4940.3 Rev-1

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CS100 OBJECTIVE

The objective of these Minimum Design Standards is to

provide each living unit with a water-carried sewerage

system adequate to collect, treat and dispose of wastewater

in a manner which will not create nuisances or endanger the

public health or the environment.

CS200 GENERAL ACCEPTABILITY

CS201 LOCAL CODES AND REGULATIONS

CS201-1 The minimum standards set forth herein have been

established to accomplish certain basic HUD-FHA objectives

and shall not be construed as relieving developers or builders

of responsibility for compliance with local ordinances, codes

and regulations, including established requirements of the

U.S. Environmental Protection Agency or its delegated

regulatory agency. To the extent that local, state, or Federal

requirements exist which are more stringent than these

Minimum Design Standards, the more stringent standard shall

apply for insuring purposes.

CS201-2 HUD-FHA does not assume the responsibility for enforcing or

determining compliance with local codes or regulations or

making interpretations regarding their application in any

specific instance.

CS201-3 HUD-FHA approval of all wastewater systems is contingent

upon approval from the U.S. Environmental Protection

Agency or its delegated regulatory agency for the system,

including discharge permit where applicable. (See Section

CS302.)

CS201-4 Where the local codes, regulations or permits provide for less

stringent standards than are required herein, these Minimum

Design Standards shall apply. In the event the local codes,

regulations or other requirements preclude compliance with

these standards, the property will be ineligible unless the

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Page 1

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4940.3 Rev-1

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stated objectives set forth herein are fully attained by an

approved alternative means.

CS202 REVISIONS TO APPROVED PLANS

Any deviations from the approved plans or specifications

must be approved in writing by the appropriate Field Office

before such changes are undertaken. A request for such

approval shall be accompanied by written evidence that the

proposed changes are acceptable to the U.S. Environmental

Protection Agency or their delegated regulatory agency, and

any other state or local authority having jurisdiction. The

request shall also be accompanied by a supplementary

engineer\'s report describing the changes and the reasons for

them.

CS203 DESIGN PERIOD

Sewerage systems shall be designed to provide adequate

service for the economic life of all the residences to be

served.

CS204 AREA TO BE SERVED

The initial plans and specifications shall provide for a

sewerage system adequate to serve all prospective

connections where all the properties proposed for

development are to be completed on a continuous

construction schedule.

CS205 STAGED CONSTRUCTION

Construction of sewerage systems in stages will be

considered where the entire development is to be completed

as a series of individual sections or groups of properties

according to a development plan but not necessarily on a

continuous schedule. Where staged construction is

proposed, the original design plans and specifications shall

provide for collection and treatment facilities adequate to

serve the properties to be included in each development

stage. The sub-trunk and trunk sewers shall be adequately

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4940.3 Rev-1

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designed to handle the flow from sewer lines to serve the

properties to be developed in all future stages of residential

construction. A proposal for staged development shall be

described in detail in the engineer\'s design development

report (DDR).

CS300 SUBMISSION OF EXHIBITS

CS301 FEASIBILITY STAGE

Prior to the preparation of detailed engineering plans and

specifications or any engineering reports, it is recommended

that the project be discussed with the appropriate Field

Office and the HUD-FHA Environmental Engineer or

Construction Analyst. During this initial feasibility-stage,

the field office representative and/or the HUD-FHA

Environmental Engineer will offer an informal opinion as to the

general feasibility of the project. The purpose of this

informal opinion is to avoid unnecessary expense associated

with the planning and design requirements contained in

subsequent stages for projects which are clearly not feasible.

However, importantly, a favorable opinion during this stage

DOES NOT indicate or imply in any way approval of the project.

Formal and final project approval will be provided as set forth

in subsequent stages below. Note: A general location map of

the area (a printed topographic quadrangle or United States

Army map where available) with the location of the

development shown thereon should be provided during this

feasibility stage.

CS302 PRELIMINARY PLANNING STAGE

Prior to the preparation of detailed engineering plans and

specifications, the submission of an engineering Design

Development Report (DDR) giving the basic data on which

the design of the system is to be developed is required. This

report shall include information on the proposed size of the

sewer pipes in the collection system; the type and capacity

of the sewage treatment plant proposed; the point of final

disposal of the sewage treatment plant effluent; and approval

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4940.3 Rev-1

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of the DDR from the U.S. Environmental Protection Agency,

its delegated regulatory agency and/or other authority having

jurisdiction over such matters, indicating that the degree of

treatment and point of final disposal for the effluent will be

suitable as to location and will be acceptable for the

development under consideration.

Information concerning the structure of the organization

which will own and operate the system and the means by

which continuous satisfactory operation and maintenance of

the system at reasonable cost is also required during the

preliminary planning stage. It is essential during this stage

to demonstrate that the proposed organizational structure will

provide for continuous satisfactory operation and

maintenance of the system at reasonable rates. In those

instances where this assurance cannot be clearly

demonstrated, HUD-FHA may require a trust indenture from

a responsible public entity to operate the system in the event

of default, or, HUD-FHA may refuse approval of the project.

Please refer to HUD Handbook 4075.12 REV. All facility

planning and preliminary designs must be in accordance with

all Federal, state and local National Environmental Policy Act

requirements.

CS303 FINAL PLANNING AND DESIGN STAGE

CS303-1 Once the DDR required in the preliminary planning stage has

been approved by HUD, the final planning and design stage

may be commenced. Not less than the following exhibits are

required during this stage for submission:

A. A final engineering report containing detailed and

specific information from which the design of the

system was developed, where such data varies from or

was not included in the original DDR.

B. Detailed engineering plans bearing the seal of a

professional engineer registered in the state where the

improvements are proposed.

C. Detailed specifications.

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4940.3 Rev-1

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CS303-2 The following specific data shall be included in the exhibits

described above:

A. Volume and strength of domestic sewage flow used in

the design. (See CS603). Estimates will be acceptable

for new systems. For extensions to existing systems

actual flow and strength determinations shall be

required. Details of the method used to determine

ground water infiltration shall be included where it is

appropriate. Actual measurements of flow are required

where feasible and practical for extensions to existing

systems to determine minimum, average, and

maximum flow conditions. Strength determinations of

sewage for existing systems should be based on

reports of laboratory analyses of composite samples

taken over a continuous 24-hour period.

B. An indication as to whether garbage disposals

(\"grinders\") are being or will be used in the residential

units being served.

C. Existing Sewers - A discussion of the nature, location,

extent and construction features of existing sewers

that would be used to accommodate the proposed

work. Submit technical data as evidence that existing

sub-trunk, trunk or outfall sewers are adequate in

capacity and structural quality to handle the proposed

sewage flows.

D. Geotechnical Report - Unless it can be shown through

prior studies, soil maps or common knowledge that soil

and groundwater conditions are not adverse or

unusual, every project shall have an accompanying

geotechnical report. The project geotechnical report

shall address all the issues for which such information

is necessary or desirable in order to make sound

engineering decisions. Soil bearing pressures shall be

provided for heavy structures. Depth to rock and

groundwater shall be provided for construction beneath

the surface in areas which rock or groundwater may be

an issue during construction. Soil permeabilities shall

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Page 5

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4940.3 Rev-1

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be identified for holding pond projects which employ

earthen liners. Swampy areas and expansive clay

areas shall be delineated. Additionally, for each

geotechnical issue identified as being unusual or

requiring special attention, the geotechnical report shall

provide recommended geotechnical solutions.

E. Water Supply - Where adverse impact on local water

supplies is possible as a result of the project, the

following information shall be provided: A discussion of

the location of wells or surface water supply intakes,

treatment plants, reservoirs, or other structures of

public health significance with relation to various parts

of the sewerage system. Report the minimum,

maximum, and average annual daily consumption of all

existing water systems within close proximity of the

project area.

F. Receiving Stream - Where final disposal of sewage is

to a receiving stream, indicate the stream and point of

discharge on a map of the area. Describe the

characteristics of the stream and give the recorded or,

if necessary, the estimated minimum and average

annual daily flow. Give the highest known highwater

marks, in relation to the elevation of the trunk sewer

outfall and the flow line of various components of the

sewage treatment plant. Any unusual flow

characteristics or use of the stream (e.g., \"trout

stream\") should also be discussed. If a lake is used for

this purpose, include such pertinent information as the

surface area, location, depth near the outlet, average

rate of inflow and state any other purposes for which

the lake is used (e.g., water supply, recreation, fishing,

etc.).

G. Design Data - Include all design criteria and

assumptions used to determine the total flow for which

each line in the collection system and the outfall sewer

is designed. The computations for determining the

diameter and related flow characteristics should be

included. Likewise, the criteria and computations used

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4940.3 Rev-1

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in developing the design of all sewage treatment plant

units and pumping stations should be shown. Also,

discuss the reasons for using the type of treatment

proposed and the degree of treatment that can be

expected from the processes to be utilized.

The use of \"packaged\" and \"proprietary\" (Brand name)

pumping, transport and/or wastewater treatment

equipment is acceptable. Packaged and proprietary

systems shall conform to all the applicable

requirements contained in this Handbook. In all

instances where \"packaged\" or \"proprietary\" systems

are proposed, the following shall be demonstrated:

1\. The existence of a unit of similar type which has

been in successful operation for twenty years or

more, or

2\. The existence of two units of similar type which

have been in successful operation for two years

or more.

In considering whether a particular unit has been in

\"successful operation\", the following factors shall be

considered:

1\. Operating performance

2\. Reliability

3\. Maintenance requirements.

4\. Operating efficiency

5\. General durability of all components including

coatings and corrosion protection

If staged construction is contemplated, the design

exhibits and computations should cover the complete

system clearly indicating each stage of construction

and the properties to be served during each stage.

H. A topographic location map of the land on which the

system is to be constructed including the treatment

plant site shall be provided. A USGS \"Quad\" map

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Page 7

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4940.3 Rev-1

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(1\" = 200\'; 20\' contour interval) is adequate for this

purpose.

I. Complete working drawings of the system including:

plans, profiles, and details of the sewage collection

system and appurtenances.

J. Details of pumping stations including pump installation,

electrical and piping details. Include force main details

when used. It is recommended that all pumping

station submittals include the following information:

1\. TDH, NPSH Calculations

2\. Static Head

3\. Pump Curves from Manufacturer

4\. System Curve(s)

5\. Head Curve(s)

6\. Wet Well Volume

7\. Cycle Time

8\. Pump Station Friction Losses

9\. Buoyancy Calculations

10\. Force Main Friction Losses

11\. Force Main Diameter and Length

12\. Force Main Material Type

13\. Elevation and Plan View of Force Main/Pump

Station

K. Details of the treatment plant construction showing the

location and dimension of all inlet and outlet structures,

weirs, orifices, etc., including a complete hydraulic

profile showing liquid surface elevations at average and

peak daily flows.

L. Details of the structural design of all structures

included in the system as follows:

1\. Live and dead loads for floors and roofs.

2\. Elevation of the overflow or liquid level of all

tank structures.

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4940.3 Rev-1

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3\. A description of the sub-soil at the site of all

major structures as determined by test borings

and exploration pits. The data should include the

type and nature of the soil from the original

ground surface to a depth below foundation level

equal to the diameter or width of the structure.

It should also include the \"N\" values or number

of blows per foot in the standard penetration test

(ASTM D 1586). The Unified Soils Classification

System is recommended for use in describing the

soil. Actual as well as recommended maximum

soil-bearing values shall be provided for all major

structures.

4\. The steel stress for ring tension in reinforcing

used in the design of cylindrical tank structures.

5\. The compressive strength of concrete used in

the design.

6\. Structural design assumptions and computations

used in the design of the major structures.

7\. Gross weight of machinery - or equipment

supported by all major structures.

8\. The maximum elevation of seasonal and average

ground water table.

9\. The thickness of concrete covering for

reinforcing steel.

M. A plan showing the location of treatment facilities with

particular reference to the location of existing or

proposed residences. A minimum scale of 1\" = 200\'

shall be used. A 100 foot buffer area shall be shown

as required in Section CS601. Additionally, the plan

shall show the closest distance between any residential

structure and any wastewater treatment system units.

(See Section CS601.)

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4940.3 Rev-1

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N. Specifications covering quality, kind and grade of all

materials, equipment, construction, workmanship, and

methods of assembly and installation.

O. Approval from the U.S. Environmental Protection

Agency or its delegated regulatory agency of the

design of the system and land disturbing activities as

described by these exhibits. Where local laws or

regulations require approval prior to construction by an

organization other than those noted, (such as local

governmental agencies, etc.,) such approvals shall also

be submitted. The EPA or its delegated regulatory

agency may require pollution prevention plans and

storm water discharge permit under the National

Pollutant Discharge Elimination Permit System (NPDES)

for all construction activities that disturb five acres or

more in total land area.

P. Complete details of the organizational structure for

ownership and operation of the system including final

drafts of all legal documents required.

Q. Proof that all necessary property rights for the project

have been obtained or are readily obtainable.

CS304 CONSTRUCTION STAGE

Prior to the commencement of any construction on the

project, the approval by HUD shall be obtained with regard to

all the items contained in Section CS303, above. Prior to

HUD\'s acceptance of any properties associated with the

project, it shall be determined that the completed

construction is acceptable. Not less than the following

exhibits are required for this determination:

A. Written evidence that the system as constructed has

been approved by the authorities having jurisdiction, if

such approval is customary or required.

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4940.3 Rev-1

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B. A written statement from the design engineer that the

system has been constructed in accordance with the

approved plans and specifications.

C. Evidence that an acceptable organization for assuring

continuity of satisfactory service has been established

and is functioning or completely prepared to commence

operations.

D. Documentation showing that all property deeds,

easements, encroachments, etc., necessary for the

project have been obtained.

CS400 SEWAGE COLLECTION SYSTEMS

CS401 GENERAL

New collection systems and extensions to existing systems

shall not be designed for a combined stormwater/sanitary

system. Except under unusual circumstances, the use of the

sewers will be limited to the collection of sanitary (domestic)

sewage, ground water infiltration (within allowable limits) and

wastes from commercial establishments provided for the

convenience of the property owners to be served by the

system.

CS402 MATERIALS

All materials to be used shall be described in the

specifications. Materials and appurtenances shall be of first

quality, free of defects and suitable to accomplish the stated

objectives for community sewerage systems.

CS402-1 Sewer Pipe

Concrete, ductile iron; high density polyethylene (HDPE) and

polyvinyl chloride (PVC) are acceptable materials. Sewer

pipe and fittings shall conform to currently dated standards

of the American Society for Testing Materials (ASTM);

American Standards Association (ASA); American Water

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4940.3 Rev-1

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Works Association (AWWA); American National Standards

Institute (ANSI); or General Services Administration (Federal

Specifications), for the type of pipe suitable for the use

intended.

CS402-1.1 The applicable specifications include:

A. Concrete

ASTM C76 - Reinforced Concrete Culvert,

Storm Drain and Sewer Pipe.

ASTM C361 - Reinforced Concrete Low-Head

Pressure Pipe.

Federal Specification SS-P-375 - Pipe, Concrete,

Reinforced Sewer

Reinforced Concrete Federal Specification - SS-P-381

\- Pipe, Pressure Reinforced Concrete, Pretensioned

Reinforcement (Steel Cylinder Type).

AWWA C300 - Standard Specifications for

Reinforced Concrete Water Pipe

Steel Cylinder Type, Not

Prestressed.

AWWA C301 - Standard Specifications for

Reinforced Concrete Water Pipe

Steel Cylinder Type, Prestressed.

AWWA C302 - Standard Specifications for

Reinforced Concrete Water Pipe

Non-Cylinder Type, Not

Prestressed.

B. Ductile Iron

AWWA C151/ - Ductile Iron Centrifugally Cast In

ANSI A21.51 Metal Molds or Sand-Lined Molds

for Water or Other Liquids.

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4940.3 Rev-1

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AWWA C110/ - Gray and Ductile Iron Fittings, 3 in.

ANSI A1.10 through 48 in., for Water and

Other Liquids.

C. High Density Polyethylene

ASTM D-1248 - Polyethylene Plastics Molding and

Extrusion Materials.

D. PVC (Polyvinyl Chloride)

ASTM D1784 - Rigid (PVC) Compounds.

ASTM D3034 - Type PSM PolyVinyl Chloride

(PVC) Sewer Pipe and Fittings.

CS402-2 Corrosion Protection

CS402-2.1 The applicable specifications include:

A. Ductile Iron

AWWA C104/ - Cement Mortar Lining for Ductile

ANSI A21.4 Iron Pipe and Fittings.

AWWA C110, - Asphaltic Coatings and Linings.

C151/ANSI A21.10,

A21.51

Individual Manufacturer\'s Standards - Epoxy and

Polyethylene Linings.

B. Concrete

Individual Manufacturer\'s Standards - Sacrificial Wall,

Asphaltic, Epoxy and Polyethylene Linings.

CS402-3 Pipe Joints

The method of making joints and the material used shall be

included in the specifications. Pipe joints not described by

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4940.3 Rev-1

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currently dated Federal Specifications, American National

Standards Institute (ANSI), American WaterWorks

Association (AWWA) or American Society for Testing

Materials (ASTM) specifications shall comply with the

manufacturer\'s specifications. Compression type joints are

required for all below ground piping systems.

CS402-3.1 The applicable specifications include:

A. Concrete

ASTM C443 - Joints for Circular Concrete Sewer

and Culvert Pipe, Using Flexible,

Watertight Rubber-Type Gaskets.

(Alternate joints using steel plates

and rings for bell and spigot

connections with rubber gaskets

are preferred.)

B. Ductile Iron

AWWA C111/ - Rubber-Gasket Joints for Ductile

ANSI A21.11 Iron and Gray-Iron Pressure Pipe

and Fittings.

C. High Density Polyethylene (HDPE)

ASTM D3212 - Joints for Drain and Sewer Plastic

Pipes Using Flexible Elastomeric

Seals.

ASTM F477 - Elastomeric Seals (Gaskets) for

Joining Plastic Pipe.

D. Polyvinyl Chloride (PVC)

ASTM D3139 - Joints for Plastic Pressure pipes

Using Flexible Elastomeric Seals.

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4940.3 Rev-1

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ASTM D3212 - Joints for Drain and Sewer Plastic

pipes Using Flexible Elastomeric

Seals.

ASTM F477 - Elastomeric Seals (Gaskets) for

Joining Plastic Pipe.

CS402-4 Bedding

CS402-4.1 Bedding for rigid pipe shall be provided in three classes,

Class A, Class B, and Class C, as described herein and directed

by the Engineer to fit the depth of trench, type and size of

pipe, width of trench, and bearing value of subgrade.

A. Class A Bedding

The pipe shall be bedded in a monolithic cradle of

2,500 psi concrete having a minimum thickness of

one-fourth the outside pipe diameter or a minimum of

4 inches under the barrel and extending up the sides

for a height equal to one-fourth the outside diameter.

The cradle shall have a width equal to or greater than

the outside diameter of the pipe barrel plus 8 inches.

The side fills and to a minimum height of 12 inches

over the top of the pipe shall be filled with carefully

compacted select backfill material.

B. Class B Bedding

The pipe shall be bedded in compacted granular

material placed on a flat trench bottom. The granular

bedding shall have a minimum thickness of one-fourth

the outside pipe diameter and shall extend halfway up

the pipe barrel of the sides. The remainder of the side

fills and a minimum height of 12 inches over the top of

the pipe shall be filled with carefully compacted select

backfill material.

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C. Class C Bedding

The pipe shall be bedded in compacted granular

material placed on a flat trench bottom. The granular

bedding shall have a minimum thickness of 4 inches

under the barrel and shall extend one-sixth of the

outside diameter up the pipe barrel of the sides. The

remainder of the side fills and to a minimum height of

12 inches over the top of the pipe shall be filled with

carefully compacted select backfill material.

D. Granular material for bedding shall consist of ASTM

C-33 #67 crushed stone, clean and graded, 95 to 100

percent of which shall pass a 1/2-inch sieve with 95 to

100 percent retained on a No. 4 sieve.

E. Bell holes shall be provided in all classes of bedding so

as to relieve pipe bells of all load. Bell holes are not

required for plain end pipe.

CS402-4.2 Bedding and Backfill Materials Classifications

A. The following backfill materials classifications shall

apply. Refer to ASTM D 2487.

Class I: Angular, 1/4 to 1-1/2 inches (6 to 40 mm)

graded stone, including a number of fill materials that

have regional significance such as coral, slag, cinders,

crushed shells, and crushed stone.

Class II: Coarse sands and gravels with maximum

particle size of 1-1/2 in. (40 mm), including variously

graded sands and gravels containing small percentages

of fines, generally granular and noncohesive, either wet

or dry. Soil Types GW, GP, SW and SP are included in

this class.

Class III: Fine sand and clayey (clay filled) gravels,

including fine sands, sand-clay mixtures, and

gravel-clay mixtures. Soil Types GM, GC, SM, and SC are

included in this class.

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4940.3 Rev-1

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B. Bedding and Backfill Terminology:

o Foundation is the backfill material beneath the

bedding upon which the bedding rests.

Foundations are usually not required in stable,

non-expansive, unsaturated soils.

o Bedding is the material (usually four to six inches

in thickness) upon which the pipe rests.

o Haunching is the backfill that is placed upon the

bedding usually up to the pipe springline

(midpoint). It is essential to have compacted

haunching material under the pipe haunches

(lower curved portions of the pipe).

o Initial backfill is placed upon the haunching

usually covering the top half of the pipe. Initial

backfill is usually placed six to twelve inches

above the crown of the pipe.

o Final backfill is placed upon the initial backfill up

to grade.

CS402-4.3 Bedding and Backfill for P.V.C. and High Density

Polyethylene Pipe

A. Backfill for P.V.C. and high density polyethylene pipe

shall be in accordance with the general guidelines

presented in ASTM D-2321.

B. Only Class I materials shall be used for bedding,

haunching and initial backfill for high density

polyethylene pipe.

C. For P.V.C. pipe, bedding materials shall be Class I

except that Class II and Class III may be used with the

specific approval of the HUD-FHA engineer and where

the contractor has demonstrated his ability to obtain

proper compaction within the pipe zones.

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D. In stable soils, the bedding shall consist of a 6-inch

layer of well leveled bedding material, compacted

mechanically to 90% Modified Proctor Density.

(ASTM D 1557)

E. If the pips is being installed above the normal water

table, the haunching backfill zone shall extend to 50%

of the pipe diameter, minimum. If the pipe is being

installed below the normal water table, the haunching

backfill shall extend 2 feet above the entire pipe.

Haunching material must be thoroughly tamped under

the pipe haunches. Haunching shall be compacted

mechanically to 90% Modified Proctor Density.

(ASTM D 1557)

F. Pipes laid in expansive clay soils shall have Class I

materials used for bedding, haunching and initial

backfill.

CS402-4.4 General Bedding and Backfill Sewer Pipes

A. The pipe shall be bedded only in a dry or dewatered

trench. A foundation shall be installed where there is

unstable subgrade material in the immediate transition

areas between concrete manholes and where the

trench bottom has been over-excavated. The

foundation shall consist of initial backfill type material

compacted to 95% Modified Proctor Density (ASTM D

1557\) for P.V.C. and high density polyethylene pipe.

B. The final backfill may be native soil without large rocks

or clumps which may cause point loading on the crown

of the pipe.

C. In all cases where structural loads are anticipated

above the pipe (e.g., road crossings), the initial and

final backfill must be compacted to 90% Modified

Proctor Density. (ASTM D 1557)

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4940.3 Rev-1

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CS402-5 Allowable Sewer Pipe Infiltration

Sewer pipe joints shall be tested for infiltration upon

completion of construction. The maximum allowable

infiltration for sewer pipe shall be as follows:

CS402-5.1 Ductile Iron (Per AWWA C111/ANSI A21.11)

Infiltration - 50 gal/inch diameter/mile/day.

CS402-5.2 Concrete (ASTM C443):

50 gal/inch diameter/mile/day.

CS402-5.3 High Density Polyethylene (HDPE)

50 gal/inch diameter/mile/day.

CS402-5.4 Polyvinyl Chloride (PVC)

50 gal/inch diameter/mile/day.

CS402-6 Measuring Infiltration

CS402-6.1 Infiltration Test

Infiltration may be measured by determining the quantity of

groundwater flowing into the sewer pipe. However, this

method of measuring infiltration is only applicable if the

water table level is above the top of the pipe. This method

may not be used during low groundwater table conditions.

CS402-6.2 Exfiltration Test

Exfiltration may be measured by determining the quantity of

water exfiltrating from the sewer by surcharging the sewer

pipe. This method is general used for pipes installed above

the groundwater table.

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4940.3 Rev-1

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CS402-6.3 Low Pressure Air Test

The low pressure air test is the preferred method of

infiltration testing. The minimum time duration permitted for

a prescribed low pressure exfiltration pressure drop between

two consecutive manholes should not be less than that

shown in the table below. The prescribed drop should not

exceed 0.5 psi from 3.5 to 3.0 psi in excess of the ground

water pressure above the top of the sewer.

MINIMUM DURATION FOR AIR TEST PRESSURE DROP

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CS403 DESIGN

CS403-1 Size

Other than for individual unit service connections, 8-inch

diameter sewer pipe will be the minimum acceptable size.

CS403-2 Depth

In general, all sewers must be designed deep enough to drain

basements or be 6 feet beneath the surface, whichever is

deeper. Where for specific reasons shallower depths are

necessary and can be justified, the sewer must be protected

to prevent its being damaged. All sewers shall be designed

and bedded or encased to prevent cracking or excessive

deflection due to superimposed loads and weight of backfill

material. Proper allowance for loads on the sewer shall be

made, taking into account the width and depth of trench.

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4940.3 Rev-1

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Note: The above sewer depth requirements do not

apply to service sewers (i.e., sewers which carry

wastewater from the residential unit to a

collector or trunk sewer). Service sewers shall

be no less than two feet beneath the surface.

CS403-3 Capacity

Sewer systems shall be designed for sanitary sewage flow

using an average daily per capita flow of not less than 100

gallons per capita per day unless otherwise justified by sound

engineering data. On this basis lateral and submain sewers

should be designed with capacities, when running full, of not

less than 4 times the average daily sewage flow. In similar

manner, outfall sewers should be designed for 2.5 times the

average daily sewage flow. Additional allowance should be

made for significant waste contributions such as shopping

centers and industries, and infiltration, taking into account

soil and groundwater conditions, and for the possibilities of

future expansion or extension.

CS403-4 Velocity of Flow

All sewers shall be designed and constructed with hydraulic

slopes sufficient to give mean velocities, when flowing full,

of not less than 2.0 feet per second based on Kutter\'s or

Manning\'s formula using an \"n\" value relative to the pipe

material used. The following table provides the minimum

slopes which may be utilized for a given diameter sewer pipe:

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CS403-5 Increasing Size and Junctions

When sewers are increased in size, or when a smaller sewer

joins a larger one, the invert of the larger sewer should be

lowered sufficiently to maintain the same energy gradient at

the junction. An approximate method for securing this result

is to place the 0.8 depth point of both sewers at the same

elevation.

CS403-6 Alignment

Sewers, up to and including those with a 24 inch diameter,

must be laid with uniform slope and alignment between

manholes.

CS403-7 High Velocity Protection

In the case of sewers where the slope and volume are such

that velocities of 15 ft. per second or greater may be

realized, special provisions shall be made to protect against

erosion and thrust.

CS404 MANHOLES

CS404-1 Location

Manholes shall be installed at the end of each line; at all

changes in grade, size or alignment; at all intersections and

at distances not greater than 400\' for sewers 15\" or less and

500\' for sewers 18\" to 30\". Greater spacing may be

permitted in larger lines and those carrying a settled

effluent.

CS404-2 Materials of Construction

Manholes shall be of the precast concrete with gasketed

joints (ASTM C 478) or concrete poured-in-place type.

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CS404-3 Diameter

The minimum diameter of manholes shall be 48\" with larger

diameters being preferable for sewer pipes greater than 18\"

in diameter.

CS404-4 Drop Type Pipe

A drop pipe should be provided for a sewer entering a

manhole at an elevation of 24\" or more above the manhole

invert. Where the difference in elevation between the

incoming sewer and the manhole invert is less than 24\" the

invert should be filleted to prevent solids deposition.

CS404-5 Flow Channel

The flow channel through manholes should be made to

conform in shape and slope to that of the sewer pipe.

CS404-6 Watertightness

Solid, watertight, bolt-down manhole covers are to be used

wherever the manhole tops may be flooded by street runoff

or high water.

CS404-7 Joints to Pipes

Inlet and outlet pipes shall be joined to the manhole with a

gasketed flexible watertight connection or other such

watertight connection which provides for differential

settlement between the pipe and manhole wall.

CS405 INVERTED SIPHONS

Inverted siphons shall have not less than two barrels with a

minimum pipe size of not less than 6\" and shall be provided

with the necessary appurtenances for convenient flushing

and maintenance; the associated manholes shall have

adequate clearances for rodding; and in general sufficient

head should be provided and pipe sizes selected to secure

velocities of at least 3.0 feet per second for average flows.

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The inlet and outlet connections must be designed so that

the normal flow can be diverted to one barrel allowing either

barrel to be cut out of service for cleaning.

CS406 PROTECTION OF WATER SUPPLIES

CS406-1 Water Supply Interconnections

There shall be no physical connection between a public or

private potable water supply system and a sewer, or

appurtenance thereto, which would permit the passage of

any sewage or polluted water into the potable water supply.

CS406-2 Relation to Water Works Structures

While no general statement can be made to cover all

conditions, it is generally recognized that sewers shall be

kept remote from public water supply, wells, or other water

supply sources and structures.

CS406-3 Relation to Water Mains

CS406-3.1 Horizontal Separation: Whenever possible, sewers should be

laid at least 10 feet, horizontally, from any existing or

proposed water main. Should local conditions prevent a

lateral separation of 10 feet, a sewer may be laid closer than

10 feet to a water main so long as the elevation of the top

(crown) of the sewer is at least 18\" below the bottom

(invert) of the water main, and the sewer pipe is:

A. Laid in a separate trench, or

B. Laid in the same trench with the water main(s) located

at one side on a bench of undisturbed earth.

CS406-3.2 Vertical Separation: Whenever sewers must cross under

water mains, the water main and/or sewer shall be laid at

such an elevation that the top of the sewer is at least 18\"

below the bottom of the water main. When the elevation of

the sewer cannot be varied to meet the above requirement,

the water main shall be relocated to provide this separation.

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Where relocation is not possible, the water main shall be

constructed so that one full length of water main pipe will be

centered over the sewer so that both joints will be as far

from the sewer as possible.

CS500 SEWAGE PUMPING STATIONS

CS501 GENERAL

Sewage pumping stations shall be located and constructed

so that the station and electrical control panel will not be

subject to flooding. A suitable structure, preferably located

off the right-of-way of streets and alleys, shall be provided.

It is important that the station be readily accessible by road.

CS502 DESIGN

CS502-1 Type

Sewage pumping stations may be of the wet-well mounted,

wet-well installed (using submersible pumps), or dry pit with

wet well (using flooded suction pumps). Pneumatic ejector

stations shall not be permitted.

CS502-2 Structures

CS502-2.1 Entrances: Where dry pit type installations are used, wet

wells and dry pits should be completely separated with a

separate entrance to each.

CS502-2.2 Pump Removal: Provisions should be made to facilitate

removing pumps and motors.

CS502-2.3 Access: Suitable and safe means of access shall be provided

to dry pits and wet wells of pump stations. Stairways are

preferred for pump stations which incorporate bar screens or

other mechanical equipment requiring frequent inspection or

maintenance.

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CS503 PUMPS

CS503-1 Duplicate Units

At least two pumps shall be provided for each pumping

station. If only two pumps are provided, the pumps should

have the same capacity with each unit being capable of

handling the expected maximum flow at the required head.

Where three or more pumps are provided, the pumps should

be designed to fit actual flow conditions and of such capacity

that with any one pump out of service the remaining pumps

will have capacity to handle maximum sewage flows at the

required head.

CS503-2 Protection Against Clogging

Pumps handling raw sewage shall be preceded by readily

accessible bar racks with clear openings not exceeding 2

inches unless the pumping equipment is of a special solids

handling type. Where screens are located below ground,

convenient facilities must be provided for handling

screenings. For the larger or deeper pump stations, duplicate

screens are preferred. For large pump stations mechanically

cleaned bar-screens should be considered.

CS503-3 Priming

The pump should be so placed that under normal operating

conditions it will operate under a positive suction head unless

the pump is designed for suction lift.

CS503-4 Electrical Equipment

Electrical equipment in enclosed places where gas may

accumulate shall comply with the American Insurance

Association specifications for hazardous conditions (AIA

Type 7), and NFPA-70, National Electrical Code, for Class 1,

Group D, Division 1 locations. All electrical equipment shall

conform to NFPA 820.

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CS503-5 Intake

Each pump should have an individual intake. Wet well design

should be such as to avoid turbulence and vortexing near the

intake.

CS503-6 Dry Pit Dewatering

A separate sump pump shall be provided in dry pits to

remove leakage or drainage with the discharge above the

high level of the wet well. Water ejectors connected to a

potable water supply are not acceptable. All floor and

walkway surfaces shall have adequate slope to the point of

drainage.

CS504 CONTROLS

In stations with duplicate units, provision should be made to

automatically alternate the pumps and provide for lead-lag

operation.

CS505 VALVES

Suitable shutoff valves shall be placed on suction and

discharge lines for each pump. A check valve shall be placed

on each discharge line, between the shutoff valve and the

pump. Where pressures dictate, check valves should be

designed to eliminate the possibility of water hammer using

hydraulic, pneumatic or electronically cushioned check

valves.

CS506 WET WELLS

CS506-1 Size

The wet well shall be sized so that with any combination of

inflow and pumping, no single pump will start in excess of

five (5) times per hour or run less than five (5) minutes

during any cycle. In general, detention periods should be

kept to the minimum compatible with proper operation of the

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pumping equipment so as to prevent sewage from becoming

septic.

CS506-2 Floor Slope

The wet well floor shall have a minimum slope of 1 to 1.75

to the hopper bottom. The level bottom area shall be kept to

an absolute minimum. Where it may be necessary to pump

sewage prior to grit removal, the design of the wet well

should receive special attention so that grit buildup is

avoided, and the discharge piping shall be designed to

prevent grit settling in the pump discharge lines.

CS506-3 Overflows/Bypasses

Wetwell overflows and bypasses will not be permitted.

CS507 VENTILATION

Adequate positive ventilation shall be provided for all pump

stations. Where the pump it is below the ground surface,

mechanical ventilation is required. Ventilation shall be

arranged so as to independently ventilate the dry pit and the

wet well if screens or mechanical equipment requiring

maintenance or inspection are located in the wet well. There

shall be no interconnection between the wet well and dry pit

ventilation systems. Dampers should not be used on exhaust

or fresh air ducts and fine screens or other obstructions in

the air ducts should be avoided to prevent clogging.

Switches for operation of ventilation equipment should be

marked and located conveniently near the entrance.

Consideration should be given to automatic controls where

intermittent operation is used. In climates where excessive

moisture or low temperatures may be encountered,

consideration should be given to installation of

dehumidification and/or heating equipment.

In dry pits, ventilation may be either continuous or

intermittent. For continuous operation at least six complete

air changes per hour should be provided. For intermittent

operation at least thirty air changes per hour should be

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provided. Similar venting shall be used for wet wells except

that 12 changes per hour should be provided for continuous

operation.

CS508 FLOW MEASUREMENT

At larger pumping stations, consideration should be given to

installation of suitable devices for measuring sewage flow

and power consumption.

CS509 WATER SUPPLY

There shall be no physical connection between any potable

water supply and a sewage pumping station which under any

conditions might cause contamination of the potable water

supply.

CS510 FORCE MAINS

CS510-1 Materials

Pressure piping shall consist of either Ductile Iron or any

pressure pipe classes of polyvinyl chloride which meet

requirements of pump pressure, depth of cover and

installation conditions.

CS510-1.1 Applicable Specifications include:

A. Ductile Iron

AWWA C151 - Ductile Iron Centrifugally Cast

ANSI A21.51 in Metal Molds or Sand Lined

Molds for Water or Other

Liquids.

AWWA C110/ - Gray and Ductile Iron Fittings,

ANSI A21.10 3 in. through 48 in., for Water

and Other Liquids.

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B. Polyvinyl Chloride (PVC)

AWWA C900 - Polyvinyl Chloride (PVC)

Pressure Pipe 4 in. through 12

in., for Water.

ASTM D2241 - Poly Vinyl Chloride (PVC)

Plastic Pipe (SDR-PR).

ASTM D1784 - Rigid Poly Vinyl Chloride and

Chlorinated Poly Vinyl Chloride

Compounds.

CS510-2 Velocity

A design average flow velocity in excess of two feet per

second shall be maintained; maximum velocity should be

limited to eight feet per second.

CS510-3 Sewage Air Relief Valves

Automatic sewage air relief valves shall be placed at high

points in the force main to prevent air locking. Where

possible the force main shall pitch continuously upward to

avoid any high points in the line.

CS510-4 Termination

Force mains should enter the gravity sewer system at a

manhole with a 90 deg upturn of the force main within the

manhole, or the forcemain should discharge within a

partitioned segment of a manhole with the partition being as

high as the crown of the force main.

CS511 POWER SUPPLY

Power supply should be available from at least two

independent generating sources, or emergency power

equipment shall be provided. The installation of an

emergency electrical receptacle shall be acceptable as a

secondary emergency power source as set forth in CS605-3.

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CS600 SEWAGE TREATMENT WORKS

CS601 PLANT LOCATION

In general to avoid local objections and for sound engineering

and environmental reasons, a sewage treatment plant site

should be located as far as practicable from any presently

inhabited area, any area which will probably be inhabited

within a reasonable future period, any wetlands, or any site

with poor soils. If an undesirable location must be used,

special consideration must be given to the design and type of

plant provided. Treatment plants shall be located at an

elevation which is not subject to flooding or else be

adequately protected against flood damage. The plant should

be readily accessible at all times. A 100 foot buffer area

shall be provided between all treatment facilities (including

ponds) and property lines; however, this buffer requirement

may be waived by HUD-FHA in situations for which it can be

conclusively shown that such a buffer is not reasonably

possible to provide. No portion of any residential structure

shall be closer than 300 feet to any wastewater treatment

unit (including ponds).

CS602 QUALITY OF EFFLUENT

Degree of treatment and desired quality of effluent for

sewage treatment plants shall be based on the requirements

of the U.S. Environmental Protection Agency or the properly

delegated state regulatory environmental agency.

CS603 BASIS FOR DESIGN LOADING

The design of sewage treatment units shall be based on

organic loading, hydraulic loading and solids loading at a

minimum. A biochemical oxygen demand (BOD5) loading of

0.17 lb. per person served per 24 hours is required except

that the loading shall be increased to 0.25 lb.

BOD/person/day if the installation of mechanical household

garbage grinders is proposed. The engineer\'s report (DDR)

should clearly justify the computed total daily average flows

and loads to include the number of persons contributing per

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property served and the estimated volume and load

contributed by each occupant. (See CS403.) Commercial

and industrial flow and infiltration, when appropriate, shall

also be given due consideration.

CS604 CONSTRUCTION MATERIALS

Due consideration should be given to the selection of

materials which are to be used in sewage treatment works

because of the possible presence of hydrogen sulfide and

other corrosive gases, greases, oils, and similar constituents

frequently present in sewage. The selection of materials is

particularly important in the selection of metals and coatings.

The protective coating to be applied to the interior and

exterior surfaces of metal treatment tanks shall be identified

and described in detail in the project specifications.

CS605 ESSENTIAL FACILITIES

CS605-1 Internal By-Passes

Properly located and arranged by-pass capabilities to other

process units shall be provided so that each unit of the plant

can be removed from service without disturbing the operation

of the treatment plant.

CS605-2 Grading, Landscaping, and Fencing

Upon completion of the plant, the ground shall be properly

graded, finished, and landscaped. Concrete or gravel

walkways should be provided for access to all units. Where

possible, steep slopes should be avoided. Surface water

should not be permitted to drain into any treatment unit.

Provision should be made for landscaping, particularly when

a plant must be located close to a residential area. The

entire treatment plant area shall be enclosed by a fence of

suitable quality and height to preclude entrance by

unauthorized persons.

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CS605-3 Emergency Power Facilities

Where two independent electrical feed sources are not

available, a standby power source capable of running

essential process units shall be provided. An emergency

power receptacle compatible with owner\'s emergency power

generation equipment will be acceptable as a standby power

source; however, in this instance, the assurance of the

availability of an adequately sized and functional mobile

auxiliary power generator on an ongoing basis is required.

CS605-4 Water Supply

An adequate supply of safe potable water should be provided

for use in the laboratory and for general cleanliness around

the plant. No piping or other connections shall exist in any

part of the treatment works which under any condition might

cause the contamination of a potable water supply.

Adequate backflow prevention shall be provided.

CS605-5 Sanitary Facilities

Sanitary facilities such as toilet, shower, and lavatory are

recommended for all wastewater treatment facilities and shall

be required for wastewater treatment facilities with 0.1 MGD

design capacity and larger.

CS605-6 Laboratory Equipment

The treatment works should include a properly equipped

laboratory for making the necessary analytical determinations

and operating control tests; however, laboratories are

optional for wastewater treatment systems smaller than 0.1

MGD.

CS605-7 Sewage Flow Measurement

Facilities for measuring and recording the volume of raw

sewage entering and treated effluent leaving the plant shall

be provided at the treatment works. However, for treatment

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plants smaller than 1 MGD, measurement of either influent

flow or effluent flow shall be sufficient.

CS605-8 Safety

Adequate provision should be made to protect the operator

and any visitors from unnecessary hazards. All OSHA

regulations apply to all phases of plant design.

CS605-8.1 All units or structures which may endanger human life shall

be enclosed by a suitable fence or have keyed lock doors.

CS605-8.2 Hand rails shall be provided where walkways exceed two

feet above grade and around the interior of all basins.

Elevated walkways shall have handrails with kickplates.

CS605-8.3 First aid equipment shall be provided.

CS605-8.4 Proper fire extinguishing equipment shall be provided at

convenient locations throughout the plant.

CS605-8.5 Proper safety and personal protective equipment shall be

provided for the handling of all chemicals.

CS606 OTHER TREATMENT PROCESSES

Treatment processes other than those described in the

following sections are eligible for consideration on the basis

of their proven and documented record of performance and

operating experience. All treatment processes and

equipment shall be approved by the U.S. Environmental

Protection Agency or its delegated regulatory agency. Where

other treatment processes are proposed, a detailed

description of each process and design data shall be

submitted.

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CS700 PRIMARY TREATMENT

CS701 SCREENING DEVICES

CS701-1 Use

All sewage treatment plants shall provide coarse and/or fine

screening for protection of pumps and downstream

processes. Screens may be used in conjunction with

mechanical shredders. All equipment should be readily

accessible for maintenance.

CS701-2 Access

Hand-cleaned screens located in deep pits shall be provided

with stairway access, adequate lighting and ventilation. A

convenient and adequate means for removing screenings

shall be provided.

Screening devices installed in a building where other

equipment or offices are located should be separated from

the rest of the building, provided with separate outside

entrances, and provided with a separate means of ventilation.

CS701-3 Spacing of Bars

CS701-3.1 Non-Mechanical Screens: Clear openings between bars

should be from one to six inches depending upon

downstream equipment requirements. Construction of bar

screens should be such that they can be conveniently raked.

CS701-3.2 Mechanical Screens: Clear openings for mechanically

cleaned screens may be as small as five-eights of an inch.

CS701-3.3 Velocities: For hand-raked bar screens the screen chamber

should be designed to provide an approach velocity of

approximately 2.0 feet per second at average rate of flow.

Maximum velocities during wet weather periods shall not

exceed 3.0 feet per second for mechanically cleaned screens.

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CS701-3.4 Invert: The screen channel invert shall be located 3\" to 6\"

below the invert of the incoming sewer.

CS701-3.5 Slope: Hand-cleaned screens, except those for emergency

use, shall be placed on a slope between 30 to 45 degrees

with the horizontal.

CS701-4 Channels

The channel preceding and following the screen shall be

filleted to prevent stranding and sedimentation of solids.

CS701-5 Safety Devices

CS701-5.1 Auxiliary Control: All mechanical units which are operated by

timing devices should be provided with auxiliary float controls

which will set the cleaning mechanism in operation at

predetermined high water marks. These auxiliary controls

should operate independent of the regular controls.

CS701-5.2 Electrical Fixtures and Controls: Electrical fixtures and

controls in enclosed places where gas may accumulate shall

comply with the American Insurance Association

specifications for hazardous conditions and the National

Electric Code for Class 1, Group D, Division 1 locations.

CS701-6 Screenings

Ample sanitary facilities must be provided for the removal,

handling, storage and disposal of screenings. Hand-cleaned

screening facilities should include an accessible platform from

which the operator may rake screenings easily and safely.

Suitable drainage facilities should be provided back to the

head of the plant both for the platform and for storage areas.

Removal of screenings and proper disposal in a sanitary

landfill is the preferred method of disposal.

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CS702 COMMINUTING DEVICES

CS702-1 Restrictions On Use

Comminuting devices may not be utilized in wastewater

treatment plants where primary clarifiers are not provided.

The use of comminuting devices is generally discouraged in

all wastewater treatment plants and pumping stations in

favor of screening devices. Where comminuting devices are

used, the following requirements must be met.

CS702-2 Channels

Design of approach channels should provide for gates or

similar devices to bypass the flow from any one or more

comminutors to a bypass channel with a bar screen. Drains

should be provided in each comminutor trap to allow for

dewatering.

CS702-3 Auxiliary Screens

Where mechanically operated screening devices or

shredding-screening devices are employed, auxiliary units

should be provided, such units being either of the mechanical

or hand-cleaned type and arranged in such a manner as to

provide for automatic diversion of the sewage flow should the

regular units fail.

CS703 GRIT CHAMBERS

Grit chambers are recommended for plants treating sewage

from sanitary sewers where the accumulation of grit is

anticipated. The Engineer\'s report (DDR) should include full

justification if grit chambers are not included in the design

for treatment plants greater than 50,000 gpd in size.

CS703-1 Location

It is recommended that grit chambers be located ahead of

pumps and comminuting devices. In such cases, coarse bar

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racks should be placed ahead of mechanically cleaned grit

chambers.

CS703-2 Number of Units

Duplicate hand-cleaned units or a single mechanically cleaned

unit with an automatic by-pass to a hand-cleaned unit shall

be provided. Mechanically cleaned grit chambers are

recommended for larger treatment plants. Single, hand-cleaned

channels with by-pass are acceptable for sewage

treatment plants serving small sanitary sewerage systems.

Treatment plants 50,000 gpd or smaller may omit grit

collection.

CS703-3 Design Factors

CS703-3.1 Inlet: Inlet turbulence shall be minimized.

CS703-3.2 Velocity and Detention: Channels should be designed to

provide controlled velocities to allow settlement of grit. The

detention period and velocities shall be based on the size of

particle to be removed.

CS703-3.3 Grit Washing: All chambers not providing positive velocity

control should include means for grit washing to further

separate organic and inorganic materials.

CS703-3.4 Drain: Provisions should be made for draining each unit.

CS703-4 Grit Removal

Grit chambers located in deep pits should be provided with

facilities for hoisting grit to ground level, access by

stairway, adequate ventilation, and adequate lighting.

CS703-5 Grit Disposal

Suitable means for grit storage and disposal shall be

provided.

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CS704 CLARIFIERS

CS704-1 General Considerations

CS704-1.1 Mechanical Systems: All clarifiers shall have mechanical

mechanisms for sludge concentration and removal.

Non-mechanical settling tanks and Imhoff tanks shall not be

allowed.

CS704-1.2 Multiple Units: Multiple, parallel clarifiers shall be

provided for each clarification installation such that the

removal of any single parallel clarifier from service will

not result in a significant reduction in treatment efficiency,

overflows or equipment damage. However, single unit primary

clarifiers may be utilized for treatment plants less than 1 MGD

in capacity.

CS704-2 Design Characteristics

CS704-2.1 Inlets: Inlets shall be designed to dissipate the inlet

velocity, diffuse the flow equally across the entire cross

section of the clarifier to prevent shortcircuiting. Channels

should be designed to maintain a velocity of at least 1 foot

per second at 0.5 design flow. Corner pockets and dead ends

shall be eliminated and corner fillets or channeling used

where necessary. Provisions shall be made for elimination

or removal of floating materials in inlet structures having

submerged ports.

CS704-2.2 Scum Baffles: Scum baffles shall be provided ahead of outlet

weirs on all primary and final clarifiers.

CS704-2.3 Weirs: Overflow weirs shall be adjustable. On circular tanks

the weir should extend around the entire periphery of the

tank. Weir loadings shall not exceed 10,000 gallons per day

per linear foot for plants designed for average flows of 1.0

MGD or less. Weir loadings for plants designed for flows in

excess of 1.0 MGD shall not exceed 15,000 gallons per day

per linear foot.

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CS704-2.4 Submerged Surfaces: The tops of troughs, beams, and

similar construction features which are submerged shall have

a minimum slope of 1.4 vertical to 1 horizontal. The

underside of such features should have a slope of 1 to 1 to

prevent the accumulation of scum and septic solids.

CS704-2.5 Protection: All settling basins shall be adequately equipped

to provide easy access for maintenance and for protection to

operators. Such features shall include stairways, walkways,

handrails, and lighting.

CS704-2.6 Surface Settling Rates

Unless otherwise approved by the HUD-FHA engineer, the

following maximum surface settling rates shall be used:

A. Primary Clarifiers:

1\. Surface settling rates for primary clarifiers shall

not exceed 800 gallons per day per square foot

for plants having a design flow of 1.0 M.G.D. or

less. Higher surface settling rates may be

permitted for larger plants.

2\. The allowable estimate of BOD removal by

primary clarifiers treating normal sewage shall

not be greater than 35%. Allowable BOD

removal by sedimentation of industrial wastes

will be dependent upon the type of wastes

contributed.

B. Intermediate Clarifiers: Surface settling rates for

intermediate clarifiers should not exceed 600 gallons

per square foot per day based on the design flow rate.

C. Final Clarifiers: Surface settling rates for final

clarifiers shall not exceed 450 gallons per day per square

foot based on the design flow rate.

CS704-2.7 Scum Removal: Scum removal equipment shall be provided

ahead of the outlet weirs on all primary and final clarifiers.

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The design should provide for the scum to be collected in a

scum well for pumping to a digester or decanting unit.

CS704-2.8 Sludge Removal: Provision for continuous sludge removal

from clarifiers is recommended. Where sludge is removed

from a clarifier to a digester, a sludge well or other

appropriate device should be installed for viewing and

sampling the sludge. Each sludge hopper shall have an

individually valved sludge withdrawal line not less than 6\" in

diameter.

CS704-2.9 Depth: The side water depth for all clarifiers shall not be

less than 12 feet unless otherwise approved by the HUD-FHA

engineer.

CS704-2.10 Sludge Hoppers: Hoppers shall be accessible for

maintenance from the operating level. The minimum slope of

the side walls of sludge hoppers shall be 1.7 vertical to 1

horizontal.

CS800 SLUDGE DIGESTION AND DISPOSAL

CS801 GENERAL

CS801-1 Classification: Separate sludge digestion tanks will be

classified as either \"aerobic or \"anaerobic\". Generally,

aerobic tanks shall be those providing for digestion,

supernatant separation and sludge concentration and storage

in tanks open to the atmosphere, with mechanical aeration

provided. Anaerobic tanks shall be those where the digestion

process is accomplished within an enclosed unit devoid of

oxygen.

CS801-2 Multiple Units: Multiple tanks are recommended for larger

sewage treatment plants. Where a single digestion tank is

used, it is desirable to have a lagoon or storage tank for

emergency use so that the tank may be taken out of service

without unduly interrupting plant operations.

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CS802 AEROBIC DIGESTION TANKS

CS802-1 Mixing and Air Requirements: Mechanical aeration shall be

provided in sufficient amount to keep the solids in

suspensions and to maintain a dissolved oxygen (DO) level of

2 mg/l or more. A minimum mixing and oxygen requirement

of 30 cfm per 1,000 cubic feet of tank volume shall be

provided with the largest blower out of service.

CS802-2 Capacity

CS802-2.1 Volatile Solids Loading: Volatile solids loading rates shall

not exceed 100 pounds per day per 1,000 cubic feet of volume.

CS802-2.2 Solids Retention Time (SRT): Minimum SRT values shall be

provided, as follows:

A. 15 days for waste activated sludge.

B. 20 days for combined primary and waste activated

sludge.

Additional time should be considered where local conditions

dictate such as in cold weather climates.

CS802-2.3 Supernatant Removal: Aerobic digesters shall be provided

with supernatant removal facilities. Supernatant shall be

returned to the head of the plant.

CS803 ANAEROBIC DIGESTION TANKS

CS803-1 Depth: The proportion of depth to a diameter should be such

as to allow for the formation of two feet or greater of

supernatant liquor and also to maintain the minimum surface

area so as to minimize heat loss.

CS803-2 Maintenance Provisions: To facilitate emptying, cleaning,

and maintenance, the following features are desirable:

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CS803-2.1 Slope: The tank bottom should slope to drain toward the

withdrawal pipe at a minimum slope of 3 vertically to 12

horizontally.

CS803-2.2 Access Manholes: At least two access manholes should be

provided in the top of the gas dome. One opening should be

large enough to permit the use of mechanical equipment to

remove grit and sand.

CS803-3 Capacity

CS803-3.1 Solids Basis: Where the composition of the sewage and

solids production has been established, tank capacity shall be

computed from the volume and character of sludge to be

digested. Due allowance shall be provided for sludge storage

and supernatant holding.

CS803-3.2 Population Basis: Where solids production data are not

available, the unit capacities shown below shall be used for

plants treating domestic sewage. The below shown

capacities shall be increased for any industrial wastes in the

sewage. Additional capacity shall be provided where garbage

solids are to be digested. The capacities shown below apply

where digested sludge is dewatered on sand drying beds.

The below shown values may be reduced if the sludge is

dewatered mechanically. Required digester volumes should

be calculated on the basis of the digester bottom having

planes sloping thirty degrees from the horizontal upward from

the end of the withdrawal pipe unless sludge mixing

equipment is installed.

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For small installations (population 5,000 or less)

consideration should be given to using the larger values. Unit

capacities required for separate unheated tanks shall be

increased in accordance with local climatic conditions.

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CS803-4 Anaerobic Tank Gas Collection, Piping and Appurtenances

CS803-4.1 General: All portions of the gas system including the space

above the tank liquor, storage facilities and piping shall be

so designed that under all normal operating conditions,

including sludge withdrawal, the gas, where any gas leakage

might occur, should be adequately ventilated.

CS803-4.2 Safety Equipment: All necessary safety facilities shall be

included where gas is produced. Pressure and vacuum relief

valves and flame traps together with automatic safety shut

off valves shall be provided. Water seal equipment shall not

be installed.

CS803-4.3 Digester Gas Piping and Condensate: Gas piping shall be of

adequate diameter and shall slope to condensation traps at

low points. The use of float controlled condensate traps is

not permitted.

CS803-4.4 Digester Gas Utilization Equipment: Gas burning boilers,

engines, and other equipment shall be located at ground level

and in well ventilated rooms. Gas lines to these units shall

be provided with suitable flame traps.

CS803-4.5 Electrical Fixtures: Electrical fixtures in enclosed places

where digester gas may accumulate shall comply with the

American Insurance Association specifications for hazardous

conditions and the NEC for Class 1, Group D, Division 1

locations.

CS803-4.6 Waste Gas: All waste gas shall be burned or otherwise

beneficially used. Waste gas burners shall be located at least

25 feet away from any plant structure if placed at ground

level, or located at roof level if sufficiently removed from

the digester tanks.

CS803-4.7 Ventilation: All underground enclosures connecting with

digestion tanks or containing sludge or digester gas piping or

equipment shall be provided with forced ventilation.

CS803-4.8 Meter: A gas meter with by-pass shall be provided.

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CS803-4.9 Sludge Inlets: Provision should be made for the recirculation

of sludge. One inlet should discharge above the liquid level

and be located at approximately the center of the tank unless

mechanical scum breakers are employed. The raw sludge

inlet line should discharge at a point at least equal to the

radius of the tank from the supernatant drawoffs.

CS803-5 Digestion Tank Heating

CS803-5.1 Insulation: Wherever possible digestion tanks should be

constructed above the ground-water level and should be

suitably insulated by earth embankments or by other means.

CS803-5.2 Heating Facilities: If heat exchangers are used, hot water

coils shall be at least two inches in diameter, and the coils

as well as the support brackets shall be of ductile iron. The

use of dissimilar materials shall be avoided to minimize

galvanic action. The high point in the coils shall be vented

to avoid air lock.

CS803-5.3 Heating Capacity for Anaerobic Tanks: If tank heaters are

utilized, sufficient heating capacity shall be provided to

maintain the sludge at 85 degrees F. to 95 degrees F. or

more at all times. Where digestion tank gas is used for

heating, an auxiliary fuel may be required.

CS803-5.4 Heating Coil Operating Controls

A. Mixing Valves: A suitable automatic mixing valve shall

be provided to temper the boiler water with return coil

water so that the inlet water to the coils can be held to

a temperature of 140 degrees F. or less. Manual

control should also be provided by suitable by-pass

valves.

B. Boiler Controls: The boiler should be provided with

suitable automatic controls to maintain the boiler

temperature at 180 degrees F. or more to minimize

corrosion and to shut off the main gas supply in the

event of pilot burner or electrical failure.

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C. Thermometers: Thermometers should be provided to

show temperatures of the sludge, hot water feed, hot

water return, and boiler water.

CS803-5.5 External Heater Operating Controls: All controls necessary

to insure effective and safe operation are required.

CS803-6 Supernatant Withdrawal

CS803-6.1 Piping Size: Supernatant piping should not be less than six

inches in diameter.

CS803-6.2 Withdrawal Arrangements: Piping should be arranged so that

withdrawal can be made from multiple levels in the tank.

Telescoping valves are recommended.

CS803-6.3 Sampling: Provision should be made for sampling at each

supernatant draw-off level. Sampling pipes should be at least

1-1/2 inches in diameter.

CS803-6.4 Supernatant Disposal: Digester supernatant shall be returned

to the head of the plant.

CS804 SLUDGE PUMPS AND PIPING

CS804-1 Sludge Pumps

CS804-1.1 Capacity: Pump capacities should be adequate but not

excessive. Provision for varying pump capacity for multiple

pumps is recommended.

CS804-1.2 Duplicate Units: Duplicate pumping units are required as

failure of one unit would seriously impair plant operation.

CS804-1.3 Type: Plunger pumps, progressive cavity, diaphragm, or

centrifugal (solids handing) pumps should be provided for

handling raw sludge.

CS804-1.4 Minimum Head: A minimum positive suction head of 24

inches shall be provided at the suction side of centrifugal

type pumps. Suction lifts should be avoided where possible.

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CS804-1.5 Sampling Facilities: Unless sludge sampling facilities are

otherwise provided, quick closing sampling valves shall be

installed at the sludge pumps. The size of valve and piping

should be at least 1-1/2 inches.

CS804-2 Sludge Piping

CS804-2.1 Size and Head: Sludge withdrawal piping should have a

minimum diameter of eight inches for gravity withdrawal and

six inches for suction. Sludge pump discharge piping shall be

at least four inches in diameter. Where withdrawal is by

gravity, adequate head and clean-outs shall be provided.

CS804-2.2 Slope: Gravity piping shall be laid on uniform grade and

alignment. Slope of gravity discharge piping shall not be less

than 3 percent. Arrangements for draining and flushing

discharge lines shall be provided.

CS805 SLUDGE DRYING BEDS

CS805-1 Area

The sludge drying bed area needed for dewatering digested

sludge is dependent upon weather conditions. In the

northern part of the United States, where the summers are

short, more drying bed area is required than in more

temperate areas. The following per capita areas have been

found satisfactory for the area between 40 degrees and 45

degrees N. Latitude. South of 40 degrees N. Latitude these

figures can be reduced by 25% North of 45 degrees N.

Latitude they should be increased 25%. Consideration

should also be given to areas which have excessive rainfall.

The design shall be based on the following table. Deviations

from the area in the table will be considered only on the basis

of information included in the engineer\'s report (DDR). Areas

may be reduced if chemical addition is used to enhance the

dewatering characteristics of the sludge.

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CS805-2 Quantity

A minimum of two beds are required. However, there shall

be a sufficient number of standby units to permit proper

sludge drying at all times.

CS805-3 Media

CS805-3.1 Gravel: The lower course of gravel around the underdrains

shall be properly graded and placed to a minimum depth of

12 inches and extend at least 6\" above the top of the

underdrains. Placement in two or more layers is

recommended. The top layer, consisting of gravel 1/8 inch

to 1/4 inch in size shall be placed to a minimum depth of 3

inches.

CS805-3.2 Sand: The top course shall consist of clean coarse sand to

a thickness of 12 to 15 inches. The finished sand surface

should be level.

CS805-4 Underdrains

Polyvinyl chloride, vitrified clay tile and precast blocks of

vitrified tile or concrete are acceptable materials for use as

underdrains. Vitrified clay blocks shall comply with ASTM

Specification C159. Other materials or methods for

underdraining of filters will be considered subject to the

submission of complete details and the description included

in the engineer\'s report (DDR). All materials used shall be

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capable of supporting the loads imposed. The minimum

diameter of underdrains shall be 4 inches, and the lateral

spacing shall not exceed 20 feet.

CS805-5 Walls

Walls shall be watertight and extend 15 to 18 inches above

and at least 6 inches below the sand surface, and be

structurally adequate to the internal and external loads

imposed.

CS805-6 Sludge Influent

The sludge pipe to the beds shall be installed so as to drain

effectively. Concrete splash plates shall be provided at

sludge discharge points.

CS805-7 Drainage Disposal

Drainage from beds shall be returned to the head of the

plant.

CS806 MECHANICAL SLUDGE DEWATERING FACILITIES

If it is proposed to dewater or dispose of sludge by

mechanical methods such as belt or plate and frame filter

press, a detailed description of the unit and design data shall

accompany the plans. Suitable evidence of the satisfactory

performance of the units will be required.

CS807 SLUDGE DISPOSAL

Dried sludge may be composted, landfilled, spread over or

cut into fields or in some cases sold to fertilizer

manufacturers. Whichever method is proposed, approval by

the local health and environmental permitting agencies will be

required.

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CS900 SECONDARY TREATMENT

CS901 PACKED TOWERS OR TRICKLING FILTERS

(\"TRICKLING FILTERS\")

CS901-1 Applicability

Trickling filters may be used for treatment of sewage and

industrial wastes of a type amenable to purification by

biological processes. Trickling filters shall be preceded by

primary clarification.

CS901-2 Design Basis

The trickling filters shall be designed to provide a reduction

in biochemical oxygen demand as necessary to properly

condition the sewage for subsequent treatment processes.

CS901-3 Dosing Equipment

CS901-3.2 Dosing: The distribution devices may be actuated by siphons

or pumps or by gravity discharge from preceding treatment

plant units when suitable flow characteristics have been

developed. Application of the sewage to the trickling filter

media shall be continuous. Consideration shall be given to a

piping system which will permit recirculation during periods

of low flow.

CS901-3.3 Hydraulics: All hydraulic factors involving proper

distribution of sewage on the trickling filters shall be

carefully calculated. For reaction type distributors, a

minimum head of 24 inches between the low water level in siphon

chamber and the center of the distribution arms is generally

desirable.

CS901-3.4 Clearance: A minimum clearance of six inches between

media and distributor arms shall be provided. Greater

clearance will be necessary in climates where icing occurs.

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CS901-4 Media

CS901-4.1 Quality: The media shall consist of plastic materials which

are durable, resistant to spalling or flaking, and insoluble in

sewage.

CS901-4.2 Media Physical Properties: Media dry specific surface area

shall be 25 to 35 sq.ft./cu.ft. Void space shall be 95 to 97

percent.

CS901-5 Underdrainage System

CS901-5.1 Arrangement: Underdrains with semi-circular inverts or

equivalent should be provided and the underdrainage system

shall cover the entire floor of the trickling filter.

CS901-5.2 Slope: The underdrains shall have a minimum slope of one

percent. Effluent channels shall be designed to produce a

minimum velocity of two feet per second at average daily

rate of application to the trickling filter.

CS901-5.3 Flushing: Provision should be made for flushing the

underdrains. In small trickling filters, use of a peripheral

head channel with vertical vents is acceptable for flushing

purposes. Inspection facilities should be provided.

CS901-5.4 Ventilation: The underdrain system,effluent channels, and

effluent pipe should be designed to permit free passage of

air. The size of drains, channels, and pipe should be such

that not more than 50 percent of their cross-sectional area

will be submerged under the design hydraulic loading.

Blowers may be necessary to ensure adequate ventilation.

CS901-6 Special Features

CS901-6.1 Recirculation: Design of the recirculation process shall be

such that it occurs automatically at a predetermined low

flow.

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CS901-6.2 Maintenance: All distribution devices, underdrains, channels,

and pipes shall be described with the necessary provisions to

be properly maintained, flushed, or drained.

CS901-6.3 Flow Measurement: Devices shall be provided to permit

measurement of flow to trickling filter whenever recirculation

is used.

CS901-7 Two-Stage Towers

The foregoing standards shall also apply to second stage

towers.

CS902 ACTIVATED SLUDGE

CS902-1 Applicability

The activated sludge process may be used where the sewage

entering the aeration tanks is amenable to biological

treatment. The processes may be one of the following

types; conventional, extended aeration, step aeration, or

contact stabilization.

CS902-2 Unusual Installations

Design data outlined herein are presumed to achieve a

removal of 90% or more of BOD and suspended solids.

Lesser removals are not acceptable. Plans for treatment

plants contemplating abnormal concentrations of sewage

constituents, unusual aeration periods or special equipment

or arrangements of equipment will be reviewed on the merits

of the proposed system and will be considered upon

presentation of appropriate supporting data demonstrating

the efficiency of the design for the specific project.

CS902-3 Primary Treatment

Primary treatment shall be provided for activated sludge

processes as set forth in section CS700. Re-aeration of the

return sludge shall be provided for all contact stabilization

processes.

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CS902-4 Clarification

See Section CS704.

CS902-5 Aeration Tanks

CS902-5.1 Number of Units: Total aeration tank volume required shall

be divided among two or more units, capable of independent

operation.

CS902-5.2 Capacity: The capacity of the aeration tanks shall be based

on the following criteria:

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Designs predicated upon reaeration of return sludge or upon

controlled ratios of mixed liquor concentrations to the plant

loadings may be acceptable, where adequate supporting data

substantiating the adequacy of the design is furnished. Such

data shall have been included in the engineer\'s report (DDR).

CS902-5.3 Dimensions: Dimensions and proportions of each

independent unit shall be such as to maintain effective

mixture and utilization of air, to prevent unaerated sections

and noticeable channeling, and to prevent deposition of

solids. Ordinarily, aeration basin mixed liquor depths will be

not less than ten nor more than fifteen feet.

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CS902-5.4 Inlets and Outlets

A. Controls: Inlets and outlets for each aeration tank unit

shall be suitably equipped with valves, gates,

adjustable weirs or other devices to permit controlling

the flow to any unit and to maintain a reasonably

constant water level. The hydraulic properties of the

system shall be such as to permit the maximum

instantaneous hydraulic load to be carried with any

single unit out of service.

B. Ports: The velocity through ports or other inlets shall

be as low as practicable to prevent hydraulic short

circuiting.

C. Channels: Channels and pipes carrying liquids with

solids in suspension shall be designed to maintain

self-cleansing velocities or shall be agitated to keep

such solids in suspension at all rates of flow within the

design limits.

CS902-6 Measuring Devices

Devices for indicating rates of flow of return-sludge shall be

installed. These devices shall also totalize and record as

well as indicate flows.

CS901-7 Air Supply

CS902-7.1 Application: The design shall provide for the introduction of

air in sufficient volume and in such manner as to:

A. Maintain at least two ppm of dissolved oxygen under

all conditions of loading in all parts of the aeration

tanks except immediately beyond the inlets.

B. Maintain sufficient velocity of movement or turbulence

to bring sludge particles into intimate contact with all

portions of the sewage.

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C. Prevent deposition of solids in any part of the aeration

basin.

CS902-7.2 Air Diffusion and Piping Capacity: The air diffusion and

piping system shall be designed as to be capable of delivering

150% of normal air requirements. Normal air requirements

shall not be less than 1500 cubic feet per pound of applied

primary effluent BOD per day for conventional, step aeration

and contact stabilization processes, nor less than 2000 cubic

feet per pound for extended aeration.

CS902-7.3 Blowers: Nominal blower capacity shall be provided to

deliver air equal to the aeration basin requirements plus

whatever air may be required to supply channels, sludge

pumps, or other air-use demands. Blowers shall be provided

in multiple units so arranged and in such capacities as will

meet the maximum air demand with the single largest unit

out of service. The design should provide for variation in the

volume of air to be delivered, in at least three steps, and, as

near as practicable, following the load demand of the plant.

CS902-7.4 Air Cleaners: Air filters shall be provided on all blower

intake pipes.

CS902-7.5 Sound Attenuation Measures: All compressors or blowers

shall be provided with sound attenuation measures. Such

compressors or blowers shall be located away from

residential construction in a sound attenuating structure such

as a concrete block walled area (4\'-6\' high with cores filled)

or building.

CS902-8 Air Diffusers

CS902-8.1 Removal of Diffusers: Aeration diffusers or other equipment

used for introduction of air to mixed liquor shall preferably

be so designed as to permit removal for inspection, maintenance

and replacement without necessity for dewatering the tank.

In installations having one aeration unit, such provision shall

be mandatory.

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CS902-8.2 Air Control Valves: Individual assembly units of diffusers

shall be equipped with control valves preferably with

indicator markings for throttling and for complete shutoff.

Diffusers in any single assembly shall have a substantially

uniform pressure loss.

CS902-9 Mechanical Aerators

CS902-9.1 Other Aeration Facilities: Where designs provide mechanical

apparatus other than, or supplementary to, compressed air as

a means of flocculating; oxidizing and aerating the mixed

liquor, the same objectives as specified under \"Air Supply\"

(CS902-7) shall be provided for. Such devices shall maintain

these objectives when operating under all load conditions.

CS902-9.2 Spare Mechanism: A uninstalled spare aeration mechanism

shall be furnished for single unit installations.

CS902-10 Drains

Aeration tank drains shall be provided for all units. Such

drainage shall be discharged to the head of the plant.

CS902-11 Sludge Handling Equipment

CS902-11.1 Pump Capacities: For installations proposing to treat sewage

of normal characteristics, return activated sludge pumps shall

be provided with variable combined capacity ranging from

10% to 100% of the design flow. In addition, a standby unit

equal in capacity to the largest single pump shall be provided.

CS902-11.2 Installation Detail: A positive head should be provided on
the

pump suctions. Pumps should have at least a three inch and

preferably a four inch suction and discharge. Piping shall not

be less than four inches in diameter.

CS902-11.3 Waste Sludge Facilities: Waste Sludge control equipment

and piping should be designed for an adjustable capacity of

0-500% of the design waste sludge volume. Devices for

indicating rate of waste sludge discharge shall be provided.

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Indicating, recording, and totalizing devices are desirable and

should be included.

CS902-11.4 Return Sludge Facilities: Suitable devices for readily

observing, sampling, controlling, and apportioning return

activated sludge shall be provided.

CS902-11.5 Disposal of Waste Sludge: Waste activated sludge may be

returned either to the primary tanks, thickening tanks,

digestion tanks or other sludge handling units.

CS903 FILTRATION

CS903-1 Use

Slow sand filters shall be provided following all waste

stabilization ponds when necessary to meet required water

quality objectives. The use of subsurface or covered sand

filters is not recommended. The use of filters for raw or

settled sewage is not allowed.

CS903-2 Filter Loading: Filter loading shall not exceed 10 gpd/sq.ft.

CS903-3 Number of Units: Two or more filter units shall be provided

for all installations.

CS903-4 Media

CS903-4.1 Gravel Base: Clean graded gravel, preferably placed in a

least three layers, should be placed around the underdrains

and to a depth of at least six inches over the top of the

underdrains. Suggested gradings for the three layers

bottom-to-top are 1-1/2\" to 3/4\", 3/4\" to 1/4\", and 1/4\" to

1/8\".

CS903-4.2 Sand: At least 24 inches of clean sand should be provided.

For open filters dosed by flooding, the effective size shall be

0.3 to 0.6 mm; for filters dosed by rotary distributors, the

effective size shall be 0.4 to 1.0 mm. The uniformity

coefficient shall not be greater than 3.5.

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CS903-5 Dosing

CS903-5.1 Duplicate Units: Two or more dosing siphons (or dosing

pumps) shall be provided.

CS903-5.2 Volume: The dosing tank volume shall be such that any filter

bed will be covered to a depth of 2 to 4 inches by each dose.

CS903-5.3 Siphons or Pumps: Siphons or pumps shall have a discharge

capacity at minimum head at least 100% in excess of the

maximum rate of inflow to the dosing tank and at average

head, at least 90 gallons per minute per 1000 square feet of

filter area.

CS903-5.4 Discharge Lines: The discharge lines to the beds shall have

sufficient capacity to permit the full rated discharge of the

siphons or pumps.

CS903-6 Distribution

CS903-6.1 Arrangement: Troughs or piping may be used for distribution

of the treated sewage over the filter surface and should be

so located that the maximum lateral travel is not more than

20 feet.

CS903-6.2 Splash Slabs: Splash slabs shall be provided at each point of

discharge.

CS903-6.3 Drain: A drain opening from troughs or discharge piping shall

be provided.

CS903-7 Underdrains

Perforated PVC or vitrified clay underdrains may be used.

The underdrains should be sloped to the outlet and spaced

not to exceed 10 feet centers.

CS903-8 Earth Base

The earth base of the filters should be sloped to the trenches

in which the underdrains are laid. Sand filters in highly

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permeable soils shall have clay or plastic liners installed to

prevent excessive infiltration into the groundwater system.

CS1000 DISINFECTION

CS1001 GENERAL

Disinfection of the effluent shall be provided where required

by the U.S. Environmental Protection Agency or their

delegated regulatory agency. The use of chlorine gas or

hypochlorites shall be utilized if other methods of

disinfection such as ultra violet light (UV) or ozonation are

not feasible. Whichever method is selected, consideration

should be given to back-up or redundant equipment.

CS1002 ULTRAVIOLET LIGHT (UV)

CS1002-1 Applicability: The use of UV disinfection systems are

desirable since no chemical residuals remain as by-products

of the disinfection process. UV systems may be utilized only

when effluent clarity is sufficient to allow adequate light

penetration. UV systems are typically limited to wastewater

treatment systems which utilize sand filtration.

CS1002-2 Design Criteria: The values for design parameters will vary

between manufacturers. However, all designs should

account for the following factors:

A. Reduction of UV transmissivity with increasing

turbidity.

B. Decline of UV output of lamps with time.

C. Increased flow rate results in decreased UV contact

time.

D. Level of Total Suspended Solids.

E. Effluent Limits.

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CS1002-3 Duplicate Systems: Duplicate systems shall provide standby

capacity of 100%.

CS1003 OZONATION

CS1003-1 Applicability: Ozone may be produced from either air or

oxygen gas sources. Ozonation devices shall be

automatically controlled to adjust ozone production to meet

demand.

CS1003-2 Design Criteria: The values for design parameters will vary

between manufacturers. However, all designs should

account for the following factors:

A. Flow rate.

B. Nature and concentration of influent contaminants.

C. Ozone contact time.

D. Effluent limits.

CS1003-3 Duplicate Systems: Duplicate systems shall provide standby

capacity of 100%.

CS1004 CHLORINATION

CS1004-1 Equipment: The use of equipment designed to feed chlorine

gas in solution is recommended.

CS1004-2 Housing: The chlorinator building or room shall have ample

forced air ventilation with heating facilities. If gas

chlorination equipment and chlorine containers are to be

placed in a building used for other purposes, a gas-tight

partition should separate the chlorine room from any other

portion of the building. Doors should open only to the

outside of the building.

CS1004-3 Capacity of Chlorinator: Chlorinator capacities required will

vary depending on the use and point of application of the

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chlorine. For disinfection, the capacity should be adequate

to produce a residual of 5.0 ppm in the final effluent.

CS1004-4 Contract Period: After thorough mixing, a minimum contact

period of not less than 30 minutes at average daily flow or

maximum rate of pumpage shall be provided for disinfection.

The chlorine contact tank should be constructed to reduce

short circuiting of flow.

CS1005 DECHLORINATION

To achieve the required chlorine reduction, the preferred

method of dechlorination is aeration. If effluent aeration is

not feasible, dechlorination equipment and chemicals may be

required. Chemical addition of sulfur dioxide, sodium

metabisulfite or other acceptable reducing agent or activated

carbon may be used.

CS1005-1 A final chlorine residual of 0.1 mg/l or less in the treatment

plant effluent must be achieved.

CS1100 WASTE STABILIZATION PONDS

CS1101 EXHIBITS

All of the exhibits required for the various states of

processing as described in \"Submission of Exhibits\" shall be

submitted when applicable. In addition the following exhibits

will be required during the Preliminary Planning Stage:

A. The results of at least 3 soil borings per acre of basin

floor area.

B. A detailed discussion of the soils where the basin floor

will be constructed and of the embankment materials.

C. The soil borings are required to determine if the soil is

sufficiently impermeable to preclude excessive liquid

loss by percolation and is suitable for embankment

construction. Soil borings should extend to a depth of

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at least one foot below the proposed finish basin floor

elevation and samples should also be taken where

significant soil changes are noted. Soil samples should

be analyzed and the soil groups reported in accordance

with the Unified Soil Classification System. Additional

soil borings should be made where the original boring

data indicates that the suitability of the soil is

questionable. Should existing soils be incapable of

reducing percolation rates to 1/8-inch per day or less,

membrane liners or off-site clay must be used.

CS1102 AREA REQUIRED

CS1102-1 Clear Area

The site should be large enough to maintain a clear

unobstructed, undeveloped area that will extend a minimum

distance of 300 feet in all directions from the nearest edge

of the basin embankments. Consideration should be given to

any proposed basin expansion or the future addition of cells

when laying out this distance.

CS1102-2 Expansion Possibilities

The site should include sufficient area for expansion of the

original pond basin or for the construction of additional cells

where the complete treatment facilities are to be built in

stages or where land is available for future development.

CS1103 LOCATION

CS1103-1 Distance from Habitation

The site selected should be suitable for sewage stabilization

basin operation without adversely affecting existing or

proposed residential properties from an aesthetic standpoint

or by reason of possible odors.

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CS1103-2 Prevailing Winds

Wherever practical, stabilization basins should be located so

that the local prevailing wind will direct sewage odors away

from residential developments.

The design should provide a water surface elevation that will

utilize the maximum wind action for mixing and dispersing

the sewage solids from the inlet toward the basin periphery.

CS1104 BASIS OF DESIGN

CS1104-1 Surface Area and Loadings

The maximum stabilization basin loading should be

approximately 50 properties per acre of liquid surface. The

average loading should be approximately 35 properties per

acre of liquid surface.

Note: Ideal climate conditions in some sections of the

nation may be conductive to higher loadings than

50 properties per acre. In these cases the higher

loadings may be justified if experience has

shown that satisfactory treatment has been

demonstrated with existing stabilization basin

installations. Care should be exercised in

determining if the higher loadings should be

used. The HUD-FHA field environmental

engineer should be consulted in this matter.

CS1104-2 Industrial Wastes

Where commercial or industrial wastewater is to be

combined with residential sewage, the maximum of 50

residencies per acre of liquid surface in the stabilization

basin should be decreased according to the strength of the

commercial or industrial wastes. To arrive at the maximum

loading under these circumstances, the strength (BOD) of the

commercial or industrial sewage can be determined, or

estimated if necessary, and converted to the equivalent

number of residences using a minimum of 4 persons per

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residence and a daily loading or 0.17 pounds BOD per

person. (0.7 lbs./dwelling.)

CS1104-3 Multiple Units

The initial construction of stabilization basins may include

multiple cells in series where a greater degree of treatment is

necessary or is required by state or local authorities. For

this type of construction, the first cell should be designed on

the basis of 50 residential connections per acre of liquid

surface. The maximum number of residential connections per

acre of liquid surface should be decreased if commercial or

industrial wastes will be combined with residential sewage.

The maximum loading should be computed in accordance with

the preceding paragraphs.

CS1104-4 Polishing

Where it is necessary to use stabilization ponds for further

treatment of effluent from other type sewage treatment

works the surface area of the basin (acres of liquid surface

required) should be based on a determination of the BOD

removal of the pretreatment works. The actual BOD loading

for further treatment can be determined from a review of the

detailed plans and specifications for proposed pretreatment

sewage works construction and from a review of operating

records and/or design plans and specifications for existing

pretreatment works of the type proposed.

CS1104-5 Pond Shape

To the extent possible, all stabilization basins should be

oval, rectangular, square or circular in shape. Islands within

embankment boundaries and coves or peninsulas along the

embankments are not allowed.

CS1105 POND CONSTRUCTION DETAILS

CS1105-1 Basin Floors

CS1105-1.1 Uniformity: The basin floors shall be level.

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CS1105-1.2 Vegetation: All existing vegetation should be completely

removed from the soils to be used for pond bottoms or dikes.

CS1105-1.3 Soils: Soils conforming to the following Unified Soil

Classification groups are suitable materials for the basin

floor when combined with adequate amounts of suitable clay

material:

GC, SC, CL, and CH

All other soil groups shall require membrane liners or

adequate clay blankets.

For further reference to the Unified Soil Classification System

see FHA Publication No. 373, Engineering Soil Classification

for Residential Developments or ASTM D 2487.

Classification of soils for engineering purposes.

CS1105-1.4 Where sealing of the basin floor is required, the

specifications should state the thickness of clay cover, and

should provide for soil compaction, to achieve the percolation

rates shown in CS1101.C. The specifications should also

describe the manner in which the seal materials are to be

placed, the depth of sealing material and the type of

compaction equipment to be used.

CS1105-2 Embankments

CS1105-2.1 Foundations: The natural or undisturbed soil underlying a

proposed embankment location should be impervious to the

extent shown in CS1110.C. If the natural soil does not meet

these requirements, membrane liners or adequate clay

material shall be used.

CS1105-2.2 Cores: Where it is determined that the construction of a core

is necessary, the specifications should provide for soil

compaction to conform, insofar as practicable, with

significant groups in the Unified Soil Classification System.

The manner in which the soil is to be placed in the core and

the type of compaction equipment to be used should also be

described.

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CS1105-2.3 Embankment Materials: Soil groups GM, GC, SM, and SC

are good materials for constructing the embankments. The

ML, CL, MH, and CH groups should be used in combination

with the above groups. It should be emphasized that the

GW, GP, SW and SP groups are not satisfactory materials

when used alone. Specifications for embankment

construction should include information on method of placing

and compacting fill and on the equipment to be used as well

as the need for a membrane liner or clay blanket.

CS1105-2.4 Top Width: A minimum top width of 8 feet should be

provided.

CS1105-2.5 Slopes: The maximum slope of the embankments should not

exceed 3 horizontal to 1 vertical.

CS1105-2.6 Freeboard: The minimum recommended freeboard is 2 feet.

CS1105-2.7 Liquid Depth

A. The minimum normal liquid depth should be 2-1/2 feet.

B. The maximum normal liquid depth should be 4 feet.

CS1105-2.8 Protection of Embankments: Embankments should be seeded

above the water level. Only shallow root crops will be

effective for this purpose as the use of long root grasses may

cause sewage to seep through the embankment. Concrete

or asphalt splash protection shall be provided completely

around the pond extending at a minimum from two feet

above the high water line to two feet below the low water

line.

CS1105-3 Influent and Effluent Lines

CS1105-3.1 Materials: Ductile iron pipe shall be used for the influent

and effluent piping.

CS1105-3.2 Line and Grade: The influent and effluent line design with

respect to grade and diameter should conform to generally

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accepted engineering practice. A minimum velocity of 2 feet

per second shall be provided.

CS1105-3.3 Point of Discharge: The influent line and the outlet should
be

located so as to minimize short-circuiting of the incoming

sewage flowing through the pond.

Where practical the discharge end of the influent line for

rectangular and oval basins should terminate approximately

one-third the distance between the influent end and the

outlet structure and at the center of circular or square

basins. Variances in this requirement may be satisfactory

where modification in the shape of the basin is considered

necessary.

CS1105-3.4 Discharge Apron: The discharge end of the influent line

should be laid on an adequately designed concrete slab. A

30 inch square minimum area is recommended.

CS1105-3.5 Interconnecting Piping: Where multiple cells are used,
ductile

iron inlet piping to successive cells may be installed through

the separating embankments.

CS1105-4 Outlet Structure

CS1105-4.1 Outlet Geometry: The outlet structure design should provide

for operating the stabilization basin at depths between 2-1/2

and 4 feet. The effluent should be removed at a depth

between 6 and 12 inches below the operating water level.

Various appurtenances may be used to accomplish this

depending on the outlet structure design. These

appurtenances may include weirs and baffles or pipe fittings

such as tees, ells and pipe extension rings.

CS1105-5 Miscellaneous

CS1105-5.1 Fencing: The entire basin area shall be fenced with eight

foot (min.) fence. Warning signs to clearly indicate the type

of utility shall be posted.

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CS1105-5.2 Access Road: An all-weather road to the basin site should be

provided and should extend to the toe of the embankment at

one or more points. Ingress and egress rights should be

required if the site is not contiguous with public property.

CS1105-5.3 Limiting Use: Stabilization basins should not be used for the

treatment of storm drainage system wastes.

CS1105-5.4 Polishing Filters: Were required by the U.S. Environmental

Protection Agency or their delegated state regulatory agency,

all ponds shall be followed by slow sand filters as provided

in CS903.

CS1106 AERATED PONDS

CS1106-1 Basin of Design

Aerated ponds shall be designed with a minimum hydraulic

retention time of 5 days. Longer times may be required in

colder climates.

CS1106-2 Mixing

Aerated ponds shall be adequately mixed to evenly diffuse

oxygen throughout the pond. A mixing power input range of

0.5 - 1.0 hp per 1000 cu. ft. of pond volume is

recommended.

CS1106-3 Dissolved Oxygen

Aerated ponds shall be maintained at dissolved oxygen levels

above 2 mg/l. This oxygen may be supplied by diffused air

or mechanical aerators.

CS1106-4 Velocity Gradient

A minimum velocity gradient of one foot per second shall be

maintained throughout the aerated pond.

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CS1106-5 Supplemental Treatment Processes

Aerated ponds may be followed by non-aerated polishing

ponds, clarifiers, filters and/or other such processes.

CS1106-6 Construction

Construction of aerated ponds shall be in accordance with

Section CS1105, Pond Construction Details.

CS1106-7 Operation and Maintenance

Pond design shall allow for expected operation and

maintenance activities, including: pond access, influent

structure access, effluent structure access, and aeration

system access.

CS1200 LAND APPLICATION SYSTEMS

CS1201 GENERAL

CS1201-1 Feasibility

The feasibility assessment of land application systems shall

be based on soil permeability, wastewater quality, and

discharge quality criteria. For any proposed site, the soil

permeability must be determined and feasibility judged based

on the operating requirements and performance of each land

treatment option.

CS1201-2 Approved Methods

The following methods of land application are approved for

consideration: spray irrigation, overland flow, rapid

infiltration, and constructed wetlands. These systems are

approved only for municipal wastewater.

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CS1201-3 Holding Ponds

CS1201-3.1 Construction: The methods of construction shall be the

same as that required for waste stabilization ponds (see

Section CS1100).

CS1201-3.2 Size: Holding ponds shall be sized such that with any

combination of equipment outages or inclement weather

which prohibits spraying, adequate storage will be available

for the treated effluent from the treatment works. Water

balance storage calculations over a 12-month period shall

have been addressed in the Engineer\'s Report (DDR). Not

less than two weeks storage shall be provided.

CS1201-4 Pumping

CS1201-4.1 The requirements of Section CS500 sewage pumping

stations shall also apply to this section.

CS1201-4.2 Pumping Station: The pumping station shall contain:

A. An in-line meter to measure the amount of effluent

pumped.

B. Pressure instruments with high and low signaling

devices to close system valving or shutdown pumps

due to line failures or over pressurization on any

portion of the system.

CS1201-5 Land Rights

Proof of a recorded fee simple deed or easement for the land

dedicated to wastewater disposal by land application must be

provided. Additionally, the holder of the fee simple title or

easement to the land shall provide adequate assurances to

HUD-FHA that the land or easement will not be conveyed or

divested so long as the land is needed for wastewater

disposal, unless such conveyance or divestiture is to a new

owner who shall assume full responsibility for wastewater

treatment as provided in this Handbook.

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CS1202 SPRAY IRRIGATION

CS1202-1 Description: Spray irrigation consists of spray irrigating

land with treated wastewater effluent. The spray application

zones must have live vegetation capable of assimilating the

moisture and nutrients.

CS1202-1.1 Design Criteria: In-depth soils testing shall be accomplished

in order to:

A. Ensure that soils are not excessively permeable so as

to allow sprayed effluent to reach shallow groundwater

tables before vegetative root systems can accomplish

their biological uptake, and

B. Ensure that soils will be adequately permeable so as to

prevent effluent runoff or ponding.

CS1202-1.2 Irrigation Frequency: Spray distribution zones shall be

irrigated no more than once per week. Five days spraying

per week, is recommended. Buffer areas shall be included.

CS1202-1.3 Spray Application Loading: Dependent on soils and

vegetation, loadings may vary from 0.25 inches to 6.0 inches

per week over the entire application area. Rates of 0.1 to

1.0 inches per hour may be used. Generally an eight hour or

less spraying time should be considered to take advantage of

evaporation and daylight.

CS1202-1.4 Slopes: Slopes should not exceed 15 percent although in

forested areas and for some crops up to 30 percent slopes

may be acceptable.

CS1202-1.5 Crops: Where crops are grown to provide the biological

uptake from the treated wastewater, rotation of both fields

and crops must be considered due to crop growing and

harvesting seasons where for a time, fields may be out of

service for spraying. Disposition of the harvested crop shall

be considered.

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CS1202-1.6 Trees and Golf Courses: Both trees and golf courses are

approvable for spray fields. Golf courses may also require a

potable water or surface water (pond or lake) system in

addition to the treated effluent system.

CS1202-1.7 Buffers: The following minimum buffers shall be provided:

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CS1202-2 Spray Field Equipment

CS1202-2.1 Piping: Portable, center pivot and solid set buried piping

systems are the most common. For all climates and

conditions the solid set buried system is recommended

herein. Risers generally should be no more than 4 feet in

height with adequate post support and bracketry up to the

nozzle.

Ductile iron or pressure class PVC is recommended for spray

irrigation piping systems. Velocities in the pipe network

should be between 2 and 8 feet per second. Valving for field

or segment isolation shall be manual.

The piping grids should be designed for optimum sprinkler

location and equal pressure distribution. A pressure

differential of less than 20% in any field is desired.

Pressure

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differentials which exceed 20% shall be justified by showing

that the necessary site grading to achieve a 20% differential

is not practical and that spray patterns have been adjusted to

take into account the pressure differentials. However, in no

case shall pressure differentials exceed 40% in any field.

CS1202-2.2 Nozzles: Nozzle orifice, pressure and flow shall be

determined by application rate, size of field, sprinkler

overlap, type of vegetation and wind velocity and consistency.

CS1203 OVERLAND FLOW

CS1203-1 Description: This system consists of applying wastewater to

gently sloped terraces and allowing it to flow over vegetated

surfaces to collection ditches.

CS1203-2 Design Criteria: Application shall be either by direct surface

application or by sprinkler system. The area shall be

sufficiently sized to allow 16 to 110 acres per MGD.

Wastewater application shall not exceed 6 inches per week

for screened wastewater or 16 inches per week for

secondary effluent. Special care shall be exercised in design

to ensure uniform sheet flow over the flow area.

CS1203-3 Preapplication Treatment: Minimum preapplication treatment

shall consist of solids removal.

CS1203-4 Construction: During construction special care shall be

exercised to ensure uniform sheet flow in accordance with

system design.

CS1204 RAPID INFILTRATION

CS1204-1 Description: Rapid Infiltration (RI) consists typically of

earthen basins which allow wastewater infiltration into the

soil followed by percolation, either vertically or laterally,

away from the application point.

CS1204-2 Design Criteria: The minimum land area requirement for a RI

system shall be determined by:

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(0.0365) Q

A = \_\_\_\_\_\_\_\_\_\_

L

Where:

A = treatment area

Q = design daily flow, m3/d

L = annual percolation rate, m/yr

Typically, land area should be 2 to 56 acres per MGD.

Where RI percolate does not satisfy state groundwater

quality requirements, the percolate shall be collected by

underdrains for re-use or surface discharge.

Wastewater application shall be by direct surface application.

CS1204-3 Site Selection: The following parameters must be defined

prior to determining a site to be suitable for a RI system:

general hydrological setting, soil descriptions and water table

locations, proposed soil layer for RI basin, groundwater flow

characteristics, and necessary site modifications

(underdrains, fill, etc.).

CS1205 CONSTRUCTED WETLANDS

CS1205-1 Description: Constructed wetlands consist of flooded

meadows and marshes, and usually include a pond.

CS1205-2 Design Criteria: Required land area for constructed wetlands

shall be between 11 and 280 acres per 1 MGD. Wastewater

shall be applied by either sprinklers or direct surface

application. Application shall not exceed 25 inches per

week. Finished grade shall not exceed 5%.

CS1300 ONSITE WASTEWATER TREATMENT AND DISPOSAL

SYSTEMS

CS1301 GENERAL

Where connection to a public sewer system is not feasible,

the following types of onsite treatment shall be allowed:

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septic tank with leaching system, sand filters or mounds, and

evapotranspiration ponds.

CS301-2 Leaching Systems shall be installed in accordance with local

requirements.

CS1302 SEPTIC TANKS

CS1302-1 Septic tanks shall be buried and watertight. All septic tank

systems shall be located and installed in accordance with

local health and environmental regulations.

CS1302-2 Septic tanks shall have a minimum 8 hour retention time.

Tanks shall have inlet and outlet devices which prevent the

discharge of sludge and scum with the effluent. Septic tanks

shall be vented to permit the escape of gases.

CS1302-3 Septic tanks for residential units shall have the following

minimum size:

1 - 2 bedrooms 750 gal

3 bedrooms 900 gal

4 bedrooms 1000 gal

5 bedrooms 1200 gal

each additional 250 gal

Where local codes require larger sizes, the local code shall

prevail.

CS1302-4 Where septic tanks are to be installed for multiple homes,

they shall be sized based on total flow. For flows between

750-1,500 gpd, the tank capacity shall be 1.5 times daily

volume flow. For flows between 1,500-15,000 gpd,

minimum tank capacity shall be equal to 1,125 gallons plus

75% of dally flow.

CS1302-5 Septic tank systems shall include one of the following

subsurface wastewater disposal systems: leaching fields,

sand filters or mounds.

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CS1303 INTERMITTENT SAND FILTERS

CS1303-1 Intermittent sand filters may be used for polishing of septic

tank effluent prior to discharge.

CS1303-2 Media shall be sized to obtain the desired flow rate.

However, not more than 1 % of the media shall be smaller

than 0.13mm. Typical media range from 0.25mm to 1.5mm,

with a uniformity coefficient not more than 4.0. Allowable

media materials are: sand, anthracite, garnet, ilmenite and

activated carbon.

CS1303-3 Filters shall be sized to allow 0.75 to 2.0 gpd per square foot

of filter area. Wastewater should be applied to flood the

surface of the filter to a minimum depth of 3 inches.

CS1303-4 Intermittent Sand Filter Systems shall be followed by a

leaching system or mounds.

CS1304 MOUNDS

CS1304-1 Mounds shall be installed in conjunction with septic tank

systems only in well drained areas with the following

maximum slopes:

Percolation Rate Maximum Slope

\< 60 min/in 6%

\> 60 min/in 12%

CS1304-2 Mounds shall be located in accordance with local health and

environmental codes.

CS1304-3 Mound system influent shall be anaerobically treated

wastewater free of settable solids and greases.

CS1304-4 Mounds shall be of the following minimum dimensions:

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Mound Height Dimension

Fill Depth 1 ft (minimum)

Absorption Bed Depth 1 ft (minimum)

Cap at Edge of Bed 1 ft

Cap at Center of Bed 1.5 ft

Side Slope \< 3:1

CS1305 EVAPOTRANSPIRATION PONDS

CS1305-1 Evapotranspiration ponds shall be designed for zero discharge

in 10 years.

CS1305-2 All evapotranspiration ponds shall be provided with an

impervious liner.

CS1305-3 All ponds shall be designed using local weather data for pan

evaporation and precipitation. All pond designs shall account

for wastewater flow and precipitation.

CS1305-4 Synthetic pond liners shall be minimum 10 mil, with 2 inch

sand cushion on both sides.

CS1305-5 Surface runoff from adjacent areas shall be diverted around

the pond.

CS1400 ALTERNATIVE OR INNOVATING TECHNOLOGY

CS1401 GENERAL

Wastewater transport or treatment involving alternative

and/or innovative technology will be considered by HUD-FHA

on a case-by-case basis. All the relevant requirements of this

Handbook shall be met. Additionally, not less than one

successful installation of the proposed technology shall be

documented and demonstrated. Technology which may be

considered under this paragraph include aquaculture

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4940.3 Rev-1

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treatment systems, recycling, curved sewers, and pressure

sewer systems.

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\* U.S. G.P.O.:1993-342-362:80020

HUD-Washington, D.C.