.
A Survey of the Effects of the Pacific Grove Semage Outfall
on the Surrounding Intertidal Region.
by Charles Mitter
Hopkins Marine Station of Stanford University
I. Introduction
Pacific Grove, California, discharges its sewage after primary
treatment from an oceen outfall,located on a narrow spit within the
boundaries of the Point Pinos Lighthouse Reservation, a marine life
preserve. The end of the pipe is about 500 feet from the base of the
point and lies two feet below mean sea level in a rocky intertidal area,
fifteen feet from shore. (see fig. 1). The region receives heavy surf.
The purpose of the present study was to determine the effects of
this outfall on the adjacent shore areas as measured by the distribu-
tions, with respect to the point of discharge, of common intertidal
organisms, and to relate these results to local currents and to other
parameters of pollution, including plots of phosphate concentration,
dissolved oxygen levels, and coliform bacteria counts.
According to a study done for the Gity Council by Engineering Sei-
ence, Inc., flow volume of this waste, which is almost wholly of domes-
tic origin, averages about 1.8 million gallons per day (mgd) during dry
weather, and about 4.5 mgd during periods of prolonged rainfall. During
heavy winter storms, because of seepage into the pipe system, flow may
Permanent address:

3
.
Figure 1. Point Pinos and Location of Pacific Grove Sewage Outfall
— —
our fall
0

0
00
V
0
Foghorn

Sewage Plant

Arrows denote wash channels
permitting exchange across

point at high high water.
22
A
200
each peak hourly rates of up to 6 mgd. At such times, the plant is hes
ily overloaded, and incoming wastes receive so brief a treatment as t-
raw. Until April 1969, sludge accumulated in the diges-
emerge essentially
ter, itself minimally effective due to a large build-up of grit, was peri-
odically discharged through the outfall pipe. The digester has recentl
April 1969) been cleaned, and will now hold about a year's build-up o.
sludge. During this year, the City Council is making plans to move the
present outfall, built in 1952, out about 500 yards into much deeper wa-
ter; this construction, if the recommendations of Engineering Science are
followed, would be concurrent with a general program of improvement in the
city's treatment facilities, to include repair of the existing lines to re-
duce infiltration, and trucking of sludge to drying beds.
I would like to express appreciation to the City Manager and
ouncil of Pacific Grove for their kindly view of and help with this.stud
and for their dedication to the continuing improvement of the city's
sewage disposal practices. Also I would like to thank Nr. Colburn oi
cific Grove's sewage treatment plant for his time and willing assistance
inally, I would like to thank the staff of the Hopkins Marine Statiön,
especially Dr. Donald P. Abbott, without whose advice and encouragement
this project could never have been completed.
Local currents.
Inshore currents in the vicinity of the outfall were studied
tsing fluorecein dye. One such measurement is depicted in figure 2. Ar
essentially identical pattern to the one shown was observed under severa
different sets of wind and tide conditions during the study period (April-
Fig. 2- Typical Inshore Current Pattern around Pacific Grove Outfall
7
Fluorescein dye packet in (X at
1000, 29 May 1969.
5 knot wind from west; heavy surf.
Rising tide: low high water at
POINT PINOS
31, + 3.7 ft.
X - dye in at outfall, time 0.
200
- dye pattern after 1 min-

- after 4 min.

00
7 min.
IH
O
" 12 min.

0




Dotted line ----
indicates areas where
water carrying effluent
tends to sit with little
mixing
4
---
and would thus seem fairly constant. However, the study
conducted during only one of the three major ocean current periods; the
inshore pattern may vary with the oceenie "seaso
ffluent Dilution
Thosphate, a basic raw material needed by plants for the synthesis of
certain organic compounds, is often found in high concentrations in sewage;
the phosphate level in Pacific Grove's effluent is roughly 100 times that of
the receiving seawter. Nowever, because this ion is not ordinarily a limi-
ing growth factor in the ocean, this large excess does not tend to be ta-
gen up by living organisms. These facts, combined with the sensitivity of
the method of detection, make phosphate concentration a reasonable mea-
sure of effluent dilution.
Determinations were made of the phosphate content of the
ying distances from the outfall, using the method described by Stricklan
and Parsons. The results are shown in figure 3. The pattern apparent i-
generally that which might be predicted from the current studies discussed
above when these are combined with a knowledge of tide and effluent flow co
ditions at the time of sampling. The highest concentrations are found in
those areas where water carrying effluent tends to sit. To the west and
along the north side of the point (except when there is flow across chan-
1s), dilution is very great; beyond about 700 feet to either side of t
ny efe
se of the point, this test can no longer dete
Salinit,
is also a measure of
Because the effluent is fresh water, salil
fluent dilution. One set of such determinations was made, using a pocket
refractometer. The results, shomn in figure 3, generally agree with
196
Fig.
Phosphate
Joncentrations
lant Effluent
Hopkins Marine
Station
Hopkins Marine
Station
(8


Phosphate concentratior
(microgram - atoms/liter
5/29/69
5/28/69
5/28/69
a.m.
p.m.
7.120
10.0
7.240
.090
135
.160
.300
.185
.235
.255
.250
.360
1.60
.48(
120
.10
.09
.095
.090
.080
.080
T PINOS
Salinit
Samples taken with phosphate
samples 5/29/69.
Sample
Salinity as %
station
normal seawate
Effluent
0.0 %
100.
95.
400
3 - Thosphate Concentrations
Distributions based on data given
n facing page.
5/28/69
a.m.

I

+5
94
5/28/6
p.I
23
2:
1-
5/29/69
-0
11
Phosphate concentration as
fraction ofthat in effluen
1.0 - 0.04
.04 -.02
.02 .015
5/28/69
-4
+2*

Samples taken between 0845
and 0945, and between 1345
and 1430. Very heavy surf.
Effluent flow rate
- Tidal height
129169
+
48
55
0-

Samples taken between 1000

and 1100. Heavy surf.
400
the phosphate measurements made at the same time, however the method i
not sensitive enough to be of use in measuring large dilutiong.
Coliform bacteria counts
Coliform bacteria, which occur in the human intestine, are widely use
as an indicator of sewage pollution; where they are encountered there is alsc
the possibility of disease organisms being present.
Counts were taken on two dates during the study period, following the
procedure in Standard Methods of Waste and Water Analysis. Three primary
fermentation tubes at each of three dilutions were used, and a cowfirmed tes
as made using eosin methylene blue agar. The results are presented in fig-
ure 4. In general, these correspond well to the current and dilution patterns
discussed above, with the exception that an occasional high court may be found
at some distance away (see samples 3 and 11 in figure 4.). As these were al-
ways in shallow, protected areas, it would seem that bacteria (not necessaril.
from the effluent) sometimes happen into a pocket providing especially favorable
growth conditions, giving counts that do not reflect the actual level of ef-
fluent dilution (but perhaps significant frow the standpoint of public health).
Dissolved oxyger
Wicro-organisms tend to attack and break down at a high rate the ergan
tter discharged in sewage, using up in the process large quantities of
ogygen, which is vital to larger plants and animals. Thus, oxygen depletior
can be a mearure of sewage pollution.
Dissolved oxygen determinations were done concurrently with the coli-
form counts, using the standard Winkler titration method. The results are
Fig. 4 - Coliform Bacteria levels
Distributions based on data shown on facing page

9
5/13/65
2
Fost probable number
index per 100 ml.
100- 1,100
24 - 100
3/26/69
4 - 23
(Note: The California State Roard of Health terns " unacceptable
counits of over 1,000 ( most probable number index/ 100 ml.). The limit
proposed for surface waters above the suggested future Bay Delta out-
fall by the Bay Delta Water Quality Control Poard is a count of 10.)
400
Fig. 4 Coliform Bacteria Jevels
Sample station (refer
Coliform bacteria,
to top map on facing
Most Probable Number
page.)
Index per 100 ml.
5/13/69
5/26/69
(sand beach; calm)
(protected cove)
(protected cove
(sand beach; some
surge)
150
(tidepool; strong
surf at high tide)
(heavy surf)
1,100
(stagnant water at
low tide; strong
surf at high tide
(protected tidepool)
(protected tidepool
(sand beach; some
surf)
100
11 (protected cove
12 (protected cove)
raphs of tidal height and efflu-
ent flow rate on days of samp-
ling.
+
34t
3
2
+
Samples taken between
1000 and 1100. Fild
surf.
Effluent flow ra
Tidal height

amples taken betweer
200 and 1300. Heavy
surf.
+4
3.
Fig.
Dissolved Oxygen Levels
Samples taken concurrently with bacteria samples fron
5/13/69 and 5/26/69. See page 8 for tide and effluent
flow graphs.
denotes areas of significant (25% or mor
oxygen depletion. (Based on data presented
below.
Dissolved oxgen, milli-
gram - atoms per liter
Sample Station
5/13/69
5/26/65
69
.751
1 (shallow, little
surge)
2 (some surf)
.709
3 (heavy surf)
4 (tidepool; hea-
vy surf at
high tide)
(tidepool,rare-
ly awash,
6 (heavy surf)
(some surf
.60g
.66
8 (tidepool, some
surf at high
tide)
9 (moderate surf
.69
10
tidepool, no
S
flow
5/26/6
resented in figure 5. They seem to concur with the pattern of ef
spersal already established.
ertidal organism distribution
A survey of the distribution of common intertidal organisms around the
For the purpose of data organization, the
utfall is presented in table 1.
point was marked off into several sections, designated by number as shown ir
figure 6, areas within which the pollution effects seem to be of approxi-
nately uniform severity.
surrounding intertidal communities i
The effect of the outfall on the
pectacular within a radius of about 50 feet from the end of the pipe. Be-
yond this to the seaward, there is a rapid and striking change back to "nor
mal". Along the south side of the point,toward the beach, the effects ta
per off more gradually. Only those areas which have obviously been signifi-
cantly altered are treated in detail here. Subtler effects at greater dis-
tances surely exist; a more detailed study, for example, would probably re-
veal a change in the relative abundances of the various algal species alor
the shore to the south of the point. Such measurements, however, are beyond
the scope of the present surve
Fig. 6 - Areas within which pollution effeets are approrimately unifom.



2.
S.....
2.

1



5.
6.
-
—
6.
outal
(See facing page for list of common organisms.)
Area 1
General Remarks
Physical Descrintion of Araa
The most severely affected area. Few spe-
A boulder field bordered behind by an
cies; almost no algae other than diatom
irregular cliff 5 to 6 feet high, most
slime; those which are present are gene-
of which is washed by waves at high
rally very stunted, except for Entero-
tide. The entire area receives heavy
morpha (which is known to thrive in some
surf! Waves reflect from cliff, adding
kinds of polluted areas). The heavy slime
to turbulence. Area contains outfall
harbors a number of creatures which would
and receives heaviest effluent concen-
not otherwise be abundant. These and the
trations; the water is usually dark
chiton Cyanoplax seem to be the only ani-
brown, with a heavy scum at low water.
mals that thrive; presumably the slime
At low tide there is a violent smell,
mostly of chlorine, detectable more
affords them an ample food supply.
than a hundred feet from the outfall.
The outfall at a -1.0.ft. tide.
Ares
Distributions of Interti
refer to map (Figb).
Are
Intertidal zonation (approximate), taken from Ricketts and Calvin,
as follows
zone 1 - at or just above level of highes
high tides.
zone 2 - region between lower high water an
mean higher low water.
zone 3 - region between mean higher low wa
and meen lower low water.
zone 4.- region between mean lower low water
and lowest low tides.
description and general remarks on facing
es and Distributions of
Intert
Algae:
Enteromorpha intestinalis (green alga) - abundant just abe
tide mark on cliff just back of outfall.
Gigartina sp. (red alga) - forming a dense, stubby growth (less th
1" high) on some protected surfaces at upper and middle levels.
algal slime (during study period, mostly colonial diatoms, esp.
Acnanthes. ; some blue-green algae, bits of Entero¬
morpna.) - on all rock surfaces from about mean high tide mark
through middle zones.
Prionitis lanceolata (red alga) - stubby clumps (less than 2"
on rocks at lower levels.
Animals:
Acmaea digitalis (limpet) - small ones (under 2") near high t
mark on clilf. One 12" x 3' band had 13.
Balanus glandula (acorn barnacle)- patchy on cliff at all levels,
typical density about 100/ft.2; scattered individuals on boulders
Tetraclita sp. (red barnacle) - scattered individuals lower dowr
on clifi.
Pollicipes polymerus (goose barnacle) - occasional 2-3" clumps
of small ones (under ?") in cracks on cliff.
Tethymia aptena (larva; a'fly) - in slime on rocks of upper
and mid levels, esp. on cliff just back of pipe; one count
showed about 200 in a square foot.
yanoplax hartwegii (chiton) - numerous in cracks at all level
on aliff. One 4 ft. vertical crevice had 9.
Area 2
General Remarks
Physical Description of Area
Like area 1, a devastated section of the
A boulder field on a rock and gravel
intertidal. The red alga Prionitis is
substratum, sloping gradually onto a
gravel beach. Also includes a large
the only seaweed that seems well able to
gravel and rock bottom tidepool just
tolerate the polluted conditions. Niddle
and upper zone algae, when present, take
above and back of area 1. The area is
on stunted and all-but-unrecognizable forms;
about 60 feet. from top to bottom at a
many of the surf ces they might normally
-1.0 tide. It receives heavy broken
occupy have been taken over by Balanus.
surf. Especially on a rising tide, se-
Barnackes, several species of chitons,
wage flows into the area and sits, ma-
a tube worm, and slime inhabitants seem
king the water opaque.
to be taking advantage of unusually rich
food supplies.

Areas 1 and 2, with areas 5 and 6 in background.
Note outfall (arrow) and general ded appearance.
23
Area
Zone
Table 1 (cont.)
tion and general re-
See facing page for physical
lesc.
marks.
Names and Distributions of Conspicuous Intertidal Organisms.
Algae:
algal slime (as in area1) - on all rocks from lower middl
zone up to about level of lowest hich water.
Gigartina sp.
Rhodoglossum sp. (red algae) - forming dense, stubby (about +
high) patches on backs of many rocks of upper and middle levels.

Iridea sp.(red alga) - 5 or 6 small (blades less than 14") plants
on packs of many rocks in middle zones. Sometimes forms stubby
(about 1" patches 3-4" in diameter.
Heterochordaria abietina ( brown alga) - occasional 1-14" patche
on rocks about lower middle level.
Corallina sp. (coralline alga) - occasional small patches on rock
of lower levels.
Prionitis lanceolata (red alga) - covers most rocks at lowest level;
also in pools through middle zones. Takes many widely varied forms.
Gigartina spinosa (red alga) - occasional plants, occurring with Prio-
nitis.
Animals:
Balanus glandula (acorn barnacle) - on tops and sides of rocks at
all levels, esp. higher up. Densities as bigh as + 1000/ft.
Cirolana hartfordi (pill bug) - numerous under rocks at upper and
middle levels. One rock 8" in diameter sheltered about 50.
Tetraclita (red barnacle) - common in middle and lower zones, often
completely covering well-protected surfaces.
Tethymia (fly larva) - in slime and algae holdfasts in middle zone.
Cyanoplax hartwegii (chiton) - one or two in almost every depres-
sion in rocks of middle zones.
ttallina californica (chiton) - occasional individuals on rocks
at lower middle level.
Mopalia muscosa (chiton) - common on low rocks throughout lower and
middle zones, or 2 per meter2 of ground area.
Tegula sp.(turban snail) - scattered throughout area in protec-
ted spots; 3-4rock in lowest zone; numerous above slime in large tidepool
Dodecaceria sp. (tube worm) - dense masses of tubes on many rocks
of lowest zone.
Anthopleura xanthogrammica (giant green anemone) - common between
rocks at lower edge of lowest zone; about 10 in large tidepool bac
of area 1.
See facing page for list of common organisms.
Area 3
General Remarks.
Physical Description of Area
The area marks the beginning of the stri-
A boulder field as in area 2. Receives
king change in the intertidal life obser-
somewhat less direct but still heavy
ved as one moves seaward along the shore
surf. As the tide begins to rise, the
area is flooded with polluted water
from the outfall. In the space of a few
feet, several species appear for the first
flowing in from area 2; a little later
on, the area becomes the boundary where
time or become much more abundant; others
numerous close to the outfall begin to
cleaner water from outside and the cur-
rent carryng effluent around to the
disappear, most notably the heavy slime.
northwest meet.
area4. Note
e in vegetation
(
Area 3
Zone
(cont.
(See facing page for physical description and rema
Names and Distributions of Conspicuous Intertidal Or
Algae:
algal slime (as in area 1) - only on some low rocks wet most of
the time.
Ulva sp.(green alga) - large patches on some rocks in middle
zones.
Irigea sp.- plants 2-3" long, often 7-8 per rock at mid level.
Heterochordaria - common on tops of rocks in lower middle zone.
Lithophyllum sp. (red encrusting alga) - frequent large patches
at lower levels.
Egregia (strap algae) - occasional strands in lower middle zone.
Corallina sp.- sharing lowest rocks with Prionitis.
Prionitis lanceolata - tops of rocks in lowest zone and in pools
higher up.
Animals:
Balanus glandula - very numerous on all large rocks of upper
and middle zones.
Chthamalus sp. (least barnacle) - numerous on tops of rocks, occur-
ring with Balanus.
Acmaea digitalis and scabra (limpets) - numerous small (less than
ones on tops of rocks, occurring with Balanus.
Tegulå 4 turban snail) - numerous around bases of rocks, especially
in upper middle zone. Clusters of 40-50 not uncommon.
Cirolana hartfordi (pill bug) - under rocks.
Anthopleura elegantissima (an anemone) - large patches on side
of rocks in middle zones.
Tetraclita - often covers more protected rock surfaces in middle
zones.
Cyanoplay
(chitons) - occasional individuals.
Nuttallina
Mopalia
Dodecaceria - large patch on one rock.
Anthopleura xanthogrammica (giant anemone) - numerous between rocks
in lower and middle zones.
jee facing page for list of common organisms.
Area 4
General Remarks
hysical Description of Area
In this area the intertidal life re-
Boulder field as in area 3; somewhat less
turns essentially to "normal". The
heavy surf. Although this area receives
heavy slime is gone; the rocks are
some flow of water from near the outfall
covered with many kinds of algae,
for a brief period as the tide begins to
which largely displace the barna-
rise, it is soon being washed almost en-
cles and provide shelter for a num-
tirely by water from the west.
ber of other animals.
Area
General Remark:
Physical Desarintion
Apparently a badly damaged area. As in
A boulder pile sloping back to an irreg-
area 2, few species, stunted algae, with
ular cliff 6-7 ft. high. The base of the
few animals able to take advantage of
cliff is about the low high water mark.
a rich food supply.
Current carrying effluent south along
the point passes just in front of area,
which receives heavy direct surf.
Area 4
Area 5
Table 1 (cont.)
See facing page for physical description and remarks.
ames and Distributions of Conspicuous Intertidal Organisus
Seaweeds:
Animals:
Enteromorpha intestinalis
hthamalus (small brown barnac.
Tegula (turban snail)
Cladophora (green alga)
Eytilus (mussel)
Endocladia (red alga
Porphyra (red alga)
Acmaea (limpets)
Tetraclita (red barnacle
Pelvetia (brown rockweed
Isnochiton (chiton)
Iridea (red alga
Katherina (large black chitor
Gigartina (red alga)
Patiria (webbed sea star)
Egregia (strap alga
Anthopleura (sea anemone)
Corallina (red alga)
and others
Phyllospadix (eelgrass)
Laminaria (brown alga
and others
Algae:
algal slime (as in area 1) - on all rock surfaces up to about
low high tide mark.
Gigartina sp. (red alga) - occasional stubby clumps around base
of cliff.
Ulva sp.(green alga) - covers many rocks in upper half of boulde
pile.
Heterochordaria (brown alga) - fairly common just below U
Corallina - occasional small clumps at lower levels.
Prionitis lanceolata - covers most rocks in lowest zone.
Animals:
Chthamalus sp. (barnacle) - very numerous above slime level
cliff.
Balanus glandula (barnacle) - numerous around top of rockpile.
Tetraclita (red bernacle)- on protected surfaces around base of
cliff.
List of common organisms on
Area 6
Physical Description of Area
The area consists of 3 distinct sections-
(a) a flat shelf above the cliff of a-
area 1, receiving only heavy splash at
high tide; (b) a gently sloping rock
channel back of area 5, most of which
is awash only at high high tides. Con-
tains one large, landlocked tidepool;
(c) a very irregular rocky shelf re-
ceiving heavy surf, offering however
many different degrees of protection
from wave shock. Contains several
large tidepools. Water washing in as
tide begins to rise is brown and murky.
facing page.
General Remarks
Although this area is not as obvi-
ously "sick" as those closer to
the outfall, containing very many
of the most common species, it
could not be called unpolluted.
Some very familiar forms are
scarce or missing (such as the Ca-
lifornia mussel and the red alga
Endocladia), while others are
far more abundant here than might
be expected. (Examples being the
goose barnacle and the chiton Nut-
tällina.). As in other areas, middle
zone algae are scarce and tend to as-
sume highly atypical forms.
Tidepool in area
6. Note dense
population of
Pollicipes on
rock in back-
ground.
(co
Area
Zone
Area 6
Table 1 (con
ames and Distributions of Gonspicuous Intertidal Organisms
Tegula (turban snail) - numerous in one protected rock pool.
Pollicipes (goose barnacle) - scattered small clumps of small ones
near top of slope; some large rocks at south edge of area have dens
populations.
Tethymia aptena (fly;larva) - very numerous in slime on top half c
slope.
Cyanoplax hartwegii (chiton) - common in cracks at upper mid level
Nuttallina (chiton) - about one/ square meter, occurring below
yanoplax.
Mopalia muscosa (chiton) - almost one to a rock at lower levels.
Anthopleura xanthogrammica (giant anemone) - occasional ones betwee
rocks in rowest zone.
hysical description and remarks on facing page.
s and Distributions of Conspicuous Intertidal Orgånisms
Algae:
Enteromorpha intestinalis (green alga) - common on rock shelf over-
looking outfall.
Rhodoglossum sp. (red alga) - frequent patches at upper levels.
Gigartina sp. (red alga) - frequent clumps at upper levels; also forms
a stubby covering on some rocks lower down.
Iridea sp. (red alga) - scattered small plants (2-3 ") at upper
mid level, especially in shaded cracks.
Lithophyllum grumosum (encrusting coralline alga) - frequent arg
patches on shaded surfaces of middle zone.
algal slime (as in area 1) - on some rocks in places flooded but
not rapidly flushed at high tide. Obvious but not measureably thick
on rocks in large landlocked tidepool.
Heterochordaria abietina (brown alga) - often forming dense beds on
relatively exposed middle level rock surfaces.
Egregia (strap alga) - occasional plants in tidepools, at lower
middle level.
Area 6
—Zone.
Table 1 (cont.
cor
Names and Distributions of Conspicuous Intertidal Organisms
Corallina sp. (coralline alga) - very common on rocks at lower
middle and lowest levels.
Prionitis lanceolata (red alga) - occasional plants in lowest zone;
common in tidepools flushed at high tide.
Laminaria sp. ( brown alga) - abundant in lowest zone.
Bossea sp. (coralline alga) - covering rocks from lowest intertida
level down into subtidal.
Animals:
Chthamalus sp. (small brown barnacle) - dominant barnacle of upper
levels, often completely covering rock surfaces.
Balanus glandula (acorn barnacle) - common just below Chthamalus;
never dense.
Tegula (turban snail) - extremely numerous in channel containing
pipe.
Acmaea digitalis & scabra (limpets) - common higher up.
ganoplax hartwegii (chiton) - occasional in cracks at upper mid level.
Nuttallina (chiton) - numerous on shady surfeces of middle zone, as
many as 15-18 per square meter.
Tetraclita (red barnacle) - abundant on more protected surfaces of
middle zone, often forming dense coverings.
Pollicipes (goose barnacle) - very dense populations covering most
rather exposed rock surfaces of middle zone. Nost individuals smal
(under 1").
tilus californianus (mussel) - infrequent small individuals (under
4 ") in some Pollicipes clumps.
Lottia gigantea (owl limpet) - occasional individuals in cracks at
all levels above lowest.
Acmaea, mostly A. limatula (limpets. Common in tidepools, esp. in
large landlacked tidepool, where one count showed 11 in a suare foot.
Anthopleura xanthogrammica (giant anemone) - common in pool and in
mid and lower zone crevices.
Haliotis cracherodii (black abalone) - occasional individuals in
crevices lower down.
Strongylocentrotus purpuratus (purple sea urchin)- very numerous
in one large tidepool.
Katherina tunicata (large black chiton)- 1-2/ meter2 in lowest zone.
Pachygrapsus crassipes - common everywhere at low tide.