(118) a Procedure for Evaluating Environmental Impact

7/28/2019 (118) a Procedure for Evaluating Environmental Impact

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A Procedurefor EvaluatingEnvironmental Impact

B y L u n a B . L e o p o l d , F r a n k E . C l a r k e ,B r u c e B . H a n s h a w , a n d J a m e s R. B a l s l e y

G E O L O G I C A L S U R V E Y C I R C U L A R 6 4 5

Washington 1971


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United States Department of the InteriorROGERS C. B. MORTON, Secretary

Geological SurveyV. E. McKelvey, Diredor

First through fifth printings 1971Sixth and seventh printings 1972Eighth and ninth printings 1973

Free on app l i ca t ion t o the U.S. G e o l o g i c a l Survey, Wash ing ton , D.C. 20244


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FOREWORD

Man cannot survive on this planet without utilizing its natural re-sources prudently. Every human action affects the world around us insome degree and the full effect is difficult to assess because of complexrelations among living and nonliving things. Under the circumstancesone can neither expect to restore the entire past nor preserve the entirepresent for future generations. However all can and should strive forproper balance between resource development and maintenance of pleasantsurroundings.The Environmental Policy Act of 1969 and the reports on environ-mental assessment that i t requires are aimed at insuping such a balancedapproach. To be effective we must provide a system for relating largenumbers of actions and environmental factors and for placing valuejudgments on impacts which are difficult to quantify.At my request the Geological Survey has developed an informationmatrix system that is described and modeled in this Circular. It is pub-lished with the thought that it will serve as a useful guide for environ-mental impact reporting and as a systematic reference. Those who sharewith us the desire to retain or improve the quality of our environmentwill recognize that this report is a sincere but still preliminary effort tofill an interim need. We hope that suggestions from others will improvethis framework.

ROGERS . B. MORTONS e c r e t a r y of the Interior


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A Pr o c e d u r e f o r Ev a l u a t i n g En v i r o n m e n t a l I m p a c tBy lu na 8. L eopold, Frank E. Clarke, Bruce B . Hanshaw, and James R. Balsley

PREAMBLEIn a recent article in Science discussing the En-vironmental Policy Act of 1969, Gillette (1971) statesThe laws instructions for preparing an impact re-port apparently are not specific enough to insure thatan agency will fully or even usefully, examine theenvironmental effects of the projects i t plans. This

report contains a procedure that may assist in develop-ing uniform environmental impact statements. TheDepartment of the Interior and the Council on Environ-mental Quality will appreciate comments on the pro-cedure here proposed.The heart of the system is a matrix which is gen-eral enough to be used as a reference checklist or areminder of the full range of actions and impacts onthe environment that may relate to proposed actions.The marked matrix also serves as an abstract of thetext of the environmental assessment to enable themany reviewers of impact reports to determine quicklywhat are considered to be the significant impacts andtheir relative importance as evaluated by the origina.tors of the impact report.Many exhaustive studies of the use of matricesfor environmental studies are now being undertaken.(See Sorensen, 1971.) This comparatively simple sys-tem is intended as a guide for the many people whoare faced with the evaluation and preparation of en-vironmental impact reports before the results of thesestudies have been completed. It should be borne inmind that there is presently no uniformity in approachor agreement upon objectives in an impact analysisand this generalized matrix i s a step in that direction.

The procedure does not limit the development of de-tail in any specific aspect of the environment; a sepa-rate expanded matrix for any environmental aspectcan easily be developed within the framework provided.INTRODUCTION

In any proposal for construction or develop-ment, it is the usual practice, both from thestandpoint of engineering and economics, toprepare an analysis of the need for the devel-opment and the relationship between i ts mone-tary costs and monetary benefits. More re-

cently, society has recognized that in additionto these customary economic analyses and dis-cussions of need, there should bea detailedas-sessment of the effect of a proposed develop-ment on the environment and thus i ts ecologi-cal, separate from its monetary, benefits andcosts; put together, these assessments comprisean Environmental Impact Statement. The prep-aration of a Statement should be done by ateam of physical and social scientists and engi-neers; ikewise, reviews of statements will gen-erally require an interdisciplinary team effort.

The Environmental Policy Act of 1969directsall agencies of the Federal Government toidentify and develop methods and proced-ures which will insure that presently un-quantified environmental amenities and valuesaregiven appropriate consideration in decision-making along with economic and technical con-siderations. The Council on EnvironmentalQuality, in furtherance of Section 102 of theAct, has set forth guidelines for the prepara-tion of the required environmental statements.It is recommended in these guidelines that thesecond item to be included in the statement isthe probable impact of the proposed action onthe environment.

This circular suggests an approach to accom-plish that specific requirement by providing asystem for the analysis and numerical weight-ing of probable impacts. This type of analysisdoes not produce an overall quantitative ratingbut portrays many value judgments. It can alsoserve as a guide in preparing the statementcalled for under Section 102(2) (c) of the Act.A primary purpose is to insure that the impactof alternative actions is evaluated and con-sidered in project planning.

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DEVELOPMENT OF AN ACTION PROGRAM;GENERALIZED PROCEDURE

Evaluating the environmental impact of anaction program or proposal is a late step in aseries of events which can be outlined in thefollowing manner. Figure 1 is a flow chart ofthe recommended sequence of events which re-sult in an environmental impact statement. Thesequence is discussed briefly below and thatportion which deals with impact assessment isexpanded in more detail later in the text:A. A statement of the major objectivesought by the proposed project.B. The technologic possibilities of achievingthe objective areanalyzed.C. One or more actions are proposed forachieving the stated objective. The alternativeplans which were considered as practicableways of reaching the objective are spelled outin the proposal.D. A report which details the characteristicsand conditions of the existing environmentprior to the proposed action is prepared. I nsome cases, this report may be incorporatedaspart of the engineering proposal.E. The principal engineering proposals arefinalized as a report or series of separate re-ports, one for each plan. The plans ordinarilyhave analyses of monetary benefits and costs.F. The proposed plan of action, usually theengineering report, together with the reportcharacterizing the present environment, setsthe stage for evaluating the environmental im-pact of the proposal. I f alternative ways ofreaching the objective are proposed in C andif alternative engineering plans are detailed inthe engineering report, separate environmentalimpact analyses must deal with each alterna-tive. I f only one proposal is made in the engi-neering report, it is still necessary to evaluateenvironmental impacts.

The environmental impact analyses requirethe definition of two aspects of each actionwhich may have an impact on the environment.The first is the definition of the magnitude ofthe impact upon specific sectors of the environ-ment. The termmagnitude is used in the sense

of degree, extensiveness, or scale. For example,highway development will alter or affect theexisting drainage pattern and may thus havea large magnitude of impact on the drainage.The second is a weighting of the degree of im-portance (i.e. significance) of the particularaction on the environmental factor in the spe-cific instance under analysis. Thus the overallimportance of impact of ahighway onapartic-ular drainage pattern may be small becausethe highway is very short or because it will notinterfere significantly with the drainage. De-pending upon the thoroughness and scope ofthe report inventorying existing environmentalconditions, the analysis of magnitude of impact,though in some details subjective, can never-theless be factual and unbiased. It should notinclude weights which express preference orbias.The importance of each specific environ-mental impact must include consideration ofthe consequences of changing the particularcondition on other factors in the environment.Again, the adequacy of the report under Dwould affect the objectivity in the assignmentof the values for specific environmental condi-tions. Unlike magnitude of impact, which canbe more readily evaluated on the basis of facts,evaluation of the importance of impact gen-erally will be based on the value judgment ofthe evaluator. The numerical values of magni-tude and importance of impact reflect the bestestimates of pertinence of each action.G. The text of the environmental impact re-port should be an assessment of the impactsof the separate actions which comprise theproject upon various factors of the environ-ment and thus provide justification for the de-terminations presented in F. Each plan of ac-tion should be analyzed independently.H. The Environmental Impact Statementshould conclude with a summation and recom-mendations. This section should discuss the rel-ative merits of the various proposed actionsand alternative engineering plans and explainthe rationale behind the final choice of actionand the plan for achieving the stated objective.

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A. Statement of objectiveQB. Technologic p ossibilit iesfor achievin g objective

C. Proposed actions andalternatives

D. Environm ental characteri-zat ion report prior toinit iation of action

E. Alternat ive engineeringplans

F3 F4 F5 F . Ident i f icat ion of im pactan d an aly sis of w n i t u d eand importance of impact.qg3 $ T4 G5 G. Assessment of impactH. Recommendations

FIGURE.-Flow chart for development of action programs.

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THE ENVIRONMENTAL IMPACT STATE MENTA complete environmental impact statementconsists of four basic items:1. A complete analysis of the need for theproposed action. This would include parts A, B,and C of the Generalized Procedures;2. An informative description of the en-vironment to be involved, including a carefulconsideration of the boundaries of a project.

For example, every drainage crossed byahigh-way can be affected at that point of crossingbut may also be affected downstream as wellowing to erosion. Therefore, these effects be-yond the right-of-way should be described inpart D of the Generalized Procedures;3. A discussionof the pertinent detailsof theproposed action-part E of the GeneralizedProcedures ;4. An assessment of the probable impacts ofthe variety of specific aspects of the proposedaction upon the variety of existing environ-mental elements and factors-parts F and Gof the Generalized Procedures-and a summaryor recommendation-part H-which would in-clude the rationale supporting the selected planof action.The analysis of need, item (1)above, shouldbea justification which considers the full rangeof values to be derived, not simply the usualcost-benefit analysis. It should includea discus-sion of the overall objectives and of possiblealternatives to meet them.

The characterization of the existing environ-ment, item (2) above, should be a detailed de-scription of the existing environmental ele-ments and factors, with special emphasis onthose rare or unique aspects, both good andbad, that might not be common to other similarareas. It should provide sufficient informationto permit an objective evaluation of the en-vironmental factors which could be affected byproposed actions. The description should in-clude all the factors which together make upthe ecosystem of the area. The vertical marginof the enclosed matrix can be used as a check-list in preparing this section.

The details of proposed action, item (3)above, should include discussion of possible al-ternative engineering methods or approaches

to accomplish the proposed development (item1).This should be done in sufficient detail sothat all actions that may have impact upon theenvironment (item2) can be checked. The hor-izontal margin of the matrix can be used as achecklist in preparing this section.

The environmental impact assessment, item( 4) above, should consist of three basic ele-ments:a. A listing of the effects on the environmentwhich would be caused by the proposed develop-ment, and an estimate of themagnitudeof each.b. An evaluationof theimportanceof each ofthese effects.c. The combining of magnitudeand importanceestimates in terms of a summary evaluation.

In preparing this circular, it is not the intentto deal at length with items (1) through (3),and it is assumed that generalized proceduresfor their preparation are commonly followedsince these items have been incorporated inmany engineering feasibility studies and bene-fit-cost analyses of past projects. Rather, theprimary intent is to focus on the new require-ment and, therefore to address primarily thepreparation of item (4)-the environmental im-pact assessment.

ENVIRONMENTAL IMPACT ASSESSMENTMATRIX

The analysis embodied in a, b, and c above ismade with a matrix (Plate1) including on oneaxis the actions which cause environmentalimpact and on the other existing environmentalconditions that might be affected. This pro-vides a format for comprehensive review toremind the investigators of the variety of in-teractions that might be involved. It helps theplanners to identify alternatives which mightlessen impact. The number of actions listedhorizontally in this sample matrix is 100 andthe vertical list of environmenta1 characteristicscontains 88, which givea total of 8,800possibleinteractions. Within such a matrix, only a fewof the interactions would be likely to involveimpacts of such magnitudeand importance thatthey deserve comprehensive treatment. Al-though the items listed represent most of thebasic actions and environmental factors likeIyto be involved in the full rangeof developments

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which require impact reporting, not all wouldapply to every project proposal. Even this largematrix may not contain all elements necessaryto make a full analysis of every project pro-posal encountered. However, the coding andformat are designed for easy expansion to in-clude additional items. Preliminary trials sug-gest that the number of applicable interactionsfor a typical project analysis usually will bebetween 25 and 50.

The most efficient way to use the matrix isto check each action (top horizontal list) whichis likely to be involved significantly in the pro-posed project. Generally, only about a dozenactions will be important. Each of the actionsthus checked is evaluated in terms of magnitudeof effect on environmental characteristics onthe vertical axis, and a slash is placed diagon-ally from upper right to lower left across eachblock which represents significant interaction.In marking the matrix, i t is important to re-member that actions may have major short-term impact (for a year or so) which areameliorated in a few years and thus of minoror negligible importance in a long time frame.Conversely, other actions with lesser initialimpact may produce more significant and per-sistent secondary effects and, therefore, havemajor impact in a long time frame. In the text,which discusses the matrix, one should indicatewhether he isassessing short-term or long-termimpact. As an example, oil drilling rigs arecommonly considered noisy and nonaestheticbut they are on location for short periods oftime-generally one to six months per site,whereas untreated spoil banks may silt andacidify streams for many years after comple-tion of a project.

In marking the boxes, unnecessary replicationcan be avoided by concentrating on first-ordereffects of specific actions. For example, min-eral processing would not be marked as affect-ing aquatic life, even if the waste productsare toxic in aquatic environments. The aquaticimpact would be covered under emplacementof tailing, spills and leaks, or other process-ing operations which may lead to degradationof aquatic habitat.After all the boxes which represent possibleimpact have been marked with a diagonal line,the most important ones are evaluated individ-

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ually. Within each box representing a signifi-cant interaction between an action and anenvironmental factor, place a number from 1to 10 in the upper left-hand corner to indicatethe relative magnitude of impact;10representsthe greatest magnitude and 1,the least. In thelower right-hand corner of the box, place anumber from 1 to 10 to indicate the relativeimportance of the impact; again 10 is thegreatest.

As an example, assume that a particularengineering proposal recommends constructionof highways and bridges. The proposed actionis item 1I.B.d. on the matrix. Highways andbridges might have environmental impactsthrough effect on erosion and related deposi-tion and sedimentation, among other things.Erosion and deposition-sedimentation occurunder the main heading Physical and Chemi-cal Characteristics of the Environment on theleft side (ordinate) of the matrix and in thehorizontal rows I.A.4.b. and I.A.4.c., respec-tively.In this example, i t might be that bridges willcause an important amount of bank erosion,because geologic materials in the area arepoorly consolidated. This may lead the investi-gator to mark the magnitude of impact ofhighways and bridges on erosion 6 or more. I f,however, the streams involved already havehigh sediment loads and appear to be capableof carrying such loads without objectionablesecondary effects, the effective importance ofbridges through increased erosion and sedimen-tation might be considered relatively small andmarked 1or 2 in the lower righthand cornerof the block. This would mean that while mag-nitude of impact is relatively high, the im-portance of impact isnot great.In the assessment of accidents (11, J ) suchas spills and leaks, it would be desirable tohave some guide which would be helpful indetermining the probability and effect of acci-dents. In this matter, the inclusion of controlswhich would reduce the probability of an acci-dent would lower the matrix entry of magni-tude, but it would have no influence on theevaluation of importame of impact.The next step is to evaluate the numberswhich have been placed in the slashed boxes.A t this point, it is convenient to construct a


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simplified or reduced matrix which consists ofonly those actions and environmental charac-teristics which have been identified as inter-acting. Special note may be taken of boxes withexceptionally high individual numbers, as bycircling the box. Although not used in this cir-cular, we have found it convenient, when com-paring alternatives in an action program, toidentify the beneficial impacts with + becausealternate action plans may have different de-grees of both beneficial and possibly detrimentalimpacts. However, in most cases the preparerwill consider all impacts to be potentially dele-terious because all the + factors would havebeen covered in the engineering report. Otherinvestigators may wish to devise their ownnumerical rating methods;hence, the marginalboxes of Plate I are simply titled "computa-tions".It must be emphasized that no two boxes onany one matrix are precisely equatable. Rather,the significance of high or low numbers for anyone box only indicates the degree of impactone type of action may have on one part of theenvironment. If alternative actions are underconsideration, and a separate matrix ispreparedfor each action, identical boxes in the twomatrices will provide a numerical comparisonof the environmental impact for the alterna-tives considered.

Assignment of numerical weights to themag-nitude and importance of impacts should be, tothe extent possible, based on factual data ratherthan preference. Thus, the use of a ratingscheme such as the one suggested here dis-courages purely subjective opinion and requiresthe author of an environmental impact state-ment to attempt to quantify his judgment ofprobable impacts. The overall rating allows thereviewers to follow the originators' lineof rea-soning and will aid in identifying points ofagreement and disagreement. The matrix, is infact, the abstract for the text of the environ-mental assessment.

TEXT

The text of an environmental impact assess-ment should be a discussion of individual boxesmarked with the larger numerical values for

magnitude and importance. Additionally, thosecolumns which cause a large number of actionsto be marked, regardless of their numericalvalues, should be discussed in detail. Likewise,those elements of the environment (rows)which have relatively large numbers of boxesmarked should be addressed. The discussionof these items should cover the following pointsas put forth in the Council on EnvironmentalQuality's guidelines published in the FederalRegister (1971) :(i) a description of the proposed action in-cluding information and technical data adequateto permit careful assessment of impact. (Thishas been covered as items C and E in fig. 1.)

(ii) the probable impact of the proposed ac-tion on the environment(iii) any probable adverse environmental ef-fects which cannot be avoided(iv) alternatives to the proposed action(v) the relationship between local short-termuses of man's environment and the maintenanceand enhancement of long-term productivity(vi) any irreversible and irretrievable com-mitments of resources which would be involvedin the proposed action should i t be implemented,and(vii) where appropriate, a discussion of prob-lems and objections raised by other Federal,State, and local agencies and by private orga-nizations and individuals in the review processand the disposition of the issues involved. Thissection may be added at the end of the review

process in the final text of the environmentalstatement.All of these points itemized above can becovered as part of a discussion of the matrix.The text that accompanies the completedmatrix should be primarily a discussion of thereasoning behind the assignment of numericalvalues for the maynitzrde of impact effects andtheir relative importance. The text should in-clude a discussion of those actions which havesignificant impact and should not be diluted bydiscussions of obviously trivial side issues.To be fully understandable, the discussion ofthe magnitude and importance of applicableimpacts and responses will require some dis-

cussion in the text of the principal character-istics, physical and ecological, of the environ-6


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ment itself and some of the important charac-teristics of the proposed action which governits environmental impact. The environmentalimpact assessment thus relies on and refers tothe data incorporated in items 1, 2, and 3 (p. 4)-the full description of the geography, physicalsetting, vegetation, climate, and other factsabout the environment and the physical andengineering aspects of the proposed develop-ment. This explanation is inserted here to cau-tion that the environmental impact assessmentneed not be burdened nor should it be paddedwith descriptions of the project and the envi-ronment per se. I t should include only suchdetails as are needed for evaluating the en-vironmental impact. The completed environ-mental impact assessment, together with items( l ) , 2), and (3), comprises the finished En-vironmental Impact Statement; all four itemsare required for review purposes.

In order to test the usefulness of the matrixapproach, amatrix for an actual proposed min-eral extraction and processing operation hasbeen prepared and included as an appendix. Thisexample is solely a model used for demonstra-tion purposes and is not intended to be an im-pact assessment of the example project. A briefsynopsis of the justification, regional setting,and general plan of operation extracted from areport which covers items ( l ) , (2), and (3) ofan environmental impact statement is included.In addition, for each of the boxes with entries,there is a brief discussion of the impact ratingincluding the reasoning behind the assignmentof values.

CONCLUDING STATEMENTObviously, the wide variety of projects andactions have such differing impact on environ-mental factors that no scheme of impact as-sessment will be universally applicable. How-ever, greatest need is not for a single anduniversally applicable assessment method, butrather for a simple way of summarizing whichimpacts are considered of greatest moment bythe people making the assessment. Different

assessors will seldom come to identical conclu-sions, but it would be useful to know the basisfor the difference.

The advantage of a matrix is in its use asa checklist or reminder of the full range ofactions and impacts. The proposed manner ofusing the matrix is aimed at separating as faras possible factual information on magnitudeof each type impact from the more subjectiveevaluation of the importance of the impact, thelatter involving preference or bias to some de-gree. This separation of fact from preferenceis highly desirable.Finally, the matrix and suggested method ofuse is presented as a draft, subject to improve-ment, expansion, and change. Because it is im-practical to circulate unpublished manuscriptswidely, this manuscript is being submitted forreview by potential users as a U.S. GeologicalSurvey circular, a series used for tentative,incomplete, or preliminary statements.The authors acknowledge with thanks thecooperation of Robert H. Twiss for sharing hisexperience in matrix construction and for histhoughtful review of this manuscript. The helpfurnished through discussion, manuscript re-vision, and suggestions by Elmer Baltz andGeorge Davis is also gratefully acknowledged.

APPENDIX: IMPACT ASSESSMENT OF APHOSPHATE MINING LEASE BYMATRIX ANALYSISA phosphate deposit estimated to include 80million tons of crude ore of an average con-

tent of 8.7percent P20, s located in Los PadresNational Forest, Ventura County, California.The ore consists of sand-size pellets of phos-phorite occurring in a sequence of sandstonesand siltstones of late Miocene age. The bedscrop out on hillslopes along a strike length ofabout 5 miles. The beds dip approximately 30"north. The mineable beds are 90 feet thick withan overburden varying from0 to 200 feet.

Application for a prospecting permit wasmade in February 1964, and a permit wasgranted in November 1964. A 3-year extensionof the permit was approved in October 1966.The company made an application for a Prefer-ence Right Phosphate Lease in April 1969. Thebackground material needed for the presentanalysis is contained in the company's report.Parts of the report are abstracted below forpurposes of this circular.

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The wgional environment.--The deposit oc-curs in a semiarid region receiving 23 inches ofannual percipitation, most of which occurs inthe perio$ November through April. The prin-cipal drainage system in the area is SespeCreek; its headwaters are about 5 miles westof the Lease Application. In its upper reaches,Sespe is an ephemeral stream. The proposedmining operation would be 2 miles north ofthe Sespe. Vegetation ranges from sparse tomedium heavy, is of a chaparral type includingoak, manzanita, and mountain mahogany, andwith a low density ground cover of grass.

Access to the area is by means of CaliforniaState Highway 33, a black-topped paved roadwhich runs from Ventura to Bakersfield. Theprospect is within one to two miles of this high-way; present access is over a temporary un-paved road. To develop the property, about 11/2miles of permanent paved road would have tobe built.

The region is sparsely settled. In a 5-mileradius of the proposed mine, there are six year-round residents plus 10 summer residences.The nearest towns are Meiners Oaks and Ojai,25 miles to the south, and New Cuyama about35 miles to the north.

General mining plans.-The ore crops outas anarrow band about 5 miles long. Test coredrilling indicated that the rock is too unstableto support underground workings and the com-pany proposes to develop the mine by open-pitmethods. The strike is approximately perpen-dicular to the local stream channels which draintoward Sespe Creek. The small canyons cutacross the ore zone every 2,000 to 3,000 feetalong the strike. I n order to prevent damage tothe watershed, the company envisions a min-ing operation which would not damor interruptthese channels. Therefore, over the life of themining operation a series of open pits would bedug parallel to the strike and terminated shortof the tributary valleys which cross the orebody. The dimensions of the proposed open pitswill be determined by the interval between ad-jacent canyons. Pit width would be a functionof the amount of overburden which could beremoved economically. In the downdip direction,mining would extend only so far as economicsof overburden removal would allow.

The planned open pit geometry is V-shaped.One limb would follow the foot wall of the orezone at approximately 30" from the horizontal.The high wall would be cut at 45 " to the hori-zontal. Such a pit would be worked in a seriesof 20-foot high benches running parallel to thestrike.Ore processing.-An ore-processing plantwould be constructed at the mine site to crushthe ore. After crushing, the phosphate would

be leached out with acid. The resultant preg-nant liquor would be neutralized with quicklimeto precipitate dicalcium phosphate in a granu-lar form.The tailings from the leach process is quartzsand which would be washed, dewatered, andstored in the open pit areas where mining hadbeen completed.The phosphate in the form either of granularsolids or liquid would be transported to marketvia trucks. The major raw materials required

to be brought in are quicklime and sulphur, thelatter being converted to sulphuric acid at themine site. Water required for the processing issmall and is to be supplied by a 1,000-foot deepwell already drilled.

Watershed and environmental values.-Thereare two principal environmental values whichrequire consideration in this area as well asmany subsidiary ones. A primary-considerationis the effect on the California condor, a rare andendangered species present in the general re-gion. The second major consideration is loca-tion of the mine lease close to the center of alarge block of National Forest land. Pertinent tothe latter is the fact that the total lease, 2,434acres, is small by comparison with the totalForest. The site is 15 miles east-southeastalong the mountain ridge from the edge ofthe San Rafael Wilderness so that no designatedwilderness lands are involved. However, theneed for recreational use of undeveloped publiclands in California to relieve population pres-sure is relatively great and any commercialoperation in an undeveloped area would havean effect on such use.

The Sespe Condor Sanctuary, located in theNational Forest, lies 15 miles to the east ofthe mining area. From this sanctuary, the con-dors are said to range along the crestline to

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the northwest, across the center of the wholeNational Forest area. The ordinary flightor soaring patterns for condors would passthrough the general region of the proposedmine site. One condor nest, apparently nowabandoned, has been noted a few miles west ofthe mining site. The other known condor nestsall lie within the condor sanctuary.Among the subsidiary environmental impacts

which the mining operation might cause, a feware mentioned briefly below and are discussedin more detail in connection with the impactmatrix.The possibility of water pollution from thephosphate itself is minimized by the fact thatthe phosphate ore is quite insoluble as shownby water quality analyses on surface water inthe area. The mining operation would not in-crease the soluble phosphate content of thewater resource. The effectiveness of erosioncontrol measure applied within the mining areawill determine the quantity of particulate phos-phate mineral and other sediments added toSespe Creek. The liquid chemicals handled atthe plant are to be confined within dikes. Ex-cept for possible leakage from these dikes, orin case of spills on the highway, water pollutionfrom processing chemicals and products shouldnot occur.

Increased soil erosion and related sedimentload to stream channels will depend upon themanner in which the stream channels crossingthe ore body are protected from the open-pitmining operation.Some level of air pollution is possible fromnoxious gases emanating from the plant inthe form of fluorine from the ore, SO, gasfrom the manufacture of sulphuric acid, andfuel combustion products. Blasting, drilling, andequipment noise will have some environmentalimpact. Mining equipment will be diesel-pow-ered and controlled by conventional mufflers.

The power requirements of the plant are es-timated to be 5,000 K V A . The mine would re-quire the construction of 14 miles of transmis-sion lines which is to be erected on wooden poleson the right-of-way of State Highway 33. Nat-ural gas would be taken from a pipeline al-ready in the area which passes within 3 miles

of the proposed plant site using either over-head or buried lines.The impact on vegetation and wildlife is in-fluenced by the fact that, over the life of themine, only 400 acres will be subjected to actualmining. The mining operation would involveanannual excavation of 4 to 5 acres with recla-mation following closely in the mined-out area.

A total of about 40 acres thus would be dis-turbed at any given time.The brief summary above shows the main

aspects of the planned mining operation forwhich environmental impact is being evaluated.More details on these and other aspects of thearea and the project plan are contained in thecompanys report.Using material contained in the companysreport, an information matrix analysis wascompleted in the manner described in the pre-vious section of this circular. The outcome ofthe analysis is recapitulated. in reduced formas figure2. The explanations which follow in-

dicate the reasoning followed in this example.The mining plan calls for a small alterna-tion of drainage so that effects on erosionand sedimentation should be minor as com-pared with the effect of highways andbridges and emplacement of tailings. Mod-ification of habitat and alteration of groundcover are not likely to be important impactsbecause the total mined area is relativelysmall. Industrial buildings and constructionof highways are considered to be among themore important impacts. The blasting anddrilling under construction (11. B. 9.) willbe short term and have limited impact, butdrilling and blasting for resource extrac-tion (11. C. a. ) will continue sporadically overthe life of the project and, therefore, is rela-tively important. Surface excavation andmineral processing appear to have rela-tively important impact potential. On detailedconsideration, product storage and erosioncontrol are viewed as less important thansome of the construction and resource extrac-tion items noted above. Changes in trafficowing to the increase in trucking rather thanincrease in automobile traffic is considered tobe capable of producing important impact. The

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,emplacement of tailings would occurthroughout the life of the project and could havesignificant effects if poorly controlled. Liquideffluent discharge would be small during allphases of the project, and, therefore, would berelatively unimportant by comparison. Spillsand leaks owing to accidents could be im-portant within the mining operation area de-pending on the effectiveness of diking. Acci-dents would be especially significant on thehighways over which new materials and fin-ished products must be hauled.With such consideration, the number of pro-posed actions considered important enough for

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FIGURE.-The reduced matrix for a phosphate mining lease.discussion was reduced to 9. Under each ofthese items in the vertical column existingcharacteristics and conditions of the environ-ment were inspected individually. Where theinteraction was deemed sufficiently important,the impact was numerically evaluated in termsof magnitude and importance. The resultingcodification appears in the completed matrix(fig. 2). The types of impact are discussed be-low in order of the items listed on the left-hand side of figure 2.

Water quality ( I . A . 2. d.) .-Water qualitycould be affected by the surface excavation,by emplacement of tailings, and by the pos-10


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sibil ity of accidental spills and leaks. Theplanned surface excavation is off-channeland was, therefore, assigned magnitude 2. Be-cause of the ephemeral nature of the streams,the importance of the excavation in affectingwater quality was rated 2 also.The same reasoning applies to the emplace-ment of tailings which are off-channel and notof a noxious character. Spills and leaks were

considered sufficiently rare to be assignedmagnitude 1,but i f they occurred, they wouldbe moderately important and, therefore, givena value of 4.In actual practice, any of the identified im-pacts can be expanded to produce secondarymatrices which can cover greater detail thanis possible on plate I or figure 2 if the analystsor reviewer feels the need to do so. As an ex-ample, expanding the matrix items related towater quality, the relative magnitude andimportance of different specific actions may bemore clearly shown than by merely using themain headings in the matrix. The example (fig.3) indicates how expansion may show detailspertinent to the individual situation. Addi-tionally, water quality could also be expandedinto subcategories such as pH, dissolved oxy-gen, turbidity, etc.Atmospheric quality ( I .A. 3. a.) .-Mineralprocessing would be the principal source ofdegradation in atmospheric quality. I ts m g -nitude was rated 2 owing to the small size ofthe plant and the absence of other industrialoperations. Its importance, however, was rated

3 because of the sulphuric nature of the gasesproduced.Erosion ( I . A. 4. b.) and deposition (1.A. 4.c.) .-Some erosion and thus some channeldeposition will be caused by the construc-tion of highways and bridges and by theemplacement of tailings. The sandy natureof the washes in the area and thus naturallyhigh sediment loads give both erosion anddeposition caused by the project a relativelylow importance. The magnitude and impor-tance of each were relatively low owing to thefact that the mining operation would involvethe construction of less than 2 miles of newroads and that protection against erosion isincluded in the design of the mining operation.

Shrubs ( I . B. 1. b.) and grasses ( I . B. 1.c.) .-The disturbance of native shrubs andgrasses is important only on the area whichis going to be physically disturbed by the min-ing. Because vegetation change would occuronly on parts of the 2,434 acre lease over thelife of the project and revegetation is part ofthe scheduled project, the magnitude and im-portance are both rated low.

Aquatic plants (I. B. I . f.).-Aquaticplants do not occur in the ephemeral streamsnear the plant site but do occur in the portionof the main stream some miles down valleywhere Sespe Creek is perennial. Any effect onaquatic plants reaching that f ar down-stream would come from excavation andfrom emplacement of tailings. The distanceto the perennial stream indicated low valuesfor magnitude, but a moderate value for im-portance in the case of spills.F i sh (I .B. 2 e.).-The same reasoning thatgoverned the assessment of impact onaquatic plants applies also to fish whichpersists only some miles downstream whereSespe Creek is perennial and the probable im-pacts are rated low.Campingand Hiking ( I . C. 2. e.) .-The onlyalteration involving camping and hiking iscaused by surface excavation. Owing to thesmall area to be affected, i ts magnitude is rated2, but its importance was considered moderateand rated 4 because any environmental changethat interrupts recreational use of public landin a highly populated State is relatively impor-tant.Scenic V i ews and Vi stas ( Z I . C. 3.a.) -Thisis one of the characteristics that is most seri-ously impacted by the proposed development.Scenic views are impaired in quality owingto industrial buildings, highways andbridges, transmission lines, surface exca-vation, trucking, and emplacement of tail-ings. All these have a low to moderate valueof magnitude and generally a somewhat higherfigure for importance. Compared with any ofthe previous items, the actions impactingscenic views and vistas are more numerous.

Wilderness quali ties (1.C. 3. b.) .-The itemwilderness and open space (I. B. 1. a.) asa land use is not important in this area be-

4 6

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Water quality

High-Industrial wayssites andbuildings andbridge:Surfaceexcav-ation

vlineraproc-essing

Y-2$ 2=? ?E m0 %v o5 . tle os 2m r

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FIGURE.-Expanded matrix showing actions which would impact water quality.cause it is not designated wilderness; accord-ingly, it was not rated. What is important isthe aesthetic and human interest item-wil-derness qualities. Thus, a distinction is madebetween wilderness as a land use, not im-portant in this area, and the quality of wildland which is considered highly important inthe area. Wilderness qualities would be im-pacted under the proposed project primari lyby industrial buildings, highways andbridges, surface excavation, trucking, andemplacement of tailings. The impact of eachon wilderness qualities i s rated moderatewith respect to both magnitude and impor-ance. The result of this is that the degradationof wilderness qualities may be considereda potentially important impact caused by theproposed development.Rar e and unique species ( I . C. 3. h.).-Pos-sibly the most important environmental impactof the proposed development is its potentialeffect on the condor. A distinction is made be-tween the biological conditions of fauna, en-dangered species (I . B. 2. g. ), and the itemunder aesthetics and human interest, rareand unique species. The condor could be cov-ered under either of these two, but should not

be under both. A s a matter of choice then, thecondor problem is specified under the item ofaesthetics and human interest.Consideration was given to the fact that themain nestingareafor the condors is some milesto the southeast and that a Naval trainingcamp involving much heavy equipment is al-ready operating near that nesting area. It isbelieved that the effect of the proposed devel-opment on condors would come about primari lyfrom the blasting and from the increase intruck traffic. For both of these actions, themagnitude is considered moderate and rated 5,but the importance of the survival of condorswas considered to be great and thus any impactis of high importance. Those two items were,therefore, given an importance score of 10.Also the sulphur fumes from mineral process-ing might be an important deterrent to the useof this part of the range by condors. The effecton the birds is unknown, but i t i s conceivablethat air pollution would keep them from land-ing to catch prey wherever the smell and smokeoccurred. The magnitude of impact of thi s ac-tion was assessed as 5 and amportance as 10.

Health and safety ( I . C. 4.. b.).-Healthand safety would be impacted primari ly by

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the increase in trucking on the highway asa result of mine operation.Summary.-Inspection of figure 2 immedi-ately gives the essence of the matrix analysis:the proposed actions which have the most en-vironmental impacts are the construction ofhighways and bridges, the blasting, sur-face excavation, mineral processing, truck-ing, and the emplacement of tailings. Theenviromental characterisitcs most frequentlyimpacted are thoseof scenic views and vista,wilderness qualities, and rare and uniquespecies.

AS an outcome of this matrix analysis, thereviewers could ask the petitioners for thephosphate project What actions can you taketo reduce these possible impacts to lower lev-els? if the impact is deemed sufficiently great.A s an example, assume that the company, inlight of the comparative values shown in thesimplified matrix, decided to substitute fordaytime trucking, a night-time only schedulefor moving supplies and products. If it wereknown that condors soar only during the dayand would be unaffected by night-time traffic,that magnitude-importance impact might be

significantly reduced. Assume also that as an-other step to reduce impact, the company de-cided to mat the ground surface prior to anyrock blasting. If this step were deemed effee-the, matrix entry of 5/10 of blasting on rareand unique species might perhaps reduce theentry a.t 1/10. These changes may, in one sense,appear to be minor, but in fact would cause asignificant reduction in impact on the specificenvironmental factor shown to be mostaffected.

REFERENCESCouncil on Envi ronmental Quality, 1971, Statementson proposed Federal actions affecting the environ-ment: Federal Register, v. 36, no. 19, p. 1398-1402 and no. 79, p. 7724-7729.Gillette, Robert, 1971, Trans-Alaska pipeline: Impact

Study Reeeives Bad Reviews: Science, v. 171, Mar.19.Sorensen, J . C., 1971, A framework f or identificationand control of resource degradation and conflictin the multiple use of the coastal zone: Univ. ofCali f., Berkeley, Dept. of Landscape Architecture,M. S. thesis, p. 42; in press, Univ. of Calif. Press.(Contains a statesf-the-art review of matrix usein environmental studies)

*U.5. G O V E R N M E N T P R I N T I N G OFF ICE : 1973-515--658/62

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(118) a Procedure for Evaluating Environmental Impact

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