Village of Hastings-On-Hudson, NY








            The Village of Hastings-on-Hudson has been plagued by flooding problems in an area east of Farragut Parkway, from Ravensdale Road to the Saw Mill River. A small waterway, subject to excessive runoff, meanders from Fenwick Road, under Branford Road, Ashley Road, and Farragut Avenue, terminating at the Saw Mill River.  Along this waterway, there are localized pockets of deep storm ponding, wide over-bank flooding, and backwater problems behind a masonry dam.


            In view of a continuing controversy over the need for and extent of improvements, the Village governing body sought technical help through the issuance of a Request for Proposals in May 2002 (see Appendix A).  This was followed with further requirements in a document issued in September 2002 (also Appendix A).


            The accepted proposal was presented to the Trustees in July 2002 (see Appendix B), and was followed by a supplementary document in September 2002 (also Appendix B).  A presentation was made before the Trustees in September 2002, which established the intended procedures and technical investigations which would ensue as the “modus” for the study.


            The challenges of this study have resulted from the following controversies and concerns:

a)       Complaints from property owners heavily damaged by localized ponding, versus the lesser concern of property owners that are minimally disturbed during similar storms.

b)       Major concerns by many property owners about potential environmental damage that might be caused by significant stream or culvert improvements.

c)       Apprehension by taxpayers over the incurring of large capital expenditures for localized problems.


Description of Area and Its Problems


            The affected area lies in the southeasterly portion of the Village (see Plate 1).  In general, this is a fully developed residential neighborhood, adjacent to major thoroughfares, such as Saw Mill River Parkway and Farragut Parkway.



            Ground relief is considerable, with changes from Elevation 107.0 near the Saw Mill River, to Elevation 176.0 on Ravensdale Road above Dan Rile Park.  Locally, slopes are steep in places, maximizing on Branford road (11% grade).  Lots are substantial in size, ranging in area from  ¼-acre to 1 acre.  The neighborhood is well established, with developed lawns, shrubbery and foundation plantings.  Large trees are scattered throughout the area (see plates).


            The waterway, and the affected areas, are localized (see Plate 2), yet there are portions of the drainage area extending into the upland slopes for almost ½-mile above the most severely flooded locations.  The waterway itself is an open channel for the most part, with culverts only under roadways.  At the source, near Fenwick Road, the channel width is only 2 to 4 feet, with depths ranging from 1 foot to 3 feet.  Toward the lower end, channel widths reach 8 to 10 feet, with depths of 5 feet or more.



            Reports indicate the following flood conditions (see greater detail in later sections):


            Fenwick Road Area –

Depths of ponding to 30 inches in roadway, basement problems, overland flow through yards.

Fenwick Road to Branford Road

Yard flow, and a reported 12-inch depth at the low point of Branford Road.

Branford Road to Ashley Road

Wide overland flow through yards, with depths to 6 inches, minimal flooding at Ashley Road.

Ashley Road to Farragut Avenue

            Flow confined to culverts, minimal damage.

Farragut Avenue to Stepping Stones –

            Over-bank flooding in undeveloped area owned by Village.

Stepping Stones Area –

Overland flow through yards, surcharge from dam’s backwater curve, (and from channel inadequacy), and some basement flooding.

Stepping Stones Dam to Saw Mill River

            Minor nuisance, some driveway flooding.


* * * *


As will be developed in later sections of this report, the area in greatest need of relief lies at the low point of Fenwick Road.  Property owners further downstream consider the flooding to be a tolerable nuisance, but stress the importance of not worsening conditions through upstream improvements.


Prior Studies


            Reports on the area’s problems have been published for almost 20 years.


            In October 1978, a Flood Insurance Study was prepared for the U.S. Department of Housing & Urban Development, Federal Insurance Administration.  The only waterways given detailed study in the Village were the Hudson River and the Saw Mill River.  The stream under study herein is illustrated (with no profile), showing flooding during 100-year frequency storms in the area south of High Street, and in the Fenwick Road area.  No other usable information was presented, except for the flood stage at the Saw Mill River.


            In June 1985, the District Conservationist, James B. Cropper, provided a brief report (see Appendix D) to the property owner of Stepping Stones.  He noted the overland flooding, the submergence of the driveway, siltation in the pond behind the dam, and erosion of the banks. He pointed out the deleterious effects of upstream development and waterway enclosures.  Solutions were presented in the form of: a) deepened channelization, to a 12-foot width and 3-foot depth, with gabion bank walls;  b) a culvert of similar dimensions under the driveway; and c) lowering of the dam to accommodate the 100-year flood condition.  Pragmatically, the author stated that “the cost of all this…to save the pond may be more than you wish to bear”.  Also, that the property owner must weigh “how important the pond’s visual appeal is to you.”  No action was taken subsequent to this report.


            In November 1986, a letter report was prepared by Hazen and Sawyer, New York City consultants (see Appendix C), authored by a local engineer (and later Trustee), Mr. David Walrath.  Drainage areas were roughly outlined, and storm flow estimates were presented for various storm frequencies.  In this professional report, it was concluded that “The stream channels and culverts downstream of Fenwick Road must be enlarged.”  Also, the report recommended intersection changes, and corrective work in the Stepping Stones area.  Possible solutions included the following:


  1. Regrading of the Ravensdale / Kent Road intersection.
  2. Retention basin in Ravensdale Park (now Dan Rile Park)

3.       Culvert and channel improvements downstream of Fenwick Road (pending study of environmental concerns).


The report also indicated that an assessment program could be undertaken  to offset a portion of the program’s capital costs.  The suggested measures were not undertaken. 


            In 1997, a series of letter reports were issued by a White Plains engineer, Mr. William H. Bruder, P.E. (see Appendix D), which concentrated on problems at Ashley Road.  Under his direction, the blockage and partial collapse of the existing stone culvert was repaired.  Also, a sloped grating was placed on the upstream side of the roadway, to reduce the entry of debris into the culverts.


Surveys Performed


            Frequent field forays were conducted for this study, to examine existing facilities, environmental conditions, evidence of flooding, utilities, tree identities, and for visual evaluations of reports by others.


            Instrument surveys were used to establish roadway elevations, topography in Dan Rile Park, utility inverts, and profiles along the possible routes for relief sewers.  Although the Village originally offered to provide detailed surveys, the work was diminished since the expense clearly outweighed the benefits.  All survey work considered necessary to a proper evaluation of conditions was conducted by internal forces, rather than by a larger subcontract.


            Existing mapping proved to be of variable value.  Tax maps and the zoning map were helpful in establishing property lines and saturation development.  However, the existing drainage map, and the sanitary sewer map, both lacked detail and were incomplete in several locations.  The eventual release of County-prepared topographic maps proved to be of most value.  This mapping provided excellent base maps (see plates), and permitted a reduction in the detailed surveys originally contemplated.


            Input from the Department of Public Works provided identification of many utility locations.  Superintendent Michael Gunther was most cooperative in this endeavor.  With his aid, and with pavement markouts by the utility companies, the pertinent pipelines were located and identified.  In several locations, culvert conditions were visually examined for obstructions or collapse.


            Soil borings were obtained at critical locations along relief sewer routes, or at important intersections (see Plate 12).



            Of most value, however, was the input from local residents. On three occasions (see Appendix E), groups of property owners appeared on site (frequently in the rain) to advise as to observed flooding conditions, property damage, culvert maintenance, and environmental concerns.  Through these voluntary contributions, much information was obtained, lessening the need to make observations during storm conditions.  Further, the expressed opinions were helpful in balancing the varying needs and concerns of each neighborhood.


Study Limitations


            It should be recognized that the purposes of this study are to identify the optimal solutions for the flooding problems of the area.  Field data is of an accuracy to permit comparison of alternatives, and to evaluate construction variables for estimating purposes.  The results are not intended to be sufficient for design purposes, but only to provide criteria, costs, and preliminary sizing.


            Mapping also presents limitations.  The 5-foot contours on the County topographic maps permit alternative comparisons, but would not be sufficient for design or construction purposes.


            Cost estimates must also be viewed as study level values.  To provide a level of comfort, contingency allowances are made (see tables), and prices are projected forward with an allowance for modest inflation.


Agencies Contacted


            In addition to local and County contacts, the following offices were contacted:


                        Soil Conservation District (U.S. Dept. of Agriculture)

                                    For information on soils, permit requirements, and file data.

                        N.Y. State Dept. of Environmental Conservation

For wetlands data, environmental requirements (SEQRA), and guidance.

                        U.S. Corps of Engineers

            For wetlands data.

N.Y. State Dept. of Transportation

            For highway data, drainage information, etc.







Existing Conditions


            Observations and reports (Appendix E) indicate the following storm related conditions:


Dan Rile Park (See Plate 3) -  Water discharging from Ravensdale Road crosses through the park, partially underground in a 27” reinforced concrete pipe.  There is some ponding in the park, but this was reduced by recent grading near the street frontage.



Along Fenwick Road (See Plate 3) -  Water coursing along The Fenway, along Branford Road, through Dan Rile Park, and from roadway areas to the east, all collect at the low point on Fenwick Road.  A swale located across Branford Road at The Fenway encourages flow into the same low area.  The only existing drain is an 18-inch vitrified clay pipe along the westerly curb of Fenwick Road, which is not capable of carrying the 1-year storm.  Water is further obstructed from passing downstream by the wall in front of #32 Fenwick Road (Chettih).  Water ponds at the low point to depths exceeding 24 inches, subsiding fairly quickly after a drop in precipitation.  Heavy surcharge occurs in the 18-inch drain during storms, lifting the grating off the frame at an inlet just north of #32 Fenwick Road.  A flood gate has been built by the property owner at #31 Fenwick Road (Haubold).  During storms, water reportedly enters the basements at #24 Fenwick Road (Van Wie), 32 Fenwick Road (Chettih), #29 Fenwick Road (Broude), and #28 Fenwick Road (Boccumini).  Other homes in the area are believed to be similarly affected.  In addition, flows from Ravensdale Road pass through yards on the east side of Fenwick Road, causing local damage.


Fenwick Road to Branford Road (See Plate 3) -  Some flood water is carried in the 15-inch and 18-inch vitrified clay pipes across the open yard at #32 Fenwick Road (Chettih).  Overland flow also passes through the same grassed yard, obstructed by the wall fronting on Fenwick Road.  There is open channel flow at the rear of this property, but the channels are partially obstructed by shrubbery.  A right angle bend at the rear of #30 Branford Road (Ratzenberger) further reduces the stream capacity.  In the side yard of #30, water floods through an open grassed area, in part because of an inadequate stream channel, and in part because of the undersized culvert at Branford Road.


Branford Road (See Plate 3) – Considerable flood water enters Branford Road from the Fenway area, collects at a low spot opposite #40 Branford Road (Leviss) then courses across this same property and through the rear of other properties until it reaches the stream.  There are no curbs to control this flow, and a high point opposite #37 Branford Road prevents drainage to the existing culvert.  There are no drains along this roadway, and the existing 24-inch vitrified clay pipe culvert across Branford Road is woefully inadequate.


Branford Road to Ashley Road (See Plates 3 & 4) – Storm flows pass along the westerly side of #25 Branford Road (McMichael/Kadala) through a grassed area.  The stream channel is small and heavily landscaped with attractive plantings which partially obstruct storm flow.  Storm runoff then floods along the property line between # 1 Ashley Road (Gross ) and #9 Ashley Road (Localio) through a heavily wooded area where the channel is inadequate to handle even moderate storm flows.



Ashley Road (See Plate 4) -  The culvert under Ashley Road is a 3 -foot x 4-foot box culvert which was recently repaired, and which is guarded by a trash rack on the upstream side which requires frequent cleaning.  No significant flooding is reported at this road, as long as the rack is kept clear.  (It was noted during inspection that a 6-inch   overflow pipe connects the box culvert to a sanitary sewer; this illegal connection should be dye tested, and plugged if necessary).


Ashley Road to Farragut Avenue (See Plate 4) – Some flooding is reported along the westerly parts of #2 Ashley Road (Jackson), but there appears to be little significant damage, except for occasional basement flooding.


Farragut Avenue (See Plate 4) – The existing 36-inch concrete pipe connects to a 30-inch corrugated metal pipe at a manhole in the street, with little reported backup.  The lines are apparently clear at this time.


South of Farragut Avenue (See Plate 4) -  Slight flooding is reported at #350 Farragut Avenue where the 30” pipe discharges into an open channel.


Farragut Avenue to Stepping Stones Driveway (See Plates 4 & 5) -  Open channel flow passes through undeveloped areas owned by the Village.  There are no reported problems, but the channel is partially blocked by debris, refuse, dead trees and underbrush.




Stepping Stones Area (See Plate 5) -  Flooding occurs across the Stepping Stones driveway and to an area immediately north, in part because of an undersized 36-inch culvert under the driveway.  In addition, there is flooding from the driveway south to the existing masonry dam (reference report in Appendix D).  There is also considerable siltation of the pond area north of the dam.  Flooding is reported in several basements along the west side of Nepperhan Avenue, particularly at #22 Nepperhan Avenue (Nugent) and at #24 Nepperhan Avenue (Ellis).  The area is heavily landscaped with attractive plantings and pathways, but the channel is too small to carry flood flows.


South of Stepping Stones (See Plate 5) -  The stream below the existing dam is narrow and deep, with limited capacity.  However, flooding is localized in areas immediately adjacent to the stream banks.  A small shed forms an encroachment over the channel in the rear yard at 16 Nepperhan Avenue (Thornton).  During extreme storms, light flooding has been reported in the driveway area at #12 Nepperhan Avenue (Casamento).


Below Nepperhan Avenue (See Plate 9) – No reported flood damage exists at the stream crossings of Farragut Parkway, extending to the Saw Mill River.  However, the more easterly crossing, consisting of two 30-inch pipes, has a serious blockage at the entrance to one of the pipes.



Drainage Areas and Flows


            The small stream that is the subject of this study is fed by a significant drainage area (see Plate 1).  To the north, the area extends more than ½ mile to Mount Hope Boulevard, and to the west, the area extends to Pearl Street.  Outlining of the drainage areas was accomplished through the use of County contour maps, with some field checking.


            At the Saw Mill River, near Farragut Parkway, the tributary area is 190 acres, and at Ravensdale Road the tributary area is 77 acres.  Following is a breakdown of the calculated areas, with a comparison (where available) of similar information from prior studies:


                                                                                    Drainage Area (acres)                

                                                            This Study *      Hazen & Sawyer       Conservationist **

Ravensdale Road                               77                       --                              --

Fenwick Road                                    89                       --                              --

Branford Road                                    94                       88                             --

Ashley Road                                    112                     107                             --

Stepping Stones                              181                     158                             174

Farragut Parkway                             190                     --                                --


Discrepancies in the reported drainage areas may be the result of differing contour information, storm drain routing, or better data available to this report.  However, the discrepancies are not beyond the normal degree of study error, and the data used in this report is clearly more conservative.


            For this study, estimates of storm flow were calculated using the broadly accepted criteria established by the U. S. Dept. of Agriculture, Soil Conservation Districts, in their Technical Release #55 (TR-55), published in 1975.  This booklet was used in conjunction with published Soil Maps (used to determine soil porosity and the degree of surface runoff), and the Village’s Zoning Map (used to indicate types of area development).  There was also the need to observe density of development, impervious areas, and the extent of grassed or pervious areas.


            A tabulation of flow data is provided (Table 1) for the critical points along the waterway, and for storm frequencies of 2 year, 5 year, 10 year, 25 year, 50 year, and 100 year.  As an illustration of the data, the reported flow at Fenwick Road for the 10 year storm is 197 cubic feet per second (cfs), which may be otherwise stated as 80,400 gallons per minute.


            For comparison with prior studies, the following tabulation is presented for a 10-year frequency storm:

                                                                        ________Peak Flows (cfs)          _____

                                                            This Study         Hazen & Sawyer       Conservationist *


Fenwick Road                                    197                     322                        --

Branford Road                                    206                     339                        --

Ashley Road                                      242                     386                        --

Stepping Stones                                354                     510                        375


            These discrepancies were discussed with the author of the Hazen & Sawyer report (D. Walrath).  In his opinion, our assumptions are reasonable and the results may be accepted for purposes of this study.

* * * * * *



*   Note that better mapping was made available for this study, than could be obtained for the other studies.


**  A further comparison of interest lies in the estimated storm flows for a 100-year frequency event.  The Conservationist provided a flow estimate of 660 cfs at the Stepping Stones property, which may be compared with the estimate for this study of 674 cfs.


            Basic to these studies is the perceived need to divert extraneous flows away from the seriously impacted areas.  Therefore, the following remedies are included in all of the following evaluations:


a.       Flow along Ravensdale Road must be kept flowing east, where possible.  To effect this result, curbs or berms will be planned along the south side of Ravensdale Road.  Also, an inlet will be placed immediately west of Kent Avenue along the south side of Ravensdale Road, to intercept gutter flow, and carry it to the drains flowing east. With a slight regrading of Kent Avenue, all of Area 1A (as reported in the Hazen & Sawyer Report) will be diverted out of the critical area.

b.       Flow along Farragut Parkway must be retained in the Parkway gutter, where possible, to minimize runoff toward the Stepping Stones area.  To effect this result, berms are needed along the easterly side of the Parkway.

c.       The existing pavement swale at Branford Road and the Fenway should be eliminated, in favor of a swale directed to the south (see Plate 10).



Hydraulic Gradients


            Hydraulic modeling of the area was accomplished with the aid of stream cross sections, culvert data, roadway elevations, and field observations.  This information was the raw data for computer modeling using the widely accepted U. S. Army Corps of Engineers (1979) software, developed by their Hydraulic Engineering Center, known as “HEC-2” stream modeling software.  This approach permits the development of hydraulic gradients and water surface profiles for steady and gradually varied flows in both prismatic and non-prismatic channels.


            The basic assumption in this study, for existing channel roughness, was an “n-value” of 0.05.  Other factors were used to offset the lack of precise contour information and detailed cross-sections.  The final model was successfully tested against empirical data reported for peak storm flooding, starting at a reported water level in the Saw Mill River at Elevation 117.0 during a 100- year frequency storm.





Basic Criteria


            The basic concern, of course, is the reduction (or elimination) of flooding and the resultant damage to property, inconvenience to the traveling public, and hindrance to emergency vehicles.  Depending on the storm frequency, damage in the pertinent areas varies from very light minor ponding… to impassable local water depths, side yard flooding, and basement seepage.  Therefore, solutions must vary with the area under study.


            The existing channel capacity is inadequate for all but the lightest rainfall.  The open channel cross-section is minimal, and the stream banks are overgrown in many areas.  Typical (average) cross-sections are as follows:


            Above Branford Rd………….….. 3.0 ft. wide, 2.0 ft. deep

            Above Ashley Rd…………….…. 3.0 ft. wide, 1.5 ft. deep

            Below Ashley Road ……………. 2.5 ft. wide, 1.5 ft. deep

Below Farragut Ave..…………... 6.0 ft. wide, 3.0 ft. deep

            Above Stepping Stones dam….. 3.0 ft. wide, 3.0 ft. deep

            Below Stepping Stones dam….. 5.0 ft. wide, 5 to 6 ft. deep


            Basic to all approaches is the need to minimize flow entering the basin.  To this effect, flow along Ravensdale Road is to be controlled under all alternatives, so as to reduce flow toward Fenwick Road.  Similarly, flow would be controlled along Farragut Parkway, to reduce flow toward the Stepping Stones area.


            To the extent feasible, consideration has been given to solutions which would provide flood reduction through the use of relief storm sewers.  Routing of storm flow around the most severely affected areas was planned, and then evaluated as to economic feasibility.


            Maximum and minimum projects are given consideration herein, phased wherever possible.  The final evaluation gives consideration to the physical, financial, and local acceptability of each plan.


            During development of this study, the following essential criteria were found basic to the project’s feasibility:


a)       Project costs must be kept to a minimum, considering the Village’s fiscal restraints and taxpayer concerns.

b)       Deep local flooding in Fenwick Road must be eliminated or reduced to manageable levels.

c)       Damage to in-situ landscaping, trees, and even natural underbrush, must be minimized or avoided.

d)       Downstream flooding must not be worsened.

e)       Objectionable yard flooding should be reduced, and basement flooding diminished.



The Request for Proposals (Appendix A) included an evaluation of channel improvements.* Accordingly, the following design criteria were established, assuming:


            Channel dimensions –

Trapezoidal (T), grassed, with side slopes of 1:2 (B = Base Width, D = Depth) Rectangular (R),  gabion walls (B = Width, D= Depth)



                        Slope expressed in feet per 100 feet of length.

                        Roughness coefficient assumed at n = 0.025


            Storm Flow Criteria

                        Selected for 1-year, 10-year, 25-year, and 100-year frequencies.




Storm Frequency





10 Year














Fenwick Road to



B = 0 **

B = 2.5

B = 2

B = 5

B = 3

B = 6

B = 4

B = 8

Bradford Road



D = 1.8

D = 2.6

D = 2.4

D = 3.1

D = 2.5

D = 3.2

D = 2.8

D = 3.2

   (Slope = 2.94)






















Bradford Road to



B = 0 **

B = 3

B = 2

B = 6

B = 3

B = 8

B = 5

B = 10

Ashley Road



D = 2.1

D = 2.8

D = 2.6

D = 3.0

D = 2.8

D = 3.0

D = 2.9

D = 3.0

   (A10Slope = 2.75)






















Ashley Road to



B = 0 **

B = 3.5

B = 3

B = 8

B = 4

B = 10

B = 7

B = 12

Farragut Avenue



D = 2.2

D = 2.7

D = 2.8

D = 2.9

D = 3.0

D = 2.9

D = 3.1

D = 3.2

   (Slope = 1.54)






















Farragut Avenue to



B = 0 **

B = 3

B = 3.5

B = 8

B = 4

B = 9

B = 6

B = 12

Steeping Stones



D = 2.1

D = 2.8

D = 2.6

D = 2.8

D = 2.8

D = 2.9

D = 3.0

D = 2.9

   (Slope = 2.67)






















Stepping Stones to



B – 0 **

B = 4

B = 6

B = 10

B = 8

B = 12

B = 10

B = 15

Farragut Parkway



D = 2.5

D = 2.9

D = 2.7

D = 3.0

D = 2.8

D = 3.1

D = 3.1

D = 3.2

   (Slope = 1.77)












            Examination of the above requirements, even for a 10-year frequency, by comparison with existing conditions, indicated the following:


1.       The needed size to carry design storm flows would exceed existing channel dimensions even for the 2-year storm.  This would require extensive excavation and channel re-shaping.

2.       Construction activities would require access widths of 15 to 30 feet.

3.       The environmental damage would far outweigh the gains in capacity.


Accordingly, the alternates chosen for study were retained largely in the public rights-of-way, and not through developed private property.


*  Costs of channelization can be furnished if needed.  But the general use of new channelization is unlikely.

** Triangular

Selection of Design Frequency


            As originally proposed, consideration was to be given to the 2-year, 5-year, 10-year, 50-year, and 100-year return frequencies.


            It was quickly realized that planning for the extremes would not be fruitful.  At the 2-year and 5-year levels, the cost of infrastructure would far outweigh the benefits derived.  There would be little effect on storm frequencies exceeding these levels.


            At the other extreme, costs for 50-year and 100-year infrastructure were found to be excessive.  Indeed, the pipe sizes at certain locations could not be accommodated without major utility relocations.


            Detailed studies were first performed using flows at 25-year frequency.  However, construction and capital costs were found to be prohibitive.  Therefore, the major sizing of drainage pipes was limited to a 10-year storm frequency, with 25-year capacities only at culverts. (It should be noted that larger storms would surcharge the system somewhat, but conditions would be much improved over existing conditions.)


Alternate ABranford Road Bypass (ref. Plates 3, 4 & 5).


            This initial plan included the following basic elements:

a)       Curbing along Ravensdale Road.

b)       Ponding in Dan Rile Park

c)       Relief storm drain along Branford Road.

d)       Partial removal of wall at #32 Fenwick Road.

e)       Additional drain piping through the side yard of #32 Fenwick Road and into the rear yard of #30 Branford Rd.

f)         Enlarged culvert across Branford Road.

g)       Curbing along Farragut Parkway.


The primary intent of this plan would be diversion of major storm water along Branford Road to reduce the flow concentration at Fenwick Road.  Storage in Dan Rile Park would replace the lost storm water storage in Fenwick Road, thus avoiding any increase in downstream runoff.


During lesser storms (say 2-year to 5-year frequency), runoff would initially be stored in a detention pond behind the proposed berm (see Plate 3) in Dan Rile Park.  Pond discharge would continue, at a reduced flow rate, through an 8-inch polyvinyl chloride bottom drain into the existing 18-inch drain in Fenwick Road.


With increased storm runoff, flow would pass over a side overflow weir, into the relief drain, discharging at Branford Road.  If storms exceeded a 10-year frequency, water would pass over the berm via an emergency spillway, then would flow overland along Fenwick Road as before, but reduced by the relief drain’s bypassing condition.


To provide capacity for a 25-year storm, the relief sewer would have to be 54-inch diameter reinforced concrete pipe.  As depicted herein (Plate 3), the bypass would be 42-inch diameter, to handle a lesser 10-year storm. Borings indicate the presence of rock at 7-foot depth (Plate 12), which adds to the cost of this approach.  Energy dissipation would be accomplished with a drop manhole upstream of the culvert.


To reduce flooding in Branford Road (and upstream), the inadequate 24-inch culvert would be replaced with a 4-foot by 10-foot box culvert, suitable for a 25-year flood, with a flared downstream headwall to reduce velocities.  A double inlet would handle street runoff.


Inlets are planned, under this approach, at the intersection of The Fenway and Branford Road, to divert surface runoff into an underground drain.  This would minimize yard flooding at #40 Branford Road.


Costs under Alternate A are estimated at $484,200 for construction, and $604,600 for capital costs.  (Table 1A).


Alternate BFarragut Avenue Bypass (ref. Plates 6 through 9)


            Under this alternative, a comprehensive plan was developed to include solutions for all known areas of flooding damage.  The elements of Alternate B include the following:


a)       Curbing along Ravensdale Road.

b)       Ponding in Dan Rile Park.

c)       Relief drain along Branford Road, The Fenway and Farragut Avenue.

d)       Partial removal of wall at #32 Fenwick Road.

e)       Additional drain piping through the side yard of #32 Fenwick Road and into the rear yard of #30 Branford Road.

f)         Enlarged culvert across Branford Road.

g)       Curbing along Farragut Parkway.

h)       Berm construction  at the south end of the municipal property, creating an impoundment north of Stepping Stones. (Plate 8).

i)         Bypass storm drain along Nepperhan Avenue, including an open channel connection to the existing waterway south of Nepperhan Avenue. (Plates 8 & 9)



This comprehensive plan would prevent ponding at Fenwick Road, and would divert storm flows away from properties currently flooded between Fenwick Road and Nepperhan Avenue.  There would also be flood relief at Stepping Stones and at the properties to the south.  For purposes of this study, capacity of the facilities are based upon a 10-year frequency storm.


Operations at Dan Rile Park would be similar to those described for Alternate A.  The impoundment north of Stepping Stones would diminish flood discharge, with overflows into the bypass drain along Nepperhan Avenue.


Costs under Alternate B are estimated at $1,040,400 for construction, and $1,294,600 for capital costs.  (Table 1B).


Alternate C – Minimum Project  (ref. Plate 10)



            This alternative was developed with the view of eliminating the worse known problems, and at a reduced cost for the project.  Following are the elements included:


a)       Curbing along Ravensdale Road

b)       Ponding in Dan Rile Park.

c)       Partial removal of wall at #32 Fenwick Road.

d)       Additional drain piping through the side yard of #32 Fenwick Road and into the rear yard of #30 Branford Road.

e)       Enlarged culvert across Branford Road, with street inlets.

f)         Curbing along Farragut Parkway.

g)       New storm drain from Dan Rile Park and along Fenwick Road.

h)       New drainage facilities in Branford Road, including regrading of road

i)         Curbing along Fenwick Road, to hold runoff in the street.


Many elements of this plan are identical with the previously described improvements.  But the expensive relief sewers are eliminated to reduce expense.


As before, detention at Dan Rile Park would be beneficial during low frequency storms, or during the initial period of a more severe storm.  During 10-year frequency storms, the new 42-inch drain along Fenwick Road, connected to the new facilities at 32 Fenwick Road, will prevent most flooding at the low point in Fenwick Road.


The proposed inlets and drain in Branford Road will diminish the flooding problem on the north side of Branford Road.  Much of the upland flow would be collected at inlets located at the intersection of Branford Road and The Fenway.  Then, curbs along the easterly side of Branford Road would further limit flooding of properties.  Finally, the high point opposite #33 Branford Road would be re-graded, thus allowing surface flow to pass downhill to the new culvert.


            Costs under Alternate C are estimated at $436,200 for construction, and $544,000 for capital costs.  (Table 1C).


Alternate D – “Barebones” Plan (See Plate 11)



            A question was raised as to the effect of an extremely limited project.


Under this alternate, only the following work would be included:

a)       Curbing along Ravensdale Road.

b)       Partial removal of the wall at #32 Fenwick Road.

c)       Enlarged culvert across Branford Road.

d)       Curbing along Branford Road; and re-grading of road.

e)       Curbing along Farragut Parkway.


In all matters, this alternate creates only partial solutions.  More important, the existing ponding in Fenwick Road would not be replaced by detention in Dan Rile Park, thus increasing initial downstream discharge.


      Costs under Alternate D are estimated at $124,300 for construction, and $154,100 for capital costs. (Table 1D).


Other Considerations


            The importance of confining flow to Ravensdale Road, thus limiting inflow to the Fenwick Road basin, cannot be stressed sufficiently.  By the proper placement of curbs along the south side of Ravensdale Road, large portions of the drainage area can be diverted in an easterly direction.  This would also diminish the damage to properties between Ravensdale and Fenwick Roads.


            The intersection of Kent Avenue and Ravensdale Road needs attention, in order to prevent runoff along Kent Avenue and into the Fenwick Road basin.  For this purpose, it is proposed that a new double inlet be placed on Ravensdale Road (with curbing), at the southwest corner of Kent Avenue, to cut off such runoff.


            Further east, along Ravensdale Road, there is a concern about the effect of increased runoff on a fronting property at an outside curve.   To offset this effect, new curbing should be installed on the south side of Ravensdale Road, east of Kent Avenue.


            Similarly, it is important to hold surface runoff along Farragut Parkway, to limit discharge to the stream above Stepping Stones. Curbing should be effective for this purpose  (see Plate 8).  Discussions with officials of the State Department of Transportation indicate the probability that such an installation would be acceptable.          

Environmental Concerns


            In reviewing elements of this study, cautions have been expressed about the landscaping, shrubberies, and even the major trees found along the stream banks.  Property owners throughout the area prefer to sustain a flood effect, rather than to disturb the plantings and underbrush.


            Channels are generally undersized and overgrown.  The Hazen & Sawyer report (Appendix C) offered the solution of channel improvements throughout the area, but apparently did not recognize the property owner reactions to such a devastating approach.


            Instead of channel work, this study concentrates on diminishing of flow from fringe areas, culvert enlargements, and detention.  This approach minimizes environmental effects, if not providing for full storm water protection.


            Other environmental concerns are common to any construction project.  There are inevitable nuisances to be expected from noise, dust, and traffic blockage.  The proper remedies lie in strictly enforced technical specifications, wherein measures for noise and dust control are stressed.  Traffic problems can best be minimized through cooperation with the police department, and the assignment of traffic control officers.


Stepping Stones Dam


            Much attention has been given to the Stepping Stones dam, with the following conclusions:

a)       The backwater effect from the dam is pronounced, affecting flood levels at several upstream properties.  But the backwater surface dissipates, even at 100-year frequencies, a short distance upstream of the Stepping Stones driveway, in the Village property.

b)       The effect of the dam is not only to establish flood levels, but also to create a stilling pond which encourages siltation.  Currently, the silt levels diminish the pond’s usefulness for swimming or for fish life.

c)       Reduction of the dam height would benefit the fronting properties and would eliminate siltation.  But, the pond would disappear (except during storms).  More importantly, the equipment needed to shift the huge blocks comprising the dam, would severely damage the landscaping and stream environment.

d)       The affected property owners have stressed their preference for an undisturbed condition, and a willingness to accept current levels of flooding.  However, they have stressed their objection to any upstream improvements which would increase stream flows.

e)       The culvert under the Stepping Stones driveway should be cleaned frequently, to minimize flooding.

f)         The Stepping Stones property owners should be advised of the following long term remedies:

1.   Dam reconstruction to provide for a manually (or motorized) operated sluice gate, to permit passage of storm flows.  Cost for such a gate would be in the order of $25,000.

2.   Installation of a level controlling gate, similar to that manufactured by the Waterman Co.  Cost of a small unit would be in the order of $55,000.


            In view of the expressed preference of the Stepping Stones property owners, and of the property owners upstream of the dam, it would appear preferable for the Village to defer any action in this area.  If flooding is to be reduced, it should remain the dam owners’ responsibility.


The opinion rendered to the property owner by the District Conservationist (Appendix D) should be reiterated… “The cost of all this … to save the pond may be more than you wish to bear….”



Comparison of Flood Relief


            The most comprehensive plan lies in Alternate B. By use of a bypass drain along Farragut Avenue, the entire upper flooded area would be relieved of excess flow.  Further, by the installation of a detention basin on Village property near Farragut Avenue, and a bypass drain along Nepperhan Avenue, the lower area would be bypassed.  If this solution could be afforded, the result would be most beneficial.


            An effective, but somewhat lesser solution would be the Branford Road bypass, presented in Alternate A.  No relief is provided for the Nepperhan Avenue area, but flooding (up to 10-year frequency storms) would be relieved in the Fenwick Road and Branford Road areas.


            The approach shown in Alternate C has the benefit of reducing the worst flooding effects, at Fenwick Road and Branford Road, but provides for little improvement further downstream.  However, the diminution of inflow from Ravensdale Road and Farragut Parkway should have a salutary effect on the entire basin.


            The inclusion of Alternate D is intended to illustrate the limits of minimization.  Scant relief would be secured from flooding, and there would be increased discharge downstream for lack of storage at the head of the watershed.


Comparison of Costs


            As would be expected, the most comprehensive program carries the greatest cost, and the least program would require the least cost.


            Following is a summary of the estimated construction and capital cost (for details, see Tables 1A thru 1D):

                                          Alternate A            Alternate B         Alternate C         Alternate D

                                                        (Bradford Road            (Farragut Ave            (Minimum                  (Barebones

                                                             Bypass)                       Bypass)                        Project)                          Project)



                Construction Costs     $484,200                       $1,040,400               $436,200                   $124,300


                Capital Costs               $604,600                       $1,294,600               $544,000                   $154,100



Comparison of Benefits


            Least benefit is derived from Alternate D, since minimal improvements are planned for any affected areas.  There will be some diminution of flooding by diversions on Ravensdale Road and Farragut Parkway.  Also, the wall removal at #32 Fenwick Road (Chettih) will diminish Fenwick road flooding.  But downstream conditions will worsen.


            Alternates A and B provide significant benefit by diverting flows around the most seriously affected areas.  Alternate B adds flood relief in the Nepperhan Avenue area as well.


            Alternate C benefits the Fenwick Road properties by affording adequate detention and relief drainage.  The flood damaged properties on the north side of Branford Road would be relieved as well (as in Alternates A & B).

Comparison of Environmental Damage


            Sensitivity to the environment in this drainage basin has been stressed from the initiation of the project.  Most of the riparian owners have expressed concern about their landscaping being damaged by any flood control project.


            Accordingly, solutions herein have generally avoided extensive channel improvements, or on-site disturbance.  Projects are mostly planned in roadways, or on public property.


            The notable exception lies in the property at #32 Fenwick Road (Chettih), where a new drain is proposed (under Alternates A, B and C).  But even here, the existing stream bed would remain untouched in view of the extensive shrubbery growing along the low area on the westerly property line.  By placing a single large drain in the open grassed area, there would be the least environmental effect on the property, and on the visual shield provided by the existing plantings.  And, the existing drain nearest to the house would be abandoned.


            Common to all projects are the problems of noise, dust, and traffic blockage.  The smallest project (D) would therefore have far fewer such problems than the largest project (B).  But with proper specification control, the selection of a project in this study need not be based upon environmental problems.


Need for Easements


            In some projects, land acquisition may be a controlling factor in the selection of a best alternative.  In this study, however, the need for real estate acquisition is minimal.


            The need for easements at #32 Fenwick Road (Chettih), and at the rear of #30 Branford Road (Ratzenberger), is common to Alternates A, B, and C.  Hopefully, this need can be met through the following process:

a)       Detailed surveys, and preparation of large scale plans.

b)       Final design, considering all environmental factors, access, specification controls, restoration requirements, etc.

c)       Consultation and negotiation with property owners.

d)       Preparation of “metes and bounds” descriptions, easement language, title search, etc.

e)       Final acquisition, by consent agreement or (as a last resort) by condemnation.


Since the affected property owners have been consulted as part of this study, it is hoped that a harmonious easement acquisition will be possible.




            Alternate A requires a commitment to the Branford Road relief drain, which is the major financial expenditure.  Therefore, phasing would not be of great effect.


            Alternate B is the most comprehensive project, requiring a commitment to the expensive Farragut Avenue relief drain.  Phasing would be possible by elimination of the southerly improvements:  Nepperhan bypass drain, and the detention pond north of Stepping Stones.


            Alternate C can be deferred, in part, by postponing the Branford Road drainage improvements.  This would permit an initial savings in the order of 58%.  However, splitting of these projects would involve additional costs for re-mobilization, separate bidding, overhead, etc., thereby diminishing the phasing benefits.  (See more detailed discussion later.)


            Alternate D is in itself a phasing operation, and no deferrals are possible.


Overall Evaluation


            Using the criteria outlined above, a possible means of comparison would be the following matrix:



                                                                        Minimum         Moderate         Maximum


            Alternate A

               Flood relief                                                                       X

               Costs                                                                                                       X

               Environmental Effect                                                          X

               Property Benefits                                                              X


            Alternate B

               Flood Relief                                                                                              X

               Costs                                                                                                       X

               Environmental Effect                                                          X

               Property Benefits                                                                                      X


            Alternate C

               Flood Relief                                                                      X

               Costs                                                                               X

               Environmental Effect                                                          X

               Property Benefits                                                              X


            Alternate D

               Flood Relief                                              X

               Costs                                                       X

               Environmental Effect                                  X

               Property Benefits                                      X






            Assuming that maximum cost and/or minimum benefit would weigh against acceptance,  Alternates A, B, and D fail by comparison.  Alternative C  offers moderate flood relief and cost, but with at least moderate benefit to properties.


            Therefore (in terms of the Village’s 2002 Request for Proposals), the selection of Alternate C will provide the “maximum practical level of protection” against the flooding of homes and streets along the main drainage channel.  The use of 10-year frequency storm flows for the primary infrastructure is most effective, considering the facilities made available (such as overflow weirs) for higher frequency storms.



Capital Costs and Amortization


            Contacts were made with various agencies to determine the availability of grants or loans for the project.  Unfortunately, no aid appears to be available for such projects.


            Currently, municipal projects are at an extremely low financing cost.  Recent Village projects were reported as follows:


            Year                 Location                        Term              Amount            Average Interest Rate

            2003           Refinanced Bonds                11 years,           $1,790,000        2.65% interest

            2002           Four Municipal Projects        Short Term        $   827,000        1.55% interest

            2001-3        LibraryAntic’n. Notes        1 year               $1,400,000        1.32% to 3.20% interest


            Construction costs are reported in this study (see Tables 1A to 1D) based on an assumed construction period for early 2004.  Since project design remains preliminary, a contingency allowance of 10% is allowed to cover unforeseen costs.


            In several of the projects, allowance is made for real estate costs.  Primarily, this involves the acquisition of easements.  Estimates of cost are based on recent costs for easements over residential properties, with allowances for fees, filing, etc.


            Other costs must be added, in order to determine the total project cost:


                     Engineering and Surveys                @ 11%

                     Construction Phase Monitoring       @  9%

                     Legal, Advertising, Bonding, etc.     @  3%

                     Administrative and Accounting        @  1%


            Assuming equal annual payments*, an interest rate of 2%, and a 20-year amortization, the anticipated annual costs may be evaluated as follows:


                                                                              Total Capital Cost**         Annual Amortization


                     Alternate A ………………….                $  604,600                                 $37,000


                     Alternate B ……………………………...$1,294,600                                 $79,200



                     Alternate C ………………….                $   544,000                                $33,300


                     Alternate D ……………………………...$   154,100                                 $ 9,400













*  Actual amortization may incur higher initial debt service, and lower final debt service.  The “equal annual payment method” is provided for ease of project comparison.


**  Note that allowance may be needed for “interest  during construction”, say 1.5% for one year, depending on the method of financing.




            The Village is authorized, by State statute, to assess properties for special benefits derived from a publicly financed project.  The special benefits may be evaluated in several ways:

a)       By stream frontage.

b)       By property valuation before and after project construction.

c)       By evaluation of damages from flooding which are eliminated by the project.


            It may also be possible to establish an “improvement district”, and to assess all properties within the district for benefits derived.


            After some study, it becomes apparent that an assessment program in the affected area would have enormous technical and political barriers.  There is no known method of assessing drainage projects which is not subject to challenge.  For example, stream frontage is not a suitable criterion since the benefits derived (or the damage eliminated) has little bearing on the length of waterway.


            More important, there is a claim from many property owners that the flooding causes little damage, even under extreme storms.  Moreover, the damage which could be caused by construction of improvements may well outweigh the benefits to property value.


            Accordingly, it is recommended that the project be considered of “general benefit” to the community, rather than of “special benefit”, thus avoiding the need for local assessments.


Phasing of Alternate C


            Assuming the selection of Alternate C by the Village Board of Trustees, the financing burden can be eased through a multi-year program, as follows:


§         Initial                Culvert enlargement at Branford Road

                    Curbing along Branford Road, and road regrading                       

                    Berms and curbs along Ravensdale Rd. & Farragut Pkwy.

                    Partial wall removal at #32 Fenwick Road

                    Detention pond at Dan Rile Park (reduced size) *                        $271,983


§         Interim             Improvements along Fenwick Road,

                    Facilities through #32 Fenwick Road                  .                       $144,245


§         Near Future     Drains and inlets along Branford Road                                        

                                Enlarged detention at Dan Rile Park (if required)                         $127,772



            It is urged that  the overall design be accomplished initially, in order to insure an integrated ultimate project.  Phasing can then be accomplished through contract subdivisions.


            It should be realized, however, that phasing will add to the project cost for several reasons: a) engineering and bidding expenses are repeated for each phase; b) contractor mobilization and demobilization costs are repeated for each phase; and c) soft costs (e.g. insurance and bonding) would be increased with multiple contracts.  Therefore, for maximum economy, the project should be instituted as a whole, without phasing.


            Further, phasing will not eliminate some of the major problems.  For example, if only the “Initial” project is undertaken, problems will continue at #32 Fenwick Road (Chettih), at #30 Branford Road (Ratzenberger), and at other homes along Branford Road.


*  Detention volume would be reduced to match the current ponding volume at the low spot in Fenwick Road (0.3 acre feet).





            The State Department of Environmental Conservation has advised that no wetlands permits will be required, since the project site is not located within a “Protected Fresh Water Wetland”.


            The U.S. Army Corps of Engineers has advised that there are no wetlands requirements within their jurisdiction.


            The State Department of Transportation indicated that it will require a permit for any curb or berm placement along Farragut parkway.  No extensive difficulties are anticipated.


            The State Department of Environmental Conservation may require an application under the State Environmental Quality Review Act (SEQRA).  A decision on the review will be made upon completion of contract documents.


            The Village Planning Department should receive notice of the impending improvements.


Collateral Matters


            A concern was expressed by the property owner at #1 Ashley Road (Gross) about a serious toilet surcharge experienced during Hurricane Floyd.  Our work on this study indicated that a pipe connection probably exists between a sanitary sewer manhole in Ashley Road, and the nearby storm water culvert.  It is important that this illicit cross-connection be dye tested, and correction made if necessary.  A similar complaint was made at #28 Fenwick Road (Boccumini), which needs investigation.


            Storm drain maps in the area are incomplete and may also need correction.  New mapping would be desirable, preferably using GIS procedures.


            Similarly, maps of the sanitary sewer system need updating and clarification.  In addition, the Village should consider a “cursory” *infiltration/inflow study, to reduce sewer flows during storm periods.


            Consideration should be given to the adoption of a zero runoff ordinance, limiting surface discharge from newly installed impervious areas.  This would ultimately provide seepage pits, or other means of restricting surface runoff, for the future benefit of the waterways.


            The importance of maintenance, for drainage pipe, culverts, and inlets, must be emphasized.  At least monthly, and after storms (particularly in the fall), there must be inspection and cleaning to insure full capacity for the next storm.  Of particular importance is the bar rack just north of Ashley Road, which requires frequent attention.  Property owners claim that other drainage facilities in the area need more frequent inspection and cleaning.


            There is a blocked concrete culvert at the most downstream crossing of Farragut Parkway.  The State Department of Transportation should be notified of the need for maintenance at this location.










*   “Cursory” study only requires night observation of sewer flows during wet weather, using prescribed guidelines. 

       More intensive television observation is then required only in the most critical areas.






            Based upon the matters described before, the conclusions of this study may be summarized as follows:


a)       The Village authorized an investigation of the flooding along an unnamed stream, extending from Fenwick Road to Farragut Parkway.

b)       Flooding is worst in the Fenwick Road area, but extends into yards throughout the area, with some basement flooding as well.

c)       Prior studies were performed by the District Conservationist at the Stepping Stones area; by the consulting firm of Hazen & Sawyer for the entire basin; and by a White Plains engineer at Ashley Road.  Except for some improvements at Ashley Road, no flood alleviation work was done.

d)       Surveys were prepared, borings were drilled, and mapping obtained from various sources, in preparation of this study.  Of greatest value was the input of local residents.

e)       A detailed survey was made of existing flood conditions under various storm frequencies (see text).  The condition is considered tolerable in all areas except Fenwick Road.

f)         Hydraulic calculations were prepared to determine drainage areas, and estimated tributary flows at various storm frequencies.  Gradients were cross-checked with reported flood levels to insure accuracy of the modeling.

g)       Consideration was given to channelization, but the environmental degradation would be excessive; therefore, improvements are considered (for the most part) in public rights-of-way.

h)       In reviewing design criteria, the optional storm return frequency was selected as 10 years for pipe lines, and 25 years for culverts.

i)         The following alternative plans were studied in detail:

A.      Branford Road Bypass – Utilizing a relief sewer along Branford Road to reduce

  upstream flooding.

B.      Farragut Avenue Bypass  - Utilizing a relief sewer along Farragut Avenue to reduce flooding from Fenwick Road to Farragut Avenue; also a relief sewer in the Neppherhan Avenue area.

C.      Minimum Project – Limited improvements, sufficient to reduce the worst flood conditions.

D.      “Barebones” Plan – An extremely limited project, creating only partial solutions.

j)         Evaluations indicate the importance of confining flow along Ravensdale Road, and along Farragut Parkway, to limit flow into the area.  To minimize environmental damage, improvements should generally be confined to public roadways.

k)       The Stepping Stones dam creates flooding to just north of the Stepping Stones driveway.  The best solutions would be either lowering of the dam, or utilizing level controls, any of which would be costly to the property owners, and damaging to the environment.  No public improvements are planned in this area.

l)         In comparing the alternates, it may be noted that Alternates A and B are the most comprehensive, but are heavy in capital cost, perhaps beyond acceptable municipal limits.  Conversely, Alternate D accomplishes little, and worsens downstream conditions.

m)     Overall, Alternate C appears to present reasonable flood relief, at moderate cost.  If desired, phasing is possible.  Therefore, Alternate C is the recommended approach.

n)       Capital costs for Alternate C are estimated at $544,000, and the annual amortization would be $33,300.

o)       Assessment financing is not recommended, in view of the great difficulty in establishing “special benefits”.

p)       Permit requirements should not be onerous.  Application will be required to the State Department of Transportation, and to the State Department of Environmental Conservation (re. SEQRA approval).

q)       Other matters are offered for consideration:

§   Improved drain and sewer mapping.

§   Disconnecting of illicit sewer connection.

§   Cursory infiltration / inflow study.

§   A “zero run-off” ordinance should be considered.

§   Culvert maintenance must be stressed, including the blocked concrete culvert under Farragut Parkway.





            Successful completion of this study would have been impossible without cooperation and input from the following parties:


  • David Walrath, former Trustee
  • Michael Gunther, Supt. of Public Works
  • Neil P. Hess, Village Manager
  • Michael Holdstein, Village Trustee
  • Susan Maggiotto, Village Clerk
  • Rafael Zaratzian, Village Technology Director
  • Area Residents – who appeared on several occasions (on rainy days) offering information.
  • Board of Trustees - providing input and comment at several public meetings.






  1. The study should receive scrutiny and input from the Board of Trustees and Village officials.
  2. The conclusions of the study should be publicized, and made available for public comment.
  3. Official approval should be given to the selected project, and capital funding should be authorized.
  4. Preparation of detailed design and bid documents should be authorized, with phasing as desired.
  5. Final cost estimates should be prepared, and bond anticipation notes should be funded.
  6. Easement acquisition should be negotiated.
  7. State approval should be obtained, from the Dept. of Transportation for work in Farragut Parkway, and from the State Dept. of Environmental Conservation for the SEQR environmental process.


  1. Bids should be obtained, and an acceptable low bid should be awarded.
  2. Construction should be completed, with appropriate field supervision.
  3. Separate consideration should be given to improved utility mapping, and to infiltration/inflow studies.