CECW-PM 21 February 2002

Transmittal Memo

Bolinas Lagoon Ecosystem Restoration Feasibility Study

Alternative Formulation Briefing Guidance Memorandum

Table of Contents of Issues/Comments

Incremental Cost Analysis
Seadrift Lagoon Component

Historical and Projected Volumes and Habitats

Disposal Costs at Hamilton Airfield Wetland Restoration Site
Relationship between Hamilton Airfield restoration and the Bolinas Lagoon Restoration Projects

Least Cost Disposal Site

Operation and Maintenance (O&M) dredging

One Time Dredging Effort
50-Year Habitat Projection

1. Policy Review Concerns.

Comment: a. Project Benefits. The district has used intertidal volume (of water column), measured in cubic yards, as the parameter by which to measure the environmental outputs (benefits) of the project. While this may be a convenient parameter to use to conduct cost effectiveness and incremental cost analyses, it does not immediately translate into any sense of increased habitat for any given species population, or guild of species, of those animals that are important in the Bolinas Lagoon ecosystem. There is no sense of increased quality of habitat that comes with just increasing the amount of intertidal volume of water. Consequently, reviewers of the report will not have a sense of the real benefits to the ecosystem that is being provided by the various alternatives, with and without the proposed action. The district should provide a concomitant assessment of the habitat gains expected with the increase in intertidal volume for each of the alternatives considered and the species of animals that will be benefited and how much they will be benefited. The “habitat unit (HU),” as derived from the Habitat Evaluation Procedures instituted by the U.S. Fish and Wildlife Service, or other similar science-based habitat evaluation metric, should be the index of expression for such habitat gains and be provided for a sufficient number of species populations to show the breadth and extent of habitat improvements at Bolinas Lagoon. Guidance on measurements of environmental benefits can be found in ER 1105-2-100, paragraph C-3d(5). Statements in the AFB materials such as…”the Habitat Evaluation Expert Panel…were unable to justify ranking any of the alternatives above any of the others using the ecological criteria” do not provide sufficient assurances that the expenditure of approximately $54 million dollars of public monies is justified.

District Response: The feasibility study evaluated an array of alternatives that would increase the tidal prism, enlarge the volume of water in the lagoon, and retard the successional processes that have been converting the lagoon to dry land. While the action alternatives would certainly achieve the physical outputs of improved water quality and sediment flux, these structural components are not, per se, ecological benefits. Since the restoration alternatives will bring the lagoon bathymetry back to a historical condition (around the 1950’s), we expect to see an increase in the species that are dependent on lower intertidal and subtidal habitat, which have decreased in number as the lagoon has become shallower. Using available historical data, the District will assess resource losses and losses in tidal volume, tying in the goals of the restoration effort to the restoration benefits that are expected to occur with increases in tidal volume and acreages. This data, along with information on the historic utilization of the lagoon complex by fish and wildlife resources, will be used to evaluate the positive correlation between intertidal volumes and habitat output benefits.

Along with the physical changes of the lagoon, stakeholders have observed a decline in the numbers of migratory waterfowl using the lagoon. Wild populations vary in size over time and space making it difficult to quantify trends in abundance with census data from any one location. However, coastal lagoons like Bolinas provide very significant feeding and resting habitat for birds that use shallow water habitat, and the conversion of shallow water habitat to mudflat or upland could have a significant adverse impact on waterfowl. As seen in the table below, there has been a 53% reduction in shallow water habitat suitable for diving waterfowl between 1968 and 1998. Project alternatives have the potential to make a substantial increase in this type of habitat.

To illustrate the benefit to the diving waterfowl guild of birds, a brief habitat evaluation has been prepared. This habitat metric is derived from: Habitat Suitability Index Models: Lesser Scaup (Wintering) U.S. DOI FWS Biological Report 82(10.91) April 1985. This model was selected because the numbers of scaup observed at Bolinas Lagoon has decreased in recent time, and because the variables in the model can be used to assess estuarine habitat. The model contains four variables: percent area with clams, percent area with emergent vegetation, human disturbance of feeding, and mean water depth. For the scaup, the minimal emergent vegetation and low human disturbance are optimal. The lagoon currently has roughly 50 acres of habitat that would be optimal feeding depth (1- 3m) and would be populated with clams.

The NER [North, Central (Riparian) and South (No Seadrift)] would increase optimal feeding habitat to a total of 186 acres, a three to four fold increase.

Surface Area and Volume Between Depth of 1m to 3m below MSL (-2.70' and 8.70' NGVD)
	Surface Area	Volume
Summary	Acres	Yds3
1968	95.64	379,986
1998	51.65	292,876
North, Central (Estuarine), and South (Seadrift)	214.36	612,675
North, Central (Riparian), and South (Seadrift)	214.36	612,707
North, Central (Estuarine), and South (No Seadrift)	185.77	530,926
North, Central (Riparian), and South (No Seadrift)	185.77	530,958
North and South (Seadrift)	202.31	575,252

Indeed, there is a link between the hydrology and the ecology of Bolinas Lagoon; that is, there are ecological benefits associated with the increase of tidal prism. This relationship is explained generally on page four, paragraph two of the AFB information package as follows:

“A decrease in tidal prism results in a loss of subtidal and intertidal habitats, equating to significant changes in habitat conditions for the species that are dependent on those areas. A decline in subtidal habitat, for example, would result in the loss of estuarine plants (e.g., eelgrass), invertebrates and fish species in the lagoon (MCOSD 1996). Steelhead and Coho salmon are two federally listed Threatened species that would be detrimentally affected by a loss of subtidal habitat (and access to the watershed’s tributaries). Bird diversity would also be affected. Bird surveys indicate that since 1972, diving birds (e.g., grebes and diving ducks) have decreased, giving rise to birds dependent on the intertidal zone, such as shorebirds and dabbling ducks. This trend is counter to statewide and regional trends. These trends will only continue as long as sediment continues to fill the lagoon. The next transitional phase to occur would be that of intertidal habitat to upland habitat. According to the Bolinas Lagoon Management Plan Update (1996), “By 2008, the Lagoon will likely be a significantly less valuable migration and over-wintering location on the Pacific Flyway, where estuarine habitats have already suffered huge losses and degradation.” Other species, like the harbor seals that use Bolinas Lagoon during their pupping season, would also suffer losses in habitat quality and quantity. Given the diversity of wildlife species using the lagoon and its proximity to relatively undisturbed and protected areas, Bolinas Lagoon is a critical element of a unique ecosystem. Although Bolinas Lagoon currently provides important habitat to a variety of species, the value of its habitats will continue to degrade as intertidal and subtidal habitats continue to decline.”

The justification for using tidal prism (i.e. intertidal volume) as an indicator of benefits is explained on page 15 of the same document. To further explain the link between the hydrology and the ecology, however, the following topics will be addressed in the Draft Feasibility Report:

Evaluation of the Alternatives – An Evolution of Possible Parameters

• HEP Analysis

The US Fish and Wildlife Service determined that HEP was not an appropriate analysis to use for Bolinas Lagoon. HEP can be used for terrestrial systems and has been adapted for use in wetland areas, but as of yet, there have not been any HEP models developed for an estuarine lagoon system. Habitat Units are easy to work with and understand, but unfortunately, a full HEP analysis was not appropriate in this case.

• Numbers of Species

Numbers of species were also not used as an indicator of project success because of our inability to predict changes in the system after a given stimulus, as well as our inability to decipher (due to a lack of historical ecological data and natural fluctuations in wildlife populations) short term and long-term changes in the lagoon. That is, we would not be able to come up with an accurate number of population increase for any particular species because of larger, regional trends in those species or other factors unrelated to Bolinas Lagoon. In addition, because this kind of project has not been conducted before, it would be impractical to predict the exact outcome for any particular species. Using numbers of species as an indicator of project success would yield results with a high degree of uncertainty.

• The Habitat Evaluation Expert Panel

Because of the complexity of Bolinas Lagoon and the link between the hydrology and the biology, the Bolinas Lagoon Executive Committee decided to convene a panel of experts – hydrologists and biologists familiar with the lagoon – to evaluate the alternatives. Modeled after the expert panel used in the Everglades project, and supported by the South Pacific Division office, the Habitat Evaluation Expert Panel (HEEP) would improve the plan formulation process and evaluate the acceptability and effectiveness of the alternatives. As stated in the HEEP summary report:

“Considering the complexity of the Bolinas Lagoon environment, as well as the interested and concerned participation of local residents, organizations and agencies, the Bolinas Lagoon Team (including the Corps and the local sponsor) deemed it prudent to seek the advice of an expert panel to evaluate each of the proposed project alternatives based on habitat considerations. By seeking the advice and consensus of a panel of experts, we hoped to discern the most effective, efficient and acceptable alternative for accomplishing the objectives of the project. As stated in the Project Study Plan, the Restoration Goals and Outputs for the Bolinas Lagoon Restoration Project are as follows:

‘The goal of the environmental restoration work performed at Bolinas Lagoon is to restore intertidal and subtidal habitat and stop further loss of these habitats through restoring tidal prism and improving circulation within the basin, while maintaining key mudflats, marsh vegetation, and other areas of biological importance. Although over the long term, sediment deposition will continue to fill the lagoon. This restoration project is intended to significantly slow the present rate of intertidal and subtidal habitat loss.’

Through many hours of examination and discussion, the Habitat Evaluation Expert Panel has added integrity and durability to the plan formulation process and the analysis of the proposed restoration alternatives.”

The HEEP succeeded in modifying the restoration options in order to make them more effective, expressed their concerns for particular species or groups of species, and determined the hydrological and ecological benefits of the project. Their analysis further promoted the project goals as stated in the PSP.

? Red, Yellow, Green – Ranking the Restoration Components

Like in the Everglades project, the HEEP was originally charged with evaluating the alternatives using a Red-Yellow-Green evaluation system. Red = no, or yes only with significant changes; Yellow = concerns exist, but some modification might appease those concerns; Green = yes. The panel, however, decided that all of the restoration options were different shades of Green; none were Yellow or Red. Because of the significant link between the hydrology and the ecology, the panel decided that any improvement in the hydrology would bring a concomitant improvement in the ecology. This is especially true because of how the alternatives were designed – to mimic historical conditions in the lagoon. One significant result of this analysis was that the panel determined that all of the restoration options were environmentally acceptable.

? The Link between Hydrology and Ecology

Since the panel was unable to differentiate the alternatives using the Red-Yellow-Green approach, they were then charged with ranking the alternatives based on their ecological benefit to the lagoon. It was apparent, however, after many hours of discussion, that it was impossible to separate the hydrology from the biology. The panel could establish ecological criteria, but they were unable to rank the alternatives against those criteria. As a result, the panel decided to list the ecological and hydrological factors that should be considered when evaluating the components to see if they could determine a common link between the two that could be used for the comparison. Looking at the list of target habitats desired by the panel (ecological factors) and the habitats associated with improving the hydrology of the system (hydrological factors), the two are clearly linked.

Target Habitats (Ecological): Shallow subtidal, subtidal, intertidal, eelgrass, terrestrial, riparian or transition, and tidal nursery habitat

Habitat (Hydraulic): Quantity (or volume) of intertidal and subtidal habitats

The panel also noted what ecological benefits would arise from an increase in intertidal and subtidal habitats. They assumed, for example, that an increase in subtidal habitat would bring about a benefit to fisheries, diving birds, and foraging seals, as well as potential habitat for eelgrass plants. A benefit to fisheries in the lagoon would also increase the value of the surrounding streams to the fish, creating an overall benefit for this group. These benefits are brought on by improved foraging habitat (due to an improved habitat for prey), improved rearing and nursery habitat, greater potential for escape from predators, and a greater diversification of habitats in the lagoon. The intertidal habitat zone is a source of food for many species higher in the food chain. The mudflats and wetland areas, which serve as habitat for plants and invertebrates, serve as feeding areas and nursery habitats for species higher in the food chain. An increase in intertidal habitat is seen as an overall benefit to the system. Thus, since an increase in intertidal habitat brings about an increase in subtidal habitat, we can assume that the lagoon system would see an overall improvement (improvement in hydrology and biology) if intertidal volume were increased.

After the panel determined that not only could they not separate the biology from the hydrology, but that they were unable to rank the alternatives based on the criteria they had developed (after all, any of the restoration options would provide some level of benefit to the lagoon), the Corps decided that intertidal volume would be an appropriate parameter to use to demonstrate an overall benefit to the lagoon system. When this idea was presented to the expert panel, all of the panel members approved.

• Tidal Prism (Intertidal Volume)

The hydrological benefits of using intertidal volume as an indicator of project success is stated in the AFB report on page 15. The hydrological and ecological benefits associated with an increase in intertidal volume have been tied together (above discussion). Their direct link makes intertidal volume an appropriate parameter for evaluating project benefits.

Discussion: It was agreed that the district will undertake a habitat-based evaluation to quantitatively demonstrate the ecological benefits associated with implementation of the recommended plan. The district has indicated that it is prepared to illustrate the benefit to the diving waterfowl guild of birds using the Habitat Suitability Index Models for the Lesser Scaup (Wintering). A preliminary analysis of the HEP model for the Lesser Scaup has been prepared to show benefits to one species in the diving duck guild by increasing lower intertidal and deeper subtidal habitat. The Corps, in cooperation with the US Fish and Wildlife Service, will also construct a With Project/Without Project comparison using cover types as a proxy for habitat types and ecological guilds to demonstrate project benefits in the feasibility report. These analyses will illustrate the benefits of the project in a quantitative manner, and provide backing to the qualitative assessment already provided. The district agreed to make an earnest effort to provide additional habitat-based evaluations for other species or guilds as presented for the lesser scaup in the district response. Finally it was agreed that the volume metric would be acceptable as the basis for in the incremental analysis of alternatives

Action: The district will undertake a habitat-based evaluation to quantitatively demonstrate ecological benefits associated with the NER and LPP plans. An analysis of the HEP model for the Lesser Scaup has been provided to show benefits to one species in the diving duck guild by increasing lower intertidal and deeper subtidal habitat, but the district will make an earnest effort to provide additional habitat-based evaluations for other species or guilds similar to that developed for the lesser scaup. Finally, it was agreed that the volume metric would be acceptable as the basis for in the incremental analysis of alternatives. The district will revise the draft report accordingly to reflect information in the district’s response and results of the habitat based evaluation.

Comment: b. Incremental Cost Analysis (Attachment 4). The costs shown in this attachment do not coincide with the costs for the NER and LPP alternatives shown on pages 24 and 25 of the “main report.” Consequently, the conclusions of the ICA may not be valid. All costs shown in the report and attachments, appendices, etc., should be consistent.

District Response: Based on the ITR Plan Formulation Comments (shown below), the Incremental Cost Analysis (ICA) was redone taking account for additional costs such as the interest during construction (IDC). The total first cost of $66,156,000 is indeed correct; this figure plus the IDC ($12,914,000) results in the $79,070,000 used for the incremental cost analysis. The same can be said for the locally preferred plan.

There is no difference in the conclusions of the ICA whether one uses first costs or the total investment costs.

Discussion: The draft report and draft EIS will be revised to reflect the current incremental cost analysis.

Action: As indicated in the discussion.

Comment b - Part 2: Initial perusal of the ICA also shows that the “North and South Alternative” would provide almost as much “ecosystem benefit” while costing much less (based on the costs and benefits shown in the ICA table) than the LPP. The district should explain why the Federal government should cost share in a plan (the LPP) that costs over $12 million more than the North and South Alternative but only provides ten percent more benefits.

District Response: In accordance with ER 1105-2-100,

“The National Ecosystem Restoration (NER) plan is one that reasonably maximizes ecosystem restoration benefits compared to costs, consistent with the Federal objective, shall be selected. The selected plan must be shown to be cost effective and justified to achieve the desired level of output.”

Indeed, there are diminishing returns in achieving higher outputs. The difference in cost between the North and South (Seadrift) plan and the North, Central (Riparian) and South (Seadrift) is large (approximately $30 million), but so too are the difference in outputs (42 percent higher). This equates to a small incremental cost increase, from $22.58 to $33.72 per unit. The final increment, the North, Central, and South (Seadrift) alternative, does not appear to be reasonably justified since the additional cost of $7 million results in a mere 0.4 percent increase in output.

Therefore, the agreed national environmental restoration (NER) plan is the North, Central (Riparian) and South (Seadrift) plan. With a first cost of $66 million, the local sponsor indicated that this plan may be cost prohibitive with potential real estate issues and political challenges needed to be met to implement the “South (Seadrift)” alternative. They have since identified two potential locally preferred plans (LPPs), the North, Central (Estuarine)and South (No Seadrift) plan, with a first cost of $59 million, and the North, Central (Riparian) and South (No Seadrift) plan with a first cost of $53 million. These LPPs did not appear in the final array of alternatives, but were found to be cost effective during the first iteration of the ICA.

For ecosystem restoration projects, the non-federal sponsor is required to cover 35 percent of the NER project’s implementation costs. Since the locally preferred plan is a smaller-scaled version of the NER plan, the same cost sharing formula should apply.

Discussion: The district noted that the ICA has been revised to show the elimination of an additional plan in the first iteration of the ICA, and a second figure has been added to show the incremental costs and benefits in the final array of alternatives. However, the analysis will need to be revised in accordance with the resolution of comment c. Seadrift Lagoon Component below, that is the Seadrift Lagoon component should be excluded from the NER plan.

Action: The revised report will reflect the current ICA and exclusion of the Seadrift Lagoon component from the NER plan.

Comment: c. Seadrift Lagoon component. It is stated on page 24 of the main report that “due to real estate issues, potential real estate takings, and public opposition” that a consensus was reached by the Corps and the non-Federal sponsor to exclude the Seadrift Lagoon component from the NER plan. If this component is not implementable and is unacceptable to the local sponsor, it should be considered as a planning constraint and be eliminated from all of the alternatives. The study team should not waste their time and funds investigating an option that is not implementable. The District should, however, note the requirements contained in comment i(2), below, regarding real estate issues.

District Response: The Seadrift Lagoon component was not removed from the NER. The meaning of the statement quoted above (from page 24 of the AFB document) was that the Locally Preferred Plan was derived from the NER, after excluding the Seadrift Lagoon component. That is, the NER remained the same, but because of potential difficulties in implementing that component, Marin County identified a plan (an LPP) that would be more likely to be implementable by the local sponsor. That plan was a derivation of the NER; essentially, the NER minus the Seadrift Lagoon component. In addition, a second LPP was identified. The second LPP is identical to the first LPP, except for the Central alternative. One LPP includes the Central (Estuarine) alternative, and the other LPP includes the Central (Riparian) alternative.

Note: To clarify the discussions of the South and South (Modified) alternatives, the names have been changed to more accurately reflect the composition of both alternatives. South is now South (Seadrift); South (Modified) is now South (No Seadrift).

Discussion: The appropriateness of including the Seadrift Lagoon component in the NER plan was discussed. In addition to the non-Federal sponsor concerns noted in the comment related to implementation and acceptability problems, Headquarters staff advised that restoration of Seadrift Lagoon would not be considered appropriate for ecosystem restoration under existing policy. Seadrift Lagoon is a private man-made feature and would be considered “enhancement”. Because the Corps does not participate in “enhancement” projects, federal cost-sharing participation could not be justified for this component; therefore, the Seadrift Lagoon component must be excluded from any tentatively identified NER plan. The Seadrift Lagoon component may be implemented as part of an LPP, however, with 100% of the associated incremental cost provided by the Non-Federal sponsor.

Action: The draft report will be revised to exclude the Seadrift Lagoon component from the tentatively identified NER plan.

Comment d. Attachment 3, “Historical and Projected Volumes and Habitats.”: Attachment 3 does not address the “South (Modified)” component. The South (Modified) plan is not included in a number of other tables as well. The draft feasibility report must have this alternative included in all plan descriptions, tables and figures.

District Response: As seen in response to comment g. Operations and Maintenance (O&M) dredging, all tables of the AFB package have been updated to include discussion of the South Modified [South (No Seadrift)] alternative. Since it is part of the tentatively selected LPP, it will be analyzed fully like any other alternative. Accordingly, discussion of the South (No Seadrift) alternative, and all of the combinations it appears in, will be added to the text of the Feasibility report.

Note: Per a request by the Executive Committee of the Bolinas Lagoon Ecosystem Restoration Study, the Central and Central Modified alternatives have been renamed Central (Estuarine) and Central (Riparian), respectively. The Central (Estuarine) alternative emphasizes the importance of estuarine environment; that is, more upland/riparian habitat is removed. The Central (Riparian) alternative emphasizes the importance of riparian habitat; that is, no riparian habitat is removed (less upland habitat is removed), and therefore less estuarine habitat is created.

Discussion: As discussed in comment c. above the Seadrift Lagoon component will be excluded from any tentatively identified NER plan Concur with District response.

Action: The district will revise the draft feasibility report and draft EIS will include the updated information related to the South (No Seadrift) alternative.

Comment: e. Disposal Costs at Hamilton Airfield Wetland Restoration site. On page 22, (Disposal and Beneficial Reuse Sites) the report states that a major assumption for disposal of material is that certain costs for off-loading, piping, site management, operations and maintenance at the Hamilton site will be Hamilton project costs, and not Bolinas Lagoon project costs. The table in Attachment 4 entitled "Bolinas Lagoon Cost Summary" shows a column marked "Dredging/Disposal costs @ Hamilton". For the North, Central (Modified) and South plan the Hamilton costs are listed as $33 million of a $66 million first cost. It is not clear what part of the Hamilton costs belong to Bolinas Lagoon. The report needs to clearly state the basis for the assumption, and clarify what costs are project costs. Also, see comment j, below, on this issue.

Comment: j. Relationship between the Hamilton Airfield Wetland Restoration and the Bolinas Lagoon Restoration Projects. Because of the effect on Project Cooperation Agreement (PCA) language for the Hamilton Airfield Wetlands Restoration project and calculation of costs and benefits for the Bolinas Lagoon project, a clear understanding of cost allocation and other relationships between these two projects is needed. The district should be prepared to discuss this issue at the AFB or other meeting with HQUSACE prior to release of a draft feasibility report for public review.

District Response e & j: One assumption used for cost comparison of disposal sites is that the Hamilton Wetlands Restoration Project (HWRP) would accept "clean" material removed from Bolinas Lagoon, whether dredged or land-excavated, for beneficial re-use. To be deemed clean, the material must be suitable for use as wetland cover. Another assumption used (and confirmatory testing should verify) is that nearly all of the material to be removed from the Lagoon is not only suitable for aquatic disposal, but also for use as wetland cover. The known exception to this is the material found in Seadrift Lagoon, which is unsuitable as wetland cover. We have assumed that the material in Seadrift Lagoon is suitable for aquatic disposal because of the relatively low levels of copper sulfate previously measured. Thus, the costs shown in the AFB documentation reflect all dredged material (wet material) going to Hamilton, all excavated material (dry material) going to Hamilton (except that of Highway 1 fill removals), and any trees or other vegetation going to Redwood Landfill.

All of the costs listed in the column marked “Dredging/Disposal Costs @ Hamilton” are part of the Bolinas project costs. In the AFB documentation, the dredging and disposal costs were lumped together as one cost. For the sake of clarity, the dredging and disposal costs will be listed in separate columns in the feasibility report.

Discussion: Due to uncertainties surrounding the availability of the Hamilton Wetlands Restoration Project (HWRP) or other alternative sites for dredged material disposal from the Bolinas Lagoon ecosystem restoration project, the San Francisco Deep Ocean Disposal Site (SFDODS) will be used as the disposal site for feasibility evaluations. The costs associated with disposing the dredged material at SFDODS are not expected to significantly impact either the ICA or the NER/LPP determination. As HWRP becomes more defined, and the uncertainties diminish, future ecosystem restoration opportunities might be presented to allow material from the Bolinas Lagoon project to be disposed of at HWRP. It is recognized that if the HWRP or other alternative site is available and were to be used as the disposal site for the Bolinas Lagoon project, any incremental costs above disposing the material at SFDODS would have to be borne by that project.

Action: The district will revise the draft feasibility report to reflect the uncertainty in the availability in the HWRP and use of the SFDODS as the disposal site for dredge material. The draft report should recognized that if the HWRP or other alternative site is available and were to be used as the disposal site for the Bolinas Lagoon project dredged material, any incremental costs above disposing the material at SFDODS would have to be borne by that project.

Comment: f. Least cost disposal site. The district needs to identify the least costly disposal site for the dredged material from Bolinas Lagoon for the alternative plans. This is not presented in the AFB materials. If, for example, the SFDODS were the least cost disposal alternative the incremental costs of transporting the material to the Hamilton Wetland Restoration site would need to be determined. These incremental costs would need to be justified by wetland restoration outputs at the Hamilton site, as was done in the Oakland Harbor Deepening project.

District Response: As far as off-loading costs at the Hamilton site, we have assumed that the cost of the off-loader, piping, site management, and operations and maintenance at the HWRP will be paid for by the Hamilton project. For example, if these costs were not absorbed by the HWRP, aquatic disposal at the SFDODS would be the least-cost disposal alternative for all of Bolinas Lagoon, including Seadrift Lagoon. Adding the cost of the off-loader alone would preclude the use of the HWRP.

When the aforementioned assumptions were used to develop potential costs for the disposal of material removed from Bolinas Lagoon, the HWRP became the least-cost environmentally acceptable disposal alternative for all of the material, except that found in Seadrift Lagoon, which must be disposed of at the aquatic disposal site. It is noted that there may be limitations on the capacity for dredged material at HWRP, which may preclude the disposal of material from Bolinas Lagoon at that site. However, a PAC document will be completed to evaluate expanding the HWRP to include a new project increment, Bel Marin Keys, which is expected to alleviate concerns over capacity.

Discussion: Contingent language regarding any additional costs for use of the HWRP or other alternative disposal site for disposal of dredged material from the Bolinas Lagoon ecosystem restoration project should be reflected in the district’s response on the potential use of the authorized HWRP. Also see discussion for comments e&j above.

Action: Due to the above uncertainties involved with utilizing HWRP as a disposal site, SFDODS will be used as the disposal site for feasibility evaluations. Also see Action for comments e&j above

Comment: g. Operations and Maintenance (O&M) dredging. The main report states that the Bolinas Lagoon Ecosystem Restoration project would be a “one-time effort,” because maintenance dredging is prohibited in the lagoon by the Gulf of the Farallones National Marine Sanctuary. If maintenance dredging is prohibited, no matter how infrequent, then why would a “one-time” dredging effort of over 1.5 million cubic yards of sediment from the lagoon be permitted? The district should provide an assessment of what the lagoon will look like over a longer period than the 50 years used in Attachment 3 to show the historical and projected volumes. While the period of analysis is 50 years for purposes of economic evaluation, the life of the project is assumed to be indefinite for ecosystem restoration. Such an assessment and evaluation should also examine the desirability of spending over $50 million dollars and then letting the lagoon gradually fill in with sediments until it is the same as today’s condition. The Principles and Guidelines and ER 1105-2-100 specifically state that “plans may be formulated which require changes in existing statutes, administrative regulations, and established common law…” The report should examine the frequency needed to conduct maintenance dredging so that the depths obtained during the initial construction are maintained over the life of the project to assure that project benefits are maintained. The requirements of periodic dredging for all alternatives should be examined to identify the proper NER and LPP plans.

District Response:

One Time Dredging Effort

The Bolinas Lagoon Restoration Project is attempting to restore an ecological and geological system that was altered by human mismanagement. Lagoon systems and shallow water estuaries are typically transient settings that normally progress from fully functional tidal systems to meadows. However, in the case of Bolinas Lagoon, this process is periodically interrupted by seismic activity that dramatically increases tidal prism by physically dropping the lagoon bottom elevation and liquefying the sediment (this occurred in the 1906 earthquake). In a study performed for the USGS, it was found that there is considerable evidence that significant earthquakes occur along the San Andreas Fault in this region at a regular interval of three to four hundred years. It is believed that this process has kept Bolinas Lagoon open for far longer than a typical lagoon system, and it is strongly suspected that it would have stayed open even longer if humans had not disrupted the lagoon and its watershed.

Looking at numerous studies pertaining to the lagoon, lagoon maps/bathymetries, and aerial photos, the Corps believes the lagoon has been filling in over the last 100 to 150 years at approximately 3 times its normal rate. This is an average rate since there were most likely times of super elevated sediment input alternating with near normal input rates as a result of varying land management practices. This overload of sediment has sped up the lagoons transformation process to the point where inlet closure could occur as soon as 2050. This would change the system, increasing the rate of meadow formation. Current opinion is that if the lagoon were left on its own, by the time the next earthquake hit the lagoon, it would be too far into the meadow formation processes to be significantly reversed.

Given the situation described above, the County of Marin (local sponsor) and the San Francisco District would ideally like to restore this system to it’s “stable” condition, which is a lagoon that progresses through the “normal” phases of a lagoon, set back periodically by natural processes. Although regular maintenance, such as regularly scheduled dredging every ten years for example, does not correspond with the project goals, there may be an occasion in the future when it is necessary to perform work after the project is physically completed in order to ensure that the benefits of this project are being realized. The Feasibility Report will include a plan to ensure that the project goals, as intended, are reasonably being achieved. For example, “If A occurs, than B & C will need to be done. If K occurs than nothing will need to be done. If M occurs we will have to take N action within XX months.” Because the lagoon is strictly regulated by the Gulf of the Farallones National Marine Sanctuary, all work in the lagoon must be approved through the permit process of the Sanctuary. Future dredging would only be allowed for scientific or ecological purposes, i.e., for the purpose of restoration.

The Corps will cost share the construction phase of the project, as well as the monitoring and adaptive management program for up to five years after the excavation work is completed. Any work after the five-year period, be it monitoring, adaptive management, dredging, etc., will be the responsibility of the local sponsor. Cost-sharing responsibilities of Marin County and the Corps will be described in more detail in the Operation, Maintenance, Repair, Replacement and Rehabilitation (OMRR&R) plan of the feasibility report. Specific cost-sharing responsibilities will be negotiated and later incorporated into the language of the project cost-sharing agreement (PCA) before construction.

50-Year Habitat Projection

The lagoon’s physical condition and habitats were projected 50 years into the future to meet the typical Corps period of analysis for the purpose of benefits/costs analyses, according to Planning Manual (IWR Report 96-R-21) PGL-96-01 and PGN ER-1105-2-100, Appendix D. This was accomplished using the projected infilling rate and the available data from 1968 to 1998. With the annual infilling rate projected, the loss of lagoon volume and potential tidal prism was calculated by subtracting the annual rate from the 1998 value. The projection of potential tidal prism was used to estimate the inlet closure date using the O’Brien Criteria (Table 1). The results of this projection showed the inlet could close in the year 2050, given the right conditions.

Table 1. Without Project Inlet Closure Estimation

*Inlet closure is estimated to occur at a closure index of 15. The closure index is essentially a ratio of tidal

power versus wave power.

Using this same analysis, the inlet closure was calculated for each alternative and projected 50 years into the future (post construction - assumed 2008) by using the new lagoon potential tidal prism as a starting point and subtracting the estimated annual sedimentation rate from it. The inlet closure estimates are provided for the NER plan (North, Central (Riparian), and South), the two runners up, and the two LPPs (North, Central (Estuarine), and South (No Seadrift) and North, Central (Riparian), and South (No Seadrift) (Tables 2 through 6).

Table 2. North, Central (Estuarine), and South (Seadrift) Alternative Inlet Closure Estimation