Air-Quality Evaluation of Stacks: Building No. 3 Chiron Corporation, Emeryville: A Wind-Tunnel Study Table of Contents EXECUTIVE SUMMARY 1

Transcription

1 Ar-Qualty Evaluaton of Stacks: Buldng No. 3 Chron Corporaton, Emeryvlle: A Wnd-Tunnel Study Table of Contents EXECUTIVE SUMMARY 1 1. BACKGROUND 3 2. INTRODUCTION 4 Project Locaton 4 Campus-Project Descrpton 4 Study Objectve 8 3. ANALYSIS OF NEAR-FIELD AIR TOXICS 8 4. CRITICAL WIND SPEED 1 5. ATMOSPHERIC STABILITY METEOROLOGICAL DATA/WIND CLIMATE DILUTION CRITERIA 13 Exhaust Stack Dluton Crtera 13 Desel Exhaust Dluton Crtera STACK PARAMETERS WIND-TUNNEL TESTING WIND-TUNNEL TEST RESULTS 18 Buldng Nos. 3 and 4 Receptor Tests 21 Indvdual and Cumulatve Stack-Receptor Measurements 22 Emergency Desel Generator-Receptor Measurements WIND-TUNNEL TEST CONCLUSIONS 24

2 Ar-Qualty Evaluaton of Stacks: Buldng No. 3 Chron Corporaton, Emeryvlle: A Wnd-Tunnel Study Table of Contents 12. ACKNOWLEDGMENTS REFERENCES AND BIBLIOGRAPHY 25 APPENDIX A: THE ATMOSPHERIC BOUNDARY LAYER WIND TUNNEL AT UNIVERSITY OF CALIFORNIA, DAVIS 28 APPENDIX B: INSTRUMENTATION AND MEASUREMENT SYSTEMS 3 APPENDIX C: WIND-TUNNEL ATMOSPHERIC FLOW SIMILARITY PARAMETERS 33 APPENDIX D: WIND-TUNNEL ATMOSPHERIC BOUNDARY-LAYER SIMILARITY 37 APPENDIX E: WIND-TUNNEL STACK MODELING PARAMETERS 42 APPENDIX F: INDIVIDUAL EXHAUST STACK INFORMATION 44 APPENDIX G: INDIVIDUAL EXHAUST STACK EMISSION RESULTS 45 APPENDIX H: EMERGENCY DIESEL GENERATOR EMISSION RESULTS 94

3 Executve Summary Wnd-tunnel tests were conducted to assess the mpact of the proposed development of Buldng #3 on the ar qualty of the Chron ste and nearby resdental neghborhoods. Testng modeled the ndvdual and cumulatve effects of Buldng Nos. 3 and 4 stacks on ther own and other buldngs HVAC nlets and other off-campus areas. After testng the ntal desgn and after mnor modfcatons to the desgn, the fnal results from the wnd-tunnel studes predcted no volatons of the EIR establshed dluton standard of 7:1. When effectve cumulatve dluton (.e., dluton calculated based on the cumulatve concentraton at a receptor due to all upwnd stacks of Buldng Nos. 3 and 4) was consdered, all receptor locatons, both on and off ste, exceeded the mnmum 7:1 dluton crteron. All ndvdual and cumulatve exposures of off-ste locatons (resdental, schools, etc.) exceeded the recommended dluton standard 1:1 and the requred dluton crteron of 7:1; and, most ndvdual and cumulatve exposures of on-ste locatons exceeded the mnmum dluton standard of 7:1. Whle these dluton crtera judged are suffcent to protect on-ste workers and vstors from known potental routne chemcal exposures, the crtera do not necessarly provde suffcent dluton to protect aganst accdental releases of larger amounts of some chemcals, or from release of smoke from a fre, or of contagous bologcal or radoactve materals. For ste locatons subject to these contngences (.e., exhaust stacks servng laboratores where such specal chemcals or hghly contagous bologcal or radoactve materals would be used, or those proxmate to offce buldng HVAC ar ntakes), dluton factors far n excess of 7:1 standard would be needed. These were not addressed n ths study. Emergency Desel Generators located on Buldng Nos. 3 and 4 and Buldng CMF were tested at ten receptor locatons for three wnd drectons, west, north-northwest and southsoutheast. Almost all receptors showed dluton values less than standards (2:1 for falure, 5:1 for cauton) for all wnd drectons and wnd speeds tested. The bggest contrbutor to the low dluton levels was the desel generator located at Buldng CMF. Table 2 shows the cumulatve hours per year that each desel generator causes less than standard condtons at each receptor locaton tested. It s recommended that Buldng CMF s desel generator use a plenum ar makeup unt to ncrease dluton measurements at all receptor locatons, and that all receptor 1

4 locatons on Chron Way use a control system to automatcally shut down whle the emergency desel generators on Buldng Nos. 3 and 4 are actve. Stack Elevaton [ft]: Emsson Rate [g/s]: Scale Factor: Less than Standards [hrs/yr] Receptor #3 #4 CMF #3, #4 #3, CMF #4, CMF #3, #4, CMF ID cauton fal cauton fal cauton fal cauton fal cauton fal cauton fal cauton fal *Results based on ESMUD Wnd Data **Cauton dluton standard s 5:1, falng dluton standard s 2:1 ***Results assume a 24 hr/day operaton. 2

5 1. Background The wnd-tunnel tests were conducted by constructng a scale model of the project, ncludng surroundng buldngs on ste, and testng t n a wnd tunnel to examne how the buldng desgn effects stack performance, or how well emssons are dluted n the atmosphere. The model was constructed to be consstent wth the desgn plans provded by Flad & Assocates and AEI, Inc. The model reflected the most current nformaton avalable regardng Chron s proposed desgn at the tme of testng. Typcal receptor locatons, ncludng HVAC ntakes, buldng entrances, courtyards, and nearby resdences n the vcnty of the project, were dentfed and wnd-tunnel testng was conducted to determne the mnmum level of dluton that would occur at these receptors for emssons from the proposed Buldng Nos. 3 and 4 stacks. In addton, tests were conducted on the effect of the emergency desel generators n Buldng Nos. 3 and 4, and the CMF buldng s emergency desel generator. The EIR analyss (after consderng the toxc ar contamnant emsson rates estmated to result from the project, toxc characterstcs of emtted substances, types of receptors near emsson sources, and proposed stack desgns) developed an operatonal dluton goal (or dluton standard) to mnmze potental health and safety effects at receptor locatons (Johnson, 1994; and, ESA, 1995). The dluton goal (or mnmum dluton crteron) represents the mnmum desred rato between the relatve concentraton of the ar-mxed emsson when t reaches a receptor locaton and the relatve concentraton of emssons at the stack ext. The recommended dluton crteron was 1:1 and the mnmum dluton crteron was 7:1 (Johnson, 1994; and, ESA, 1995). For testng roof-top exhaust stacks n the wnd-tunnel, a neutrally buoyant tracer gas (ethane) was emtted from varous representatve stacks on the scale model wth the resultant concentraton of the tracer gas at the receptor locatons measured. Receptor measurements were conducted usng the upwnd drectons (.e., the ncluded wnd angle that resulted n measurable levels of effluent at a receptor). From these tests, expected mnmum dluton factors could be determned for varous combnatons of stacks and receptors tested. 3

6 2. Introducton Project Locaton Ths report addresses the Phase II project of the Chron Emeryvlle Campus Expanson Program. The Phase II project nvolves the addton of Buldng Nos. 3 and 7B to the exstng buldngs on the current Chron campus. Buldng #3 wll be a sx-level laboratory-offce buldng complementng the exstng Buldng #4; and, Buldng #7B wll be a two-story central utlty plant, complementng the exstng Buldng #7A. The Chron campus s located n Emeryvlle, Calforna, east of the San Francsco Bay, as shown n Fg. 1. The campus ste s approxmately bounded by Stanford Street on the north, Horton Street on the west, Holls Street on the east, and 53rd and 47th Streets on the south. Fg. 2 dsplays the ste locaton. Campus-Project Descrpton The Phase II project ncludes the constructon of Buldng Nos. 3 and 7B on Chron s Emeryvlle campus. The exstng campus buldngs wll reman. Fg. 3 ndcates the Phase II campus layout. Floors one and two of Buldng #3 are a combnaton of two-story hgh buldng support spaces, mechancal/electrcal rooms, and several areas of two levels of offces, lab and plot plant and buldng support type spaces. Ar handlng unts for floors 1-5 wll be located on the 1st floor, wth an addtonal unt on the 6th floor to serve floor sx offce space. Floors three, four and fve contan laboratores and offce areas. Floor sx ncludes offce areas and mechancal rooms. There s a mechancal penthouse on level seven, whch houses mechancal equpment. The buldng exhaust systems wll nclude four central exhaust systems and numerous dedcated exhaust systems. The exhaust stacks from these systems, wll be grouped nto four areas on the roof. The frst and second group of stacks wll be at the sxth floor (northwest and southeast cones) and the thrd and fourth group of stacks at the seventh floor (southeast and northwest cones). The thrd and fourth group of stacks wll be at the seventh floor located on top of the mechancal penthouse. The man exhaust stacks wll be szed to provde an average exhaust ar 4

7 5

8 6

9 7 Fgure 3. Current Phase II of the Chron campus expanson.

10 velocty of 3,5 fpm wth energy savng VFD s allowng an operatng range between 4, fpm and 2,5 fpm. In addton to the HVAC exhaust systems, there s a desel emergency generator set on the frst floor wth an exhaust outlet at the west sde terrace areas of the second level of both Buldng Nos. 3 and 4. Also, the desel emergency generator of Buldng CMF, located on the west sde of Buldng F, was tested. Buldngs No. 7B s a two-story central utlty plant addton to buldng 7A. The frst floor wll house chllers, wth bolers located on the second floor. The coolng towers and boler exhaust stacks wll be located on the roof. Study Objectve The objectve of the present study s to determne the potental for re-entranment of exhausts from Buldng Nos. 3 and 4 nto ts own HVAC ntakes and/or other HVAC ntakes wthn close proxmty. Ths study also estmates the levels of contamnaton at other senstve areas on the campus (.e., courtyards, buldng entrances, etc.) and at adjacent propertes. These propertes nclude the Pacfc Rm School (corner of Doyle and Stanford Streets), the Artsts Cooperatve Housng, neghborng resdences, MEI (Maxmum Exposed Indvdual) prevously dentfed by computer smulaton (ESA, 1995), Day Care Center, and Emeryvlle Hgh School. Ths study also ncludes analyss of Buldng Nos. 3 and 4 and CMF emergency desel fuel generators on Buldng Nos. 3 and 4 and Buldng CMF. 3. Analyss of Near-feld Ar Toxcs The dsperson of potentally hazardous exhaust s of great concern, and several dfferent methods for predcton and analyss of the atmosphere s ablty to dlute pollutants before the gases mpact senstve receptors have been developed. In the envronmental assessment of an exhaust stack, emprcal or computer analyss may be employed, full-scale tests may be conducted, and/or wnd-tunnel tests may be carred out. Whch of these methods to use depends on such factors as economc constrants, the physcal regon of nterest, and qualty and accuracy of the desred results. Varous knds of emprcal-analytcal methods have been developed to evaluate dsperson; however, each method generally apples only to specfc areas of concern. Also, most numercal 8

11 models are lmted by falng to account adequately for local buldng wake effects or by requrng nput of locally measured buldng wake and turbulence data. Full-scale dsperson tests can provde useful concentraton data. However, full-scale testng of dfferent wnd drectons and speeds along wth vared atmospherc stablty s usually mpractcal. Interpretaton of full-scale data s complcated by changng atmospherc condtons; and, the evaluaton of an unbult structure s, of course, not possble. Wnd-tunnel tests can be conducted under deal, steady wnd condtons. Such tests, conducted properly, account for the effects of buldng aerodynamcs and ste specfc wnd-flow patterns created by the test buldng and surroundng buldngs, trees, and topography. The results can be used to dentfy potental dluton problems. ASHRAE (1997) provdes a good dscusson of the valdty of wnd-tunnel modelng as a proven accurate means to smulate the dsperson of stack exhausts n the atmosphere. ASHRAE acknowledges the superorty of wndtunnel data over that of emprcally calculated predctons. Wnd-tunnel tests can precsely smulate crtcal condtons occurrng n full scale. Wndtunnel tests can smulate the average or mean wnd speed dsperson of exhausts, as well as the so-called worst-case dsperson of exhausts, and other types of condtons that may be of nterest. The worst-case dsperson of exhaust s generally used to determne the mnmum level of dluton from an exhaust source that mght occur under an accdental-release condton. Ths test represents a sngle wnd drecton at a sngle wnd speed; ths combnaton produces the mnmum dluton of all possble wnd drectons and speeds. Usually, the occurrence of such a specfc condton s statstcally small and typcally wll comprse only a few hours or less of an annual meteorologcal data set. Thus, the worst-case dsperson case refers to an accdent stuaton that s used to determne f short-term exposure lmts (e.g., 15 mnutes, 1 hour, etc.) are exceeded at senstve receptor locatons. In contrast to the worst-case analyss s the routne release analyss. Under routne release testng, the normally expected exposure of emssons over a specfed tme perod s estmated. Typcally the tme perod s one year thus predctng annual exposure levels, although any tme perod could be used (.e., one month, etc.). For annual routne exposure analyss, the average concentraton contrbuton from each of the 16 wnd drectons n 22.5 degree ncrements s measured (ASHRAE, 1997). The 16 major wnd-drecton measurements then can 9

12 be ntegrated nto the meteorologcal data for frequency to estmate ndvdual receptor annual exposure levels. In contrast, the worst-case dsperson of exhausts s assumed to occur when a gven senstve locaton s located drectly downwnd of the emsson source for the so-called crtcal wnd speed. The crtcal wnd speed les between lower wnd speeds whch generally create a large exhaust dluton due to enhanced plume rse, and hgher wnd speeds, where the vertcal exhaust stream s rapdly dffused horzontally and mxed wth the turbulent movng ar. At ths sngle crtcal wnd speed, the benefcal effects of plume rse (low speed) and mxng (hgh speeds) are compromsed, and the mnmal dluton of exhaust stack emssons results. 4. Crtcal Wnd Speed The crtcal wnd speed, as mentoned above, represents the mnmum dluton condton for a gven exhaust emsson at a specfc receptor locaton. The value of the crtcal wnd speed s not constant for all stacks; t depends on the sze of the stack, the exhaust speed, and the dstance between the emsson source and the specfc receptor locaton. Thus, for a sngle stack there wll be as many crtcal wnd speeds as there are receptor locatons. ASHRAE (1997) provdes an equaton for theoretcally calculatng the crtcal wnd speed whch s gven as U crt, = 36. B1 Ae Ve S U crt, o s the crtcal wnd speed producng the smallest mnmum dluton for an uncapped vertcal exhaust wth neglgble stack heght. V c s the exhaust speed of the stack. B 1 s called the dstance dluton parameter. B 1 depends on the exhaust plume trajectory, turbulence ntensty of the approach wnd and turbulence generated by the buldng. The upwnd level of turbulence s gven by σ θ, the standard devaton (n degrees) of wnd drecton fluctuatons averaged over a 1 mnute perod. Wlson and Lamb (1994) gve B 1 = σ θ. The recommended desgn value for buldngs n an urban terran (Category B, α=.22, δ = 37 m) s σ θ equals 15 degrees, whch makes B 1 equal to.59 (ASHRAE, 1997). 1

13 For the present case, the expermentally determned crtcal wnd speeds were found from wnd-tunnel testng by varyng the approach wnd speed n the tunnel. The more conservatve of the measured values (.e., the one that resulted n the lower value of mnmum dluton) was used to assess the mnmum dluton standard. Ths technque should be appled snce the theoretcal crtcal wnd speed from the ASHRAE dluton equatons addresses only smple buldng shapes and the equaton was emprcally determned from full-scale and wnd-tunnel tests. The theoretcal estmate of crtcal wnd speed does not account for ste specfc buldng geometry and surroundng topographc condtons. 5. Atmospherc Stablty Plume behavor wll vary suffcently for dfferent atmospherc condtons. The thermal stratfcaton of the atmosphere has great nfluence on the long-range dsperson of an exhaust plume. Vertcal wnd shear, due to thermal effects, also can result n unexpected plume rse. A common classfcaton scheme used to categorze atmospherc dffuson by ts stablty s Pasqull stablty. Table 3 shows the sx stablty classes by Pasqull (1961) and later modfed by Turner (1967). Classes A to C represent unstable condtons, characterzed by strong vertcal dffuson due to the buoyancy and shear producton of turbulence. Class D represents nearneutral condtons, where buoyancy effects are unmportant and nearly all turbulence knetc energy s taken from the shear n the mean flow. Classes E and F represent stable condtons, characterzed by weak dffuson and turbulence, nhbtng mxng and dluton of the plume wth the ambent ar. Stablty Class F has the potental to be the worst-case condton f the wnd drecton algns the plume centerlne trajectory wth the heght of the receptor. The wnd-tunnel smulatons represent near neutral to slghtly unstable atmospherc condtons. Therefore, the wnd-tunnel tests cannot reproduce the worst-case condton that mght occur for a stable atmosphere. However, n the near feld (dstances less than 1 meters), the stablty of the atmosphere wll not greatly alter the dsperson from that whch occurs under the neutral condtons (whch are modeled n the wnd tunnel), snce the presence of the buldng would mechancally ntroduce turbulence (through vortcty sheddng and wake formaton), whch would effectvely negate the stratfcaton effect on the dsperson process. In addton, the 11

14 wnd tunnel does model ste-scentfc dsperson characterstcs unque to the specfc case consdered, whch n general results n more accurate estmates than other methods. Table 3. Meteorologcal Condtons Defnng Pasqull Turbulence Type /a/ Surface Wnd Speed m/s Daytme Insulaton Nghttme Condtons /c/ thn overcast or > low hgh strong moderate slght 4/8 low clouds < 3/8 cloudness <2 A AB B 2 3 AB B C E F 3 4 B BC C D E 4 6 C CD D D D >6 C D D D D A. Extremely unstable condtons D. Neutral condtons B. Moderately unstable condtons E. Slghtly stable condtons C. Slghtly unstable condtons F. Moderately stable condtons /a/ From F. A Gfford, Turbulent dffuson typng schemes: a revew. Nuclear Safety, 17(1):71, /b/ /c/ Apples to heavy overcast day or nght. Degree of cloudness s that fracton of sky above the local apparent horzon that s covered by clouds. In the mmedate buldng and stack vcnty, local mechancal turbulence s prmarly governed by the buldng, roof and stack-flow nteractons. Therefore, the plume behavor s not greatly nfluenced by the atmospherc stablty. However, the further away the plume travels, the greater the nfluence of the thermal stratfcaton of the atmosphere becomes. Atmospherc stablty may affect the dsperson at senstve receptors that are located at dstances greater than a few buldng lengths downwnd from the source. For the Chron ste, the buldng length s effectvely square (2 m n an east-west drecton and about 2 m n a north-south drecton). Thus, the closest resdences and the locatons of concern are wthn ths crteron dstance. Therefore, the neutral atmospherc stablty s approprate for the present testng stuaton. Further reason for usng a neutral atmosphere n the present wnd-tunnel testng s provded by consderaton of the exstng meteorologcal condtons at the Chron ste. For the condtons at the Chron ste, the one-year East Bay Muncpal Utlty Dstrct meteorologcal data set 12

15 ndcates that Pasqull stabltes A through C occur only about 6.6% of the tme, D stablty occurs 61.8% of the tme, and E and F stabltes occur about 29.5% and 2.2% of the tme, respectvely. The wnd tunnel models the Pasqull stablty class D. A reasonable technque to account for adverse atmospherc stablty s to utlze the wndtunnel ste-specfc results and apply an atmospherc correcton factor, as necessary, to account for the non-neutral atmosphere. However, snce the dstances from the emsson sources are all wthn the range of one or two effectve buldng-lengths and because the domnant stablty class s Class D, the wnd-tunnel condtons adequately represents the ste stablty. Therefore, no atmospherc stablty correcton factor was appled to the wnd-tunnel data. ASHRAE (1997) also states, For most applcatons related to arflow around buldngs, neutral stratfcaton s assumed (for physcal modelng), (.e., no stablty correcton factor s requred). 6. Meteorologcal Data/Wnd Clmate Knowledge of the typcal prevalng wnd speeds and drectons s mportant n properly assessng the wnd-tunnel results. Ths nformaton s useful for determnng the dstrbutons of occurrence of certan wnd flow drectons whch may gve rse to mnmal dluton levels for some emsson source - receptor combnatons. The wnd meteorologcal data records (met data) that prevously was used n the E.I.R. for the ISCST computer analyss of the Chron Development Plan also was used n the present study. A one-year perod of met data was avalable from the East Bay Muncpal Utlty Dstrct (EBMUD) wastewater treatment planet located approxmately one mle South of the Chron ste. Ths met data record had been prepared and approved by the BAAQMD for use n the screenng level ISCST2 computer model calculatons. Therefore, ths same met data set was used for the present study. Table 4 presents the met data n tabular form. 7. Dluton Crtera Exhaust Stack Dluton Crtera A prmary goal n ths study was to determne f exhaust emssons from the proposed Buldng No. 3 and exstng Buldng No. 4 would meet the establshed dluton standard for routne chemcal releases (as opposed to an accdental or unntended chemcal release). At the 13

16 same tme, t s desrable to avod possbly over-desgnng the exhaust systems by requrng, for example, excessvely tall stacks. Rather than relyng solely on non-ste specfc estmates provded by the analytcal methods, (.e., ASHRAE models), or by computer models (such as ISCST2), physcal modelng was used to provde a more realstc ste-specfc evaluaton of stack dsperson of the near-feld dsperson process n the vcnty of the project ste. Table 4. EBMUD Wnd Data Wnd Drecton Duraton n hours for each wnd speed bn, n m/s Drecton Azmuth Total N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW Total 876 ESA (1994 and 1995) used two methods consdered for use n developng conservatve dluton crtera for the project. The frst method consdered only antcpated routne releases (Johnson, 1994), and gnored accdental releases of emssons. The second gnored routne releases and focused on accdental releases of chemcals n a laboratory. The routne release standard was selected for the present study as specfed by Chron (Johnson, 1996). The objectve of ths analyss was to evaluate the routne operatonal health and safety effects of the development of the project. The dluton calculaton, usng the routne release premse (Johnson, 1994; and, ESA, 1994 and 1995), resulted n the followng dluton standards based on fve dstnct health-related crtera, as shown n Table 5. What s requred, then, s to meet the most strngent of the crtera above. Consequently, f wnd-tunnel testng ndcates that the project can feasbly meet a dluton crteron of about 7 to 14

17 1, then t s clear that the project can be constructed to avod sgnfcant mpacts related to cancer rsk, non-cancer health effects, and acute health effects of routne releases. The second method uses a worst-case analyss based on an accdental release, a spll, durng crtcal dsperson wnd condtons. That crteron has been used by the Unversty of Calforna at Davs (Whte et al., 1991) as a mnmum dluton crteron for exhausts from laboratory fume hoods. Table 5. Dluton Crtera for Routne Release Health Effect Standard Dluton Crteron Cancer Rsk (resdental) 69 to 1 Cancer Rsk (occupatonal) 45 to 1 Non-Cancer Chronc Health Effects (resdental) 57 to 1 Non-Cancer Chronc Health Effects (occupatonal) 38 to 1 Acute Health Effects 3.3 to 1 That standard appled to non-cancer health effects; the cancer health rsks specfcally were not consdered. For ths standard, no more than one accdental release was assumed to occur at any one tme (multple releases could occur as long as ther occurrences do not overlap) and the maxmum event would be the spll of a four-lter bottle of solvent. The Davs campus dluton crteron (Seabury, 1991 a, b, c and d) was 6:1 and amended around 2 to 1:1, meanng that one part fume-hood emssons dluted by 1 parts uncontamnated ar would not exceed that exposure standard. The accdental release crteron was not used as the standard n ths study snce the present ntent was to evaluate only long-term operatonal health and safety effects. In summary, the mnmum dluton crteron or standard used n ths study s 7:1 wth a recommended level of 1:1 f possble (Johnson, 1994 and 1996; and, ESA, 1994 and 1995). Ths mnmum crteron addresses only routne releases of chemcals that would be expected from operatons of the project. The 7:1 crteron does not provde the level of protecton whch 15

18 mght be needed to avod adverse acute health effects that mght occur as the result of accdental releases of toxc materals under certan combnatons of wnd drecton and speed. Desel Exhaust Dluton Crtera For exhausts from emergency desel generators located at Buldng Nos. 3 and 4 and Buldng CMF, dfferent dluton crtera s necessary. Desel exhaust s a complex mxture of thousands of organc compounds, of whch hundreds contrbute to ts odor. Odor ntensty has been well correlated wth the oxygenated (smoky-burnt) porton of the emtted hydrocarbons, although odorous non-hydrocarbons are also present. Therefore, t would be dffcult to evaluate desel exhaust n the same manner utlzed for fume hood exhaust. Instead, desel exhaust s evaluated as a sngle entty to dentfy odor thresholds. Odor panel data presented n Cernansky (Journal of The Ar Polluton Control Assocaton, 1983) ndcates that approxmately 2 percent of persons would object to odors when exhaust s dluted by a factor of 4:1. Recent data from Vanderheyden (87 th Annual Meetng of the Ar & Waste Management Assocaton, 1994) ndcate that a dluton level of 2:1 correlates to the 2 percent objecton level. The 2:1 dluton level s typcally used as an odor threshold as t was n ths project. Odors at ths dluton level wll stll be detectable by most persons and wll be objectonable to only about 2 percent of the populaton. Health lmts for desel exhausts are above ther respectve normalzed odor thresholds (Ar Qualty and Pedestran Level Wnd Evaluaton Walker Hall Sesmc Replacement Faclty Unversty of Calforna at Davs, 1997 (CPP Project )). Therefore, the desgn crtera for both sources s based on a more conservatve cautonary odor threshold value of 5:1, and a falng odor threshold of 2:1. 8. Stack Parameters Dluton of source emssons from a gven stack can be mproved by ether ncreasng the heght of the stack, or by ncreasng the exhaust velocty through the stack. In some nstances, however, ncreasng the stack velocty may not be an effectve means to ncrease dluton dependng upon where the trajectory of the exhaust plume mpacts ether the ground or another buldng,.e., HVAC nlets. Both desgn varables, stack heght and speed, were consdered n 16

19 ths analyss. However, ncreasng the stack heght would most lkely prove to be the most effectve and economcal means to ncrease the level of dluton at senstve receptors. 9. Wnd-Tunnel Testng The atmospherc boundary layer s that layer of ar coverng the earth that s drectly affected by frcton between the ground and atmosphere as the ar flows over the planet s surface. In order to study the dsperson of gases n the atmosphere, the flow characterstcs of the atmosphere n the regon referred to as the atmospherc boundary layer must be consdered. Physcal modelng of dsperson n ths regon s conducted n an envronmental or atmospherc boundary layer wnd tunnel. The Atmospherc Boundary Layer Wnd Tunnel (ABLWT) at U.C. Davs s such a faclty and was used for all gas dsperson tests made for ths study. Testng was carred out on a 1 nch equals 3 feet (1:36) scaled model that ncluded the project buldngs as well as major off-ste buldngs wthn a dameter of one-half mle from the ste. The area modeled n the wnd tunnel was about one-quarter mle normal to the approachng wnd drecton and approxmately one mle n the drecton of the wnd flow. A hydrocarbon analyzer was used to measure qualtatvely the downwnd dsperson of buldng emsson sources. A tracer gas, ethane, njected through modeled exhaust stacks was sampled at specfc crtcal locatons (courtyard locatons, ventlaton ntakes, etc.) downstream of the stack n the wnd-tunnel test secton. Vertcal wnd speed to exhaust speed momentum smlarty was matched n all wnd-tunnel tests. A tme-averaged concentraton measurement was made per senstve receptor. An ndvdual measurement was a tme average of 3, ndvdual dgtzed samples collected over a 3 second perod to produce a mean concentraton, after beng corrected to account for the varable background level of ethane concentraton. Wnd-tunnel testng of emssons from all buldngs examned representatve exhaust stacks for a range of stack characterstcs, ncludng varous approach and exhaust veloctes. Generally, a representatve stack wthn a groupng of several stacks was modeled n the wnd tunnel. Ths approach allowed for all stacks to be accounted for by ether drect testng or through the extenson of wnd-tunnel results to adjacent stacks n the same stack groupng area. Over 2 selected receptor locatons were sampled n a general test program to characterze the dlutons at on-ste locatons on and around the ndvdual buldngs of the Chron ste. On- 17

20 ste measurement receptor locatons were selected to dentfy potental low-dluton condtons at buldng entrances, HVAC ntakes, and pedestran walkways and plazas. Usng ethane as a tracer gas, wnd-tunnel measurements were made for the dluton of emsson sources at the specfed downwnd receptor locatons, such as future courtyards, pedestran areas, ventlaton ntakes and roof-top locatons on surroundng buldngs. The measured dluton values were compared wth the prmary exhaust dluton acceptablty crteron (the routne release standard) of 7 to 1 to evaluate the feasblty that the project would relably meet the health and safety goals for long-term routne release operatons. Ths crteron, when taken together wth the evaluatons carred out n the envronmental mpact report, provdes a suffcent bass to reach vald conclusons about the ablty of the project to be bult to satsfy those goals wthn acceptable health and safety standards. The testng focused on determnng f the project exhaust would meet the mnmum dluton crteron at all dentfed senstve receptor locatons. If the desred dluton levels were not met, an effort would be mounted frst to dentfy and characterze potental mtgaton measures, and then to evaluate the effectveness of the measures to meet the dluton crteron, such as ncrease the stack heght, alter the flow velocty or adjust the stack locaton untl the mnmum dluton crteron was acheved. 1. Wnd-tunnel Test Results A 1 nch equals 3 feet model was constructed from Phase II scope of work plan provded by Flad & Assocates and AEI, Inc. After completon of the model, an approval meetng was held at Chron n Emeryvlle (Aprl, 22) n whch representatves from Chron and Afflated Engneers, Inc. (AEI) approved the model accuracy wth the ncluson of several then recent desgn changes that were subsequently ncorporated nto the model. Therefore, the most current verson of the model at the tme of wnd tunnel testng was used. The locaton of the measurement receptors s shown n Fgs. 4 and 5. Table 6 provdes a bref descrpton of each receptor locaton. These measurement locatons are comprsed of all HVAC nlet areas of Buldngs Nos. 3, 4, M, F, and CMF. Adjacent propertes receptor locatons were dentfed at the closest resdental housng area, Pacfc Rm School, The Day Care Center, Emeryvlle Hgh School, Artsts Cooperatve Housng and the MEI (Most Exposed Indvdual) 18

21 prevously determned from the ar dsperson computer modelng U.S. EPA-approved Industral Source Complex Short Term (ISCST2) ar pollutant dsperson model for a smlar type emsson source (ESA, 1994). Table 6. Receptor Locatons Receptor Buldng Locaton 16 4 East sde of bldg, 2nd floor ntake 17 4 East sde of eastern penthouse 18 4 North sde of eastern penthouse th floor rooftop near elevator 2 4 West sde of bldg, 6th floor 21 4 West sde of bldg, southern end of 2nd floor 22 4 West sde of bldg near brdge, 2nd floor 23 3 West sde of bldg, north of brdge, 2nd floor 24 3 West sde of bldg, northern end of 2nd floor 25 3 South sde of bldg, 6th floor 26 3 West sde of bldg, 6th floor 27 3 North sde of bldg, 6th floor, above desel generator 28 3 South sde of eastern penthouse 29 3 West sde of eastern penthouse 3 3 North sde of eastern penthouse 31 3 East sde of eastern penthouse 32 3 East sde of bldg, 2nd floor 34 M East sde of penthouse 35 CMF Eastern rooftop, southern end of bldg 36 F Mddle of southern quadrant of roof 99 M South sde of northern penthouse 19

22 Fgure 4. Receptor locatons on model, pcture taken of the West sde of Buldng Nos. 3 and Fgure 5. Receptor locatons n model, pcture taken of the East sde of the Buldng Nos. 3 and 4. 2

23 Buldng Nos. 3 and 4 Receptor Tests The receptors represent areas of nterest such as HVAC ntakes, courtyard areas, pedestran walkways and off-ste senstve areas: day care center, school, resdental housng areas, and medcal facltes. Twenty of the receptor locatons were on ste and fve receptor locatons were off ste to address resdental and communty concerns. Table 6 provdes a descrpton of each of the receptors measured. Each of the sx representatve stack source areas, also referred to as cones, from the four emsson areas of the roof of Buldng #3 and the two emsson areas of Buldng #4, that were tested n the wnd tunnel, are gven n the tables. For a gven receptor, only certan wnd drectons resulted n exposure to stack emssons. These wnd drectons were prmarly upwnd of a specfed stack-receptor combnaton. Accordngly, only concentraton measurements at receptors n the general downstream area were measured n accordance wth ASHRAE specfcaton, whch are: the test program must nclude specfcatons of the meteorologcal varables to be consdered. These nclude wnd drecton, wnd speed and thermal stablty. Data taken at the nearest meteorologcal staton should be revewed to obtan a realstc assessment of wnd clmate for a partcular ste. Ordnarly, local wnds around a buldng (Buldng #4), pressure, and/or concentratons are measured for 16 wnd drectons n 22.5 degree ntervals (.e., east wnd, east northeast wnd, northeast wnd, etc.). If only local wnd nformaton and pressures are of nterest, testng at one wnd speed (average for that drecton wth neutral stablty) s suffcent. Followng these ASHRAE gudelnes, the test program was desgned to measure concentraton exposures at each receptor locaton due to each of the 22.5 degree wnd drectons. The tests were conducted at the scaled respectve average wnd speed from the meteorologcal data for each of the 16 wnd speed drectons beng tested. The analyss of the wnd-tunnel concentraton measurements nvolved determnng two features of the dsperson process: ) estmate the ndvdual stack-receptor dluton for all stack receptor locatons possble (multple stacks n each of the 6 cones tme 2 receptors); and, 21

24 ) a calculaton of effectve cumulatve dluton for each sngle receptor for each 22.5 degree wnd drecton to nsure t does not drop below effectve dluton crteron of 7:1 (for any hour averaged tme nterval). Wnd-tunnel tests were conducted for each of the major sxteen 22.5 degree meteorologcal wnd drectons. For each of these 16 wnd drectons, each one of the nne representatve stacks were tested separately to dentfy ndvdual contrbutons to the total or cumulatve concentraton. All nne representatve stacks were wnd-tunnel tested. All downwnd receptors wthn the ncluded wnd angle of 22.5 degrees were measured for each of the fve representatve stacks tested. For the purposes of evaluatng the standard, the total concentraton exposure was determned by frst multplyng the concentraton of the representatve stack by the actual number of stacks that would operate n that gven emssons area; and, secondly, addng them together the concentraton exposure from all operatonal stacks at the receptors for that partcular wnd drecton. Indvdual and Cumulatve Stack-Receptor Measurements For each stack tested, the receptors downwnd for a specfed wnd drecton were measured. Indvdual as well as cumulatve stack results for all receptors are found n the Appendx of ths report. Indvdual fumehood exhaust toxctes, gven n Appendx F, were appled to the result n Appendx G, whch presents the ndvdual stack-receptor combnaton and cumulatve concentratons and dlutons for the 2 receptor locatons that were measured. The wnd drecton that wll delver the stack emsson effluent to the receptor s gven n the second column of the table. Typcally, only one to three wnd drectons wll produce effluent at a gven receptor as observed n the second column. The other wnd drectons would not contrbute to the concentraton. The concentratons are gven n columns n parts per mllon (ppm). The emsson source s one mllon parts per mllon; therefore, the concentraton measured at the receptor represents the nverse of the dluton level that would be acheved. The cumulatve concentratons of all Buldng Nos. 3 and 4 stacks are also ncluded n the fnal effectve dluton numbers. The lower lstngs n Appendx G present the same data; however, concentraton s converted to dluton levels. For cumulatve effects of multple stack effluent at a sngle receptor, the 22

25 cumulatve concentratons of all contrbutng stacks are added together to produce a total exposure concentraton, whch s then converted nto a dluton factor. Ths factor s called the effectve dluton snce t ncorporates cumulatve effects of all stacks nto a sngle dluton. The effectve dlutons ranged from 49:1 to thousands-one as observed n Appendx G. Over 2 receptor locatons were measured to determne dluton levels caused by the stacks on the roof of Buldng Nos. 3 and 4. The receptor locatons ncluded HVAC ntakes of Buldngs Nos. 3 and 4, M, CMF and F. Addtonally; all off-ste senstve areas prevously dentfed (ESA, 1995) were tested. Pedestran walkways, courtyard area, bus stops, etc., were also tested for locatons both on and off ste. For cumulatve effects of multple stack effluent at a sngle receptor locaton, the cumulatve concentratons of all stacks were added together to produce a total exposure concentraton, whch was then converted nto a dluton number (called the effectve dluton ) snce t ncorporates cumulatve effects of all stacks. All dlutons of ndvdual stacks were well n excess of the recommended and mnmum dluton standards (.e., 1:1 and 7:1, respectvely). All other cumulatve effects of the stacks resulted n dlutons greater than the recommended standard of 1:1, for the senstve on- and off-ste receptors (.e., resdual, schools, HVAC ntakes, etc.). Emergency Desel Generator-Receptor Measurements Emergency Desel Generators located at Buldng Nos. 3 and 4 and CMF were tested at ten receptor locatons for three wnd drectons, west, north-northwest and south-southeast. Vrtually all receptors showed dluton values less than standards (2:1 for falure, 5:1 for cauton) for all wnd drectons and wnd speeds tested. The bggest contrbutor to the low dluton levels was the desel generator located at Buldng CMF. Appendx H shows the ndvdual desel stack results for each wnd speed and drecton, and Table 2 n the Executve Summary shows the cumulatve hours per year that each desel generator causes less than standard condtons at each receptor locaton tested, and shows that Buldng CMF s desel generator causes dlutons of less than 5:1 at all receptor locaton for 3496 hours per year, or approxmately 4% of the tme over a one-year perod of tme. Buldng #3 s desel generator produces cautonary dluton levels (less than 5:1) for Receptors #2, #24 and #25 for 16, 23 and 4 percent of tme per year, respectvely, and falng dluton levels (less than 2:1) for 23

26 Receptor #24, #25, #26 and #27 for 6, 12, 16 and 7 percent of tme per year, respectvely. The emergency generator at Buldng #4 causes dluton values less than the cauton standard at receptor locatons #21 and #25, 25 and 3 percent of tme annually, and falng dluton values at receptor locatons #2-#22 and #23-#27 for 16 and 14 percent of tme annually, respectvely. It s recommended that Buldng CMF s desel generator use a plenum ar makeup unt to ncrease dluton measurements at all receptor locatons, and that all receptor locatons on Chron Way use a control system to automatcally shut down whle the emergency desel generators on Buldng Nos. 3 and 4 are actve. 11. Wnd-Tunnel Test Conclusons The Chron campus establshed mnmum dluton standard of 7:1 was used n accessng the acceptablty of stack dsperson, regardless of receptor locaton. Usng ethane as a tracer gas, wnd-tunnel measurements were made of the dluton of roof exhausts at specfc receptor locatons, such as HVAV ntakes on both Buldng Nos. 3 and 4 and the exstng nearby buldngs on and off ste. A mnmum dluton standard of 2:1 was appled to receptor locatons exposed to the exhaust of emergency desel generators located on Buldng Nos. 3 and 4 and Buldng CMF. Wnd-tunnel testng of emssons from Buldng Nos. 3 and 4, as well as stacks of nearby buldngs, examned representatve exhaust stacks for a range of stack characterstcs. Generally, a representatve stack wthn a groupng of smlar stacks was modeled n the tunnel (ths resulted n testng several representatve stacks thus accountng for all types of stack-emssondffuson processes). Ths approach allowed for all stacks, whether on an ndvdual bass or cumulatve-effect bass, to be accounted for by ether drect testng or through reasonable extenson of wnd-tunnel results to nearby untested stacks wthn the same cluster or group, of smlar stacks. The wnd-tunnel analyss ncluded testng of seven separate representatve stacks on Buldng #3 and two stacks on Buldng #4. In testng, measurements of exhaust dluton were made at downwnd locatons under ASHRAE-specfed condtons for routne stack dsperson processes (.e., the worst-case accdent release stuaton was not tested). Measured dluton values were compared wth the 7:1 24

27 mnmum dluton crteron (or the less strngent 1:1 recommended crteron) at each receptor. Desel exhaust testng was conducted for three specfc wnd condtons, west, north-northwest and south-southeast nstead of worst-case condtons. Whle above dluton crtera are judged suffcent to protect on-ste worker and vstor health for expected chemcal exposures (ESA 1994 and 1995), the crtera do not necessarly provde suffcent dluton to protect aganst accdental releases of relatvely larger quanttes of some chemcals, or for release of smoke from a fre, or for releases of contagous bologcal or radoactve materals. For these contngences, dluton factors far n excess of 1:1 or hgher may be a desrable desgn goal. Selectons of such a strngent dluton standard would be warranted for exhaust stacks servcng laboratores where such specal chemcals or hghly contagous bologcal or radoactve materals would be used, or for exhaust stacks proxmate to offce buldng HVAC ar ntakes. These were not addressed n ths study. 12. Acknowledgments The author gratefully acknowledges Messrs. Jonathon Byron, James Cheng and Davd Lubtz and Ms. Bethany Kuspa for assstng and conductng much of the wnd-tunnel testng. The contrbutons of Mr. Raj Yadav of Flad & Assocates and the contrbutons of Messrs. Jm Sharp and Todd Bowman of AEI, and Messrs. Nnh Dzoan, Les Slowk, and Laslo Prvar of Chron Corporaton are gratefully acknowledged. A specal thanks s extended to Mr. Joseph Mller of Chron Corporaton for hs patence and specal nterest durng the course of ths wnd-tunnel study. 13. References and Bblography Amercan Socety of Heatng, Refrgeratng and Ar Condtonng Engneers [ASHRAE], 1997 ASHRAE Handbook - Fundamentals, Atlanta, GA, Calforna Ar Polluton Control Offcers Assocaton (CAPCOA), CAPCOA Ar Toxcs Hot Spots Program Revsed 1992 Rsk Assessment Gudelnes, October Cho, Hyon Mann (Greg), Wnd-tunnel and Numercal Smulaton of Flow Over Porous Fences and partcle Saltaton n Atmospherc Boundary Layers, Ph.D. Dssertaton, Unversty of Calforna, Davs,

28 Envronmental Scence Assocates, Techncal Memorandum: Desred Dluton Performance, Chron Development Plan, Envronmental Scence Assocates, Health Rsk Assessment and Wnd Tunnel Modelng: Chron Development Plan, Report, February 1995, Revsed Aprl 24, Hanna, S.R., Brggs, G.A., and R.P. Hosken, Handbook on Atmospherc Dffuson, Techncal Informaton Center, U.S. Department of Energy, Johnson, Stephen R., Letter to Steve Fre of Afflated Engneers Inc., January 31, Ths s also reference ESA, Johnson, Bll, Techncal Memorandum: Chron - - Toxc Ar Contamnants Exhaust Stack Dluton Crtera, Envronmental Scence Assocates, Inc., October 25, Pasqull, F., The Estmaton of the Dsperson of Wndborne Materal, Meterorol. Mag., 9:33-49, Petersen, R.L. and M.A. Ratclff, An Objectve Approach to Laboratory Stack Desgn, ASHRAE Transactons, Vol. 97, Part 2, Plate, E.J., Aerodynamc Characterstcs of Atmospherc Boundary Layers, U.S. Atomc Energy Commsson, Natonal Techncal Informaton Servce, Vrgna, February 198. Seabury, John, Manager, Envronmental Servces, U.C. Davs Offce of Envronmental Health and Safety, memorandum to Bob Strand, U.C. Davs Offce of Archtects and Engneers, March 13, 1991a. Seabury, John, Manager, Envronmental Servces, U.C. Davs Offce of Envronmental Health and Safety, memorandum to Bob Strand, U.C. Davs Offce of Archtects and Engneers, October 22, 1991b. Seabury, John, Manager, Envronmental Servces, U.C. Davs Offce of Envronmental Health and Safety, memorandum to Bob Strand, U.C. Davs Offce of Archtects and Engneers, October 25, 1991c. Seabury, John, Manager, Envronmental Servces, U.C. Davs Offce of Envronmental Health and Safety, memorandum to Janet C. Hamlton, Vce Chancellor, U.C. Davs Offce of Admnstraton, December 12, 1991d. 26

29 Turner, D.B., Workbook of Atmospherc Dsperson Estmates, Publc Health Servce, Publcaton 999-AP-26, Robert A. Taft Santary Engneerng, Cncnnat, OH, Whte, B.R., J.F. Kavanaugh, and K.D. Moran, U.C. Davs Lfe Scences Expanson/Brggs Hall Addton, Wnd-Tunnel Testng Techncal Report, Unversty of Calforna, Davs, Aprl Whte, B.R., Ar Qualty Evaluaton of Stacks Phase One, Lfe Scence Center, Chron Corporaton, Emeryvlle: A Wnd-Tunnel Study, Wnd-Tunnel Testng Techncal Report, Bruce R. Whte, Davs, Aprl 1997, revsed September, Wlson, D.J. and B.K. Lamb, Dsperson of Exhaust Gases from Roof-level Stacks and Vents on a laboratory Buldng, Atmospherc Envronment, Vol. 28, pp m Woodward-Clyde Consultants, Assessment of Ar Toxcs Emssons: Chron Corporaton, Horton Street Campus, Emeryvlle, CA, December 29, Woodward-Clyde, Estmate of Future Ar Toxcs Emssons: Chron Corporaton - Horton Street Campus, Emeryvlle, CA, May 5,

30 APPENDIX A: THE ATMOSPHERIC BOUNDARY LAYER WIND TUNNEL AT UNIVERSITY OF CALIFORNIA, DAVIS In the present nvestgaton, the Atmospherc Boundary Layer Wnd Tunnel (ABLWT) located at Unversty of Calforna, Davs was used (Fgure A-1). Bult n 1979 the wnd tunnel was orgnally desgned to smulate turbulent boundary layers comparable to wnd flow near the surface of the earth. In order to acheve ths effect, the tunnel requres a long flow-development secton such that a mature boundary-layer flow s produced at the test secton. The wnd tunnel s an open-return type wth an overall length of 21.3 m and s composed of fve sectons: the entrance, the flow-development secton, the test secton, the dffuser secton, and the fan and motor. The entrance secton s ellptcal n shape wth a smooth contracton area that mnmzes the free-stream turbulence of the ncomng flow. Followng the contracton area s a commercally avalable ar flter that reduces large-scale pressure fluctuatons of the flow and flters larger-sze partcles out of the ncomng flow. Behnd the flter, a honeycomb flow straghtener s used to reduce large-scale turbulence. The flow development secton s 12.2 m long wth an adjustable celng for longtudnal pressure-gradent control. For the present study, the celng was dverged celng so that a zeropressure-gradent condton s formed n the stream wse drecton. At the leadng edge of the secton mmedately followng the honeycomb flow straghtener, four trangularly shaped spres are statoned on the wnd-tunnel floor to provde favorable turbulent characterstcs n the boundary-layer flow. Roughness elements are then placed all over the floor of ths secton to artfcally thcken the boundary layer. For a free-stream wnd speed of 4. m/s, the wnd-tunnel boundary layer grows to a heght of one meter at the test secton. Wth a thck boundary layer, larger models could be tested and thus measurements could be made at hgher resoluton. Dmensons of the test secton are 2.44 m n stream wse length, 1.66 m hgh, and 1.18 m wde. Smlar to the flow-development secton, the test secton celng can also be adjusted to obtan the desred stream wse pressure gradent. Experments can be observed from both sdes of the test secton through framed Plexglas wndows. One of the wndows s also a sldng door that allows access nto the test secton. When closed twelve clamps dstrbuted over the top and lower edges are used to seal the door. Insde the test secton, a three-dmensonal probe- 28

31 postonng system s nstalled at the celng to provde fast and accurate sensor placement. The traversng system scssor-type extensons, whch provde vertcal probe moton, are also made of aerodynamcally shaped struts to mnmze flow dsturbances. The dffuser secton s 2.37 m long and has an expanson area that provdes a contnuous transton from the rectangular cross-secton of the test secton to the crcular cross-sectonal area of the fan. To elmnate upstream swrl effects from the fan and avod flow separaton n the dffuser secton, fberboard and honeycomb flow straghteners are placed between the fan and dffuser sectons. The fan conssts of eght constant-ptch blades 1.83 m n dameter and s powered by a 56 kw (75 hp) varable-speed DC motor. A dual belt and pulley drve system s used to couple the motor and the fan. Fgure A-1: Schematc dagram of the UC Davs Atmospherc Boundary Layer Wnd Tunnel. 29