Loading...
HomeMy WebLinkAboutSDP200500014 Assessment - Groundwater 2005-02-28 Grace Community Church Tier 3 Groundwater Assessment Groundwater Management Plan Prepared for: Win Wood Grace Community Church 1762 Timberwood Bvd. Suite 125 Charlottesville VA 22902 April 2, 2005 Nick H. Evans PhD CPG Virginia Groundwater LLC 4609 Burnley Station Road Barboursville, VA 22923 T EN APR 4 2035 CG.! UNITY DEVELOPMENT Key Findings Hydrogeologic unit: Piedmont Foothills (III) Groundwater availability zone: Class 2 (moderate groundwater availability) Hydrogeologic conditions favorable to proposed use? yes Site within groundwater sensitivity zone? no Groundwater flow pattern: recharge on southeast flank of Piney Mountain; groundwater flow southeast; discharge at spring in southeastern corner of property, in Herring Creek and the North Fork Rivanna River Contamination threats on record: no open UST cases inside one mile buffer; no open cases of toxic release Additional contaminant threats observed in field reconnaissance? no Impacts of proposed use on existing users: groundwater availability on site should be adequate for proposed use without affecting existing users off site BMP recommendations: maintain undisturbed forest cover as much as possible during development; implement runoff - neutral site plans insofar as practicable. Site Overview The Grace Community Church parcel (TM 21 -11) is located on the southeast flank of Piney Mountain, west of US 29 in northern Albemarle (Figure 1). There is about 300 feet of topographic relief on the parcel; elevations range from about 535 feet in the southeastern corner to about 835 feet at the northern corner on Piney Mountain. ' The site is presently in mixed pine and T. hardwoods that are 15 to 20 years old - The land is incised by erosional gullies, now wooded, that formed during previous clear cutting. Groundwater is presently discharging into a spring near the southeastern corner of the parcel. Hydrogeologic Assessment Bedrock geology The parcel straddles a mapped bedrock contact between ProterozoicY -age porphyroblastic biotite - plagioclase augen gneiss to the northwest, and ProterozoicZ -age White Oak alkali feldar granite to the southeast (Figure 2; Geologic Map of Virginia, 1993). The parcel is within the Piedmont Foothills (III) hydrogeologic unit, with Class 2 (medium) relative groundwater availability, as defined in the Albemarle County Hydrogeologic Assessment Summary Report of 2003. The contact between the two mapped bedrock units on the parcel is intrusive, dating from when the granite was emplaced into the gneiss about 700 million years ago. Both the granite and the gneiss were subsequently recrystallized during regional metamorphism, and it is not likely that this discrete contact has significance today in terms of groundwater flow on this parcel. The parcel contains bedrock outcroppings of alkali feldspar granite in the northernmost corner. Bedrock is not exposed at lower elevations, where rock is covered by a mantel of weathered colluvial material and saprolite. Boulders of diabase occur at the edge of the parcel along Rt 606, implying that a diabase dike is present up- slope. —�� , L / ` � J r - \ 4 \ , 3'\ C ' \ �� � y v;' J T -� N � \ c V im\ f ftor T' L . � a e . ( s f /�� s �• / '' • �` � i p . /'�' 'a> A 1 1 a) S / I 'L'') v ,-1 /� - /�J/ / \ \ - �� 7 ` • ,, �1 -, / 4----- ... ,w . l :e.-Lf 1 1 Avg �. / `\ \ --�T� _ . 0 ‘'.-'---'•- . - �1 r �rp T' J- ( 1 �i .l - -1; /�'✓. , ✓ • t ' �, 0 I • r ^ ` �� r >7, ( � - -,,,, 'rl )It'''‘ X41- �� ! � ) > \ /�� 0 0 CA D ,,, ,7) 1) � � :. j ltl' 1 ( � \ `"i , , \am ; ; - ,' �, \( �'",/ ; / �� - u ry , „/„-‘\),---/-44.------- \ - - � . - k -�= � � � !(� � `, ; < , ,5 ,s - ,r \( \ 1i �'= I '.: O , ,,,,... .. i ...., - \ , .. ..:„.-.-.„,,!■, ,f /"... :2 , - - _L„,.,...._,,,, , ,---,-,-; ,- -7- -;` ,- \,_-_,..---, ''' \,. r" \ .('-`,,,, \ •' --.\;, ,,... r _.\_)\,,,, Y \=�� �" � \lam Vi - E � ` �'1� • , •.. y ' �'f � r � i /n \11' ` \ - �'` /` � i ' \ _� \ . \ \\� ti `'` rr \\ '--'-- • 1 � - ( O. � � f `J `\ " - '\\ YE' a i � i I " ( ' ' i / I \ '� d �� ^ .), �, \,_,? M, , /' 4 , � S J Lim^ / __-! l... - -N _�\�f�rJ� (� t ^J y e � , 0 -'a %v im ( � y ,< v � k \� �(_; C� /} z d- v�LJ .4, Z t` -7(c w /,1 r '* ter` -, pin f . A / � r v � �,, . ,- ^ � j / �_ � t W > t \ ,�. \ ( ✓- ' ^. -- - \, C , � � • � ,� ,��, -- � �- � ' R _ A------,---' f > > : � � i �/ gar --:___<.-= � I t, - .�� S r r �-, Al. fi D mss, r \ 3 ( D t , Gam .' . �' � / - ' � , ' �Z` 1 1 � � \ ��� lt✓ � �l V � ` � c y R , , ` /a' ( C , . ^JI � 1 ` 3 's � 'J � _ i �l/�' ,' . c is \\ ___/ �- � f l:v� r' r-, 1 �wJ/ jam ( ; lA \ v + s l � r �' i (.. O) � , • � �f`i_.) �.. „t L” /, ,,,7 )fin\ �.1 /_..._ /. 1 <.�,. -< Nco O moo m* 3 0 r co , � Q o - m - o c-, = ' �- - m c Q 13 3 n. *S ( _' . a cQ c= n cn v 'u v (D 0 c - 7- 7 N m ED o - ED m 411 co g - A * --- t % , ,,,_ _-..- ;_s . . . . - - -..„, -- ce - r l � -_ /� �` t.' � ` �. • _ � CD Q / � �__ / \ i --" `. / , CD ��� '�� -; L " 7� t ' ( y • r `� ate. 1,1,4*‘...„,,s4; Z: t 4 O CD- I 1 ! ` in. S ,. s ),./„),., , gi „."-„,...,, ---,-,,, -„,,____ • ° P c:25>-2.:A___fl-----.14 ` o V,-,,j),-\7:1Liz,fs--„, � �+ ti � D , " - i .._.---'---__>_"-_,- '--=--------"). \ i n-N r-----r ,,, \ 47 ., 11------%- 3:v4, g rcol< ( --__ . 7 -- ___ -rf w ,/ ) \\----- ---_----`- ---------->- — . - . .. -; D -----" ''-------** , , _ _ cr - - - - - - - ---- ' t' • . 4 . , , , 27, . 7 ‘\" opm - 6 - --,--:,_<___.----, c .„--_..-_-----./..„...,_„.,, f , , ;\ -12 , , )\1 (---- ' 1 11/ t 6\ i i , al .., • "--,. . , / , -•••__, ----, , , ( -6<,--, j ' � i°' c y � . ,, :� t 4 V/ -� -, — Bedrock fracture density and water well productivity Neither the granite nor the gneiss contain primary intergranular porosity through which groundwater might pass. Groundwater flow is confined to bedrock fractures and fissures. No significant linear features, fracture traces or structural features were identified on air photos or other maps in this study that would be useful indicators of bedrock fracture orientation on this parcel. In the absence of good bedrock exposures with which to directly observe bedrock fractures, the yields of randomly -sited water wells can be used as a proxy for fracture density. The average yields of wells in the two bedrock formations on the site are virtually the same, although wells drilled in the granite are somewhat shallower, and have shorter casings. For 1536 wells in the database drilled in the biotite gneiss, average yield is 8.4 gallons per minute, average total depth is 218 feet, and average casing length is 49 feet. For 89 wells in the database drilled in alkali feldspar granite, average yield is 8.2 gallons per minute, average depth is 190 feet and average casing length is 39 feet. Overall, the data indicate that these bedrock types are favorable for groundwater development in terms of fracture density. However, the success of a water well still depends on whether or not the well intersects water - bearing fractures, and dry holes result if no fractures are encountered at the drilling site chosen. Soils and saprolite Soils on the parcel are in part derived from transported colluvial material, and in part residual, derived by weathering of biotite gneiss bedrock. Louisburg soils (Figure 3) on the upper part of Piney Mountain are thin, rocky, and rapidly permeable. These pass down -slope into Wedowee and Pacolet sandy loams. These soils are deep and moderately permeable. The soil profiles on this parcel can be favorable to groundwater recharge to the extent that forest cover remains undisturbed. Because of the slope and moderately permeable subsoils, surface runoff is rapid, and the hazard of erosion is severe. Groundwater flow, recharge and discharge Groundwater flow across the parcel is estimated to be in a southeasterly direction (Figure 2), driven by the strong topographic gradient on the southeastern flank of Piney Mountain. Primary recharge is on the upper slopes of Piney Mountain. Groundwater discharges in a spring in the southeastern corner of the parcel. Deeper level groundwater recharging on Piney Mountain discharges into Herring Branch, and, ultimately into the North Fork Rivanna River. co -N N l/) .p. - ET 01 v- v- 01 e j 01 CX) ED 3�? 2 30° N od ��m n cn '< CD CD r V V N o o O ^ 0 0 �! Q U) a) C U) 7 O ` , 01 O 01 O- 0 o 0 3 C O D W 0 o � N* -CS _ a - E 3 o SQ ° = w 3 < C N (D N O Q Q � G 5 0 0 -3 CO C') CD n' 0 _ _ U3 A CAI . O C 04 - > ---4 t .... __ z p 0 Lo , .c _ 0 ___________---- . , ___ ,„,,, ,pi 6„ .... .4.4„ ...-- ..„14F. .4, -,• z$3,-/ .1%%"'":9v<9— ,,,„(6 ,--- 0 ,, ,..-- i„.,, Groundwater sensitivity and contaminant threats The Grace Community Church parcel is not within an area of recognized groundwater sensitivity according to a County study or databases that were assembled during the 2003 Albemarle County Hydrogeologic Assessment, Phase 11 (Figure 4). Toxic releases on record As of March 28, 2005, the US Environmental Protection Agency Toxic Release Inventory contained no entries that are within one mile of the site and none beyond one mile that are considered a threat to groundwater recharge. The Virginia DEQ toxic release database does not show open cases that are within the one mile buffer zone surrounding the parcel, or beyond the one mile buffer, in areas considered a threat to groundwater recharge affecting the site. Underground storage tanks The County underground storage tank database shows three tanks within the one -mile buffer. These are all listed as closed cases in the database. The tanks are an property owned by GE Fanuc, down gradient from the Grace Community Church parcel. The current Virginia DEQ registry of underground storage tanks does not show registered tanks that are within the one mile buffer zone surrounding the Grace Community Church parcel, or beyond the one mile buffer, in areas considered a threat to groundwater recharge affecting the parcel (Table 1). There is a service station and convenience store on the southbound side of US 29 within 700 feet of the parcel (Figure 4). The status of storage tank(s) at this facility is unknown. However, the facility is located down - gradient from the Grace Community Church parcel, and it is unlikely that a spill at the service station would affect groundwater resources on the church parcel. (0 efi- - , _ ..._ 0 CD_ CD --, } CD O Q., C 1 _ , $ 0 Q , a) W n /11%. , ovit41001 w CT m A O N m N • m ► o a : N 1 re- c)= a 0 = I; ■ ' �. l. 3 en L © 1 � . Os ''^^ 7 � t O N -' 0 • fA N (D .--.- t� - ` tii P Y ^4 i r-► • A" n 0 Table 1: Registered underground storage tanks in the Virginia DEQ database, zip code 22911, as of March 28, 2005 Fac Id Name Address 1 Zip 5 Fac Type PANTOPS AMOCO CONVENIENCE 6026141 CENTER 241 Rolkin Ct 22911 GAS STATION 6013298 GENERAL ELECTRIC FANUC Routes 29 & 606 22911 INDUSTRIAL 6006805 Forest Hill Associates Inc 2320a Hunters Way 22911 CONTRACTOR 6014980 BADGER FIRE PROTECTION 4251 Seminole Trail 22911 INDUSTRIAL 6003286 ACSA Fuel Storage Facility 168 Spotnap Rd 22911 LOCAL 6023993 Charlottesville - Albemarle Airport 100 Bowen Loop Road 22911 LOCAL S.L. Williamson Company Inc Shadwell 6036048 Plant 1240 River Road 22911 CONTRACTOR 6037239 FABRICS UNLIMITED 3912 Seminole Trail 22911 GAS STATION 6039403 Baker - Butler Elementary 2740 Proffit Rd 22911 LOCAL 6038521 Pantops Liberty 240 Rolkin Rd 22911 GAS STATION 6039181 Avis Rent A Car System Inc 1581 Airport Rd 22911 COMMERCIAL 6039300 Charlottesville - Albemarle Airport Car Rental 3843 Dickerson Rd 22911 LOCAL Potential for transportation- related accidents and spills The church parcel is located within 600 feet of a major highway, US 29. However, the road is down - gradient from the parcel, and it is unlikely that a contaminant release resulting from an accident would affect groundwater resources on site. Residential drainfields There are several drainfields on adjoining properties in the vicinity of the parcel (Figure 5). Only two of these are potentially up- gradient from the parcel, on the northeast side. These are around 300 feet from the property line; the possibility of contaminants reaching the Grace Church parcel from these drainfields is considered remote. Potential for proposed use to affect existing users of groundwater The proposed use of groundwater is not predicted to interfere with existing users on adjoining parcels or elsewhere. Groundwater availability is estimated to be more than adequate to supply the needs of the church without affecting neighboring wells. Reserve wellfield The church parcel is large enough that multiple options exist for the siting of wells, should it become necessary to drill more than one well. y1; r V 474 ° dYyy ' le �r .w - # .4.1. � ,-- i.. . "" 4 i r *r ` " �1r i , . ''''''96 � r .0* n . ,� CD 01 - - (D r. CD �. x (D 0 0 _ - —f, 0 � CO ,,..+✓..-. CD ,.p.. y , n . 'a ., .. .. Wry xkx ors �.�+# ♦ - a' µ 0 ,y am'"'"' 3 • �+ . 4110 ' • t � = �« i ' 1 NP + siF. ,w 3 0 N� r+� g ' / 0 ., '' , ■ r , i ER t * ® ' 4 * ii , Dedicated Monitoring well This parcel is not in an area of intensive groundwater development at the present time, and the proposed use is not predicted to stress groundwater resources off site. It would seem this is not a priority site for a County dedicated monitoring well. Best Management Practices: recommendations Steep slopes on this parcel and moderate subsoil permeabilities make it imperative that existing forest cover be left undisturbed wherever possible. This is particularly important on the upper portions of the parcel. The site plan places the church and parking lot in the lower one -third of the parcel. The interests of resource protection would best be served if the Church were to commit to leaving the up -slope portions undisturbed, and consider placing that acreage under conservation easement. Site plans incorporate an arcuate bioretention swale that receives all runoff from the developed site. This structure will greatly enhance the possibility of runoff - neutral development, which is good for groundwater recharge. s '�d r tj 11 q 0. a LI 1 _ _ _ 11 II 1. r ill IS i 1 1 15 e sg r • , , ,, \ :f ) '' , i 9 '. ;-.,-. \' \ • i q ---\.. 1 1 I t "--.; 1 \'' A y € of . • 1, a , ' I Y I. s 4 1 ; l i' \ .1 7.1 ; :,,,,>, --, r)—(f_ , • i 1 . 7 4 9 i i o , ). ...s. ..., . ... , Pi ilitt i i. I #1 -*L . , 4 . . ------ _, ,i ii . _ __ i e ' A ( iS 1 -*/ E; CIC --- 6/6 ... ii VIP _ ; — — — -� _ saa•sasorom ma.... In 07'i ) is II PLAN r H ;+ ' , z �, pRE].MVARS SITE DE�t1)YYENTP11= FOR � �� �r s i z a GR COMMUNITY CHURCH VA :t.1 t/I i - } – ZFr1 1 11161:141 S6 $' L�/v iijil i �c 1 i'1 ! ; _ G RADING AND UTIL1TII PLAN i - a C a.