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HomeMy WebLinkAboutSCWA - Public Water Supply Master Plan for TOS - 7/1992LEGGETTE, BRASHEARS & GRAHAM, INC. PROFESSIONAL GROUND-WATER CONSULTANTS MASTER PLAN FOR PROVIDING A PUBLIC WATER SUPPLY TO THE TOWN OF SOUTHOLD, NEW YORK PREPARED FOR SUFFOLK COUNTY WATER AUTHORITY JULY 199~.- I'tAY g 8 1998 WILTON CONNECTICUT ST. PAUL' TAMPA FISHKILL MINNESOTA FLORIDA NEW YORK RAMSEY NEW JERSEY EXTON SIOUX FALLS PENNSYLVANIA SOUTH DAKOTA ALBUQUERQUE NEW MEXICO NASHUA NEW HAMPSHIRE I I I I i I I I I I i I I I I I I i I LEGGETTE, BRASHEARS & GRAHAM, INC. PROFESSIONAL GROUND-WATER CONSULTANTS R. G. SLAYBACK G. SIDNEY FOX FR AN~K H. CRUM MICHAEL R. BURKE ROBERT LAMON1CA WILLIAM K. BECKMAN DAN C. BUZEA July 28, 1992 JOHN NA$O, YR. Mr. Edward Rosavitch, P.E. Chief Engineer Suffolk County Water Authority 4040 Sunrise Highway Oakdale, NY 11769 Dear Mr. Rosavitch: Enclosed for your use are twelve (12) copies of our report "Master Plan for Providing a Public Water Supply to the Town of Southold, New York". Bob Lamonica or I will be pleased to respond to questions or comments. We hope this document is responsive to your needs. Very tr~.:!y yours, LEGGETTE, BRASHEARS & GRAHAM, INC. RGS:skd Enclosures sufcon.ltr/92-34 MASTER PLAN FOR PROVIDING A PUBLIC WATER SUPPLY TO THE TOWN OF SOUTHOLD, NEW YORK P~mred For Suffolk County Water Authority July 199'2 LEGGETrE, BI~_S~ & GRAHAM, INC. Professional Ground-Water Consultants 72 Danbury Road Willon, CT 06897 I1 II II II I1 Il II II ! ! i i 1 I i I MASTER PLAN FOR PROVIDING A PUBLIC WATER SUPPLY TO THE TOWN OF SOUTHOLD, NEW YORK SUMMARY The Upper Glacial aquifer in the Town of Southold contains a series of fresh- water lenses separated by tidal creeks or inlets. Development of ground water for public supply purposes is feasible in the lens areas, but individual well withdrawal rates will be smaller than in western and central Suffolk County to minimize the threat of salt-water inlxusion by lateral encroachment or vertical upconing. A widespread interstadial clay offers greater protection from upconing on the North Fork than exists in the Montauk area. The largest present water use in the Town is for seasonal agricultural irrigation, a largely consumptive water use, that is forecasted to decrease in future years. Public water-supply usage will be mainly non-consumptive, as most of such usage is returned to the ground by septic systems. Six prospective public water supply well-field sites have been identified in the western sector of the Town of Southold, with a preliminary yield potential of 3.2 mgd (million gallons per day). Individual well yields are estimated to range from 200 to 625 gpm (gallons per minute). Each of the sites meets the Water Authority criterion for tank overflow elevation at or near the well-field location. The chosen well sites are mostly located on the southerly side of the fresh-water lenses, so as to minimize water main distances to population centers which are mainly along the Peconic Bay coast. Eventually, a transmission main could provide a continuous interconnection from the Riverhead system to the Greenpofi: Water District, and perhaps eventually to Orient. A prospective well site of modest yield potential (110 gpm) has been identified in the Orient area. Ground-water quality on the North Fork has been adversely impacted by agricultural chemicals. Although it is possible that concentrations of such chemicals of any given well site may not exec~'~_ drinking w~t_~ limits, the Water Authority should plan on treatment for nitrate removal and for removal of pesticide, herbicide and fungicide residues. Naturally-occurring iron and/or manganese concentrations may also require water treatment. LEGGt=i l~ BRASHEARS & GRAHAM, INC. II il ! ! I ! I I I 1 I I -2- INTRODUCTION On May 5, 1992, the Southold Town Board adopted the following resolution: WI~REAS, the Town Board is responsible for the health, safety and welfare of its citizens; now, therefore, be it Ri~OLVED that the Town Board of the Town of Southold hereby endorses a study of a pilot plan by the Suffolk County Water Authority to provide public water to the people in the area from the vicinity of the Riverhead Town boundary, South of the Long Island Rail Road, up to the vicinity of Bay Avenue in the Mattituck area, subject to the Town Board reviewing and approving the survey before it is released; and BE IT FURTHER RF-qOLVED that the Town Board endorsea an initial study by the Suffolk County Water Authority of water needs to serve Cutchogue and New Suffolk. As a responsible provider of a safe and plentiful supply of water to over one million people in Suffolk County, the Suffolk County Water Authority believes it is prudent to anticipate the needs of the entire North Fork of Long Island so that, if the need arises in the future, they are in a position to expand the initially envisioned pilot- area system. As part of a coordinated effort to generate a Master Water Supply Plan for the Town of Southold, the Authority requested that Leggette, Brashears & Graham, Inc. (LBG), Professional Ground-Water Consultants, prepare a water availability study. No specific attention has been given in this study to the area served by the Greenport Water District, but this district could eventually be integrated into a townwide distribution systenl o The elements of the study include determination of the safe yield of the aquifers underlying the town, estimation of current usage, determination of the optimum locations for water-supply wells and storage facilities, and review of potential water quality in future production wells. POPULATION AND WATER USE Population in the Town of Southold in 1990 was listed by the U.S. Census Bureau as 19,836 persons. The LILCO estimate for Januar3, 1, 1991 was 19,831. The U.S. LEGG~.I ~.~, BRASHEARS ~ GRAHAM, INC. -3- Census data break out as follows by geographic areas according to "Census Designated Places' (CDPs), which are not n~ly political boundaries. SOUTHOLD TOWN U,S. CENSUS ESTIMATES Geographic Area [ 4/1170 4/1/80 Laurel598 962 1,094 Mattituck 3,039 3,923 3,902 Cutchogue - New Suffolk 2,718 2,788 3,001 Peconic 835 1,056 I, 100 Southold 3,749 4,770 5,19'2 Greenpon West 1,682 1,571 1,614 (unincorporated) Grcenport Village 2,481 2,273 2,070 (incorporated) l~a~t Marion - Orient 1,240 1,511 1,534 Fishers Island 462 318 329 Totals 16,804 19,172 19,836 For the area of the Town of Southold west of the service area of the Grcenport Water District, the first four listings - Laurel to Peconic - show a 1990 population of 9,097, about 46 percent of the Town po[relation. According to LILCO; the 1991 population estimate represents 8,229 households, of which 3,774 are located in the four western CDPs; 46 percent. The summer-season population is not so clearly known, but the North Fork Water Supply Plan (NFWSP) provided estimates from the Suffolk County Planning Board of a townwide summer increase of 19,760 in 1980, slightly more than double the year-round population. These increases are dominated by second home and summer guest populations, but also include motel and camping visitors. I1 II II I1 ! ! ! I i i 1 1 i i -4- Per-capita water use in 1980 in the Greenport and Riverhead Districts was listed in the NFWSP as 110 and 120 gpd (gallons per day), respectively. With a year-round population of 20,000 in the Town of Southold, this transhtes to 2.2 to 2.4 mgd of domestic water use. Present summer-soa,.on domestic water use would be expected to be essentially double these values. Based on the water-supply experience in the Montauk area, a growth in summer-vacation home populations could lead to seasonal water use approaching four times the year-round rates. For the four western CDPs, the Greenport and Riverhead per-capita usage figures correspond to a demand of about half the townwide values. At present, these water demands are being met by individual domestic supply wells, with the exception of the Captain Kidd Estates water system which is operated by the Suffolk County Water Authority. The initial pilot-project plan announced by the Water Authority is to extend a main from the Riverhead system along Peeonic Bay Boulevard east to Bay Avenue, with the expectation of serving a substantial number of residences and businesses from the Long Island Railroad/Route 25 area south to Peconic Bay. This area involves approximately 800 property owners, and is known to have a history of private well contamination with nitrates and/or pesticides, as well as high iron content. It is anticipated that new well sources would be developed within about three yors and that the initial pilot project would be expanded to the north and east. WATER-SUPPLY AVAILABILITY The hydrogeologic framework of the North Fork of Long Island has been studied for the past 35 years by the United States Geological Survey and other concerned agencies. The reference list of this report illustrates the coverage of the various studies. Fresh-water supply in the Town of Southold is derived from local ground water in the Upper Glacial aquifer. The Magothy aquifer contains salt water throughout the North Fork. Available studi~s indicate that there is a surplus of shallow ground water available for development, but that care must be taken to avoid unnecessary water-quality problems related to agricultural land use and potential salt-water encroachment. LEGG~-~ ~,'~ BRASHEARS & GRAHAM, INC. -5- The most important recent finding concerning water availability is that there is an areally extensive clay layer, previously only inferred, extending from Riverhead at least as far east as Richmond Creek (NFWSP, 1980, Bohn-Buxton et al., in press). This interstadial clay is present at approximately 50 feet below sea level in the Laurel/Mattituck area, sloping northerly and easterly to about 100 feet below sea level in Shore Acres/Wolfpit Lake and in Cutchogue. Its thickness varies from about 20 feet in the west to as much as 90 feet in Cutchogue. Figure 4-1 from the ~SP is appended to this report, a longitudinal section from Riverbead to Orient which shows the relationship of this clay to the fresh-water lenses. There is also a lower interstadial clay unit, but it is below the fresh-water/salt-water interface over much of the study area. The presence of the upper clay unit limits the potential for upconing of salty water beneath production wells. As with most coastal ground-water resources, the key availability parameters are aquifer transmissivity and individuni-well yield potential, volume of (fresh) water in aquifer storage, and recharge rates. On this peninsula, which functions hydrogeologically like an elongated oceanic island, a series of fresh-water lenses float on a large body of underlying salt water, with lateral separation and salty zones between the lenses at the major estuarine creeks. An overview of the more recent previous studies of the area summarizes the available body of knowledge on these hydrogeologic parameters. As with most hydrogeologic studies, the more recent reports are in part derivative of earlier studies. Hoffman - Bulletin GW-45 Hoffman (1961) of the United States Geological Survey, examined the specific capacity - the yield divided by the drawdown - for 77 wells throughout Southold, and found the following: I.~,~ ~ Baa.Sim.~lts & Ga~n~/nc. I I II I I -6- Range in specific capacity Percent of wells (gpm/ft!~) 40 or more 14 30 to 39 20 20 to 29 45 10 to 19 2O ~ than 10 I J./ Gallons per minute per foot of drawdown. t! m~ I l I I I ! Thus, there is a reasonable expectation that properly designed and constructed wells will have specific capacifes greater than 20 gpm/~ and probably more than 30 gpm/ft, depending on local subsurface conditions. From these data, Hoffman concluded that the transmissivity of the glacial deposits *ranges from values somewhat less than 200,000 glxt per foot to values somewhat greater". He further noted that the coefficient of permeability may range between 1,000 and 5,000 glxt per square foot. With reference to storage, Hoffman utilized a specific yield of 0.17 and the Ghyben-He~rg p~ciple to estim~'~ i~e torte ~re~h ~_"e,??-,,."~'- ?~.~e on the mainland pan of the Town of Southold as 83,000 million gallons in April 1950. This may be broken out into three segments: West: Mattituck Inlet to Hashamomuck Inlet 70,000 Central: Chapel Lane, Greenport to Causeway, ~t Marion 6, I00 Orient 7,000 TOtal (rounded) ] 83,000 1_/ Million gallons. LEGG~, s~. BRASHEARS & GRAHAM, INC. -7- By far, the largest volume of fresh-water storage occurs in the west area, near Mattituck, Cutchogue, and the Village of Southold. It should be noted that Hoffman did not consider the storage in the part of the Town of Southold west of Mattituck Creek. Of his grand total, only 2,000 million gallons, or 2.4 percent, was storage above sea level, essentially in direct proportion to the Ghyben-Herzberg ratio (40: I). Hoffman estimated average annual recharge to these three areas as: west 8,6OO Central ~0 1~ 1,100 Thus, in contrast to most of Long Island, the annual replenishment is a significant percentage of the fresh-water storage, an impoCtant factor in water-supply planning. In this light, Hoffman also looked at the annual recharge during a 3-year period of minimum precipitation, in which only 30 percent of the precipitation became recharge. Ama~al recharge (mi~ MG MGD/mi: West 29.2 5,750 0.54 Central 6.7 585· 0.24z' East 4.7 715 0.42 Estimate reflects 2 mi~ area with surficial clay, assumed to have zero recharge. Thus, in an area where fresh ground-water storage is limited, Hoffman estimates a conservative drought recharge rate of about half the accepted average recharge rates for Long Island. I I i} I1 I I ii Ii -8- Crandall. USGS WSPol619-GG Crandall (1963) questioned Hoffman's assumptions about evapotranspiration rates, and calculated average recharge rates for four areas of the Southold peninsula (plus two island-peninsulas not considered here), with reductions in parts of the Greenport area to allow for local clayey sediments and paved areas. The west-central (B), central (C), and eastern (D) areas were essentially identical to Hoffman's, but a western area was added to the west of Matfimck Inlet and- extending about a mile into the Town of Riverhead. His average recharge values for Area B were less than Hoffman estimated for his West area to the east of Mattimck Inlet. ] Area I Annual recharge (MG) A (West) 1,500 B (West-Central) 5,300 C (Central) 850 D (~a~t) 1,100 TOtal 8,750 Crandall noted that recharge may range from 25 to 35 percent of the total annual precipitation in very dry or very wet years, respectively. Crandall offered his own estimates for fresh-water storage based on a larger specific yield of 0.22 and deductions for lill and clay units. His values, which are substantially larger than Hoffman's, are: Lr_x;~,g, Jr... Bv. nsar. nas& G~nM, I~c. ! Area I Fresh-water storage (MG) A (West) 46,000 B (West-Central) 134,000 C (Central), 10,400 ( ast) 10,400 Total 200,800 Nevertheless, Crandall's storage ~imates indicam that the largest fresh-water storage in the Town of Southold occurs between M_..a~dtuck Inlet and Hashamomuck Inlet. (~0mnrehensive Public Water Sun.Iv Study (CPWS-24} The Comprehensive Public Water Supply Study for Suffolk County (CPWS-24) (1968) by Holzmacher, McLendon & Murrell provided a fresh approach to ground-water supply availability by proposing 'Permissive Sustained Yields" for specific areas within the County. Permissive Sustained Yields was defined as "the maximum rate at which water can be consumed perennially without bringing about some undesired result". In effect, the estimates of Permissive Safe Yield began with area-specific recharge rates, made reductions for near-coast areas outside the main water budget area, and made further reductions based on an "optimum" position of the salt-water interface, including considerations of drought. The CPWS-24 report also defined "Average Net Yields", which were based on average-year recharge rates. For Southold, the findings were: I i1 Ii I] II Ii I] I] i] ! ! -10- ,~ Permi~'~ve P~Y per mi' Average Sustah~ed of water Net Yield Yield budget area (ANY) (m~d) (m~d/mi~) (mgd) We~t of Mattituck Creek 2 0.40 3.4 MnHtuck Creek to Hashamomuck 5.$ 0.35 10.4 Pond Hashamomuck Pond to Orient Harbor 1 0.25 2.1 l:~.t of Orient Harbor 0.5 0.25 1.1 North Fork Water Suooly Plan - SCDH~; The North Fork Water Supply Plan (NFWSP) (1983), prepared by ERM-Northeast and Camp, Dresser & McKee for the Suffolk Counvy Department of Health Services (SCDHS), offers lime new data rcla~l to basic aquifer parameters, but much useful data on historical and projected wa~r use. For ground-wa~er availability, this study reexamined and generally accepted the "Permissive Sustained Yields" from the CPWS-24 report, but adjusted the water-budget areas slightly. Table 7-4 from the NFWSP, a par~ of which is reproduced bctow, is a useful summary of the available water budget, compared to the estima~l consumptive wa~er use in 1980. LEGG,- l ~., BaASaT~aS & G~H~ I~¢. SUMMARY OF WATER BUDGET ANALYSIS (From Table 7-4, NFWSP) -11- Zone pgrmissive sustained vleld Present Potentially consump- available for tive use future use (mgd) (mgd/sq.mile) (mgd) (mgd) I - Riverhead 29.4 0.7 4.7 24.7 2 -- Riverhead & West 5.6 0.4 3.9 1.7 Southold 3 - West Central 4.9~ 0.35 3.3 1.6 4 - Central 0.9x' 0.25 0.5 0.4 5 - l:~t 0.40~/ 0.25 0.47 0~ 1._/ Since the underlying aquifers in these zones have insufficient storage, these values are conservatively based on drought conditions and would be larger for a year of average precipitation. 2_/ The zero enu3t indicates that the present consumptive use is approximately equal to the permissive sustained yield in Zone 5 during drought conditions. LBG Renorts LBG has prepared several reports on the Southold area for the Water Authority dealing with "Facwrs Affecting Water Supply Development" (1985) and site-specific reports (Mill Lane-l~89, Oregon Road-1991, Laurel Lake-1992). For these reports, the CPWS-24 "Permissive Sustainable Yields" have been adopted as the most conservative values for water-supply planning purposes~ and site-specific data have been utilized for well-field planning. The "Factors" reports dealt with the historic fluctuations of the fresh ground-water mound in the area between Mattituck Inlet and Richmond Creek, in effect the west- central, Area B, or Area 3 region of previous studies, and theoretical aspects of salt- Inc. I I] I1 I! Il It I1 I t 1 i i I -12- water upconing beneath a pumping well as related to yield and positioning of the well screen, as well as general well-field spacing. The three site-specific reports provided preliminary yield-potential estimates ranging from 175 gpm at Mill Lane, to 350 gpm at Oregon Road, to 625 gpm at Laurel Lake. In each case, consideration was given to vertical upconing and lateral encroach- ment of salt water as the potential limiting parameters. WELL-FIELD SITE SELECTION CRITERIA It is evident that salt-water encroachment, vertically and/or horizontally, is the practical limiting factor for public supply well fields. In practice, it has been found that lateral encroachment is the more limiting factor for well or well-field yield in Southold when theoretical performance is evaluated. As was determined earlier on the South Fork, this means that the optimum locations for ground-water development are along the central spine of the North Fork, where fresh ground-water mounds or lenses occur between the major creeksYtidal inlets, roughly coincident with the Long Island Railroad track. This area affords the greatest aquifer thickness and the greatest distances from salt-water bodies. However, there are other factors which have to be considered in Southold. Pouulation Centers The primaxy population centers are located along the southern portion of the town adjacent to Peconic Bay, and also along Mattituck Creek. It therefore becomes inefficient to construct well fields in the interior because of water-main length and excessive pressure losses through the transmission pipes. The well-field site selection process included placing wells in reasonably close proximity to population centers. Storaee Tanks Another factor is storage tank placement. In order to be able to integrate the Southold system with the Riverhead system, as well as other Authority systems, the tanks must have an overflow elevation of 185 feet above sea level. The tallest tanks the LEGG~.,~ ~ BRAS~ARS & GIC~mAM, l~c. -13- Authority constructs are 150 feet, which means that they must be located at 35 feet above sea level. The 35-foot contour in the western part of the Town of Southold, shown on plate 1, is approximately coincident with a water-table elevation of 4 to 5 feet above sea level on the southerly side of the fresh-water mound. At this elevation, the prospective well sites are sufficiently removed from salt-water bodies to minimize lateral salt-water intrusion potential. All of the six well-field sites in western Southold could accommodate a tank at elevation 35 feet above sea level onsite or in near proximity. A detailed review of storage needs is beyond the scope of this study but is a potentially important factor in an area with high seasonal weekend usage. F h-W r M und The LBG report of March 1985 outlined the normal and extreme drought year (1966) water-table mound centered on Cutchogue Station, between Mattituck Creek and Richmond Creek. A number of prospective production well-field locations have been considered essentially between the normal +4- and +5-four water-table elevation contours. These general locations have been chosen because they ~ downgradient of the ground-water divide, sufficiently distant from tidal water, have a relatively thick fresh-water lens, a~e sufficientiy separated to avoid undue mutual drawdown interference, are reasonably close to population centers and Main Road (Route 25) and, in a preliminary way, a~e in re-'oas where property may be readily available to the Water Authority. Previous studies by LBG show that at water-table elevations of 4 feet above sea level, well yields as high as 700 gpm can be a~hi~ved without inducing upeoning of salt water (LBG, 198fi). Thes~ calculations were completed without cunsiderafion of the areally-cxtensive interstadial clay layer, which would be even more protective of high- yield wells. Based on the above factors, six well-field locations have been selected, as shown on plate 1. The anticipated long-term yields of the well fields, also shown on plate 1, are based on a recharge rate of 0.5 mgd/m~, and the indicated circles around each well site symbolically represent the equivalent recharge area. The actual zone of capture for II ! ! -14- each well field would have a parabolic shape centered on the wells and widening up to and, in some cases, beyond the present ground-water divide. As any site is tes~l and developed, site-specific zone-of-capture modeling should be used to define the actual zone of recharge capture. The total selected well*field network would have a combined sustained capacity of 3.2 mgd, sufficient yield to supply a population of about 30,000 people. This is well in excess of the population projections for the entire Town of Southold to the year 2020. It is important to recognize that short-duration .~msonal pumpage substantially greater than the year-round rated capacities may be accommodated. The presence of upper interstadial clay in western Southold implies that seasonal upconing of saline water will be less of a limiting factor than on the South Fork. Sources of Known or Potential Contamination The most recent inventory of land disturbances that may involve potential hazardous waste/storage facilities is the Cornell University CLEARS study for the SCDOHS, in which a county-wide inventory of potential waste-disposal sit~ was made by detailed analysis of aerial photographs for 1962, 1978 and 1984. Such features as dumps, landfills, pits, lagoons, barrels or drums, mined area~, disturbed land and above- ground tanks were identified, and changes associated with these sites over the photo histo~-y were described. Where I~F, inent, CLEARS information for file vicinity of pwposed well-field sites is discussed below in the section on each proposed well-field location, and the mapped sites are shown on plate 1. Competition With Irri~ation As can be seen in table 7-4 from the NFWSP (page 11 of this report), agricultural irrigation is the largest consumer of water on the North Fork. E~timates of the past irrigation pumpage have been given in previoua report~, vary considerably from wet to dry year, and are considered unreliable by local agricultural experts. L£GG~ a~., BIO,~IF. AI~ & GRnItAM, I~C. -15- A windshield survey of thc North Fork was conducted in/one 1992 for a first- hand understanding of the active farming and irrigation activities, eg~ecially in relation. to prospective public water supply well sites. In the Town of Southold, there appears to be considerable agricultural diversity, with the historic dominant potato acreage giving way to sod and wine grapes, and a large acreage still in vegetables and berries. Table 7-3 from the NFWSP, reproduced below, gives estimate~ of crop acreage and annual water consumption in 1980 ba~d on estimates by the Suffolk County Cooperative Extension Service. IRRIGATION REQUIREMENTS FOR CROPS GROWN ON THE NORTH FORKv (From Table %3, NFMSP) Crop type Acreage Irrigation requiremenL~- (g:dlons per acre per year) Potatoes 12,000 125,000 Mixed vegetables 4,000~ 205,000 Cabbage and Cauliflower 3,500 205,000 Rye 2,000 -- Nurser3, stock 2,000 165,000 Pastures 1,000 20,000 Sod 1,000 245,000 Sweet corn 800 125,000 Fruit trees 6(~0 125,000 Grapes 350 40,000 Greenhouses 25 815,000 TOTAL 27,275· 140,000 (weighted average) l./ Communication with D. Fricke et al. from Suffolk County Cooperative Extension Service. 2-/ Peppers, spinach, beans. ~/ All figures rounded. 4_/ Acreage was estimated. l By contrast, a 1991 estimate for all of Long Island for 1991 from the Farm Bureau shows only 7,500 acres in potatoes, 2,450 acres in cabbages and cauliflower, but with substantial increases in nursery stock, sod and grapes. Irrigation practices vary widely by crop and individual preferences, but mainly involve moveable sprinklers, with some trickle-irrigation in nursery stock areas. The 'rule of thumb' is that most crops n__~d_ an inch of natural or irrigation water per week during their growth cycle. In a typical year, sod requires about double the water that potatoes need because of the growth cycle, whereas wine grapes are rarely irrigated except in the initial season of planting until the deep roots are set. A representative of the Soil Conservation Service offered his opinion that most crops in the Town of Southold are under-irrigated because of the lack of sufficient equipment and labor, and that the grape crop could be improved by periodic irrigation. In June 1992, a fairly sizeable acreage was in hay or lying fallow, with some areas showing 'old field progression' to woody plants. Numerous 'for sale" signs were evident on inactive and on some active farms. As housing displaces farms, the consumptive use of ground water will decrease. Whether homes are supplied by individual wells or by public water supply, the major part of domestic water use will be returned to the ground by septic systems. Most of the previous reports on the North Fork forecast a long-term reduction in commercial agricultural activity in the future, following patterns from the west. If reaiizea, this will result in less consumptive use of ground water. A working paper by the 1991 US/UK Countryside Stewardship Exchange Project found that there were 470 parcels of land of 10 acres or larger in the Town of Southold, comprising 13,500 acres. Active commercial farms, 84 in number, involved ownership of only 3,670 acres. Retired farms comprised 2,533 acres. Substantial acreage, much in sod, was leased land, not included in the active farm list. A total of 1,100 acres of farmland in the Town have reportedly had their development rights sold. LEGG~.~ ~, BRAS~a~S & GmmAM, i~C. -17- PROPOSED WI~LL-FII~.LI~ LOCATIONS Site A Site A is a farm site in an area presently used for cabbages and potatoes and with wine grapes, more potatoes and a small horse farm in the immediate area. For the present, there would be moderate competition for the available water for irrigation purposes, and only minor potential for interference with domestic supply wells. The preliminary yield potential of this site is estimated as 0.5 mgd. Site B Site B is in unoccupied woodlands directly to the east of the Laurel Lake tract. Nearby farmland is lying fallow; there is some active potato fanning to the west and southwest. Competition with irrigation is deemed minor. There is minor potential for interference with domestic supply and commercial wells within the Laurel Lake community, the Camp Malloy area and along Main Road (Route 25). The preliminary yield potential is estimated as 0.9 mgd. An issue that will need to be addressed during testing will be potential impacts on fresh-water wetlands about 1,000 feet to the north of the site. There is an abandoned sand and gravel pit to the east of Laurel Lake near the prospective well site. It has a hummocky appearance that looks like sand and gravel was dumped in, perhaps to cover something, rather than a typical mined-out appearance. No diz~ct evidence of dumping was observed. This site should be checked out by test borings and a monitoring well during testing for a production well siM. The CLEARS study makes note of this site and another gravel mining site south of Main Road near Bray Avenue. In addition, an industrial site between Main Road and railroad tracks has a history of above-ground storage tanks, scattered waste and soil mounds. One or more monitoring wells would be warranted in this direction. Site C Site C is in farmland presently in use for vegetables and near some fallow land. Potatoes are grown to the west, wine gropes to the south, and more fallow land lies to / I I I I I I I I I I I I I I i I I t -18- the east. At present, there is moderate seasonal competition for the local ground water for irrigation, and some potential for interference with domestic supply wells along Main Road (Route 25). The preliminary yield potential is estimated as 0.5 mgd. Site D Site D is presently a Christmas tree farm. Wine grapes and beans are being grown to the west and northwest. The Town of Southold landfill is located 1.2 miles to the north-northwest, on the northerly side of the ground-water divide. Competition with seasonal irrigation water use appears light, but some potential for interference with domestic supply wells along Main Road (Route 25) and nearby side streets. The preliminary yield potential is estimated as 0.5 mgd. Site E Site E is mainly in a wine-grope area, mostly associated with a single vintner. Competition with seasonal irrigation is presently light and the potential for interference with domestic wells is slight. The preliminary yield potential is estimated as 0.5 mgd. Site F Site F is in a primarily residential and wooded area. Directly to the northwest is a recharge basin/pond which has wetlands characteristics, and directly across Middle Road is a gasoline station. The site is too small to accommodate a storage tank but land 1,000 to 2,000 feet to the northeast on the north side of Middle Road, near the power line right-of-way, may be suitable. There is little to no competition with irrigation supplies, but some potential for interference with domestic supply wells. A 1989 test well at this site showed excellent water quality, and pore-water samples from the inte~stadial clay showed fresh water to more than 100 feet below the production zone. The preliminary yield potential is estimated as 0.25 to 0.30 mgd. A public water-supply permit has been issued for two wells at this site with an authorized withdrawal rate of 288,000 gpd (gallons per day). LEGG~..~ ~,':., BRASHF_.ARS &: GV.~AM, I~c. Once suitable properties are located for well installation, a testing program would be initiated. At each site, a test well would be installed and a controlled pumping test run to determine the zone of contribution. The tests would utilize existing or newly- installed monitor wells to determine water-level drawdowns at specific distances from the well fields. The final recommended well yields would be based on the aquifer testing. The initial development is planned for the Laurel Lake area. It is anticipated that this Well field will be capable of supplying water to the communities west of Mattituck Creek along Peconic Bay, as well as most of Mattituck. In addition, the present investigation has included consideration of prospective well sites both east and west of Mattituck Creek and in Orient. No consideration has been given to the Village of Greenport which operates its own public supply system supported by wells. Orient Area Plate I also shows the much smaller and lower ground-water mound in Orient, with the location of a prospective well-field site. Based on Table 7-4 of the NFWSP (page 11 of this repori), thc Permissive Sustained Yield of this area is already over- subscribed, mainly by agricultural pumpage. Considering that both the agricultural and residential consumption peak during the same months, and the small volume of local fresh ground-water storage, it appears likely that increases in pumpage would likely lead to salt-water encroachment, especially in drought years. A local source of public water supply by shallow wells might be feasible if a significant volume of agricultural pumpagc is retired. A rectangular manmadc pond about a half mile to the east at the headwaters to the wetlands was identified by the CLEARS study. The 1978 and 1984 photos showed the pond being filled in with material including miscellaneous waste. Thc estimated yield potential of this site is about 0.15 mgd. I I I I I I ! I I [ GROUND-WATER QUALITY Ground-water quality in the Town of Southold has been widely degraded by leaching agricultural chemicals. Heavy fertilizer usc has caused elevated nitrate levels, commonly exceeding the drinking water standard of 10 rog/1 (milligrams per liter) of nitrate-nitrogen. Concentrations of residues of aldicarb and other pesticides and fungicides also commonly exceed drinking water limits. Naturally-occurring dissolved iron and, to a lesser extent, manganese are also commonly esthetic nuisances for private well owners. Where present above the Secondary Maximum Contaminant Levels in public water-supply wells, treatment for removal would be required and would be a benefit to customers. Well-site selection can minimize the concentrations of agricultural chemicals. Initial sampling results from the Mill Lane test well in Peconic indicated excellent water quality, but sustained high-yield pumpage at any site will tend to draw in water from laterally-remote areas, and to draw water from the upper part of the water table where surficial chemical impacts tend to be concentrated. Any well in the Southold area should be expected eventually to show impacts of agricultural chemicals, although not necessarily in excess of drinking water standards. It would be prudent to plan on water treatment for nitrate and pesticide/herbicide/fungicide removal and for iron and/or manganea~ remova~ at each well fic~.. CONCLUSIONS AND RECOMMENDATIONS 1. There is sufficient flesh ground water in the Town of Southold to support the expected future population growth into the early part of the next century. LEGGt. i ,~ BRAsnva, as & GRAHAM, I~C. -21- 2. The expec~l future reduction in commercial agricultural activity will reduce the consumptive use of ground water, resulting in a more favorable hydrogeologic budget. Ground water used for domestic water supply is largely returned to the ground by septic systems. 3. Ground-water quality in the Town of Southold has been impaired by residues of agricultural chemicals. Although any well site may initially show satisfactory water quality, some water-quality degradation over time should be expected. Treatment for nitrate and/or pestieidedhe~bicidedfungicide residue removal and for iron and/or manganese removal should be planned for any public water well field in the Town. Over the very long term, reduced agricultural activity should result in some ground-water quality improvement. 4. Six well-field sites have been identified in the western part of the Town, from the Riverhead border to the hamlet of Peconic. These sites have individual projected yield potentials of 200 to 625 gpm, and an aggregate estimated yield of 3.2 mgd. Tank locations that would meet the Authority's elevation criterion are available at or near each well site. The well-field and umk sites have been situated so as to be reasonably close to population centers that may want public water-supply service. The ultimate distribution system would likely fie into the Greenpon Water District, providing additional back-up capacity for that system. 5. The ground-water resources in the Orient area appear to be fully subscribed by domestic and agricultural usage. If agricultural acreage is retired, a small local well field may be feasible. L£G.a, ~. B~rr_~as & GannA~ Inc. I I I I It I I I I I I I I I I I I I -22o 6. As with any Water Authority exploration program, a full-scale testing program should be conducted at any proposed well-field site to ascemin the hydraulic characteristics of the subsurface material, the depth of the salt-water interface, the stratigraphy, the water quality and any potential impacts of water-supply development. skd July 28, 1992 southold, rpt]92-34 LEGGETrE, BRASHEARS & GRAHAM, INC. Robert Lamonica, CPG Vice President I I I I I I I I I I I Pa,,e SUMMARY ......................................... 1 INTRODUCTION ....................................... 2 POPULATION AND WATER USE ............................ 2 WATER-SUPPLY AVAILABILITY ........................... 4 Hoffman - Bulletin GW-45 5 Crandall USGS WSP-1619-GG 8 Comprehensive Public Water Supply Study (CPWS-24) ........... 9 North Fork Water Supply Plan - SCDHS .................... 10 LBG Reports ..................................... 11 WELL-FIELD SITE SELECTION CRITERIA ..................... 12 Population Centers .................................. 12 Storage Tanks ..................................... 12 Fresh-Water Mound ................................. 13 Sources of Known or Potential Contamination ................. 14 Competition With Irrigation ............................ 14 PROPOSED WELL-FIELD LOCATIONS ........................ 17 Site A ......................................... 17 Site B ......................................... 17 Site C ......................................... 17 Site D ......................................... 18 Site E ......................................... 18 Site F ......................................... 18 Site-Specific Testing ................................. 19 Orient Area ...................................... 19 LEGGr~ ar.., Bv~ar~v.s &Gm, Ha.~, L'qc. TABLE OF CONTENTS (CONTINUED) GROUND WATI~R QUALITY 20 CONCLUSIONS AND RECOMMENDATIONS .................... 20 REFERENCES APPENDIX PLATE FIGURE 4-1 FROM THE NFWSP pI~I:.I.IMINARY WATER-SUPPLY PLAN I I I I I I I I I I I I I I I I -23- REFERENCES Baler, J. H. and Dennis Moran, 1981, 'Stares Report on Aldicarb Contamination of Groundwater as of September 1981", Suffolk County Department of Health Services. Baler, J. H. and S. F. Robbins, 1982, "Report on the Occurrence and Movement of Agricultural Chemicals in Groundwater - North Fork of Suffolk County', Suffolk County Department of Health Services. Bohn-Buxton, Debra E., Herbert T. Buxton and Valerie-ann K. Eagen, in press, 'Ground-Water Flow Patterns and Travelfimes on North Fork, Long Island, New York, in Relation to Aldicarb Contamination", United State~ Geological Survey. Crandall, H. C., 1963, 'Geology and Ground-Water Resources of the Town of Southold, Suffolk County, New York", United States Geological Survey, Water Supply Paper 1619-GG. ERM-Northeast Engineers, P.C. and Camp, Dresser & McGee, 1983, "North Fork Water Supply Plan, Suffolk County, New York", prepared for Suffolk County Department of Health Services. Hoffman, John F., I961, ~Hydroiogy of the Shailow Ground-:~Vater Rcsctwoir Town of Southold, Suffolk County, Long Island, New York', United States Geological Survey, Bulletin GW42. HoLzmacher, McLendon & Murrell, 1970, "ComprehensiVe Public Water Supply Study, Suffolk County, New York, CPWS-24. Iensen, H. M. and Julian Soren, 1974, ~Hydrogeology of Suffolk County, New York', United States Geological Survey, Hydrologic Investigations Arias HA-501. Leggette, Brashears & Graham, Inc., 1985, 'Factors Affecting Water-Supply Development in the Southold Area, Long Island, New York', prepared for Suffolk County Water Authority. LEGGt..s l~, Bm,sm & GRAHAM, INC. -24- Leggette, Brashears & Graham, Inc., 1989, 'Hydrogeologic Evaluation of the Richmond Creek Subdivision Property, Mill Lane, Peconic, New York', prepared for Suffolk County Water Authority. Leggette, Bra.shears & Graham, Inc., 1991, 'Hydrogeologic Evaluation of the Property at Oregon Road, Oregon Hills, Town of Southold, New York', prepared for Suffolk County Water Authority. Leggette, Brashears & Graham, Inc., 1992, 'Potential Land Acquisition, Laurel, New York', prepared for Suffolk County Water Authority. Luscynski, N. J. and J. F. Hoffman, 1951, 'The Water Table as of April 1950 in Southold Township, Suffolk County, Long Island, New York', United States Geological Survey, Open-File Report. McClymonds, N. E. and O. L. Franke, 1972, 'Water-Transmitting Properties of Aquifers on Long Island, New York", United States Geological Survey, Professional Paper 627-E. Soren, Julian and W. G. Stelz, 1984, "Aldicarb-Pesticide Contamination of Ground Water in Eastern Suffolk County, New York', United States Geological Survey, Water Resources Investigations Report. Suffolk County Water Authority, 1990, "Southold Watershed Management Plan: Evaluation of Proposed Alvah's Lane Wellsite, Hamlet of Cutchogue~. APPENDIX FIGURE 4-1 FROM THE NFWSP I I I1 I1 I1 II II Ii I1 II ZONE I i ZONE ?- _ , ZlNE ;5 ZONE 4. SOUTHOLD LINE ~b~q~.O BOUNDARY HAS; WATER TABLE ; ;I TABLE F 0 LEV SEA CLA~ AND CLAY ; ~ ~LA~ ) 2?5- 300. 325- 350. 375' 400' 425 FRESH WATER TO BEDROCK ZONE 5 DAM ~NAL TEST WELL GLACIAL Figure 4-1 Geologic Cross - Section 9! 4 .... APPR~)XIMATE AREA OF CAPTURE ' APPROXIMATE 5 FOOt: WATER TABLE CONTOUR -~PPROXIMATE 0 2000 SCALE IN FEET SUF MD D T X XL G P LEGEND_ PROPOSED WELl- LOCATION MINED AREA MINED AREA-DUMP DUMP ABOVEGROUND TANK DISTURBED LM~D DISTURBED LAND-LANDFILL LAGOONS POLK COUNTY TOWN OF ~NATER AUTHORITY SOUTHOLD PRELIMINARY WATER SUPPLY PLAN DATE -- REVISED PREPARED BY: -- t LEGGETTE, BRASHEARS & ~RAHt2vl, INC. --t -- I Professional Ground-}Ta~er Consultants ~ ~ 72 Danbury Road -~ I '~ ~ilton, CT 06897 49 APPROXIMATE ~V.~LL FIELD ]Jame~port 0 FEET 5 APPROXIMATE AREA OF CAPTURE 9 5 3 · APPROXIMA'J~E 5 FOOT WATEF~ ,.TABLE Col~rI'OUR " t3 Jc LEGEND PROPOSED WELL LOCATION .\ Neck Bay L Har, bor CUTCHOG[fE HARBOR 0 2000 SCALE IN FEET t3 / SOUTH DRAWN: CHECKED: M.R.V. , 22 /5 SUFFOLK COUNTY TOWN OF PRELIMINARY DATE REVISED WATER AUTHORITY SOUTHOLD WATER SUPPLY PLAN BY.' LEGGETTE, BRASHEARS & GRAHAM, INC. Professional Ground-Fater Consulfants 72 Danbury Road Wilton, CT 06897 (203) 762-1207 PLATE: 1 OF I % THIS IS A RECORD DRAWING: OF WORK AS CONSTRUCTED: ,, SU FOZ ' c001,77'Y' REVISIONS DESCRIPTION DATE DESCRIPTION · APPROVED: WALTER, C, HAZLITT, ~EXECUTIVE DIRECTOR, pROF, ENGINEER LIC, NO. O~ ;7585 $,UFFOLK COUNT'Y WATI~:I{ AUTI1ORITY D..p~,.TM~:,,r.r...,,,...... E~NEE~NG, SUNRISE HIGHWAY AT POND RO~ ' , OA~A~ L.I., N Y ' THE EDUCATION LAW AN DRAWINGS ANDIO~ UNLES~ PROFESSIONAL ENGtNIEEI NOTE AND/OR IN 3HE SPECIFICATIOi~IS.