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<br />EFFECT OF URB~N DEVELOPMENT ON STREAM
<br />WATER QUA LITY
<br />
<br />Regional variations in the quality of
<br />surface ~aters arise naturally, deter-
<br />~ined by the mineral structure of the
<br />geological strata and the chemistry of
<br />the surface soils (Berry, et a1.
<br />1974). However, it is generally ac-
<br />cepted that urban development causes a
<br />deterioration in this variable natural
<br />quality of ~urface waters. The effect
<br />is not a simple one, and methods of
<br />predicting it are not well developed.
<br />In addition, the manner in which a par-
<br />ticular activity or type of development
<br />causes a change in water quality may
<br />itself he complex (Coughlin and Hammer,
<br />1973) .
<br />
<br />Among the sources of pollution in urban
<br />runoff water are sediments originating
<br />from construction sites, debris and
<br />contaminants from streets, contaminants
<br />from open land areas, ?ublicly used
<br />chemicals, air deposited substances,
<br />ice control chemicals, and dirt and
<br />contaminants washed from vehicles (Sar-
<br />tor, et al. 1974). Previous studies
<br />provide valuable information on the
<br />total problem of water pollution re-
<br />sulting from urban runoff. They point
<br />out the shock pollution loads which
<br />storm runoff from urban areas can place
<br />on receiving waters. Principal conclu-
<br />sions from many of these studies are
<br />listed by Sartor, et al. (1974), Amy,
<br />et a1. (1974), McElroy, et a1.
<br />(1976), Wanielista, et al. (l977), and
<br />by Waugh (1978) as:-
<br />
<br />1. Water temperatures can be increased
<br />5-8 degrees C in summer and lowered
<br />up to 3 degrees C in winter.
<br />
<br />2. Concentrations of suspended solids
<br />can increase dramatically during
<br />urban land development and con-
<br />struction.
<br />
<br />3. Dissolved load in streams can in-
<br />crease up to ten-fold with urbani-
<br />sation.
<br />
<br />4. With secondary treatment of urban
<br />waste water, more than half of the
<br />residual pollution in a stream will
<br />come from unrecorded and uncon-
<br />trolled sources, e.g. urban storm
<br />water discharges and runoff frOM
<br />farmland.
<br />
<br />s. Runoff from street surfaces is gen-
<br />erally highly contaminated and is
<br />similar in many respects to sanita-
<br />ry sewage. Calculations based on a
<br />typical city indicate that the ru-
<br />noff from the first hour of a mod-
<br />erate-ta-heavy storm (brief peaks
<br />to at least 1.3 cm/hr) contributes
<br />considerably more pollutional load
<br />than does the same city's raw sani-
<br />tary waste during the same period
<br />of time. These calculations are
<br />for a situation in which streets
<br />ere cleaned (intentionally or by
<br />rainfall) about once every five
<br />days.
<br />
<br />6. The major constituent of street
<br />surface contaminants is consistent-
<br />ly found to be inorganic,
<br />mineral-like matter, similar to
<br />common sand and silt. The loading
<br />intensities of these contaminants,
<br />
<br />expressed as weighted average va-
<br />lues for all samples, were found by
<br />Sartor, et al. (1974) to be:
<br />total solids, 395 kg/curb kmJ
<br />volatile solids, 28.2 kg/curb kmJ
<br />BODS, 3.80 kg/curb km; COD, 26.8
<br />kg/curb km: phosphates, 0.310
<br />kg/curb kmJ nitrates, 0.026
<br />kg/curb km; Kjeldahl nitrogen,
<br />8.620 kg/curb km: total coliforms,
<br />61,800 ~illion/curb km: and faecal
<br />coli forms, 3,480 million/curb km.
<br />
<br />.
<br />
<br />The extreme variability of water
<br />quality in urban storm water is de-
<br />monstrated by wanielista, ct al.
<br />{1977}. Ranges of para~eter va-
<br />lues, exoressed as conc~ntr~tions,
<br />are stated to be: tot~l solids,
<br />451 to 14,6~a mg/l: total suspen~-
<br />ed solids, 2 to 11,303 mg/l:
<br />volatile suspended solids, 12 to
<br />1,60W mg/l; BODS, 1 to 70B mg/l;
<br />COD, 5 to 3,10~ mg/l: total P04,
<br />0.1 to 125 mg/l: soluble P04, 0.1
<br />to Ig mg/l; organic N, 0.1 to 16
<br />mg/l: NH3-N, 0.1 to 2.5 mg/l:
<br />chlorides, 2 to 25,000 mg/l (with
<br />highway deicing): total coliforrns,
<br />280 to 146 mi1lion/100ml; faecal
<br />coliforms, 55 to 112 million/100ml~
<br />and faecal streptococci, 200 to 1.2
<br />million/100m!.
<br />
<br />!
<br />
<br />7. Significant amounts of heavy metals
<br />were detected in the contaminant
<br />materials. zinc and lead were the
<br />most prevalent, and for the cities
<br />tested yielded average values of
<br />8.183 and a.e56 kg/curb km respec-
<br />tively.
<br />
<br />8. Substantial quantities of organic
<br />pesticides and related compounds
<br />were also found in the street sur-
<br />face contaminants~ Although the
<br />data showed considerable variation
<br />from. site to site, loads in the
<br />order of 0.00028 kg/curb km were
<br />found for the cities tested. Both
<br />chlorinated hydrocarbons and poly-
<br />chlorinated biphenyl compounds
<br />(PCB) were found rather consistent-
<br />ly.
<br />
<br />.
<br />
<br />.
<br />
<br />9. Grease and oil are the major organ-
<br />ic constituents of street particu-
<br />lates, and are shown to occur with
<br />concentrations up to 110 mg/l.
<br />
<br />11. The quantity of contaminant materi-
<br />al on street surfaces varies wide-
<br />ly. Principal factors which affect
<br />the loading intensity at any given
<br />site include surroundina land use,
<br />elapsed time since streets were
<br />last cleaned, local traffic volume
<br />and character, street surface type
<br />and condition, public works prac-
<br />tices, and season of the year. In
<br />general, industrial land use areas
<br />tend to accumulate contaminants
<br />faster than commercial or residen-
<br />tial areas~
<br />
<br />.
<br />
<br />11. Loading intensities were found by
<br />Sartor, et al. (1974) to average
<br />791 k9/curb km for industrial
<br />aites, Bl.R kg/curb km for commer-
<br />cial areas, and 338 kg/curb km for
<br />residential areas.
<br />
<br />.
<br />
<br />12. Total colifocms are higher in in-
<br />dustrial than commercial areas, and
<br />lowest in residential areas.
<br />
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