastal Basin investigation heretofore dis- cussed (p. 40) showed in nearly all cases chloride concentrations well below the lower limit for safe irrigation use (4^, pp. 126-126). Of 48 samples, only 8 showed more than 100 p. p. m. of chloride. Some of the effluents containing large quantities of industrial wastes and not used for irrigation ran much higher.

FREE CHLORINE The quantity of residual chlorine required to insure disinfection is very small, as noted above. Opportunities for reduction or elim- SEWAGE IRRIGATION IX WESTERN STATES 43 illation of free chlorine in the disinfected effluent are available during the period of flow through open ditches and furrows and the period of contact with the soil, all prior to contact with the plant roots. No experimental data on the hazard to plants under such conditions have come to tlie writer's attention; however, chlorinated effluents have been observed in use in several areas for irrigation of alfalfa and citrus and deciduous trees, without apparent injury to the plants. SEWAGE WATER RIGHTS The character of the water right is important in considering sewage irrigation. Sewage is one form of return flow after diversion of water for beneficial use {-'¡i). In some western jurisdictions an a|)propriator is permitted to reuse and recapture return water after it lias left liis own lands and before it enters a natural watercourse; in others he may not only do this, but under certain circumstances may redivert tlu^ return water from the stream into which it flows; ami in still others he may do neither. The rule in the last-named group is based upon public ownership of the return flow, and the otluM- rules recognize private ownership at least prior to the time of the coMuniiigliug with the flow in a natural stream. These rules are generally applicable to the ownership of sewage, although there are few State supreme court decisions in point. 'J'he Colorado Supreme Court held that the city of Trinidad had no property rights in its treated sewage, but must return any surplus miller its appropriative rights to tlie stream from which it was di\erted.-i The Wyoming Supreme Court held that the city of Cheyenne might discharge sewage into an irrigation ditch, under con- tiiict with the owner of the ditch, over the protest of appropriators on the stream from which the municipal water supply had been di- verted, as otherwise' tlie city would be hampered in its problem of sewage disposal ; but that the city had no further rights to sewage discharged directly into the stream.^^ The Superior Court of Walla Walla County. Wash., directed the city of Walla Walla to discharge llie effluent from a proi)osed treatment plant at a point at which it would be available to Irrigators who previously had been using the flow.-' In none of these instances did the court require an alteration in the method of sewage disposal on account of water rights claimed by other users; but in each case the city was required to satisfy existing rights where such course was consistent with the primary object of disposing of the sewage. iS'ew uses of sewage for irrigation before its discharge into stream channels will a{)parently be confined in large measure, from a water- right standpoint, to the sewage return from developed or from foreign water (water from other watersheds) in those States adopting the strict public-ownership theory; and in the other States, will probably be available in whatever degree the supreme courts of such States depart from this theory in their decisions on ownership of sewage p:ven in Colorado, which has gone further than any other State m

^Pulaxtí IrrUjating Ditch Co. v. City of Trinidad, 70 Colo. 565, 203 I'ac. 681 (Jan. 9, ^"'¿'wuomimi Hereford Ranch v. ITammoml Packing Co. et al., 33 Wyo. 14, 236 Pac. 764 **a?. S"v }fo»e'et al. v. City of Walla Walla, Superior Court, Walla Walla County, Wash., Case Í8888, decree dated March 23, 1027. 44 TECHNICAL BULLETIN 675, U. S. DEPÏ. OF AGRICULTURE considering return waters public, the supreme court has held that foreigfn water drained into a stream is not subject to prior appropria- tions from that stream.^* The legal restrictions upon reuse of sewage effluent by or undei- authority from the city will doubtless be less in the States which recognize deviations from the strict rule of public ownership than in those which adhere to it, particularly where the effluent is to be delivered to irrigators directly and not first discharged into a stream; for in some States, under such circumstances, con- tracts for the sale of waste water take precedence over the rights of appropriators not having such contracts (-?/, p. H6). Most of the decisions of courts of last resort on ownership of return waters have involved the return from appropriated water. Kiparian rights, in States which recognize the riparian doctrine, "are not of a political nature, but are private rights," and therefore in case of a municipality vest only in the ownership by such municipality of the abutting land.-= However, to the extent that a city may have a valid riparian right to use water for irrigation as well as domestic purposes on riparian land, no reason is apparent why the city could not reuse legally for irrigation on those riparian lands the sewage return from water diverted under such riparian right. Rights to the use of percolating ground waters rest upon the ap- propriation doctrine, the correlative doctrine, the doctrine of reason- able use, or the doctrine of absolute ownership, depending on the jurisdiction in which they occur {6). No Supreme Court decisions involving the right to reuse sewage from cities deriving their munici- pal water supplies from underground are known to the writer. Pre- sumably the right of reuse for irrigation, at least before discharge of tlie effluent into a natural watercourse on which water rights exist, would be governed by the limitations upon the right of use of the original water supplies.

ECONOMIC FEASIBILITY OF SEWAGE IRRIGATION Tlie foregoing discussion has shown that sewage irrigation is being practiced rather extensively in two Western States and in a few localities in the others. It also appears that the total quantities of water so utilized and areas of land so irrigated are small when compared with other irrigation uses, but that the practice is of eco- nomic importance in many localities, particularly m furnishing and utilizing supplemental water supplies. It is further brought out that sewage is a very special kind of water supply, with qualities so distinctive that its utilization is generally subject to restrictive laws or regulations and administrative supervision and requires more care on the part of the Irrigator than necessary in using ordinary water supplies; and that the standards imposed by public authority on sewage-irrigation practices have become increasingly strict. The present technique in distributing the water and applying it to the soil is shown to be much the same as that used for other water sup- plies in the same locality, with the difference that the excess of supply over demand has encouraged in some instances an unnecessarily lavish

** San Luis Valley Irrigation District v. Rio Grande Drainage District, 84 Colo. Oil, 208 Pac. 533 (May 28, 1928). » Town of Antioch v. Williams Irrigation District, 188 Cal. 451, 205 I'ac. 688 (Mar. 23, 1922). SEWAGE lUKIUAÏJON IN WESTERN STATES 45 use of the water witli some injurious effects. In other words, instead of increasiiij^ the care required for efficient irrigation with any kind of water, the tendency in various cases has been exactly the reverse.

EFFECT AND VALUE OF PAST AND PRESENT PRACTICES Irrigation has been of some economic value to mimicipalities that have enij)loyed it as a means of sewage disposal. Such value, on the whole, is less now than it was several decades ago, when it was cus- tomary to condone the use of untreated sewage in producing crops. Under any circumstances the economy of sewage disposal by irriga- tion depends upon whether the net cost of acquiring and operating farm land is less than tlie cost of treating the sewage for disposal elsewhere. Obviously, if there is no cost for treatment, the net ret urns from crojis are greater than if the effluent from a treatment plant is used for irrigation, other things being equal. However, un- secondary treatment were called to the writer's attention. The effluent which in one case was 46 TECHNICAL, BULLETIN 675, U. S. DEPT. OF AGRICULTURE charged with responsibihty for infestation of beef cattle, pasturing on irrigated land and drinking the effluent from the ditch (p. 34), was from a primary sedimentation unit. The widespread existence of typhoid in a western valley was attributed by medical authorities several years ago, to the use of stream water into which large quan- tities of raw sewage had been discharged. The possibility of epi- demics has caused public-health authorities to develop high stand- ards to which the treatment and utilization of sewage must conform if the practice is to continue.

ECONOMIC ASPECTS OP EXTENDING PRESENT PRACTICES

LIMITATIONS Several important limitations upon the probable extension of sew- age-irrigation practices follow.

QUANTITIKS OF WATEB AVAILABLE The quantity of effluent available for new or additional uses in most areas will be small. If the acre-for-acre ratio of municipal to irrigation use is taken as a guide—that is, the assumption that use of water by municipalities is approximately the same as irrigation use on equivalent land areas {25, p. 31)—the area capable of obtaining a full water supply from municipal sewage cannot be expected to exceed around two-thirds of the populated area contributing to the sewage. This ratio does not apply to all conditions, by any means, but is useful as a rough measure. Sewage from many of the larger cities in Western States, other than those bordering the Pacific Ocean, is already in use, either directly or by diversions from stream channels into which it is discharged. Supplies from the large Pacific coast cities are potentially available, but their use for irriga- tion depends upon major economic and other limitations, and there- fore does not ajjpear imminent. Hence the reasonable probability is that throngliout most of tlio AVest, such extensions as may take place in the near future will occur principally in communities surrounding the smaller cities and towns and with correspondingly smaller quan- tities of available effluent. This means that the outside estimate of additional use is the equivalent of a small area in each of a large number of communities. WATEK WGHTS An important limitation in some of the exclusively appropriation States is the prior chiim of downstream appropriators to the sewage flow. This does not ajijily, at least in Colorado, to the sewage return from nuniicipal water brought from a ditferent watershed. In other States tlie rule of public ownership of return waters is less rigidly applied and the limitation there will probably be less. (See the dis- cussion on p. 43 and folloAving.)

STATE SANITAKY KEGULATIONS Extensions of the practice will necessarily conform to the require- ments of public-health authorities. The importance of this limita- tion from the standpoint of the public welfare, and the growing con- SEWAGE IRRIGATION IN WESTERN STATES 47 sciousness of the necessity for high standards of pubhc sanitation, leave no doubt that the tendency will be to extend and increase the rigidity of public supervision where necessary; not to relax it. If this is correct, it follows that the practices will be brought more gen- erally under control and features considered objectionable eliminated. The reason for the current paucity or absence of restrictions in some of the States is that the practice is not general enough to create a problem; it does not mean that widespread practice would be un- restricted, extensions of present practices in such States, if made, will tend to create a problem or add to one already existing; and public regulations may be expected if the problem becomes serious. What this means, from an economic standpoint, is that extensions of sewage irrigation will tend to be limited to those communities in which effluents approved for irrigation use by public-health author- ities are produced, but tliat the opportunities for approved practices will grow with the development of reliable sewage treatment. A fur- ther implication is that extensions will be limited to the crops these authorities approve, which in some States even now will rule out many crops for human consumption unless the sewage treatment be complete and continuously reliable. In the absence of complete treatment, including disiTifection, which is expensive, the opportuni- ties for extension of sewage irrigation under public supervision will probably be limited principally to forage and textile crops and to some of the orchard crops.

COST TO THE IKKIOATOR The cost of water to the individual user of sewage has not been based on the cost of developing the water supply, and consequently has been a relatively unimportant consideration to him up to the present time. As shown below, in connection with ability of lands to pay for water, it is likely that some future uses of effluent will de]ien"d cm the ])ayment of substantial charges for tlie water. This will doubtless limit in some degree extensions of the practice; but inasmuch as there are now many existing plants from which the ef- fluents are not being used, and as the installation of new treatment plants, regardless of whether the effluent is to be utilized or not, may be expected in many localities, based on the present trend, it appears that the limiting effect of cost to the irrigator should be less than would be expected if new development of other water supplies were involved. It is believed that such extensions as take place m the near future will be on the basis of use from treatment plants then in operation, rather than as a consideration for the installation of the plant, and mainly in connection with general farm crops rather than hifi-h-priced food crops; under such circumstances the cost of water is not a serious impediment to the use of the effluent. Another lim- itin"- factor is the cost of applying the water to the land, which may be expected to exceed the iiormal cost of applying unpolluted water. These matters are discussed in more detail below. On the whole, the existence of an available supply of effluent will be in itself an inducement to its use on lands short of water, and the cost ele- ment while important, will probably not be the controlling factor in limiting use of the effluent. 48 TE

FIELDS IN WHICH EXTENSIONS AEE LIKELY TO OCCUR A strong likelihood exists that the use of sewage for irrigation, subject to certain limitations, will be extended from time to time. This is particularly true if the drought conditions prevailing during the past decade continue. The water shortage in 1934 was general and most acute, and several others while less widespread have been of distressing proportions. Furthermore, in various areas, insuffi- cient recharge of ground-water supplies from precipitation has in- creased the lag between recharge and effective utihzation, with re- sulting higher costs of pumping. Tlie result of such conditions is to induce agricultural communities to seek new sources of water supply ; and the utilization of sewage now going to waste has been proposed in a number of western localities.

SUPPLEMENTAL lERIGATION IN GENERAL FARMING AREAS Consideration of the various limiting factors upon the extension of sewage irrigation leads to the conclusion that extensions, while likely to occur, will be principally in the field of supplementing exist- ing supplies of water in irrigated general-farming areas, and in pro- viding water for irrigating crops for winter feed in dry-farmed areas, at least so far as the present outlook is concerned. In the usual case the effluent, from a quantitative standpoint, is better adapted to the demand for small quantities of Avater for auxiliary supply than to the principal requirements of an irrigation project. Furthermore, it is not often that plants for the complete reclamation of sewage are built; hence the effluent seldom meets the highest standards of public-health authorities for use in irrigating crops for human con- sumption, although it may be considered by them to be safe for forage crops under approved methods of irrigation, harvesting, and feeding. In that event the utility and value of the water for irri- gation purposes lie in a narrow field, but are definite within tliat field, hence it appears that supplemental irrigation is the field in which extensions in the near future are most generally to be expected. To the extent that the effluents in question are considered by com- jjetent authority as safe for irrigation use, they should serve a use- ful purpose in this field. Considering the character of sewage treat- ment, it is hardly likely that the charge for use of the effluent will exceed the ability of the lands to pay for it ; and the quantities of water so made available in most areas will be too inconsiderable to tempt overdevelopment. The economic effect of such extensions as do occur will be to increase to some extent the production of forage crops in areas having inadequate water supplies under normal con- ditions; and to make possible the maintenance of normal crop pro- duction in drought years in other areas. It is in this latter group that the greatest demand for additional small water supplies has been voiced, and it is there that the chief economic effect of exten- sions of the practice will probably be felt. A probable exception lies in some of the high-value orchard com- munities. Several cities put to considerable expense for sewage treatment have made arrangements in recent years for utilizing ef- SEWAGE lURIGATION IN WESTERN STATES 49 fluents approved by the State for orchard crops, or have negotiated for such use. This trend will probably continue, although extensive developments in the immediate future are not anticipated. Their economic effect will not be confined to agricultural areas, in the added supplies of irrigation water so acquired, as is mainly the case with supplemental irrigation in general-farming areas, but will be felt by the cities to the extent that the cost of sewage disposal is offset by revenue from sale of the water. Water supplies in areas of this char- acter have considerable value, and the ability of the lands to pay for water bears a closer relationship to the cost of sewage disposal than is usually the case in a general-farming community.

PBODIICriON OF CROPS FOR HUMAN CONSUMPTION The standards of health authorities, in States in which irrigation of fruits and vegetables with effluents has important public health and economic significance, are so high as to discourage the practice ex- cept under the most favorable circumstances. That is, only effluents that meet continuously a high standard as to bacterial content are sanctioned for such use, and fulfilling these requirements involves most difficult problems of design and operation. It is true that food crops of this cliaracter are being produced in a number of localities with effluents of poor quality; but it is equally true that such prac- tices cannot continue indefinitely and that their extension on any im- portant scale is most unlikely. Only practices that meet the highest standards may be expected to survive. Installation and operation of a treatment plant capable of produc- ing an effluent that meets continuously the public standards for the irrigation of any and all crops is probably impracticable for most small communities. Not only the initial cost, but the cost of opera- tion is laigh, owing partly to the imperative necessity for personnel adequate in training and numbers. Use of the effluent for crops bringing liigh returns may justify the project economically; this limits the project to favored localities. In most cases, even though economic feasibility be demonstrated mathematically, it is more than likely that the cost will appear to those responsible for authorizing the proposed expenditure out of proportion to the community's re- sources. It is therefore not likely that many small communities will embark upon enterprises of this character under prevailing eco- nomic conditions.

ABILITY OF FARM LANDS TO PAY FOR SEWAGE What lands can afford to pay for sewage depends, as in case of other irrigation water, on the returns from crop production after deducting costs of production (other than costs for water but includ- ing application of the water), operation and maintenance of irriga- tion works, general taxes, costs of family living, and amortization of farm indebtedness. Such permissible cost of water necessarily varies widely with the character and location of irrigable lands and the kind of crops to be irrigated, and obviously is influenced vitally by the agricultural economic situation prevailing during the period of payment. 50 TECHNICAL, BULLETIN 675, U. S. DEPÏ. OE"' AGRICULTURE

In a given area adapted to a wide range of crops, the selection of crops to be grown with sewage is governed by the character of the sewage available for irrigation as appraised by public-health authori- ties having administration over the practice. Wliere the range of adaptability to crops is wide, the character of available sewage sup- ply thus becomes a major limiting factor; it is an essential limiting factor whatever the range of crops. The charges individual farmers have actually been required to meet for the use of sewage water have usually been small; in fact, many such users pay nothing for the service because profit from sale of the water has not often influenced municipalities in planning their sewage-disposal works ; getting rid of the sewage has naturally been their primary consideration, and nearly always agricultural use has been secondary or wholly incidental from the city point of view. Thus in a large proportion of western areas in which sewage _ is used for irrigation, the cost of water has not yet become a major item. As most of the present farms are not far distant from the source of supply, transmission channels have not been generally expensive to construct. These farmers have taken the sewage as they found it, and where subject to public regulation in the use of sewage, they have made their crop selections accordingly. Access has thus been liad to a source of water supply in fairly close proximity, available at small cost. Doubtless comparable ac- cessibility will be extended to other areas in greater or less degree with the growing public consciousness of the desirability of proper sewage disposal.■■^"' If sewage must be treated before being released by a municipality, the cost of acquiring it for agricultural use is not necessarily based on the cost of treatment. Most experience to the present time sliows little or no relation between the two costs. However, the cost of sewage to the farmer for use in irrigating specific crops may bear a definite relation to the cost of treatment, if the processes required in making the effluent suitable for use in growing those crops involve expenditures greater than would be needed for an effluent prepared for disposal in some other manner consistent with public safety. In such cases, where the sewage has been already reclaimed to the extent required by health authorities for straight disposal, but not to the extent required by them for the irrigation of, say, vegetables and strawberries, it is reasonable to expect agriculture to pay any differential needed for additional treatment for use in growing these crops ; otherwise the incentive on the part of the city to provide this additional treatment is lacking. For example, the lessee of a sewage farm in southern California agreed to pay a specific rental for the land and one-half of the effluent, which at the time of signing the lease conformed to the State requirements for use in irrigating alfalfa; and agreed to pay a rental about 56 percent higher whenever the effluent should be

2*'Data compilefl by Ihe National Resources Committee indicate tlie construction of 83r) new sowase treatment plants in the united States from 1932 to early 19H7, with tributary iiopulatlon estimated at 14,984,000. Of this number 720 new plants, with tribu- tary population 14,196,000, were constructed with Federal assistance. About three-fifths of the new plants include both primary and secondary treatment (SI, p. 7). It is further reported that the total number of sewage-treatment plants in incorporated places in 1937 approximated 3,700, serving a population of 35,200,000 (51, p. i). SEWAGE IRRIGATION IN WESTERN STATES 5I sufficiently purified to be suitable for irrigating truck and similar products. (The required degree of purification has not yet been at- tained.) The value of the additional rental was estimated, on the one hand, to cover the cost of further treatment for complete dis- infection, and on the other hand, to be justified by the greater net returns expected from truck gardening over those from alfalfa pro- duction. Reference has been made heretofore to Pomona, Calif., where anticipated revenue from irrigation use was a factor in the plan of sewage treatment, and where an irrigation company has acquired the exclusive right to the continuously chlorinated effluent from an activated-sludge plant, at substantial compensation, for use in irrigating orchards. The cost of effluents for future irrigation, in areas in which the sewage is not now reclaimed, will doubtless vary from nothing to a substantial percentage of the cost of reclaiming the sewage. It is reasonable to anticipate that the actual charges in a given case will be influenced, on the one hand, by estimates of the ability of the farm lands to pay for the water, and on the other hand, by whatever pressure may be exerted at the time upon the city to clean up its sewage. Requiring the irrigated lands to pay a large part of the cost of sewage reclamation would appear far less likely if public opinion or insistence by State public-health authorities were then di- recting a city to build a treatment plant, than if the incentive resulted princi])ally from demands by farmers for irrigation water. Experience in irrigation agriculture shows that ability to pay for water has often been overestimated. Illustrations are not needed to show how widespread this condition has been, in good times as well as bad, and wliat large losses have been sustained by investors in se- curities of many irrigation projects throughout tlie West, owing to one cause or another. Nevertheless, it is equally true that good irri- gated lands have made large aggregate payments for water overa series of years. Pcesent technique is adequate for estimating, within reasonable limits, the probable ability of lands to pay for water. If this estimate is made carefully and conservatively at the outset of a sewage-irrigation project, the probability of default in making the payments is lessened. in estimating ability to pay for sewage, there are certain matters in connection with distributing and applying water that differ from those on an ordinary irrigation project and therefore should not be overlooked. It has'been shown in discussing this subject (p. 14), that in conveying sewage in public places the use of underground pipe or covered surface conduits is needed for protection; that entirely separate distribution systems for effluents and unpolluted water are necessary where water of both kinds is used in the same area ; that the amount of ditch cleaning necessary is measurably in- creased in sewage-irrigation areas; and that preparation of the land for irrigation requires more care and expense than under ordinary conditions. This means comparably higher capital and operation costs for the use of sewage, both on the system distributing water to the farmers and on the individual farms. The tendency toward stringent public supervision means that the prospective user of effluent cannot afford to scale down his estimate on the assumption 52 TECHNICAL, BULLETIN 675, U. S. DEPT. OP AGRICULTURE

that any kind of practice will do for sewage irrigation, but on the contrary must increase it to meet the public standards to which he must adhere. The estimate of cost of a distribution system, where a number of users is involved, must be based on entirely new construction or on acquisition of works no longer used for other irrigation water. Public-health authorities consider that the use of any part of a sewage-distribution system for conveying water that must be kept un- polluted is hazardous. This negatives any idea of a dual-purpose canal, for conveying sewage and unpolluted water either simul- taneously or alternately to respective irrigated areas; or of any point of contact between the sewage-distribution system and the system for clean water, other than a channel for the purpose of adding dilution water to the sewage under such hydraulic conditions as will prevent backflow of the sewage. In other words, to conform to these stand- ards, a project for furnishing effluent to various parts of an already irrigated area must provide a duplicate irrigation system. Citrus growers in southern California pay annual charges for water which in recent years have ranged from $5 to $80 per acre, or from $2 or $3 to $40 per acre-foot. Over the 15-year period ended with 1984, the annual operating expenditures of nine mutual companies in that area ranged from about $4 to $55 per acre, the individual water users in many cases having expended additional sums to get the water to their land and in some instances for auxiliary supplies. These expenditures do not include new construction or acquisitions. On the other hand, annual charges for water for general crops in many regions are found to range from $1 or $2 to $10 per acre ; and unless exceptionally high returns from crops are assured or other exception- ally favorable conditions obtain, experience indicates tliat it is not gen- erally safe to predicate construction of irrigation works in a general- farming area on annual payments exceeding $10 per acre. Too many projects have proved unable to carry substantially higher charges, owing to one cause or another. The supply of effluent is rather constant even in drought years and therefore more dependable than ordinary irrigation supplies from other sources. The value for crop production is apparently equal to that of other water. Users can afford to pay the same charges for the effluent as they would for stream water, minus the differential incidental to applying the sewage. Hence in an area in which liigh- return crops are produced, they can afford to pay a substantial part of the cost of so processing the sewage as to make it conform to the State sanitary requirements for such use. Where general farming is practiced, it appears that they cannot generally do this ; and theii- economic ability to acquire a water supply from such source ^yill probably depend in many cases on the fact that the sewage is being treated or will be treated by the city without regard to its possible USB for irrigation, or at least that the installation of the treatment plant is not contingent upon repayment by irrigated lands of the cost of a high degree of refinement.

RETURNS FROM MUNICIPAL SEWAGE FARMS The operation of a municipal sewage farm presents a somewhat different financial problem from that of an individual sewage-irri- SEWAGE IKIUGATION IN WESTERN STATES 53 fiated farm. The major consideration here is not so much the relation of cost of water to net returns from farm operations; rather, it is the t'tfect of net farm returns upon the cost of sewage disposal. Financial statements of several municipal sewage farms were ob- tained in the course of the present study, but not in sufficient detail to indicate the true financial status of sewage farms. Considering only the actual fai-m receipts and disbursements, some show substan- tial ])rofits in certain years and substantial losses in others; if inter- est on the investment and taxes on the portion of the land devoted to farming are added to the disbursements some of the favorable bal- ances disappear. Whether it is proper to consider these overhead cliarges in judging the success of the sewage farm depends upon the part j)layed by the farm in the plan of sewage disposal. Operation of the sewage farm at a deficit would be justifiable from the standpoint of cost of sewage disposal, so long as the deficit did not exceed the charges on such additional treatment of the sewage as would be necessary for its dis|)osal into a watercourse ; and any favor- able return would be an offset against the cost of disposal. If the requirements as to character of the sewage to be used in irrigation are the same as for disposal into a stream channel, operation of the sewage farm is no longer a matter of sewage disposal but becomes distinctly a farming enterprise and is of value to the city only if carried on at a profit. Other circumstances may make sewage farming economically de- sirable irrespective of overhead charges; for example, the utilization of city-owned land. The present study disclosed cases in which cities were obliged to acquire more land than needed for sewage-treatment j)lants, either to forestall objections from neighboring landowners, or because the quickest and least expensive way to obtain a particu- lar site was to purchase the entire tract of which it formed a part. Interest and taxes on land necessarily acquired for other reasons are not proper items for consideration in determining the economic feasi- bility of using that land for sewage farming, if such operation is the most practicable means of utilizing it.

USE AND SALE OF SLUDGE Sludge, a necessary byproduct of sewage-treatment plants of var- ious types, lias in various places a commercial value which appar- ently has little or no bearing upon the cost of water to Irrigators at present but may have eventually. The value of the sludge depends on its usefulness for fertilization purposes and upon the demand from users to whom it may be trans- ported economically. The range in utility and value is considerable, depending on the type of sludge." For example, the city of Pasa-

se The committpe invesHgaling the utilization of sewage sludge as iertilizer (M), above referred to (t) »"). concluded that heat-dried activated sludge is of value for its organic nitrogen and phosphoric acid content as well as humus, and its effect as a conditioner in mix«! fertilizers, and with suitable nitrogen content may justify a rail haul of 1,000 miles or less It was also concluded that digeste

SUMMARY Sewage is looked on as an asset in various areas because of its possible use as a supplemental irrigation water supply. Sewage irrigation, from the standpoint of western agriculture, is a corollary of sewage disposfd. It is not synonymous with sewage disposal. Therefore, irrigation with this particular water supply, in areas in which irrigation is important or essential to agriculture, is an agricultural problem. Sewage is being diverted from outfall lines or treatment plants and used for the irrigation of crops in 102 western communities in- cluded in the present study. With several important exceptions, sew- age from the largest western cities is not now being diverted directly for irrigation. In practically three-fourths of the cases included in the study, crop irrigation has been incidental to the disposal of the sewage. This use of sewage in some areas has been discontinued for various reasons. In 18 comnumities in the study, sewage is diverted from public stream channels into which it has been discharged from outfalls and treatment plants. Irrigation ditches in many western areas divert from streams which carry sewage in varying degrees of initial treat- ment and subsequent stream dilution. Present uses of sewage for irrigation by individuals are largely supplemental ; that is, in many cases they augment other water sup- plies. Practices in applying the water conform generally to preva- lent local standards, although some unnecessarily lavish uses were observed. Areas now irrigated with sewage taken directly from out- falls or treatment plants range from 1 or 2 acres to several thous- and, the most extensive area of direct application being at San Antonio, Tex. In 46 connnunities the sole use of sewage for irrigation is by indi- vidual farmers. In 67 communities there are municipal sewage

2** According to data presented in the committee report (32). above referred to, sales of heat-dried activated sludge b.v Pasadena over the tx'riod l»29-:i6 averaged ,'i.238 tons per annum ; hy Houston over the period 19.32-36, 2,002 tons per annum ; and by Milwaukee over the period 1927-36, 32,093 tons per annum. SIOWAGK IKUIGAÏION IN WESTERN STATES 55 farms; the, snrphis effluent above the needs of 25 such farms is used by neifihborinfj; farmers who receive it directly from the disposal plant or sewafje farm. The municipal sewaf^e farm is less of a factor in utilization of sewage than formerly, but is still important from an agricultural standpoint. Coarse-textured soils, loose in structure, have proved better suited to sewage irrigation than heavy soils of equivalent fertility but many tracts irrigated with effluents consist of clay loams and clays. Dif- ficulties with the heavy soils irrigated with effluents have arisen largely from lack of care and judgment in applying the water, rather (han from the character of the water. The coarser-textured, lighter soils comprise two-thirds of the soil classes in the areas included in the study. Any change resulting from the use of sewage so far as reported, was to the effect that the soil structure showed improvement. Considering 85 separate areas in the West in which sewage irrigation is being practiced, the maximum period of substantially continuous use of sewage (treated or untreated) is approximately 49 years, with an average of 15 yeai"s. Crops irrigated with sewage are those commonly grown under ir- rigation in the locality. Reports generally indicate higher yields with sewage effluents than with other water applied under com- j)arable physical conditions and witli equal care. Small grain (in- cluding field corn) is grown in the largest number of localities, fol- lowed by alfalfa. Orchard trees and vines, vegetables, pasture, and a group of miscellaneous crops (led by grasses and cotton) are grown with sewage in many localities. The sewage used "in nine-tenths of the localities in the study now receives some pretreatment. In a few cases raw sewage is diverted from outfall lines above treatment plants and used for irrigating vegetables and other crops. Several of the "Western States, particularly those in which sewage irrigation is important, have formulated policies for the regulation or guidance of sucli practices. In some States public control is exer- cised by State officials, and in others, educational and advisory action is taken but without enforcement of specific regulations. City and county officials have certain powers in controlling sewage-irr^ation practices, independently or in cooperation with the State. Effective regulation, where the irrigated area is extensive and the Irrigators are numerous, may require frequent inspections. The complete rec- lamation of sewage to a point at which the effluent is suitable for use on any and all crops eliminates the necessity for control over its use, but increases the necessity for supervision over operation of the plant which produces the effluent. The tendency of regulatory bodies is toward increasingly high standards of use of effluents in irrigation. The possibility of polluting ground waters by extensive applica- tions of sewage under favorable conditions may be inferred from ihe findings of several investigators. The spread of pollution, and the limits of spread under conditions in which the experiments were con- ducted have been demonstrated. The quantity of initial pollution, character of the soil, and location and direction of flow of the ground water appear to be the important factors. Where effluents have been i-endered safe this danger is removed and the effluents become available for augmenting underground water supplies for subsequent use. 56 TECHNICAL BULLETIN 675, U. S. DEPT. OF AGRICULTUKK

The suitability of effluents for irrigation depends on the chemical as well as the bacterial constituents. Excessive salinity affects the growth of sensitive plants; excessive proportions of sodium produce unfavorable soil conditions. Small quantities of boron are toxic to many plants, and have given concern in some sections in southern California. Wliere the proportions of salts in a municipal water supply are increased as a result of industrial wastes to a point at which the water becomes hazardous for irrigation, separate disposal of the industrial wastes is necessary if the effluent from the domestic sewage is to be used on crops. Sewage is one form of return flow after diversion of water for beneficial use. The courts in some States adhere to the public-own- ership theory of return flow, which means that return waters from irrigation (unless appropriated from a different watershed from that in which the water is put to use) are not the private property of tlie appropriator; while those in other States have sanctioned the ap- propriator's right to recapture return flow under certain circum- stances. So far as municipal waters a[)propriated from streams in the public-ownership States are concerned, it would appear that new uses of sewage from sucli municipalities for irrigation, before being discharged into stream channels, will be largely confined to the sewage return from water brought by the cities from other watersheds. Such extensions of sewage irrigation practices as may occur within the near future are expected to be in the field of supplemental irri- gation, although some new enterprises in orchard areas are probable. Important limitations on the extension of these practices are the small quantities of water tlms made available, the effect of rights of existing appropriators on streams into which sewage is now being discharged, the restrictions of State public-health autliorities on the character of effluent which may be used for specific crops, the higli cost of so treating an effluent as to make it available for all crops, and ability of lands to pay for the water. The cost of sewage to individual farmers so far has usually been low. However, the cost of sewage to farmers for irrigating crops which require treatment of the effluent beyond that now required of the city under public-health laws will doubtless involve payments by the farmers for part or all the cost of the added treatment. The cost of effluents for future irrigation, in areas in which the sewage is not now reclaimed, will doubtless vary from nothing to a substan- tial percentage of the cost of reclaiming the sewage. It is reasonable to anticipate that the actual charges in a given case will be influ- enced on the one hand by estimates of the ability of the farm lands to pay for the water, and on the other hand by whatever pressure may be exerted at that time upon the city to treat its sewage.

LITERATURE CITED (1) ANONYMOUS. 1931. HELP FOR WATLAT SHORTAGE MAY IJE IN KECLAIMING SEWAGE WA.STE. Calif. Citrogr. 16: 498, 538-539, illus. (2) AMBaticAN SOCIETY OF CIVIL ENOINEEBS and AMEIKICAN PUBLIC HEALTH ASSOCIATION. 1928. DEFINITIONS OF TEKMS USED IN .SEWEBAGE AND SEWAGE DISPOSAL PRACTICE, ADOPTED BY THE AMERICAN SOCIBH'Y OF CIVIL BNGINEEKS JULY 10, 1028, AMERICAN PUBLIC HEALTH ASSOCIATION OCTOBER 20, 1927. Amer. Soc. Civ. Engin. Manuals of Engineering Practice No. 2, 19 pp. New York. SEWAGK IRRIGATION IN WESTERN STATES 57

(3) BEARD, PAUL J., CARLSON, J. M., and CHAMBERS, R. D. 1937. THE SURVIVAL OF EBERTHELLA ÏYPHOSA IN SOIL. JOUr. Bact. 33: 74-75. (4) and MEADOWOROFT, NIEL P. 1935. SURVIVAL AND BATE OF DEATH OF INTESTINAL BACTERIA IN SEA WATER. Amer. Jour. Pub. Health 25: 1023-1026, lllus. (5) CONKLINO, HAROLD. 1937. ADMINISTRATIVE CONTROL OF UNDERGROUND WATER : PHYSICAL AND LKOAL ASPECTS. Amer. Soc. Civ. Engin. Trans. 102 [753]-784. Discussion, pp. 785-837. (6) DAPPERT, ANSELMO F. 1932. TRi\CINO THE TRAVEL AND CHANGES IN COMPOSITION OF UNDERGROUND POLLUTION. Water Worlds and Sewerage 79 : [265]-269, illus. (7) EATON, FRANK M. 1935. BORON IN SOILS AND IRRIGATION WATERS AND ITS EJ-FECT ON PLANTS, WITH PARTICULAR REFERENCE TO THE SAN JOAQUíN VALLEY CE CALIFORNIA. U. S. Dept. Agr. Tecli. Bull. 448, 132 pp., illus. (8) ENSLOW, L. H. 1927. RECENT DEVELOPMENTS IN SEWAGE CHLORINATION. Pub. Health ReptS [U. S.] 42: 1023-1042. [Also Pub. Health Serv., Reprint No. 1105.] (9) FROEHDF, F. C. 1931). HOW POMONA MAKES MONEY SELLING SEWAGE EFFLUENT FOR IRRIGATION VSK. West. City 6: 39-10. 49, .')2, illus. (10) B^iLLEK, GEORGE W., and MOCLINTOOK, JAMES R. 1926. SOLVING SEWAGE PROBLEMS. 548 pp., illus. New York. ( 11 ) WHIPPIJ:, G. C, and MULHOIX.äND, W. 1921. REPORT OF THE SPECIAL SEWAGE DISPOSAL COMMISSION. 31 pp. LoS Angeles. <12) GORMAN, ARTHUB E. 1930. WATIOR-BORNE OUTBRE.VKS DUE TO POIXUTION OF GROUND WATER SUP- piJES. Mo. Water and Sewerage Conf. Ann. Rept. 6: 45-51. (13) CHASE, E. SHbaiMAN, FREEBURN, H. M., HUTTON, H. S., DAPPERT, A. F., and (!OUDI::Y. It. F. 1938. WATER-BORNE OtITBRI-:AK8 IN THE UNITED STATES AND CANADA 1930- 1ÎKÎ0 AND niEiR SIGNIFICANCE. Amer. Pub. Health Assoc. Ann. Yearbook (1937-38) 8: 137-156. (Sup. to Amer. Jour. Pub. Hciilth, v. 28, No. 2, pp. 137-156. 1938.) (14) GOUDEY, K. F. 1931. PL.\NS FOB SEWAGE RECIJIMATION IN THE LOS ANGELES METROPOLITAN AREA. Engin. News-Rec. 106: 443-446, illus. (15) 1931. SOME OPBHiATION RESIILTS, 1X)S ANGELES SEWAGE RECLAMATION PLANT. Sewage Works Jour. 3: 214-222, illus. (16) GREEN, C. E., and BEARD, P. J. 1938. THE SURVIVAL OF E. TYPHI IN SEWAGE TREATMENT PLANT PROCESSES. Anier. Jour. I'ub. Health 28: 762-770. (17) HARDING, S. T. 1936. WATFUT RIGHTS FOB IRMGATION ; PRINCIPLES AND PBOCEDUBE POB ENGI- NEERS. 176 pp. Stanford University, Calif. (18) IIEUKET.EKIAN-, H. 1927. THE FATE OF B. OOLI AND B. AEB0GENK8 IN SEWAGE PURIFICATION. Joiir. Bact. 14: .5,5-67. (19) and SCHULHOIT, H. B. 1935. STuniiîS ON THE SIUWIVAL OF B. TYPHOSUS IN SURFACE WATERS AND SEWAGE. N. J. Agr. Expt. Sta. Bull. 589, 32 pp., illus. (20) Hoo\'BR, C. B. 1937. SOME IMPRESSIONS OF SEWAGE DISPOSAL IN GERMANY. Ohio Conf. on Sewage Treatment Ann. Repts. 7-8: 36-45. (21) HOBNE, W. T. 1934. AVOCABO DISEASES IN CALIFORNIA. Calif. Agr. Expt. sta. Bull. .585, 72 pp., Illus. (22) HUTfrHiNS, WfXLS A. 1931 POLICIES GOVERNING THE OWNERSHIP OF RETURN WATERS FEOM IRRI- GATION. U. S. Dept. Agr. Tech. Bull. 439, 48 pp., illus. 5g 'rK(]HNI(;AL BULLETIN 675, U. S. DEPT. OF AGRICULTUUK

(23) KEIXEY, W. P., and BBOWN, S. M. 1928. BOEÎ)N IN THE BOILS AND IREIQATION WATERS OF SOUTHERN CAUTOENIA AND ITS RELATION lO CITRX'S AND WALNUT CULTUBT:. Hilgilrdia 3: 445-458. (24) KLIGLEK, I. J. 1921. INVESTIGATION ON SOIL POLLUTION AND THE RELATION OF THE VARIOUS TYPES or PRIVIEB TO THE SPREAD OP INTESTINAL INFECTIONS. Rocke- feller Inst. Meil. Research Moiiog. 15, 75 pp., illus. (25) Los ANGELES BOARD or PUBIJC SERVICE COMMISSIONERS. 1916. COMPIJ';TE REPORT ON a)NSTRucTioN OF THE LOS ANGELES AQUEDUCT; WITH INTRODUCTORY HISTORICAL SKETCH . . . 319 pp., iUuS. Los Angeles. (26) Los ANGEILES SEWAGE DISPOSAL COMMITTEE. 1921. REPORT OP ENGINEERS REGARDING THE DISPOSAL OP SEWAGE OF THE CITY OF LOS ANGELES, CALIFORNIA. Book No. 2, 51 pp., UIuS. LoS Angeles. (27) MiTCHiiLL, GEX)ROE A. 1931. OBSEasvATiONS ON SEJWAfiEl FARMING IN EUROPE. Kngiu. News-Eec. 106; 66-69, lllus. (28) ■ 1937. MUNICIPAL SEWAGE IRRIGATION. Englii. News-Rec. 119: 63-66. (29) MiTOHELsoN, A. T., and MUCKFX, DEIAN C. 1937. SPREADING WATER FOR STORAGE UNDERGROUND. U. S. Dept. Agr. Tech. Bull. 578, 80 pp., lllus. (30) MUBGGE, O. J. 1934. DEVELOPMENT OF SAFE GROUND WATER SUPPLIES. Johnson Nati. Drill- ers' Jour. June-July 1934: 4-5. (31) PASADENA [CALIF.] CITY AUDITOR. 1912-13. ANNUAL REPORTS . . . Flscal years ending June 30, 1912, and June 30, 1913. (32) PE.\ESB„ LANGDON, chairman. 1937. THE UTILIZATION OF SEWAGE SLUDGE AS FEBTILIZEB. ScWage WorkS Jour. 9: 861-912. (33) RAFTER, GEORGEI W. 1899. SEWAGE IRRIGATION, PART II. U. S. Geol. Survey Water-Supply and Irrigation Paper 22, 100 pp., illus. (34) RAWN, A. M., chairman. 19S4. SALVAOEJ OF SEWAGE STUDIED. Civ. Engin. 4: 471-472. (35) REINKE, E. A. 1931. GBNElIli\L, CONSIDERATIONS IN DETERMINING STANDARDS OF RECLAIMED SEWAGE FOB VARIOUS USES. Amer. Soc. Civ. Engin. 4 (1) : 4-6. (36) RHINES, CHESTER. 1985. THE PESiSISTBNCE OF AVIAN TUBEStCLE BACILLI IN SOIL AND IfT ASSO- CIATION WITH SOIL MICRO-ORGANISMS. Jour. Bact. 29: 299-311. (37) 1935. THE LONOmiTY OF TUBEIBCLB BACILLI IN SEWAGE AND STREIAM-WATER. Amer. Rev. Tiiberc. 31: 49^-497. (38) RoBCHLiNG, HERMAN ALFRED. 1892. THE SEWAGE FARMS OF BERLIN. Inst. Civ. Engin. Minutes Proc. (1981-92)109:179-228. No. 2570. Discussion, pp. 229-268, illus. (39) RUCHHOFT, C. C. 1934. STUDIES ON THE LONGEVITY OF BACILLUS TYPHOSUS (BBERTHEXLA TYPHi) IN SEWAGE SLUDGE. Sewage Works Jour. 6: 1054-1067, lllus. (40) RUTHS, H. 1928. B-üNFZIO JAHRE BERLINER 8TADT0üTBB (FIFTY YEARS OF BERLIN CITY FARMS). 60 pp., illus. Berlin. (41) ScoFiBLD, CARL S. 1933. QUAUTY or IRRIGATION WATERS, SOUTH COASTAL BASIN INVESTIGATION. Calif. Dept. Pub. Works, Div. Water Resources Bull. 40, 95 pp., illus. (42) 1933. DETAILED ANALYSES SHOWING QUALITY OF IKMGATION WATERS (SUP- PLEMENTAL TO BULLEJTIN NO. 40). SOUTH COASTAL BASIN INVESTIGA- TION. Calif. Dept. Pub. Works, Div. Water Resources Bull. 40-A, 131 pp., illus. SEWAGE IKIiKÎATION IN WESTERN STATES 59

(43) SCOPIELD, CAFI. S., 011(1 HEADLEY, I'EANK B. 3921. QUAUTY OF IRRIGATION WATER IN REI^TION TO LAND BECI^MATION. Jour. Agr. Itesearch 21: 265-278. (44) and WiLCOx, L. V. 19;il. BOBON IN IRRIGATION WATERS. U. S. Dept. Agr. Tech. Bull. 264, 6(> pp., illus. (45) SMITH, G. B. I*. 1928. BROAD IRRIGATION WITH SEWAGE. Arlz. State Bd. Health Bull. July 1928: 4(>-4;i. (46) STII.ES, C. W., CROHURST, H. R., and THOMPSON, GORDON B. 1927. EXPEIilMKNTAI, BACTEBIAL AND CHEMICAL POLLUTION OP WELLS VIA GROUND WATER, AND THE FACTORS INVOLVED. U. S. Pub. Health Serv., Hyg. Lab. Bull. 147: 1-136, Ulus. (47) STOKES, W. B., LKUKEI., W. A., and BAKNETTE, R. M. 1930. EFFEC;TS OF IKRIGATION WITH SEWAGE EFFLUENT ON THE TIELDS AND ESTABUSHMENT OF NAPIER GRASS AND JAPANESE CANE. Pia. Agr. Expt. Sta. Bull. 215, 18 pp. (48) STRAHOBN, A. T.J NELSON, J. W., HOLMES, L. C, and BCKMAN, B. C. 1915. SOIL SURVEY OF THE FRESNO AREA, CAUF0RNIA. U. S. Bur. SollS, Field Oper. 1912, Rept. 14:2089-2166, illus. (49) SUBRAHMANYAN, V. 1932. SEWAGE FARMING IN INDIA. Current Sei. [India] 1:157-160. [Sum- marized in Bxpt. Sta. Rec., 70:252. 1934.] (.50) UNITED STATES LAWS. STATUTES, ETC. 1893. AN ACT GR.\NTlN(i ADDITIONAL QUARANTINE POWERS AND IMPOSING ADDITIONAL DUTIES UPON THE MARINE-HOSPITAL SERVICE. Ü. S. Statutes at Large, v. 27, Ch. 114, pp. 449-452. (52d Cong., 2d sess. ). (51) [UNITED STATES] NATIONAL RESOURCES COMMITTEE, WATER RESOURCES COMMITTEE. 1937. SECOND REPORT OF THE SPECIAL ADVISORY COMMITTEE ON WATER POLLU- TION AND SUMMARY OF STATE LEGISL.\TION AFFECTING WATER POLLUTION. (Appendixes to report of hearings by Rivers and Harbors Committee on H. R. 2711, H. R. 2300, and H. R. 3419.) (52) UNITED STATES PUBLIC HEALTH SERVICE. 1921. INTERSTATE QUARANTINE REGULATIONS OF THE UNITED STATES. REV. ed., 40 pp. APPENDIX LIST OF AREAS INCLUDED IN STUDY IN WHICH SEWAGE WAS BEING USED FOR CROP IRRIGATION IN 1934 OR 1937, OR BOTH

IRRIGATION WITH SEWAGE TAKEK DIRECTLY FROM OUTFALLS OR DISPOSAL PLANTS Arizona : Casa Grande, Nogales, Phoenix,'" Tucson. California : Bakersfleld, Banning, Chino, Cloverdale, Colfax, Colton, Corcoran, Dixon, Elsinore, Exeter, Fowler, Fresno, Hanford, Hemet, Indio, Kingsliurg, Lemoore, Livermore, Lodi,'" Madera, Manteca, Marysville, Merced, Modesto, Ontario, Orland, I'asadena, Pomona, Ripon, Riverside, San Luis Obispo, Santa Maria, Santa I'aula, Santa Rosa, Selma, Sonoma, St. Helena, Susanville, ïulare, Turloclí, Ukiah, Vacaviile, Visalia, Wasco,""^ Whittier, Woodland, Yrelta. Colorado : Greeley. Idaho : Glenns Ferry, Äleridian. Kansas : Liberal, Scott City. Montana : Anaconda, Helena, White Sulphur Springs. New Mexico : Clovis, Portales, Santa Fe. Oregon : Ashland, Burns. Texas: Abilene, Amarillo, Baird, Breckenridge, Brownfleld, Canyon, Carlsbad (State Sanitarium), Chlldress, Coleman. Dublin, Falfurrias," Georgetown, Karnes City, Kerrville, Kingsville, Lubbock, Midland, Mission, Munday, I'lain- view, Robstown, Roscoe, Rotan, San Angelo, San Antonio, San Marcos (irriga- tion with sludge), Snyder, Stamford, Stephenville, Sweetwater, Tahoka, Uvalde. Utah : Brighara, Richfield, Salt Lake City, St. George. Washington : Pomeroy, Walla Walla. Wyoming: Cheyenne.

IRRIGATION WITH SEWAGE DIVERTED FROM PUBLIC STREAM CHANNELS Arizona : I'hocnix. California : Brea, Pasadena, San Bernardino, Santa Rosa, Tracy. Colorado : Denver, (Jreeley. Nebraska : Hastings. Nevada : Reno. New Mexico : Ra ton. Oregon : Aslilaiid, Medford. South Dakota ; Rapid City. Texas : Sim Angelo. Utah : Ogden. Washington : Walla Walla. Wyoming : Cheyenne. 2" Direct irrigation only on park surrounding plant ; not oon-iidered in total Asures. ^ BfHuent taken diredl.v into irrigation district canal. ^ Creamery waste only, 22 Sewage irrigation previously practiced and abandoned, just now being resumed. 60

U.S. GOVERNMENT PRINTING OFFICE: 1939

For sale by the Superintendent of Documents, Washington, D. C. . - - - Price 5 cents