WATER POLLUTION CONTROL AOMIN I STRATI ON
NORTHWEST REGION, PAC F1C NORTHWEST WATER LABORATORY
HOUSEBOAT WASTES:
METHODS
FOR COLLECTION
AND TREATMENT
JUNE 1967
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HOUSEBOAT WASTES
METHODS FOR COLLECTION
AND
TREATMENT
Prepared by
B. D. Clark
Technical Projects Branch
U. S. Department of the Interior
Federal Water Pollution Control Administration
Northwest Region
Pacific Northwest Water Laboratory
Corvallis, Oregon
June 1967
LIBRARY
Oept. of the Interior.
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TABLE OF CONTENTS
Page
I. INTRODUCTION 1
A. Authority 1
8. Purpose and Scope 1
C. Problem 1
II. SUMMARY 5
III. WASTE CHARACTERISTICS 11
A. Waste Quality 11
B. Waste Quantity 11
IV. PLUMBING REQUIREMENTS 17
A. Houseboats 18
B. Other Floating Structures 29
V. MOORAGE COLLECTION 33
A. Collection System 33
B. Moorage Lift Stations 40
VI. TREATMENT 47
A. Individual Methods 47
B. Group Methods 52
VII. EXAMPLE DESIGN 61
A. Basic Design Criteria 61
B. Layout and Cost Estimates 63
VIII. BIBLIOGRAPHY 71
IX. APPENDIX 73
Appendix A - Plumbing Costs for Three Houseboats in
Seattle, Washington 75
Appendix B - Design Curves for Multiple Pump
Systems 79
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LIST OF FIGURES
Figure Page
No. Title No.
1 Houseboat Water Use Pattern 14
2 Houseboat Plumbing Plans 20
3 Centrifugal Sump Design 27
4 Recirculating Toilet and Macerating Pump
Application 30
5 Walkway Connections 36
6 Moorage Collection Costs 39
7 Centrifugal Sump Pump Installation t 41
8 Moorage Lift Station 42
9 Extended Aeration Treatment Costs 55
10 Floating Restroom & Sewage Treatment Plant Used in
Conjunction with Boating and Other Marine
Activities 57
11 Floating Restroom & Sewage Treatment Plant Used
with a Boat Holding Station Evacuation System ... 58
12 Settling Tank and Chlorination Treatment 59
13 System Design 62
14 Design Curves for Multiple Pump System for
Various Inflow and Pumping Rates 83
15 Design Curves for Multiple Pump System for
Various Inflow and Pumping Rates 84
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LIST OF TABLES
Table Page
No. Title No.
Average Wastewater Quality from Three
Individual Homes 12
Quantities of Sewage Flow 15
Estimated Costs for Plumbing a One-Bathroom,
Single Story Houseboat with Copper, Cast Iron,
and Plastic Materials 22
Houseboat Plumbing and Pumping Methods Summary . . 32
Comparison of Feces and Urine Waste Quantities
to Total Household Wastes for a Family of Five
People 50
Soil Absorption Areas Required for Single
Houseboats for Various Percolation Rates 53
Cost Summary 69
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ABSTRACT
Methods of collection and treatment for houseboat and moorage
wastewaters are reviewed. Several methods using alternative
materials are considered and approximate installed costs are
given. Emphasis is on solution of the problem in the State of
Oregon but information developed is applicable in adjacent states
and elsewhere with appropriate adjustments.
ii
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ACKNOWLEDGMENTS
This study was made possible through the assistance of the
following State and local agencies and individuals:
1. Oregon State Sanitary Authority
Portland, Oregon
2. Floating Homes Association
Seattle, Washington
3. Waterfront Property Owners Association
Portland, Oregon
4. King County Health Department
Seattle, Washington
5. City of Seattle Engineering Department
Seattle, Washington
6. Hersey Sparling Meter Co.
Seattle, Washington
7. City of Portland Water Bureau
Portland, Oregon
8. Parkrose Water District
Portland, Oregon
9. Master Equipment Co.
Portland, Oregon
10. Cornell Pump Co.
Portland, Oregon
11. H. D. Fowler Co.
Seattle, Washington
12. DeFirs Moorage
Portland, Oregon
13. Waterly Lane Moorage
Portland, Oregon
14. Portland Rowing Club
Portland, Oregon
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15. Mr. Terry Pettus
Floating Homes Association
Seattle, Washington
16. Mr. Fred Repp
Master Equipment Co.
Portland, Oregon
17. Dr. Donald Guthrie
Professor of Math
Oregon State University
Corva His, Ore gon
iv
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HOUSEBOAT WASTES
METHODS FOR COLLECTION AND TREATMENT
I. INTRODUCTION
A., Authority
The Pacific Northwest Water Laboratory of the Federal Water
Pollution Control Administration, Northwest Region, was requested
by the Oregon State Sanitary Authority, letter dated January 19,
1966, to conduct,
"A study of methods and costs of treatment and/or
disposal of sewage wastes from houseboats and other
floating structures."
The Federal Water Pollution Control Act, P,L» 84-660, as amended
by the Clean Water Restoration Act of 1966, Section 5b, provides
the Federal authorization for this study.
Bo Purpose and Scope
The purpose of this study is to develop findings on wastewater
characteristics, together with methods and costs of collection and
treatment of sewage wastes from houseboats and other floating
structures. The study area for the report included the States of
Washington, Oregon, and California with primary emphasis on the
State of Oregon„
C. Problem
In three Pacific Northwest States, California, Oregon, and
Washington, there are over 1200 houseboats and many other floating
structures such as boathouses, commercial establishments, floating
restaurants, and public restrooms that discharge untreated sewage
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wastes directly to waters over which they are moored,, Few of these
structures have plumbing systems.
All three states presently have legislation in varying forms,
both local and State, that require houseboats and other floating
structures to treat their sewage before discharge or else require
complete removal to existing shoreside sanitary sewers.
In California, State law prohibits the discharge, of untreated
sewage to waters of the State and action is being taken by the
California Water Quality Control Board in the form of cease and
desist orders against property owners that have houseboats moored
at their property. The State has had little success to date in
enforcing these orders.
In Washington, most houseboats are located in the City of
Seattle and are required by city and county ordinances to connect
to a recently constructed city sewer by June 1967. Development of
acceptable collection methods and difficulties with local contractors
on construction costs indicate that the June 1967 deadline will not
be met.
In the State of Oregon, houseboats and other floating structures
will be required specifically by State law (ORS 449.150) to provide
adequate treatment for all wastes discharged to State waters
effective September 1, 1967. This time limit has recently been
extended by the Sanitary Authority to January 1, 1968, for the
installation of waste treatment facilities for toilet wastes.
Treatment facilities for kitchen, bath, and laundry wastes (not
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including garbage or human excreta) were given an extension of
time from September 1, 1967, to January 1, 1971, provided adequate
facilities were installed for toilet wastes and acceptable
progress reports are submitted on January 1, 1969, and January 1,
1970, demonstrating the development of a satisfactory plan
acceptable to the Authority for the disposal of the kitchen,
bath, and laundry wastes.
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II. SUMMARY
Findings of this study on methods for the collection and treat-
ment of wastes from houseboats and other floating structures are
summarized below:
1. The study area for this report includes the States of
Washington, Oregon, and California which have over 1200 houseboats
and many other floating structures requiring sewage collection
and treatment facilities.
2. With rare exception, houseboats and other floating
structures discharge untreated domestic sewage from toilets,
kitchens, and baths directly to the water in violation of State
statutes and water quality standards, and this may constitute a
health hazard to other water users.
3. Average daily houseboat wastewater quantities are similar
to those for normal land residences with a daily per capita flow
of 75 gpd. The average 16-hour flow is also similar with a per
capita flow rate of 95 gpd.
4. The quality of the houseboat waste is expected to be
similar to that for a normal land residence. A separate report
will present data on the quality characteristics of the houseboat
waste.
5. The collection and treatment of houseboat wastes will be
more expensive than most land-based installations because of their
location.
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6. Few houseboats have adequate plumbing systems, requiring
major replumbing to collect and treat wastes. Several methods are
presented for replumbing. The range of costs are estimated from
$230 to $800 for a single story, one bathroom houseboat. Plastic
PVC pipe costs the least. This material is not approved for use
in Oregon or Washington for interior plumbing but is acceptable in
California.
7. Central collection of all wastes is recommended wherever
possible requiring that moorages provide central collection
facilities for houseboat wastes and wastewaters from other floating
structures. Costs for above water, pressure moorage collection
systems installed were estimated to range from 8% to 83 cents per
houseboat per foot of moorage length using cast iron pipe and 5
to 48 cents per houseboat per foot of moorage length using PVC
plastic pipe for moorages ranging in size from 50 to 5 houseboats,
respectively. Costs would be significantly higher for gravity
underwater collection systems.
8. Houseboats located on rivers or waters with a large tidal
fluctuation may require individual pump units to maintain collection
lines above water. Individual houseboats on these waters may or
may not require pumps depending on whether they treat their wastes
on shore or on the water with a floating facility. Several pumping
methods have been considered that range in price from $275 to $1500,
not including installation costs.
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9. Houseboats located on lakes or other relatively quiet
bodies of water could use either gravity underwater systems to a
central lift station or individual pumping units for pumping
direct to shore.
10. Moorages on widely fluctuating rivers may find it
necessary to install lift stations on auxiliary floats to lift
the waste to shore-based treatment facilities or public sewers.
These units can be purchased in a price range of $2500 to $7100.
11. Recirculating toilets may find application where the w.aste
volume is significant. This would be the case for intermittent
waste sources that choose to hold the wastes with periodic cleaning
of the holding facilities.
12. Pumping all wastes to a shore sewer is the least expensive
and most practical alternative wherever this is possible. It has
been estimated that exclusive of city or other municipal group
connection charges, a houseboat could pump all wastes to a city
sewer for a cost ranging from $1000 up.
13. Individual treatment devices including macerator-chlorinator
toilets, incinerator toilets, septic tanks with soil absorption
fields, and aerobic extended aeration units were considered.
14. Macerator-chlorinator units presently available commercially
are not recommended for use in treating wastes from the floating
structures considered in this report.
15. Incinerator toilets provide satisfactory treatment of
toilet wastes with proper operation and maintenance. They are
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not satisfactory when considering the entire household waste. The
estimated costs for these units installed will range from $350 to
$575 per unit.
16. For no more than one houseboat, a properly designed and
constructed shore septic tank with soil absorption field would provide
satisfactory treatment in areas where soil conditions and local regu-
lations permit. Such a system installed would cost from $1100 up.
17. Aerobic biological treatment units with disinfection
facilities would provide satisfactory treatment of all wastes in
most waters of the study area. Packaged units are available
commercially that could be used in either a floating- or shore-
type of installation. Costs for a floating unit would range from
$1800 to treat the wastes from a single houseboat, to $200 per
houseboat for the wastes from 50 houseboats,
18. Commercially available biological treatment units are over-
sized for individual houseboat applications making them bulky and
prohibitively expensive. There is a need for an economical individual
household secondary treatment device capable of operating satisfactorily
with a minimum of operation and maintenance.
19. Primary settling with sludge removal facilities and chlori-
nation of the effluent could be considered as an interim method of
treatment. This process may find application where sewers are not
presently available but are contemplated in the near future. The
lower degree of treatment will not interfere with other beneficial
uses of the water. A system adequate to serve up to 25 to 35 house-
boats could be fabricated for $500 to $700, excluding labor costs.
8
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20. A system design with three alternatives was made for a
typical, moorage in the Portland, Oregon, area. The design
considered: (1) pumping with centrifugal pu;up=i from each house-
boat to a lift station for further lifting to a city sewer,
(2) pumping with centrifugal pumps directly to a city sewer
from each houseboat, and (3) pumping with pneuratic ejectors
to a floating treatment facility. The cost to r.he individual
houseboat owner for each plan was $935, $1360, and ^1460,
respectively. The first cost to the moorage owner for each plan
was $7500, $4600, and $8700, respectively. These figures do not
include annual costs for financing, operation, and n.aintenance.
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III. WASTE CHARACTERISTICS
Houseboat waste is purely domestic in nature and is expected
to be similar in both quality and quantity to that of a normal
land residence. A literature search was made to characterize
the houseboat waste on the basis of normal household character-
istics but, the available information is limited particularly on
an individual household basis. That which was found, together with
field data collected to date, is reported at this time,,
A. Waste Quality
Watson et al^ ' report on the quality characteristics of
wastewaters from several individual land residences obtained in
an extensive sampling program of several years. These data are
expected to be characteristic of houseboat wastes. Table 1
summarizes data from this report for three homes.
B. Waste Quantity
The reported average -residential sewage flow per capita is
approximately 75 gallons per day (gpd) with a range from 27 to
200 gpd.(2)(3) The percent distribution of this flow has been
estimated as follows:
Waste Source Reference 2 Reference 3 Average
Kitchen Wastes 13.3% 6% 107.
Toilet Wastes 33,4% 41% 38%
Showers, Washbasins, etc. 33.370 37% 35%
Laundry Wastes 20.0% 4% 12%
The basic design flow variations used for small Army
installations are reported on page 13.
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TABLE 1
Average Wastewater Quality from Three
Homes after Watson(l)
ANALYSIS (mg/1)
Total Solids
Suspended Solids
Total Volatile Solids
COD
BOD5
Detergents
Total Nitrogen
NH3 -Nitrogen
Total P04
Ortho-PC>4
Grease
PH
Flow (gpd)
Family Characteristics
Total People
Children
Home Laundries
Dishwashers
Baths
HOME 1
866
363
468
705
542
5.3
69
53
47
31
95
8.0
388
Home 1
5
2
1
1
5
HOME' 2
788
293
414
540
284
5.2
61
48
70
40
33
8.0
331
Home 2
5
3
1
1
3
HOME 3
1249
473
659
882
479
6.9
121
92
65
40
66
8.3
123
Home 3
5
1
1
1
1
12
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Basic Design Flow Variations
for Small Army Installations
Condition Per Capita Flow, gpd
24-hour average 70
16-hour average 37.5
4-hour maximum 122.5
Extreme Peak 210
At this writing, limited data have been obtained on the waste
discharge from houseboats. Assuming that the waste disposal
pattern would parallel the water consumption with a certain time
lag between usage and discharge and a small consumptive loss,
water use was monitored at several moorages.
The measured average houseboat per capita water consumption
is 78 gpd, based on the use at two moorages in the City of
Portland (Portland Rowing Club and Water Lane Moorage) and one
moorage in the City of Seattle. This is based on data for 1585
houseboat-months water use. With a 5 percent consumptive loss,(l)
the average waste discharge is 74 gallons per capita per day (gpcd)
which agrees closely with figures reported previously.
Data on hourly flow variations were obtained by installing a
continuous recording device on a water meter serving the Waterly
Lane Moorage located on the Willamette River in Portland, Oregon.
Figure 1 averages these data for two weekend periods. Analysis
of the data indicates good agreement with those reported previously.
Waste quantities from other floating structures can be
estimated from Table 2 reproduced in part from the Manual of Septic
Tank Practice.(2)
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TABLE 2
QUANTITIES OF SEWAGE FLOW
Type of Establishment
Single family dwellings
Restaurants (toilet & kitchen wastes/patron)
Restaurants (kitchen wastes/meal served)
Public restrooms (toilet wastes only)
Sewage Flow*
75 gpcd
7-10 gallons
2%-3 gallons
5 gallons/
patron
Public bathhouses (bathhouse, showers, toilets) 10 gpcd
Stores (per toilet room)
400 gallons/
day
*If recirculation toilets are used, the volume of toilet waste
could be calculated on the basis of four gallons per 80 usages,
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IV. PLUMBING REQUIREMENTS
To provide treatment for wastes from houseboats and other
floating structures, the wastes must first be collected and trans-
ported to a single point. In the case of houseboats that treat
their wastes individually, this point may end at the houseboat.
For a moorage with a number of houseboats, boathouses with sanitary
facilities, and other structures with liquid waste discharges, a
common collection system with a single treatment facility is the
most economical approach.
The problem of collection is complicated by flood stage
fluctuations on the rivers (as much as 27 feet on the Willamette
and Columbia Rivers in the vicinity of Portland), river currents,
floating and submerged trash, tidal fluctuations, and the fact
that few of the existing houseboats and other floating structures
have plumbing systems. To overcome these problems, individual
pumping units at each waste source with sufficient capacity to
pump the waste to a shore-based facility or a facility at the
moorage level were considered. An alternative to the individual
pumping units would be to retain the waste in a holding tank and
use a portable pump to empty the holding tank periodically. Gravity
systems could be used on lakes and other quiet bodies of water but
these were not considered in this report,
This section is composed of two portions dealing first with
the individual collection, holding, and pumping systems, and
second with the moorage collection and pumping systems.
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It is expected that the individual will be responsible up to
the point of system connection and the moorage will be responsible
for providing a conveyance system and holding tank emptying facilities,
if necessary.
A. Houseboats
The waste collection may require complete replumbing and indivi-
dual pumping units or simple holding facilities with provision made
for draining periodically. In areas where gravity systems can be
utilized, replumbing may be all that is required.
The drainage system of houseboats, boathouses, and other float-
ing structures with few exceptions, is composed of vertical drain
lines from each fixture discharging directly to the water. Because
all wastes, including kitchen, laundry, and bath, require treatment,
most houseboats will require complete replumbing. Also, in area's
where necessary to maintain lines above water, each structure will
have to be provided with a pump unit or a holding tank.
1. Plumbing Methods
Methods and materials for plumbing installations on house-
boats and other floating structures must comply with State and/or
local plumbing codes except when alternatives are approved by the
plumbing department with jurisdiction. It is recognized that there
are structural and financial problems involved unique to the existing
houseboats which may justify relaxation of certain code requirements
to effect a reasonable solution.
The Floating Homes Association, Seattle, Washington, which
represents about 500 houseboats located on Lake Union within the
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City of Seattle, together with the City of Seattle Plumbing Depart-
ment has developed an acceptable plan for replumbing existing
houseboats. At this time approximately 80 houseboats have been
plumbed according to this plan. This basic plan, modified to
meet the State of Oregon Plumbing Code, is presented in Figure 2.
This method of plumbing for houseboats facilitates
construction and minimizes the expense involved, yet provides
a completely workable system. In the future, all houseboats
without exception will be expected to comply with State or
local plumbing codes.
Approved materials for replumbing are specified by most
State or local codes. In Oregon, the State plumbing code requires
that all fixtures be trapped and that waste discharge piping be
either galvanized steel, galvanized wrought iron, cast iron, brass,
lead pipe, or copper tube. Plastic pipes, Acrylonitrile-Butadiene-
Styrene (ABS), or Polyvinyl Chloride (PVC), that conform to the
temporary standards of the U. S. Department of Commerce (CS270-65
for ABS pipe and CS 272-65 for PVC pipe) are acceptable for use
in California but are not approved in Oregon or Washington. The
National Plumbing Code has proposed revisions to include plastic
pipe and fittings for water, sewer, drain, and waste lines„ When
and if these revisions are made, Oregon and Washington, as well,
may allow the use of plastic materials.
To provide relative cost estimates for replumbing house-
boats, a typical floor plan for a one bathroom, single story
houseboat was chosen and cost estimates were made for replumbing
•
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" IF OVER 4' FROM ./TUB SHOWER
IF OVER 4' FROM MAIN WASTE
INDIRECT WASTE TO SUMP
EITHER DOCK OR INDIVI-
DUAL HOUSE SUMP,
PLAN 3
NOTE: BASIC PLUMBINO PLANS WHICH MEET
OREGON CODES.
CONTACT LOCAL STATE,COUNTY OR CITY
PLUMBINO DEPT. WHEN DESIGNED FOR
STRUCTURES OR VARIANCE IS
NECESSARY.
HOUSEBOAT PLUMBING PLANS
FIGURE 2
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with copper, cast iron, and plastic materials according to the
plan illustrated by Figure 2. The cost of material was based on
an average of unit prices at local distributors in the State of
Oregon. Unit labor costs were estimated at $9.50 per man-hour and
the construction time at 40 man-hours using copper pipe.* Construc-
tion time for the other two materials was based on a recent article
by Pierce using copper material as a reference,(5) These times are
given as follows?
Relative
Construction
Material Time
Copper 1.0
Plastic (ABS or PVC) 0.35
Cast iron 1.83
The estimated cost for replumbing a one-bathroom single story
houseboat is $230 with plastic materials, $560 with copper
materials, and $800 with cast iron. These costs are summarized
in Table 3.
The estimated labor costs in Table 3 can be reduced
significantly if the owner assists in the work as indicated by
three examples of houseboat replumbing presented in Appendix A.
The owners did their own carpenter work and assisted the plumber
which reduced the average construction time by a factor of two.
It should be noted that the construction times for cast iron and
plastic materials are hypothetical and may differ significantly in
practice.
*Based on figures provided by University Mechanical Contractors, Inc.,
Seattle, Washington, for three houseboats. See Appendix A for details,
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TABLE 3
ESTIMATED COSTS FOR PLUMBING A ONE-BATHROOM, SINGLE STORY
HOUSEBOAT WITH COPPER, CAST IRON. AND PLASTIC MATERIALS
Type
Copper
Cast Iron
Plastic (PVC
2.
Cost of
Materials
$ 180
$ 110
or ABS) $ 100
Pumping Methods
Labor
Costs
$ 380
$ 690
$ 130
Total
Cost
$ 560
$ 800
$ 230
Where pump units are required, the houseboat drainage system
should tie into a small sump with a pump or ejector to convey the
waste under pressure to point of treatment or disposal. The sump
or ejector which could be connected to the houseboat float should
conform to the following design criteria;
a. Storage capacity excluding pump of at least 20
gallons.
b. Material should be cast iron, fiberglass,
aluminum, PVC, or steel coated with an asphalt or epoxy compound.
The weight of the sump should not be excessive.
c, Maximum liquid level in the sump should be 30
inches below the moorage connection, if possible.
d. Inlet diameter should be a minimum of 3 inches
and the outlet diameter a minimum of 2 inches. If suitable
maceration precedes the pump, the outlet can be reduced even more.
e. Adequate venting should be provided. A 2-inch
vent extended above the roof line is suggested.
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f. There must be no overflow from the sump.
g. It should be located or protected in such a
manner as to prevent damage from boats, swimmers, floating or
submerged debris, and to facilitate maintenance and inspection.
In pump selection, there are a number of alternatives
open to the houseboat owner depending on his location and whether
treatment is provided on shore or on the water.
If the waste is treated on shore, which is recommended
wherever feasible, the pump capacity should be 55 gpm at heads
varying from 10 to over 40 feet. An arbitrary selection of 20
feet was made to differentiate between high and medium head pumps
on the basis of several typical head-capacity curves. The capacity
of 55 gpm was selected on the basis of providing a 2.5 feet per
second (fps) velocity in a 3-inch pipe.
High head pumps would be required for pumping directly
to shore in the Portland, Oregon, area. In nearly all other areas
where houseboats are located in the States of Oregon, Washington,
and California, medium head pumps could be used for pumping wastes
to shore.
If the waste is pumped to a floating treatment facility
or to an auxiliary lift station used in place of individual high
head pumps, a low head pump should be used with a capacity of at
least 55 gpm at a head of 0 to 10 feet.
Two types of pumps have been considered; pneumatic
ejectors and centrifugal pumps.
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Pneumatic ejectors consist essentially of a closed tank
into which sewage flows by gravity until it reaches a certain depth.
Then air under pressure is admitted into the tank to displace the
sewage through the discharge line until the low water level control
cuts off the air supply. Ejectors require one-way valves on both
inlet and outlet pipes, venting on the inlet side, level control
mechanisms, and a source of air under pressure. For individual
houseboat pumping, pneumatic ejector units should provide their
own air supply. If pneumatic systems were standardized on all
houseboats, perhaps moorages would provide the air supply, but this
possibility is unlikely.
Pneumatic ejectors have the advantage of operating satis-
factorily over a wide range of heads from a minimal to a high head,
and to pass solids equal in size to the inlet and discharge piping.
Their main disadvantages include problems with check valves seating
properly, air control, and their high initial cost. While they are
not free from operating problems, they are usually superior to centri-
fugal pumps that handle raw sewage.
Pneumatic ejectors are ideally suited for houseboats in
principle because of their adaptability to various head requirements
and their nonclog characteristics. However, few commercially
available units are economically feasible for houseboat application.
At present, an ejector specific for houseboats for pumping
up to heads of about 20 feet is being developed in Portland. This
work is aimed primarily at developing a unit that is small, self-
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contained, that minimizes problems with controls and check valve
clogging on the inlet side, and that has a significantly lower cost.
A test unit has been constructed and will be operated on a
houseboat for several months to obtain data on its operation.
An approximate cost of this unit exclusive of valves, fittings,
and the small compressor to activate the ejector is $550. The
additional cost of valves, fittings, etc. and the compressor would
run between $150 and $200 for a total price of approximately $750.
An ejector sufficient to pump against higher heads would be
considerably more expensive--on the order of $1500.
Radial flow centrifugal pumps, submerged or dry, were
considered as applicable for individual houseboat pumps. This
type was chosen because it is less expensive than other types of
pumps and is available commercially in packaged sump type
installations.
Centrifugal pumps are compact and less expensive than
pneumatic ejectors. Their main disadvantages include: (1) operating
head limitations and (2) clogging problems due to rags, stringy
material, and other solids found in raw sewage.
High head centrifugal pumps are available commercially
and, with minor modification, can satisfactorily pump houseboat
wastes ashore in high head pumping areas. Modifications include
throttling of the flow to reduce velocities when the total pumping
head requirement is low. This may also necessitate maceration of
the sewage prior to pumping in order to maintain a system free from
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clogging, It is estimated that a high head pump and sump, not.
installed, would cost at least $450. With maceration precedio^ the
pump, the cost is estimated at $600.
Low head centrifugal pumps are also available commercially
and could be used without modification for pumping ashore in .iteas
with a 10- iv 20-foot head requirement. A packaged sump and pu> \-
of this type is estimated to cost at least $330 not installed
A. less, expensive low head centrifugal pump could be us-^sl
for pumping at the moorage level against heads less than 10 feet
but would require some modifications. Throttling of the discharge
which may in turn require maceration would be necessary or the static
lift would have to be increased above 3 feet to assure dependable
service. The cost for this type of pump with sump riot installed
would be at least $275. To provide adequate maceration prior to
the pump would cost on the order of $150 for a total price of $425.
A submersible type of centrifugal pump application that
could be used when throttling is required is illustrated schematically
by Figure 3. This design includes a food grinder on the inlet and
a gate valve on the discharge line for throttling. The grinder
macerates the sewage solids which reduces pump and valve clogging.
Throttling should be avoided if at all possible since this requires
additional and frequent maintenance.
The disadvantages to this design should be carefully
considered before actual installation. These are:
26
-------
3" Flexible Pipe
to Houseboat
2" Vent
to roof lineN
/O-IO, I0-30psi Pressure Gage
,2" Gate Valve
Union ^^—Clamped Connection
2"Flexible Pipe
2* Discharge Pipe
-See State code for
approved material
2'-6"
MINI.
NOTE: inlet, Outlet and Vent pipes require watertight
seals.
Clamped connection can be used as safety
shear section.
Food Grinder is optional feature-not
recommended unless throttling required.
CENTRIFUGAL SUMP
FIGURE 3
-------
a. The use of food grinders on raw sewage has serious
drawbacks, because they were not designed for this type of operation.
Any rags, sanitary napkins, or other long stringy material would
most likely clog the grinder and require manual cleaning. The life
of the unit under these conditions is unknown and in most cases
standard warranties would not be applicable. There is only one
instance reported in the literature of a similar setup using a food
(1)
grinder to precede a pump. Watson et al. report using a food
grinder in their waste sampling apparatus for several individual
households for several years with no apparent difficulties.
b. The grinder would have to be modified by placing
the manual restart switch outside the sump and the motor would have
to be sealed to water tightness.
c. A switching mechanism is also required to start
the grinder when there is flow to the sump.
d. Few centrifugal pumps in a feasible price range
for houseboat use will pass rags, sanitary napkins, etc. without
clogging. The use of these pumps requires either close control
over what is discharged to the sewer or frequent maintenance.
A unit with the grinder option has been constructed and
is being used in a 6-week houseboat sampling program in Seattle,
Washington. Data on the installation cost and operation of this
unit will be made available in a separate report.
An alternative to use of a food grinder would be to install
a macerating type pump in the interior plumbing system of the structure.
28
-------
This type of pump is commercially available and is used widely for
draining mobile home holding tanks and other types of sewage hold-
ing facilities where the pumping head is less than 4 feet.
This alternative has the advantages over the food grinder
of being a tried and tested unit and is considerably less expensive.
It is estimated that this unit could be installed for approximately
$100 and would result in additional savings by allowing the use of
plumbing materials no greater than 2 inches. Figure 4 gives a
schematic layout of this system.
Table 4 summarizes the various plumbing and pumping methods
with their associated costs.
B. O.ther Floating Structures
For floating structures other than houseboats, with inter-
mittent, usage, such as boathouses, public restrooms, etc., a
number of commercially available devices could be employed for
the collection and/or treatment of the wastes.
«
If the structure has only a toilet such as many of the
public restrooms, recirculating, chemical, or incinerator toilets
could be successfuly used. With the exception of the incinerator
toilet, these methods require facilities for periodical cleaning;
e.g., a portable sewage pump could convey the wastes to a point of
treatment or disposal.
For structures with waste sources other than toilets such as
certain boathouses, some commercial facilities including floating
restaurants, boat supply stores, etc. with sink and bath or shower
29
-------
METHOD I
Macerating
Pump
i sv.'MW.^ w.j. i ss sRc-g
Moorage Collection
Main
Recirculating
Toilet
Portable Sump
Pump-
600 Gal Ion
Holding Tank
METHOD E
MACERATING PUMP AND
RECIRCULATING TOILET APPL.
FIGURE 4
-------
wastes, holding tanks could be used with one of the three toilet
devices mentioned above. The tanks could be sized to retain the
waste for several weeks or longer on the basis of flow quantities
given previously in Table 2. Disinfectant chemicals would be
required to inhibit sewage decomposition and offensive odors.
An installation similar to that illustrated by Method II in
Figure 4 could be used. The estimated cost for holding tanks and
recirculating toilets to accommodate two complete restrooms with
washbasin and shower facilities for a 2-week period would cost
from $700 to $900.
31
-------
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32
-------
V, MOORAGE COLLECTION
This section of the report presents design criteria and cost
estimates for a moorage collection system, including design
capacity, swells, waves, float connections, effects of temperature,
selection of materials, and design of houseboat connections and
lift stations.
A. Collection System
The first step in the planning of a moorage collection system
is the overall plan or system layout in which both present and
future sources of waste must be considered,
The wastes on a houseboat moorage or marina come from a
variety of sources other than houseboats. These include boat-
houses with sanitary facilities, public restrooms, floating
restaurants, snack bars, commercial establishments with sanitary
facilities, and pleasure craft with toilets. Wastes of a
continuous nature require individual connections to the moorage
system. This includes the houseboats, floating restaurants and
snack bars, and other commercial establishments with a continuing
water use. Other intermittent wastes from public restrooms, boat-
houses, and pleasure craft, and certain of the commercial establish-
ments such as boat supply houses, repair shops, etc., may not
require individual, connection to the system but instead, could
utilize holding tanks, recirculating , chemical, or incinerator
toilets.
33
-------
Provisions should be made for any future expansion of the moorage
for houseboat mooring, boathouses, etc. The systems should be designed
with capacity to receive wastes expected during the life of the moorage.
Moorages located on rivers, such as nearly all those in the
State of Oregon, will require pressure collection systems to main-
tain lines above water because of river currents, submerged and
floating trash, and water stage fluctuations. As discussed previously,
each individual connection to the system will require a pump with
adequate capacity to force the waste to a central point for treatment
or further pumping. This may be on the water or on the shore.
In the States of Washington and California, most houseboats
are located on lakes, bays, or other relatively calm bodies of
water with little stage fluctuation. In these situations, gravity
lines under water to a central lift station could be considered as
well as the individual pump units for a pressure system.
1. Design Capacity and Sizes
A sanitary sewer has two main functions: (1) to carry
the peak discharge for which it is designed, and (2) to transport
suspended solids so that deposits in the sewer are kept to a minimum.
The system should be designed to provide scouring velocities
greater than 2.5 fps at least two times a day to prevent corrosive
effects and potential clogging from sludge accumulations.
For moorage pressure systems, the design peak flow will
be dictated by the number of pumps on the system that operate
34
-------
simultaneously, the rate of waste flow to the sump, the pumping
characteristics, and the physical layout of the system. The pipe
should be sized to pass the peak flow at a velocity greater than
2,5 fps but less than 10 fps,
The minimum size pipe, where more than one pump is
connected, is 3 inches. This size is adequate for peak discharge
rates up to 220 gpm. For rates greater than this, a larger
diameter pipe is required.
Appendix B presents design curves to indicate number of
pumps operating simultaneously for 99.9% of the time for multiple
pump systems on the basis of number of pumps connected to the
system, rate of inflow to the pump sump, and pump discharge rate.
For example, a system with 50 pumps connected, a waste discharge
of 100 gallons in an hour, and a pump discharge rate of 60 gpm
would have no more than six pumps operating simultaneously for
99.9% of the time.
2. Swells, Waves, and Float Connections
To allow for unequal movements of one portion of the
moorage walkway relative to the next, caused by swells, waves, or
unequal loadings, lengths of flexible pipe should be used wherever
one walkway joins another. This is illustrated by Figure 5.
The length of flexible pipe should allow for an elevation
difference of 3 to 4 feet between adjoining walkways. There should
also be no sags with the additional length made up in the form of
a horizontal bend.
35
-------
MOORAGE
WALKWAY
FLEXIBLE PIPING
-CLAMPED
CONNECTION
FLEXIBLE PIPING
MOORAGE WALKWAY^
WALKWAY CONNECTIONS
-------
3. Temperature Effects
Provision should be made to prevent freezing of the
lines and to provide for expansion-contraction. The lowest one-
day average temperature noted during 25 years of record at the
U. S. Weather Bureau Portland Airport Station was -3 degrees F on
February 2, 1950. The maximum recorded for this station was
107 degrees F on July 30, 1950.
The minimum temperature value should be used to calcu-
late the amount of insulation necessary. Flexible connections
between separate floats as described above will provide sufficient
allowance for expansion and contraction if connection of the pipe
to the moorage is such that the pipe can move within the connection.
4. Materials
The following materials have been accepted for use on
houseboat moorages by the City of Seattle and would most likely
be acceptable in Oregon and California as well:
a. Hewitt Robbins Flexible Pipes F55, F66*
b. White National Rubber Flexible Pipes CH22A,
CH64A (Neoprene)*
c. Plastic (PVC) 160# Test (Solvent joint or
rubber joint)
d. Cast Iron and Ductile Iron
e. Copper Class L
f. Transite (Water Pressure Type)
*Mention of products and manufacturers is for identification only
and does not imply endorsement by the Federal Water Pollution
Control Administration or the U.S. Department of the Interior.
37
-------
Cost of material, labor for installation, and expected life will all
vary considerabl}1 for these materials. Generally, plastic and cast
iron are the cheaper with flexible pipes the more expensive. Concern-
ing labor costs, flexible and plastic pipes would be cheapest with
cast iron the most expensive; however, cast iron, pipe is the most
durable with plastic possibly the least.
The specific situation, which will vary considerably from
moorage to moorage, will dictate the most economical choice of
material. However, as a rough guide for estimating the cost of
moorage collection systems installed, Figure 6 indicates the cost
per houseboat per foot of moorage length for plastic and cast iron
materials. An example on use of Figure 6 is given later in the
report.
5= Houseboat Connection
A standard form of connection should be adopted by all
morrages because of the mobility of the houseboats. It is suggested
that where above water pressure systems are required, a standard
3"x3" 2-inch Tee or Wye with a 2-inch check valve be provided for
each waste connection,, A 2-inch stub from the check valve should
be provided for a clamped flexible pipe connection to the houseboat
sump. The clamped connection can be designed to provide a point
of failure in the event the houseboat breaks loose from its mooring.
A minimum grade of 0.25 inch per foot should be maintained
between the check valve and the 90 degree elbow on the discharge pipe
of the sump with no sags or low spots in the connection. This method
38
-------
o
z
O
at
O
O
o
o
3
o
TOO
90
SO
70
60
50
40
30
20
10
PVC PLASTIC
10 20 30
NO. Of HOUSftOATS
40
50
MOORAGE COLLECTION COSTS
FIGURE 6
-------
of connection is illustrated by Figure 7 for a centrifugal-type
sump. The same type of connection could be utilized for a pneumatic
system.
B. Moorage Lift Stations
Central lift stations may be used in lieu of high head individual
pumps at moorages that treat their wastes on shore in areas with
water stage fluctuations greater than about 20 feet. If treatment
is provided on the water or where water stage fluctuations are not
as severe with maximum ranges between 10 and 20 feet, it will be
possible to pump directly from the houseboat sump to a treatment
facility or public sewer.
The following design criteria for moorage lift stations are
suggested regarding location, construction, pump capacity, wetwell
design, and estimated costs. An illustration of a typical installation
is also presented.
1. Construction
The station should be located near the shore ramp to mini-
mize piping and to be convenient for maintenance, operation, and
electrical service. It should be firmly secured to the moorage
walkway to reduce damage from float movement and be completely
above water.
Figure 8 suggests a plan which would be applicable at
most moorages. The station is supported by an auxiliary float and
connected to the houseboat line and shore discharge line with flexible
pipe. The shore discharge line could be a tubular hand rail along
the ramp.
40
-------
Moorage Walkwoy
Shore Ramp
Jl
3" Pipe
// Flexible Pipe
/ 3"-C.J,Wye
^Flexible Connection
M
Wet Well
Flexible
Connection
SECTION A-A
MOORAGE LIFT STATION
FIGURE 8
-------
RESTART BUTTON
PUMP SWITCH
OATE VALVE
CLAMPED CONNECTION
SHEAR CONNECTION
2" FLEXIBLE HOSE
2"r«ECK VALVE
3? MAIN WYE CONNECTOR
MOORAGE WALKWAY
FOOD WINDER,
(IF NECESlAftYi
"0X30"
SUMP PUMP
VARABLE DISTANCE L FT.
\
-TV-
Vent to
Roofline
"^7?
^
^
CENTRIFUGAL SUMP
PUMP INSTALLATION
-------
Note that the inlet to the wetwell for the illustrated
station is approximately 6 feet above the houseboat discharge main
and 8^ feet above the maximum water level in the houseboat sump.
With this static head, little or no throttling of the sump pump
would be required. The float should be sufficiently large to
support the weight of the station and provide stability against.
overturning.
2. Capacity
The minimum size discharge line from the pumps is 2 inches
for a macerated or ground sewage and 3 inches for a raw sewage.
Since the velocity of flow in the discharge pipe should be main-
tained between 2.5 and 10 fps, it follows that the pump capacity
for a 2-inch discharge line should be at least 25 gpm at low river
stage and a maximum of 98 gpm at minimum head or high river stage.
For a 3-inch line the minimum is 55 and maximum 220 gpm.
Centrifugal pumps should be able to pass the maximum size
solids expected for the system or severe clogging will result. For
a raw uncomminuted sewage they should have a 3-inch solids handling
capacity. However, solids would not be, a major consideration and
a less expensive pump could be used if the grinder, sump-pump
combination, or toilets with macerator pumps are used.
3. Wetwell Design
Design criteria for construction of wetwelLs are available
in a number of documents and are specified in state regulations.
Essentially the only variable is the volume and this is considered
below.
43
-------
The selection of proper storage capacity is critical
because it affects the time the sewage is retained in the station
and the frequency of operation of the pumping equipment. ASCE
Design Manual No. 37^ ' suggests a wetwell size that, with any
combination of inflow and pumping, the cycle of operation for each
pump will not be less than 5 minutes and the maximum detention time
in the wetwell will not exceed 30 minutes. Based on these criteria,
a pump capacity of 75 to 125 gpm, and a rate of inflow varying from
200 to 900 gpd per houseboat, the following volumes are suggested
for the lift station wetwell serving houseboats.
No. of Capacity
Houseboats Wetwell Storage, Gal.
1 20
2 30
3-7 50
8-15 100
16-30 150
The above figures are for total storage which is composed of the
volume between high and low water levels, the dead storage or
storage below low water, and freeboard volume.
4. Materials
The moorage owner has three alternatives in providing a
lift station. He can purchase the components and fabricate the unit
himself, have it built, or he can purchase a small package lift •
station ready for installation* Possibly with exception of the
small moorages, the prefabricated package unit would be the most
practical approach.
44
-------
There are a number of package units on the market for
both centrifugal and pneumatic systems that would find application
as moorage lift stations. The prices vary significantly depending
on the specific application, equipment needed, and manufacturer
with an estimated price range from $2.500 to $7000» Again, this
is based on pumping uncomminuted sewage„ If the waste is
comminuted or solids removed by an incinerator toilet or other
means, this price range could be reduced,
Additional details can be obtained directly from the
manufacturers or their representatives regarding specific
applications.
45
-------
VI. TREATMENT
Wastes from all sources can be treated individually or on a
group basis. With few exceptions it will be more economical to
treat on a group basis.
Since most floating structures can travel through and/or
reside on various classes of water, a minimum of secondary treat-
ment or connection to a shore sewer is preferable and is generally
required. Connection to shore sewers, wherevfer possible, should
be required to consolidate waste treatment responsibility and
regulatory control.
The remainder of this section discusses available treatment
methods and estimated costs on both an individual and group basis.
A. Individual Methods
Individual treatment should be considered only when the source
is isolated and would cause great expense to connect to a central
system.
1. Macerator-Disinfecter Toilets
This method, as the name implies, macerates and disinfects
the toilet waste before discharge. Operation of the macerator and
addition of the disinfectant solution are generally automatically
triggered by the flushing action of the toilet. These toilets
can be either marine or standard type.
They have been shown''' to effectively reduce coliform
concentrations and provide some measure of organic removals when
47
-------
operated properly. There is sone question, at present unanswered,
as to the bacterial efficiency of these units due to the presence
of sewage solids.
The average cost of these units, based on prices quoted
from three different manufacturers, is approximately $100. Assuming
an installation cost of $50, the total installed cost would be on
the order of $150.
Macerator-disinfecter units have several disadvantages:
a. They do not provide secondary treatment.
b. These units are difficult to police to insure
adequate operation and maintenance.
c. Use on board government vessels has demonstrated
short life and periodic equipment repairs and replacement.
d. They do not significantly reduce solids concen-
trations nor provide a reduction in the degradable organic matter,
and the bactericidal efficiency is questionable, and generally,
unreliable.
e. Treatment is provided only for toilet wastes.
These units have received approval in a number of states
for use on pleasure craft. However, for reasons mentioned above,
they are not recommended for use in the houseboat problem.
2. Incinerator Toilets
These units provide complete gas incineration of toilet
wastes to an inert ash. They use no water for flushing but can
48
-------
handle up to a quart of liquid material. The combustion time is
from 14 to 18 minutes, but the combustion cycle can be interrupted
at any point for subsequent usage of the unit. Combustion vapors
are vented to the atmosphere. Operation is completely automatic
and the toilet becomes nonusable when it is not functioning
properly. They use natural or LP gas and are ignited by 110 volts
AC or a 12-volt DC battery.
The treatment efficiency of these units is complete with
100 percent removal of the sanitary waste. Like the macerator-
disinfecter toilet, though, they provide treatment only for the
toilet wastes or based on figures presented previously, only
33 percent of the total waste volume. Table 5 indicates the
percent of the total household waste represented by the toilet
wastes. This also would represent the percent efficiency of the
incinerator toilets in removal of these parameters. This varies
from a low of 23 percent total phosphate removal to a high of 100
percent NH^-nitrogen removal. While this comparison is at best
a gross one, it does indicate that incinerator toilets do not
provide adequate treatment on a total household waste basis when
secondary treatment is the desired standard.
The first cost of these units, not installed, runs from
$300 to $500 depending on the type purchased and the extra features
desired. There would also be the cost for gas and electricity but
these operating costs are minimal. Installation of these units
could be estimated at approximately $50 to $75.
49
-------
TABLE 5
Comparison of Faces and Urine Waste Quantities to Total
Household Wastes for a Family of 5 People
Parameter
Urine & Feces
Contribution (8)
gm/day
Total Household
Contribution (1)
gm/day
Percent
Urine & Feces
Contribution
of Total
NH3-Nitrogen
Total Nitrogen
Total P04
Grease or Total
Total Solids
62.0
65.0
14.5
Fat 22
360
60
76.5
62.0
30.7
950
100
85
23
71
38
The primary advantages of these devices include: (1) com-
plete removal of fecal and urine wastes, and elimination of most of
the public health hazard from houseboat wastes; (2) low first cost
and operation costs; (3) easy installation and maintenance, and
(4) assured quality control if properly installed since there is
no place for the waste to go if the unit is not operating. Adequate
maintenance and operation are essential.
The primary disadvantages of the units, and it should be
noted that these are undocumented, include: (1) odor problems,
(2) questionable durability under continued long-term usage, and
(3) less than secondary treatment is provided for the total household
waste. Also, a relatively high cost is involved considering the
degree of treatment provided.
50
-------
It is expected that these units may find application on
facilities with only toilet wastes such as certain boathouses, *
public restrooms, and certain commercial establishments or they
may be used for interim treatment.
3. Individual Aerobic Treatment: with Disinfection
This method consists essentially of a tank with 24 hours
retention time, artificial aeration, solids settling and return,
and chlorination of the effluent before discharge. It is a simple
system in principle but like any biological system, sensitive to
proper operation.
There is only one unit presently known .£0 be on the
market suitable for individual application. This varies in size
from 750 gpd to 1,250 gpd.
The efficiency of this unit with proper^installation and
maintenance is on the order of 75 to 85 percent organic removal and
would be acceptable as secondary treatment.
For the individual houseboat the smallest unit is actually
oversized, providing 750-gpd capacity when 200 to 400 gpd would be
sufficient. This would not impair its efficiency but does suggest
the need for a smaller sized unit.
The cost of a 750-gpd unit is approximately $1000 delivered
to Portland, Oregon. To this would be added cost of chlorinator,
flotation, corrosion protection, and installation estimated at
$800, and the total cost would be on the order of $1800.
51
-------
Operation and maintenance of the unit relative to non-
biological forms of treatment are considerably greater both from a
time and money standpoint.
4. Shore Treatment
If the wastewater from the individual houseboat is pumped
to shore for treatment, there are two alternatives. These include
connection to a public sewer or to a septic tank with absorption
field, provided soil conditions permit. Other methods such as hold-
ing tanks and extended aeration units are cheaper to use on the
water.
Each of these alternatives has been investigated and it
appears that the most practical is to pump the wastes to a public
sewer. This would cost approximately $800 to $1000. If no public
sewer is available, the next approach would be to pump the wastes to
a septic tank with absorption field or seepage pit on shore. The
area required for the field or pit can be determined from Table 6.
It is estimated that a system such as this would cost on the order
of $1100, installed. If land is unavailable or if soil characteristics
do not permit the use of an absorption field, an extended aeration
type plant would be necessary for treatment on the water (a shore-
based facility would be more expensive than providing a floating unit).
B. Group Methods
In instances where connection to a public sewer cannot be made,
moorages and houseboat owners will have to provide their own treatment,
52
-------
The alternative process discussed here meet State requirements.
They include a floating or shore-based extended aeration unit or
a settling unit with chlorination to be replaced by sewer connection
or secondary process at some designated date in the future. Each
of these methods with illustrated applications is presented.
TABLE 6
Soil Absorption Areas Required for Single Houseboats
for Various Percolation Rates(l)
Percolation
Rate
min.
1 or less
2
3
4
5
10
15
30 W
Absorption Area'^)
Using Recirculating
Toilet, ft.
20
30
35
40
45
65
80
115
Absorption Area'^)
For Total Houseboat Waste
ft.2
45
70
80
90
100
150
180
260
(1) Table based on allowable sewage loadings presented in Manual of
Septic Tank Practice, U.S.P.H.S., No. 562, 1957.
(2) Based on flow of 100 gpd per houseboat
(3) Based on flow of 225 gpd per houseboat
(4) Not suitable for seepage pit
53
-------
!„ Extended Aeration
Packaged extended aeration units are available from a
number of manufacturers in a size range suitable for a moorage
treatment system. Information on facilities which can be modified
at a reasonable cost for flotation if desired, can best be obtained
through direct contact with a manufacturer.
Figure 9 illustrates the estimated installed costs of a
floating extended aeration treatment facility for various sized
moorages on a per houseboat basis. The cost per houseboat decreases
significantly as the size of moorage or number of houseboats served
increases. For example, the cost per houseboat for serving one
houseboat is $1800 while the cost per houseboat for serving 50
houseboats is $200. This curve is based on typical prices for a
floating treatment facility. The cost for a unit installed on shore
would be less and would be recommended in areas with pumping heads
on the order of 10 to 20 feet. In high head areas such as the
Portland, Oregon, area, it would be more economical to float the
treatment facility with the moorage.
The major disadvantage to the packaged extended aeration
unit is the degree of competence required for efficient operation.
Like any biological system it is sensitive to a number of parameters
and unless these are understood by the operator, changes can upset
the balance in operation considerably„ Also, the annual costs of
operation are high due to power requirements, and maintenance labor.
54
-------
!2,OOQr
! 1,506
UJ
(O
3
O
X
K
bl
0.
8
!l,000
FIRST COST INSTALLED WITH
CHLORINATION AND FLOTATION
10 20 30 40
NO. OF HOUSEBOATS SERVED
50
EXTENDED AERATION
TREATMENT COSTS
FIGURE 9
-------
If these units are used, it is recommended that a service
agreement from the manufacturer or other reputable servicing firm
be obtained.
Figures 10 and 11 illustrate typical examples of how and
where floating extended aeration facilities could be used.
2. Settling Tank and Chlorination
This method of treatment will not provide the degree of
efficiency normally required but might be adequate as the first
step in a stage treatment scheme which would lead to secondary
treatment.
For the raw houseboat waste, the process would include a
settling tank constructed with a sludge draw off standpipe. The
effluent would be chlorinated before discharge.
The settling tank should be designed on the basis of less
2
than 600 gpd/ft of surface area and provide a minimum of 2 hours
retention of the design flow. The design flow should be the 16-hour
daily average or 95 gpcd. The bottom of the tank should be sloped
at least 2:1 to the sludge draw off pit, and the chlorine contact
chamber should provide a 15 minute contact time on the basis of the
design flow. If recirculating or incineration toilets are used on
the houseboats, the design flow can be reduced to 70 gpcd and if no
laundry facilities are permitted it can be further reduced to 50 gpcd.
Figure 12 illustrates a typical design which utilizes a
500 gallon septic tank modified as shown, a 55-gallon barrel with
portable chlorinator, all supported by a wood float over styrofoam
56
-------
uu
o:
o
LJ
K- S
z <
< u
p
bit*
*s
ifE
§1
cc
_i o
U. U
-------
u.
tf)
oc
i
u.
-------
SCUM .BAFFLE
CHLORINE
CONTACT
CHAMBER
SETTLING
TANK
2 DISCHARGE
PIPE
4'-6"
-3 SLUDGE D^AWOFF TO
COMMERCIAL SEPTIC
TANK PUMPER
2"GATE
VALVE
SETTLING TANK ft
CHLORINATION TREATMENT
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cylinders. All metal surfaces would be covered with an asphalt,
epoxy, or other approved coating. This design uses standard, off-
the-shelf equipment and could be fabricated, excluding labor, for
approximately $500 to $700. It would be sufficient in size to
handle up to 35 houseboats using recirculating toilets. Without
recirculating toilets, 25 houseboats could be connected. This
unit could later be salvaged for use in construction of a lift
station when sewers become available. The use of plastic or
fiberglass materials for the settling tank and contact chamber
could be weight saving. The cost of this material would be some-
what higher but this may be off-set by savings in float requirements
and installation time.
60
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VII. EXAMPLE DESIGN
The following design is presented to illustrate method of
design, equipment application, alternatives for treatment, and
cost estimates. It should be emphasized that these costs are
only estimates and could change significantly with different
equipment and labor costs.
In the design of this system, three alternatives are
considered:
1. Centrifugal pumps at each houseboat that pump to a
central lift station on the moorage which in turn lifts the
waste to a Portland city sewer.
2. Centrifugal pumps at each houseboat with capacity
to pump directly to shore to a Portland city sewer.
3. Pneumatic ejectors at each houseboat that pump to
a floating package plant.
Each alternative is discussed below. The basic scheme for
the system design in plan and profile is shown on Figure 13.
A. Basic Design Criteria
The moorage is assumed to accommodate 18 houseboats with no
future expansion considered. A total of 35 people live on the
houseboats.
The average 24-hour flow is 75 gpcd, and the average 16-hour
flow is 95 gpcd. The maximum rate of waste flow expected from a
houseboat is 50 gallons in an hour.
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PORTLAND CITY SEWER
MANHOLE SMH INV EL 31.9-
FLOATINO LIFT STATION
LOCATED ALONG MOORAOE
WALKWAY
MAX WS EL. 26.8
MEAN WSEL.&9
MIN.Wt EL.0.0
4"FORCE MAIN, ATTACHED TO
MOORAQE WALKWAY
NOTE: ELEVATIONS ON DATUM 1.95FT. ABOVE
M.S.Li PIPING LAVED LENGTHS
BASED ON AERIAL PHOTOS »ELEV.
DIFFERENCES
EXISTING PORTLAND CITY
SEWER-MH. S.E.I84
AIR
STATION
AIR LINE X
FLEXIBLE CONNECTION
COLLECTION MAIN
325'
BAFFLE BOX
FLOATING LIFT STATION OR(CENTRIFUGAL OR
PNEUMATlOFLOATING PACKAGE TREATMENT
PLANT.
4V
260'
: HOUSEBOATS WILL DISCHARGE WASTE
INTO COLLECTION MAIN BY PUMPING
WILLAMETTE RIVER
SYSTEM DESIGN
FIGURE 13
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The average organic loading per person is CL25 pound of 5-
da.y biochemical oxygen demand (BOD) per day on the basis of data
presented in Table I.,
A minimum velocity of 2 ,,5 fps and a maximum velocity of 10
fps will, be used to size the force mains.
A wetwell capacity of 1.50 gallons will be used as indicated
B. Layout and Cost. Estimates
Each of the three alternatives is discussed in two schedules
on the basis of financial responsibility—that of the houseboat
owner and that of the moorage owner. Cost estimates are given for
each alternative,
1 , Alternate A
This alternate calls for houseboat plumbing, centrifugal
pumps at each houseboat, a moorage collection system, a lift station,
and a discharge force main with baffle box for connection to a city
sewer „
a0 Schedule_l
This schedule is composed of plumbing, provision of
houseboat pump units, and connection to the moorage system. It
will be the responsibility of the houseboat owner.
Houseboats were assumed to be plumbed with copper
materials by a licensed plumber in accordance with the plan presented
by Figure 2,
63
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Packaged submersible centrifugal pumps in 18"x30"
cast iron sumps were used at each houseboat and attached in a manner
similar to that illustrated by Figure 3.
The grinder mechanism for macerating sewage solids
was not considered necessary as the total lift between the high
water level in the sump and the discharge point to the wetwell was
in excess of 5 feet which is the minimum operating head for the pump.
The normal operating range of the houseboat pumps
would vary, depending on the number of pumps operating simultaneously,
from 110 to 90 gpm. The corresponding maximum flow in the collection
system which may be exceeded 0.1 percent of the time, would be 270 gpm.
Each houseboat pump unit will be connected to the
moorage system with a length of 2-inch flexible hose of a type
mentioned previously. The hose will be clamped on both ends with
sufficient strength to hold under normal stresses but such that it
will fail first in the event the houseboat breaks from its mooring.
Estimated costs for plumbing and the pump units are
based on figures reported previously, plumbing at $560 per houseboat
and the pump units including installation at $325 per houseboat.
The cost for making the moorage connection is estimated at $50 per
houseboat. The total first cost then to each houseboat owner would
be $935.
b. Schedule 2
This schedule includes the moorage collection system,
the lift station, and the shore discharge line with baffle box. It
64
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would be the responsibility of the moorage owner to provide this
system*
The moorage collection systeir to the wetwell of the
lift station was designed of 3-inch Schedule ^.0 PVC pipe. This
size pipe requires an average flow of 55 gpn? and is adequate, for
flows up to 240 gpm« The peak flow would actually be 270 gpm but
the difference was not considered significant enough to warrant
the. use of 4-inch pipe. The line, is supported at 5 foot intervals
with devices that allow the pipe to contract and expand» A. 5-foot
long, 3-inch flexible hose connection was made every 100 feet and/or
at every walkway division, A standard connection with 3"x3"x2"
tees and a 2-inch check valve was provided for every houseboat.
Insulation of the pipe was not considered necessary on the basis
of heat transfer calculations for extreme temperatures. The
weight of the collection system is less than 2 pounds per foot and
no additional flotation was considered necessary.
A package lift station built in accordance with
State requirements was selected with dual nonclog sewage pumps.
To reduce head loss and pump capacity, a. 4-inch .PVC Schedule 40
discharge line was used. Pumps with a capacity of 100 gpm at a
head of 50 feet were satisfactory for use in the lift station,,
It was calculated that the station would support
itself with no additional buoyancy at a depth of 3.5 feet when
empty. The auxiliary float was designed only to support the
weight of sewage in the wetwell before pumping and the, weight of
65:
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two men. The float will also give the station stability against
overturning.
The force main from the lift station to the shore
sewer is of 4-inch Schedule 40 FVC pipe,, The shore connection is
similar to that indicated by Figure 8 with a 5-foot length of 4-
inch flexible hose connecting the lift station to 4-inch PVC pipe
attached to the. 60-foot, long ramp, A 10-foot length of 4-inch
flexible hose is used to connect the shore side of the ramp to the
4-inch PVC main on shore. The line on shore is laid in trench and
backfilled. A baffle box is used to dissipate the velocity head
before discharge to the sewer manhole.
The estimated cost of the moorage collection system
is based on data presented in Figure 6 for the PVC system. This
cost, for 18 houseboats, is $0,138 per houseboat per foot of
moorage length. For the example moorage with a total length of
680 feet to the lift station the cost would be $1700.
The lift station cost with auxiliary float is
estimated at $3600 installed. This cost is based on typical
material and labor costs for the Portland, Oregon, area.
The discharge force main of 4-inch PVC Schedule 40
pipe with an energy dissipating baffle box is estimated to cost
$1500 for materials and $700 for labor for a total cost of $2200.
The total cost to the moorage owner for Alternate A
is $7500.
66
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2 „ Alternate B
This alternate calls for individual, centrifugal pumps
at each houseboat with capacity to pump directly through a moorage
system to a shore sewer,
a „ Scheduj,e_j_
Under this schedule are the houseboat plumbing and
the individual, pump units,
Plumbing would be the same as discussed previously
and the estimated cost would be $560 per houseboat.
Each pump unit to pump ashore will require capacity
to pump against a 51,9 foot head plus system losses. To minimize
head losses and reduce the pump size, a 4-inch collection system
is required, With a 4-inch collection system and discharge main,
a 1-hp pump with a capacity of 100 gpm at a head of 50 feet can
be used. Each unit would be connected as discussed previously.
The estimated cost for each pump unit is $950,
installed, plus an additional $50 for the moorage connection.
The total cost for each houseboat would be $1560 for this alternate.
bo Schedule 2
This schedule would be the same as that discussed
under Schedule 1 with the exception that a lift station would not
be required and a 4-inch collection system would be required rather
than a 3-inch system, The total estimated cost to the moorage
owner for this schedule would be $4600, installed.
67
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3. Alternate C
This alternate calls for pneumatic ejectors at each house-
boat that pump to a central floating treatment plant.
a. Schedule 1
Plumbing is the same as discussed earlier with an
estimated cost of $560 per houseboat.
The pneumatic ejector units are complete packaged
units sized for an individual household. The total pumping head is
less than 10 feet and a low pressure ejector is utilized. The
estimated cost for the ejector is $800 installed. There would be
an additional charge of $50 for the connection to the moorage system.
The total cost to the houseboat owner for this schedule
is $1410.
b. Schedule 2
For this alternate the moorage owner would have to
provide a moorage collection system and a floating treatment facility.
The moorage collection system would be the same as
that discussed under Schedule 2, Alternate A, with an estimated
cost of $1700.
The cost for the floating treatment facility was
estimated on the basis of data provided in Figure 9. This estimates
a cost of $7000 or $390 per houseboat.
The total cost to the moorage owner for Alternate C
is $8700.
4. Summary
Costs for the three alternatives are summarized in Table 7.
68
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Alternate A is the least expensive method for the houseboat owner
but involves a greater cost for the moorage owner. Centrifugal
pumps, with their inherent difficulties in pumping raw sewage
are also a disadvantage, Alternate B is the least expensive for
the moorage owner but the most expensive for the houseboat owner.
It also involves the use of centrifugal pumps for raw sewage and
large expensive pump installations at each houseboat. Alternate C
is expensive for both the houseboat owners and the. moorage owners.
Pneumatic ejectors, though, would provide dependable none log
service and possibly in the long run be more economical.
The floating treatment facility on the other hand may
prove to be much more expensive than the first cost indicates
because of annual operation and maintenance, costs.
It should also be remembered that the costs presented in
Table 7 do not represent annual costs but simply the first cost
for capital investment. Annual operation, maintenance, replacement,
and financing costs may present an entirely different outlook and
should be considered before deciding on any one method.
TABLE 1
COST SUMMARY
Schedule Alternate A Alternate B Alternate C
1--Houseboat Cost
Plumbing $ 560 $ 560 $ 560
Sump, pump & connection 375 1000 850
TOTAL COSTS $ 935 $ 1560 $ 1410
2--Moorage Cost
Collection System $ 1700 $ 2400 $ 1700
Lift Station 3600
Force Main & Baffle Box 2200 2200
Floating Treatment - - 7000
TOTAL COSTS $ 7500 $ 4600 $ 8700
69
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VIII. BIBLIOGRAPHY
1. Watson, K. S., Farrell, R. P,, and Anderson, J. S „ "The
Contribution from the Individual Home to the Sewer
System." Paper presented before annual WPCF Meeting,
September 1966,,
2. Manual of Septic Tank Practices. Public Health Service
Publication No. 526, 1957.
3. "The Effect of Industrial Wastes on Sewage Treatment." New
England Interstate Water Pollution Control Commission,
June 1965.
4. Babbitt, R. E. Sewerage and Sewerage Treatment., 6th ed.
John Wiley and Sons, Inc., 1949„
5. Pierce, J. W. "Plastic Pipe—A Progress Report/1 Civil
Engineering, ASCE, February 1967.
6. Design and Construction of Sanitary and Stcjrm Sewers. ASCE
Manual of Practice No. 37, 1960.
7. "Evaluation of Marine Toilet Chlorinator Units." by Syracuse
University Research Corporation for New York State
Health Department. Report No, 9, May 1962.
8. Sunderman, F. W. and Bociner, F. "Nutritional Values in
Clinical Medicine." p. 260. W. B, Saunders and Co,,
1959.
9. Personal communication with Dr. Donald Guthrie, Associate
Professor of Mathematics at Oregon State University,
Corvallis, Oregon.
10. Cox, D. R. and Smith, W. L. Queues. John Wiley and Sons,
Inc., 1961.
71
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IX. APPEND IK
-------
APPENDIX A
Plumbing Costs for Three Houseboats in
Seattle, Washington
-------
UNIVERSITY PLUMBING 6- HEATING CO.
CONTRACTOR*
iaiTVWAVN.fi • 9. O. • O X •• • PMQMC
• CATTLE, WABHINOTON 9B1OB
•OLD TO
Terry Pattut
2039 Falrvlaw Ave. East
Saa-HU. Washington 98102
-46-
CAIN Upon COWUTIM «r w«««
f. a. NO.
2339 PalrvlM Ay*, b.
Rorough waitat, vwitt and watar for houcaboat
9/14 9/21
Wtlaman
Paterton
II
7
IQTAI >
-------
UNIVERSITY PLUMBING 6- HEATING CO. |
CO NTHACTORS
BCATTLE. WASH INOTON 9B1OS
DAT!
October 11,
•OLD TO .
Dan Brackett
.2818 Boyer East
Seattle, Washington
-1»-
Timid C««H UMK coupumoM OF wonn 0ur JOB NO. |9|9
Rcrough wastes, vonts and »at«r for hous* boat
LABOR 9/14 RATE TOTAL
Kattleman 16 7.30 131.40
Labor
Material
Porni It
Overhead I5£
Foe 10*
Sales Tax
P. O. NO.
131.40
191.57
3.75
326.72
49.01
375.73
37.57
413.30
17.36
430.66
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UNIVERSITY PLUMBING 6- HEATING CO.
CONTRACTOR*
• CATTLE, WA1MINOTON ••IDS
Simons
KH.OTO . 281 A Boynr Avenue Ea§t
Seattle, Washington 96108
DAT. October 7
.ie«?_
'. • run* C*«H un» eemunm or won Our
Rough In
LABOR Q/21,
Kettleman 7
Petereon 7
MB NO. 2047
aia TOTAL BAJK
U 84 7.30
II 6* 7.30
Labor
Material
Perwlt
Overhead 15*
Fee 10*
Sales Tax
9. O. MO.
TOTAL
60.23
60.23
'20.46
172.17
3.00
295.63
44.34
339.97
34.00
375757
389768
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APPENDIX B
Design Curves for Multiple
Pump Systems
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DESIGN CRITERIA FOR MULTIPLE PUMP SYSTEMS
Moorage collection systems with a number of pumps connected
in parallel should have adequate capacity for the maximum probable
number of pumps operating simultaneously. To determine the
probable maximum number for various size moorages, queuing theory
was employed to relate pertinent design parameters which include:
1. Number of pumps connected to system.
2. System head characteristics.
3. Rate of sewage inflow.
4. Pump head-capacity characteristics.
5. Rate of pumping.
A relationship developed by Guthrie^'and Cox' ' for
indicating the proportion of time or probability that any number
of pumps in various sized systems operate simultaneously is given
by equation 1.
Pj - P0rj (D
where
rj • 1 for j»o
and
™ JJ for 1*- j *N (3)
( j! (o) )
N = number of pumps connected to the system
I • rate of inflow to the pump sump, gallons per minutes (gpm)
0 - pumping rate, gpm
81
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Pj * proportion of time or probability that j pumps are
in operation where j varies fron o N
For general use a family of curves was prepared for Pj by vary-
ing the number of pumps connected to the system from 0 to 50, the
rate of inflow from 50 gallons per hour (gph) to 200 gph and the
pumping rate from 120 to 30 gpm, These curves are given in Figures
14 and 15. The indicated number of pumps operating simultaneously
would cover over 99.9 percent of the time; i.e., there would be a
0.1 percent chance that the indicated number of pumps operating
would be exceeded.
It should be remembered when using the curves that the average
24-hour houseboat waste flow is less than 200 gallons and the
average pumping rate would be on the order of 60 to 100 gpm.
82
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INFLOW RATE - 50 GPH
2
c
II
I i
10
9
8
7
6
5
4
3
2
I
0
30GPM
40GPM
606PM
1206PM
I
I
10 15 20 25 30 35 40
Number of Pumps Connected to System
45 50
INFLOW RATE = 100 GPH
Q- -3
*o
-------
INFLOW RATE * 150 GPH
I!
"5
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