Guidelines for Evaluating and Selecting Modifications to Existing Roadway Drainage Infrastructure to Improve Water Quality in Ultra-Urban Areas (2012)

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104 Cost evaluation is a vital component in the practicality assessment of retrofit alternatives. This section describes the factors that affect retrofit costs and presents general retrofit cost information and cost reduction strategies. 8.1 Cost Elements Planning, Design, and Permitting Costs: BMP retrofit- ting requires significant upfront time and cost for scoping, siting, site characterization, permitting, and BMP design. Effective planning and design, however, are crucial for suc- cessful retrofitting. Early and comprehensive coordination and site characterization can help to identify efficient retrofit options, as well as site constraints that will avoid added costs and construction delays down the road. Significant planning and design costs should be expected for retrofit projects. For resource planning, Caltrans estimates average design costs as 10% to 12% of the construction cost (Caltrans, 2001). Higher planning and design costs should be anticipated for small proj- ects and for projects in highly constrained settings. Permitting costs can vary substantially based upon the environmental and infrastructure setting. In some cases, very minor permit- ting costs can be anticipated (i.e., a project completely within ROW and no environmental impacts); in other cases, where projects are outside the ROW and/or would impact environ- mentally sensitive species, for example, fairly high costs can be anticipated. Land Costs: Land acquisition costs are site specific but are characteristically high in dense urban areas. Approxi- mate land costs can range from $500,000 to $2,000,000 per acre (Strecker et al., 2005). ROW acquisition in ultra-urban settings is generally not practical due to high land costs and existing development/infrastructure. Capital Costs: Capital costs are the expenditures associ- ated with the construction of the BMP retrofit. BMP con- struction costs are highly variable and critically dependent on site-specific conditions. Cost information from past projects can only serve as a guide to inform estimates of future proj- ects and not as a definitive reference since every retrofit is dif- ferent. Factors that make it difficult to apply unit costs from one project directly to another project include: • Regional variations in design, price of materials, and labor rates; • Physical site-specific constraints; • Differences in quality and efficiency of planners, designers, and contractors; • Differences in regulatory framework; • Differences in inflation and macroeconomic conditions at the time of construction; and • Regional variations in weather conditions. Accurately estimating costs for new construction is chal- lenging for the reasons just listed. It is even more challeng- ing to develop accurate cost estimates for retrofit situations due to the uncertainty of site-specific complications. Retrofit costs, therefore, are typically much higher than new construc- tion costs for most BMPs other than BMPs such as inserts. According to Schueler et al. (2007), the base construction cost of retrofits generally exceeded equivalent new construc- tion costs by a factor of 1.5 to 6 based on evaluation of nearly 100 projects around the country. Still higher construction costs should be expected for ultra-urban retrofits due to physical site constraints. The costing tools that are available typically do not factor in retrofit conditions that can sig- nificantly increase costs, e.g., the whole-life cost model and spreadsheet framework developed by WERF (2005). Contingency and Escalation Costs: Contingency costs address unforeseen costs encountered during construction. Contingency costs for retrofit projects should be higher as compared to new construction, reflecting greater uncertainty about site-specific conditions and constraints and less flexi- bility for corrective measures. Design and contingency factors for BMP retrofits range between 32% to 40% (Brown and S e c t i o n 8 Retrofit Costs

105 Schueler, 2007; Schueler et al., 2007). Contingency factors can also depend on the BMP type. Vegetated BMPs are more likely to stay on budget for capital and installation in compar- ison to infiltration basins, porous pavement, and media filters (Phillips et al., 2008). Projects that have significant construc- tion periods should incorporate appropriate cost escalation factors in the project cost (Caltrans, 2009). Operation and Maintenance Costs: All retrofits have to be maintained after construction. While maintenance might not factor into retrofit installation costs, maintenance is a major component of the life-cycle cost of any retrofit and should be taken into consideration at the planning stages of any retrofit process. The most common and costly O&M practices are sediment management at inlets and outlets, trash and debris removal, and vegetation management (Kang et al., 2008a). O&M costs can compose a substantial fraction of the total BMP cost. Annual O&M costs for surface detention facilities are on the order of 5% or less of the construction cost. Dry detention facilities and infiltration basins have the lowest and least vari- able O&M costs (Weiss et al., 2005). More variable O&M costs as a percentage of construction cost are reported for infiltration trenches (5% to > 20%), sand filters (1% to 13%), swales (4% to > 7%), and bioretention (1% to > 11%). As a rule-of-thumb, annual O&M costs are on the order of 10% of total construc- tion costs for stormwater BMPs that cost about $10,000 (circa 2005), and on the order of 5% for stormwater BMPs that cost $100,000 (circa 2005) (Kang et al., 2008a). Greater O&M costs can be anticipated for proprietary underground BMPs, particu- larly, if they require frequent inspection and maintenance; there are access or safety issues; or they require proprietary compo- nents such media cartridges. However, long-term maintenance cost data for proprietary BMPs are not well established. Life-Cycle Costs: These costs are the total project cost over the life span of the retrofit BMP, including planning and design, construction, and O&M. Examples of life-cycle cost estimation for BMPs are given by Oregon State Univer- sity et al. (2006). 8.2 Cost Factors in Ultra-Urban Settings In ultra-urban retrofit situations, the site conditions can strongly affect retrofit costs. Even when capital costs are known, such as the cost of proprietary BMPs, site conditions can greatly affect the installation costs. Understanding site constraints at the design stage can translate into more accu- rate cost estimates. The site constraints most likely to impact cost estimates are factors that limit constructability such as space constraints, site accessibility, and obstructions. Space Constraints: Limited space can prevent the use of the most efficient tools and machinery and/or can increase the amount of manual labor that has to be done to complete a project. Space limitations can force contractors to reduce the size of the staging areas or relocate the staging area to incon- venient locations, lowering construction efficiency. Cost esti- mates must account for alternative methods of construction in space-constrained situations. Site Accessibility: The distance from construction materials and excess material haul sites can significantly increase retrofit costs. Similarly, limited access to retrofit sites can also signifi- cantly increase project costs. Cost estimates must account for site accessibility. Obstructions: The presence of obstructions both known and unknown can significantly impact construction costs and schedules. Large rocks and boulders, unsuitable and contami- nated soils, high groundwater tables, utility conflicts, exist- ing structure foundations, historic buildings, wetlands, water bodies, and other protected areas can cause costly construc- tion delays and construction change orders. Ultra-urban highways are prone to unforeseen obstruc- tions because of the density of development. In many cases, as-built drawings are not available, particularly in older highway settings, and even when available, they may not be accurate. During the Caltrans retrofit study, the discovery of unsuitable subsurface materials and buried utilities was a reoccurring issue, even when as-builts were available (Cal- trans, 2004). Buried objects and utility conflicts accounted for 4.3% of the total adjusted retrofit construction costs in the Caltrans study (Caltrans, 2001). Ultra-urban retrofits warrant greater efforts in early plan- ning, coordination, and site characterization to help identify potential obstructions. Even with such efforts, unknown obstructions are potential constraints that cannot be com- pletely forecast. Contingency costs should be increased as necessary to reflect uncertainties about the site conditions. Environmental Mitigation and Permitting Challenges: Additional costs relating to mitigation of environmentally sensitive areas, protection of wetlands and endangered spe- cies habitat, and related permitting can significantly increase the total cost of a retrofit. Retrofit selection, design, cost estimates, and construction should anticipate the need for mitigation, protection, and special permits. Safety and Security: Safety and security considerations require additional components such as fences, gates, locks, screens, and security lights to be included in retrofit designs. During construction, additional signage and traffic control may be needed for the safety of the construction workers and the general public. For example, traffic-control and safety/ security costs accounted for about 7.5% of the total adjusted retrofit construction costs in the Caltrans study (Caltrans, 2001). Failure to include safety components in the design or failure to anticipate the cost of construction and inspection/ maintenance safety procedures can lead to inaccurate cost estimates.

106 Longevity: The longevity of a BMP is affected by fac- tors such as maintenance (most importantly); deterioration of materials (as in a filter); damage due to accidents, cold weather, vandalism, etc.; changing drivers such as traffic con- ditions, urban density, etc.; preference for alternative use for site; changes in treatment preference; changes in transporta- tion mode; and so forth. Longevity directly affects estimates of life-cycle costs. At the end of a BMP’s life, engineering options are similar to those for any facility: rebuilding or renovation, abandonment in favor of a new facility or alternative treat- ment, or rejuvenation of components such as filter material. 8.3 BMP Cost Estimates 8.3.1 Sources of Cost Data BMP cost data are limited, particularly for highway retro- fit projects in space-constrained settings. Potential sources of cost data follow: • Reference manuals: RS Means (http://rsmeans.reedcon- structiondata.com/) and similar reference manuals provide current cost-estimating data for a variety of construction categories. Use of cost data from new construction or sig- nificant redevelopment without adjustment, however, is not appropriate for retrofit projects as site-specific condi- tions and constraints are likely to increase costs. • Proprietary device manufacturers: Manufacturers are good sources of capital cost information for proprietary BMPs and expected O&M costs. They may also have infor- mation on construction requirements that can help to refine cost estimates. • Industry literature: BMP cost information is compiled in various reports including Heaney et al. (2002); Sample et al. (2003); Young et al. (1996); and Weiss et al. (2005). Several of these sources are summarized by Oregon State University et al. (2006). The data represent many types of BMPs and appli- cations, but most are for new construction. Available cost data are frequently normalized by area or volume treated, and summarized as power function equations. General cost information is useful for preliminary retrofit planning. • Contractors and DOT in-house databases: The most useful cost information is gained through experience of engineers and construction personnel as DOTs implement retrofit programs. DOTs should actively coordinate and develop working relationships between designers, engi- neers, field personnel, and contractors to gain experience and insights into retrofit cost drivers and to develop cost reduction approaches. Some state DOTs, such as WSDOT, are beginning to perform value-engineering studies on stormwater facilities in urban areas, to discern the most cost-effective solutions. 8.3.2 Retrofit Cost Data Published BMP retrofit cost data are limited. Primary sources of retrofit cost data are the Center for Watershed Pro- tection (CWP) guidance document (Schueler et al., 2007) and the Caltrans retrofit study report (Caltrans, 2004). Table 8.1 summarizes retrofit cost information from these sources. The Center for Watershed Protection (Schueler et al., 2007) compiled cost data from 100 BMP retrofit projects that reflect a variety of retrofit project types. The cost information is for retrofit projects generally aimed at watershed restoration goals where space constraints do not significantly impede design and construction. Therefore, the cost guidance does not entirely reflect costs associated with ultra-urban environ- ments where higher costs are expected. The Caltrans retrofit study (2004) included detailed accounting of capital and maintenance costs with indepen- dent third-party review. The costs reflect stand-alone retrofit projects of transportation drainage facilities in urban set- tings. Caltrans noted that there is uncertainty about how well the cost data may reflect actual costs in a large-scale retrofit program due to the pilot-specific nature of some of the costs and the lack of standard competitive bidding. Nevertheless, the Caltrans cost data are likely the most representative cost data available for ultra-urban highway retrofits, but should be used only as a general guide. 8.3.3 General Findings and Cost Guidance Site-specific and national cost information compiled in the Caltrans (2004) and CWP (Schueler et al., 2007) reports sup- port the following findings and general cost guidance regard- ing BMP retrofits: • Retrofit costs vary greatly: Available retrofit costs are highly variable, even within similar BMP categories and for similar treatment volumes. Variable costs reflect the site-specific characteristics and general uncertainties asso- ciated with retrofit situations. Consequently, it is difficult to develop non-specific forecasts of retrofit costs. • Retrofit costs are significantly greater than new con- struction: Schueler et al. (2007) report that retrofit base construction costs generally exceeded the cost of new stormwater practices by a factor of 1.5 to 6. Caltrans (2004) finds that retrofit construction costs were as much as an order of magnitude or more than costs gathered in a nationwide survey, reflecting the stand-alone and site- specific characteristics of the Caltrans retrofit projects as well as the general nature of more difficult conditions encountered in highway/freeway environments. • The most cost-effective BMPs are surface storage and vegetated BMPs: The most cost-effective BMP categories

107 in terms of cost per volume treated are surface storage and vegetated facilities, including detention and infiltration basins and vegetative filtration BMPs. A few types of catch basin retrofits, GSRDs, and proprietary hydrodynamic sys- tems also have good to moderate cost effectiveness. • The least cost-effective BMPs are underground BMPs: The most costly BMPs are those that require underground instal- lation including underground detention vaults, oil-water separators, and underground media filtration systems. • Unit costs decline as the size of the impervious acreage increases: Caltrans and the CWP both found the size of treated area to be one of the most influential cost factors. There is an economy of scale in terms of construction per unit volume treated as the size of the treated area increases. Schueler et al. (2007) state that smaller on-site retrofits that treat less than a 1/2 acre of impervious cover tend to be two orders of magnitude more expensive per treated area than larger storage retrofit practices. • BMPs with simple and standard designs tend to be more cost effective than specialized and proprietary BMP devices: In general, cost efficiencies are gained when BMPs have simple designs (e.g., surface detention, infiltration and vegetated filtration BMPs) and/or make use of stan- dardized designs and components (i.e., inlet structures and precast units). BMPs with complex and unique designs (e.g., underground cast in-place designs) and proprietary components (e.g., specialized media cartridges) tend to be more costly on a cost per volume treated basis. 8.4 Cost Reduction Strategies Cost reduction approaches and strategies are developed through experience as DOTs develop and implement retro- fit programs. The retrofit pilot study conducted by Caltrans (2004) identified a number of cost reduction strategies as outlined in the following paragraphs. Integrate BMP Retrofits with Larger Projects: For major projects, stand-alone retrofits are the most expensive approach. Integrating retrofits with other highway improvement projects reduces costs by: • Providing more flexibility and opportunity for BMP selec- tion, BMP siting, and connection with existing drainage systems; Retrofit Category Caltrans Center for Watershed Protection BMP Type (number of installations) Adjusted Construction Cost* ($/m3 ) O&M ($/m3) Life- Cycle Cost** ($/m3) BMP Type Construction Cost* ($/m3 ) Range Average Range Median Catch basin Various types (6) $3–$27 $13 $37 $50 Hydrodynamic CDS units (2) $224– $353 $340 $127 $467 Oil-Water Separator Areo-Power (1) $2537 $27 $2,564 Detention Extended detention (5) $390– $1683 $760 $107 $867 Ponds $38–$367 $113 Wet Basin (1) $2229 $582 $2,811 Vegetative filtration Biofiltration Swale (6) $182– $2005 $968 $95 $1,064 Swale $267– $827 $470 Biofiltration Strip (3) $384– $1237 $963 $95 $1,058 Large bioretention $282– $648 $395 Media filtration Storm filter (1) $2024 $263 $2,287 Delaware Sand Filter (1) $2462 $100 $2,563 Structural sand filters $601– $827 $752 Austin Sand Filter (5) $746– $2118 $1863 $100 $1,964 Underground sand filter $1052– $2818 $2442 Infiltration Infiltration Basin (2) $340– $397 $475 $104 $579 Infiltration retrofit $376– $864 $564 Infiltration trench (2) $691– $775 $944 $91 $1,035 French drain/ dry well $395– $507 $451 Advanced treatment MCTT (2) $1856– $1895 $2414 $220 $2,635 * Cost per cubic meter of design storm treated, inflation adjusted to 2009 dollars. Design storms and design treatment volumes vary reflecting differences in regulatory and precipitation characteristics. ** 20 years @ 4% Note: To convert from $/m3 to $/ft3 divide by 35.3; to convert from $/m3 to $/acre-ft multiply by 1233.6. Table 8.1. Retrofit cost information from Caltrans (2004) and Schueler et al. (2007).

108 • Reducing mobilization, traffic-control, and equipment costs, and generally increasing the economies of scale during construction; and • Reducing regulatory compliance cost by using a single per- mit for the entire project. DOT retrofit programs should emphasize long-range plan- ning to coordinate retrofits with other highway improvement projects. Consider Cost Implications of BMP Selection: BMP options have varying cost attributes: • Larger treatment capacity is more cost effective. Because of economies of scale, BMPs that treat larger areas/volumes are generally more cost effective than smaller facilities; for example, regional facilities are more cost effective than dis- tributed facilities, unless there would be significant con- veyance costs to address or larger land areas would need to be purchased to site the larger facility. When options are available, BMPs should be selected and designed to treat larger drainage areas. This guidance may be constrained by maintenance issues. For example, O&M personnel may prefer taking care of a single, large facility rather than sev- eral smaller ones, or depending on the difficulty/frequency, there may be occasions when several small installations of one type might be preferable to a single large site with another type. • Non-structural vegetated controls are less costly than structural controls. Vegetated BMPs have minimal struc- tural features, have flexible designs allowing for easy inte- gration into landscaping, and can provide conveyance functions. This provides savings in the design and con- struction of structural stormwater facilities such as pipes, conveyances, and storage facilities. Land costs if required can make them more expensive. • Specialized proprietary BMPs are generally less cost effec- tive. Specialized proprietary BMPs can have higher capi- tal and maintenance costs than standard alternatives and should be a second-tier alternative. Proprietary specialized BMPs are most suitable where standard alternatives are not practical (highly space-constrained settings) or when they are required to meet higher levels of treatment per- formance (for example, as part of a treatment train or if specialized media is required to address a particular POC). Partner with Other Entities: Cross-jurisdictional partner- ships within the watersheds where the highways are located can provide significant cost savings. Consider Engineering Design and Construction Factors: BMP design and construction are major cost drivers. Sig- nificant cost savings are realized as personnel gain experi- ence with BMP technologies, BMP siting, and BMP design and modifications: • Consider undersized BMPs for cost savings. BMPs are sized to conform with DOT design storm sizing require- ments. However, in space-constrained situations, BMP sizing requirements can be cost prohibitive. Undersized BMPs that are cost effective should be pursued consistent with the overall goal of maximizing pollutant reduction. In some situations, it may make sense to oversize BMPs in areas where one can offset reductions in performance for undersized BMPs. Note that undersized BMPs if designed properly can still achieve significant water quality benefits. • Use landscape features. Integrate BMPs into natural topog- raphy and landscaping to reduce construction and material costs. If this is feasible, distributed BMPs may be more cost effective than a larger facility. • Limit structural requirements. Select BMPs that do not require pumping and extensive shoring as feasible. • Use of standard components. Flexible designs that utilize standard components and construction practices tend to be easier to construct and are more likely to be completed on schedule with a reduced risk of budget overruns. • Limit sod and irrigation for vegetation installation. Mini- mize the use of sod as a primary means of establishing or restoring vegetation, and install vegetation when there is a reasonable chance of successful establishment without irri- gation (Caltrans, 2009) or with minimal irrigation (during establishment period in particular).