UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WATER PLANNING DIVISION
As part of the continuing Water Quality Management Program this
report is being sent to areawide agencies designated under Section
208 and State planning agencies implementing sections 303 and 208 of
the Federal Water Pollution Control Act Amendments of 1972. Legislated
and court imposed deadlines combined with changing technology and water
planning methods make the rapid transfer of information essential. Our
purpose is to stimulate thought and avoid unnecessary duplication but
not to imply a broad EPA endorsement of methods or statements. Our
desire to rapidly distribute reports of potential value to the planning
process will mean that some material will be in an early draft form.
It is hoped that this report contains information which will help estab-
lish the foundation to support the implementation of specific programs
developed through the Water Quality Management Process.
STORMWATER QUALITY SUMMARY
PREPARED FOR NEW CASTLE COUNTY, DELAWARE
NOVEMBER, 1975
PRELIMINARY DRAFT
-------
DRAFT DOCUMENTS
ON THE SUBJECT OF
STORMWATER MANAGEMENT
Prepared for the
NEW CASTLE COUNTY, DELAWARE
AREAWIDE WASTE TREATMENT MANAGEMENT PROGRAM
NOVEMBER 1975
-------
COUNTY
POLICY BOARD I V N^ ONE PEDDLER'S ROW
MELVINSLAWIK. COUNTY EXECUTIVE ^HM* JHU-'-'"'' /\ 4. PEDDLER'S VILLAGE
THOMAS MALONEY, MAYOR, CITY OF WILMINGTON > TB §8\ *1 ' >-X '"' NFUVABK np 1Q7n'J
WILLIAM REDD. MAYOR, CITY OF NEWARK fllWP' S5S ^ ,7 ^ NfcWAHK, UE. la/02
DIRECTOR OF WILMAPCO, CHAIRMAN S5»*.:«BH -!* "=" * '/ ' (302)731-7670
208 ADMINISTRATOR, SECRETARY I ^JjL ^T (302)571-7827
AREAWIDE WASTE TREATMENT MANAGEMENT PROGRAM
To Whom It May Concern:
The attached documents represent two partially-edited .draft reports which
have been prepared for the New Castle County, Delaware 208 Program. These draft
reports constitute the'partial fulfillment of the Contractor's assignment in
the area of stormwater management as it relates to non-point source pollution.
Although these documents are still within the internal and advisory review
processes of our 208 Program and although they represent only a portion of the
Contractor's ultimate set of deliverables, the reports are being provided to
EPA Headquarters for distribution to other 208 Agencies who might be contemplating
either a literature review of non-point pollution or an assessment of the state-
of-the-art of available abatement techniques. It is expected that the finalized
reports of the New Castle County, Delaware Stormwater Management Study will also
be submitted to EPA Headquarters for general 208 distribution.
Aside from the fact that the documents are to be considered in rough draft
form, only one other minor caution is advised to the general reader; when the
Contractor initiated his work assignment, he was asked to utilize his discretion
somewhat in the material that he would present. That is, if particular data, a
particular management technique, or particular contamination sources in the
literature had no applicability to New Castle County, Delaware, the Contractor
was at liberty to exclude that information from his reports.
If there are questions regarding the contents of these documents, the reader
may either address them to this Agency or directly to the Contractor. The Con-
tractor's Project Engineer for this assignment is Mr. Gordon Sparks, P.E., c/o
Turner, Collie & Braden, Inc., P.O. Box 13089, Houston, Texas 77019 (1-713-528-
6361).
Paul E. Barker, P.E.
Project Director
PEB/gm
11-17-75
-------
TABLE OF CONTENTS
Title
Page
TEXT
SECTION I INTRODUCTION
SECTION II SOURCES AND CHARACTERISTICS
Atmospheric
Rural Runoff
Forest Land
Rangeland
Cropland
Pastureland
Runoff From Construction Activity
Urban Runoff
Mining Lands
SECTION III SUMMARY AND CONCLUSIONS
Summary
Conclusions
BIBLIOGRAPHY
6
12
15
16
16
16
17
20
35
37
37
38
40
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
TABLES
Comparison of Four Recommended Stream Quality
Standards with Classification Systems
Minimum and Maximum Concentrations of
Selected Particulate Contaminants
Precipitation Characteristics - Concentrations
Precipitation Characteristics - Area Yield Rates
Analyses of Rainfall Samples - Atlanta, Georgia
The Distribution of Chloride in Snow and
Snow Melt as a Function of Sampling Location
7
9
9
10
10
-------
TABLE OF CONTENTS (Cont. )
Title
Page
11
18
22
26
TABLES (Cont. )
Table 7 Distribution of Lead in Snow and in Snow Melt
as a Function of Sampling Locations
Table 8 Summary of Non-Point Source Characteristics
for Rural Land
Table 9 Quantity and Characteristics of Contaminants
found on Street Surfaces
Table 10 Urban Land Drainage and Stormwater Overflow
Characteristics
Table 11 Seasonal Variations (Median Values) for
Bacterial Discharges in Stormwater and
Rainwater from Suburban Areas, Cincinnati,
Ohio, and in Agricultural Land Drainage,
Coshocton, Ohio
Table 12 Average Pollutant Concentrations from Urban
Sub-basins During Storm Flows
Table 13 Summary of the Analytical Results from 15 Test
Areas, Tulsa, Oklahoma
Table 14 Average and Range for BOD, COD, and TOC
in Urban Storm Water Runoff from 15 Test
Areas in Tulsa, Oklahoma, Dates: September 1968
to September 1969
27
30
32
33
-------
STORMWATER QUALITY SUMMARY
SECTION I
INTRODUCTION
The Federal Water Pollution Control Act Amendments of 1972
require the control of point and nonpoint sources of water pollution in
meeting the goals of the Act. Section 208 of the Act encourages that all
activities associated with point and nonpoint source problems be planned
and managed through an integrated areawide waste treatment management
program. One of the first such programs in the country was initiated in
1974 with the designation of New Castle County, Delaware as a 208 area.
It has long been recognized that sanitary sewage discharged from
large urban areas is a significant source of pollution of the nation's waters,
and since the turn of the century, an increasing emphasis has been placed
on the importance of collecting and at least partially treating these
flows. (14) These actions were mainly brought about by public concern
regarding the bacterial nature of the sewage. Disease, heightened by filth
and overcrowding of cities, often caused epidemics that created panic and
paralyzed the city's commerce. (15)
Until recently, concern with regard to pollution of the rivers and
streams has focused only on control of municipal and industrial sources, or
the "point" sources of pollution. Storm water had been ignored as a source
of pollution, probably due to its direct association with rainwater, which
even today is mistakenly assumed to be "pure" by the general public.
-------
An editorial on a Council on Environmental Quality (CEQ) study (27)
revealed that in most cases higher flows resulting from urban runoff did not
"dilute" point source pollution, but caused lower quality than normal flows.
The water quality downstream of the urban areas studied was found to be
controlled by the point sources only 20 percent of the time. Increased
interest in other potential pollution sources has evolved as water pollution
concerns have expanded, to include problems associated with nutrients,
sediment, persistent chemicals, and toxic materials. The remaining
sources of pollution have been grouped into a general category of "non-
point" sources, which are dependent upon rainfall-runoff.
The earliest reported study of the pollutional level of urban storm-
water runoff in the United States was made in 1950 by Palmer.(16,2)
Palmer sampled urban storm water runoff from land surfaces at street
catch basins in downtown Detroit. Although the data were considered to
be limited by Palmer, he felt that the results supported the contention
"that storm water run-off from highly urbanized and highly populated areas
is heavily polluted and would be but slightly less objectionable in the re-
ceiving waters than the run-off flow from combined sewers. " (17) Thus, as
was the case of sewage treatment, concern for the possible pollutional
effects for storm water apparently originated in the city in regard to the
effects of urbanization. Later investigators of the subject concentrated
not only on separate and combined stormwater and sewerage systems in
urban areas, but on semi-urban and rural areas attempting to estimate the
-------
degrees of pollution emanating from, these sources. (14) As mentioned
previously, the dominant consideration has been the bacterial nature re-
garding public health. The presence of large concentrations of coliform
bacteria suggests the potential presence of pathogenic organisms. Another.
matter of concern equally important to public health is the presence of toxic
or other chemical substances entering public water supplies. As far as
stream or lake pollution is concerned, the determination of the amounts of
suspended solids (both volatile and fixed), total solids, the dissolved oxygen
(DO), and biochemical oxygen demand (BOD) concentrations are also im-
portant. (14) In reviewing the literature, the most cited parameters for
determining the quality of stormwater runoff are BOD, suspended solids,
total coliforms, and chemical oxygen demand (COD).
Because of the dependence of a balanced ecosystem upon the mainte-
nance of minimum levels of DO, the BOD has been reported to be the most
valuable single analytical parameter "since it represents the total ultimate
demand that will be made on the oxygen resources of the stream or
lake. "(14) However, it has been recommended that BOD not be considered
appropriate or representative of pollutant strength of urban land runoff due
to inhibitory effects of heavy metals (toxic substances) upon the BOD deter-
mination. Instead, utilizing the COD to estimate the ultimate amount of
organic material susceptible to biodegradation has been suggested. (19)
In considering the possible pollutional effects of the above-mentioned
parameters on water quality, the recommended limits of concentrations for
-------
I
five common parameters were determined by fourU. S. authorities (the Ohio
River Valley Water Sanitation Commission, the Tennessee Valley Authority,
the West Virginia Water Commission, and the Interstate Commission on the
Potomac River Basin) and are shown in Table l.(14, 20)
The term "pollution" is generally associated with man and his activi-
ties affecting the environment. It should be recognized, however, that even
without human activity, a stream is never absolutely pure because of nat-
ural pollution. (2) These natural sources take the form of soil erosion,
decomposition of vegetation and animals, animal wastes, and solution of
minerals.
These nonpoint sources are identified briefly with respect to their
characteristics and requirements for control (1) as follows:
1. Those uncontrollable or not needing control
a. precipitation
b. unmanaged forest land runoff
c. rangeland runoff
2. Those possibly needing control
a. cropland runoff
b. runoff from land receiving manure
c. irrigation return flows
3. Those requiring control
a. urban land runoff
b. manure seepage
c. feedlot runoff
-------
TABLE 1
COMPARISON OF FOUR RECOMMENDED STREAM QUALITY
STANDARDS WITH CLASSIFICATION SYSTEMS (20)
.
Stream Quality
and Uses
Excellent
Recreation
(Bathing);
Water Supplies
(Chlor'n.)
Desirable
Recreation
(Bathing and
Fish Life)
Desirable
Water
Supplies
(Filtration)
Doubtful
Water Supplies
Aux. Treatment;
Recreation; Fish
Life
Unsuitable
Water Supplies;
Recreation; Fish
Life
Standard*
Ohio R. Bas.
T.V.A.
W. Va.
Pot'c. R. Bas.
Ohio R. Bas.
T.V.A.
W. Va.
Pot'c, R. Bas.
Ohio R. Bas.
T.V.A.
W. Va.
Pot'c. R. Bas.
Ohio R. Bas.
T.V.A.
W. Va.
Pot'c. R. Bas.
Ohio R. Bas.
T.V.A.
W. Va.
Pot'c. R. Bas.
Class
AA
1
AA
A
A
II
A
B
A
II
A
B
B
III
B
C
C
IV
C
D
Coliforms
/Ml.
Ave. Max.
0.5
0.5
1.0
0.5
1.0 10.0
5.0 10.0
10.0
5.0 10.0
50.0
50.0
10.0
50.0
200.0
200.0
100.0
Over
200.0
200.0
200.0
D.
O.
(p. p.m.)
Ave.
7.0
7.5
7.5
6.5
7.0
6.0
6.5
6.5
6.5
6.0
6.5
5.0
5.5
4.0
4.0
Under
5.0
5.5
3.0
4.0
Max.
_
6.5
6.5
5.0
5.5
5.0
5.0
5.0
5.0
5.0
5.0
3.0
4.0
3.0
3.0
Under
3.0
4.0
2.0
3.0
5- Day
B.O.D.
(p. p.m.)
Ave.
_
1.0
0.75
-
3.0
1.5
2.5
1.5
3.0
2.0
2.5
2.0
5.0
4.0
6.0
3.0
Over
5.0
4.0
6.0
Max.
2.0
1.0
-
_
3.0
3.5
3.0
_
4.0
3.5
4.0
_
6.0
7.0
5.0
Over
-
6.0
10.0
pH Value
Min.
6.5
6.5
6.3
6.0
6.5
6.5
5.8
6.5
6.5
6.5
5.8
6.0
4.0
5.0
3.8
6.0
Under
4.0
5.0
3.8
6.0
1 1 Id IV/IO
Max. (p.p.b.)
8.6
8.6
7.7 0.0
8.0
8.6 1.0
8.6
9.0 5.0
8.5
8.6 1.0
8.6
9.0 5.0
8.5 -
9.5 10.0
9.5
10.5 25.0
8.5
Over Over
9.5 10.0
9.5
10.5 25.0
8.5
oi
-------
SECTION II
SOURCES AND CHARACTERISTICS
Atmospheric
The pollutants in storm water originate either in the atmosphere or
on the land. Air contaminants exist in the form of particulates and gases.
A substantial amount of air pollution is of natural origin, including weather-
ing, dust storms, tree emissions, forest fires, and volcanic eruptions.
In most areas, however, the significant harmful air pollution is man-made,
resulting from mining, refining, manufacturing, incineration, construction,
and combustion of fuels for electrical power generation, heating, and auto-
motive power. (3)
The five principal categories of air pollutants are sulfur oxide,
nitrogen oxide, hydrocarbons, carbon monoxide, and particulate matter. (3)
The scavenging (wash out) of these pollutants by precipitation is propor-
tional to the rate of precipitation.
Of the total amount of pollutants in the air, suspended particulates
comprise only about one percent by weight when combined with the major
I gaseous pollutants. However, total annual dustfall in urban areas ranges
from 500 to 900 tons per square mile. (3)
A summary analysis of air samples collected by the National Air
! Sampling Network is shown in Table 2.
-------
7
TABLE 2
MINIMUM AND MAXIMUM CONCENTRATIONS
OF SELECTED PARTICULATE CONTAMINANTS (3)
1957 to
(Micrograms per
1961
cubic meter)
Urban
Mean
Suspended particulates 104
Benzene-soluble
Nitrates
Su I fates
Antimony
Bismuth
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Molybdenum
Nickel
Tin
Titanium
Vanadium
Zinc
Radioactivity
organics 7.6
1.7
9.6
*
*
*
0.020
*
0.04
1.5
0.6
0.04
*
0.028
0.03
0.03
*
0.01
4.6t
Maximum Mean
1706.00 27.0
123.90 1.5
24.80
94.00
0.230
0.032
0.170
0.998
0.003
2.50
45.00
6,30
2.60
0.34
0.830
1.00
1.14
1.20
8.40
5435.00t
Nonurban
Maximum
461.0
23.55
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
*Less than minimum detectable quantity.
tPicocuries per cubic meter.
-------
8
Precipitation is a variable and intermittent nonpoint source of
pollutants, but once contaminants are in precipitation, they are uncontrol-
lable. .Tables 3 and 4 present precipitation characteristics both in terms
of concentration units (mg/1) and area yield rates (kg/yr. /ha) as compiled
by Loehr. (1)
A more recent analysis of rainfall was made in Atlanta, Georgia
as presented in Table 5. (4) These data are in close agreement with those
presented by Loehr.
A study of chloride and lead levels in snow and runoffs from snow
melting indicates an ever-increasing problem in Canadian and American
cities. (30) The chloride problem is most acute in those cities where
salting is used to keep roads clear of snow in winter. As shown in Table 6,
the range of chloride in snow and snow melt is from 4 to over 15,000 mg/1.
Although lead contamination is a global problem, the most prominent con-
centrations seem to be associated with roads and streets and, thus, vehi-
cles. Since most of the lead contaminants are associated with suspended
solids, most of the lead levels in snow-dump areas are retained at the site
after the snow is melted. Therefore, in those cities where snow is removed
from streets and transported to dumps, the melting snow would carry only
a small portion of the total lead burden into a watercourse. Table 7 shows
the range of lead in snow and snow melt is from less than 0.1 to over 3, 000
mg/1.
-------
TABLE 3 j
PRECIPITATION CHARACTERISTICS - CONCENTRATIONS (1) i
Concentration under Given Conditions* (mg/l)
1963-64
Constituent Urban1
Nitrogen
'NH4-N
N03-N
Inorganic N* 0.7
Total N 1 .27
Phosphorus
Total PO4-P
Hydrolyzable PO4-P 0.24
Suspended solids 13.0
COD 16.0
Major ions
Ca
Cl
Na
K
Mg
S04
HCO3
196364 Northern 4 yr.
Rural1 Cooper2 Europe3 Forest16-22 Feth5 Ohio6
0.06 0.16 0.17-1.5 1.10
0.14 0.31 0.30 0.56 1.15
0.9 - - - - -
1.17 - - - - - -
- - - 0.008 - 0.02
0.08 - - - - -
11.7 - - - - -
9.0 - - - -
0.65 - 0.21
0.57 - 0.42 - -
- 0.56 - 0.12 -
0.11 - 0.19 -
- 0.14 - 0.16 -
2.18 - 3.10
0 -
Joyner'
0.73
0.04
*Data are primarily yearly averages; numbers in headings refer to references by Loehr.
tlnorganic N = NH4, NO2, and N03-N.
TABLE 4
PRECIPITATION CHARACTERISTICS - AREA YIELD RATES (1)
Constituent
Nitrogen
NH4-N
NO3-N
Suspended
solids
COD
Major ions
Ca
Cl
Na
K
Mg
S04
HC03
Area Yield Data* (kg/yr/ha)
-2 1964-1 965s 1 965-1 9668 -9t 1962-6310
1.6 2.2 - -
1.5 1.5 4.1
100 -
- - 124
7.0 - - - 9.0
6.3 - -
5.9 - - - 25.6
1.4 - - - 3.1
2.1 - - - - .
23.5 30.0 42.7 - -
0 0 - -
"Average U. S. rainfall of 30 in. (76 cm)/yr assumed.
"f Numbers in headings refer to references by Loehr.
-------
10
TABLE 5
ANALYSES OF RAINFALL SAMPLES - ATLANTA, GEORGIA (4)
Rainwater Samples
Date, 1974 COD
August 14
October 15 18
November 5 19
November 11 < 10
November 17 < 10
December 12 < 10
NH3-N
December 12 0.13
BOD5
9
1
4
Kjeldahl-N
0.16
Suspended
Solids
18
4
4
3
1
10
N03-N
0.05
Lead
0.07
0.06
<0.05
P
0.03
Oil and
Grease
-
1.6
TABLE 6
THE DISTRIBUTION OF CHLORIDE IN SNOW AND SNOW MELT
AS A FUNCTION OF SAMPLING LOCATION (30)
Location
Number of Samples
Range of Chloride Levels
(mg/l)
Mean Chloride Level
(mg/l)
Snow dumps
Commercial street
Industrial street
Residential street
Roof samples
Snow dump runoff
Storm sewer runoff
Raw wastewater
Treated wastewater
Rideau River
Ottawa River
134
41
6
9
5
36
53
5
10
54
61
4-2,500
4-15,266
143-2,448
154-8,151
0-3
16-4,397
11-1,163
84-332
88-363
8-57
6-21
464
3,233
1,703
2,283
0.6
500
219
162
200
19
9
-------
TABLE 7
THE DISTRIBUTION OF LEAD IN SNOW AND IN SNOW MELT
AS A FUNCTION OF SAMPLING LOCATIONS (30)
Location
Snow dumps
Major highway
Commercial street
Industrial street
Residential street
Roof samples
Snow dump runoff
Storm sewer runoff
Raw wastewater
Treated wastewater
River
Number of
Samples
149
3
41
6
9
7
39
50
5
13
8
Filtrate
0.052
0.060
0.042
0.048
0.014
0.041
0.009
0.007
0.026
0.027
0.006
Mean Lead Level
(mg/l)
Paniculate
555
3,287
822
935
1,228
-
1,322
1,791
479
448
69*
Range of Lead Levels
for Total Sample
Total Sample
4.8
102.0
3.7
4.7
2.0
0.10
0.11
0.13
0.09
0.06
o.ost
(mg/l)
0.02 -
86.00 -1
0.02 -
0.06 -
0.12 -
0.02 -
0.004-
0.002-
0.05 -
0.003-
0.004-
50.0
13.0
11.3
14.3
10.2
0.25
0.51
1.19
0.16
0.14
0.046
*Value for river bed sediments (22 samples).
^ Calculated using lead levels in transported sediment (average 494 ppm) as opposed to river sediments.
-------
12
Rural Runoff
The characteristics of runoff from rural and agricultural lands are
related to the use of the land, soil characteristics, material both present
in and added to the land, and rainfall intensity. The parameter of most
concern when considering runoff from rural and agricultural land is sedi-
ment. Soil conservation to avoid loss of valuable topsoil and to minimize
problems resulting from sediment (suspended solids) deposition is a world-
wide goal. (5) Additional concern for sediment has developed with respect
to its oxygen-demanding materials which reduce dissolved oxygen concen-
tration, and its nutrient content which can cause eutrophic problems. The
major problem of excessive nutrients is the stimulation of the growth of
algae and other aquatic plants in lakes and streams. (6)
Constituents contained in runoff from rural land originate in rain-
fall, wastes from wildlife, leaf and plant residue decay, applied nutrients,
herbicides and pesticides, nutrients and organic matter initially in the
soil, and wastes from pastured animals. (1) Organic and inorganic con-
stituents are released at varying rates from all soils and geologic forma-
tions. The natural weathering of rocks and minerals and the oxidation and
leaching of organic matter contribute "pollutants" to runoff even in the
absence of human activity. The nutrients most commonly referred to in the
literature regarding rural runoff are nitrogen and phosphorus. The levels
of these nutrients are generally considered the most critical in terms of
-------
13
supporting algal blooms. One example of a critical level for these nutri-
ents in this respect is 0. 30 mg/1 for inorganic nitrogen and 0. 01 mg/1 for
inorganic phosphorus. (6)
Water pollutants from nonpoint sources can reach a body of water in
two ways. They can either be dissolved or suspended in surface runoff or
they can percolate into subsoil and reach streams or lakes through sub-
surface movement. Pollutant generation and transport in this respect
are dependent upon rainfall/runoff relations of storms. Pollutants can also
adhere to soil particles and be eroded from the land. In this respect,
movement of pollutants is strongly correlated with sediment generation and
transport. (7)
Nitrogen is involved in a very complex cycle and exists in several
chemical forms which differ substantially in properties. Some forms are
highly soluble in water, and nitrate, in particular, is subject to leaching
and movement into subsurface waters.
Phosphorus is usually found in an insoluble form and it is trans-
ported principally on sediment. (13) Thus, if the phosphorus content of
eroding soils is known and data are sufficient to calculate sediment yield,
phosphorus emissions can be calculated. Similarly, emissions of insoluble
forms of nitrogen can be calculated as a multiple of sediment emissions.
For small areas, nitrogen and phosphorus concentrations in soils can be
accurately determined. However, for large areas such as river basins,
data on such concentrations will probably be inadequate. A sampling and
-------
14
analysis program will generally be both too time consuming and costly for
planning efforts; thus, generalized data will have to be used. (8)
The mechanisms of sediment generation from soil surfaces have
been capsulized in the Universal Soil Loss Equation. A variety of data
on rainfall, topography, soil characteristics, crop and ground cover
characteristics, and mechanical practices of agriculture have been col-
lected by the Soil Conservation Service, USDA, for estimating yields of
sediment with this equation throughout the United States. However, the
Universal Soil Loss Equation deals only with "on-site" erosion and lacks
a delivery term to relate the quantity of on-site eroded sediment to the
quantity delivered to surface streams. (8)
In terms of volume, sediment ranks above sewage, industrial wastes,
and chemical pollution combined. On an annual basis, sediment is usually
j| over 90 percent of the pollutant load carried by most streams, and 95 per-
! cent of that sediment is from nonurban sources.(9) For the nation as a
li
i whole, the sources of sediment, ranked in decreasing magnitude of impact
i
j on streams, are as follows: a) agricultural tillage, b) grazing, c) highway
| construction and maintenance, d) timbering, e) mining, f) urban land
i
i development, and g) recreation land development. (10)
II
Crop fertilizers have been blamed as a major contributor to nutri-
ents in surface waters. Generally, only 5 to 10 percent of the fertilizer
phosphorus added to a soil is taken up by the following crop. The remain-
I ing applied phosphorus is converted to insoluble forms and may become
(
a source of available phosphorus for crops in subsequent years. On the
-------
15
average, no more than 50 percent of the applied nitrogen in fertilizer is
recovered by crops, although grass may recover 80 percent or more of the
applied nitrogen. (1)
1. Forest Land
Nearly 500 million acres in the United States are in forests
managed primarily for the production of timber. (11) A well-managed
forest with a good stand of trees is usually quite resistant to erosion and
absorbs incident rainfall, which reduces runoff. Therefore, the runoff from
these areas may serve as one of the better indicators of constituents that
result from natural conditions. (1,12) However, the runoff from forest
areas can contain organic matter ranging from green vegetation to well-
decomposed humic matter containing high concentrations of nutrients and
oxygen-demanding materials.
The increased demand for wood fiber has accelerated cultural
production practices in managed forested areas. Forest management prac-
tices such as forest fertilization and block cutting of mature trees will alter
the characteristics of runoff from forested areas. Soil disturbed by tree
harvesting, skidding logs to a landing area, and construction of roads to
haul logs from a forest is highly erodible and is the major source of sedi-
ment, which is the principal pollutant from these areas. (11)
Nutrient problems caused by forest fertilization do not appear to
be serious under current conditions and practices. (1)
-------
16
2. Rangeland
Where rainfall is sparse or where the land is not very fertile,
intensive crop production is not possible and few animals can be supported
per acre of land. This rangeland, with low domestic animal and human
density and low fertilized acreage, represents a near natural situation.
Therefore, runoff from these lands would contain background or natural
constituents. (1)
3. Cropland
Cropland includes orchards, grassland, idle farm land, and
land used for production of grains and vegetables. Runoff from cropland
has characteristics different from that of rangeland, since cropland is
under direct human management.
The soil of many farms has poor drainage characteristics, and
subsurface tile or other type drains can be installed to permit better water
movement and crop yields. The surface and subsurface irrigation drains
discharge to surface waters at diverse points and constitute a part of irri-
gation return flow. (1) Chemical constituent concentrations increase in
runoff waters during surface irrigation because of incorporation of undis-
solved fertilizer particles in the irrigation stream or by erosion of soil
particles having attached fertilizer ions. (13)
4. Pastur eland
Pasturelands usually contain animals for production, and runoff
from these lands contains contaminants from animal wastes. Animal wastes
-------
17
are a major potential source of water quality degradation. Runoff from
barnyards, feedlots, and pastureland may contaminate water supplies,
destroy fish and aquatic life in streams, and generally degrade water
quality. Nitrate in groundwater and ammonia in the air in the vicinity of
feedlots have been shown to be significantly higher in concentration than at
remote locations. However, the extent of pollution from animal production
is more dependent upon waste management methods than on volume of waste
involved. (12,1)
A summary of nonpoint source pollution characteristics for
rural land as compiled by Loehr (1) is presented in Table 8.
Runoff From Construction Activity
Each year the construction of highways, dams, power plants, housing
developments, and other activities use up more than one million acres of
land in the United States, some of which had been utilized previously for the
production of crops, timber, water recharge, wildlife, recreation, and
other continuing needs. As man continues to alter the soil, water, and other
natural resources at an increasing rate, the possible pollutional effects of
his actions also increase. (21)
Except for some cases, natural erosion is a very slow process.
Since this process has occurred at a slow and relatively uniform rate over
thousands of years, natural erosion does not to any large extent create en-
vironmental problems. In fact, the sediment derived from such erosion is
an essential ingredient in the balance of the environment. (21) An excellent
-------
TABLE 8
SUMMARY OF NON-POINT SOURCE CHARACTERISTICS FOR RURAL LAND* (1)
Source
Irrigation tile drainage,
western U.S.
Surface flow
Subsurface drainage
Crop land tile drainage
Seepage from stacked
manure
Feedlot runoff
COD
Concentration (mg/l)
Area Yield Rate (kg/yr/ha)
BOD
NO3-N Total N Total P COD BOD NO3-N
Total N
Total P
Surface Area of Interest
Forested land
Range land
Agricultural crop land 80
Land receiving manure
0.1 - 1.3 0.3 - 1.8
_ _ _
7 0.4 9
_ _
0.01-0.11
- -
0.02-1.7
_ _
0.7-8.8
0.7
_
- -
3.0-13
-
0.1-13
4.0-13
0.03- 0.9
0.08
0.06- 2.9
0.8 - 2.9
Forest area
Range land
Active crop land
Crop or unused land used
25,900-31,500 10,300-13,800
3,100-41,000 1,000-11,000
0.4 - 1.5 0.6 - 2.2 0.2 -0.4
1.8 -19.0 2.1 -19.0 0.1 -0.3
10-25 0.02-0.7
1,800-2,350 190-280
10-23 920-2,100 290-360
83
for manure disposal
3.0-27 1.0 - 4.4 Irrigated western soils
42.0-186 3.0-10.0 Irrigated western soils
0.3-13 0.01- 0.3 Active crop land requiring
drainage
7,200 1,560
100-1,600 10-620
Manure holding area
Confined, unenclosed
animal holding areas
"Data do not reflect the extreme ranges caused by improper waste management or extreme storm conditions; the data represent the range of average values reported in previous tables.
OO
-------
19
example of man's altering natural erosion and sedimentation is Egypt's
Aswan High Dam. The dam changed the Lower Nile from a turbid stream
into a clear one with smaller peak annual flows. Agricultural lands that
were productive for thousands of years no longer are flooded each year,
with consequent deposits of sediment rich in nutrients. Further, the Nile's
discharge into the Mediterranean Sea no longer provides nutrients essential
for sea life. (10)
Water-generated sediment, however, can become a serious problem
when natural vegetation is destroyed by man's activities. These activities
include exposing the soil surface, altering drainage patterns, and covering
permeable soil surfaces with impermeable structures. All of these factors
greatly accelerate the overall rate of erosion, commonly referred to as
"accelerated erosion. " Such erosion is reported to produce about 70 per-
cent of all sediment generated in the country. (21)
Accelerated water erosion can be divided into three major categories:
overland erosion, stream channel, erosion, and shore erosion. The sever-
ity of erosion is influenced by four major physical factors: climate,
vegetative cover, soil, and topography.
Potential pollutants other than sediment associated with construction
activity include pesticides, petrochemicals (oil, gasoline, and asphalt),
solid wastes, construction chemicals, wastewater, garbage, cement, lime,
sanitary wastes, and fertilizers. The amount of sediment generated from a
construction site will apparently have to be determined on a case basis by
utilizing the Universal Soil Loss Equation. Other pollutants associated with
-------
20
runoff from construction sites would have to then be estimated as a portion
of total sediment transported. (21)
Urban Runoff
Most of the urban areas of the United States have separate sewer
systems. Many of the older large cities have combined sewers, or a mix-
ture of combined and separate sewers. Although the areas contributing
urban runoff represent only a little over one percent of the total area of the
country (22), most of the literature on stormwater runoff concerns the
urban area source.
The sources of contaminants in urban runoff include street litter,
gasoline combustion products, ice control chemicals, rubber and metal lost
from vehicles, decaying vegetation, domestic pet wastes, fallout from
industrial and residential combustion products, overflows from sanitary
sewers, and chemicals applied to lawns and parks.(1, 26) A 1969 report
by the American Public Works Association (3) summarized a study to deter-
mine the factors in the urban environment which contribute to the pollution
of urban stormwater runoff. Street litter was found to be the major source
of pollution, having as its most significant components dust and dirt. Catch
basins were found to be one of the most important single sources of initial
shock loading or "first flush" loading upon a stream, due mainly to the an-
i aerobic conditions which exist in such facilities between storms. Other
potential sources of pollution considered included air pollution, roof dis-
charges, and chemicals used in the urban environment. A separate study
-------
21
was undertaken (26) to investigate the pollution aspects of street surfaces
in 12 cities in the United States, representing some 25,000 curb miles of
streets. The conventional parameters of water pollution considered in-
cluded total solids, volatile solids, BOD, COD, Kjeldahl nitrogen, and
soluble nitrates and phosphates. Also included were less common param-
eters such as heavy metals, including chromium, copper, zinc, nickel,
mercury, lead, and cadmium, and the chlorinated hydrocarbon and organic
phosphate compounds generally associated with pesticides.
Additional studies were conducted concerning the presence of total
and fecal coliform bacteria on the streets. The quantity and character of
the various contaminants found on the street surfaces are summarized in
Table 9 by pounds per curb mile.
One of the most important findings of the study was that a great
portion of the overall pollution potential is associated with the fine solids
(<43/4) fraction of the street surface contaminants (5. 9 percent of the total
solids). About one-fourth of the oxygen demand and one-half of the algal
nutrients were associated with this fine fraction. It also accounted for over
one-half of the heavy metals and three-fourths of the pesticides. The
significance of these data lies in the fact that conventional street-sweeping
operations are rather ineffective in removing fines (only 25 percent of the
material <43/J»). Of further significance along these lines is the fact that
catch basins were reported to be ineffective in removing fine solids and
organic matter.
-------
22
TABLE 9
QUANTITY AND CHARACTERISTICS OF
CONTAMINANTS FOUND ON
STREET SURFACES (26)
Weighted Means
for All Samples
Measured Constituents (Ib/curb mile)
TS 1.400
Oxygen demand
BOD5 13.5
COD 95
VS 100
Algal nutrients
Phosphates 1.1
Nitrates 0.094
Kjeldahl Nitrogen 2.2
Heavy metals
Zinc 0.65
Copper 0.20
Lead 0.57
Nickel 0.05
Mercury 0.073
Chromium 0.11
Pesticides
p,p-DDD 67X10"6
p.p-DDT 61 X 10~6
Dieldrin 24 X 10~6
PCB 1,100X10"
Bacteriological
Total coliforms*
(organisms/curb mile) 99 X 10
Fecal coliforms*
(organisms/curb mile) 5.6X10
*Number of observed organisms/mile.
Note: Lb. X 0.454 = kg; mile X 1.61 = km.
6
-------
The principal factors affecting the loading intensity at any given site
included surrounding land use, the elapsed time since streets were last
cleaned (either by sweeping or flushing or by rainfall), local traffic volume
and character, street surface type and condition, and season of the year.
Most of the literature reports data on separate storrnwater pollutants
in terms of concentrations (i. e., mg/1) or area yield rates (i.e.,
kg/ha/yr). The published data usually fail to relate specific pollutants to
watershed characteristics, sanitary conditions, land use, or rainfall. As
a result, many parameters vary by two or more orders of magnitude from
city to city. (2)
As mentioned previously, Palmer sampled storrnwater runoff from
the urban area of Detroit in 1949. (16) He also reported additional samp-
lings of several storms from Detroit in 1960. (17) The range of values he
reported for the 1949 data for BOD was 96 to 234 mg/1, for total solids
310 to 914, and. for total coliform MPN's/100 ml 25, 000 to 930, 000. (16)
The range of values for the 1960 data was MPN's from 2, 300 to 430, 000
and mean suspended solids from 102 to 213 mg/1. The concentrations of
the pollutants varied widely with time and location, with no apparent pat-
tern between storms.
In 1954, a study of surface runoff from a housing estate in England
indicated BOD concentrations up to 100 mg/1 and suspended solids up to
2045 mg/1. A reference to this report by V/eibel, et al (22) revealed that
the BOD concentrations tended to increase with length of antecedent dry-
weather periods up to 8 to 10 days. However, in a study of 36 storms in
-------
24
Durham, North Carolina, "the time since the last storm was not found to be
a significant factor affecting the quality of urban, land runoff". (19) The
pollutant concentrations during the first part of the storm were typically
higher than those during the remainder of the storm for this study, indicat-
ing a first-flush effect. This first-flush effect has also been reported by
others. (18, 22, 14)
A study of stormwater runoff from a 27-acre residential and light-
commercial urban area in Cincinnati, Ohio in 1962 and 1963 (22) indicated
average concentrations of 19 and 99 mg/1 for BOD and COD, respectively,
with suspended solids averaging 210 mg/1.
The constituents in the runoff were also examined with respect to
seasonal variation, but no parameter exhibited any pronounced change.
There was no relationship evident between antecedent interval and runoff
pollutants. Cleveland (2) also found the pollutional parameters to remain
fairly constant throughout the year.
A 1965 study by Burm, et al (24) determined chemical and physical
qualities of the separate and combined systems cf the Detroit-Ann Arbor
area. The City of Ann Arbor has a separate stormwater system serving
approximately 3,800 acres of largely residential and commercial develop-
ment with some rural drainage entering the system. Annual mean values
for BOD and suspended solids were 28 and 2080 mg/1, respectively.
Although BOD did not vary from season to season, a "first-flush" effect
was noticed in this parameter. This first-flush phenomenon was not exist-
ent for the suspended solids. High suspended solids concentrations were
-------
25
attributed to the erosion due to the high average land slopes in the Ann
Arbor area and the loose texture of the soil.
The chemical and biochemical characteristics of urban runoff re-
corded in a number of studies, including those referenced in this paper, as
compiled by Loehr (1) are presented in Table 10.
The bacteriological characteristics of stormwater pollution are of
equal concern with respect to pollution of streams and lakes as physical,
chemical, and biochemical characteristics due to their direct public health
aspects. Total and fecal coliforms have been traditionally used to indicate
possible pathogenic contamination. (18) Geldreich, et al (25) performed an
extensive bacterial analysis of storm water in Coshocton, Ohio. Storm
water was examined from city streets, a suburban business district storm
drain, a wooded hillside adjacent to a city park, and cultivated farm fields.
. The various indicator organisms exhibited seasonal variations in densities,
as shown in Table 11. Tests also indicated that rainwater contained insig-
nificant bacterial contamination, and the major contamination of this water
source must occur on contact with the polluted land environment. The
fecal coliform to fecal streptococcus ratios were always below 0. 7, indi-
cating fecal pollution by warmblooded animals other than man. Such
animals were believed to be animal pets, particularly dogs and cats, plus a
substantial rodent population, all of which would likely be found in an urban
community. Similar bacterial data were also reported by Weibel, et al (22)
for an urban area in Cincinnati. Fecal coliforms found in stor-m water in
-------
TABLE 10
URBAN LAND DRAINAGE AND STORMWATER OVERFLOW CHARACTERISTICS* (1)
Item and Location
Concentration (mg/l)
Cincinnati, Ohio
Seattle, Wash.
Tulsa, Okla.
East Bay Sanitary District,
Calif.
Los Angeles County, Calif.
Washington, D. C.
Total Solids
~
545
(200-2,240)
1,400
2,910
Suspended
Solids
227
(5-1,200)
367
(84-2,050)
1,400
_
2,100
(26-36,200)
COD
111
(20-610)
85
(42-138)
_
BOD TKN N03-N Total N Soluble P Total P
17 3.1 - 1.1
(1-173) (0.3-75) (0-7.3)
2.0 0.53 - 0.08 0.21
12 0.9t - - 0.38
(8-18) (0.4-1.5) (0.18-1.2)
87
(3-7,700)
160
126
(6-625)
Cl
_
12
(2-46)
5,100
200
42
(11-160)
Reference
(to Loehr)
1
(1962-64)
22
48
49
49
49
Detroit, Mich.
Madison, Wis.
Durham, N. C.
Russia
Rainwater runoff
Street washing water
Melting snow
Moscow
Leningrad
Stockholm
Area yield rate (kg/yr/ha)
Cincinnati
Stormwater runoff
Combined sewer overflow
(310-910)
2,730
(274-13,800)
(1,000-3,500)
14,500
(30-8,000)
(102-210)
(20-340)
(450-5,000)
(31-14,500)
(570-4,950)
640
280
179
(40-600)
310
(96-234)
15
(2-232)
(12-145)
(6-220)
(5-105)
(186-285)
36
(17-80)
47
(0.4-2.0)
_
~
8.8
6.8
_ _
(0.2-1.8) (0.5-4.0)
0.6
(0.15-2.50)
_ _
_
"
1.1
5.6
1.0
_
13
(3-390)
(6-32)
(11-17)
(6-58)
_
49
50
51
(1968-70)
52
52
52
49
49
49
9
9
48
Tulsa, Okla.
Detroit, Mich, (kg/ha)
Ann Arbor, Mich, (kg/ha)
Rock Creek (Potomac),
Washington, D. C.
Durham, N. C. (1968-70)
Stockholm, Sweden
Highway runoff
Terrace house runoff
Residential block runoff
"Average characteristics, range of
tOrganic N.
$NO2 + N03-N.
1,400
(550-5,700)
14,200
2,040
470
930
values shown
220
1,230
1,185
173
620
in parentheses.
220 30 2.1
(67-530) (13-54) (1.2-4.0)
100 8.8 0.2
35 1.2 0.9
2.9 12 J
93 75 -
100
14 _
43
1.0
(0.4-3.0)
2.1 4.0
0.3 1 .0
1.6
3.0
5.1 - 0.2
1 .4 - 0.04
3.5 - 0.16
48
53 (June-
Aug. 1965)
53
23 (60% urban,
30% farm)
51
54
54
54
ts)
-------
TABLE 11
SEASONAL VARIATIONS (MEDIAN VALUES) FOR BACTERIAL DISCHARGES IN STORMWATER
AND RAINWATER FROM SUBURBAN AREAS, CINCINNATI, OHIO, AND IN
AGRICULTURAL LAND DRAINAGE, COSHOCTON, OHIO
Total
Source Date Samples Season
Wooded hillside Feb. 62 to Dec. 64 278
Spring
Summer
Autumn
Winter
Street gutters Jan. 62 to Jan. 64 1 77
Spring
Summer
Autumn
Winter
Business district Apr. 62 to Jul. 66 294
Spring
Summer
Autumn
Winter
Rural Jan. 63 to Aug. 64 94
Spring
. Summer
Autumn
Winter
Rainwater Jun. 65 to Feb. 67 49
Spring
Summer
Autumn
Winter
Total
Coliform
2,400
79,000
180,000
260
1,400
90,000
290,000
1,600
22,000
172,000
190,000
46,000
4,400
29,000
18,000
58,000
<1.0
<1.0
<0.4
<0.8
Fecal
Coliform
190
1,900
430
20
230
6,400
47,000
50
2,500
13,000
40,000
4,300
55
2,700
210
9,000
<0.3
<0.7
<0.4
<0.5
(25)
Fecal
Streptococcus
940
27,000
13,000
950
3,100
150,000
140,000
2,200
13,000
51,000
56,000
28,000
3,600
58,000
2,100
790,000
< 1.0
< 1.0
<0.4
<0.5
Ratio
FC/FS
0.20
0.70
0.03
0.02
0.07
0.04
0.34
0.02
0.19
0.26
0.71
0.15
0.02
0.05
0.10
0.01
-
-
-
Percent
Fecal
Coliform
7.9
2.4
0.2
7.7
16.4
7.1
16.2
3.1
11.4
7.6
21.1
9.4
1.3
9.3
1.2
15.5
-
-
-
ts)
-J
-------
28
Atlanta (4) were also believed to have their origin predominantly from dogs
and other animals.
Bacterial counts in 50 percent of the samples for the Cincinnati study
(22) reported total coliforms, fecal coliforms, and fecal streptococci as
58,000, 10,900, and 20,500, respectively, thus indicating a predominately
non-human source.
A 1963-1964 study by Burm, et al (23) dealt with bacteriological
characteristics of combined and separate storm sewer discharges in the
Detroit-Ann Arbor area. One conclusion of the study was that bacterial
quality did not appear to be related to storm intensity, duration, or total
rainfall, either in separate or combined systems.
Since storm water can apparently be a major source of intermittent
pollution to bathing beaches and water supplies, the bacteriological charac-
teristics will have to be considered along with the other characteristics.
Considerations will range from prohibition of domestic animals from public
and water supply areas to diversion or treatment of storm discharges en-
tering such areas.
Up until fairly recently the water quality data reported in the litera-
ture were no more than unrelated pieces of data. As the importance of
I
storm water became of increasing concern and more complex models were
devised to attempt to closely estimate such pollutional aspects, more de-
tailed data relating to rainfall and watershed characteristics were
developed.
-------
29
One such study was made in 1972 in Durham, North Carolina. (19)
According to the author, the results contained in the report are believed
to represent urban areas of the Piedmont province on the East Coast.
Thirty-six separate runoff events were sampled, resulting in 521 separate
samples for six sub-basins representing a variety of urban land-use class-
ifications. It was concluded that the individual sub-basins did not exhibit
significant variations in urban runoff quality to indicate influence of land use
on quality of urban runoff (for the three parameters of COD, TOC, and BOD).
In order to relate pollutant yield to runoff characteristics, the variables
of runoff rate, time from storm start, time from last storm, and time from
last peak were investigated. It was found that rate of discharge and time
from storm start were the most significant. Apparently the frequency of
runoff described by the two remaining variables did not significantly in-
fluence pollutant discharge. A summary of the average pollutant concentra-
tions for five of the sub-basins is presented in Table 12. Sub-basins W-l,
W-2, and E-l are primarily residential areas and portions of N-2 and
E-2 are undergoing urban renewal. Sub-basin N-2 is primarily composed
of a portion of the downtown business district, including light to heavy
industry and an expressway. Sub-basins E-l, E-2, and W-l essentially
contain no industry, business, or commercial property.
A study in Tulsa, Oklahoma (28) attempted to relate runoff charac-
teristics to land use in fifteen test areas, each with a predominant land
activity. The areas were carefully selected as to land use, ground cover,
-------
TABLE 12
AVERAGE POLLUTANT CONCENTRATIONS FROM URBAN
SUB-BASINS DURING STORM FLOWS (19)
(DURHAM, N.C.)
Sub-basin
Organics (mg/l)
Nutrients (mg/l)
Total
COD
TOC
BOD5
K-N
P
Fecal Coliforms ( #/ml)
Solids (mg/l) -
Metals (mg/l) -
Total
TVS
SS
VSS
Al
Ca
Co
Cr
Cu
Fe
Mg
Mn
Ni
Pb
Sr
Zn
E-1
93
30
60
0.36
0.50
540
834
202
627
102
27
2.2
<0.1
0.13
0.11
10
16
0.84
<0.1
0.26
<0.1
0.22
E-2
130
32
69
0.44
0.53
185
849
156
638
80
23
4.1
0.1
0.15
0.13
6
10
0.49
<0.1
0.13
<0.1
0.32
N-2
102
30
83
0.57
0.59
50
977
133
770
99
22
1.6
<0.1
0.16
0.12
5
10
0.51
<0.1
0.32
<0.1
0.27
W-1
95
35
36
0.42
0.54
242
819
132
629
87
18
1.8
<0.1
0.13
0.10
10
7.5
1.1
<0.1
0.27
<0.1
0.32
W-2
101
32
81
0.31
0.57
265
938
134
739
142
23
2.0
<0.1
0.15
0.12
13
11
0.52
<0.1
0.25
0.11
0.23
30
Total
Basin
170
42
0.96
0.82
230
1440
205
1223
122
16
4.8
0.16
0.23
0.15
12
10
0.67
0.15
0.46
0.36
-------
31
type of industries, physical conditions of drainage systems, and environ-
mental conditions which include such things as exterior housing quality,
water supply and wastewater disposal, refuse storage, and presence of
livestock and domestic animals. Table 13 summarizes the pollution
parameters measured on the fifteen watersheds, while Table 14 sum-
marizes the average and range for the organic pollutants for each of the
fifteen areas.
The results of the study indicated that coliforms, BOD, organic
nitrogen, orthophosphate, and solids varied not only between different land
uses but between different areas of identical land-use classification. By
comparing BOD/COD and TOG/COD ratios, it was concluded that the stand-
ard COD test did not measure certain organic materials such as straight-
chain aliphatic compounds, aromatic hydrocarbons, and pyridine.
It was concluded that land surface characteristics which influence
drainage, environmental conditions, and degree of development (i.e.,
amount and type of streets and storm sewers) affect the amounts of pol-
lutant concentrations more than specific land-use types. It was also dis-
covered that most pollutant concentrations decreased with time since the
start of the current precipitation and since the antecedent event. The
bacterial and total solids concentrations increased with the average inten-
sity of the current precipitation event.
A study performed in Lincoln, Nebraska (29) had as its purpose to
obtain data on the pollutant concentration versus duration of rainfall. Three
residential areas were sampled having single and some multi-family land
-------
32
TABLE 13
SUMMARY OF THE ANALYTICAL RESULTS
FROM 15 TEST AREAS, TULSA, OKLAHOMA (28)
Parameter
Mean of the
Test Areas
Range of the Test
Area Means
Bacterial (number/100 ml)1
Total coliform
Fecal coliform
Fecal streptococcus
Organic (mg/l)
BOD
COD
TOG
87,000
420
6,000
11.8
85.5
31.8
5,000-400,000
10- 18,000
700- 30,000
8- 18
42-138
15- 48
Nutrients (mg/l)
Organic Kjeldahl nitrogen
Soluble orthophosphate
Solids (mg/l)
Total
Suspended
Dissolved
0.85
1.15
545
367
178
0.36-1.48
0.54-3.49
199-2,242
84-2,052
89- 400
Other Parameters
pH
Chloride (mg/l)
Specific conductance
(micromhos/cm)
7.4
11.5
108
6.8-8.4
2-46
36-220
"Geometric mean.
-------
TABLE 14
AVERAGE AND RANGE FOR BOD, COD, AND TOC IN URBAN STORM WATER
RUNOFF FROM 15 TEST AREAS IN TULSA, OKLAHOMA
DATES: SEPTEMBER 1968 TO SEPTEMBER 1969 (28)
Test
Area
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
BOD (mg/l)
Classification
Light Industrial
Commercial-Retail
Residential
Med. Ind. Residential
Residential
Medium Industrial
Residential
Residential
Residential
Commercial (Office)
Residential Com. Mix.
Open Land Runways
Residential
Recreation (Golf)
Residential
Min.
3
2
2
4
3
6
2
3
4
4
4
6
4
6
1
Avg.
13
8
8
14
18
12
8
15
10
11
14
8
15
11
12
Max.
23
16
21
29
38
18
17
25
15
27
23
16
39
23
24
Min.
54
21
20
14
37
39
12
50
40
36
80
21
13
22
18
COD (mg/l)
Avg.
110
45
65
103
138
90
48
115
117
107
116
45
88
53
42
Max.
215
94
162
232
261
133
69
405
263
240
167
69
220
74
62
Min.
17
12
14
22
11
12
0
5
13
0
17
6
17
18
11
TOC (mg/l)
Avg.
43
22
22
42
48
34
15
37
35
28
33
20
35
29
34
Max.
71
36
31
74
85
42
20
82
61
80
49
40
66
36
75
UJ
OJ
-------
34
use ranging in age from new to 20 years old. Population density ranged
from 7.9 to 11.3 persons per acre for the 79, 85, and 375-acre subareas.
All three areas are apparently drained by curb-and-gutter streets with
storm sewers.
A variety of rainfall intensities and durations were recorded during
the five-month study period, as well as antecedent dry periods. On
numerous occasions, parameters being sampled reached a high concentra-
tion in the initial runoff, followed by a sudden dropoff, then followed some
time later by a second peak concentration. This double first-flush effect
was believed to be caused from stagnant pools in drainage channels left by
antecedent rainfall.
Due to the limited data and duration of the study, no conclusions were
drawn on the effects of seasons or antecedent dry periods. There was an
indication, however, that the intensity and duration of a preceding storm
may have a considerable effect on the washoff of a pollutant in a later
storm. Also, when the total quantity of a pollutant loading (i. e., COD and
SS) in pounds for a given rainfall was plotted against the total rainfall (in
inches) a straight-line relationship on semi-log graph paper is indicated.
Similar relationships were reported for BOD and suspended solids versus
total rainfall per storm by Weibel, et al. (22)
A study performed at Purdue University (18) investigated the quality
of stormwater runoff from two watersheds. One, an urban area of 29
acres, included a fully-developed residential area with 8. 7 persons per
acre. The second watershed was a semi-urban rural area of 292 acres
-------
35
four miles north of the university campus. This partially-developed resi-
dential area has 178 acres residential and 114 acres farmland, having a
combined density of 3. 4 persons per acre.
A first-flush of suspended solids and BOD was exhibited for the
urban area but not for the other area. In order to compare the two water-
sheds, the unit "pounds per day per acre - MGD" was used to reduce the
stormwater quality data from the two areas to a comparable basis.
The urban area had BOD values ranging from 7 to 24 Ib/day/acre -
mgd and suspended solids ranging from 2 to 8 Ib/day/acre - mgd. The
semi-urban/rural area had BOD and suspended solids ranging from 0. 07
to 0.14 and 0.14 to 4. 3 Ib/day/acre - mgd respectively.
As was the case with the Lincoln, Nebraska study, several subse-
quent flushes of suspended solids occurred after the initial flush when flow
increased dramatically. However, upon reaching maximum flow, solids
concentrations decreased and remained constant. This was reported to
imply that a minimum flow is required to completely flush the solids from
the basin.
Mining Lands
The only apparent activity related to mining in New Castle County,
Delaware is clay produced for the Delaware Brick Co. from one area just
south of New Castle, arid six sand and gravel companies, of which only the
sand and gravel operations will be assumed significant.
-------
36
Storm water and plant process water are the two main sources of
water pollution associated with sand and gravel production. The pollution
impact is chiefly from the sediment load, ranging in concentration from
several hundred to several thousand mg/1. Three different methods of
sand and gravel excavation are practiced: 1) dry pit, sand and gravel are
removed above the water table; 2) wet pit, raw material is extracted by
means of a dragline or barge-mounted dredging equipment both above and
below the water table; and 3) dredging, sand and gravel are recovered
from public waterways including lakes, rivers, estuaries, and oceans.
All methods require about 600 gallons of water per ton of product (32),
and when applied to the number of tons produced in Delaware (i. e.,
2,205 thousand short tons in 1971) on a yearly basis, over a billion gal-
lons of such wastewater could enter the streams and estuaries of the
state.(33)
In a state-of-the-art summary of the sand and gravel industry (32),
the detrimental effects of sediment ranged from algae, generally the most
basic member of the food chain, through the higher life forms of fish.
Although a precise minimum concentration of inorganic solids (such as
emitted from sand and gravel operations) which is detrimental to maintain-
ing good fisheries has not been established, the suspended solids concen-
trations listed below are believed meaningful approximations:
Concentration Effect on Fish
0-25 ppm No harmful effect on fisheries
25-100 Good to moderate fisheries
100-400 Unlikely to support good fisheries
400 and above Poor fisheries
-------
37
SECTION in
SUMMARY AND CONCLUSIONS
Summary
In reviewing the literature on stormwater runoff characteristics,
there is no doubt as to its potential significance as a source of water pollu-
tion to lakes and streams. The quality of runoff varies from relatively
"pure," similar to uncontaminated precipitation, to a septic or toxic condi-
tion capable of destroying fish and wildlife as well as having unknown
detrimental effects upon humans when ingested either directly or indirectly
through contamination of domestic water supplies.
The factors which influence the quality of rainfall runoffs are as
numerous as the physical and chemical characteristics which describe the
environmento Almost all studies referring to hydrological effects agree
that rainfall duration, intensity, and frequency definitely affect the quality
of the resulting runoff; however, there does not seem to be adequate data
to produce general relationships between the rainfall characteristics and
other physical factors such as land use, pollutant contaminants and concen-
trations, and volume of runoff applicable to a large geographic area. As
an example, data collected in four small suburban watersheds in the
Atlanta area (31) were used to calibrate the Corps of Engineers' computer
model STORM. However, when the calibrated model was used to duplicate
like data collected from other similar watersheds in the Atlanta area, the
differences between observed and computed values were more than would be
acceptable due to standard errors. The research project for Tulsa
-------
38
mentioned previously (2) utilized techniques and "models" to determine
procedures for estimating dispersed stormwater pollution from urban
areas. The three methods were developed "to enable urban engineers and
planners to calculate the preliminary estimates of the dispersed pollutional
stormwater loads to receiving streams from urbanized drainage basins
which would provide a range of concentrations and/or loads for the more
important pollutional parameters" (listed as coliform, Fecal Strep, BOD
COD, ON, PO4, TS, FS, and VS). The applicability and use of the Tulsa
Methods in determining an estimated range of values for several storm-
water pollutional parameters for other urban areas, such as those in New
Castle County, is unknown, especially when hydrological and physical char-
acteristics relating to the study area are recalibrated or adjusted. Use of
such empirical methods may or may not give better general pollutional load
or concentration values than using the ranges of such values from the liter-
ature with good judgment. The literature does not substantiate one method
over another; the topic of storm water is too complex and depends upon too
many unrelated variables.
Conclusions
In conclusion, it appears that each 208 area should have detailed
sampling data in order to evaluate the effects of stormwater runoff upon the
environment and to provide the data required for the use of a complex com-
puter model. Usually, though, the available data are inadequate and New
Castle County is no exception. In the absence of adequate data, however,
-------
39
general data derived from the characteristics of the study area under con-
sideration and the literature may be no less accurate (at least on the level
required to make stormwater management decisions) than a detailed storm-
water computer model calibrated with years of specific data.
-------
40
BIBLIOGRAPHY
NCC 208 Storm Water Quality Summary
Reference
Number
(1) Loehr, Raymond C. , "Characteristics and Comparative
Magnitude of Non-Point Sources. " Journal Water Pollution
Control Federation, Vol. 46, No. 8 (August, 1974).
(2) Cleveland, Jerry G. , et al, Evaluation of Dispersed
Pollutional Loads From Urban Areas, Oklahoma University,
Norman, The Bureau of Water Resources Research,
(April, 1970), NTIS PB 203 746.
(3) American Public Works Association, "Water Pollution Aspects
of Urban Runoff. " FWPCA Publication No. WP-2Q-15, U. S.
Department of the Interior, (January, 1969).
(4) Non-Point Pollution Evaluation Atlanta Urban Area, A Report
Submitted to the Savannah District Corps of Engineers
Savannah, Georgia for the Metropolitan Atlanta Water
Resources Study Group, Black, Crow & Eidsness, Inc., and
Jordan, Jones & Goulding, Inc. A Joint Venture, Contract
No. DACW 21-74-C-0107, (May, 1975).
(5) Loehr, Raymond C. , "Agricultural Runoff - Characteristics
and Control," Journal of the Sanitary Engineering Division
Proceedings of the American Society of Civil Engineers, SA6
(December, 1972).
(6) Harms, Leland L. , Dornbush, James N. , and Andersen,
John R. , "Physical and Chemical Quality of Agricultural Land
Runoff, " Journal Water Pollution Control Federation, Vol. 46,
No. 11 (November, 1974).
(7) Chiu, S.Y., McElroy, A. D. , Aleti, A. , and Nebgen, J.W.,
Non-point Pollutant Loading Functions as Water Quality
Management and Planning Tools, Second Annual National
Conference on Environmental Engineering, July 20-23, 1975,
University of Florida, Gainesville, (July, 1975).
-------
41
(8) Me Elroy, A.D. , Chiu, S.Y. , Aleti, A. , and Nebgen, J. W. ,
"A Systematic Review of Methodologies for Quantification of
Pollutants From Non-point Sources," Second Annual National
Conference on Environmental Engineering, July 20-23, 1975.
University of Florida, Gainesville, (July, 1975).
(9) The Task Committee on Urban Sedimentation Problems of the
Committee on Sedimentation of the Hydraulics Division,
"Urban Sediment Problems: A Statement on Scope, Research,
Legislation, and Education, " Journal of the Hydraulics Division
Proceedings of the American Society of Civil Engineers, HY4
(April, 1975).
(10) Guy, Harold P., and Jones, Earl, Jr., "Urban Sedimentation
In Perspective" Journal of the Hydraulic Division Proceedings
of the American Society of Civil Engineers HY 12 (December,
1972).
(11) Processes, Procedures, and Methods to Control Pollution
Resulting from Silvicultural Activities, U.S. Environmental
Protection Agency, Office of Air and Water Programs,
EPA 430/9-73-010, (October, 1973).
(12) Methods for Identifying and Evaluating the Nature and Extent
of Non-point Sources of Pollutants, U.S. Environmental
Protection Agency, Office of Air and Water Programs,
EPA 430/9-73-014, (October, 1973).
(13) Bondurant, James A. , "Quality of Surface Irrigation Runoff
Water, " Transactions of the ASAE (1971).
(14) Dunbar, D.D. , and Henry, J. G.F. , "Pollution Control
Measures for Storm waters and Combined Sewer Overflows,"
Journal Water Pollution Control Federation, Vol. 38, No. 1
(January, 1966).
(15) "The Good Old Days - They Were Terrible, "Texas Town and
City, Vol. LXH - No. 2 (February, 1975).
(16) Palmer, Clyde L. , "The Pollutional Effects of Storm-Water
Overflows from Combined Sewers, " Sewage and Industrial
Wastes, Vol. 22, No. 2 (February, 1950).
-------
42
(17) Palmer, Clyde L. , "Feasibility of Combined Sewer Systems, "
Journal Water Pollution Control Federation, Vol. 35, No. 2
(February, 1963).
(18) Me Elroy, Felix T.R. , Stormwater Runoff Quality for Urban
and Semi -Urban /Rural Watersheds, Purdue University, West
Lafayette, NTIS PB-231 482, (February, 1974).
(19) Colston, Newton V. , Jr. , and Tafuri, Anthony N. , Charac-
terization and Treatment of Urban Land Runoff, U. S.
Environmental Protection Agency, Office of Research and
Development, EPA-670/2-74-096 (December, 1974).
(20) Streeter, H. W. , "Standards of Stream Sanitation, "Sewage
Works Journal, 21, 1, 115, (January, 1949).
(21) Processes, Procedures, and Methods to Control Pollution
Resulting From All Construction Activity, U. S. Environmental
Protection Agency, Office of Air and Water Programs,
EPA 430/9-73-007, (October, 1973).
(22) Weibel, S. R. , Anderson, R. J. , and Woodward, R. L. ,
"Urban Land Runoff as a Factor in Stream Pollution," Journal
Water Pollution Control Federation, Vol 36, No. 7
(July, 1964).
(23) Burm, R. J., and Vaughan, R. D. , "Bacteriological Comparison
between Combined and Separate Sewer Discharges in South-
eastern Michigan," Journal Water Pollution Control Federation,
Vol. 38, No. 3, (March, 1966).
(24) Burm, R. J., Krawczyk, D.F., and Harlow, G. L. , "Chemical
and Physical Comparison of Combined and Separate Sewer
Discharges," Journal Water Pollution Control Federation,
Vol. 40, No. 1, (January, 1968).
(25) Geldreich, E.E. Best, L. C. , Kenner, B.A., and Van Donsel,
D. J. , "The Bacteriological Aspects of Stormwater Pollution, "
Journal Water Pollution Control Federation, Vol. 40, No. 11,
Part 1, (November, 1968).
(26) Sartor, James D. , Boyd, Gail B. , and Franklin, J. Agardy,
"Water Pollution Aspects of Street Surface Contaminants, "
Journal Water Pollutional Control Federation, Vol. 46, No. 3,
(March, 1974).
-------
43
(27) Bowen, D. H. Michael, "Runoff Poses Next Big Control
Challenge," Environmental Science and Technology, Vol. 6,
No. 9, (September, 1972).
(28) Storm Water Pollution from Urban Land Activity, AVCO
Economic Systems Corporation, Federal Water Quality
Administration, U. S. Department of the Interior, 11034 07/70
(July, 1970).
(29) Hergert, Stephen L. , Urban Runoff Quality and Modeling
Study, Masters Thesis, University of Nebraska, Lincoln,
NT1S PB-237-141 (December, 1972).
(30) Oliver, Barry G. , Milne, John B. , and La Barre, Norman,
"Chloride and Lead in Urban Snow," Journal Water Pollution
Control Federation, Vol. 46, No. 4, (April, 1974).
(31) Holbrook, Robert F. , Perez, Armando I., Turner, Billy G. ,
and Miller, Herbert, "Stormwater Studies and Alternatives in
the Atlanta Area," Second Annual National Conference on
Environmental Engineering, July 20-23, 1975, University of
Florida, Gainesville, (July, 1975).
(32) State-Of-The-Art; Sand and Gravel Industry, U.S.
Environmental Protection Agency, Office of Research and
Development, EPA-660/2-74-066, (June, 1974).
(33) Mac Millan, Robert T. , "The Mineral Industry of Delaware, "
Minerals Yearbook 1971, Volume II, Bureau of Mines, U. S.
Department of the Interior, (1973).
-------
DRAFT
STRUCTURAL AND NON-STRUCTURAL TECHNIQUES SUMMARY
FOR MANAGEMENT AND CONTROL OF STORMWATER POLLUTION
for the
208 PLANNING AGENCY
NEW CASTLE COUNTY, DELAWARE
NOVEMBER 1975
-------
TABLE OF CONTENTS
Title
TEXT
SECTION I INTRODUCTION
SECTION II ABATEMENT MEASURES
Land -use Planning
Improved Sanitation
Enforced Controls
Air Pollution
Chemical Use
SECTION III CONTROL MEASURES
Retention/ Detention
Rooftop Storage
Parking Lot Storage
Storage on Plaza Areas
Dry Impoundment or Detention Basin
Permanent Impoundments
Stream Channel Storage
Swale Storage
Subsurface Detention
Infiltration Systems
Infiltration Basin
Diffusion and Infiltration Wells
Shallow Infiltration Wells, Pits, and Trenches
Porous Pavement
Aeration of Lawns
Collection System Controls
Periodic Sewer Flushing and Cleaning
Catch Basin Cleaning
Infiltration /Inflow Control
Page
1
8
8
9
14
14
15
18
19
i
20
21
22
23
23
26
28
28
29
29
31
32
33
34
36
36
37
37
-------
TABLE OF CONTENTS (cont. )
Title
Page
TEXT (cont. )
Vegetative Cover
Erosion and Sediment Control
SECTION IV TREATMENT MEASURES
Physical Treatment
Sedimentation
Dissolved Air Flotation
Screens
Filtration
Biological Treatment
Waste Treatment Lagoons
Physical-Chemical Treatment
Chemical Coagulation
Disinfection
SUMMARY OF ALTERNATIVES
SECTION V
Table F-l
Table F-2
Table F-3
BIBLIOGRAPHY
TABLES
Land-use Planning Strategies and Techniques
Information About Various Types of
Street Sweepers
Summary of Construction Cost Estimates -
Open Ponds
39
44
49
56
56
64
68
71
80
83
91
92
98
105
106
Table F-4 Summary of Sediment Removal Costs
10
13
27
27
-------
TABLE OF CONTENTS (cont.)
Title
Page
Table F-5
Table F-6
Table F-7
Table F-8
Table F-9
Table F-10
Table F-ll
Table F-12
Table F-13
Table F-14
Table F-15
Table F-16
Table F-17
TABLES (cont.)
Summary of Storage Costs for Various Cities
Cost Comparison of Porous Pavement and
Conventional Pavement with Storm Drainage
Temporary Seeding and Seeding Dates
Soils, Seed Mixtures, Dates, for Semi-permanent
to Permanent Seedings
Maintenance, Fertilization, and Mowing for
Permanent Seeding
Costs of Sediment Control Methods
Cost Summary of Sediment Control Alternatives
Renovated Wastewater Quality Characteristics
Before Industrial In-plant Treatment
Constituent Concentrations and Settling
Characteristics of Urban Stormwater Runoff
From a Single Storm 8/19/65, 27-acre (11-Ha)
Residential, Light-commercial Area,
Cincinnati, Ohio
Summary Data on Sedimentation Basins Combined
with Storage Facilities
Settling Velocities of Selected Particles,
After Hazen
Cost of Stormwater Sedimentation Facilities
Typical Removals Achieved with Screening/
Dissolved Air Flotation
30
35
41
42
43
48
48
52
Table F-18 Generalized Quality Comparisons of Wastewaters
58
60
62
65
67
69
-------
TABLE OF CONTENTS (cont.)
Title
Page
TABLES (cont. )
Table F-19 Dissolved Air Flotation Cost for 25 mgd
Table F-20 Classifications of Screens
Table F-21
Table F-22
Table F-23
Table F-24
Table F-25
Table F-26
Table F-27
Table F-28
Table F-29
Figure F-l
Figure F-2
Figure F-3
Figure F-4
Characteristics of Various Types of Screens
Design Parameters for Filtration Mixed Media,
High Rate
Cost of High Rate Filtration
Design Factors for Stabilization Basins
Land Area versus Capacity - Open Ponds
Achievements of Chemical Clarification
Examples of Filter Performance on Various
Effluent Types
Comparison of Ideal and Actual Chemical
Disinfectant Characteristics
Effectiveness of Alternatives in Pollutant
Reduction or Removal
FIGURES
Cost of Sedimentation Facilities
Cost of Filtration at 4 gpm per Square Foot
for Design Capacity 0. 01 mgd to 10 mgd
Cost of Filtration at 4 gpm per Square Foot
for Design Capacity 0.1 to 100 mgd
Cost of Aerated Wastewater Stabilization Ponds
70
72
73
75
77
86
90
95
97
101
106
63
78
79
88
-------
TABLE OF CONTENTS (cont. )
Title Page
FIGURES (cont.)
Figure F-5 Cost of Non-aerated Wastewater Stabilization
Ponds 89
Figure F-6 Cost of Lime Clarification 96
Figure F-7 Cost of Chlorine Contact Basins 103
Figure F-8 Cost of Chlorination Feed Systems 104
-------
F. Structural and Non-Structural Techniques Summary for Management
and Control of Stormwater Pollution
SECTION I
INTRODUCTION
Until recently, the only problems associated with the word "storm
water" have been as a result of flooding. Major losses from flooding are
very evident in the form of real and personal property, loss of human and
animal life, disruption of rivers and streams, and inconveniences in the
disruption of public utilities. As a result of such losses, the Corps of
Engineers built the first Federal flood control works on the Mississippi
River in 1928 (34), thereby expanding their work responsibility which pre-
viously concerned only development of navigation and improvement of
harbors. Recent increased flooding as a result of urbanization has focused
attention on construction (or its limitations) in the "flood plain. " Although
the natural, ecological, recreational, and even logical aspects of preserv-
SAWM
ing flood plains/fhave restricted development in these areas, they have had
only a minimal impact in limiting development within flood plains. Con-
tinued high levels of flood losses led the Congress to enact the National
Flood Insurance Program which has the objectives of making available
insurance protection and encouraging the development and application of
adequate land use and control measures in order to reduce or avoid future
flood losses.
Stormwater management problems have since been expanded to in-
clude pollution resulting from combined sewer overflows, storm sewer
-------
discharges, soil erosion, and problems associated with the beneficial use
rf.S.
of storm water (35). Over the past decade the^Environmental Protection
AUO ITS ff^E&KSSoA flG£»C/£S
Agency (EPA)y(has supported a large research effort in the field of storm-
water management, but emphasis has been placed on control and treatment
of storm sewer discharges and combined sewer overflows which are
characteristic of urban areas (36).
In 1911, Congress passed the Weeks Forest Purchase Act authorizing
the Secretary of Agriculture to take certain steps toward managing the
flow of navigable streams (34). The Soil Conservation Service was estab-
lished under the authority of the Soil Conservation Act of 1935. This agency
was created to develop and implement measures to reduce and retard run-
ro
off it^fcurbiaig soil erosion. Although farmers enacted these measures to
preserve valuable topsoil for agricultural production, a secondary benefit
was reduction in nonpoint pollution from this source.
The alternatives available to reduce stormwater pollution have been
categorized into three general topics (37) as follows: (a) abatement, (b)
control, and (c) treatment. Abatement measures include all pre-storm
actions directed toward reducing availability of pollutants to storm flows
such as air pollution reduction, avoidance of over-application of fertilizers,
pesticides, or herbicides, street sweeping, periodic flushing of collection
systems, sewer separation, minimization of exposed jXf land surfaces dur-
ing construction, and maintenance of good vegetative cover in erodible
areas. Control measures directly influence the stormwater path, flow
-------
rates, or loadings. The most common of these are terracing, strip crop-
ping, contouring, diversions, roof top and parking area storage, and other
in-line or off-line detention facilities including in-line storage basins or
ponds. The treatment measures generally involve physical, chemical, and
biological techniques which previously have been developed for sanitary and
industrial wastewater treatment.
The management and control techniques for reducing stormwater
pollution are as complex as the characteristics and constituents of storm
water itself. Since the amount and types of pollutants in storm water have
been determined to be partially a function of the rainfall intensity and dura-
tion in addition to land-use type, it logically follows that reduction in the
hydrologic and hydraulic rates would also reduce pollutants. If, for
ffS
example, a good vegetative cover is maintained, then friiw dissipati
raindrop energy upon striking the ground^is less likely to dislodge soil
TMVS
particlesAmaking them available for transport by runoff. This cover may
also act as a filter to remove debris, ^slow down the runoff rate thereby
reducing the possibility of scouring, as well as provide nutrient uptake and
reduction of oxygen- demanding materials resulting from plant uptake.
If measures such as temporary storage are used for the purpose of
reducing peak runoff rates or volumes, there is a possibility that detention
time may also be sufficient to provide some degree of physical treatment
(sedimentation) and even biological treatment.
Thus, it is evident that selection of one alternative to reduce storm-
water pollution can in all likelihood provide secondary benefits. One such
-------
benefit which is "designed into" the alternative is the use of flood plains
for recreation areas or turning detention Basins into permanent ponds
while retaining flood storage, commonly referred to as blue-green areas
when used in conjunction with green belts or open areas. Therefore, selec-
tion of any alternative techniques for control of stormwater pollution should
not only consider its engineering and economic soundness but also the
social and environmental benefits or disadvantages.
The primary responsibility for nonpoint source (NPS) management
under PL 92-500 rests with the states, and the implementation of these
programs will be part of the areawide planning process in designated 208
areas. The EPA's responsibility in the NPS management effort is to pro-
vide guidance to the states or 208 agencies in order that the 1983 water
quality goals of the Act may be reached. The EPA must also review and
approve the management plans submitted by the state or agency.
The purpose of this section of the study is to present various methods
of preventing, controlling, or reducing the pollutional effects which storm-
water runoff can have upon receiving waters. In order to perform a com-
plete evaluation of an alternative, the costs of constructing and maintaining
it must also be considered.
As mentioned previously, the field of separate stormwater manage-
ment is a relatively new area. As limited as the available literature, data,
and techniques applicable to separate stormwater management are, the
information on the costs of such alternatives and methods is even less
abundant. A number of articles in the literature have presented costs of
-------
their subject facilities; however, either the data presented were too gener-
alized, the facility was too specific to one particular area or instance, or
the source of the storm water considered was from a combined sewer
rather than a separate one.
Fortunately, however, a considerable amount of separate data indi-
cate that previously developed expertise for conventional water supply and
wastewater treatment problems, as well as techniques to conserve water
and soil, are applicable to the problems created by rainfall runoff.
Therefore, when information regarding a particular control or treatment
alternative or technique is not available with respect to separate storm-
water management, it will be assumed that a specific water or wastewater
unit or process capable of similar desired performance will be applicable.
Similarly, abatement measures that are doubly effective in preventing
pollutant removal and transport as well as conserving soil and water will
also be considered applicable, and^available costs of such/\used.
As indicated above, all costs were derived from the literature, and
the major portion of such data were from three sources: references 36,
40, and 62 in this report. The cost data in these references were re-
portedly derived from project reports, bid tabulations, contractor and/or
manufacturer quotations, published articles, and EPA reports.
The cost of almost any facility is dependent upon the size, the pro-
cess, geographic location, time of construction, and disposal of byproducts
where required. (36) One method to reduce the wide variation caused by
-------
6
such considerations is the use of a common cost basis such as the Engi-
neering News-Record (ENR) Construction Cost Index. This index was
created in 1921 to diagnose price changes that occurred during and immedi-
ately following World War I, and to evaluate their effect on construction
costs. The derivation of the index is based on constant quantities of
structural steel, Portland cement, lumber, and common labor. (66) An
darA ARE.
average U. S. construction cost index is updated monthly; boing^derived
from 20 individual U. S. cities. Since the individual cities1 indexes are
also reported, a more geographically correct index is possible for a speci-
fic area.
The cost indexes of the cost figures for the various alternatives are
presented herein where they were available from the literature. If no such
index was reported, no attempt was made to estimate an applicable one due
to the unknown factors used to generate the data.
It should be noted, however, that although the use of cost indexes to
validate costs is warranted, the sparsity and individuality of actual installa-
tions makes such generalization only a best guess when using available
information. Even with a considerable amount of specific data, such cost
estimates probably can be accurate only within a range of 20 to 30 percent
due to unknown contingencies.
The cost estimates for individual abatement, control, and treatment
measures will appear in the individual discussion of each where available.
All costs reported herein are exclusive of land which, unfortunately, can
be the most important factor when comparing specific alternatives.
-------
Because of the great variation in types and amounts of pollutant con-
stituents, their sources, and methods of reduction, as reported in the
literature, there is no single common denominator between them. Some
parameters are considered in terms of concentrations such as mg/1 while
others are related to area, such as pounds per acre or pounds per curb
mile. In any event, no attempt was made to convert such values to a com-
mon parameter unit.
-------
SECTION II
ABATEMENT MEASURES
The EPA's guidance will strongly emphasize the value of preventive
i approaches to NFS management. The most feasible means to deal with NFS
problems will probably involve application of land and resources manage-
ment practices which prevent the generation of pollutants. Many of these
practices are in use and some are in the process of being developed.
After examination of alternative practices, those most effective in
preventing or reducing the amount of pollution by a NFS will be included
in implementation of "Best Management Practices" (BMP) by the states.
The BMP's will be determined with reference to: a) physical characteristics
of a site or area (i. e., rainfall, soil, slope, vegetative cover); b) land
use or activity generating pollutants (i. e., agriculture, urban, silviculture,
construction); and c) water quality and quantity needs of the basin or stream
segment. Obviously, a BMP for one condition may not be appropriate in
another similar situation, and they should not be applied indiscriminately
across a state. A state with uniform physiographic and climatic character-
istics, however, will need fewer variations in its BMP's.
Land-use Planning
Land use is one of the major variables in the determination of quan-
tity and quality of storm water. The effects of land-use type, distribution,
and rate of growth, attitudes toward specific types of development such as
industrial or multi-family residential, as well as political structure and
-------
9
climate, may be of greater importance than treatment processes or tech-
nical developments (44). Therefore, land-use planning is of primary
importance in stormwater pollution abatement, and should be a major tool
of the water quality management process. The ways in which land use
affects water quality are well understood; however, the reverse relation-
ship is less documented. For example, polluted waterways probably re-
duce housing values, although the direct effects are aesthetic and
recreational.
A great number of strategies for meeting water quality goals by
means of land-use planning are available. Shubinski (38) compiled a state-
of-the-art summary of techniques for such strategies presented by
Voorhees (39). They were broken down into regional, site development,
and land management strategies and are presented in Table F-l.
Improved Sanitation
Better housekeeping measures to remove leaves, street litter,
refuse, and other solid wastes before they find their way into stormwater
runoff will obviously reduce pollution from this source, although quantita-
tive information is generally limited to street litter in the literature.
Improved solid waste collection would also have the added benefits of min-
imizing rats and other rodents, and thus reduce their associated bacterio-
logical pollution (25).
A considerable amount of investigation has been undertaken to vali-
date the water pollution potential of street surface contaminants and the
-------
TABLE F-l
LAND USE PLANNING STRATEGIES AND TECHNIQUES (38)
10
A. REGIONAL STRATEGIES AND TECHNIQUES
STRATEGY
Modify growth rate
Modify growth distribution and density
Preserve environmentally sensitive areas
and open space
Control location of critical uses
B. SITE DEVELOPMENT STRATEGIES
Encourage proper site selection
Modify project size and mix
Exercise sound site planning principles
C. LAND MANAGEMENT STRATEGIES
Control construction related erosion
IMPLEMENTATION TECHNIQUES
* Policy recoimendations and decisions
by governmental leaders
* Zoning
* Public service policy
* Building >Toratoria
* New town assistance programs
* Locational decisions for major public
facilities such as sewage lines and
treatment plants and location of
major highways
* Zoning
* Local jnoratoria on sewage taps or
extensions
* Regional planning and adoption of policy
and controls by member jurisdictions
* A-95 review and environmental impact
statements
* Tax abatement for open space
* PUD, large lot zoning
* Negotiate densities proposed in impact
areas
* Acquisition special zones requiring
use permits
* __Zoning
* Private or public compacts
* Tax incentives and disincentives
* Collaborative regional planning and
funding
* A-95 review: environmental impact
statements
* Federal or state regulation of certain
uses
* Zoning, subdivision, building and
other regulations
* Site plan review
* Permit to construct
* Erosion and sedimentation control
ordinances
-------
TABLE F- ' (CONT.)
Utilize conservation practices in
agriculture
Utilize conservation practices in
flood plains,shorelines
Control resource extraction
* Soil conservation service advice
Regulations requiring conservation
service advice
Laws regulating application of fertilizer
pesticides & disposal of animal waste
Conservation plans
Advisory services regarding pesticide
and fertilizer application, feedlot
management
*
*
*
*
*
*
*
*
Zoning
Subdivision and other regulations
Acquisition in fee or easement
Building permits
Fill and dredge laws
Require plan for water quality protection
Performance bonds prior to permitting
use zoning permits systems
-------
12
effectiveness of street sweeping in reducing this urban source (26, 3). It
is generally agreed that, at least in the past, street cleaning practices
have been essentially for aesthetic purposes and in this regard have been
successful. However, even under well operated and highly efficient conven-
tional sweeping programs (i.e., mechanical-type sweepers), removal of
the fine silt-like material (where the concentration of pollutants is of
greatest significance) is limited to about 15 percent (26). The overall
efficiency of the mechanical sweepers is reported to be about 50 percent.
Of importance to street cleaning as a viable pollution reduction
measure is that 95 percent by weight of the material is located within 40
inches of the curb and 78 percent is within 6 inches of the curb. This is
presumably a result of transport by traffic to the curb by air currents
and direct impact (26).
Vacuum street sweepers of several different designs have recently
been introduced in this country. Their overall efficiency is reported to vary
between 70 and 90 percent. Additional advantages over mechanical sweepers
have been listed as: a) fewer parts to break down, resulting in lost time
and expensive repairs; b) require only one pass to remove contaminants;
c) no required support personnel to transfer collected material; and d) no
dust clouds created during operation, often characteristic of mechanical
sweepers. The vacuum sweepers were also reported to be cost competitive
with mechanical sweepers when total costs (capital, operational, and main-
tenance) are considered (40). The general information available on three
types of street sweepers, including costs, is presented in Table F-2.
-------
TABLE
INFORMATION ABOUT VARIOUS TYPES OF STREET SWEEPERS (40)
Swe c p e r _T yn.e_
Sweeping Speed
Maximum Vehicle Speed
Cost per curb mile
Commercial Rates
Mechanical
3-10 rnph
15-25 mph
$2-$8
$15-$25/hr.
Regenerative
Vacuum Air
3-10 mph
6 0 mph
$2-$14
$20-$30/hr.
3-10 mph
60 mph
$3-$10
$20-$25/hr
-------
14
Enforced Controls
The APWA made a study of 224 U. S. cities of varying sizes and
geographical locations and asked the cities to supply copies of ordinances in
specific categories with respect to control of pollutants capable of entering
storm water (3). The replies were analyzed and grouped into the following
classifications:
a. Anti-litter
b. Debris, etc., on vacant lots
c. Erosion control
d. Parking lots and garage
e. Handbills
f. Site cleanup of circuses, carnivals
g. Produce markets
h. Weed control
i. Discharges into sewers
j. Cleanliness of private property
k. Street excavations
1. Vehicular spillage and littering
m. Moving and demolition of buildings
n. Bonfires and incineration
o. Building construction materials
p. Animals and animal care establishments
q. Storage and disposition of garbage and rubbish
r. Authorized and unauthorized dumping
Air Pollution - This is a source of stormwater pollution which should
not be overlooked when evaluating the composition of runoff, particularly in
I urbanized areas. Although a substantial amount of air pollution is of natural
origin, the significant harmful contaminants are manmade and, as such,
are technically controllable. Therefore, any programs oriented toward
control and reduction of air pollution (both on the local and national level)
will surely reduce undesirable materials from entering the atmosphere and
reaching streams and lakes.
-------
15
Chemical Use - When referring to chemical control, the example
that first comes to mind is de-icing salts, commonly sodium and calcium
chloride, used on roads and highways in northern latitudes. It is esti-
mated that in 1965 and 1966, 4. 8 tons of de-icing salts were applied to
Delaware roads per single lane-mile (41). Chloride concentrations in a
stream below a shopping center were found to average 29 mg/1 in winter
months, while the summer concentration was only 15 mg/1.
The corrosive properties of the salt have been estimated to cost pri-
vate automobile owners about $100 per year. In addition to economic and
common pollutional aspects of de-icing salts, other substances added to
them to prevent caking and inhibit corrosion of automobiles have been found
to be toxic to human, animal, and fish life. Others, such as sodium ferro-
cyanide (an anticaking compound) are not toxic until exposed to sunlight,
which in this case releases cyanide (40,41).
Two alternatives to reducing the pollution potential associated with
chemical de-icing practices are: (a) careful selection in the types of chem-
icals and moderation in their application; and (b) removal of salt-laden snow
to dumps where controls can prevent the melt from entering surface
waters. Also, since careful attention to possible groundwater contamina-
tion is required with the latter alternative, it is believed that the better
alternative is moderation in use and careful selection of chemicals.
Alternatives to the use of salt include (40): (a) in-slab thermal
melting; (b) mobile snow melters; (c) substitute de-icing compounds;
(d) compressed air with blade; (e) snow adhesion-reducing substances in
-------
16
pavements; (f) pavement materials that store solar energy for melting;
and (g) salt retrieval. Burlington, Massachusetts investigated a number of
alternatives to salt because of the pollution of a water well (40, 42). The
alternatives included heated sanders, 23 different types of abrasives, sub-
stitutes for salt, and rubber-tipped blades for snow plows. After three
years, it was decided that pure salt should be used on pavements at hills,
curves, and other problem areas, while a 3 to 1 ratio of salt to sand could
be effectively and economically used elsewhere. When the removal effi-
ciency and cost are both considered, according to current literature, the
use of salt is far superior in highway de-icing.
Black, Crow, and Eidsness (-40) summarized from the literature,
some data on costs of de-icing and alternatives. They reported that cover-
ing a stockpile with a tarpaulin would cost $3 - $5 per ton of salt and that
the cost of bin storage was $50 - $70 per ton. It was. reported that chemical
treatment of snow and ice would cost about 10 times the cost of salt appli-
cation, which was reported to be $19 per ton. With respect to heating, it
was reported that operation and maintenance would be the lowest of the
de-icing alternatives; however, construction cost would be in the order of
$300, 000 per lane-mile.
Pesticides, herbicides, and fertilizers are also of importance in
considering sources of pollution amenable to enforcement or management
methods of control. The presence of these substances is equally common in
urban and rural areas. Such municipal and residential operations as tree
spraying, weed control, rat control, insect control, and fertilization add to
-------
17
chemical residues in the urban environment. Similarly, the use of fertili-
zers, pesticides, and herbicides has been essential to the increased crop
production that has permitted the United States to feed not only itself but
also other nations (5). Agriculture is by far the largest user of these
chemical compounds (3), and whether for urban or rural usage, such mate-
rials are used by most people in greater amounts than are necessary.
Although these chemicals become associated with the soil after
application and soil erosion prevention measures will control their release
into surface waters, the apparent first solution to the problem is to mini-
mize the amount becoming available to the environment. This is fairly
straightforward for pesticides and herbicides, but fertilizers are more
complicated. The best way to add fertilizer is when it is needed for crop
growth; however, efficiency of fertilizer usage depends upon time of appli-
cation, type of crop, climatic conditions, soil type, and fertilizer charac-
teristics (5). Some specific practices that can reduce the availability of
fertilizer nutrients that are lost to surface streams as listed by Loehr (5)
are as follows: (a) avoid application on frozen soils; (b) limit the amount
applied to that needed by crops; (c) minimize fall application; (d) time
application to be consistent with crop need; (e) spread fertilizer on growing
crops or stubble rather than on bare soil; and (f) avoid application on slopes
capable of rapid runoff.
-------
18
SECTION III
CONTROL MEASURES
As mentioned previously, control measures are generally designed
to reduce the volume and/or flow rate of stormwater runoff. In accom-
plishing this objective, the measures in almost all cases influence the
quality of the runoff, fortunately improving it as a rule.
Control measures can usually be implemented after development is
established; however, to choose the most efficient and economical com-
ponents and combinations, they should be initiated in the planning stage
prior to any construction. A good example of this is The Woodlands, Texas
which is a planned community 25 miles north of Houston. It is an entirely
new community which will consist of about 18, 000 acres by 1990. Two
major goals in developing the community were: a) preservation of the
natural environment and setting; and b) minimization of increased storm-
water flows and pollution as a result of development. Control and abate-
ment measures which will be employed in reaching these goals include:
a) utilizing the natural drainage system in its existing undeveloped, grass-
covered state to slow and reduce runoff by infiltration; b) using swales
lined with native vegetation where drainage channels are required;
c) retention and detention facilities, where practical, to minimize effect
of urbanization on flow rate and volume; d) implementing erosion control
measures in construction areas to minimize sediment runoff from these
areas; e) using drainage pipes only in highly developed areas where natural
-------
19
systems are infeasible; f) possibly using porous pavement; and g) control-
ling the use of pesticides, herbicides, and fertilizers to minimize the pos-
sibility of their polluting runoff. (36, 51)
It was estimated that the natural drainage system would cost $600
per acre, compared to about $1,200 per acre for a conventional channalized
and sewered system. Three other good examples of implementation of
stormwater management programs from the planning stage are: a) Fairfax
County, Virginia within the 22, 690-acre Pohick watershed near Washington,
D. C. (34); b) Rock Creek Planning Area of Montgomery County, Maryland
(34); and c) the new planned town of Columbia in Howard County, Maryland
(52) also near Washington, D. C.
Retention/Detention
In reviewing the literature on stormwater pollution, it is evident that
sediment (i. e., suspended solids) is the predominant pollutant. In terms
of quantity, its volume far exceeds that of any other chemical, biochemical,
or bacteriological contaminant. In addition to having potential detrimental
physical characteristics such as reducing light penetration through water,
covering spawning areas and bottom algae, and damaging fish gills, such
secondary pollutional media as oxygen-demanding materials and toxic sub-
stances have been associated with it.
Because of the close relationship between erosion and rainfall-runoff
characteristics, any measures which reduce or retard the flow rate and/or
-------
20
quantity of storm water will in all likelihood reduce erosion, and thus, sed-
iment pollution, the most widespread methods for attaining such results
are retention and detention. "Detention generally refers to holding runoff
for a short period of time and then releasing it to the natural watercourse
where it returns to the hydrologic cycle. Retention facilities normally
refer to schemes whereby water is held for a considerable length of time
for aesthetic, agricultural, consumptive, or other uses. "(35) In relation to
"source" abatement measures, these retention or detention facilities would
be "on-site" or at least upstream impoundments. Common examples of
these are rooftop storage, parking lot storage, local recreational area
storage, and small detention basins and ponds constructed within the limits
of development areas. For agricultural areas, "the use of contour plowing
is one of the best means available for stormwater management and runoff
control. "(35) Other such methods relative to rural or undeveloped land are
minimum tillage on slopes, terracing, strip cropping, use of crop residues
on soil, diversions, and avoidance of bare land surfaces. (5)
Rooftop Storage - Horizontal rooftops are used in some areas for
stormwater detention. The objective of this approach is to use available
storage capacity of a roof to reduce the discharge rate of storm water into
collection systems during a storm. Proponents of this alternative cite that
most industrial and commercial flat-roofed buildings would meet required
design criteria. In many existing buildings, the roofs are designed for a
snow or live load of 30 to 40 pounds per square foot, or an equivalent of
-------
21
5. 8 to 7. 7 inches of water, representing a considerable rainfall event.
(34, 35) The existing buildings may be adequate to support such weight,
but leakage, requiring additional waterproofing, could result. A survey
of three downtown commercial blocks in the Borough of State College,
Pennsylvania found that more than half the surface area was occupied by
flat roofs (36), although the actual amount over a watershed would probably
be considerably less, especially if the existence of peaked roofs is consid-
ered. In a hypothetical case study for the Corps of Engineers, an urban
watershed of 200 acres was assumed to include 200, 000 square feet of flat-
roofed buildings. (35) It was estimated that it would be possible to use roof
storage to reduce the peak runoff rate from the area by about 11 percent
(from 185 cfs to 165 cfs). Other advantages to rooftop facilities are they
are not unsightly because they are not visible, and they present no safety
hazards to children. However, there may be problems of leakage, possible
structural overloading (if applied to existing structures), maintenance to
remove debris and ice, and the possibility of heavy rainfall overflowing the
top of the roof if drains become blocked, any of which could cause damage
to the building or its contents. Also, these facilities only reduce peak flows
downstream and do not remove pollutants to any degree. Because of the
above, it would seem that use of this type of detention would be desirable
only in an area of highly concentrated flat-roofed structures or for new
construction where proper design features can be incorporated.
Parking Lot Storage - Most typical commercial, industrial, multi-
family and institutional facilities reserve a considerable amount of area for
-------
22
parking. Parking lot storage consists of using either the surface parking
lot or porous soil beneath it to retain excess precipitation and reduce run-
off. This is generally accomplished by under sizing stormwater inlet struc-
tures, placing gravel filter dams around inlets, or percolation trenches.
A notable application of this technique (34,35) is a 33-acre shopping
center in Florissant, Missouri, a suburb of St. Louis. The parking lot was
divided into a series of depressed rectangles, each draining into a control
drainage system. It is reported that a heavy to medium rainfall would re-
sult in a depth of only 2 to 3 inches, with maximum allowable storage being
12 inches. The use of detention with reduced drainage facilities was re-
ported to cost $115,000, which was a $35,000 savings over a conventional
system with no retention provisions. Other advantages include: from a
structural standpoint, there is no limit to the depth of water that can be
stored; the surface need not be level; ease of inspection and maintenance
with conventional street cleaning equipment; and possible use of porous
pavement to increase infiltration and aquifer recharge. The only problems
associated with parking lot detention appear to be inconvenience for a per-
iod of time while the lot drains after rainfall. Other problems may be
avoided by not designing steep slopes which may result in unusually deep
ponding. Also, steepness may cause inconvenience in walking for elderly
or handicapped persons and in vehicle entry or exit during times when ice
forms on the pavement.
Storage on Plaza Areas - The use of detention storage on areas
around commercial and office buildings is similar to parking lot storage,
-------
23
but differences may include drainage area, grading requirements, and
depth of ponded water. (35)
Dry Impoundment or Detention Basin - These facilities are perma-
nent structures designed to provide temporary storage for storm water
with later release at a controlled rate. The release rate is generally based
on the downstream capacity of the receiving waterway.
Since the facilities hold water only during and for a short time after
rainfall, they have a potential for multi-purpose use. These detention
basins have been located in recreational areas, greenbelt areas, and neigh-
borhood parks.
In some areas of the country, erosion and sediment control practices
are required during construction. When construction is completed, these
basins could be converted into detention basins. One such example is a
4. 5-acre office site in Rockville, Maryland where the runoff from both the
roof and parking areas is conveyed to two dry impoundments having a de-
signed release rate equivalent to the two-year design storm prior to
I development. (34)
Permanent Impoundments - The planned integration of permanent
lakes or ponds in open spaces or greenbelts with provisions for flood stor-
age has become known as the "blue-green" concept. The most common way
to create this effect is to build a dam across a small drainage waterway.
Another method is to excavate below the water table in areas where the
water table is high. In any case, the object is to create a permanent pond
-------
24
with a normal water surface somewhat below the top of the release struc-
ture to provide temporary flood storage and controlled release of storm
waters.
Thus, the blue-green concept can provide a number of benefits to an
individual site or development as well as the environment: (a) recreational
area; (b) an aesthetically-pleasing environment; (c) temporary flood stor-
age; and (d) removal of sediments and nutrients from urban runoff.
It should be noted, however, that such ponds or retention basins may
or may not provide the desired degree of pollutant removal. Because of
design or land constraints, they may be adequate to remove only sand and
gravel-sized material, and possibly a small part of silt-sized particles.
The effectiveness of trapping these smaller-sized particles depends on
hydraulic characteristics and size of the pond. These facilities are unlikely
to remove clay-sized particles remaining in suspension, which are highly
visible and may give the appearance of muddy or "polluted" water in the
pond. (10)
In specific rural or agricultural areas, the primary purpose of
retention ponds is to minimize pollution caused by runoff from animal pro-
duction areas. With proper management, these retention ponds can also be
utilized for treatment of wastewater from feedlots. They may be used as
lagoons, oxidation ponds and evaporation ponds, and with other facilities
such as aeration systems and spray irrigation.
The benefits of retention ponds are very attractive when considered
alone. However, it must be noted that the impoundment is highly susceptible
-------
25
to pollution from such sources as construction-generated sediment, accum-
ulation of debris and floating trash characteristic of any inhabited area,
possible contamination from domestic sewage and, of course, stormwater
runoff. Therefore, continuing maintenance will be required to keep such
facilities in their expected condition. The principal maintenance problem
will be removal of accumulated sediment and its subsequent disposal. Sev-
eral possible uses for the sediment near the basin are to: a) improve grad-
ing and reduce steep slopes, b) fill unwanted gullies and ravines, and
c) cover material for solid waste disposal areas. Care must be taken to
prevent erosion of the sediment from the disposal area back into the stream
system.
Floating debris may be removed by skimming barriers designed to
float on the water, generally positioned just as runoff enters the lake.
The inflow of nutrients into a pond will probably produce conditions
favorable for aperiodic algal blooms. If such occurrences are not desirable,
there is the alternative of chemical treatment. Hitman and Associates (34)
reported the most common method of such chemical treatment as the appli-
?
cation of copper sulfate at a rate of 2 pounds per cfs; however, no related
time value was reported in order to estimate the resulting concentration.
Ehlers and Steel (67) similarly recommend a dosing of 10 to 20 pounds of
copper sulfate per million gallons to control algae growth in swimming
pools. The copper sulfate will destroy the algal bloom but it is also toxic to
almost all forms of plankton and fish and there is the potential for buildup
of copper concentrations in bottom sediment. Cuprose (copper citrate) has
-------
26
also been effective in controlling algae at concentrations of 2. 0 ppm, but
! with no fish kill. Biweekly applications of cuprose at concentrations above
3. 0 ppm should also be effective in control of aquatic weeds.
Mallory (52) compiled data for various sizes of "open ponds" which
had the purposes of peak stormwater flow reduction and sediment removal.
This tabulation, including various sizes of ponds up to almost one acre in
surface area, with the associated cost estimates, is presented in Table F-3.
The estimated costs of sediment removal from such ponds, based
on a facility receiving 10,000,000 gallons of runoff per year, were also
reported by Mallory and are presented in Table F-4.
Stream Channel Storage - Streams can usually provide a substantial
amount of storage in either the channel, the voids of the soil on the banks,
or the valley. The valley area is more commonly referred to as the flood
plain, and the extent of the flood plain is generally computed based on an
assumed flood frequency discharge. Flood plain storage is mainly used to
| alleviate storm runoff peak discharges in areas where a more natural
drainageway is desired rather than the excavation of channels. This
approach would lend itself more to a developing area, where the flood plain
can be reserved for recreation and greenbelt use than an existing developed
area where flood plain storage would cause damage to property, inconven-
ience, and health and safety hazards.
The storage capacity can be increased by use of check dams. They
are also useful in reducing the effective slope of the stream, and thus
velocity, thereby dissipating energy and controlling downstream erosion.
-------
TABLE F"3 SUMMARY OF" CONSTRUCTION COST ESTIMATES - OPEN PONDS (52)
... ....__>.,,-..._ ,,.! , 1 ".. .- , 1 ...III - ...» 1 1.- . ..II 1 1 - ... - M., 1. .1 ..!., ..... -,. 1 - -_ . _ ,_ , , ' -.. ...... - -1 _l. ._ * ^ V
(Cost Items in Dollars)
1,
1,
1,
Capacity
(gal) "
52,950
97, 950
159, 450
238, 800
339, 300
465, 000
630, 000
858, 000
015, 000
105, 000
780,000
Concrete
Yards
16.02
20. 11
23. 89
39.22
42.77
52. 03
70.37
87.00
102. 00
110.00
151.00
Excavation
Yards
87. 9
161.9
263.8
393.4
560. 1
768.4
1, 037.0
1,416.7
1, 660. 0
1,800. 0
2, 850. 0
J'VJilU
Area
(sq.ft. )
2, 500
4, 000
5, 500
7, 000
9,000
11, 250
15, 000
20, 500
23,000
24, 400
35,000
Concrete
Cost
1, 153
1, 448
1, 720
2, 820
3, 078
3,746
5, 063
6, 226
7,344
7,920
10,872
Embank
ment
Cost
30
30
30
54
60
71
101
497
520
529
840
_
Excavation
Cost
160
360
535
810
1, 050
1, 320
1, 300
608
1,850
2,040
3, 358
Clear
& Gru
30
40
55
70
90
112
150
207
230
244
350
h
1,
1,
1,
1,
1,
3,
Rip
Rap
109
402
740
786
142
031
970
878
536
187
500
Net
Total
1,482
2, 280
3, 080
4, 540
5, 420
6, 280
7, 584
9, 454
11,480
11, 920
18, 920
Cont.
-(25%
371
570
775
1, 1 35
1, 355
1, 570
1, 896
2, 364
2, 870
2, 980
4,730
Gross
Total
1, 853
2, 850
'I. 8=i -3
5 , t> 7 o
6, 775
7, 850
9,480
11, 818
14,305
14, 900
23,650
TABLE F'4 SUMMARY OF SEDIMENT REMOVAL COSTS (52)
Number of Total
Occurrences Man- Labor Equip. Per per
per Year hrs Rate Cost Cost Occurrence Year
Routine
Check
Trash
Removal
Sediment
Removal
50
25
25
0.5 2.88 1.44 0.50
0.2 2.88 0.58
1.0 2.88 2.88
1.0 4.03 4.03 8.33
Total trash and sediment removal, cost per year
1. 94
0.58
11.47
$ 97.
14.
381.
00
50
00
$41)2. 50
Trash and sediment removal, cost per gallon runoff $0.00004925
TV
-sj
-------
28
However, their use in flood-prone areas should be carefully considered,
since they increase the water surface elevation and thus the chance of
flooding for a given storm discharge.
Swale Storage - Swales are most commonly associated with site
grading for drainage of individual lots in urban areas. They are generally
located on either side or the back of property lines and drain longitudinally
through a block. The gradients of swales are quite gentle and, when prop-
erly designed, can cause up to six inches of temporary ponding along prop-
erty lines. The ponded water is either discharged at controlled rates or
allowed to percolate into the ground.
This method is limited to areas which can be suitably vegetated and
have topography conducive to the development of mild gradients. (34)
Subsurface Detention
Subsurface detention within the storage space of the pipe network is
commonly known as "in-line storage. " Such detention in large combined
sewer systems is considered a "control method" of pollution reduction. Use
of the storage space within the storm sewer system and/or the construction
of subsurface storage tanks, in-line or off-line, are subsurface detention
measures and can be considered "control" methods. These facilities have
been generally used in areas of high-cost developments where there is little
or no open space available for alternative systems. They are located so as
to receive the volume generated by the peak rate in excess of what the
stormwater system can handle. Then, when the capacity of the collection
-------
29
system becomes greater than the inflow, the stored storm water is slowly
released back into the system.
Another possible use of such facilities is the storage of the heavily
polluted "first-flush" portion of storm water and then subsequent release
to a sanitary sewer for treatment.
One application cited in the literature (34) was in Fairfax County,
Virginia. A supermarket stores surface runoff in an underground tank to
supplement city water for use in an air conditioning cooling tower system.
The costs of various capacity structures which have been constructed
for combined sewer overflows were compiled by Lager and Smith (36) and
are presented in Table F-5.
Infiltration Systems
An infiltration system temporarily stores runoff and allows its per
eolation into the soil. (34) The main purpose of these systems is to control
and reduce the quantity of stormwater runoff, although secondary benefits
are present. Infiltration can also serve to artificially recharge ground-
water. Other benefits include conservation of water and land, avoidance of
hazards of standing water associated with other methods, minimizing dam-
age to the environment, and having an aesthetic ally-pie as ing appearance in
most cases. (35)
Infiltration Basin - This method of stormwater disposal has become
popular for two main reasons: increasing groundwater reserves and reduc-
tion in cost of conventional storm sewer systems. These facilities have
-------
Table F'5 SUMMARY OF STORAGE COSTS
FOR VARIOUS CITIES3
Location
Seattle, Wash. [14]
Control and monitoring system
Automated regulator stations
Minneapolis-St. Paul, Minn. [7]
Chippewa Falls, Wis. [18]
Storage
Treatment
Akron, Ohio [17]
Oak Lawn, 111. [16]
Melvina Ditch Detention
Reservoir
Jamaica Bay, New York City,
N.Y. [10,12]
Basin
Sewer
Humboldt Avenue, Milwaukee,
Wis. [3, 13]
Boston, Mass. [6]
Cottage Farm Stormwater
Treatment Station
Chicago, 111. [9]
Reservoirs
Collection, tunnel, and
pumpingc
Reservoirs and tunnels
Treatment
Sandusky, Ohio [19]
Washington, D.C. [4]
Storage,
mil gal.
32.0
--
2.8
2.8
0.7
53.7
10.0
13.0
23.0
4.0
1.3
2,736.0
2,834.0
5,570.0
5,570.0
0.2
0.2
Capital cost, $
3,500,000
3,900,000
7,400,000
3,000,000
744,000
186.000
950,000
441,000
1,388,000
'21,200,000
21,200,000
2,010,000
6,200,000
568,000,000
755,000
1,323,000,000
1,550,000,000
2,873,000,000
535,000
883,000
Cost per
acre,
$/acre
5,550
8,260
2,070
10,330
2,340
S40
6,530
6,530
3,560
2,370
3,150
5,500
6,460
11,960
36,000
29,430
Storage
cost,
J/gal.
0.23
--
0.26
0.26
0.62
0.03
2.12
0.92
0.50
4.74b
0.21
0.27
0.24
0.24
2.67
4.41
Annual
operation and
maintenance
cost, $
250,000
--
2,500
7,200
9,700
23,300
--
--
50,000
65,000
--
--
8,700,000
6,380
3,340
a. ENR 2000.
b. Includes pumping station, chlorination facilities, and outfall.
c. Includes 193.1 km (120 miles) of tunnels.
Note: $/acre x 2.47 - $/hectare; $/gal. x 0.264 - $/l; mil gal. x 3.785 Ml
-------
31
been used successfully in New York since 1933. (43) They have been used
in particular on highway projects because it is more economical to con-
struct short trunk storm sewer systems leading to such basins at various
locations rather than conventional long mains to reach suitable discharge
areas.
These facilities consist of excavations in relatively permeable soils
with a minimum depth of at least 10 feet between the floor of the basin and
the groundwater table. These facilities should also not be used for con-
struction areas where slopes are incomplete and unprotected, since the
fine sediments will permanently impair the natural infiltration characteris-
tics assumed during design of the basin. Side slopes of such basins should
also be properly vegetated, not only to prevent erosion and clogging but to
maintain infiltration rates through the slopes. The basin floor should be
deep tilled once each season to open soil pores and provide a well aerated,
highly porous surface texture. (34) Sediment removal should also be
accomplished during this tilling operation.
Diffusion and Infiltration Wells - Diffusion wells are normally large
diameter vertical shafts constructed of precast concrete sections, often to
depths between 100 and 200 feet. They have been effectively used in New
York (43, 34) to correct the results of inadequate design or maintenance of
recharge basins. However, a large basin is necessary to store storm water
prior to disposal in the well, and therefore they are not alternates to
basins.(34)
-------
32
Infiltration wells are deep, small diameter wells more often used in
conjunction with a detention basin. The criteria established for the applica-
bility of infiltration wells are as follows (34): a) when land availability
restricts or prevents construction of an adequate-sized infiltration basin;
b) where highly permeable soil exists below impervious surface soil of
such depth exceeding the limits of simple excavation; c) when no alterna-
tive site is available for basin construction in more favorable soils; and
d) when well cost is less than conventional drainage or where topographic
or geometric features so dictate.
With direct injection of storm water into aquifers that may serve as
water supply sources, there is a distinct possibility of a pollution problem.
This possibility diminishes with lower permeabilities and distance to the
withdrawal point. Careful consideration should be given to the character-
istics of the storm water, the characteristics of the aquifer, and its pres-
ent and potential use as a source of water.
Shallow Infiltration Wells, Pits, and Trenches - These facilities
are generally constructed on sites where limited detention capacity is
required and suitable soils avail. They are generally constructed by exca-
vating and backfilling with gravel or stone. The well is generally greater
than five feet deep and from two to five feet in diameter. The pit is simi-
lar to the well but its surface dimensions are longer and wider. The
trench is generally less than five feet deep and narrower than the pit.
A common use for these facilities is the storage and disposal of
runoff from roof areas. They have also been used to intercept runoff from
-------
33
parking areas and driveways. One example of a dry-well system is in
Germantown, Maryland where five wells having a storage capacity of 800
cubic feet control drainage from a 1.4-acre site. An infiltration trench
is used to control runoff from a one-acre parking lot in Gaithersburg,
Maryland. The trench has a storage volume of 1, 970 cubic feet. (34) Both
facilities are reportedly filled with two-inch diameter washed gravel and
from dimensions given, the well and trench systems require 3. 9 and 4. 2
cubic feet of excavation to provide one cubic foot of stormwater storage,
respectively.
Porous Pavement - Porous pavement is a pavement that is permeable
to water, durable with age under traffic, and is adequately supported by
base and subgrade materials under conditions of water saturation. (44) In
terms of cost and practicality, porous pavement should be made of conven-
tional paving materials and applied at the site by conventional equipment.
Of all materials considered, an open-graded hot-mix asphaltic concrete
meets all these requirements.
The asphalt paving mixes may be designed and produced from a wide
range of aggregate blends varying from course to fine particles. Porous
asphalt mixes have been classified into three types according to water infil-
tration rates: a) less than 5 inches per hour; b) 5 inches per hour to 25
inches per hour; and c) greater than 25 inches per hour. (44)
Roads designed with grassed, swale drainage and porous asphaltic
concrete were found to be generally more economical than conventional
-------
34
asphaltic concrete roads with storm sewers and catch basins. Other bene-
fits include groundwater recharge, improved skid resistance and thus
traffic safety, preservation of vegetation, relief of flash flooding, and
aesthetic benefits from use of colored porous surfaces.
Porous pavements require proper design of subgrade and subgrade
drainage provisions. Higher porosity pavements should be used to pre-
vent clogging of the surface under heavily polluted conditions. Shoulder
slopes must be protected from erosion by lateral drainage from the road-
way into adjacent drainage channels.
Parking lots and playgrounds were reported to cost from $1. 00 to
$2. 20 per square yard more than conventional asphaltic concrete surfaces,
but the difference was thought to be largely a result of higher Asphalt Insti-
tute specifications in contrast to those for designs typically installed. (44)
A cost comparison of porous asphaltic pavements to conventional
asphaltic pavements with storm drainage are presented in Table F-6.
Aeration of Lawns - Periodic perforation of golf courses has been
used to increase infiltration and aeration. Apparently, urban lawns have a
very low infiltration rate in comparison to woodland and natural grass-
lands, and methods of increasing this infiltration could reduce their runoff
rate and increase infiltration into the soil. (34) This would seem to be lim-
ited to individual homeowners and not a feasible manageable alternative to
be implemented by a stormwater pollution abatement program.
-------
TableF-6
COST COMPARISON OF POROUS PAVEMENT AND CONVENTIOr.'AL+PAVL'MENT WITH STORM DRAINAGE (44)
Type of Pavement
Parking Lot
Res i den t i a ] S tree t
Low-des i gn
H i cjh-des i gn
Business Street
Suburban development
Ci ty
County Road
H i ghway
Two- lane
Four- 1 an e
Asphal t
Cone re te
P 1 ayg round
Porous Pavement
Cost
($/y
6.32 -
6.33 -
6. 13 -
6.65 -
6.99 -
6.01 -
6.80 -
8.16 -
8.23 -
4.35 -
Range
2)
6.1*0*
6.37*
6.56
6.99
8.32
6.8?
7-92
8.79
9.04
it. 3 6*
Average Cost
($/y2)
6.36
6.35
6.38
6.38
7.66
6.44
7-36
8.48
8.64
4.36
'Conventional Pavement
Cost Range
($/y2)
3-65 - 5-81
4.80 - 9-60
8.35 - 12. 10
6.90 - 9-90
14.20 - 22.20
7.24 - 13-23
8.54 - 20.45
16.36 - 31 .40
17-76 - 33.90
3- SO - 5-20
Average Cost
(S/y2)
^73
7.20
10.23
8.40
18.20
9.20
14.50
23.88
25-83
'(.55
-Range reflects differences in excavation costs.
-(-Conventional asphaltic concrete pavement with curbs and gutters.
-------
36
Collection System Controls
Collection system controls are those alternatives which pertain to
the interception and transport of wastewaters. Examples of such controls
applicable to storm sewers are sewer flushing and cleaning, catch basin
cleaning, and infiltration/inflow controls. Other collection system control
alternatives such as sewer separation, regulator devices, and remote
monitoring and control structures were designed specifically for combined
sewers and are generally only applicable to such large systems. There
is a probability of adaptation of the principles of some of these methods to
separate storm sewers, but due to the lack of documentation in the litera-
ture, and because separate sewers are generally required to carry a larger
volume with much larger flow variation, such controls will not be consid-
ered further herein.
Periodic Sewer Flushing and Cleaning - Although this alternative
would serve to abate pollution of a waterway by the simple process of re-
moving pollutants from availability, it is used as a maintenance procedure
to unclog storm sewers and improve hydraulic capacity. It is also gener-
ally limited to small pipelines and infrequent applications. (36) Studies
regarding sewer cleaning have had as their purpose determination of clean-
ing costs rather than the effect of cleaning upon water quality. (45, 46) It
was concluded (46) that the costs to prevent of sediment entering the sewers
were substantially lower than the costs of removing the sediment from
sewers. Therefore, although such measures are obviously helpful in reduc-
ing pollution, they would not be a feasible stormwater management
-------
37
alternative due to the physical size of most sewer systems and the resulting
costs that would be associated with such a program.
Catch Basin Cleaning - Catch basins are reasonably effective in
removing coarse inorganic solids from runoff but are ineffective in remov-
ing fine solids and most inorganic matter, especially if they are full. It is
the general conclusion from the literature that proper maintenance and
cleaning of these structures is expensive, (45) and a regular clean-out pro-
gram would be required to remove a significant amount of the pollutants
entering them. According to Sartor, et al, (26) "where a simple stormwater
inlet structure would suffice, it is probably desirable to get rid of the catch
basin, either by replacing it or by filling it in. " It would seem that concen-
tration of maintenance efforts on regular street cleaning would be of more
benefit to pollution abatement than catch basin cleaning.
Two reported costs of removing solids from catch basins (40) were
$600 per ton in Chicago and $62 per cubic yard in California.
Infiltration/Inflow Control - Infiltration is that volume of water which
enters sewers from groundwater sources such as building connections,
broken, cracked, or corroded pipe, improper connections, and manhole
walls. Inflow is that volume of water which is discharged into sewers from
roof leaders, cellar and yard drains, foundation drains, commercial and
industrial discharges, and manhole covers. These "problem" flows and
their methods for control and prevention are normally associated with com-
bined and separate sanitary sewers, but the same general sources are also
characteristic of storm sewers. The reason for their concern with regard
-------
38
to sanitary sewers is that all flows entering the sewage collection system
are treated equally at the plant, whether or not they are intentional flows.
In the case of storm sewers, it is possible for such sources to hydraulic ally
overload the design capacity of the system, especially if they are from roof
drains and other such direct input sources where very high inflow rates are
possible and detention is desired.
Control of infiltration is accomplished structurally by adequate
design, construction, inspection, and testing of new sewers and by proper
survey and corrective measures in old sewers. If the infiltration is not a
result of serious structural failure such as broken pipe, it is probably
not of as much significance to stormwater management as it would be to
wastewater management. The volume of such infiltration may be in the
range of 5, 000 gallons per mile per day for an 8-inch pipe to 12, 000 gallons
per mile per day for a 24-inch pipe. (53) Although such volumes are signif-
icant to sanitary sewage treatment, the flow rates (. 01 and . 02 cfs respec-
tively) are insignificant when compared to the capacities of the pipes. In
summary, normal infiltration is not believed to be a matter of concern with
regard to abatement and control in stormwater management.
Inflow, on the other hand, could be a major problem when the source
is a large impermeable area such as a roof or parking area. In one example
of a 10, 000-square-foot roof drainage system (35) which was restricted to
a maximum ponding depth of 3 inches from a 3. 2-inch rainfall, the resulting
peak flow would be 40 gallons per minute (0.1 cfs). The "average" runoff
-------
39
rate for this rainfall from the 10, 000 square feet with no roof control sys-
tem would be 0. 74 cfs. Thus, depending on the rainfall and surface area
characteristics, inflow from a relatively small drainage area could produce
a very significant effect upon a storm sewer or other type drainage system.
Correction of inflow conditions is more dependent upon regulatory
action on the part of local governmental officials than on construction
measures. If elimination of existing inflows is deemed necessary due to
adverse effects upon sewer systems, more restrictive sewer-use regula-
tions have to be invoked. (36)
Vegetative Cover
Vegetation is the most versatile of all the techniques to reduce the
pollutional aspects of storm water in that it can be used for abatement,
control, and treatment with equal effectiveness.
Probably the most important measure in the abatement of pollution
associated with erosion and sedimentation is the use of vegetation, both
in urban and rural areas. The maintenance of a good vegetative cover will
in almost all cases provide maximum erosion control and prevention,
though not total control. In addition to physically holding the soil and reduc<
ing runoff velocity, vegetation can act as a filter to remove particles
already in suspension. Another benefit is the potential treatment character-
istics of vegetation. These are more commonly associated with land treat-
ment alternatives, specifically spray irrigation and overland runoff.
-------
40
In a study in Tucson (47), a grass covered native soil filter was
tested for effectiveness as a treatment measure for urban storm runoff.
The grass alone was attributed with COD, SS, VSS, turbidity, total coli-
form, and fecal coliform reductions of 19, 34, 26, 97, 84, and 50 percent
respectively.
Also, a number of the "control" techniques described in this report
require the use of vegetation to function properly and reduce the frequency
of maintenance.
The three general categories of practices used by the Soil Conserva-
tion Service to reduce or control erosion are vegetative, non-vegetative,
and engineering. (48) The vegetative methods include establishing a living
cover of grass, shrubs, ground cover, or trees. Non-vegetative measures
include mulches, sprays, chemicals, and plastic covers, while engineering
measures consist of the structural techniques used to control runoff.
Vegetative measures are divided into temporary and permanent
categories, where the temporary measures are used only until permanent
stabilization is accomplished. (49) Table F-7 presents examples of tem-
porary vegetation species, seeding rates, ans seeding dates applicable to
Delaware. (49) Information regarding types, fertilization, and maintenance
of permanent vegetative cover applicable to Delaware is presented in
Tables F-8 and F-9.
Mulch is a natural or artificial layer of plant residue or other mater-
ials placed on the soil surface. Although it is a separate, non-vegetative
means of preventing erosion, it is normally used in seeding operations of
-------
TABLE r
TEMPORARY SEEDINGS AND SEEDING DATES (4<^
SPECIES
Barley
Wheat
Rye
Ryegrass (Italian)
Annual , common
Sudangrass
SorghumxSudan
(hybrids)
Sorghums
Millet (Pearl)
Foxtail (German)
Buckwheat
Winter Oats
Spring Oats
Korean lespedeza
(Inoculate seed)
SEEDING DATES
SEEDING RATES Feb. 1 May 1 Aug. 15
Per Acre
2 1/2 bu.
2 1/2 bu.
2 1/2 bu.
35 Ibs.
30 Ibs.
30 Ibs.
35 Ibs.
35 Ibs.
50 Ibs.
2 1/2 bu.
2 1/2 bu.
25 Ibs.
Per 1000 Sq. Ft. May 1 Aug. 1 Nov. 15
2.75 Ibs. x x
3.50 Ibs. x - x
3.25 Ibs. x - x
.30 Ibs. x - By 9/10
.70 Ibs. x
.70 Ibs. x
.80 Ibs. - x
.'30 Ibs. - x
June
1.15 Ibs. - July
2.00 Ibs. - x
2.00 Ibs. x -
.60 Ibs. xx
Summer plantings may require irrigation to succeed.
-------
TABLE F-0
SOILS, SEED MIXTURES, DATES, FOR SEMI-PERMANENT TO PERMANENT SEEDINGS (4*0
MIXTURES
1. 'Kentucky 31' tall fescue
2. 'Kentucky 31' tall fescue
Korean lespedeza
3, 'Kentucky 31' tall fescue
Sericea lespedeza
4. 'Kentucky 31' tall fescue
Crownvetch
(Droughty Areas)
5. 'Kentucky 31' tall fescue
Red top
(Droughty Areas)
6. Weeping lovegrass
Sericea lespedeza
(Poorly Drained Areas)
7. 'Kentucky 31' tall fescue
Reed canarygrass
(Shaded Areas)
8. 'Kentucky 31' tall fescue
Creeping red fescue
(Saline & General Areas)
9. 'Midland' or 'Tufcote'
Bermudagrass*
10. Perennial Ryegrass
PLANTING
Lbs/Ac
60
50
15
50
20
40
15
30
5
4
25
30
10
30
12"
Centers
35
RATE SEEDING DATES
Lhs/1000 Feb. 1 Aug. 15
so. ft. May 1 Nov. 1
1.40 x x
1.15 x By
0.35 Sept. 15
1.15 x By
0.50 Sept. 15
0.90 x By
0.35 Oct. 1
0.70 x x
0.10
0.10 Feb. 1
0.60 Auq. 15
0.70 x x
0.70
0.70 x x
12'
Centers May to July 15
0.80 x x
Inoculate seed of crownvetch, Korean lespedeza, and sericea lespedeza immedi-
ately before seeding.
*Overseed with Korean lespedeza at the rate of 10 Ib/ac.
All of the above mixtures except 6 and 9 can be seeded at any time, providing
the sites arc mulched. The possibility of failing to get a stand established
is greater, however, when the optimum seeding dates are ianored. This is
especially true during June and July unless the site is irrigated.
-------
TABLE
MAINTENANCE, FERTILIZATION, AND MOWING FOR PERMANENT SEEDING (4 ^ )
Mixture
No. Seeding Mixtures
1,2 Perennial Ryegrass 10-10-10
5, 7 or Tall Fescue
8, 10 makes up 70% or
more of cover.
FERTILIZATION RATE
Formulation Lb/Ac. Lb/1000
SQ. Ft.
500
Time
Mowing
11.5 Fall. *Not closer than
Yearly, or as needed. 4" if occasional
mowing is desired
Crownvetch
0-20-20
400
9.2 Spring.
Year following
establishment and
every 4-7 yrs.,
thereafter
Do not mow.
Fairly uniform 5-10-10 500
stand of Tall
Fescue & Sericea
lespedeza or
sweet clover.
Weeping lovegrass 5-10-10 500
and Sericea les-
pedeza. Fairly
uniform plant
distribution.
Bermudagrass 10-6-4 500
11.2 Fall.
Year following
establishment and
every 4-5 yrs.,
thereafter
11.5 Spring.
Year following
establishment and
every 3-4 yrs.
thereafter
11.5 Each May; more often
if intensively
managed.
Not required. Not
closer than 4"
if occasional mow-
ing is desired,
and then in fall
after sericea has
matured.
Not required. Not
closer than 4" if
occasional mowing
is desired, and
then in fall after
sericea seed has
matured.
Depends on
function of area.
*Keep mowers off slopes that might be damaged by wheel tracks,
-t
C>
-------
44
temporary and permanent vegetation to reduce erosion and evaporation
losses, provide insulation from solar energy, and other benefits to aid
in establishment of vegetation. (50)
Erosion and Sediment Control
Several of the control measures described previously are effective
erosion and/or sediment control measures, although most have as the
principal objective flow rate modification. The purpose of this subpart
is to highlight the need for measures to specifically control sediment
removal and deposition, particularly in rural or agricultural areas.
"The development of technology for the control of erosion and sedi-
ment has been underway since the federal government became involved
with the problems associated with the drought of the 'dirty thirties'. " (50)
Since that time, conservation practices developed and put into use on farms
include terraces, grassed waterways, contour ploughing, cultivation, and
strip cropping. The Soil Conservation Service has been the major force
in the implementation of such measures in that it "... is available to pro-
vide soil, water, and related resource technology to all people who own,
control, or plan the use of land. "(48) In addition to the vegetative con-
servation measures, many structural measures were developed including
diversion channels, temporary check dams, level spreaders, backslope
drains, gabions, chutes on slopes, and splash pools or pads at culverts.
Obviously, such measures are applicable not only to farming but to many
uses, including construction sites and hydrographic modifications (i. e.,
drainage channels and impoundments).
-------
45
The Soil Conservation Service has compiled such information on
vegetative and structural conservation measures (reference 48) as
applicable to the State of Delaware. Included in the publication are the
definition, purpose, applicability, and site conditions for specific measures
to prevent or control erosion from runoff. Another excellent reference (41)
compiled by the University of Delaware for the EPA includes not only such
measures applicable to rural areas, but also specific detailed descriptions
and drawings of measures to control runoff and erosion in urban areas.
It is believed that a listing and detailed description of all the control
measures available in the cited and other publications would be only unnec-
essary repetition. For this reason, the references are only mentioned
here for future retrieval of details as desired. When considering alterna-
tives for specific erosion and sediment control, the personnel of the Soil
Conservation Service are available to provide technical assistance and
should be consulted on all projects of this nature.
A study on the effects of sediment control measures during construc-
tion was performed on a 21.1 square-mile drainage area of the Anacostia
River in Montgomery County, Maryland. (68) Stream flow and sediment
were monitored from 1962 to 1972, during which time urban land increased
from 3. 5 percent in 1959 to 20 percent in 1971. In 1967, the county council
passed an ordinance requiring erosion and sediment control plans be
approved along with preliminary subdivision plans prior to construction.
The approval control measures included: a) exposure of the least amount
-------
46
of soil at any one time during construction; b) mulch and temporary vege-
tation; c) diversion berms; d) level spreaders and stabilized waterways
to reduce slope erosion; and e) sediment basins to trap sediment not
retained by other control measures. A voluntary program begun in 1965
was not successful in encouraging developers to include sediment control
measures.
Although a number of factors could have been responsible for the
decrease in sediment discharge, it was stated that "the factor most likely
responsible for the decreased sediment load between 1968 and 1972 is the
sediment-control program begun in 1965. " It was estimated that the pro-
gram prevented 110, 000 tons of sediment from being transported from the
basin between 1968 and 1972, or an average of 1, 300 tons per square mile
per year. The sediment actually discharged during this period from the
drainage area, which was reported to be in the "Piedmont physiographic
province," was estimated to be about 70, 000 tons or 829 tons per square
mile per year.
During the 10-year study period, a seasonal variation of suspended
sediment was observed. Average monthly sediment discharge during
1963-1972 ranged from 718 tons in December to 3,800 tons in June. Fall
and early winter (October to January) was a period of relatively low sedi-
ment discharge while early spring and summer were periods of high
I sediment discharge. October through January is characterized by low pre-
cipitation, low intensity storms which are not conducive to heavy erosion
and sediment transport, while the remainder of the year is characterized
-------
47
by intensive rainfall from convective storms which can cause severe ero-
sion. For the 10-year period, virtually all of the sediment was transported
during these convective storms (76 percent of the sediment was transported
on 86 days representing about 2. 4 percent of the time).
A summary of the costs for some of the previously-mentioned meth-
ods that are generally used to control sediment were compiled by Black,
Crow, and Eidsness (40) and are presented in Tables F-10 and F-ll.
-------
TABLE F-/0
COSTS OF SEDIMENT CONTROL METHODS (40)
Cost ($ per cubic yard)0
Method
Hydromulching
Removal from
Streets, Parks,
Playgrounds,
etc.
Removal from
Basements
Removal from
Sewers (Hydro-
flush Method)
Sediment Basins
(earthen, small)
Virginia
2.56
6.60
65.00
62.00
2.20
California Percent Removal
27.903 About 95
8.00 Not Applicable
77.00 Not Applicable
.68. 00 Not Given
About 70
Note high variability in costs, which are affected by local
credibility factors and labor costs.
D
Not given by geographic region.
Project life assumed to be 10 years.
TABLE f-l
COST SUMMARY OF SEDIMENT CONTROL ALTERNATIVES (40)
Method
Berms, ditches
Small sedimentation basins
Surface stabilization
(seeding, chemicals, etc.)
Cost
$1.25-2.80 per linear foot
$1,500 each
$209-567 per acre
Engineering structures
$55 per acre
-------
49
SECTION IV
TREATMENT MEASURES
The treatment of wastewater usually involves the removal, separa-
tion, or change-in-state of the contaminants in the waste stream. (37) The
technology exists today to treat stormwater runoff, but the desired goals of
such treatment should be outlined along with their associated economics.
The two main goals of treatment of storm water, as evident in the litera-
ture, are a) reduction of the pollution potential of such wastewater upon the
receiving waters of the nation; and b) the recovery of a potential resource
for domestic, industrial, agricultural, or recreational use. Also, treat-
ment as a stormwater management alternative has essentially been consid-
ered only for urban stormwater runoff. Possible exceptions may include
storage and land treatment measures for runoff from feedlot operations and
retention ponds in urban and semi-urban watersheds to reduce runoff and
associated sediment pollution. The apparent dividing line between control
and treatment alternatives would be the further clarification of the word
treatment to mean "conventional" treatment, more commonly associated
with wastewaters which contain all or a considerable portion of sanitary
sewage. Further references to treatment in this report will mean such
conventional facilities, and it will be assumed that this measure will apply
only to urban land use where there is either an existing separate storm
sewer or drainage system or where there will be, as in the case of future
development.
-------
50
Treatment alternatives consist of physical means such as screening
and sedimentation as well as more process-oriented means including
physical, chemical, and biochemical treatment. Examples of such pro-
cesses include: a) dissolved air flotation; b) ultrahigh rate filtration;
c) chemical clarification; d) contact stabilization; and e) high rate trickling
filters.
Considering the characteristics and constituents of storm water, it
is evident that treatment would be desirable from the pollution abatement or
control standpoint. There are statements in the literature which indicate
that the 1983 goals of the Act will not be met by upgrading municipal and
industrial point discharges alone and that storm water will have to be given
equal consideration.
Conventional sewage treatment processes are designed to produce an
effluent that can be assimilated by the receiving water without violating
pre-set water quality standards which do not generally recognize the future
use of the effluent as a source of municipal supply or other specific water
use. Similarly, conventional water treatment processes are generally not
designed to treat raw water having a quality approaching that of sewage
plant effluent; rather, a more moderately contaminated and turbid water.
Therefore, before the alternative of treatment is considered, the intended
use of the storm water after treatment should be established so that unnec-
essary processes or units may be avoided.
Previous research into the reuse or reclamation of wastewater has
apparently been focused on municipal sanitary sewage effluent or combined
-------
51
sewer effluent after treatment and not specifically on separate storm water.
Mallory (52) noted that "no local reuse of storm water was reported in the
literature surveyed, but numerous applications of sub-potable water sys-
tems, including reclaimed wastewater, were reported. " The only citation
of stormwater reuse covered in this research effort was the previously
cited example of the supermarket storing surface runoff and using it
directly in the air conditioning system. (34)
The reuse of renovated municipal wastewater in industry, however,
is well documented. A survey of such industrial use was made by Weddle
and Masri (54) who cited twenty-six examples across the country. A sum-
mary of the quality characteristics of the renovated wastewaters before
industrial in-plant treatment and use for thirteen of the industries is pre-
sented in Table F-12. When compared to the available quality parameters
reported in Section D of this report, it is apparent that storm water quality
(prior to any treatment) is equivalent or superior to the municipal effluent
presently being used. It should be noted here that the use of municipal
effluent rather than storm water by these industries was not an oversight,
but that they are located in arid and semi-arid regions of the country where
there is not sufficient rainfall to provide a supply as reliable and predict-
able as the daily flows from sewage treatment plants. These documented
reuses of wastewater are presented here to show the potential resource
value of storm water in one specific area, namely industry. The use of
storm water by industry would have the added benefits of removing it as an
-------
TABLE F-iZ
Renovated wastewater quality characteristics before industrial in-plant treatment (54)
Calcium Hardness Alkalinity Suspended Dissolved
mg/l mg/l mg/l Solids Solids
Industrial User pH CaCO3 CaCO3 CaCO3 mg/l mg/l
Standard Oil, Lima, Ohio 88 208
Nevada Power, Las Vegas,
Nevada 7.4 245 610
Black & Decker, Hamp-
stead, Maryland 7.5
Dow Chemical, Midland,
Michigan 7.3
El Paso Products,
Odessa Texas 7.0 230 410
Texaco, Amarillo, Texas7. 3 70 255
Southwestern Service,
Amarillo, Texas 7.4 75 285
North American, Canoga
Park California 8.8 40 130
Bethlehem Steel, Balti-
more, Man/land 6.9
Lamsdale Power, Lams-
dale, Pennsylvania 7.5
City of Burbank,
California 7.8 110 150
Los Alamos Lab, Los
Alamos New Mexico 7.0 40
Champlin Petroleum,
Enid, Oklahoma 8.4 200
139
255
150
320
275
90
200
250
150
450
28
20
10
10
10
18
35
25
60
1540 .
630
600
1450
1300
1250
560
300
720
400
800
BOD Phosphate Ammonia Silica Chloride
mg/l mg/l mg/l mg/l mg/l
16
110
17
10
10
15
8.0
20
80
8.0
25
45
20
20
25
70
35
15
40
30 10
17 30
18
7.0 30
20 20
20 20
17
40
15 60
30
320
300
475
300
370
75
70-200
95
110
30
250
-------
53
available direct pollution source and assuring its treatment prior to even-
tual release to the environment.
Storm runoff has been stored and reused locally for centuries. Many
island communities such as Gibralter, Guam, and Bermuda have been en-
tirely dependent on such efforts to store rainfall to supply their needs. (52)
In this country, the Department of Agriculture published handbooks to
assist in constructing farm cisterns as supplementary water supplies in
areas where sufficient groundwater is not available or is not of acceptable
quality.
The domestic uses of reclaimed wastewater have generally been
limited to lawn watering, toilet flushing, and other nonpotable uses. Four
such examples as cited by Mallory (52) are:
a) Sites of Grand Canyon National Park, where treated domestic
wastewater was first used in the park in 1926 for toilet flush-
ing, lawn sprinkling, cooling water, and boiler feedwater at
the power plant.
b) Pomona, California, where municipal sewage plant effluent
has been used for domestic irrigation of lawns and gardens
in a suburban home development since 1929.
c) San Diego State Teachers College, California, where sewage
effluent was first used for lawn and shrubbery irrigation in
1931.
d) Golden Gate Park, San Francisco, California, first used acti-
vated sludge plant effluent in 1932 for lawn watering and main-
taining water levels in some of the park lakes.
Probably the most noted example of domestic reuse of wastewater is
the experience of Chanute, Kansas. (55) A drought dried up the local water
supply and for a period of five months (October 1956 to February 1957),
-------
54
effluent from the city's secondary treatment plant was diverted to the water
supply reservoir. It was estimated that the treated wastewater was re-
cycled through the city at least eight times. A similar instance occurred
in the fall of 1956 in Lyndon, Kansas, and in both instances the municipality
itself made the decision to reuse the sewage effluent. (56) Further docu-
mentation of such reuse being publically accepted is apparently lacking in
the literature, although the aesthetics of such reclamation are still con-
sidered to be an important factor. (52) It is interesting to note that many
municipalities over the country draw their water from inland streams and
lakes that are in fact the diluted sewage effluents of upstream cities.
"Although the presence of such pollution is generally known, consumer
acceptance of the water does not appear to be reduced appreciably. "(56)
Therefore, since the use and acceptance of municipal effluent has
been documented, and since it is generally agreed that urban storm water
is of better quality than such effluents, there should be very few problems
associated with public acceptance of any alternative to reclaim and reuse
storm water for all domestic purposes.
Agriculture would be an ideal use for urban storm water with little or
no treatment. However, such areas are generally too distant from munici-
palities, making the cost of collecting and transporting runoff prohibitive.
Although most state health standards do not permit the use of sewage for
truck farming regardless of the degree of treatment, there are apparently
no such controls over stormwater reuse. As mentioned previously, appli-
cation of effluents to the land is an acceptable form of sewage treatment,
-------
55
and as such could be a viable treatment alternative or process for storm
water under the proper conditions.
The use of treated stormwater effluent for recreation and ground-
water recharge have been mentioned previously in the discussion of control
measures. The use of retention or detention ponds can also serve the dual
purpose of recreation and recharge, whereas infiltration basins serve only
to remove the storm water from a surface area into the groundwater. The
treatment meastre generally associated with these uses is simple
sedimentation.
Although there are a number of examples and studies in the literature
regarding the treatment and reuse of domestic effluent and combined sewer
overflows, such data on separate stormwater flows are scarce. One such
study by Mallory (52) had as its objective the development of systems that
could control the stormwater pollution of a lake having the secondary bene-
fits of reusing the water to supplement the water demands of a community.
The conceptual design and cost estimates were prepared for the three cases
of: a) potable reuse; b) sub-potable reuse; and c) pollution control. It was
determined that the use of local storage and treatment represented a fea-
sible and economical method for stormwater pollution control, and that the
use of treated water can supply a large portion (approximately one half) of
the freshwater demands of a typical urban residential community.
Thus, if the problems associated with costs of treatment of storm
water and its remoteness to designated areas of beneficial use or reuse can
be solved, treatment can be a feasible stormwater management alternative.
-------
56
However, in citing examples of stormwater treatment, Lager (37) stated
that "primary emphasis should be given first, to establishing control over
the flows and secondly, to treating at the objective levels. " In general,
conventional primary or secondary treatment, or physical-chemical treat-
ment at storm sewer discharge points would be prohibitively expensive,
and often physically impossible, due to large numbers of discharge points,
land requirements, or required sewer system changes.
Physical Treatment
Physical treatment processes are those in which the application of
physical forces predominates. Typical examples include screening, sedi-
mentation, flotation, and filtration, the operations of which may or may not
include the addition of chemicals.
Physical treatment processes have the advantages of a) high efficien-
cies of removal over a wide range of flows; b) can be easily automated; and
c) can stand idle for long periods of time without affecting treatment effi-
ciency. The predominant pollutant removal by physical processes is sus-
pended solids, although secondary removal of other pollutants associated
with solids is also accomplished (i.e., BOD, COD, and toxic materials).
Sedimentation - Sedimentation is the most commonly used method for
removing suspended solids. Removal efficiencies of primary clarifiers
are usually about 30 percent for BOD and 60 percent for suspended solids.
Conventional sedimentation may not be the most economical means due to
a) long detention times that require large size of such facilities; and b) the
low removal efficiency for colloidal material. (36)
-------
57
The effects of sedimentation on urban land runoff in Durham, North
Carolina were studied by Colston (19) both with and without chemical addi-
tion. Plain sedimentation for 15 minutes was found to remove an average
of 61 percent COD, 77 percent suspended solids, and 53 percent turbidity.
Based on jar tests, alum was found to be the most effective coagulant and
at an average dosage of 57 mg/1 and subsequent to the addition of alum,
sedimentation removed 84, 97, and 94 percent of the COD, suspended
solids, and turbidity, respectively. The ranges of the average raw sample
concentrations for the tests were apparently 171 to 496 mg/1 for COD, 340
to 887 mg/1 for suspended solids, and 213 to 483 JTU for turbidity. Accord-
ing to Colston, "plain sedimentation, being much less costly than chemical
coagulation, removed a significant portion of organics and solids and should
be considered an effective tool for preventing adverse effects of urban land
runoff on water quality management. "
A similar sedimentation/chlorination study was made by Weibel, et
al (61) on the runoff from a single storm event in Cincinnati, Ohio. Plain
sedimentation apparently did not produce the removal rates reported by
Colston, but this is probably due to the lower concentrations of pollutants
in the Cincinnati sample, which can have a substantial effect upon removal
rates. Table F-13 presents the removal rate versus time for plain sedi-
mentation as reported by Weibel. The variations in the BOD removal rates
with time were believed to have resulted from variations in laboratory
methods during analysis. (61)
-------
TABLE 'F-13
CONMIII-I.NT roNO NIK \T|MNS AND SI.THING CIIAK \C I I HISIICS (ll: LKIUN SI'OKM-
\\.VITK Kl NOI I I ROM \ SINt.l I. SIORM S '19,'<>5
27-UUI (II-H\) Kl sim.NIIAt . I K.III'-COMMI IUIM A HI V, ( IM INN \ I I. I HUD
C'onttitucnl
Nil X
NO. N
NO. N
Org. N S
I'O, 'Ti.iali I'O;
I'O, .Sol. I'O.
HOD
con
SS
VSS
K;iw
conceiilr;ilion
img l.i
0.2
0.05
0.5
1.4
1 .15
0.46
25.0
62.0
231 .0
38.0
_ _
10 min
0
0
0
14
4
0
40
1?
39
34
Kcmouil ;il
20 min
0
0
0
21
13
0
44
13
46
45
UT .staled x
60 min
_ .
'
0
0
o
43
13
0
20
IS
57
50
lllins; limes
4hr
.
0
0
0
S6
34
20
3 [
71
60
24 hr
0
. 0
0
'
39
0
48
47
87
84
1
[
-------
59
One solution to overcoming some of the disadvantages of conventional
sedimentation is to combine the sedimentation process with storage or
detention facilities (36), thus taking advantage of the dual use approach.
Since sedimentation will occur whenever the velocity of the storm water is
reduced by directing it into a structure having a larger cross-section than
the conveyance facility, control alternatives such as retention and detention
ponds will function as sedimentation basins also. This approach was taken
by Mallory (52) in the Columbia, Maryland study.
Another example cited by Lager (37) was a detention/chlorination
facility constructed in Boston (Cambridge), Massachusetts having a maxi-
mum capacity of 233 mgd which was reported to be the difference between
capacities of the incoming and outgoing interceptors at the site. The facility
consists of six parallel basins each 10 feet deep by 27 feet wide by 108 feet
long. It was estimated that for 80 percent of the storm events, this facility
provided a treatment time of 30 minutes or longer, and for 15 percent of
the storm events the flows will be totally contained. At the design flow
rate, it was estimated that 10 minutes of chlorine contact time was pro-
vided, resulting in an overall reduction in coliform counts approaching 100
percent. Suspended solids removal was estimated at 40 percent on the
average, with little or no BOD reduction attributed to "erratic results not
being weighted to the flow. "
Information on several combined system storage/sedimentation
facilities that have been constructed was compiled by Lager and Smith (36)
and is presented in Table F-14. In all cases but the Chippewa Falls,
-------
Table F-/4 SUMMARY DATA ON SEDIMENTATION BASINS
COMBINED WITH STORAGE FACILITIES
Lot it ion of facility
Ccttagc Farm Detention
and Chlorination Facility,
Cambridge, Mass.
Oxippewa Falls, Mis.
Columbus, Ohio
Whittier Street
Alum Creek
Humboldt Ave. ,
Milwaukee, Wis.
Spring Creek Jamaica
Bay, New York, N.Y.
Mount Clemens, Mich.
Lancaster, Pa.
Neiss Street,
Saginaw, Mich.
Size, Removal efficienc]
gal. storage facility SS BODj, %
a. In operation
1.3 Covered concrete 45 Erratic
tanks
2.8 Asphalt paved 18-70 22-74
storage basin
4.0 Open concrete 1S-4S 1S-JS
tanks
0.9 Covered concrete NAb NA
tank
4.0 Covered concrete NA NA
tanks
10.0 Covered concrete NA NA
tanks
b. In planning or construction phase
5.8 Concrete tanks
1.2 Concrete silo
J.6 Concrete tanks
r
Type of solids
removal equipment
Manual washdown
Solids removal by
street cleaners
Mechanical wash-
down
Mechanical wash-
down
solids by mixers
Traveling bridge
hydraulic mixers
Resuspension of
solids and mcchan-
eductors
Air agitation and
pumping
Mechanical and
manual washdown
a. All facilities store solids during storm event and clean
the interceptor can handle the solid water and solids.
b. NA - not available.
Note: mil gal. x 3,7«S.O - cu m
sedimentation basin when flows to
-------
61
Wisconsin project, settled sludge is stored until after the storm event, at
which time the contents of the tanks are slowly drained back into the
interceptor.
The advantages to sedimentation include: a) familiarity of the pro-
cess to design engineers and operators; b) the facilities can be automated;
c) the process provides for storage of at least part of the overflow; d) dis-
infection can be effected concurrently with sedimentation; and e) sludge
collection equipment can be added at minimal incremental cost. The dis-
advantages of sedimentation include: a) the land requirement is high;
b) when the process is used alone, the cost is high; c) only primary treat-
ment is afforded storm water; and d) some manual cleaning of most basins
is necessary after each storm event. (36)
The sizing of sedimentation basins is based on a number of vari-
ables, including the characteristics and size distribution of the particles
desired to be removed. In the case of storm water, this information is not
usually known and probably varies with time. The literature indicates that
urban storm water contains a substantial amount of colloidal and near-
colloidal particles for which the settling velocity approaches zero and the
detention time becomes infinite. The settling velocities of selected particle
sizes were compiled by Mallory (52) and are presented in Table F-15.
These may be used to determine theoretical overflow rates and dimensions
of sedimentation facilities. The cost of construction and operation of con-
ventional sedimentation facilities (primary and secondary clarifiers) is
presented in Figure F-l as a function of the surface area. The costs of
-------
6?-
- SETTLING VELOCITIES OF
SELECTED PARTICLES, AFTER HAZEN (52)
Particle Diameter Settling Rate
Kind of Material _ (uj _ (cm /sec)
Coarse sand 1000 10.0
Coarse sand 200 2. 1
Fine sand 100 0.8
Fine sand 60 0. 38
Fine sand 40 0.21
Silt 10 0.015
Coarse clay 1 0.00015
Fine clay 0.1 0.0000015
-------
SEDIMENTATION
100
L
D
a
7; 10
'.
T3
a
"
c
O
O
2
oC
d
2
Z
O.I
10,000
!OOO
100
0.1
I 10
SURFACE AREA-1000 SQ.FT.
10
'100
u
i
o
o
a
n
a
.
O
CJ
a
o
u
FIGURE F-l
DALLAS
-------
64
several combined stormwater storage /sedimentation facilities are pre-
sented in Table F-16, although their design criteria were not reported.
Dissolved Air Flotation
Dissolved air flotation is a unit operation used to separate solid par-
ticles from a liquid phase (i.e., water). Fine air bubbles introduced into
the water attach to solid particles and the resulting buoyant force of the
combined particle and air bubble is great enough to cause the particle to
rise. Particles which have floated to the surface of the water are removed
by skimming. Generally, the difference between the effective specific
gravity of the combined air bubble and solid particle and that of water is
greater than the difference between the specific gravity of the solid particle
and water. This results in higher particle removal velocities, which in turn
results in higher allowable overflow rates and shorter detention times than
conventional settling units. (36)
There are two basic processes for forming air bubbles: a) air is
dissolved under pressure into the wastewater and, upon release of the pres-
sure, comes out of solution in the form of bubbles; and b) wastewater is
saturated with air at atmospheric pressure and, upon application of a
vacuum over the flotation tank, air bubbles form by dissolution. The first
process is most commonly used. (36)
There are three methods for implementing the pressurization pro-
cess. The first method pressurizes the total flow and mixes it with air.
The second, referred to as "split flow" flotation, is where a part of the
-------
Table F-/£ COST OF STORMWATER SEDIMENTATION FACILITIES3
Location of facility
Size.'
mgd
Capital cost,
$/mgd J/acre
Annual
operation and
naintenance cost,
J/»gd
Cambridge, Mass.
Cottage Farm St6rm-
water Treatment
Station
Columbus, Ohio
Khittier Street
Alum Creek
Milwaukee, Wis.
Humboldt Avenue
New York, N. Y.
Spring Creek-
Janaica Bay
62.4 100,000
192
43
192
480
32.000
43,000
10,500 3.S60
44.000 6,530
1,240
260
a. ENR - 2000.
b. Maximum capacity assuming 30-minute detention time.
c. Includes pump station and screening facilities.
Note: mgd x 43.808 I/sec
-------
66
incoming flow is pressurized and aerated, then remixed with the remaining
portion of the flow before entering the flotation tank. The third method
pressurizes a portion of the effuent and recycles it to be mixed with the
incoming flow. The last two methods are used with larger units since only
a portion of the total flow is pressurized.
The advantages of dissolved air flotation include: a) suspended solids
and BOD removal are moderately good; b) the separation rate can be con-
trolled by adjusting the air supply; c) capital costs are moderate when con-
sidering high separation rates, high surface loadings, and short detention
times; and d) the system can be automated. Disadvantages include: a) high
operating costs compared to other physical processes; b) greater operator
skill required; and c) and provisions must be made to prevent wind and rain
from disturbing the flotage or suspended material removed by this unit
process. Lager and Smith (36) cited four example projects where air flota-
tion studies were demonstrated; however, all four studies utilized combined
sewer overflows rather than separate storm water. The studies also uti-
lized various kinds of chemical additives to aid in flotage formation. The
effectiveness of this process on removal of pollutants in separate storm
water is not known since no such research was found in the literature. A
summary of the removal rates by dissolved air flotation, both with and
without chemical addition, upon combined sewer overflow is presented in
Table F-17. The majority of the chemicals tested have been polyelec-
trolytes and ferric chloride, with the latter reportedly being the most
successful.
-------
67
Table F-/7 TYPICAL REMOVALS ACHIEVED WITH
SCREENING/DISSOLVED AIR FLOTATION
Without chemicals
Constituents
SS
VSS
BOD
COD
Total N
Total P
Effluent, mg/1
81-106
47a
29-102
123a
4.2-16.8
1.3-8.8
% Removal
56
53a
41
41a
14
16
With chemicals
Affluent , mg/1
42
18
12
46
4.2
0.5
-48
-29
-20
-83 '
-15.9
-5.6
1 Removal
77
70
57
45
17
69
a. Only one set of samples.
-------
68
The use of dissolved air flotation on separate storm water is appar-
ently untried. Because of the relative similarities in quality between
separate and combined sewer overflows (see Table F-18), the removal
efficiencies experienced with combined overflows should applyVwithin a
relatively narrow rangejfor separate stormwater runoff (urban). However,
because of the apparent complexity of the process when compared to other
alternatives, the widespread use of dissolved air flotation on separate
stormwater flows is probably not practical. The use of this process would
probably be limited to specific cases where there are special pollutants
that must be removed such as oil or other floating substances where
screens, sedimentation, or other such conventional physical processes are
ineffective.
The cost data for four prototype and pilot dissolved air flotation
facilities were scaled to a 25-mgd capacity (36) and are presented in Table
F-19. The costs are reported to include pretreatment devices. The avail-
able information was used to develop an equation, presented below, in which
Ca is the capital cost of the facility and Qa is the plant capacity in mgd.
Since particular design criteria were not reported, this equation probably
is representative of a range of such facilities:
Ca = 58,000 (Qa)0'84
Screens
Screens are used to remove almost all sizes of suspended material.
They range in size from 3-inch clear openings (bar screens) to 15 microns
-------
Table F"I8 GENERALIZED QUALITY COMPARISONS
OF WASTEWATERS
Type
Untreated municipal
Treated municipal
Primary effluent
Secondary effluent
Combined sewage
Surface runoff
BOD5,
mg/1
200
1J5
25
115
30
SS, Total coliforms,
mg/1 MPN/100 ml
200
BO
15
410
630
5 x
2 x
1 x
5 x
4 it
107
107
103
106
105
Total nitrogen,
mg/1 as N
40
35
30
11
3
Total phosphorus ,
mg/1 as P
10
8
5
4
1
Source: Data condensed from Tables 12 and 13, Section V. Values based upon flow-
weighted means in individual test areas.
-------
70
Table F-R DISSOLVED AIR FLOTATION COST FOR 25 MGDa(3&)
Plant location
Construction cost
including pre- .
treatment devices
Operation and
maintenance
Total cost,
«/l,000 gal.
Chemical cost
alone, */l,000
gal.
a. ENR - 2000.
b. Fort Smith used
Fort Smith,
Arkansas
(Estimated
cost)
$480,000
10.83
--
Milwaukee,
Steel tank
(Actual
cost)
$580,000
S.7S
4.17
Wisconsin
Concrete
tank
(Estimated
cost)
5686,000
--
--
hydraulic cyclones for pretreatment ;
Racine ,
Wisconsin
(Actual
cost)
$703,000
3.34
2.71
San Francisco,
California
(Actual Average
bid cost) cost
$1,760,000 $842,000
6.64
S.llc
Milwaukee and Racine used SO-mesh
fine screens; San Francisco used only bar screens.
c. Seventy-seven percent of total operation and maintenance cost, which is the average per-
centage the chemicals cost at Milwaukee and Racine.
Note: 4/1,000 gal. x 0.264 - f/1,000 liters
-------
71
(microscreens). Four classifications of screens with respect to opening
sizes are presented in Table F-20. (36)
The use of fine screens to remove sediment depends upon the
requirements and characteristics of the particular instance. However,
coarse screens or bar screens should be included as a pretreatment and
protection device for any treatment installation.
Microstrainers and fine screens remove from 25 to 90 percent of the
suspended solids and from 10 to 70 percent of the BOD. According to
Lager and Smith: (3 6) "additional studies on combined sewer overflow
strainers are warranted before removal efficiencies can be predicted with
any degree of accuracy... " If the use of screens is questionable with re-
spect to combined sewer overflows, their use on separate stormwater flows
is even more doubtful because of the lack of test data. A summary of the
general characteristics of fine screens is presented inTable F-21. Because
of the relatively high costs associated with the fine screens, their limited
treatment capabilities, and their questionable removal efficiencies for
storm water, they are not believed to be a viable alternative for storm-
water treatment.
Filtration
Filtration is a combination of particle transport and attachment. In
order for a particle to be removed, it must either adhere to the surface of
the filter medium or contact the solid-liquid interface of the filter me-
dium. (57) Particle transport is influenced by media size, filtration rate,
-------
Table F-2O CLASSIFICATION OF SCREENS (3k)
Opening
Classification
Bar screens
(> 1 in.)
Coarse screens
(1 to 3/16 in.)
Fine screens
(3/16 to 1/250 in.)
Microscreens
(< 1/2SO in.)
Mesh
--
--
3
4
6
8
9
10
14
20
28
35
48
60
80
100
150
230
400
Inches
3.0
2.0
1.050
0.742
O.S42
0.371
0.263
0.185
0.131
0.093
0.07-8
0.065
0.046
0.0328
0.0232
0.0164
0.0116
0.0097
0.0075
0.0058
0.0041
0.0026
0.001S
0.0009
Microns
--
--
1.651
1.168
833
589
417
295
246
180
147
104
65
38
23
Note: in. x 2.54 cm
-------
73
Tablef"-2.1 CHARACTERISTICS OF VARIOUS TYPES
OF SCREENS
Microstrainer
Drum
screen
Rotary fine
screen
Hydraulic
sieve8
Principal use
Approximate removal
efficiency, t
Main treatment
Pretreatment Pretreatment Pretreatment to
to other de- to other de- other devices
vices and vices and
main treat- main treat-
ment ment
BOD
SS
Land requirements,
sq ft/mgd
Cost, S/mgd
Can be used as a dry
weather flow polish-
ing device
Automatic operation
Able to treat highly
varying flows
Removes only par-
ticulate matter
Requires special
shutdown and
startup regimes
Screen life with
continuous use
Uses special sol-
50
70
~ 15-20
12,000
Yes
Possible
with con-
trols
Yes
Yes
Yes
7-10 yr
No
15
40
15-20
4,800
No
Possible
with con-
trols
Yes
Yes
Some
10 yr
No
15
35
24-62
8,000
No
Possible
with con-
trols
Some limita-
tion
Yes
Some
1,000 hr
Yes
--
--
20
5,600
No
No controls
needed
Yes
Yes
No
20 yr
No
vents in backwash
water
High solids concen-
trate volume, t of
total flow
0.5-1.0
O.S-1.0
10-20
< O.S
a. Information on hydraulic sieves is limited. Formal study on treatment of
combined sewer overflows is just beginning.
b. Based on a 25-mgd plant capacity.
Note: sq ft/mgd x 2.12 » sq m/cu m/sec
$/mgd x 0.38 = $/cu m/sec
-------
74
fluid temperature, and density and size of the particle. O'Melia and Storm
(58) report that particle size influences particle transport in water filtra-
tion to a greater extent than any other parameter. Three physical aspects
of filtration that should be noted are: a) filtration is a dynamic process
depending upon depth and detention in the filter; b) the removal of suspended
particles in a filter is proportional to the concentration of the particles;
and c) the material removed from suspension clogs the filter. (57)
Historically, filtration has been used for domestic water treatment
rather than for conventional wastewater treatment because of the rapid
clogging, due mainly to compressible solids which are strained out at the
surface of the filter medium. Storm water, on the other hand, contains
a larger fraction of discrete, noncompressible solids that are more easily
filtered. (36) However, filter runs would be much shorter than in conven-
tional water treatment due to the higher solids content of the influent.
The only examples found in the literature which approximate stormwater
filtration were discussed by Lager and Smith. (36) These have all been
demonstration projects to evaluate filtration of combined sewer overflows.
One succesful project was in Cleveland, Ohio, where a dual-media filter
of anthracite and sand followed a fine screen (420 micron). Removals for
this study were 65 percent for suspended solids, 40 percent for BOD, and
60 percent for COD. The addition of a polyelectrolyete increased the
suspended solids removal to 94 percent and the BOD and COD removals to
65 percent each. The filtration design parameters for this referenced
study are presented in Table F-22.
-------
Table F-22 DESIGN PARAMETERS FOR FILTRATION MIXED
MEDIA, HIGH RATE
Filtering media 4 ft anthracite coal
J ft sand »612
Effective size, mm
Anthracite coal *
Sand 2
Flux rate, gpm/sq ft
Design 24
Range 8-40
Headless, ft 5-30
Backwash
Volume, \ of inflow 4
Air (rate and time) ,
scfm/sq ft, min 10, 10
Water (rate and time) ,
gpm/sq ft, min 60, 20
Filtering aid
Pol/electrolyte, type Anionic
Pretreatment 420 micron ultrafine
screen
Note: gpm X 0.679 1/sec/sq m
ft x 0.305 - m
scfm/sq ft x 0.305 - cu m/min/sq m
-------
76
Advantages of filtration include: a) good removal rates; b) the pro-
cess is easily automated; and c) relatively small land area is required.
Reported disadvantages include a) high capital costs; b) probable rapid
clogging resulting in higher operation and maintenance; and c) required
storage of backwash water which may be in the range of 4 percent of the
volume filtered. (36)
The envisioned use of filtration of separate storm water with respect
to this study would be as a secondary process such as effluent polishing
after coagulation and sedimentation. This high degree of treatment would
also have to be justified by strict water quality requirements or require-
ments of intended beneficial reuse. In this light, filtration would probably
be a desirable alternative.
The hypothetical costs of filtration facilities having capacities of 25,
50, 100, and 200 mgd, assuming 24 gpm per square foot, were developed by
Lager and Smith (36) and are presented in Table F-23. The estimated costs
of similar facilities, assuming 4 gpm. per square foot for a range of capaci-
ties from 0. 01 to 100 mgd, are presented in Figures F-2 and F-3. (62)
When the two sources are compared on the same ENR index, the capital
costs of the 25 and 50 mgd facilities are within 15 percent, and the capital
costs of the 100 mgd facilities are within 25 percent. However, the annual
operation and maintenance costs reported by Lager and Smith are about
7 to 10 times higher than those derived assuming 300 hours of operation
-------
77
TABLE F-23
COST Of HIGH KAT£ FILTRI\TIO^ (3(0
Plant capacity
cu m/sec
1.1
2.2
4.4
8.8
25
50
100
200
Capital
cost, $
1,580,000
2,390,000
4,370,000
7,430,000
Operation and
maintenance
cost, $/yr
44,000
55,000
98,000
129,000
The cost data are based on an ENR of 2000.
The operating costs are estimated to be $0.0382/1,000 1
($0.141/1,000_gal.) for 300 hours of operating per year
-------
78
1000
FILTRATION
(SAND OR GRADED MEDIA AT 4GPM/SQ.FT.)
IOOO
-
~
-
c
o
100 r-
-
Lt
2
. L-'U-HpLf. "J_U- E .1JL:;: -i
i - ;
rrhTT" :~""~JT~T~i'r\"j
0.1 I
DESIGN CAPACITY, MGD
FIGURE
PALLAS
- /343
-------
FILTRATION
(SAND OR GRADED MEDIA
AT 4.0 GPM/SQ.FT.)
1000
000
r^t'"t" ' "*~ -*~i "~i ~ir' "- 4 -^
^lllhrtjrftTTHin
^L__:_: 104
10
DESIGN CAPACITY, MGD
6 T B 9
JIO
!00
FI6URL F-3
;- {343
-------
80
per year at full capacity using Figure F-3. Since both sources are hypo-
thetical in nature, an actual full-scale facility would be required to give
better cost estimates than are available at this time.
Biological Treatment
In conventional biological treatment, the objective is to convert a
portion of the organic matter present in the sewage into cell tissue which
can be removed by sedimentation. A considerable amount of the colloidal
solids are also removed during this process. Biological treatment can be
accomplished in either of two ways: a) aerobically (in the presence of
oxygen); and b) anaerobically (in the absence of oxygen). Aerobic processes
are generally used to convert the organic matter into cells, while the
anaerobic processes are used to stabilize the cells removed in the aerobic
process.
The efficiency of biological treatment is dependent upon a number of
factors including: a) rate of substrate utilization; b) growth rate of the
organisms in the system; c)length of contact time between the waste and the
organisms; d) the types of organisms; and e) environmental conditions such
as temperature, pH, nutrients, and toxic materials. (36)
The aerobic removal of BOD and solids is accomplished by several
mechanisms including: a) removal of suspended matter by enmeshment
in the biological floe (cells); b) removal of colloidal material by physio-
chemical adsorption on the biological floe; and c) biosorption of soluble
organic matter by the microorganisms. (59)
-------
81
Biological treatment (i. e., by activated sludge or trickling filter
processes) of domestic and industrial wastewater produces a high quality
effluent and is generally the least costly process when compared to other
alternatives. However, stormwater flows are not continuous predictable
daily flows as are these other wastewater sources. Because of their
random, intermittent, and variable behavior, they are not conducive to
keeping the biological mass (necessary for assimilation of wastes) alive
during times of dry weather. (19) Also, such erratic loading conditions,
and the constitutents of some storm waters such as toxic materials, tend
to upset the biological process.
Two methods which have been tried to alleviate this problem are:
a) construction of a wet-weather facility next to the dry-weather treatment
plant; and b) use of a treatment process which can treat wastewater having
a relatively high variation in flow and strength.
An example of the first method is the contact stabilization process
used to treat combined sewer overflows at Kenosha, Wisconsin. The BOD
and suspended solids removals achieved at this plant were 83 and 92 per-
cent, respectively, for the 23 storm events during 1972. (36)
The second method was tested at New Providence, New Jersey. (37)
Although the community has separate sewer systems, high infiltration/
inflow conditions during wet periods raise the flow rate to as high as 10
times the average "dry-weather flow rate at the sewage treatment plant.
Modifications to the trickling filter plant were made so that during normal
How conditions the two filters would operate in series up to a predetermined
-------
82
flow rate. At this point, an automatic transfer to parallel operation is
accomplished until flows again drop within the series range.
The removals were reported to be 85 to 95 percent for both BOD and
suspended solids during dry-weather flows and 65 to 90 percent during wet-
weather flows. (36) It was also reported that removal efficiencies dropped
when the hydraulic loading increased in addition to being reduced by chang-
ing the operation to parallel with no recirculation. Both filters did recover
removal rates rapidly after the storms and a return to dry-weather flow
rates was accomplished. (37)
As was the case for other stormwater treatment alternatives, the
application of biological processes so far has been limited to combined
sewer overflows. The priority of concern for combined overflows over
separate stormwater runoff in the literature is apparently due to the fact
that the majority of the EPA demonstration projects have been in cities
where combined sewers comprise all or almost all of their system. Also
the characteristics of combined overflows are more similar to those of raw
sanitary sewage (see Table F-18), and thus the public health and human
reaction aspects of raw domestic sewage entering watercourses come into
play.
In many such instances, the combined system overflows are retained
in the lines and bypassed only at the treatment plant. Thus, the polluted
flows are conveyed to the site by one or several outfalls, whereas a
separate stormwater collection system may have hundreds of outfalls to
-------
83
receiving waters. The physical impracticality of the treatment of such
segmented flows will not be discussed further.
If the conventional treatment of separate storm water was well docu-
mented and proven very efficient in terms of physical pollutant removals,
such an alternative would be feasible only in specific or special case in-
stances such as water quality requirements of receiving bodies or benefi-
cial reuse requirements for domestic or industrial water supply. Even then
it may be more feasible to store the runoff and release it into the existing
sanitary sewer system during periods of low flow.
Waste Treatment Lagoons - Treatment lagoons have historically
been an important part of the waste treatment process, especially for small
municipalities and industries. They employ a biological treatment method
based on anaerobic and aerobic processes. However, they have been con-
sidered separately from other processes such as activated sludge and
trickling filters in this report. The primary reason for this is their simi-
larity to detention basins and/or retention ponds. All storage facilities have
one thing in common: they reduce the flow rate of a conveyance system such
as a drainage ditch or storm sewer. In doing so, the action of bacteria
and algae become significant because they are given sufficient time to
change the physical and chemical constituents of the influent prior to down-
stream release (if any). Thus, when designing a retention or detention
facility to control the rate of stormwater runoff and remove sediment, it
may be possible to also effect a degree of biological treatment with little
variation or added expense. The word "design" is the key word in this
-------
84
statement. Current design criteria are apparently not adequate to meet
higher quality effluent criteria that have recently been established across
the country. Apparently the main problem associated with lagoons is the
microbial solids content and suspended algae carried over in the effluent,
which exert oxygen demand and increase suspended solids concentrations.
Both of these factors have been excluded from consideration in the design
of conventional lagoon wastewater treatment systems, (60) resulting in un-
certain removal efficiencies for actual facilities.
Advantages of lagoons include: a) low capital costs (construction);
b) virtually unattended operation contributing to low operation and mainten-
ance costs; c) capability of being easily modified to act as a storage unit;
and d) ability to act as polishing lagoon during dry weather. (36) Dis-
advantages include a) large land requirements; b) uncertain degree of
treatment during actual operation; c) potential nuisance or safety hazards;
and d) sludge and sediment deposits reduce treatment capacity and, in the
case of retention/detention facilities, must be removed, adding to the
cost of operation and maintenance. (36)
The different types of lagoons are limited to: a) oxidation ponds,
b) aerated lagoons, c) anaerobic lagoons, and d) facultative lagoons.
Oxidation ponds are generally shallow earthen basins utilizing bac-
teria-algae symbiosis (existence of two organisms under mutual advantage)
and sedimentation as treatment. The depth is such that surface transfer
and algae are adequate to keep the pond aerobic.
-------
85
Aerated lagoons are generally lined or unlined earthen basins having
a mechanical aeration device to supply oxygen required by bacteria which
provide waste stabilization or treatment.
Anaerobic lagoons are devoid of oxygen and utilize methane bacteria
for stabilizing organic matter by converting it to carbon dioxide and methane
gas. They require relatively stable feeding rates or waste input to avoid
upsetting the delicate balance between acid-forming and methane-forming
bacteria, thus eliminating this process from further consideration in this
study.
Facultative lagoons contain three zones of biological activity: a)
aerobic near the surface; b) anaerobic near the bottom; and c) facultative in
the middle which contains both anaerobic and aerobic organisms.
Some mixing of the upper and lower layer is desirable to insure
distribution, and thus treatment, of pollutants in the individual layers.
Complete mixing is avoided to maintain treatment layers and prevent odors
from escaping from the anaerobic layer. This is usually accomplished by
making ponds deep enough to create a thermocline. (36)
Many factors apparently affect the operation and removal efficiencies
of lagoons. These include a) detention time; b) sufficiency of oxygen supply;
c) mixing of the pond by wind or mechanical means; d) organic loading rate;
and e) temperature. (36) The design factors for waste treatment lagoons as
compiled by Eckenfelder (59) are presented in Table F-24. The type of
lagoon utilized apparently is most closely associated with the depth and
-------
TABLE, r-24
Design factors for stabilization basins
Aerobic Facultative Anaerobic Aerated
Depth, ft 0.(>-1.0 2-5 S-10 15-13
Detention, days 2-0 7-30 30 50 2-10
HOD loading,
lh/(acre) (day) 100-200 20-50 300-500
Percent BOD removal SO-95 75-85 50-70 55-90
Aljiac concentration
mg/Iitcr >100 10-50 nil nil
-------
87
loading rate. According to Lager and Smith, (36) the removal efficiency is
dependent mostly on the detention time.
The design of a retention/detention facility is based upon a number
of factors, but primarily on volume of runoff desired to be contained. From
this amount, the depth, area, detention times, and other factors are deter-
mined. The topography and land availability also enter into the calcula-
tions. Thus, there will obviously be prior considerations to treatment, but
when the multi-purpose aspects of such facilities are included, some degree
of treatment should be easily incorporated into retention/detention
alternatives.
The estimated costs of aerated and non-aerated wastewater stabili-
zation ponds are indicated in Figures F-4 and F-5, respectively, for sur-
face areas between 1 and 1,000 acres. Because the higher sediment load
associated with stormwater runoff must be periodically removed, the costs
shown for operation and maintenance are probably lower than would be
experienced in actual stormwater treatment installations.
In the study for Columbia, Maryland, Mallory (52) presented a table
of land area versus capacity for open ponds whose primary objectives we ^e
local storage, treatment, and reuse of separate stormwater runoff. These
data are presented in Table F-25 and, although the depths are not reported,
they probably represent good "ball park" land requirements for desired
storage volumes. One factor that was reported with respect to the table
was that a 30-foot border was assumed beyond the high-water line to allow
-------
AERATED WASTE WATER STABILIZATION PONDS (£2)
ICO
M
k.
D
10
M
a
c:
a
B
o
8
u
cB
:
z:
O.I
-l-H:-|if:;--1-:j-rrH-:--!-.-(--;- ^ - ---rj~-jr" rrr.- -r±-±n>T
. . I ... j I J , t ''' t . ! I . ' ' ' ' ' ' ' ' '
: .n:i±.._:::L..L: : LJ
!OOO
o
XJ
o
H
a
J
00
O
_J
5
u
"
100
ipoo
POND SURFACE AREA-ACRES
FIGURE F-4
S ENR=
-------
NON-AERATED WASTEWATER STABILIZATION PONDS
100
Q
XJ
t/l
a
c
C
C
o
c
5
OC
c
Z
Z
10,000
1000 o
100
M
a
o
t/l
O
_
!00
' '000
POND SURFACE AREA - ACRES
FIGURE.
r=NR=
-------
TABLE. F-25
LAN]} AREA VS. CAPACITY - OPEN PONDS (52)
Capacity
(gallons)
10, 000
100, 000
1,000,000
4, 000, 000
10, 000, 000
20. 000, 000
40, 000, 000
100, 000, 000
Land Area
(acres)
0. 0714
0. 340
1. 690
4. 110
7. 645
12. 250
19. 550
36. 370
-------
91
for slope protection and permit decorative fringing with trees and shrub-
bery, desirable measures for any type of retention/detention facility.
Physical-Chemical Treatment
Physical-chemical treatment is a means of treatment in which the
removal of pollutants is brought about by chemical addition in conjunction
with physical treatment processes. Conventional physical-chemical
treatment with regard to wastewater generally includes preliminary treat-
ment, high-lime treatment (chemical clarification'*, ammonia 4iitrogen
removal (either by stripping or an on exchanger); neutralization (usually
with carbon dioxide), filtration, activated carbon polishing, and disinfec-
p-
-------
92
to shockloads and nonsusceptibility to biological upsets from toxic mater-
ials or washout during peak flow rates; and d) the resulting ability to pro-
duce consistently high effluents from the varying influents that characterize
stormwater runoff. (36) Because of the apparent lower concentrations of
nutrients and organic matter in storm water relative to raw municipal sew-
age, ammonia removal and activated carbon treatment would probably be
required only in specific instances. Therefore, the physical-chemical
treatment units assumed for this study are pretreatment (coarse screen-
ing), chemical coagulation, filtration, and disinfection. Since screening,
filtration, and disinfection are covered separately in the text, only chemi-
cal coagulation will be described in this subpart.
Chemical Coagulation - The key process in physical-chemical treat-
ment is the chemical coagulation-clarification unit, since it is responsible
for either directly removing pollutants or converting them into a form that
allows other units to effectively remove them. After preliminary treatment
by coarse screening (and grit removal if desired), the influent is dosed
with a coagulating chemical in a mixing unit. Common coagulants include
lime, iron or aluminum salts, polyelectrolytes, and combinations of the
three. Following chemical addition, the influent is allowed to flocculate
and settle in a conventional clarification facility having a mechanical
sludge-removal apparatus.
At this point, the reader may wonder what is the difference between
the process just described and sedimentation with chemical addition.
Chemical coagulation requires the physical process of settling and addition
-------
93
of chemicals to increase settling efficiency, both a part of physical-chem-
ical treatment. The only differences between the two processes in regard
to this study would be physical size, detention time, construction method,
anid sludge removal. Sedimentation in this context is envisioned as a pro-
cess used in connection with a larger lake or pond from which sediment
would be removed periodically (i. e., bi-weekly, monthly, or annually,
depending on physical characteristics) by means of conventional construc-
tion equipment. Chemical coagulation, on the other hand, would utilize a
relatively small unit constructed of steel or concrete having continuous
mechanical sludge or sediment removal and no multi-purpose benefits such
as aesthetics or recreation.
There is no method for predicting the exact dose of chemicals re-
quired for desired removal efficiencies; thus, the standard jar test proce-
dure must be utilized for this purpose. Even then, this procedure is only
approximate because of the apparent varying pollutant concentration of storrr
water both with time during event and time since the last event. The most
effective means of efficiently adding chemicals to obtain desired removal
rates in such a case may be to preset the dosing apparatus to add a higher
concentration at the beginning of the inflow event and gradually taper off
with time and/or volume of runoff. Obviously, a considerable amount of
research is needed in this area, especially when considering a fully auto-
mated process and the fact that such data for separate stormwater treat-
ment are nonexistent in the literature.
-------
94
Monitoring the pH of the resultant mixture could offer a mechanism
and a parameter for control of the addition of adequate chemicals. (36)
This procedure is necessary when phosphorus removal is achieved by high-
lime treatment (pH above 11.0) and removal of ammonia nitrogen by strip-
ping is utilized. (62)
The criteria that would be used to design the coagulation equipment
should also be determined by jar testing. These criteria include flash
mixing time, flocculation time, and sedimentation upflow rates, which
could vary considerably with the stormwater constituents. The removal
efficiencies of several chemical clarification pilot plants, as compiled by
Lager and Smith (36), are presented in Table F-26. Although these data
reflect the effect of physical-chemical treatment upon raw municipal sew-
age influent, they should reflect the applicability of such treatment upon
stormwater runoff.
The cost of lime clarification based on hypothetical treatment of
wastewater with the addition of about 350 mg/1 lime for facilities ranging
in size from 0.1 to 100 mgd is presented in Figure F-26. Because the
operation time and chemical quantities are unknown, the estimated costs
for treatment shown may not be valid for a stormwater installation.
Although filtration is discussed elsewhere in this report, Table F-27
is presented to show the effectiveness of the more specific case of filtration
following chemical coagulation in contrast to various other effluents. Such
-------
Table F-26 ACHIEVEMENTS OF CHEMICAL
CLARIFICATION [Sfr]
Plant
Blue Plains ,
Washington, D.C.
Ewing- Lawrence
Sewage Authority,
Trenton, N.J.
New Rochelle ,
N.Y.
Westgate, Va.
Salt Lake City,
Utah
Chemical
Lime pH 11.5
170 mg/1
ferric
chloride
Lime pH 11.5
125 mg/1
ferric
chloride
80-100 mg/1
ferric
chloride
BOD 5
removal ,
%
80
80
80
70
75
SS Phosphorus
removal, removal,
1 4
90 95
95 90
98 98
.-
80
-------
LIME CLARIFICATION
(TWO CLARIF1ER PROCESS)
.:!:. : ' "i J
Li:f:J_^-4i ..u_4___...V
, . i . , i j^
10,000
M
a
1000 "o
.o
at
T3
3
O
o
u
100
! 10
DESIGN CAPACITY, MGD
' ''100
a
FIGURL
F-Mf< =
-------
Table F-£7 EXAMPLES OF FILTER PERFORMANCE O/sf
Scale of
Location 1 ation
Stanford Pilot
Univers i ty
[25]
Lake Tahoe Full
191
Township
(20]
Bernards Pi lot
Township
120]
Township
[20]
Bernards Pilot
[20]
Washington, Pilot
D.C. [20]
BOP5. mg/1 COD, ns/1
Feed filter Inf. Eff. Inf. Eff.
Settled Dual-media --
secondary
e f fluent
Chemically Tri-media 9 5 23 IS
t reate J
secondary
effluent
T r i ck 1 inR
filter
effluent
Unsettled Moving bed 55 3.8
trickling
filter
effluent
effluent
Rjw Moving bed 115 19
Chemically Dual-media
clarif ied
raw
sewajte
Total
phosphorus. Turbidity,
ag/1 JTU" SS. »g/l
Inf. Eff. Inf. Eff. Inf. Eff.
0.6S 0.05 7.0 0.5 15 0
9.37 0.51 33 7 SO IS
19.1 0.99 39 3.4 86 7.1
14.6 1.3 S3 3.7 77 11
21.5 2.16 123 16.7 1S6 27
IS 4.5
a. Jackson turbidity units.
b. A single-medium filter operating essentially continuously and in a closed loop. Sec [20].
-------
98
removal efficiencies should also be applicable to effluent from sedimenta-
tion, providing other constituents such as algae are not present in dominat-
ing concentrations.
Disinfection
Communicable diseases have been with man throughout history. Epi-
demics such as the plagues that swept Europe in the fourteenth century,
the London epidemic in the seventeenth century, and more recently the
cholera, typhoid, and other epidemics that swept this country in the nine-
teenth century are general knowledge to the public. However, it was not
until 1854 that water was realized as a source of infection, with the famed
Broad Street Pump incident when John Snow and John York demonstrated
that the water from the pump was the cause of a local cholera epidemic
in London.
The practice of chlorination has become such a widespread and
accepted method of preventing the spread of waterborne diseases that it
is frequently taken for granted. Although chlorination of water supplies
on a regular basis has been practiced since about 1850, continuous
chlorination of water supplies did not begin in this country until the early
1900's. In 1909, Jersey City, New Jersey started hypochlorite treatment
of its Boonton supply, leading to a celebrated court case which upheld
the right of the city to chlorinate the water in the best interest of the public.
The development of facilities to feed gaseous chlorine into water occurred
about 1912, and after that time the chlorination process grew rapidly. (63)
-------
99
Chlorination of water supplies and sewage effluents grew out of the
concern for waterborne organisms in sewage, although today this is recog-
nized as only one source. From the summary on constituents in storm
water, it is obvious that a considerable amount of such pollution is associ-
ated with urban runoff. Even naturally "pure" surface runoff from wilder-
ness areas will contain background concentrations of organisms originating
from the air, soil, or human or animal activities on the watershed. (69)
"The three categories of human enteric organisms of the greatest
consequence in producing disease are bacteria, viruses, and amoebic
cysts. "(36) Chlorination is essentially 100 percent effective in destroying
the higher organisms. However, viruses, cysts, and bacterial spores can
be tolerant of most Chlorination procedures. Since there are more than 100
viruses excreted in human feces that are capable of causing a waterborne
disease, the significance of improper or inadequate Chlorination is real-
ized. (64) Thus, if any use such as contact recreation or water supply is
planned for such contaminated stormwater runoff or waters receiving such
runoff, disinfection may be an important process to consider in stormwater
management. Any alternative plan which calls for treatment will most
probably also include disinfection, due to the special use or water quality
problem which calls for treatment in the first place. However, the wide-
spread use of disinfection on rural or semi-urban or suburban runoff enter-
ing natural streams or lakes will probably not be justified nor desirable
because of the resulting removal or destruction of natural organisms
necessary to the total food chain.
-------
100
The effectiveness of disinfection depends upon a number of factors
including: a) contact time, b) concentration and type of chemical agent,
c) temperature, d) pH, and e) number and types of organisms. Only chem-
ical agents will be considered applicable to stormwater disinfection. Other
means, such as radiation and heat, are not considered feasible. There are
also disinfection properties associated with the physical removal of organ-
isms, as in solids separation and biological treatment. However, these
removals will be considered only secondary since disinfection is not their
primary purpose.
The characteristics of the most common chemical disinfectant agents
are presented in Table F-28. When the characteristics of stability, effec-
tiveness, cost, and technology are considered, it is believed that conven-
tional chlorine feed systems or a form of hypochlorite feed would be more
desirable than the other disinfectants. For the purpose of this study, disin-
fection will be assumed to consist of conventional gaseous chlorine feed
facilities commonly used in water and wastewater treatment.
Weibel (61) performed chlorination tests on separate urban storm-
water runoff in addition to the sedimentation tests mentioned previously.
Varying doses of chlorine (form not reported) were applied to raw and
settled stormwater runoff to determine their effects on total and fecal
coliforms and fecal streptococci. At chlorine doses of 4. 62 mg/1 and
higher, substantial kills were observed. Better than 99. 999 percent total
and fecal coliforms and 99. 99 percent fecal streptococci were killed. At a
dose of 4. 65 mg/1, Weibel reported a free residual of 0. 0 mg/1. Doses of
-------
101
Table F-28 COMPARISON OF IDEAL AND ACTUAL CHEMICAL
DISINFECTANT CHARACTERISTICS
Sodium Calcium Chlorine
Ideal disinfectant Chlorine hypochlorite hypochlorita dioxide
Toxicity to Should l>e hishly toxic at High High High High High
microorganism high dilutions
Solubility Must be soluble in water or Slight High High High Hijh
cell tissue
Stability Loss of germicidal action on Stable Slightly Relatively Unstable, must Unstable, mujt
standing should be low unstable stable be generated be generated
as used as used
Nontoxic to Should he toxic to micro- Highly toxic Toxic Toxic Toxic Toxic
higher forms organisms and nontoxic to man to higher
of life and other animals life forms
Homogeneity Solution must be uniform in Homogeneous Homogeneous Homogeneous Homogeneous Homogeneous
compos it ion
Interaction Should not be absorbed by Oxidizes Active Active High Oxidizes
with extraneous organic matter other than organic oxidizer oxidizer organic matter
material bacterial cells matter
Toxicity at Should be effective in ' High High High High Very high
ambient ambient temperature range
temperatures
Penetration Should have the capacity to High High High Hlsh . High
penetrate through surfaces
Noncorrosive Should not disfigure metals Highly Corrosive Corrosive Highly Highly
and nonstaining or stain clothing corrosive corrosive corrosive
Deodorizing Should deodorize while High Moderate Moderate High High
ability disinfecting
Detergent Should have cleansing action
capacity to improve effectiveness of
disinfectant
Availability Should be available in Urge Low cost Moderately Moderately Moderate »i£n c°st
quantities and reasonably low cost low cost cost
priced
-------
102
5.54 and 11.08 mg/1 reportedly gave free residual chlorine concentrations
of 0.06 and 2.4 mg/1, respectively. This is significant when considering
the reduction of enteric viruses. According to Sobsey (65), a free chlorine
residual of 0. 3-0. 5 mg/1 after 30 minutes contact time is likely to produce
99. 99 percent reduction in enteric virus concentration if the water has a
pH * 8.5.
The costs of conventional gaseous chlorination facilities can be esti-
mated from Figures F-7 and F-8. As with other such figures in this re-
port, the operation and maintenance cost of such facilities for stormwater
treatment is questionable.
-------
CHLORINE CONTACT BASINS (62)
CAPITAL-:: :-
":i]:i]z:2±
j;i
: ! . , . . , f . i T . I . i .
""-
..,
FT."*"; ' . ' ! ! : '
:;::'L.U_i:!.
.:_:>.
: ;?-;; : |-t>T
--U-^vL^f--.
.i>i'x':i:'i.:
. I::
. ...-,,., :...,. :
i i -
-
, . , I
:j:-::i . ;:j.J [.!. ! , :::;'-;: i. :::.;:i:'!: .:-i-'j : , /]}
:.r-r:i!n-l:i':h;;:v;^i.='Tn
! i-1
|!j '
i
1000
100
^
.
;
:
10 100
BASIN VOLUME- 1000 CU. FT.
" looo
FIGURE F-7
-------
CHLORINATIOH FEED SYSTEMS
kOOOf-
10,000
o
-c
100
in
a
I
3
a
O
CJ
2
CD
c
100
AVERAGE CHLORINE'USE AT DESIGN FLOW- LBS.PER DAY
10
10,000
FIGURE
-------
105
SECTION V
SUMMARY OF ALTERNATIVES
The purpose of this section is to present the alternatives discussed
in the previous sections with a summary of their relative effectiveness in
pollution control or removal. In order to accomplish this without repeat-
ing some of the test and tables, a summary tabulation was prepared and is
presented as Table F-29. The first column lists the alternatives by the
three general topics of abatement, control, and treatment. The remaining
six columns are entitled 03 Reduction, SS Reduction, Pathogen Reduction,
Nutrient Reduction, Heavy Metal Reduction, and Flotage Reduction. With-
in each of these six pollutant columns, there are sub-columns represent-
ing a range of degrees of potential reduction by each alternative. The
degree in which an alternative is effective in reducing a pollutant is indi-
cated by an "X" in the proper single sub-column for each of the six pollu-
tant columns. Thus, an alternative may be quickly evaluated as to its
probable effectiveness in reducing a chosen pollutant by scanning the proper
vertical column. Similarly, the alternative or alternatives which have
the potential for the highest pollutant removal may also be determined.
The ranges of pollutant removal efficiencies (expressed as percent
removal) shown in Table F-29 were derived by the engineers from the
literature. Because of the variability of similar values reported in the
literature, the ranges should not be taken as absolute, since more specific
data could very well alter them.
-------
TABLE F-29 106
EFFECTIVENESS OF ALTERNATIVES IN
POLLUTANT REDUCTION OR REMOVAL
Alternative Techniques
and Strategies
Considered
ABATEMENT
Land Use Planning
Improved Sanitation
Improved Solid Waste Practices
Conventional Street Sweeping
Extensive Street Sweeping
Enforced Controls
CONTROL
Retention/Detention
Subsurface Detention
Infiltration Systems
Collection System Controls
Vegetative Cover
Sediment Control
TREATMENT
Physical Treatment
Sedimentation with Chemicals
Sedimentation without Chemicals
Bar pr Coarse Screen
Dissolved Air Flotation
Filtration
Biological Treatment
Lagoons
Physical-Chemical Treatment
Chemical Clarification
Disinfection
c
go
1 = 5s s? g
s &s LO o 9
Q o CN in m
« ^ 0 li §
O o T- cs o
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
c
o
*-*
° *?
~a ^ o o
« in in m
^ fe
co ' in >
00 O CM O
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Pathogen Reduction '
Negligible
up to 99%
over 99%
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Nutrient Reduction
0 - 25%
25 - 75%
over 75%
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Flotage Reduction
0 - 30%
30 - 80%
over 80%
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Heavy Metals Reduction
0 - 50%
50 - 90%
over 90%
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
-------
107
BIBLIOGRAPHY
NCC 208 Structural and Non-structural Techniques Summary
(34) Hittman Associates, Inc., Approaches to Stormwater Manage-
ment, U, S. Environmental Protection Agency, Office of
Water Resources Research, OWRR C-4140, (November 1973),
NTIS PB-228-124.
(35) Poertner, Herbert G., Practices in Detention of Urban Storm-
water Runoff, U. S. Environmental Protection Agency, Office
of Water Resources Research, OWRR C-3380, (June 1974),
NTIS PB 234 554.
(36) Lager, John A., and Smith, William G., Urban Stormwater
Management and Technology, An Assessment, Metcalf and
Eddy, Inc., U. S. Environmental Protection Agency, National
Environmental Research Center, Office of Research and
Development, (December 1974), NTIS PB-240 687.
(37) Lager, John A., "Stormwater Treatment: Four Case
Histories," Civil Engineering - ASCE, (December 1974).
(38) Shubinski, Robert P., "Concepts of Urban Runoff Control,"
Management of Urban Storm Runoff, American Society of
Civil Engineers, OWRR C-4048, (May 1974), NTIS PB-234 316.
(39) Alan M. Voorhees and Associates, Inc., Water Resources
Engineers and Environments for Tomorrow, Land Use and
Water Quality Protection; Relationship, Strategies, and
Guidelines, a draft report prepared for the U. S. Environmental
Protection Agency (January 1973).
(40) Black, Crow, and Eidsness, Inc. and Jordan, Jones, and
Goulding, Inc., Study and Assessment of the Capabilities and
Cost of Technology for Control of Pollutant Discharges from
Urban Runoff, a draft report prepared for the National
Commission on Water Quality, (July 1975).
(41) Tourbier, J., and Westmacott, R., Water Resources Pro-
tection Measures in Land Development - A Handbook,
Delaware University, Neward, Water Resources Center,
(April 1974), NTIS PB-236 049.
(42) Orlandella, A.R., "Burlington Counts on Salt Again,"
Public Works, Vol. 105, No. 8, (August 1974).
-------
108
(43) Weaver, Robert J., Recharge Basins for Disposal of Highway
Storm Drainage - Theory, Design Procedure, and Recom-
mended Engineering Practices, New York State Department
of Transportation, (May 1971), NTIS PB-2Q1 959.
(44) Thelen, E., Grover, W. C., Hoiberg, A. S., and Haigh, T. I.,
Investigation of Porous Pavements for Urban Runoff Control,
the Franklin Institute Research Laboratories, Philadelphia,
Pennsylvania, U. S. Environmental Protection Agency,
EPA 11034 BUY, (March 1972).
(45) Heaney, James P. and Sullivan, Richard H., "Source Control
of Urban Water Pollution," Journal Water Pollution Control
Federation, Vol. 43, No. 4 (1971).
(46) Engineering Science, Inc., Comparative Costs of Erosion and
Sediment Control, Erosion Activities, EPA-430/9-73-Q16,
(July 1973). ~~~~
(47) Popkin, B. P., Effect of Mixed-Grass and Native-Soil Filter
on Urban Runoff Quality, Masters Thesis, Arizona University,
Tucson, (1973), NTIS PB 237 683.
(48) Boysen, S. M., "Engineering Practices for Sediment Control
in Urban Areas of Maryland, " Proceedings - Planning and
Design for Urban Runoff and Sediment Management, University
of Kentucky, Lexington, (July 1973), NTIS PB-225 274.
(49) Soil and Water Conservation for Urbanizing Areas in Delaware,
U. S. Department of Agriculture, Soil Conservation Service,
(September 1973.
(50) Hittman Associates, Inc., Guidelines for Erosion and Sediment
Control Planning and Implementation, U. S. Environmental
Protection Agency, Office of Research and Monitoring,
EPA-R2-72-015, (August 1972).
(51) Everhart, Ralph C., "New Town Planned Around Environmental
Aspects, " Civil Engineering - ASCE, 43, No. 9, (September,
1973).
(52) Mallory, S. W., The Beneficial Use of Storm Water, U.S.
Environmental Protection Agency, Office of Research and
Monitoring, EPA-RZ-73-139, (January, 1973).
-------
109
(53) Design and Construction of Sanitary and Storm Sewers, WPCF
Manual of Practice No. 9, ASCE Manual of Engineering Practice
No. 37 (1967).
(54) Weddle, C. L., and Madri, H. N., "Reuse of Municipal Waste-
water by Industry, " Industrial Water Engineering, Vol. 9, No. 4,
(June/July 1972).
(55) Metzler, D. L., et al, "Emergency Use of Reclaimed Water
for Potable Supply at Chanute, Kansas, " Journal American Water
Works Association, Vol. 50, No. 8, (August, 1958).
(56) Berger, Bernard B., "Public Health Aspects of Water Reuse for
Potable Supply, " Journal American Water Works Association,
Vol. 52, No. 5, (May, 1960).
(57) Craft, T. F., "Review of Rapid Sand Filtration Theory, "
American Water Works Association Journal, Vol. 58, No. 4,
(April, 1966).
(58) O'Melia, Charles R., and Stumm, Werner, "Theory of Water
Filtration," American Water Works Association Journal,
Vol. 59, No. 11, (November, 1967).
(59) Eckenfelder, W. Wesley, Jr., Industrial Water Pollution
Control, McGraw-Hill Book Company, New York, (1966).
(60) Waste Treatment Lagoons - State of the Art, Environmental
Protection Agency, Project #17090 EHX, (July, 1971).
(61) Weibel, S. R., Weidner, R. B., Christiansen, A. G., and
Anderson, R. J., "Characterization, Treatment, and Disposal
of Urban Storm water, " Section 1, Paper No. 15, Third Interna-
tional Conference on Water Pollution Research, Munich,
Germany, (1966).
(62) Turner, Collie & Braden, Inc., Wastewater Management Plan
Colorado River and Tributaries, Texas, prepared for U.S.
Army Corps of Engineers, Fort Worth District, Vol 3 Technical
Appendix, (September, 1973).
(63) Sawyer, Clair N., and McCarty, Perry L., Chemistry for
Sanitary Engineers, McGraw-Hill Book Company, New York,
(1967).
-------
110
(64) White, George Clifford, "Disinfection: The Last Line of Defense
for Potable Water," American Water Works Association Journal
Vol. 67, No. 8, (August, 1975).
(65) Sobsey, Mark D., "Enteric Viruses and Drinking-Water
Supplies, "American Water Works Association Journal, Vol. 67,
No. 8, (August, 1975).
(66) Engineering News-Record, McGraw- Hill, Inc., New York,
(March 20, 1975).
(67) Ehlers, Victor M., and Steel, Ernest W., Municipal and Rural
Sanitation, Sixth Edition, McGraw-Hill Book Company, New
York (1965).
(68) Yorke, Thomas H., "Effects of Sediment Control on Sediment
Transport in the Northwest Branch Anacostia River Basin,
Montogomery County, Maryland, " Journal Research U. S.
Geological Survey, Vol. 3, No. 4, (July - August 1975).
(69) Coltharp, George B., and Darling, Leslie A., "Livestock
Grazing - A Non-Point Source of Water Pollution in Rural
Areas?" Water Pollution Control in Low Density Areas,
Proceedings of a Rural Environmental Engineering Conference,
Paper No. 23, Edited by William J. Jewell and Rita Swan, The
University Press of New England, Hanover, New Hampshire
(1975).
-------
G. Evaluation and Screening of Alternative Techniques for Stormwater
Management.
This section of the report presents a methodology for evaluating the
various stormwater management alternatives presented in Section P. It
should be noted that such a procedure must be very general in nature due to
the broad range of problems and available solutions which it considers. The
first item which must be identified is the objective (or objectives) which re-
sult in the consideration of alternatives in the first place. The primary
objective in the 208 program, of course, concerns water quality as related
to point and nonpoint sources of pollution. However, there are a number of
i
other secondary objectives which can be closely related to water quality and
may be called the "three r's" of secondary wastewater management: rec-
reation, recharge, and reuse. These objectives are considered secondary
only when compared to water quality goals. In many instances, it may be
possible to effect these secondary objectives in accomplishing the primary
objective, thereby increasing the benefits of an alternative, and thus its
feasibility or acceptance.
In order to realistically evaluate a stormwater alternative, it must
be evaluated in response to a. problem resulting from either quality (i. e.,
water pollution) or quantity (i. e., flooding) or both. Such problems are
identified directly by such means as water quality sampling and analysis,
or obvious physical evidence such as erosion, sedimentation, suspended
materials, and odors. Potential problems may be disclosed by inputting
generalized data and assumptions into a computer model which is designed
-------
to indicate degradation of water quality as a result of wastewater inflows.
Due to the limited scope of this study and the fact that very limited quality
data are available for Delaware streams, hypothetical problems will have
to be considered in evaluating the alternatives presented in Section F.
Many alternatives were screened "out" while compiling the methods and
techniques presented in the previous section because of the desire to keep
those alternatives considered applicable to separate storm water and in
the form of more general categories of abatement, control, and treatment.
Examples of this would be the exclusion of alternatives which concern
only combined sewers such as sewer separation, or the exclusion of such
specific processes, procedures, and methods to control pollution resulting
from the production of timber, which is negligible in New Castle County.
The many different types of abatement and control measures commonly
used by the Soil Conservation Service were also excluded from detailed
evaluation. These measures include: different types of vegetative and
non-vegetative or chemical mulching; vegetative ground covers such as
vines, shrubs, and trees; methods to stabilize sand dunes along the coast;
and the many structures such as grading, outfalls, chutes, and level
spreaders.
Once the basic information has been compiled and goals and objec-
tives are outlined with respect to the problems of the study area, the feasi-
bility of implementing a program of specific corrective actions may be
determined. This feasibility will be dependent upon a number of related
-------
and unrelated factors ranging from technical efficacy and economic justifi-
cation to administrative, legal, and political amenability. These factors
were arranged into ten categories which cover the broad range of possible
advantages, disadvantages, benefits, and limitations of individual
alternatives.
A detailed and extensive procedure is impossible due to the limits of
j the available data and state-of-the art of stormwater management. There-
fore, a more direct, simplified matrix approach was derived from several
similar attempts in the literature, and is presented in Figure G-l.
Since it was desired to rank the alternatives with respect to each
other in their relative effectiveness or applicability to each category, a
| numerical value was assigned each alternative for all ten categories.
Values range from 0 to 10, indicating minimal to maximal degree of effec-
tiveness or applicability. The values presented in Figure G-l were deter-
mined by the Engineers, based upon the conclusions of practitioners and
researchers presented in the literature. It should be noted that the values
and ranking procedure may vary with individuals, specific land-use char-
acteristics, or political and public attitudes.
If all ten values for an alternative are horizontally summed (total 100
possible), the total should reflect the overall feasibility of the alternative in
relation to general problems of stormwater management. Similarly, if it is
desired to know which alternative or alternatives are probably most effec-
tive with respect to a particular category, the column of numbers below a
-------
4
category are scanned, with the higher numbers representing the more
feasible alternatives.
A column is also presented that indicates the land-use category
(either urban or rural) for which the alternative will probably be best
suited. Some alternatives, such as sediment control, are equally effective
for all land-use types and are so indicated in Figure G-l.
The ten evaluation categories appearing in Figure G-l are listed
below, along with a brief description of the factors which they represent:
1. QZ Demand Reduction - The effectiveness of an alternative in re-
ducing the availability or removing those materials which exert an
oxygen demand upon receiving waters is evaluated under this
category.
2. SS Reduction - The effectiveness of an alternative in reducing the
availability or removing those materials which may be suspended,
floated, or transported and deposited is evaluated under this
category.
3. Nutrients, Heavy Metals, and Toxic Compounds Reduction - This
category includes the nitrogen and phosphorus compounds, the heavy
metals such as lead, mercury, cadmium, chromium, and zinc com-
monly referred to as toxic materials, as well as the pesticides and
herbicides. These contaminants are grouped together into one cate-
gory because they are normally associated with the fine suspended
solids and sediments, and any alternative which affects one will in all
likelihood have an equal effect upon the others.
-------
TABLE G-1
STORM WATER MANAGEMENT ALTERNATIVES SUMMARY
MATRIX
Alternative Techniques
and Strategies
Considered
ABATEMENT
Land Use Planning & Implementation
Improved Sanitation
Improved Solid Waste Practices
Conventional Street Sweeping
Extensive Street Sweeping
Enforced Controls
CONTROL
Surface Detention
Surface Retention
Subsurface Detention
Infiltration Systems
Collection System Controls
Vegetative Cover
Sediment Control
TREATMENT
Physical Treatment
Sedimentation with Chemicals
Sedimentation without Chemicals
Bar or Coarse Screen
Dissolved Air Flotation
Filtration
Biological Treatment
Lagoons
Physical-Chemical Treatment
Chemical Clarification
Disinfection
Land Us* Applicability
Urban
Rural
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
EVALUATION CATEGORIES
<1>
O2 Demand Reduction
3
2
S
6
5
4
6
6
8
1
9
7
7
5
1
7
5
6
7
0
<2l
SS Reduction
3
0
S
6
5
4
6
6
10
1
9
9
8
6
1
7
9
7
8
0
(3)
Nutrients, Heavy Metals,
and Toxics Reduction
3
1
S
6
7
2
6
6
7
1
9
6
6
4
0
S
7
6
7
O
(4)
Pathogen Reduction
0
1
2
2
3
0
4
4
9
0
7
0
4
3
0
3
8
4
4
10
(5)
Applicability to
Storm Flows
S
9
6
5
9
10
8
8
7
2
10
8
4
5
8
4
4
5
4
10
(6)
Environmental Impact
10
5
5
5
8
4
7
8
9
1
10
8
6
5
2
6
6
4
6
9
(7)
Public and Political
Acceptance
5
8
5
3
2
8
6
7
7
0
10
5
6
6
5
3
5
4
6
8
(8)
Secondary Benefits or
Dual-Use Capabilities
8
1
t
1
5
9
7
2
9
1
10
6
8
7
0
8
8
S
8
0
(91
Capital Cost
10
7
7
6
9
8
8
4
6
2
9
7
3
3
7
3
2
7
4
7
not
Operation & Maintenance
9
2
4
2
5
8
7
3
8
0
10
6
2
3
6
2
2
6
2
3
Total Effectiveness or
Feasibility of Alternative
56
36
45
42
58
57
65
54
80
9
93
62
54
47
30
48
56
60
56
47
Typical Components
Zoning: Flood Plain and Shoreline Use
Management; Building Codes and Sub-
division Regulations.
Mechanical Sweepers
Vacuum Sweepers with or without
Mechanical Sweepers
Air pollution standards; restrictive use
of pesticides, fertilizers, deicing salts,
etc.; animal control; debris on vacant
lots; unauthorized dumping.
Roof-top storage; parking lot storage;
storage on plaza areas; dry impound-
ments; channel and swale storage.
Permanent impoundments.
Storage tanks.
Infiltration wells, basins, pits, and
trenches; porous pavement.
Periodic sewer flushing and cleaning;
catch basin cleaning; infiltration/ inflow
control.
Control of construction-related erosion
by vegetative or structural methods as
used by soil conservation service.
Conventional clarification units with
alum addition, flocculaiion.
With polyelectrolytes or ferric chloride
Lime addition, flocculation,
sedimentation.
Chlorination.
-------
4. Pathogen Reduction - Most of the literature concerns only the coli-
form organisms with respect to public health aspects of stormwater
runoff. However, because these organisms do not indicate the pre-
sence of enteric viruses which are of equal concern, this category
considers the effect an alternative has upon reducing both bacterial
and viral forms of disease causing agents.
5. Applicability Under Variable Water Flow Conditions - Because of the
varying quantity and sometimes discontinuous nature of stormwater
runoff, some alternatives may be less effective in pollutant removal
or prevention of pollutant entry than if the processes were more
stable or constant. The best example is the limitations which such
characteristics can have upon some biological treatment alterna-
tives, since they are easily upset by large variations in flow rate
or concentration of certain pollutants.
6. Environmental Impact - This category probably includes the widest
range of possible considerations, both good and bad. Impacts to
wildlife, fish, and vegetation and to the human environment, including
aesthetic effects, are under consideration in this category. An alter-
native such as sediment reduction could enhance the biota and wild-
life of a stream, while disinfection would produce exactly the opposite
results. However, if the stream is used for contact recreation or
water supply, failure to disinfect could allow conditions adverse to
public health to develop or continue.
-------
7. Public and Political Acceptance - The ease in which an alternative
may be implemented by a governing body or the reaction it may
draw from the general public could be a dominant factor in its
consideration. One such example would be the intensification of
street-sweeping operations. In order to properly effect such a pro-
gram, the vehicles must sweep materials from the area near the
curb which would necessitate "no parking" restrictions during sweep-
ing periods. The inconvenience to the public as a result of decreas-
ing available parking area for a longer period of time could result in
the eventual abolition of such a program.
8. Secondary Objectives or Dual-use Capabilities - This category in-
cludes all secondary benefits which may be realized from implemen-
tation of an alternative; i.e., recharge, recreation, and reuse. A
common example would be a retention or detention facility having as
its primary objective flow-rate reduction and sediment removal, but
simultaneously providing recreation, enhancing aesthetics, and
allowing infiltration, and thus aquifer recharge.
9. Capital Cost - This category may be considered by many to be among
the most important, for no matter how effective an alternative may
be in its primary objective, if it cannot be financed, it cannot be
implemented. Also, if there are two or more alternatives which
may accomplish a desired objective with equal effectiveness, the one
which costs less will probably be the one given further consideration.
-------
10. Cost of Operations and Maintenance - This is of equal importance as
capital costs, for even though an alternative may cost less than
another to construct, if it costs more to operate and maintain, over
a given period of time it could eventually cost more.
A summary evaluation of each alternatives is presented below in des-
cending order of their numerical ranking total determined in Figure G-l.
The highest ranking alternatives are described in greater detail than others
due to their higher relative importance and potential use in stormwater
management in New Castle County, Delaware.
Ranking Total From
Figure G-l. Alternative Summary
93 Vegetative Cover - This alternative is the most
versatile of all the techniques in that it can be
used as either an abatement, control, or treatment
measure with equally high effectiveness. As an
abatement measure, the maintenance of a good
vegetative cover will provide maximum erosion
control and prevention, thus reducing the possi-
bility of sediment being dislodged and transported.
In preventing sediment transport, the associated
oxygen-demanding materials and heavy metals,
nutrients, herbicides, and pesticides are also
prevented from entering a waterway. A good
vegetative cover can be used to slow the velocity
of runoff and thus aid in its detention. It can also
act as a filter or screen to remove particles from
suspension. There are also treatment properties
associated with vegetation as related to spray
irrigation and overland runoff (more commonly
used as a method of tertiary wastewater
treatment). Vegetation is also a necessary
component of swales, retention/detention ponds,
-------
sediment control basins, and infiltration basins to
keep them operational. Other secondary benefits
include the aesthetics of vegetation, especially in
connection with the blue-green concept of develop-
ment, its relative ease of implementation, and the
relatively low cost of implementation and mainten-
ance when compared to other alternatives.
80 Infiltration Systems - Where adequate soil condi-
tions exist, these alternatives are potentially
excellent for reducing pollution and providing
secondary benefits of aquifer recharge and storm
water runoff volume reduction. Use of the subsur-
face soil removes essentially all contaminants
associated with solids, and most of the remaining
contaminants are assimilated by soil bacteria.
Conservative substances such as nitrates and
chlorides may not be significantly removed how-
ever, and their reduction is dependent upon dilu-
tion by groundwater, or surface water should the
groundwater enter a stream or lake. Although
these alternatives rank the second highest of those
considered herein, their possible limitations
should also be noted. Because of the relative
slow infiltration rate of most suitable soils com-
pared to runoff rates, some means of storing the
runoff prior to infiltration will probably be
necessary. Since porous pavement is generally
designed to contain only the rainfall striking the
pavement, adequate retention volume can usually
be provided in the subgrade aggregate. However,
the other means of infiltration are generally re-
quired to dispose of the runoff from a rooftop or
other impervious area such as a parking lot.
Infiltration pits and trenches will generally have
a relatively large storage volume (and thus surface
area) compared to the amount of drainage area
they must receive runoff from. Infiltration basins
are more "efficient" in that they may contain a
relatively high storage volume as compared to the
other infiltration methods. By their nature and
methods of operation, however, infiltration sys-
tems are limited to localized, offstream, and
relatively small-scale installations. Thus, a few
such small isolated systems in a drainage area
-------
would probably not have any overall significance.
An intensive program requiring all roof drains
and large public and private impervious areas
to utilize such systems, however, could have a
tremendously beneficial effect upon a watershed.
65 Surface Detention - Surface detention refers to
permanent impoundments having added capacity for
stormwater flow rate control, and thus flood re-
duction downstream. They are capable of provid-
ing a degree of biological treatment similar to
lagoons and sedimentation, but have the added
benefits of aesthetics when combined with
landscaping. They must be properly maintained,
however, which consists mostly of periodic sedi-
ment removal. One disadvantage these facilities
have is their hazard to small children who will
be attracted to the water. A more familiar dis-
advantage is the relatively high land requirement
as compared to other alternatives. Although
cheaper to construct and maintain, their feasibility
could be greatly reduced in certain areas where
land is either not available or too valuable.
Therefore, actual applications of this alternative
may be limited to semi-urban, developing urban,
or rural areas.
62 Sediment Control - Although erosion and sediment
control is accomplished by the use of other control
alternatives such as retention/detention ponds or
basins and vegetation, the combination of such
components to specifically control sediment origi-
nating from construction activities is worthy of
individual consideration. The need to control ero-
sion in this country led to the creation of the Soil
Conservation Service whose sole purpose is the
conservation of soil and water and the prevention
of these resources becoming "out of place. "
Erosion is not only the source of sediment but
can damage or destroy public structures such as
highways and bridges, leading to further problems
or hazards. It is also aesthetically unpleasing
and gives an appearance of irreparable damage
and devastation to the landscape or a stream.
The resulting sediment carries oxygen-demanding
-------
10
materials, suspended solids, toxic substances,
and such substances as nutrients, pesticides,
and herbicides, usually traceable to a man-made
origin. Sediment can clog drainage ways and
structures increasing the potential for flood
damage and degrade the chemical quality of the
receiving stream both directly and indirectly.
Thus, the importance of controlling erosion and
sediment is realized in a number of ways.
60 Lagoons - Lagoons have the primary function of
providing biological treatment to wastewater. They
differ from detention ponds herein only by not
producing the numerous other secondary benefits.
They would probably be used in more rural areas
for the stabilization of animal wastes or other such
specific sources of pollutants, and it would there-
fore not be desirable to provide aesthetics and
recreational facilities with them. In other areas
where treatment of storm water is desired, the
surface detention impoundment would probably be
used, since the concentrations of pollutants in the
runoff would be lower and less likely to cause the
odor problems associated with lagoons.
58 Enforced Controls - The prohibition or restriction
in the potential availability of pollutants to runoff
can be of greater importance than indicated by this
matrix evaluation procedure. Although the over-
all quantity reduction of most pollutants is not as
significant when compared to other alternatives,
if the materials are prevented from entering the
runoff in the first place, they need not be con-
sidered further. The concern for toxic substances
is a good example. These compounds found in all
pesticides, herbicides, and other substances
applied to the ground surface can have highly de-
trimental effects, even in trace concentrations.
However, ignorance or carelessness in their ap-
plication or frequency of use by the general public,
in addition to governmental agencies, can result
in unnecessary pollution of surface and ground-
waters. However, it should be recognized that no
matter how good the intentions of a government or
-------
11
the general public in passing and supporting such
legislation, the actual success and respect for
such controls may decline in popularity due to
apathy by inconvenience to the public.
57 Surface Retention - These facilities are generally
constructed for the purpose of flood reduction by
temporarily storing a portion of the runoff.
Because of the relatively short detention times
which are associated with these facilities, essen-
tially no biological activity and only partial sedi-
mentation is possible. However, in reducing the
peak flow rates of runoff, possible erosion haz-
ards are reduced and indirect pollution abatement
can be realized. They also have the secondary
benefits of recreation areas when dry. They can
require a substantial area of land, however, but
generally such land is in a flood plain and not suit-
able for development anyway.
56 Filtration - This alternative has a relatively high
ranking due to its potential pollutant removal
capabilities. Since a considerable portion of the
contaminants can be associated with the solid par-
ticles which this process removes, a high degree
of treatment is generally associated with filtration.
Filtration is also not affected by toxic substances
as are biological treatment processes, and the
effects of flow variation can be negated in the de-
sign stage. Further, this process can be fully
automated, is not affected by periods of non-use,
and requires no start-up time or readjustment
time after peak flows. The major disadvantages
are high capital and operational costs, as well
as the requirement for a very high quality effluent
which normally is associated with water quality
problems or reuse. It will also have to be pre-
ceeded in most cases by screening and sedimenta-
tion (either with or without chemicals) in order to
realize high removal efficiencies. If very high
quality effluent is the goal, the sedimentation with
chemicals would probably be replaced by chemical
clarification since nutrient removal may be
desired.
-------
12
56 Chemical Clarification - This alternative is simi-
lar to filtration in its high pollution removal
capabilities. Although filtration is capable of
removing smaller suspended materials, the
chemical process of this alternative is capable of
removing dissolved materials in addition to sus-
pended ones. It, too, will probably be feasible
only where very high quality effluent is necessary.
It is also not affected by toxic substances and can
be designed to operate automatically over a wide
range of flows. Screening is a prerequisite and
in cases where very high quality effluent is de-
sired, this alternative may be followed by
filtration. The high cost of construction and oper-
ation are the major disadvantages of this
alternative.
56 Land-use Planning and Implementation - Land-use
planning is similar to enforced controls, although
many benefits such as pollution reduction are less
tangible. It may be more easily implemented at a
lower direct cost. It can have tremendous envi-
ronmental impact, simply by designating areas
that may be either fully developed or must remain
in their natural state. The zoning of land as to its
permitted use is very important in determining
potential quantity and quality of pollutants in
stormwater runoff. In the stormwater quality
summary, it was indicated that more densely
developed areas would produce more pollutants
than sparsely developed ones, although both may
fall under the same land-use type. The only prob-
lem with this alternative is that land-use plans
can change either due to public or political pres-
sures or over a period of time the needs of the
community change which brings about the need to
change land-use zones. The zoning of land as to
its permitted use is very important in determining
potential quantity and quality of pollutants in
stormwater runoff. In the stormwater quality
summary, it was indicated that for the same gen-
eral land-use type, the amount of pollutant pro-
duction will vary with the completeness (density)
of development and the intensity of utilization.
A problem with this alternative is that land-use
plans can change either due to public or political
-------
13
pressures, or over a period of time, the needs
of the community change which brings about the
need to change land-use zones.
54 Sedimentation With Chemicals - This process is
similar to chemical clarification in that sedimen-
tation of chemically-generated floe is used to re-
move suspended material and in doing so removes
other pollutants, including bacteria and viruses,
oxygen-demanding materials, and toxic materials.
In most cases involving the need for a higher de-
gree of treatment than plain sedimentation can
provide or where land restrictions prohibit larger
surface detention impoundments, this alternative
will probably apply. Screening is required as a
preliminary process, but further concern for
chemical or biological constituents is not
warranted. Sedimentation can also be designed to
be fully automatic and able to handle a wide varia-
tion of inflows. Adequate chemical addition for
proper and efficient removal rates may be a pro-
blem, however, with the variation in stormwater
quality and quantity. Even with constant inflow
characteristics, there can be a significant varia-
tion in removal rate, and thus effluent quality.
54 Subsurface Detention - These facilities are gener-
ally reinforced concrete tanks buried under a
parking lot or other such facility in an urban area
where off-line storage is desired for a collection
system. They are only used where land use
restrictions or availability will not permit con-
struction of a surface detention facility and where
higher treatment is not desired. Although these
facilities can be similar in operation and removal
efficiency to other storage or sedimentation facili-
ties, their high cost of construction will limit their
use to very specific situations.
48 Dissolved Air Flotation - This method, when used
with chemicals, provides very good suspended
solids removal on combined sewer overflows which
contain a considerable amount of light organic
materials. However, its effectiveness on separate
storm water is not known at this time, although
good removals should be experienced. Because it
-------
14
requires greater skill to operate, and due to its
greater capital and operational costs, it does not
rank high as an alternative in stormwater manage-
ment. The only noteworthy advantage over conven-
tional sedimentation is the smaller space or land
requirement per volume of wastewater treated.
This alternative will probably be limited to use
where a substantial amount of flotage materials
(such as oil or grease) must be removed, since
other sedimentation facilities are not capable of
removing such materials.
47 Sedimentation (without chemicals) - This alterna-
tive has a considerably lower pollutant removal
potential as compared to sedimentation with chem-
ical addition. As a result, it will have very
limited applicability and should be considered only
after the various retention/detention, vegetative
cover, or sediment control alternatives.
47 Disinfection - This alternative ranks very low with
respect to others because it has essentially only
one function -- destruction of pathogenic organ-
isms. In this respect, disinfection is almost 100
percent effective when properly applied and is
relatively inexpensive when the public health as-
pects are considered. In cerain instances of down-
stream water use, disinfection could well be more
important than any alternatives that remove other
water-degrading substances. Therefore, due to
the potential presence of pathogenic organisms
in stormwater runoff from any source, disinfec-
tion should be considered an extremely important
alternative.
45 Conventional Street Sweeping - This alternative
differs from extensive sweeping in that mechanical
sweepers are used in a program that does not
restrict parking during sweeping periods. As a
result, only up to 50% of the solid materials
may be removed if the sweeper can gain access
to the curb area. Such programs in existence
should remain in effect and conside^ ation for more
extensive programs should be given.
-------
15
42 Extensive Street Sweeping - Because of the con-
siderable pollution concentration that has been
associated with street litter (particularly the finer
materials), the removal of this material from the
watershed can represent a considerable reduction
in the potential pollution of the receiving stream.
The word "extensive" refers to concentrated
use of vacuum type sweeping machines which have
been shown to be capable of removing up to 90%
of the street litter. The only apparent drawbacks
to the implementation of this type of abatement
program are the cost and the periodic incon-
venience to motorists due to the requirement
for no parking along the curb on sweeping
days. For these reasons it ranks lower than
conventional sweeping, even though pollutant
removal is higher.
36 Improved Solid Waste Practices - This alternative
is similar to the street-sweeping alternatives and
various enforced control methods. However,
although it is most effective in removing the larger
floating debris, only a negligible amount of other
pollutants are affected. It is a very desirable
practice in reducing rodents and their associated
health hazards and improving aesthetics of the
community. However, when compared to alter-
natives more closely related to storm water, it
ranks very low.
30 Bar or Course Screen - The removal of large
objects or floating debris is of primary importance
to both the aesthetics of a waterway and to the
successful operation of any form of treatment des-
cribed herein. Because of this and its relatively
low cost of construction and operation, screening
is considered to be an important alternative even
though it is of limited overall benefit.
9 Collection System Controls - This alternative
Fanks lowest due to its enfeasibility when con-
sidering the costs and effort that would be required
to effect a successful program of pollution
reduction. It would also be physically impossible
to clean all or a major portion of the storm sewers
of most urban areas between rainfall events. It
-------
16
appears that inflow reduction could be an effective
means of reducing flow volumes and rates, but this
alternative would be more easily implemented
under the "Enforced Controls" alternative.
4U.S. GOVERNMENT PRINTING OFFICE: 1976 622-358/380 1-3
------- |