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<br />78
<br />SOIL SURVEY
<br />a high, or rapid, infiltration rate even though thor-
<br />oughly \eetted, and consist chiel{v of deep. \\ell
<br />drained to excessicek rlrainerl, a,arse le>aured soils.
<br />'t'hey have a high rate of water transmission.
<br />Croup L' soils hate a nxxlerntcip lu++ runoff potential.
<br />Thev hace a morlernte inlil(ratimt rate +chen thoroughly
<br />wetCerl and consist chiellc of moderately deep or deep,
<br />moderately tvrll drained nr t+ell drained. moderately
<br />fine texlurcrl to moderately coarse textured soils that
<br />hate moderately' sln+c to moderately rapid permeabil-
<br />ih'. They have a mnrlerate rate of +yater transmission.
<br />Group C soils have n morleratelc high runoff pnten-
<br />tial. Then hnye a slmy infiltration rate \chen thnrnughl}•
<br />wetted and consist chiellc of soils +yith a lacer that
<br />impedes dmymyard mm ement of water and sails that are
<br />nuulerately fine tektured or tine textured. hace a slo\v
<br />infiltration rate because of salts nr allclli, nr hace a
<br />moderately' high water table. '1'hcy hace a slow rate of
<br />\vater transmission.
<br />Group D soils have a hi),!h rlmnR~ potential. They
<br />have a ccrc slmy infiltration rate tyhen thoroughly
<br />o•etted and consist chiefly' Ilt clay "oils u'ilh a high
<br />swelling potential, soils +cith a permanently high \rlter
<br />table, a cLlypan m' clay' Ial'el' ilt nr near the surface,
<br />ver\• slow infiltratimt because of salts or ;Ilkali, and
<br />shallow soils over nearlc impervious material. They
<br />have a ycry slaty rate oC e'ater lr;utsmissiun.
<br />lSnFLrrrrinr in(rrprrr(n(inn.c
<br />The interpretations in table 7 ;ue 1,aserl nn the esti-
<br />mated engineering properties of soils shrlt~ n in table
<br />(,, on test dat;t for snits in this surce~• ;u ca and others
<br />nearby nr nd.ioining. ;uxl nn the esperiencn of engineers
<br />;ctrl soil scientists with the sails of Pin Gr;utdc C•nwtt>'
<br />Area. In table 7, ratings :ue used W sununarize limita-
<br />tion or suitability oC the soils for :Ill listed Inlrposes
<br />other than far drainage of cropLuul and pasture, irri-
<br />gation, ponds and rescrynirs, emb:ull:mcnls, ;uul ter-
<br />races and diversions. I'or these pnrlirul;u• uses. table 7
<br />lists those soil features not be overlouherl in planning,
<br />installation. anti maintenance.
<br />Soil limitations ve expressed as slight, moderate,
<br />and seyere..Slrp/rt means Chat soil prnpa ties ;u'e ~rene-
<br />rally favorable for the rated use, nr in other tyords,
<br />limitations are minor ;Ind arc easily oyac•ame. d/od-
<br />rrrrte means that some sail properties arc unfacurable
<br />but can he uyercmne nr ntndified be special planning
<br />and rlesig~n. Srrrrr indicates sail properties sn unfavor-
<br />able and so difHc•ult to correct ur u\'ercmne that major
<br />soil reclamation, special design, or intensive mainten-
<br />ance is required. rot some uses, the rating of severe is
<br />divided to obtain ratings of se\•ere ruxl \e„• severe.
<br />Vrr7~ srrrve indicates one nr more soil properties so
<br />unfavm'able fm' a partic•ulnr use that overcoming the
<br />limitations is dillicull and costly and connuunle not
<br />practical for the rated use.
<br />Soil suitnl,ility is expressed as good, fair, poor, and
<br />(rnsuitnGlr. 'T'hese terms have me,utings appr<+~imately
<br />parallel n'ilh the terms slight, moderate, severe, and
<br />eery severe.
<br />IPoflowing ace explanations of clone of Lhe columns
<br />in table 7.
<br />Topsoil is used for topdressing nn area +yhere vege-
<br />tation is to be established and maintained. Suitabilite is
<br />affected mainh~ by the ease of a' rking and spreading
<br />the soil material, as in preparing seedbed; the natural
<br />fertility of the material, nr its re ponce to plants when
<br />fertilizer is applied; and the abset ce of substances tonic
<br />to plants. Texture of the soil ma erial and its content
<br />of stone fi•agments are character sties that affect suit-
<br />ability. -41so cmtsidererl in the r, tings is damage that
<br />will result in the wren from n'hich he topsoil is taken.
<br />Sand and grnyel are used in gr t quantities in many
<br />kinds of construction. The ratio s in table 7 pro\•ide
<br />information on probable source.. A soil rated as a
<br />food or fair source of sand or g'acel generalh~ has a
<br />lar'er at least 3 feet thick. the to of \chich is tyithin a
<br />depth of fi feet. The ratings do t of take into account
<br />thickness of overburden. locatiol of the tyater table,
<br />or other factors that affect minis of the materials, and
<br />neither do they indicate qualih of he deposit.
<br />Road fill is soil material used in embankments fm'
<br />roads. The suitability t.ntings refl ct the predicted Ixr-
<br />favnance of soil after it has been tfaced in an em~ank-
<br />ment that has been properly con parted and In•ocided
<br />with adequate rlrainnge. ;uui the elatice ease of exca-
<br />vatingthe material at borro\\' area .
<br />Septic tank filter fields v'e.subs dace systems of the
<br />m• perforated pipe that dish'ibut effluent from a sep-
<br />tic tank into natural soil. The oil material from a
<br />depth of f3 inches to (i feet is eyal aced. The soil prop-
<br />perties considered are those that a ect both absorption
<br />of efiuent and construction and Iteration of the Sys-
<br />tem. Properties that affect absm•p nn are permeability,
<br />depth to \yater table or rock, and s tsceptibility to flood-
<br />ing. Slope is a soil Ilt'operty tha affects layout and
<br />consh'uction and increases the isl: of soil erosion,
<br />lateral seepage, anti dotynslope fl \+' of effluent. Large
<br />rocks or boulders increase consh•u tion costs.
<br />FIomesites frith basements, as ated in table 7, are
<br />sites for d\celtings that are no mo'e than three stories
<br />high and are supported by found. tint footings placed
<br />in undishn~bed soil The features tat affect the rating
<br />of a soil for dwellings are those tl at relate to capacity
<br />to support load and resist settlem nt under load, and
<br />those that relate to ease oC excav. Lion. Soil properties
<br />that affect capacity to support to rl arc wetness, sus-
<br />ceptibility to flooding, density, pl< ticity, texture, and
<br />shrink-swell potential. Those that ffect excm~ation are
<br />tcetness, slope, depth to bedrock, a td content of stones
<br />anti rocks.
<br />Highway location pertains to su erhighways similar
<br />to those of the interstate scstem a d not to local roads
<br />and streets. In estimating the soil features that affect
<br />selection of hightyay IneaGOn, e\alnatlOR is for the
<br />profile of an undishu'bed soil that as not keen drained
<br />but has had its organic surfac layer removed, if
<br />one occurs. Some of the features considered are the
<br />height of the \yater table; the haz u'd of flooding; the
<br />stability of the soil material, parti ularly tinder heavy
<br />loads of pressure; depth to and kin of bedrock; degree
<br />of frost hazard; and slope.
<br />Dikes and diversions are emba kments, or ridges.
<br />constructed across the slope to int crept runoff so that
<br />it soaks into the soil or flo\as slow) • to a prepared out-
<br />let. features that affect suitability f a soil fm' dikes or
<br />
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