Category Housing and Urban Development


The city of Lacey requires a 10-foot separation between public water and public sewer, a state and local code provision. When a sewer lateral crosses a water main or vice-versa, a З-foot vertical separation must be maintained. This occurred in The Park, but Phillips was unable to make the З-foot vertical separation.

Подпись: Lacey, Washington. EXAMPLES FROM THE DEMONSTRATION PROJECTSBecause of this, the city required a heavy gauge metal sleeve around the water pipe within 10 feet of the sewer. This apparently is a carryover requirement from the time of cast iron and concrete soil pipe, when joints often broke and leaked. However, with longer lengths of seamless PVC pipe available, the separation require­ments and the need for a metal sleeve appear to be unnecessary.

Подпись: Portland, OregonBuilders in Portland frequently install gas, electric, telephone, and TV lines in a common trench. In addition to allowing this practice, the city of Portland permitted Robinson to install his common trench and water line trench outside the right-of-way. The city also allowed the use of less expensive native backfill instead of off-site granular backfill. The city would not waive their normal require­ment that sanitary sewer mains be placed in a separate trench in the right-of-way. Robinson saved $5,040 by installing his common trench and water line trench outside the right-of – way and using backfill from the site.





One of the most prohibitive local residential land development regulations requires placement of all utilities in public rights-of-way. A viable, less costly alternative is installation of utilities outside of the ROW in easements.

Following are guidelines for utilities and utility easements:

• Place utilities in easements instead of rights-of-way where appropriate.

• Use plastic piping in underground gas systems.

• Install direct buried phone, cable TV and electric lines.

• Use common trenching for multiple utility installations.

Подпись: Easements/ Rights-of-Way Utility easements are an acceptable procedure in many areas of the country. Benefits of easements compared to rights-of-way are detailed in the Streets section. Specific to utilities, however, an easement often allows placement of a line in the shortest available path, decreasing the overall length of the line and reducing costs.


Home owners maintain and use easement areas, saving the locality money and adding land for the homeowners’ enjoyment. Legal rights to the easement land are assigned to the community, utility companies, and home owners.

Подпись: Materials Several non-traditional materials for use in sanitary sewers, stormwater systems, and water service are discussed in earlier sections. Gas, electric, and cable TV can also use more effective, less costly materials.

Plastic piping, usually polyvinyl chloride (PVC) or polyethylene (PE), is used in underground gas piping systems in lieu of the traditional black or galvanized steel, reducing costs and increasing ease of installation and corrosion resistance.

Direct-burial cable can be used for cable TV, phone, and electric lines, eliminating the need for a covering or conduit to serve as a protective sleeve. The National Electric Code (NEC) permits direct-burial cable when a minimum soil cover, or equivalent protection, is provided.

Подпись: InstallationCommon trenching of different combinations of utilities is becoming more acceptable. Common trenching of sanitary sewer and water lines is permitted by the major U. S. model building code organizations – ICBO, BOCA, SBCCI and CABO. Approxi­mately $5 per foot can be saved in installation costs of main lines, with a smaller savings of $2 per foot on service laterals. The water line is generally placed at least 12 inches above the sewer line, with a minimum horizontal separation of 18 inches. However, due to improved reliability in materials and construction techniques,


UTILITIES/UTILITY EASEMENTS Подпись: г [ЩіїШг^гг, = i(fsin=w=m-2jifHK(= iu~w-gl

Common water/sewer trench

local codes are beginning to recognize that minimum separation distances are unnecessary.

Common trenching is used successfully with electric, telephone, cable TV, and gas lines. The installation cost is reduced substantially if three or four utility companies share trenching expenses.

The city of Tacoma, Washington, estimates common trenching in residential areas reduces costs, an average of 97 cents per foot where electric, telephone, and cable TV are installed in the same trench. Seattle, Washington, reports savings of 40 percent to 60 percent.


Alternatives to traditional standards, materials, and procedures used in residential water supply systems are often more cost efficient.

Following are guidelines for water supply:

• Consider alternative materials for water mains and service pipes.

• Use multiple connections to one common service where feasible.

• Size water distribution pipes to meet the projected need.

• Substitute blow-off mechanisms for some, fire hydrants.

• Consider alternative meter arrangements.

Подпись: Water MainsПодпись: PVC pipeWATER SUPPLYPressure water pipe has been constructed of concrete, vitrified clay, lead, ductile iron, cast iron, asbestos cement, and wood. The newest material, plastic, most often in the form of polyvinyl chloride (PVC) or polybutylene (PB), has performed equally well or better than many of the more "traditional" materials.

PVC is relatively light weight, easier to install, more resistant to corrosion, and less expensive than many of the alternatives. An 8-inch PVC water main will save $2.00 to $2.50 per linear foot compared with an 8-inch ductile iron water main.

Most sizes of PVC pipe can be installed without the use of expensive machinery normally required to lower the pipe into a trench, since its relatively long lengths are easily balanced against its lighter per unit weight. PVC does not require complicated mechanical or glued joints. The bell and О-ring joints of standard PVC water pipe are wedged into place, saving material and labor costs.

An alternative to relatively expensive copper tubing for service lines is plastic tubing, usually manufactured from polyethylene (PE) or polybutylene (PB). Estimated savings of replacing 1-inch type К copper tubing with 1-inch plastic tubing is between $1.50 and $2.00 per linear foot.

Подпись: Water ServiceПодпись: ConnectionsAlthough local acceptance of plastic has been a slow process, both materials have been recognized under the major model plumbing codes. Available from most local suppliers, PB and PE have been rated at pressures well above those encountered in public water systems. Plastic tubing is flexible, lightweight, and easily joined with standard fittings. The relatively long lengths of most tubing insure that the number of joints will generally be limited to those at the main and the meter.

Saddle-type connections can be eliminated where a service line taps into the water main. A corporation stop assembly, used when tapping into ductile iron pipe, provides a complete, tight fitting connection without the saddle. The saddle adds $20 to $30 per tap, depending upon local factors. Crimping of tubing, especially near the tap, can be avoided by bedding the area within a foot or two of the connection with a local aggregate.




Service line connection to water main


Communities should reevaluate standards that require a separate tap for each residence. Тар-in costs can be reduced significantly by branching off a tap to service more than one building or home. Multiple connections to one common service are frequently used with no adverse impact on performance.

A single water service can be installed along the common property line of adjoining lots. A standard wye or tee is used to branch off the common line near the meter, reducing the number of taps by 50 percent. Trenching costs and maintenance costs are also reduced since only one line is installed for two homes.

Common water service lines can serve a number of homes in cluster or. townhouse developments. A larger branch than the typical 3/4-inch service line may be required if more units are to be served. Cost benefits of multiple service lines are directly proportional to the number of units each line serves.

Multiple connections to a single water service line

Подпись: Sizing Accessory Items Many communities’ standards require a 6-inch, 8-inch, or even 10-inch minimum diameter for water mains. This often produces an overdesigned system.

Residential water supply and fire flow requirements should determine the size of water distribution piping. These requirements can often be met on short runs with 2-inch to 4-inch water lines. A larger main is generally nearby if it is necessary to install a hydrant for fire protection.

Cost savings are estimated at $4.50 per foot when a З-inch line is used compared to a 6-inch line.

Cost effective materials and construction techniques can be applied to meters, valves, hydrants and fittings. ;

Fire hydrants are routinely installed at the terminal end of water lines and at low lying points where it may be necessary to blow off the line. A blow-off mechanism can be substituted for hydrants that are not required for fire protection, saving approximately $1,000 per hydrant. A standard 2- inch blow off is usually adequate and can be installed by extending the main I with a short section of 2-inch tubing.



Подпись: STANDARD Подпись: Exterior water meter
An outdoor type water meter enclosed in a plastic meter box eliminates both the remote reader and the curbstop shut-off commonly installed with an indoor water meter, saving approximately $60.

АІ a safeguard against freezing in colder climates, the top of the meter is covered and placed below iocal frost depth.

Multiple meters can be housed in a single box, especially efficient when multiple connections are made to a single tap.

Подпись: Charlotte, North CarolinaПодпись: Mesa County, ColoradoWATER SUPPLYПодпись: EXAMPLES FROM THE DEMONSTRATION PROJECTS
In Lynton Place, built by the John Crosland Company, two major revisions to the city’s water main construction standards were proposed and subsequently approved by the city.

The first revision permitted a substitution of PVC water pipe for the cluctile iron pipe (DIP) water mains usually required. The second change permitted a common service line to serve two homes. This variance, which eliminated the need for two individual taps (and one tap fee), was achieved through the installation of a single 1-inch service line in place of two 3/4-inch lines. The innovations to the water system resulted in a reduction in total costs of $8,310, a savings of approximately $554 per unit.

In Mesa County, Colorado, water service to an individual building is typically installed using asbestos cement pipe. The county allowed Roger Ladd and Company to use polybutylene water service lines at the Coventry Club subdivision, resulting in a total savings of over $3,100 or approximately $63 per unit.

Подпись: Portland, OregonWATER SUPPLYПодпись: Lacey, WashingtonMike Robinson, President of Black Bull Enterprises, proposed substituting PVC water mains in place of the standard DIP in the North Meadow Village demonstration subdivision, and downsizing the water main from 8-inch lines to 6-inch fire hydrant and 4-inch domestic water lines, depending on the location. The city allowed both deviations from existing standards and permitted the elimination of individual meters for each unit with the understanding that the home owners’ association would maintain the system as privately owned. Water lines outside of the ROW were allowed based on the private ownership of the system.

The total water distribution system savings at North Meadow Village were estimated at $1,283 per unit. This reduction was after the inclusion of a $72,500 lawn sprinkler system. Had the $72,500 been excluded from the demonstration cost calculations, savings reflected in the per unit cost would have increased significantly.

The city allowed John Phillips, the builder, to install water mains outside the rights-of-way as long as easements were provided and the mains were in reasonably accessible locations.

Подпись: Blaine, Minnesota Подпись: Burlington, VermontPhillips also hooked one water line into two, three, or four water meters, meaning one tap and one corporation stop would serve as many as four dwellings. By placing four meters on a single tap, cost per unit was reduced from $530 to $211. This technique was practical only because the units were grouped and clustered. Total water service costs were reduced over $40,000.

Good Value Homes (GVH),

"•builder/developer of the Cloverleaf Farm 9th Addition, installed a 11/2- inch diameter water supply line to each eight-plex unit instead of the normal 2-inch line.

GVH also clustered the shut-off valves in one central location, and installed one water meter per building instead of the typical one meter per unit.

William R. Hauke, Hauke Building Supply, was permitted by the city to use one water line for four units in his infill demonstration, saving approximately $3,000.

Plastic pipe was also used in the following demonstrations: Oklahoma City, Oklahoma; Everett, Washington; and Charlotte, North Carolina


Residential neighborhoods often have overdesigned, underutilized sewer systems which local officials must review for cost reduction possibilities. Various sanitary sewer system alternatives are available today to communities using traditional, outmoded procedures, designs, and materials.

Following are guidelines for sanitary sewers:

• Use curvilinear sewers where feasible.

• Increase maximum manhole spacing.

• Use cleanouts as an alternative to manholes for maintenance.

• Use plastic pipe instead of concrete or metallic pipe.

• When appropriate, use inside drop connections.

• Design sewer pipe size and slope to meet the need.

• Use "state-of-the-art" inspection procedures.

• Use common laterals.

Подпись: Manholes, Curvilinear Sewers, CleanoutsRequiring fewer manholes than the norm, encouraging curvilinear sewer designs, and allowing use of cleanouts can save money for developers, local governments, and home buyers. Curvilinear sewers reduce the total length of sewer pipe, but the greater savings are from a reduction of manholes at $1,000 to $1,500 each. Hydraulic performance within a sewer is not adversely affected by the curved sections.


Although many communities require that manholes be spaced at a maximum of 200 to 400 feet, many more places now permit spacings in excess of 600 feet, due to improved methods of maintenance and construction and equipment development. For example, flush trucks capable of cleaning sewer lines 600 to 800 feet in length are now standard equipment for many public works departments.

SANITARY SEWERSCleanouts can be provided in lieu of manholes both in curvilinear and straight runs. Cleanouts can also be installed at a much lower cost than a manhole at the terminal end of the sewer line. They offer a cost effective alternative in flood prone areas or in areas of high water tables because of installation, lower material costs, and better protection against infiltration.

Although cleanouts are a proven cost – effective alternative, manholes may still be required at a slope change or where multiple pipes converge.

Plastic pipe is being used in an increasing number of communities, offering reductions in material, installation, and replacement/main – tenance costs when compared to total costs of more "traditional" materials.

Подпись: Pipe Materials Подпись: Drop Inlets Polyvinyl chloride (PVC) is strong, lightweight, and considerably less expensive than concrete and metallic piping and has proven its durability and reliability over several decades of use in sanitary systems. Many of the early problems associated with PVC can be traced to improper bedding procedures. If the entire length of the pipe, including joints, is supported by the bedding materials, the pipe is secure. A clean, carefully placed backfill is also recommended.

Sewer designers and construction crews installing sanitary sewers must insure the continuous flow of waste­water through manholes, especially when significant elevation differences exist between the influent and effluent pipes. Most areas require an outside drop connection to convey wastewater across an elevation drop, a costly solution requiring added piping and concrete blocking. An inside drop connection is less costly because it requires less materials, is easier to install, reduces stress at the connec­tion and needs less excavation and backfill.


Inside drop manhole


Подпись: Design CriteriaA sanitary sewer must be designed to coordinate with a master plan for sewer extensions, which all commu­nities should have to ensure efficient integrated systems. Often, in lieu of a master plan, community standards arbitrarily require a minimum 8-inch diameter pipe. In many instances, especially on cul-de-sacs, deadends, and other areas where the sewer serves only a few houses, smaller pipes of 4 or 6 inch diameter actually provide better service because of faster flow. Larger pipe sizes may be detrimental since they could promote deposition of solids at low flows. A З-inch house lateral is generally sufficient for a single dwelling unit.

Sizing criteria should be evaluated to reflect actual conditions. In the past, 100 gpcd was considered the standard design flow from a dwelling. However, researchers have shown that 40 to 50 gpcd more accurately reflects typical average flows.

An "across the board" minimum slope cannot be applied to all pipe. The minimum slope required for a sanitary sewer should not be an arbitrary standard, but should be determined for a specific site. Flatter sloped sewers reduce trenching depth, a critical factor where bedrock or other obstacles exist.





Wastewater Flow

No. of



Range of

Indi vi dual


Resi dences



Residence Averages




Linaweaver, et al.




– 66

Anderson and Watson



44 (


– 69

Watson, et al. ‘





– 65

Cohen and Wallman





– 101.6






– 65.4

Bennett and Li nstedt





– 82.5

Siegrist, et al.




‘ 25.4

– 56.9

Oti s





– 71

Duffy, et al.




.Weighted Average


Source: On-Site Wastewater Treatment and Disposal Systems, U. S. EPA – 1980

Подпись:Подпись: Common LateralsTelevision cameras can locate leaks with a higher degree of accuracy than a visual inspection conducted by a maintenance crew because they actually travel the distance of the pipe. If combined with an effective maintenance program, T. V. inspections help to insure quality construction and indirectly result in savings in future repairs or replacement.

Common laterals can be used to connect the public sewer to more than one house, reducing total trench

Main Sewer Line



Подпись: Wye connection detail

Подпись: Multiple connections to a common sewer lateral

length and quantity of materials.

Since many communities charge fees based on the number of connections, additional savings come from the reduction in the number of connec­tions to the main.

Two adjoining lots can be serviced by one lateral installed along the common property line with an easement dedicated to insure access for maintenance and/or replacement. A standard wye fitting is installed at the junction of the individual building drains. Pipe length is decreased by almost 50 percent since every other lateral is eliminated.

Clusters and townhouses also adapt well to common laterals by connecting three or more units to a single line.

In any application of common sewer connections, benefits increase as the distance from buildings to public sewer increases.

Подпись: Source: Alternatives to Public Sewer, NAHB - 197Э Public Sewers An alternative to the traditional Alternatives high-cost public sewer system is the various on-site technologies currently available; the most typical is the conventional septic tank/soil absorption system.

Considered an excellent system if functioning properly, the septic system has several advantages: the need for a treatment plant is elimi­nated, sewer mains and pumping stations are eliminated, sewer tap fees are eliminated, and groundwater recharge is encouraged.

There is also a major disadvantage with septic systems: a large per­centage of soils in the U. S. are not suitable for this purpose.

On-site mound or fill systems are gaining acceptance across the nation in areas where soil conditions were previously considered "unsuitable."

Evapotranspiration systems, effective in semi-arid climates, "treat" septic tank effluent by discharging it into an evapotranspiration bed. The effluent is disposed of through evaporation and plant uptake. In community on-site systems, the land best suited for a soil


Source: Residential Wastewater Systems, NAHB – 1980




absorption system is reserved for the drain field. Effluent from each dwelling is pumped from (or flows from) an individual septic tank to the community drain field. Although the absorption area required for the system would be much larger than an individual drain field, it can be used for other purposes such as open space requirements.

Подпись: Lacey, WashingtonSANITARY SEWERSAt "The Park," John Phillips was allowed to use 6-inch diameter PVC branch sewer mains to serve 15 to 25 dwellings. The city normally requires 8-inch sewer mains.

Curvilinear sewer lines were used, allowing Phillips flexibility in serving more units with one lateral or branch feeder. Phillips used the PVC pipe manufacturer’s data for curving the pipe, and Lacey accepted the curved lines based upon the pipe manufac­turer’s recommendations.

Four-inch diameter PVC sanitary sewer laterals with 4-inch wyes to serve several detached and attached units were requested and approved. Major trenches and laterals were reduced by about 75 percent over conventional use. Although this was a one-time only approval, Phillips believes that with a good maintenance track record the method will be approved for general use. Total sanitary sewer costs were reduced by almost $61,000.

Подпись: Sioux Falls, South DakotaПодпись:SANITARY SEWERSRonning Enterprises, Inc., builder/developer of the Sioux Falls demonstration site, installed curvilinear sewers instead of straight-run sewers. Manholes were spaced approximately 460 feet apart, an increase over the Sioux Falls norm. Six additional manholes would have been necessary had the more traditional sewer system been used. This resulted in a savings of $6,000 or $80 per unit.

Standard spacing between manholes in Everett is 300 feet. City officials permitted a maximum distance of 600 feet at the Sunridge project, developed and built by Rich Boyden. Three manholes were eliminated for a total savings of about $3,500.

Increased manhole spacing was also permitted in Charlotte, North Carolina.

Cleanouts were allowed in place of normally required manholes in: Crittenden County, Arkansas; Christian County, Kentucky; and Portland,


Plastic pipe was permitted in: Charlotte, North Carolina; Oklahoma City, Oklahoma; White Marsh, Maryland; and Phoenix, Arizona.

One sewer was allowed for two or more units in: Burlington, Vermont, and Charlotte, North Carolina.


Подпись: PRECAST SUMP In Street

Portland, Oregon In North Meadow Village, developed

and built by Black Bull Enterprises in Portland, Oregon, the developer proposed changes deleting 630 feet of storm sewer pipe and adding an effective means of groundwater recharge.

A system of swales was designed to convey runoff into three on-site sumps where it could soak into the soil. Where storm sewer pipe was required, PVC was used in place of concrete pipe. The combination of savings from each change in the storm drainage system resulted in a savings of $6,350. ITus was equivalent to a per unit savings of $742.

Drainage for Cimarron, developed and built by Knoell Homes, Inc., was primarily above ground. Concrete valley gutters were used in some streets, and normal street curbs and gutters in other streets to direct stormwater to a channel and then to retention basins. The retention basins further created a visually attractive entrance to Cimarron. This drainage plan saved $70,578 over the original plan which required some underground drainage through an 18-inch concrete pipe, and a, pumping station to lift stormwater to an existing canal.

Подпись: жПодпись: Phoenix, ArizonaПодпись: Cimarron entranceSTORM WATER DRY SUMPПодпись:In Covington Place, builder/ developer Norcon Builders, Inc., eliminated typical Greensboro curbs and gutters. Ninety percent of the stormwater is absorbed by grassy swales along the sides of the streets and filters into natural areas on the site. This design saved approximately $200 per unit, and added to the attractive, woody, natural feeling of the subdivision.

Charlotte, North Carolina Stormwater in Lynton Place, John

Crosland Company builder and developer, is carried by grassy swales to a retention pond, with culverts used where necessary. This saved $16,390 compared to the curb, gutter, and piping system normally used in Charlotte.

The following demonstrations also used grassy swales instead of the typical locally accepted culverts for storm­water drainage: Oklahoma City, Oklahoma, and Knox County, Tennessee.


Подпись: Lacey, WashingtonEXAMPLES FROM THE DEMONSTRATION PROJECTSThe Park, developed and built by John Phillips, realized savings through changes in the storm drainage standards. The typical Lacey street is constructed with catch basins every 250 feet. Underground concrete pipes convey water from basins to a location off site. In addition, manholes are required at a spacing not to exceed 250 feet.

Phillips proposed a number of changes to Lacey standards. He received permission to replace curbs and gutters with a grassy swale along one side of the street and sloped the road surface toward the swale, a deviation from the typical crowned street. One catch basin drained into a retention pond, and another part of the site drained into an existing ditch.







$ 40,000



Type I catch basin




Pipe and tubing

– 18" Concrete culvert



– 15" Concrete culvert



– 12" Concrete culvert



– Drainage tubing











6" Vertical curb and





6′ Valley gutters




Hip rap




Sales tax (7.8%)








Cost Per Unit

$ 320*

$ 1,087**



*176 units **153 units

Cost savings attributed to changes in storm drainage standards at The Park are shown. Total savings of $767 were realized per unit.

Everett, Sunridge, a subdivision developed and Washington built by Rich Boyden, used existing

site conditions and alternate materials to improve cost effectiveness of the development. Normal procedure in Everett is to install CMP for the underground storm drainage system. It is also standard procedure to apply a per unit drainage fee of $432 to new residential construction.


In exchange for dedication of a 5.8 acre tract of land in the flood plain, the city agreed to waive the drainage fee at the site. Based on its success­ful use as sanitary sewer and water pipe, the city also permitted PVC to be installed in place of CMP storm pipe, resulting m a savings of $2,916. When added to the $432 per unit drainage fee, the total storm drainage system at Sunridge was installed at a savings of $27,108. This illustrates benefits of a reasonable compromise to both the community and the developer.



Gutters, which are discussed in the previous section, are just one component of the complete storm drainage system. However, important economies can be achieved in the construction of entire storm drainage systems.

Following are guidelines for storm drainage systems:

• Use performance requirements in place of prescriptive standards in all components of storm drainage design.

• Consider detention/retention basins, especially when regional management is preferred.

• Use less expensive alternatives to corrugated metal and concrete pipe.

• Consider precast structures if available from local suppliers.

• Reduce the use of manholes and inlets by increasing spacings between structures, or by replacing them with curved pipe sections, tees, and wyes where appropriate.

Traditional stormwater systems were usually "closed": that is, once water entered the system, it passed through nonporous pipes and channels, sometimes for substantial distances, until it was finally discharged into a moving stream or river. More recently, the undesirability of removing a significant portion of > runoff from local areas where precipi­tation falls has become increasingly clear. Consequences can include: inadequate recharge of groundwater supplies; increased potential for contamination of groundwater; soil subsidence, such as the formation of sinkholes that occurred in central Florida; and downstream flooding.

Modern systems increasingly emphasize retention of rainfall in the local area where it falls. Parts of the con­veyance system can be left "open," substituting grassy swales and natural drainage for closed piping. Detention and/or retention basins can also accommodate excess stormwater, enabling the gradual recharge of local groundwater supplies.

Open portions of drainage systems cost less than equivalent closed piping. Environmental considerations and cost savings therefore go hand in hand. Additional savings can be achieved through regional stormwater manage­ment serving the entire drainage basin or several specific sites within a basin. Regional control of stormwater generally requires less construction by developers, and the local jurisdiction achieves savings in operational and management costs. Improved effi­ciency is another benefit over individual site controls, since the need for "piecemeal" planning can be reduced.

Подпись: Design Storm RequirementA ten-year design storm is the typical standard for the "minor" stormwater system in a residential development. However, major channels or culverts with large contributing areas require special consideration. Design storm frequency is based on convenience and economics. A community decides how much to pay to insure against the possibility of flooding. The merits of each proposed site plan must be considered, since each site adapts differently to various designs. Performance requirements, which generally encourage innovative and less costly alternatives, should be used over prescription standards.

Two effective methods for carrying excessive stormwater use detention and/or retention basins and "overland relief." Retention/detention facilities can take a variety of forms. Manmade lakes and subsurface absorption are two of the more popular systems. Although each has its own pros and cons, both achieve the intended objective of effective stormwater management. Lakes contribute to aesthetic value but require more land area. Soil absorption systems can be installed on "tighter" sites but are limited to the capacity of the soil.

Подпись: Detention/Retention Подпись:Culverts and open concrete channels can be reduced in size by grading the surrounding land to direct stormwater on an overland path to the stormwater system downstream if the design storm is exceeded. Grassy swales provide overland relief in a residential neighborhood. Larger "flood banks" are used in major drainage areas.



In recent years, less expensive, more durable plastics have begun to replace traditional corrugated metal pipe (CMP) and reinforced concrete pipe (RCP). Polyvinyl chloride (PVC) and polybutylene (PB), both exhibit excellent resistance to corrosion and are currently used for stormwater pipe.

PVC, a relatively inexpensive plastic, can be installed throughout most of the "minor" storm drainage system.

PB is manufactured in sizes small enough for water supply systems, large enough for highway culverts, and in most sizes in between, usually in a corrugated configuration to provide the appropriate structural qualities. Due to their relatively light weight, PVC and PB pipe do not generally require special equipment for place­ment in the trench.



Components of a sewer system -­manholes, sewers, inlet and outlet structures – must be examined for possible cost savings in installation methods, choice of materials, and use of new designs. Where available, precast manholes and inlets generally provide a less costly alternative to abor intensive, site-built structures.


An average of $1,000 to $1,500 can be saved by eliminating a single manhole, depending on depth and local cost factors. Although many communities allow manholes or inlets to be spaced a maximum of 600 to 800 feet apart, some standards limit maximum spacings to as little as 200 feet.

These shorter spacings are carry-overs from an era when clean-out capabili­ties and construction techniques were inferior to those today. Officials must periodically review such standards to encourage state-of-the-art construction.

Manholes can also be eliminated by installing a curved section of pipe at nonabrupt changes in direction. Many communities also recommend installing a cleanout or other access within 50 feet of a bend to clear possible obstructions. The need for such access is questionable, since there is little risk of stoppage in the curved storm sewer alignment.

Подпись: Prefabricated tee section

Manholes can be eliminated where smaller pipes join larger storm "mains." For example, a prefabricated tee or wye section can ioin a building roof drain (downspout) with the public storm drain, thereby avoiding the added cost of a manhole.

STORM DRAINAGE SYSTEMSEndwalls, commonly installed at the end of a drainage pipe, can also be eliminated. With proper grading at the terminal end of the pipe, a flared end section will provide the needed transition at a much lower cost than an endwall.

Multiple use of drainage structures should be encouraged when possible. A yard inlet, combined with a curb type inlet, can achieve greater efficiency at less cost, receiving runoff from two or more directions.







In some cases, inlet structures can be completely eliminated and replaced with flared end sections. If the surrounding area is graded properly, an end section can be used as an inlet in place of a drop type structure.

Since the cost of an end section is similar to a standard section of pipe, overall savings would be equivalent to the cost of any eliminated inlet structure.

Inlet/Outlet Rip-rap, grouted stone, or other Controls erosion controls can often be replaced with one of the commercially available fabrics designed for soil stabilization. The fabric is placed at the end of the channel or pipe after the area has been graded and seeded. Fabrics can be installed at less cost than concrete or stone erosion controls, and provide a more appealing site.


Curbs and gutters convey rainfall into storm drainage systems, which are discussed in the next section. There are, however, less costly alternatives to the traditional vertical curb and gutter construction.

Following are guidelines for curbs and gutters:

• Substitute grassy swales for curbs and gutters.

• Where curbs are installed, build rolled curbs rather than traditional vertical curbs.

• Reduce the width of concrete gutters or eliminate them entirely.

• Eliminate reverse-flow curbs and gutters in parking lots, or replace them with asphalt curb, header curb, wheel stops, or integral curb/sidewalks.

• With concrete vertical curbs, use extruded construction rather than formwork.

Подпись: Grassy SwalesПодпись: Typical roadside swaie Grassy swales are depressed areas running parallel to the street that serve in lieu of curbs and gutters to convey stormwater. The grading required to construct a swale. can be completed during the grading of the surrounding lots or during final street grading. Therefore, cost savings are approximately equivalent to the cost of installi ng a curb and gutter.

In addition to providing savings in initial construction, swales offer continued savings in the form of lower long-term maintenance. Periodic flushing, replacement, or rehabilitation of pipes is eliminated. Swales within the public right-of-way are typically maintained by the home owner. Most swales can be graded to insure easy mowing.

Where runoff can be accommodated by a shallow swale, the depressions can be carried directly across driveways. Where a deeper depression is required for greater runoff capacity, concrete or metal conduits can be installed under driveways. At street intersec – tiohs, stormwater pipe can be installed under the street.

In addition to providing cost savings, swales allow for local retention of moisture from rainfall and melting snow. This is discussed in greater detail in the next section.

Подпись: Types of CurbsCURBS AND GUTTERSCURBS AND GUTTERSThe most common type curb in urban residential settings is the vertical combination curb and gutter.

A less costly alternative is the rolled curb, also called the rollover, roll, or mountable curb. Rolled curbs are typically 6 inches or less in height with a plane sloping face or well – rounded corners with a 2-inch to 3- inch radius which allow vehicles to cross them with varying degrees of ease. They can be sized to meet local hydraulic demands; the slope across the face of the gutter and the height of the curb can be designed to meet the projected capacity.

In many instances, curbs are installed before the type of house to be constructed or a lot is selected, and before driveway placement is decided. Therefore, it is usually necessary to remove the vertical curb, install a curb cut for the driveway, and haul away the old curb. With a rolled curb this is not necessary, saving approximately $300 to $450 per housing unit in the affordable housing demonstrations.

However, if vertical curb is chosen, good planning can reduce the added cost of removing any curb. A simple method gaining in popularity is to leave a space for the driveway and pour a separate entrance later. If possible, the driveway entrance should be installed during construc­tion of the adjacent sidewalk to avoid added labor costs.

Подпись:Concrete gutters, 18 inches to 24 inches wide, are a standard require­ment in many development specifica­tions. In most areas, a 12-inch gutter is sufficient, while in more arid regions, gutters can be elimi­nated entirely by simply extending the asphalt surface to the shoulder or curb. Local weather data should be reviewed, and gutters reduced in size or eliminated where rainfall rates warrant.

Curbs in Alternatives to vertical curbs in off – Off-Street Parking street parking include:

• elimination of curbs and gutters

• header curbs

• asphalt curb construction

• integral curb and sidewalk

• wheel stops

Combination curb and gutter can be eliminated in many parking lots by encouraging the use of sheet flows.



CURBS AND GUTTERSMuch of the curb line in parking areas generally consists of reverse flow gutters – that is, gutters that do not convey water as a conventional gutter does, but simply divert water away from the curb. This can usually be accomplished without a curb by proper grading of the parking lot surface.

Подпись: Wheel stops in parking bays
Подпись: STREET

Where curbs are required or chosen, they can often be replaced with header curbs, asphalt curbs, or integral curb and sidewalk, especially in cases where a gutter is not warranted.

Wheel stops are a less expensive alternative to curbs that keep intact the psychological barrier provided by curbs.

Подпись: Construction MethodsInstallation of curbs and gutters traditionally required labor­intensive formwork and preparation. Such construction methods have increasingly been replaced by extrusion or "slip form" techniques in which the operator, following a string line with a machine, "lays" the concrete out in its final form. This technique can be used to construct either a traditional curb or alternative types of rolled curbs. In areas where traditional formwork is still done, builders should check the availability of labor-saving alternatives.

Подпись: Boise, IdahoThe city permitted construction of rolled curbs as a substitute for 6- inch curbs along the residential streets of the Lakewood Meadows development. A total of 3,720 feet of rolled curb was installed at a cost of $16,740. Traditional vertical curbs were required along one collector street; 1,063 linear feet at a cost of $6,112. The rolled curb saved $1.25 per foot or $146 per housing unit.

In Fairway Village, the city permitted substitution of a rolled curb for a 6- inch vertical curb. The rolled curb cost $2,00 per foot less to install. Savings were $10,368 or $477 per unit.



Santa Fe curb and gutter vs Fairway Village curb and gutter





Elkhart County, Indiana

Elkhart County approved the elimina­tion of curbs and gutters, and substitution of a system of drainage swales. The cost of typical Elkhart streets, including curbs and gutters, averaged $32 per foot. The curbless demonstration project streets averaged $21 per foot. A total of $330 was saved on each 60-foot wide demonstra­tion lot.

Other affordable housing demonstra­tion projects using rolled curbs instead of the typical vertical curbs include: Tulsa, Oklahoma; Oklahoma City, Oklahoma; Birmingham, A labarna; White Marsh, Maryland; an d Sioux Falls, South Dakota.

Demonstrations in Christian County, Kentucky; Mesa County, Colorado; Greensboro, North Carolina; and Lacey, Washington eliminated curbs and gutters.


Подпись: Boise, IdahoEXAMPLES FROM THE DEMONSTRATION PROJECTSПодпись: Lincoln, NebraskaTypical Boise streets have sidewalks on both sides. At Lakewood Meadows, the city permitted elimination of sidewalks on one side of the sub­division’s streets and around T – turnarounds. One higher-order collector street was required to have sidewalks on both sides, but a sidewalk on one side only was allowed for a high-volume arterial street. Walkways were provided in common areas and between T – turnarounds.

The builder estimated that 2,696 additional linear feet of sidewalk would have been required to comply with existing Boise standards. Construction costs were decreased by $8,088, a per-unit reduction of $216.

Existing Lincoln standards call for 4- foot wide sidewalks on both sides of all residential streets. At Parkside Village, the city permitted Empire Homes to install З-foot wide sidewalks on one side of the street only. Cost savings were $4,289, or $191 per unit.

County standards call for sidewalks on both sides of residential streets. At the Hermitage Hill affordable housing project, this requirement was waived altogether, and no sidewalks were installed. Savings were $40,348, or $558 for each of the 73 units.

Подпись: Christian County, KentuckyПодпись: Crittenden County, ArkansasRex Rogers, in Harvard Yard, used an 8-foot concrete swale on one side of the street and graded the street so stormwater was channeled to that side. The swale is only slightly angled and doubles as a sidewalk.

Other demonstration sites which eliminated sidewalks altogether or used them on only one side, contrary to normal local practice, include:

Charlotte, North Carolina; Phoenix, Arizona; Tulsa, Oklahoma; Santa Fe, New Mexico; Lacey, Washington; and White Marsh, Maryland.

Pedestrian pathways or meandering walkway systems are used in Phoenix, Arizona and Portland, Oregon.


Many local zoning ordinances and construction standards specify that sidewalks be built on both sides of residential streets. These requirements were developed during an era of lower land values and lower construction costs, and should be reviewed in the context of today’s higher costs.

Following are guidelines for sidewalks and walkways:

• Construct sidewalks on one side rather than both sides of local streets, and consider elimination altogether on lightly traveled streets.

• Eliminate sidewalks around deadend streets and cul-de-sacs.

• Minimize placing homes facing collector and higher-order streets, thereby reducing or eliminating the need for sidewalks on these streets.

• Replace infrequently used sidewalks on streets with pathways between _ groups of residences, bus stops, stores, playgrounds, and other community facilities.

• If sidewalks are necessary, limit their width to three feet.

• Consider using sidewalks integral with curbs.

Sidewalks in Local governments, builders, and home Residential Areas buyers all benefit from cost savings

that can be achieved in sidewalk construction. Builders and home buyers save through lower construction costs. Local governments save through reductions in maintenance and replacement.

An increasing number of communities have dropped requirements for sidewalks in residential communities from their standards. Streets in these areas generate insignificant amounts of pedestrian traffic and a low volume of vehicular traffic moving at slow speeds. A properly graded shoulder, or the roadway itself, can provide a suitable pedestrian pathway.









Combination roadside shoulder/waikway

For the same reasons, sidewalks can also be eliminated around deadends and cul-de-sacs.

On higher-order local streets and collector streets, safety is often cited as the rationale for building sidewalks on both sides of the street. However, in the majority of these cases, a % single sidewalk will suffice. Situations

in which a single sidewalk will generate substantial street-crossing activity by pedestrians can be individually evaluated.

Подпись: Single sidewalk along higher-order street Подпись: Pathways and WalkwaysSidewalks along higher-order streets can, be eliminated completely by reducing the number of residences which face such streets. Pedestrians will then use the local streets on which homes are situated.

In planning for sidewalks, and also for pathways as discussed below, consider­ation should be given to likely _ pedestrian destinations. These include such places as bus stops, playgrounds, and convenience stores. Accommoda­tion of significant foot traffic along standard walking routes is more important than accommodation of occasional and casual traffic between and among homes.

Pathways and walkways offer an alternative to sidewalks that is cost effective and eliminates safety hazards to pedestrians that might arise from passing vehicles. This consideration can be prominent in planning the layout of subdivisions.

Such planning can provide for concrete walks, asphalt paths, or gravel paths between and among strategic locations. Walking access can be established between groups of residences and such facilities as parks,

Подпись: Pathways often eliminate need for sidewalks

Подпись: Dimensions and Construction SIDEWALKS AND WALKWAYS

community centers, and shopping centers. The paths and walkways can pass over easements that constitute part of the total subdivision plan. Townhouse and cluster developments lend themselves well to this type of integrated planning.


In the illustration, a З-foot and 6-foot sidewalk are compared. It should be noted that, in addition to a 50 percent reduction in the quantity of materials required, the З-foot sidewalk reduces the required right-of-way or easement by 6 feet. ,

Three-foot and 6-foot sidewalk

An integral curb and sidewalk combines two separate processes into a single step. One edge of the sidewalk is "thickened" and its side doubles as a curb.