Jacqueline L. Oravitz, PE
Joseph P. LeClaire, PhD
Ali T. Diba, PE

GIS-Based Pipeline Alternative Alignment Analysis Using PIPEplan

A water utility conducted an analysis of seven alternative alignments for a new aqueduct connection using PIPEplan (DCSE, 1997). PIPEplan is an interactive tool which quantifies environmental impact assessments in corridor planning for conveyance alignments. PIPEplan runs with the ArcView geographic information system (GIS) and Oracle relational database management system (RDBMS) and can be used by planners, managers, and engineers to conduct siting analysis.

PIPEplan was used to screen and rank the alternative alignments based on impacts to resources that fall within three categories: natural resources, land use, and agricultural resources. PIPEplan uses GIS and RDBMS, as well as internal algorithms to summarize resource impacts for each alternative alignment. Ratings of resources within a given category and weights between resource categories were considered in the analysis. The alignments were ranked based on the available data and on the analysis summarized in this report.

Project Background

The water utility is evaluating two major alternatives: (1) a 34-mile pipeline from and existing pipeline access point paralleling a railroad right of way and traversing mainly rural and agricultural areas; and (2) a 15 to 23-mile pipeline from the terminus the existing pipeline traversing a more remote area with more undisturbed natural resources

Methodology

The process of analyzing pipeline data is divided into a number of steps which are described in this section. The following terminology and associated analytical steps are described herein: segments and alignments; resources; resource rates and weights; impacts and buffer distances; generating impacts; calculating score for a given segment; segment ratings; and rating score for alignments.

Segments and Alignments

Each proposed alignment is comprised of several segments. The segments were analyzed separately, and the overall ratings for each alignment was obtained by summing the ratings of it's component alignments. The segments are shown on Figure 1. The composition of the various proposed alignments is as follows:

Figure 1 - Segments

	Alignment	Length	Length
		(ft)	(miles)
1A	179,500	33.9	1-1, 1-2b, 1-3, 1-5, 1-6, 1-7b, 1-8, 1-9a
2A	87,300	16.5	2-1, 2-2, 2.3a, 2-4, 2-5, 2-6, 2-7, 2-8a
2B	89,500	17.0	2-1, 2-9a, 2-9b, 2-10, 2-12, 2-17a, 2-19a, 2-20
2C	95,700	18.1	2-21a, 2-21b, 2-22b, 2-23
2D	120,000	22.7	1-10, 1-6, 1-7b, 1-8, 1-9a
2AB	81,000	15.4	2-1, 2-2, 2-3b, 2-10, 2-11, 2-12, 2-17a, 2-19a, 2-20
2BC	84,000	15.9	2-1, 2-9a, 2-21b, 2-22b, 2-23, 2-25

Resources and Resource Ratings

A resource is an entity with an intrinsic societal value in the vicinity of a proposed alignment that can be impacted by the alignment. Resources can include natural resources such as wetlands and wildlife habitat or man-made resources such as cities, farmlands, and urban areas. Rates were assigned to each resource, specifying a "penalty" for impacting a resource. The higher the rate, the more significant the penalty. Table 1 shows the individual resources (indicated by "ID" and "Description") and the rates assigned for this analysis. The "Category" and "Resource" columns in the table, in general, represent categories and resources used in the pre-engineering alignment studies. The categies were mapped to the PIPEplan resources derived from ArcInfo coverages.

Table 1 -- Resource Ratings
Pre-Eng Refinement Study		PIPEplan Resource-Ratings Table
Category	Resource	ID	Description	Rate
Natural Resources
	Wetlands	51	Wetland Lines: Seasonal Wetland	5
		54	Wetland Areas: Seasonal Wetland	5
		4	Stream-Intermittent	5
		10	Pond-Intermittent	5
		11	Marsh	5
		53	Wetland Areas: Marsh	5
	Waters	3	Stream-Permanent	3
		9	Lake/Pond-Permanent	3
	Riparian	30	Landuse: Riparian Vegetation - SAC	3
		40	Landuse: Riparian Vegetation - SJQ	3
		52	Wetland Lines: Riparian Woodland	3
		56	Wetland Areas: Riparian Woodland	3
	Native Vegetation	31	Landuse: Native Vegetation - SAC	2
		41	Landuse: Native Vegetation - SJQ	2
Land Use
	Annual crop	27	Landuse: Field Crops - SAC	3
		28	Landuse: Truck Nursery and Berry Crops - SAC	3
		37	Landuse: Field Crops - SJQ	3
		38	Landuse: Truck Nursery and Berry Crops - SJQ	3
	Vineyard	34	Landuse: Vineyards - SAC	5
		44	Landuse: Vineyards - SJQ	5
	Orchard	25	Landuse: Citrus and Subtropical - SAC	4
		26	Landuse: Deciduous Fruits and Nuts - SAC	4
		35	Landuse: Citrus and Subtropical - SJQ	4
		36	Landuse: Deciduous Fruits and Nuts - SJQ	4
	Pastures	39	Landuse: Grain and Hay Crops - SJQ	2
		42	Landuse: Pasture - SJQ	2
		29	Landuse: Grain and Hay Crops - SAC	2
		32	Landuse: Pasture - SAC	2
	Residences	57	General Plan Landuse: AG-RES - SAC	5
		58	General Plan Landuse: COMM/OFF - SAC	5
		71	Zone: Limited Agricultural/5ac - SJQ	5
		72	Zone: Incorporated Cities - SJQ	5
		73	Zone: Non-Agricultural - SJQ	5
		69	Zone: Agricultural/Urban Reserve - SJQ	5
		70	Zone: Limited Agricultural/10ac - SJQ	5
	Ag Structures	33	Landuse: Semiagricultural & Incidental to Agriculture - SAC	5
		43	Landuse: Semiagricultural & Incidental to Agriculture - SJQ	5
Agricultural Resources
	Prime	22	Prime Farm Land - SAC	4
		48	Prime Farm Land - SJQ	4
	Local	47	Farm Land of Local Importance - SJQ	3
		21	Farm Land of Local Importance - SAC	3
	State	49	Farm Land of Statewide Importance - SJQ	3
		23	Farm Land of Statewide Importance - SAC	3
	Unique	50	Unique Farm Land - SJQ	3
		24	Unique Farm Land - SAC	3

Impacts and Buffer Distances

An impact occurs wherever the alignment centerline comes within a buffer distance from a resource. Each impact has a starting and ending point within a given segment. The starting point is the point along the segment, indicated by the stationing along the segment, where the segment comes within the buffer distance. The impact occurs along the alignment until it is no longer within the buffer distance. If the segment begins or ends within the buffer distance from a resource, the impact will start at the beginning or end of the segment. Using a larger buffer distance will increase the length of the impact for any given resource. A buffer distance of 20 meter was used in this analysis to calculate the impact scores.

Generating Impacts

Impacts for each segment on each resource were derived using ArcInfo's dynamic segmentation (dynseg) data model. The dynseg events were generated for various buffer distances. The generated events were then transfered and normalized in the PIPEplan RDBMS for retrieval, overlay, rating, and display using the PIPEplan tool.

Calculating score for a given segment

PIPEplan was used to estimate the impacts of a segment to a selected set of resources. This resulted in a rating or score for each segment. When multiple resource impacts were assessed, their impacts were overlayed. Based on the buffer distance, an impact zone for each resource occurrence is established. Then, for the impact and rating calculations, the segment is subdivided by the boundaries of the impact zones. The rate for each sub-segment is the sum of the products of the rate times the weighting factor times the sub-segment length for each resource impacting that sub-segment. The overall rating for a segment is calculated form the sum of the rating for the sub-segments, and the overall rating for each alignment is the sum of the ratings of the segments comprising the alignment.

Results

Segment ratings were derived using a 20 meter buffer distance. The total impact score for each segment and resource category are shown in Table 2. The impacts for each resource category and for all of the resources in the categories combined. The impact score for each category and for the overall combination are illustrated on Figures 2, 3, 4, and 5. These impacts show the ratings as it changes in each subpart of each segment.

Table 2 - Segment Ratings
Segment	Natural Resources	Land Use	Agricultural Resources	Overall
1-1	9,298	4,608	9,981	23,887
1-2a	1,221	17,540	13,360	32,121
1-2b	6,501	34,664	16,033	57,199
1-3	6,512	4,513	4,261	15,286
1-5	32,240	55,946	30,544	118,730
1-6	9,977	37,349	43,709	91,035
1-7a	1,384	1,640	828	3,852
1-7b	802	8,785	6,026	15,612
1-8	1,098	58,520	38,029	97,647
1-9a	599	6,018	7,512	14,129
1-9b	1,947	9,792	3,997	15,736
1-10	8,199	18,342	18,481	45,022
2-1	7,210	17,422	4,841	29,474
2-2	6,912	4,617	11,003	22,532
2-3a	6,382	636	3,168	10,186
2-3b	6,264	515	3,401	10,180
2-4	10,505	11,686	11,291	33,482
2-5	1,059	0	0	1,059
2-6	1,493	184	316	1,992
2-7	9,360	12,842	18,793	40,995
2-8a	4,102	4,254	1,494	9,849
2-8b	5,230	9,721	6,437	21,388
2-9a	14,628	5,466	5,684	25,778
2-9b	18,365	3,228	7,119	28,712
2-10	2,439	1,572	433	4,443
2-11	5,568	1,762	1,184	8,514
2-12	2,310	3,876	2,343	8,528
2-13	962	2,360	780	4,102
2-14	687	1,421	1,495	3,603
2-15	321	2,052	972	3,344
2-16	7,234	1,974	1,066	10,274
2-17a	3,666	6,268	6,867	16,800
2-17b	2,785	2,290	2,647	7,722
2-18	2,033	9,075	7,291	18,399
2-19a	2,836	383	1,421	4,640
2-19b	4,025	289	1,311	5,625
2-20	8,867	2,629	3,976	15,473
2-21a	37,669	19,687	30,011	87,367
2-21b	7,381	358	0	7,739
2-22a	4,016	1,492	1,572	7,080
2-22b	3,586	987	1,637	6,210
2-23	16,878	0	1,688	18,566
2-24	15,956	443	4,322	20,721
2-25	6,810	0	0	6,810

Figure 2 - Natural Resources Impact Ratings

Figure3 - Land Use Impact Ratings

Figure 4 - Agricultural Resources Impact Ratings

Figure 5 - Overall Impact Ratings

The score for the individual alignments were obtained by adding the scores for the segments composing these alignments. The final summary of the rating score combined into the seven alignments is provided in Table 3. Based on the available data and on the analysis summarized in this report, Alignment 2BC is the alignment that would have the least impact to the resources examined.

Table 5 - Alignment Ratings
Alignment	Natural Resources	Land Use	Agricultural Resources	Overall	Normalized
1	67,028	210,403	156,095	433,526	458%
2A	47,022	51,642	50,905	149,569	158%
2B	60,321	40,843	32,684	133,848	142%
2C	65,514	21,032	33,336	119,882	127%
2D	20,675	129,014	113,756	263,445	279%
2AB	46,071	39,044	35,468	120,582	127%
2BC	56,494	24,233	13,851	94,578	100%

References

Diba Consulting Software Engineers. 1997. PIPEplan User's Guide. Mission Viejo, California

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ERSI, ArcInfo, and ArcView are registered trademarks of Environmental System Research Institute, Inc.

About the Authors

Jacqueline L. Oravitz, P.E.
Senior Software Engineer
Diba Consulting Software Engineers
26980 Crown Valley Parkway
Mission Viejo, CA 92691
Telephone: (714)347-7587
Fax: (714)347-7565
email: jlo@dcse.com
http://www.dcse.com

Joseph P. LeClaire, Ph.D.
Supervising Environmental Scientist
Diba Consulting Software Engineers
26980 Crown Valley Parkway
Mission Viejo, CA 92691
Telephone: (714)347-7584
Fax: (714)347-7565
email: jpl@dcse.com
http://www.dcse.com

Ali T. Diba, PE
President
Diba Consulting Software Engineers
26980 Crown Valley Parkway
Mission Viejo, CA 92691
Telephone: (714)347-7575
Fax: (714)347-7565
email: atd@dcse.com
http://www.dcse.com