 |
WATER SUBSYSTEM
IMPROVEMENT STUDY
FOR THE
NORTHWEST AREA AA
IN THE
TOWN OF MOUNT PLEASANT
WESTCHESTER COUNTY, NY
PREPARED FOR:
TOWN OF MOUNT PLEASANT
WESTCHESTER COUNTY, NEW YORK
PREPARED BY:
CHARLES A. MANGANARO
CONSULTING ENGINEERS, P.C.
65 East Route 4
River Edge, New Jersey 07661
FEBRUARY 2004
CAMCE No. 1774
SECTION 1 - INTRODUCTION
There are 241 homes and 36 potential lots in the Town of Mount Pleasant (ATown) in an area adjacent to the southwestern boundary of the Village of Pleasantville (AVillage). This includes homes in the following areas: Locust Road, Woodland Drive, Ridgewood Drive, Manville Road, the southern portion of Choate Lane, Leroy Street, Central Avenue, and related streets (designated as Area AA), but does not include portions of the Choate Lane area, the Mountain Road area, and the northern end of the Sarles Lane area. This Area AA is not part of a water district, improvement district, or other municipally recognized organization or corporation.
While these homes and lots reside physically in the northwest corner of the Town, many receive water from the Village Water Department which also maintains the water mains. Since the mains in this area are outside of the Village, the Villages attention to these areas has been on an as needed basis, and often is a result of a leak or complaint only. Those home owners that are not serviced by the Village have chosen to drill wells, which characteristically tend to be very deep and have relatively low yields.
In general, the homes in these areas which receive water from the Village suffer from low pressure, low volume, and relatively high water rates. The quantity and pressure of water available for fire fighting in many portions of this area is substandard. The lack of adequate water mains has resulted in a situation wherein future growth must be meticulously monitored. In extreme cases, permits for connection to the water system have been deferred until the water system can be upgraded, or required a sophisticated water storage system.
In addition, the resulting low pressures and volumes in the existing mains also affects the local fire departments ability to adequately fight fires. Existing hydrants may not provide adequate water to extinguish a major fire in the area, requiring fire fighters to manually lay hose from more substantial water sources, utilizing precious time and manpower.
Charles A. Manganaro Consulting Engineers, P.C. has been tasked with a review of only Area AA and asked to provide updated costs and recommendations to upgrade the existing water system infrastructure for Area AA.
SECTION 2 - REGULATORY REQUIREMENTS
The following will serve as a brief summary of the water supply and distribution regulations and their relation to the study area.
The size of distribution mains and pressure in the piping system are subject to regulation. The New York State Department of Health has adopted the Recommended Standards for Water Works (also referred to as, (The Ten States Standards) as the guidance document for acceptable raw and treated water quality, as well as distribution system design specifications. According to this Standard, minimum water main size when fire protection is provided shall be 6 inches. Static pressure sources, such as storage tanks, shall maintain operating water level variations of less than 30 feet. The normal working pressure in a distribution system should be 60 pounds per square inch (psi), and not less than 35 psi. A water distribution system shall also be designed to maintain a minimum pressure of 20 psi at ground level at all
points in the system under all conditions of flow, including during fire fighting events. The Ten State Standards also indicate that a system pressure in excess of 100 psi should be reduced using devices, such as a pressure reducing valve.
Fire flow requirements are established by the Insurance Service Office (ISO). As over 95% of the service area consists of single-family, less than three-story residential dwellings, the needed fire flow is essentially dependent upon the type of construction and distance between dwellings. The fire flow requirements for the concerned area varies from 500 gpm to 1,000 gpm. Based on the distance between buildings, in some cases being less than 30 feet, a fire flow of 1,000 gpm is needed. Additionally, needed fire flows must be maintained for two hours. Based upon fire flow calculations, either 120,000 gallons of water storage capacity should be provided (just for fire protection), or a separate fire flow pumping (1,000 gpm) arrangement should be installed in a booster pumping station.
While the majority of the existing water distribution system in the area of concern was installed before these regulations were formalized, any improvement to the water system will be required to meet these guidelines. Any and all improvements to public water supplies must be submitted and approved by the Westchester County Department of Health (WCDOH).
SECTION 3 - EXISTING CONDITIONS
The following is a brief description of the area of concern. The May 1997 Study had three study areas that were grouped into three geographic areas, namely: Locust Road and Woodland Drive (Area AA as shown in Figure 1 at the end of the report); Mountain Road South; and Mountain Road North. However, as previously stated this study is a review and update of the costs and recommendations presented in the May 1997 Study for only Area AA as follows:
Area AA - Locust Road and Woodland Drive Area
A total of approximately 241 homes and 36 potential open lots exist in the area. Area AA consists of the following: Locust Road, Woodland Drive, the southern portion of Choate Avenue, Manville Road, Lake Drive, and related streets including Polly Wiggle Lane, Highland Terrace, an unnamed right-of-way, Ridgewood Drive, Oak Drive, Birch Drive, Parkview Drive, Park Street, Fairview Drive, Elliot Place, Sanford Street, Elmwood Street, Walnut Street, Central Avenue, Chestnut Street, Short Street, Underhill Road, Leroy Street, and Foshay Avenue. Portions of this area are characterized by old tuberculated 6-inch water mains, which provide water to 1 to 2-inch water mains. The 6-inch water mains were last flow tested in 1995. However, a relatively new 6-inch water main has been constructed on Highland Terrace and an
8-inch water main on Bedford Road.
In summary, the flows were substandard, with marginally acceptable volumes to significant portions of the subsystem, and unacceptable pressures for fire fighting (less than 500 gpm at 20 psi at the corners of Locust and Ridgewood). This was confirmed in previous studies, and by independent flow tests. Existing 1 to 2-inch water mains were installed in excess of 50 years ago on Ridgewood Drive, Oak Drive, Birch Drive, Parkview Drive, Polly Wiggle Lane, and an unnamed right-of-way, as well as on parts of Woodland Drive, Locust Road, and Elliot Street. On Lake Drive, each home has a separate tap from a short (approximately 20 feet long) main from the 8-inch main in Bedford Road that was installed in the mid 1990's.
This area is provided water via a single source, the existing cement mortar lined 8-inch water main on Bedford Road, and has no water distribution main looping. Water is purveyed by the Pleasantville Village Water Department.
SECTION 4 - SUBSYSTEM MODIFICATION ALTERNATIVES
Area AA can be characterized as an area with shallow rock outcrops and steep slopes which renders installation of new water mains as a costly endeavor. This area requires substantial distribution main development. The majority of existing water mains are undersized and require replacement and/or extension simply to provide adequate water pressure and volume to existing customers. Consequently, the extension of the existing mains will allow connection to the system by present well-water users, thus increasing the number of customer accounts.
It is recommended that fire fighting capacity in the area be upgraded. This may be accomplished by increasing the distribution system to streets presently not served by municipal water, or served by insufficient mains.
Two significant results then occur: new fire hydrants could be installed, and municipal water would be available to present well-water users. Streets such as Park Street, Central Avenue, Chestnut Street and related streets, and Foshay Avenue to Leroy Street may benefit from these improvements.
Looping water mains is possible in the following configurations: Bedford Road - Locust Road - Woodland Drive; Locust Road - Park Street - Fairview Avenue - Walnut Street; and, via possible easement - Ridgewood Drive - Parkview Drive - Park Street - Locust Road.
Due to age and severe tuberculation the 6-inch water mains on Locust Road and Foshay Avenue are recommended to be replaced in order to eliminate flow restrictions and handle the increased water pressures to meet regulatory requirements. However, the existing 8-inch and 6-inch water mains in Bedford Road and Highland Terrace, respectively, are relatively new and will not require improvements other than a new fire hydrant at the end of Highland Terrace. All new water mains will be 6-inches or greater in diameter with most being 8-inches.
With a potential water consumption requirement of 241 homes and 36 potential open building lots in this area, either a pump station and a water storage tank (standpipe type) with a capacity of approximately 400,000 gallons or a booster pumping station with a fire flow pump and possible 120,000 gallon tank (standpipe type) will be required. This is due to the variations in elevation and friction losses associated with the volumetric demand of the proposed additional homes to be serviced in this area. It should be noted that both pump station configurations would include a chemical feed system to maintain chlorine residuals.
Two potential sites exist in this Area AA where either a pump station or booster pump station could be construction. The initial site which has been referenced in past studies is an open parcel of property that would need to be acquired at the southeast corner of the intersection of Bedford Road and Locust Road. However, a review of the Town's tax maps has revealed an open parcel of property that the Town owns along the west side of Locust Road approximately 600 feet south of Bedford Road. Being that this property is owned by the Town it has been selected as the new pump station site for both alternatives. A preliminary layout of the pump station (either alternative), water storage tank (at the end of Central Avenue or at the pump station site) and water main distribution system (including valves, fire hydrants
and pressure regulating valves) has been shown in Figure 2 at the end of the report.
As mentioned above, in order to meet the water consumption requirements of Area AA and be in compliance with Ten State Standards either: a pump station and water storage tank at the end of Central Avenue (which will be called Alternative No. 1) or a booster pump station system with a water storage tank at the pump station site (which will be called Alternative No. 2), along with the distribution system for both alternatives shown in Figure 2, must be constructed. A brief description of each Alternative and major tasks to complete is as follows:
ALTERNATIVE NO.1
 Pump station with two constant speed pumps, flow meter, chlorination system and an emergency generator on a lot owned by the Town along the south side of Locust Road.
 Dedicated supply main from the Village line to the pump station.
 Discharge main from the pump station to near the intersection of Ridgewood Drive and Locust Road.
 A 30 foot diameter by 80 foot high (400,000 gallon) water storage tank (consisting) of operating, fire and emergency storage volumes) on park land at the end of Central Avenue. A picture of a similar size tank (34 foot diameter by 75 foot high - 500,000 gallon) is included at the end of this report.
 Water main distribution system (including valves, fire hydrants, pressure regulating valves (PRV=s), and new service connections to existing homes).
 Radio control system (UHF) between pump station, water storage tank, PRV=s, and Mount Pleasant Water Department.
 Complete Environmental Impact Assessment.
 Acquire park land property through an Act of the New York State Legislature.
 Complete design, obtain permits and bid for construction.
 Complete construction and place into operation.
ALTERNATIVE NO. 2
 Booster pump station with three distribution system pumps, one fire flow pump, four variable frequency drives, flow meter, chlorination system, and an emergency generator on a lot owned by the Town along the south side of Locust Road. A 30 foot diameter by 24 foot high (120,000 gallon) water storage tank for fire protection only (no emergency water storage volume) has been included for the fire flow pump
which will depend on the results of a hydraulic analysis of the Village distribution system.
 Dedicated supply main from the Village line to the pump station.
 Discharge main from the pump station to near the intersection of Ridgewood Drive and Locust Road.
 Water main distribution system (including valves, fire hydrants, pressure regulating valves (PRV=s), and new service connections to existing homes).
 Radio control system (UHF) between booster pump station, on-site water storage tank, PRV=s, and Mount Pleasant Water Department.
 Complete Environmental Impact Assessment.
 Complete design, obtain permits and bid for construction.
 Complete construction and place into operation.
Based on our distribution system layout in Figure 2, a technical evaluation of the proposed project, and our review of capital costs to design, permit, acquire property, and construct this project, we recommend a pump station on the Town property site with a water storage tank at the end of Central Avenue on park land property (Alternative No. 1) to serve Area AA. The Booster Pump Station, of Alternative No. 2, has a slightly lower cost but is not as reliable and technically sound. Thus, for the slight increase in capital cost a much better, simpler and more reliable water distribution system is achieved. The maintenance costs for Alternative No. 1 should also be lower than for Alternative No. 2.
A new water district would be formed for Area AA that would be operated and maintained by the Town's Water Department. The pump station would be designed such that during periods of low demand (such as overnight), the water storage tank would be filled in order to meet peak demands during the day. This water storage tank would also provide fire flow protection and a supply of water for emergencies (not available with the Booster Pump Station Alternative.
SECTION 5 - SUPPLY OPTIONS
In general, there are two options to supply water to Area AA. The first option being the Village Water Department with the second option being the consolidation and installation of new water transmission mains from Town water sources.
Unfortunately, this portion of the Town is characterized by shallow rock outcrops and deep groundwater. This has lead to the present situation, in which consumers on the existing Village water system often share undersized water service lines, and those whom have chosen to drill wells have drilled deep, marginally productive (in some cases less than the acceptable minimum of 5 gallons per minute) wells. In either scenario, water users have inadequate water pressure and volume.
The options to supply water to Area A from the Town were evaluated and presented in a report entitled A Water Main Route Study to Supply Water to the Northwest Area of the Town of Mount Pleasant, Westchester County, New York, dated October 2002 and prepared by Charles A. Manganaro Consulting Engineers, P.C. Besides presenting water main routes, probable costs were also developed and presented for each option. In summary the two supply options were: from the southwestern end of Irvington Street and Stanley Street in Thornwood, across the Saw Mill Parkway and River to Polly Wiggle Lane or from the Hawthorne Water Storage Tank north to N.Y. Route 117 and then east to the intersection of Bedford Road and Woodland Drive.
Both Town supply options were found to be very expensive due to: distance, shallow rock, natural obstructions and major highway crossings.
SECTION 6 - ECONOMIC ANALYSIS
Based on the Subsystem Modification Alternatives presented in Section 4, the following is a discussion of the Probable Project Costs for Alternative No. 1 and 2. Project costs consist of probable surveying, boring, geotechnical, planning, engineering, permitting, and construction costs. Alternative No. 1 has a probable cost of one dollar for park land acquisition from the County for the water storage tank at the end of Central Avenue. Engineering probable costs include planning, design, and permitting in 2004/2005 dollars while construction management and resident observation are in 2005/2006 dollars. Probable construction costs are in 2005/2006 dollars. The basis of these probable costs and associated dollar values is that if this project is to proceed it will start by the Spring of 2004. Starting this
project after the Spring of 2004 would require that the probable costs presented be adjusted to reflect the appropriate future start date. The Probable Project Costs for each Alternative are as follows with summary Tables 1 and 2 at the end of this report plus detailed spread sheets of probable costs in Appendix A:
ALTERNATIVE NO. 1 - See Table 1 for a breakdown of the Project Probable Cost.
Project Probable Cost...................................$6,321,053
ALTERNATIVE NO. 2 - See Table 2 for a breakdown of the Project Probable Cost.
Project Probable Cost...................................$6,077,815
NOTE: These costs are predicated upon typical construction methods and assumptions as to the quantity of rock anticipated to be removed. A detailed geotechnical investigation will be required to finalize the probable construction costs.
The costs presented below represent the annual cost per home (241 homes). These costs are based upon the above Probable Project Costs being financed for a 20 year period at a 6% interest rate as follows:
ALTERNATIVE NO. 1
Probable Annual Cost Per Home......................$2,287/year
ALTERNATIVE NO. 2
Probable Annual Cost Per Home......................$2,199/year
NOTE: The distribution of Probable Project Costs has been presented on a annual cost per homeowner. However, the Probable Project Costs should be considered for distribution, for AreaAA, on the basis of a set dollar value per $1,000 of assessed property value; a set dollar value per 1,000 square feet of assessed value; or a combination of an annual cost per home for a set percentage of the capital cost with the remaining percentage of the capital cost being set on an assessed property value basis. These financing methods in general distribute the cost of the project so that larger homes/properties with higher assessed values and likely greater water usage, would pay a greater percentage of the probable project cost.
A review of the Project Probable Cost for each Alternative and indicates that there is a relatively small difference of $243,239 (less than 4%) between the two alternatives. This translates into a small annual difference of $88/year per home. For this reason and the technical reasons previously presented, we thus recommend Alternative No. 1 for design, permitting and construction.
SECTION 7 - CONCLUSIONS AND RECOMMENDATIONS
Of the approximately 241 homes in the Northwest Area AA of the Town adjacent to the southern and wester borders of the Village, nearly all of the households would benefit from upgrades in the water distribution system in this area. While increased pressure and volume may be a primary value, the secondary value includes increased ability of the fire department to fight fires in this area; this may result in decreased insurance rates for homeowners in this area.
The distribution system modifications outlined herein represent substantial construction, and substantial financial obligations. As this area represents a significant base of water consumers, it is recommended that a water district or similar entity be formed to facilitate financing of this project, as well as negotiate water purchase prices from the supplier.
Should the Town wish to pursue the recommendations presented herein, the next step would be development of a design memorandum. The design memorandum is required by the NYSDOH, and will provide the technical basis for the design of the necessary modifications. Also based on the selected Alternative it may be important to initiate discussions with a New York State Legislator representing this area to support and present for approval any construction on park lands.
J:\SECRETARY\A\TMP\1774\ReportforWater Subsystem Improvement Study for the Northwest Area A
APPENDIX A
| |
