APR 1965 Aggregation Methodology

Transcription

1 Sa Joaqu Valley Ar Polluto Cotrol Dstrct APR 1965 Aggregato Methodology Approved By: Sged Date: March 3, 2016 Araud Marjollet, Drector of Permt Servces Backgroud Health rsk modelg ad the collecto of emssos vetory are ecessary for varous Dstrct ad state programs. Emssos vetory reportg ad modelg for small quattes of emssos sources are typcally expedtous compared to projects wth umerous emssos sources. I some cases, facltes or projects ca volve hudreds or thousads of emssos sources or compoets. Due to resource costrats, t may ot be practcal to report ad/or model that may compoets or emsso sources dvdually. I order to maage the reportg ad/or modelg of emssos from a large umber of compoets, aggregato of smlar compoets to a sgle source for reportg ad/or modelg ca be beefcal. Aggregato meas the groupg ad cosoldato of the emssos from ay umber of dvdual compoets or sources to a sgle source. Hstorcally, aalyses assocated wth the AB2588 (Ar Toxc Hot Spots Assessmet Act) program utlzed such a method. Purpose The purpose of ths polcy s to provde gudace o determg f ad how emsso sources may be aggregated for the purposes of performg health rsk modelg for Dstrct Rsk Maagemet Revews (RMR), Calfora Evrometal Qualty Act (CEQA) projects, Emssos Ivetory (EI), ad AB2588 (Ar Toxc Hot Spots Assessmet Act). Applcablty Ths polcy may apply to a faclty or project wth multple fugtve emsso sources or compoets wth fugtve emssos, ad qualfy uder Secto IV.A below. Ths polcy does ot apply to combusto sources, or emssos sources wth stacks, whch should all be reported ad evaluated separately.

2 Gudace (see Appedx B for examples) A. Geeral Requremets ad Qualfcatos To qualfy to be aggregated, each source of emssos must meet all of the followg requremets: 1. Aggregato of compoets should oly occur f there are fve (5) or more of ay sgle compoet (e.g. ppg valves at a olfeld) or source type (e.g. storage taks). Note, there ca be umerous compoets wth a permt ut, ad there ca be umerous compoets that are permt-exempt. 2. The aggregated compoets must have the same Source Classfcato Code (SCC) ad emssos estmato methodology, as well as smlar release parameters. 3. Each aggregated source shall use the same toxc emsso profle(s) for toxc emssos estmato purposes. Aggregated sources that do ot have the same toxc emsso profles requre approval from the Dstrct before proceedg. 4. The locato of the aggregated source must rema wth the same Secto, ¼ Secto, ¼ of a ¼ Secto, or the area whch the actual sources resde. The locato should be determed accordg to Sectos IV. B ad C below. 5. The locato of the aggregated source caot resde a area ot owed or cotrolled by the faclty. 6. Aggregated fugtve compoets should be modeled as area sources. 7. The heght above groud or elevato of the area source wll deped o the sources that have bee aggregated. B. Aggregato of Compoets or Sources wth a Uform Spatal Dstrbuto 1. Compoets that are wth a sgle secto (~1609 x ~1609 meters or 1x1 mle square) ca be aggregated to a sgle source, f: a. The compoets are ot separated by more tha 800 meters ad are equally spread over the etre secto, ad b. The aggregated source locato would be the ceter of the secto. The modeled area source sze should be o greater tha 100 meters by 100 meters. 2. Compoets that are wth a sgle quarter secto (~804 x ~804 meters or ½ x ½ mle) ca be aggregated to a sgle aggregated source, f: APR

3 a. The compoets are ot separated by more tha 400 meters ad are equally spread over the etre quarter secto, ad b. The aggregated source locato would be the ceter of the ¼ secto. The modeled area source sze should be o greater tha 50 meters by 50 meters. 3. Compoets that are wth a sgle quarter of a quarter secto (~402 x ~402 meters or 1/4 x 1/4 mle) ca be aggregated to a sgle aggregated source, f: a. The compoets are ot separated by more tha 200 meters ad are equally spread over the etre quarter of a ¼ secto, ad b. The aggregated source locato would be the ceter of the quarter of the quarter secto. The modeled area source sze should be o greater tha 25 meters by 25 meters. Other aggregato schemes ad szes may be used wth the approval of the Dstrct. C. Aggregato of Compoets or Sources wth a No-Uform Spatal Dstrbuto Compoets that are ot equally dstrbuted over a secto, quarter secto, or sub quarter secto ca stll be aggregated as log as the requremets of sub tem IV.A have bee satsfed. Two methods are descrbed below wth the Weghted Mea Ceter Method cosdered more accurate tha the Coservatve Method. Other methods may be used wth the approval of the Dstrct. 1. Weghted Mea Ceter Method The weghted mea ceter method provdes a procedure by whch geospatal data ca be represeted by a sgle data pot or locato. Ths method takes to accout the locato of each source beg aggregated ad the emssos beg released. I order to use ths techque, three data pots from each source beg aggregated are requred: 1) the toxcty based emsso rate (TBER), 2) UTM North coordate, ad 3) UTM East coordate. A example calculato s cluded Appedx A. a. Toxcty Based Emsso Rate I the early 1990 s, whe the Ar Toxc Hot Spots Act (AB2588) program started to requre HRAs, o system exsted for calculatg a source s exposure to earby receptors. At that tme modelers used what has come to be kow as a toxcty based emsso rate. There are two methods for determg the toxc emsso rates; oe for whe APR

4 carcogec (cacer) mpacts are the most sgfcat ad oe for whe o-carcogec (chroc ad acute) mpacts are the most sgfcat. The carcogec method takes the Ut Rsk Factor (URF) for each toxc ar cotamat (TAC) ad multples t by ts calculated aual emssos lbs/year or g/sec. The the carcogec TBERs for each source are summed. Ths method provdes a sgle emssos rate that represets the overall toxcty of the emssos from a gve source. Ths method s also useful for comparg sources rrespectve of ther dsperso parameters.. To determe the carcogec toxcty based emsso rate of each source, use the followg equato: Eq. 1 Toxcty Based Emsso Factor (Carcogec) w = P T =1 Where: w = Sum of the toxcty based emsso rates P = Source pollutat emssos T = Pollutat toxcty (URF) = Number of pollutats for the source = Represets each pollutat The o-carcogec method takes the calculated max hour (acute) or aual emssos (chroc) for each TAC lbs/hour or lbs/year or g/sec ad dvdes t by ts Relatve Exposure Level (REL) value. The the ocarcogec TBERs for each source are summed. Ths method provdes a sgle emssos rate that represets the overall toxcty of the emssos from a gve source. Ths method s also useful for comparg sources rrespectve of ther dsperso parameters.. To determe the carcogec toxcty based emsso rate of each source, use the followg equato: Eq. 2 Toxcty Based Emsso Factor (No-Carcogec) w = P R =1 Where: w = Sum of the toxcty based emsso rates P = Source pollutat emssos R = Pollutat toxcty (REL) = Number of pollutats for the source = Represets each pollutat APR

5 For the purpose of determg where a aggregated source wll be located ad to mmze the resources eeded, the emssos do ot have to be coverted to grams per secod, but ca be left the uts that wll be reported to the Dstrct. b. To determe the weghted mea ceter locato of the aggregated source, use the followg equatos: Eq. 3. Weghted UTM East coordate Where: X w 1 1 w x Xw = Weghted mea UTM East coordate x = UTM East coordate w = Sum of the toxcty based emsso rates = Number of emssos sources to be aggregated = Represets each source coordate w Eq. 4. Weghted UTM North coordate Where: Y w 1 1 w y Yw = Weghted mea UTM North coordate y = UTM North coordate w = Sum of the toxcty based emsso rates = Number of emssos sources to be aggregated = Represets each source coordate w c. I order to mmze the umber of sources ad resources eeded to perform ths method, sources clustered wth 25 meters of each other may be grouped together ad the ceter locato of the cluster maybe used. 2. Coservatve Method Ths method places the locato of the aggregated source at the locato of the earest source receptor combato. APR

6 Appedx A Weghted Mea Ceter Method The example project has sx tak sources. The coordates for each source are dcated below: Table 1. Source Coordates Source UTM East UTM North Tak Tak Tak Tak Tak Tak Step 1: Calculate the toxcty based emsso rate usg equato 1: Table 2. Example of Toxcty Based Emsso Rates Devce Name CAS Pollutat URF Emsso Rate (lbs/yr) Toxcty Based Emsso Rate Tak H2S 1.79E E+00 Tak Xylees 8.75E E+00 Tak Toluee 4.25E E+00 Tak Bezee 2.90E E E-06 Tak H2S 5.37E E+00 Tak Xylees 2.63E E+00 Tak Toluee 1.28E E+00 Tak Bezee 2.90E E E-06 Tak H2S 2.69E E+00 Tak Xylees 1.31E E+00 Tak Toluee 6.38E E+00 Tak Bezee 2.90E E E-06 Tak H2S 1.07E E+00 Tak Xylees 5.25E E+00 Tak Toluee 2.55E E+00 Tak Bezee 2.90E E E-06 Tak H2S 5.37E E+00 Tak Xylees 2.63E E+00 Tak Toluee 1.28E E+00 Tak Bezee 2.90E E E-06 Tak H2S 1.79E E+00 Tak Xylees 8.75E E+00 Tak Toluee 4.25E E+00 Tak Bezee 2.90E E E-06 APR

7 Step 2: Determe the Weghted Mea Ceter (WMC) UTM Coordates for the Aggregated Source Usg Equato 2: X w = [(1.27E 6) ]+[(8.81E 9) ]+[(1.91E 6) ]+[(7.62E 6) ]+[(3.81E 6) ]+[(1.27E 6) ) (1.27E 6)+(3.81E 6)+(1.91E 6)+(7.62E 6)+(3.81E 6)+(1.27E 6) X w = Usg Equato 3: Y w = [(1.27E 6) ]+[(8.81E 9) ]+[(1.91E 6) ]+[(7.62E 6) ]+[(3.81E 6) ]+[(1.27E 6) ) (1.27E 6)+(3.81E 6)+(1.91E 6)+(7.62E 6)+(3.81E 6)+(1.27E 6) Y w = Fgure 1 dsplays the approxmate locato of the sx fugtve tak sources (T1-T6), ad the weghted mea ceter (WMC) for the aggregated source. Fgure 1. Weghted Mea Ceter (WMC) Source Locato APR

8 Appedx B Examples of Aggregated Source Placemet Example 1: Emssos that are evely dstrbuted across a Secto, ¼ Secto, or ¼ of a ¼ Secto. If the emssos from your sources are evely dstrbuted across the Secto, ¼ Secto, or ¼ of a ¼ Secto, your aggregated source should be placed ear the ceter of the Secto, ¼ Secto, or ¼ of a ¼ Secto, respectvely. Ths s llustrated Fgure 2 below: Fgure 2. Locato of a Aggregated Source for Evely Dstrbuted Sources APR

9 Example 2: Emssos that are ot evely dstrbuted across a Secto, ¼ Secto, or ¼ of a ¼ Secto. If the emssos from your sources are ot evely dstrbuted across a Secto, ¼ Secto, or ¼ of a ¼ Secto, your aggregated source should be placed based o the recommeded weght mea ceter method descrbed Secto IV.C.1 above. Assumg that the sources Fgure 3 are detcal ad wth detcal emssos, your aggregated source would be placed smlarly to what s show below: Fgure 3. Locato of a Aggregated Source for No-Uformly Dstrbuted Sources APR

10 Example 3: Multple clusters of the same source type wth a Secto, ¼ Secto, or ¼ of a ¼ Secto. I Fgure 4, there are two dstct clusters of sources wth the same Secto, ¼ Secto, or ¼ of a ¼ Secto. The two clusters have sources that are detcal ad have detcal emssos, but fall outsde the dstace lmtato(s) lsted Secto IV. I ths case each of the two clusters would ot be combed to a sgle aggregated source, but would be separated to two dstct aggregated sources. Ths would esure that emssos are ot advertetly located mproperly. For ths scearo, the aggregated sources would be placed smlarly to what s show below usg the weghted mea ceter method. Fgure 4. Multple Clusters of Sources APR